Lucio Buratto, Richard Packard
History and evolution of modern Cataract Surgery
Jorge L. Alió, John Alpar, Danièle Aron-Rosa, Steve Arshinoff, Georges Baikoff, Rafael I. Barraquer, Domenico Boccuzzi, Steve Brint, Patrick I. Condon, Jack M. Dodick, Howard Fine, Richard Keeler, Paul Koch, Keiki Mehta, Thomas Neuhann, Bo Philipson, Kimiya Shimizu, Mike Southard, David Spalton, Yuri Takhtaev
Fabiano Gruppo Editoriale
Š Copyright 2019 Lucio Buratto ISBN 978-88-31256-01-8 FABIANO Gruppo Editoriale
Publisher: FGE S.r.l. Fabiano Gruppo Editoriale Field office: Regione Rivelle 7/F - 14050 Moasca AT, Italy Editorial office: Via Petitti 16, 20149 Milano, Italy e-mail: info@fgeditore.it - Tel. +39 0141 1706694 The Authors and the Editor decline any responsability for any errors in the text. All rights reserved. Reproduction of this book - total or partial - is strictly forbidden. Printed in: August 2019
I dedicate this book to my grandson Kaito with the wish and hope that he will become a good doctor and a very good ophthalmologist. Grandad Lucio
I dedicate this book to all those who have enabled me to have my wonderful career in ophthalmology but especially my wife Fiona also an ophthalmologist who has put up with all the time I have spent editing this book. Richard Packard
Index CHAPTER 1
CATARACT EXTRACTION FROM ANCIENT TIMES TO THE 20TH CENTURY.....................................7 Richard Packard
CHAPTER 2
THE HISTORY OF INCISIONS IN CATARACT SURGERY .......................17 Joan Balgos, Jorge L. Alio, Andrzej Grzybowski, Piotr Kanclerz, Howard Fine
CHAPTER 3
THE EVOLUTION OF THE CAPSULOTOMY .............................................39 Richard Packard
CHAPTER 4
THE EVOLUTION OF PHACOEMULSIFICATION ...................................51 Paul Koch
CHAPTER 5
HISTORY AND EVOLUTION OF NUCLEAR EXPRESSION AND CORTEX ASPIRATION..........................................................................75 Lucio Buratto
CHAPTER 6
THE HISTORY OF INTRAOCULAR LENSES ............................................93 Domenico Boccuzzi
CHAPTER 7
THE HISTORY AND EVOLUTION OF OPHTHALMIC VISCOSURGICAL DEVICES (VISCOELASTICS) ........................................157 Steve Arshinoff
CHAPTER 8
POSTERIOR CAPSULE OPACIFICATION ..................................................165 David Spalton
CHAPTER 9
THE HISTORY OF LASERS IN CATARACT REMOVAL .............................175 Jack M. Dodick
CHAPTER 10
THE HISTORY OF THE ND:YAG LASER .....................................................183 Danièle Aron-Rosa, Jean-Claude Grieseman, Jean-Luc Febbraro
CHAPTER 11
IIIC THE FIRST 35 YEARS ..............................................................................187 Bo Philipson
CHAPTER 12
THE EVOLUTION OF THE OPHTHALMIC SURGICAL MICROSCOPE.................................195 Richard Keeler
CHAPTER 13
HISTORY FROM AN OPHTHALMIC SURGICAL COMPANY VIEWPOINT .................................................................................231 Mike Southard
CHAPTER 14
THE IMPACT OF IMPACT .............................................................................253 Lucio Buratto, Mike Southard
CHAPTER 15
LIVE SURGERY IN THE DEVELOPMENT OF ITALIAN AND INTERNATIONAL OPHTHALMIC SURGERY...........265 Lucio Buratto
CHAPTER 16
THE CONTRIBUTIONS OF THE BARRAQUER FAMILY TO XX CENTURY CATARACT SURGERY ....................................................297 Rafael I. Barraquer
CHAPTER 17
MODERN CATARACT SURGERY FROM THE BRITISH PERSPECTIVE ...........................................................307 Richard Packard
CHAPTER 18
THE HISTORY OF ADULT AND CONGENITAL CATARACT SURGERY IN IRELAND .................................313 Patrick I. Condon, Michael O’Keefe
CHAPTER 19
THE DEVELOPMENT OF MODERN CATARACT SURGERY, THE GERMAN EXPERIENCE ........................................................................333 Thomas Neuhann
CHAPTER 20
THE HISTORY OF PHACOEMULSFICATION IN SPAIN .........................343 Jorge L. Alio, Ramon Lorente
CHAPTER 21
A HISTORY OF MODERN CATARACT SURGERY FROM THE FRENCH VIEWPOINT ..............................................................355 Georges Baikoff
CHAPTER 22
THE ITALIAN EXPERIENCE .........................................................................361 Lucio Buratto
CHAPTER 23
CATARACT SURGERY IN THE USA .............................................................399 Stephen Brint
CHAPTER 24
LENS IMPLANTATION IN THE UNITED STATES OF AMERICA A PERSONAL VIEW BY ONE WHO WAS THERE ......................................407 John Alpar
CHAPTER 25
THE HISTORY OF MODERN CATARACT SURGERY IN JAPAN ............427 Kimiya Shimizu
CHAPTER 26
THE HISTORY OF CATARACT SURGERY IN INDIA ................................435 Keiki Mehta
CHAPTER 27
THE HISTORY OF OPHTHALMOLOGY IN RUSSIA ................................445 Yuri Takhtaev
1 Cataract extraction from ancient times to the 20th century Richard Packard
I
n ancient times the operation of couching was performed by the Babylonians according to the Code of Hammurabi in the 1800s BCE and is supposed to have been described by the Indian surgeon Acharya Sushruta in 600BCE in his treatise Uttar Tantra. However Roy et al in a paper in the British Journal of Ophthalmology in 1973 claim that Sushruta (Figure 1) carried out a form of extracapsular surgery. Described in a new translation of his text book thus: “The patient was asked to sit on a high stool, with the surgeon sitting in front of him face to face. He was instructed to look at the surgeon’s nose while the operator placed the tip of his little finger on the bony margin of the outer angle of the orbit, holding a sharp-pointed needle between his thumb, index, and middle finger. The point entered the anterior chamber, at the junction of the medial and lateral two-thirds of the outer portion of the white layer (sclera) of the eyeball. If a sound was produced followed by the gushing of watery fluid, then the surgeon’s needle was considered to be in the correct part of the eyeball, but if this puncture was followed by bleeding, it meant that it was misplaced. Care was taken to avoid blood ves- Figure 1. Description in Sanskrit of Sushruta’s operative technique sels present in that region. The tip for cataract
7
HIST ORY AND EVOLUT ION OF MODERN CATARACT SURGERY
Figure 2. Ammar ibn Ali Al-Mosuli sucking out a soft cataract
of the needle was then made to incise the capsule of the lens. With the needle in this position, the patient was asked to blow down the nostril, while closing the opposite nares. After this procedure, according to Sushruta, lens material came out alongside the needle and when the patient was able to perceive objects, the needle was removed.” Galen of Pergamon in the 2nd century CE recorded that a Greek physician, “dislodged the cataract into another place where it was less disturbing”. This couching technique for treating the mature cataract was performed into the 20th century. How then did things change? Although there is a recent translation of Sushruta’s works, as mentioned above, which suggested he may have extracted a soft cataract by suction it was an Iraqi surgeon Ammar ibn Ali Al-Mosuli who certainly performed thisi. In his Choice of Eye Diseases (1010CE) written in Egypt he described extraction of cataracts using suction. He invented a hollow metallic syringe, which he inserted through the sclera (Figure 2). He wrote the following on his invention: “Then I constructed the hollow needle, but I did not operate with it on anybody at all, before I came to Tiberias. There came a man for an operation who told me: Do as you like with me, only I cannot lie on my back. Then I operated on him with the hollow needle and extracted the cataract; and he saw immediately and did not need to lie, but slept as he liked. Only I bandaged his eye for seven days. With this needle nobody preceded me. I have done many operations with it in Egypt.” It was not until the 17th century that the understanding of the anatomy of the lens in the eye led surgeons to consider the removal by extraction of a mature cataract when the first post-mortem examinations of cataractous lenses were performed. This was done by Werner Rolfink (1599–1673) in 1656, and Michel Brisseau (1676-1743) in 1707, a half century later. Brisseau, in the preface of his book, Traite de la Cataracte et du Glaucoma (Paris, Houry), described a soldier whose cataract he couched. The soldier subsequently died and Brisseau dissected his eye and extracted the lens, giving conclusive proof of the true nature of cataract. In 1707, Antoine Maitre Jan (1650–1725) independently published his findings of examination of the lens from a deceased cataract patient in his Traite des Maladies des Yeux and he also discovered the onion-like layered structure of the lens. Soon after, there appeared reports on three successful lens extractions in living patients whose lenses 8
Chapt e r 1 C atarac t e xtracti o n f r om anci e nt ti me s to th e 2 0 t h c e ntur y
were subluxed into the anterior chamber: two operations by Charles de St. Yves (1667–1736) in 1707 and 1716 and another by the noted surgeon Jean Louis Petit (1674–1760) in 1708. The surgeon Jean Méry (1645–1723) proposed to the Paris Academy of Science in 1707 that they sanction extraction as a method for treating cataract. “Extraction seems to be as safe as couching; it may be even less risky,” Méry stated. “The aqueous reforms easily. The cornea does not have any blood vessels and therefore does not become affected with inflammations”. However, the Academy showed little interest in the new procedure and as we shall see during the course of this book, so many other great ideas in relation to cataract surgery awaited someone to “convince the world” of their value. Jacques Daviel (1693-1762) was the individual destined to accomplish this and thus claim the title of the inventor of cataract extraction. How was it that Daviel decided to extract the cataractous lens from the eye? He had trained as a doctor in Rouen as an apprentice to his uncle a Dr Saillou. At the age of 20 years old, he became an assistant surgeon in the French Army, eventually serving as an assistant to Xavier Bouquot at the Hotel-Dieu in Paris. Notable to this appointment was the fact that the Hotel-Dieu was the only public institution in Paris where the dissection of cadavers was permitted. When there was the last major outbreak of plague in southern France in 1720 Daviel volunteered to go to the area to treat those afflicted. 100.000 died in this epidemic. He was honoured for his work and in 1722 appointed to be Master Surgeon. In 1733 at the age of 40 Daviel performed his first cataract operation, a couching procedure, which went very well. It has been speculated as to why he decided to devote the rest of his medical career to cataract surgery. The consensus is that in 1734 he met John “Chevalier” Taylor an itinerant cataract surgeon and oculist to George II of England and other royal houses. Although Taylor was reputed to be a good surgeon, others were less impressed. He operated on Johann Sebastian Bach with disastrous results that led to the composer’s death. None the less Daviel was attracted by the idea of devoting himself to ophthalmologic surgery. To be successful in couching cataracts demanded speed and considerable skill, and Daviel became a master of this procedure in short order. It considerably helped that his status in Marseilles and his protection by Louis XV allowed him to circumvent the social and religious restrictions that limited the use of cadavers for practice surgery in 18th century France. His experience from cadaver surgery enabled Daviel to avoid learning from live patients through trial and error. Daviel became famous over the next decade or so as a skilled practitioner of the couching technique. He was sought after all over Europe and travelled widely. By 1746 he was appointed surgeon oculist to King Louis XV and moved to Paris. However it required 2 failed couching procedures in 1745 and 1747 which encouraged Daviel to consider the extraction technique. Although he had already expressed reservations about the couching technique in a letter to a friend. He was aware of the work earlier in the century of Brisseau, Maitre Jan, St. Yves and Petit, relevant to cataract extraction, and also knew of Méry’s unsuccessful attempt to gain the endorsement of the Paris Academy of Sciences for the operation. In the first of these failed operations the cataract would not move backwards and the lens broke up into pieces. Daviel decided to open the eye with a knife and scissors to remove the lens fragments. Although the initial result seemed good the eye became infected and was lost. Daviel responded to this disaster by designing a blunt instrument—rather than the usual sharp needles—with which he continued to depress cataracts. Of greater importance was his stated resolve to bring a new “great 9
HIST ORY AND EVOLUT ION OF MODERN CATARACT SURGERY
idea” for cataract surgery he was developing to a “certainty by continuing to work daily on the eyes of cadavers”. The second, but more crucial, case that brought Daviel’s cataract extraction technique into existence occurred 2 years later, on April 8, 1747. The patient was M.Garion, a wig maker, and the operation was clearly described by Daviel himself: “I begin with the left eye whose cataract seemed more mature and yet I was not able to depress it. The pupil appeared cloudy after the operation and the patient saw absolutely nothing. I then proceeded to the right eye and had just as much trouble. Having failed in every manoeuvre to push down the cataract in this eye, I decided to open up the cornea, as I had done with the hermit. I widened the aperture, then I raised the cornea with small forceps, inserted my small spatula through the pupil and extracted from the posterior chamber of the eye the whole lens, divided and broken into several pieces during my initial procedure. After this extraction, a part of the vitreous humour oozed out: it had been disrupted by the first operation but, despite this inconvenience, the patient discerned objects well. The operation had no harmful sequelae and, after some time, the patient was cured”. Daviel concluded “I decided henceforth to operate for cataract exclusively by the extraction of the crystalline lens”. It is interesting to speculate as to why Daviel, who after all had very good results with couching and on which his reputation rested, opted to champion extraction. It may be that he was intrigued to use his undoubted surgical skills in what he felt was a more challenging operation and thus to claim it as his own. Shortly thereafter Daviel performed his first “planned” cataract extraction. The patient a lady had her eye opened the capsule disrupted and the nucleus removed . Apparently within 2 weeks the eye had recovered. Daviel with his access to cadaver eyes and in his surgery on patients improved the technique and the instruments he used (Figure 3).
Figure 3. Daviel’s technique and instruments for cataract extraction
10
Chapt e r 1 C atarac t e xtracti o n f r om anci e nt ti me s to th e 2 0 t h c e ntur y
Figure 4. Sharpe’s cataract knife
By 1752 he had performed 206 extractions with a success rate of 88%. Considering the surgery was done without asepsis or anaesthetic these results are impressive. He now felt ready to present his results which he did to the Academy of Surgery in Paris. Following peer review, which included another surgeon trying the Daviel technique, albeit with less impressive results, the paper was published. Daviel staunchly defended his method of extracting cataract, and surgeons in Europe and England divided into those who preferred couching and those adopting extraction. This dispute continued until the end of the nineteenth century and was often termed the “hundred years war”, by medical historians. This was particularly true in Great Britain where one of the doyens of the surgical fraternity Sir Percival Potts (1714-88), famous for Pott's disease and Pott's fracture, disparaged the operation of cataract extraction. He described it as “merely a fashion” and strongly advocated couching. Not all his colleagues felt this way and Samuel Sharp (1700-78) of Guys Hospital in London designed a knife to make the cataract incision that obviated the need to enlarge the incision with scissors. He also was the first to perform intracapsular extraction. An Austrian surgeon, Joseph Beer (1763-1821), candidly expressed his view of the Potts’s attitude to extraction as follows. “Some of the English ophthalmologists rejected the extraction method in order to please Mr Pott, others in order to stand out among the crowd. A third group did it out of national pride and out of hate of all things French. And a fourth group did it because they had bad results due to prejudice or clumsiness”. Increasingly over the ensuing 70 years surgeons adopted ophthalmology as a specialist undertaking although the terms ophthalmology and ophthalmologist did not become common currency until the middle of the 19th century. By the second decade of that century dedicated eye hospitals were starting to appear often in response to returning soldiers from fighting in Egypt with so called “Egyptian ophthalmia”. This was either gonorrhoea or trachoma and affected huge numbers. What was the patient’s perspective on cataract extraction in the 19th century? There is a vivid description by The Reverend Patrick Bronte (1777-1861), father of the famous authors the Bronte sisters, of his operation for cataract in the mid-19th century. “Belladonna—a virulent poison—was first applied, twice, in order to expand the pupil—this occasioned very acute pains for only about five seconds—The feeling, under the operation—which lasted fifteen minutes, was of a burning nature—but not intolerable—as I have read is generally the case, in surgical operations. My lens was extracted so that the cataract can . . . never return in that eye.” At about this time one of the great figures of European ophthalmology Albrecht von Graefe
11
HIST ORY AND EVOLUT ION OF MODERN CATARACT SURGERY
Figure 5. von Graefe cataract knife
(1828-70) was changing the way that cataract extraction was performed by introducing what he called “linear extraction”. In order to facilitate this surgery he designed a special knife with a long thin blade to open the eye. It has since then been called the Graefe knife (Figure 5). Instead of the eye being incised from outside in this knife was passed across the anterior chamber and cut outwards to create the incision. It required some considerable manual skill to be able to do this well and consistently but the technique was used by most cataract surgeons for the next 100 years. Von Graefe also moved the incision to the superior position rather than inferiorly as described by Daviel. One of the important figures in the move to create eye hospitals in the UK was George Guthrie (1785-1856). He was the first surgeon at the Royal Westminster Hospital for Treatment of Diseases of the Eye which was founded in 1816. He describes how he felt when he invited von Graefe to his hospital to perform cataract surgery in 1850. “I was satisfied that he knew as much as I did about it, and I was infinitely more gratified to perceive that he did not know more.” What were the results of cataract surgery like in the latter half of the 19th century using the von Graefe technique? George Cowell (1836-1927) a surgeon at the Royal Westminster Ophthalmic Hospital in London published a book of lectures on cataract in 1883. He quotes the results of 100 operations for cataract performed by himself. He claims that 90% were successful, 7% had defective vision and 3% panophthalmitis. We do not know exactly what success meant for the patient. Up to this point as we have seen cataract surgery was carried out without any anaesthesia. In 1884 this was to change when Carl Koller (1857-1944), working in Vienna, introduced cocaine as a topical anaesthetic. The following year the same drug was used as a retrobulbar injection by Hermann Knapp, a German ophthalmic surgeon working in New York. When procaine appeared in 1904 most surgeons moved to this form of anaesthesia in the 20th century. Although most surgeons were performing extracapsular surgery some were trying to remove the whole lens, intracapsular surgery as performed by Samual Sharp in the 18th century. One of these was Ignacio Barraquer (1884-1965) working in Barcelona. He devised an instrument which he called the erisophake. It consisted of a suction cup that was applied to the lens to enable its removal through a 180 degree von Graefe incision (Figure 6). Although many surgeons came to visit Barraquer few took up his technique. Intracapsular surgery did not really become popular until the late 1950’s when his son Joachim Barraquer (19272016) started to use D-chymotrypsin to dissolve the zonule. This was then combined with the use of the cryoprobe invented by Tadeusz Krwawicz (1910-88) from Poland and improved by Percy Amoils from South Africa. One of the major disadvantages of cataract surgery in the pre lens implant era was the require12
Chapt e r 1 C atarac t e xtracti o n f r om anci e nt ti me s to th e 2 0 t h c e ntur y
Figure 6. Erisophake in use by Prof Ignacio Barraquer
ment to use aphakic spectacles post operatively. There was a significant magnification of the image reaching the retina and the visual field was reduced to the central 30%. The peripheral field was also distorted by the spherical aberration of the thick spectacle lens. Although Leonardo da Vinci had suggested the idea of a contact lens in 1508 in his book Codex of the eye, Manual D. It was the astronomer Sir John Herschel who realised the design concept required for a contact lens. He in 1845 published two new ideas in the Encyclopedia Metropolitana. The first was for a spherical capsule of glass filled with animal jelly, while the second was a mould of the cornea that could be impressed on a transparent medium, albeit it of indeterminate nature.. It was not until 1887 however that the first contact lens manufactured from glass and fitted to cover the entire eye was made by the German glass blower F.E. Muller and fitted by the ophthalmologist Adolph Eugen Fick (18291901). These were heavy and uncomfortable and did not become much used. Just before the second world war in 1936 the British firm ICI produced a lightweight plastic polymethyl methacrylate (PMMA) and this was used to make contact lenses (Figure 7).
Figure 7. Early PMMA scleral contact lens
13
HIST ORY AND EVOLUT ION OF MODERN CATARACT SURGERY
Figure 8. Sir Harold Ridley performing Graefe section with preplaced sutures
In 1948 just before Sir Harold Ridley used PMMA for the first intraocular lenses micro-corneal contact lenses appeared. Although Ridley was operating in a manner in 1949 that von Graefe would have recognised from a century before apart from the use of 6/0 black silk sutures (Figure 8). Having done the extraction of the cataract how was the wound to be closed? It is interesting that although sutures had long been used in general surgery their general use in cataract surgery came quite late. The Boston surgeon Henry Willard Williams (1821-95) described the use of a corneal suture in 1865. The importance of preplacing the suture was emphasized. However, although many other authors described its use in the ensuing decades this idea did not gain traction until better suture materials appeared in the second half of the 20th century. Most surgeons in 1865 were using some form of conjunctival bridge to assist in the wound closure first described by Louis-Auguste Desmarres (1810-82) in 1858 (Figure 9). This technique with multiple modifications was the commonest means of wound closure well into the 20th century. Some like Wilhelm Czermak (1856-1906) working in Prague advocated suturing the conjunctiva to the sclera to improve the stability of the wound (Figure 10).
Figure 9. Desmarres conjunctival bridge after Beer’s knife incision
14
Chapt e r 1 C atarac t e xtracti o n f r om anci e nt ti me s to th e 2 0 t h c e ntur y
Figure 10. Czermak conjunctival incision and suture closure
By the beginning of the 20th century cataract surgery had undoubtedly become an operation which skilled surgeons were performing with good results. In the obituary of Sir Anderson Critchett (1845-1925) Surgeon Oculist to King Edward VII of Great Britain and the doyen of cataract surgeons in his day we find the following statement. “To see Critchett removing a cataract in the heyday of his skill was to see the perfection of operative technique.” No doubt all surgeons would like to have something similar said of them. Thus, by the midpoint of the 20th century with great skill in evidence and established techniques in place and a material already in use for contact lenses namely PMMA, the next great step in cataract surgery was about to appear. As will be seen in the chapter on intraocular lenses what Sir Harold Ridley (1906-2001) called “the cure for aphakia” was soon to be realised. However, it would take a war with aerial combat and the curiosity of a medical student to bring this idea to the mind of the inventor.
15
2 The history of incisions in Cataract Surgery Joan Balgos, Jorge L. Alio, Andrzej Grzybowski, Piotr Kanclerz, Howard Fine
1. Introduction Evolution or revolution? From 180˚ to 2.5mm Clear Corneal Incisions The earliest documented cases of cataract removal involved couching – wherein an instrument was used to push the cataractous lens to the vitreous cavity. In 600 BC Sushruta described this procedure where he was also said to perform a small incision almost like a paracentesis – but it was not large enough to enable the extraction of the entire lens. Jacques Daviel (1693-1762) for several years specialized in couching cataracts, yet difficulties encountered in couching for two patients gave him the idea to open the cornea and successfully remove the lens. In 1752, he presented his innovative method of cataract extraction to the French Academy of Surgery. (Lois, 1787) The procedure described by Daviel was the precursor of extracapsular cataract extraction (ECCE). (Mehta, 2012) Primarily, a triangular knife was used to open the cornea at its lower edge – the incision was later enlarged and the lens manually delivered. The incision performed by Daviel was curvilinear and flap-like. Albrecht von Graefe later described an incision made closer to the limbus and in a straight fashion, in the upper part of the cornea. (von Graefe, 1867) (von Graefe, 1865) He used a special knife of his construction for performing the incision - a sharp-pointed tapered blade (Figure 3) that prevented aqueous leakage and globe softening. Placement of the incision in the upper quadrant was beneficial to corneal biomechanics and wound healing. Jacobson first reported a failure rate of 3–5% with von Graefe’s technique, compared to 10% with the classical semicircular incision but the introduction of antisepsis decreased this to less than 2%. (Jacobsen, 1884) von Graefe's incision became the principle technique for cataract removal for almost a century, although a significant disadvantage for this technique was the learning curve associated with it. Samuel Sharp (1709–1778) was the first to perform intracapsular cataract extraction (ICCE) - his 17
HIST ORY AND EVOLUT ION OF MODERN CATARACT SURGERY
Figure 1. The procedure Jaques Daviel ďŹ rst suggested which involved opening the cornea in order to remove the crystalline lens (top), and the blade he designed in order to perform the procedure (bottom)
Figure 2. The knife designed by Samuel Sharpe (top), and his original description of the procedure of intracapsular cataract removal (bottom)
Figure 3. The knife designed by Albrecht von Graefe
Figure 4. A comparison of the incisions constructed by Daviel (Fig. I and Fig. III) and von Graefe (Fig. II and Fig. IV)
18
Chapt e r 2 Th e h i s to r y of inc is i ons i n Cataract S ur g e r y
report was presented to the Royal Society of London and subsequently published in the Philosophical Transactions. (Sharp, 1753) For this technique a limbal incision was performed and the lens was manually expressed with the thumb. Sharp designed a knife which resembled a narrow lancet - it had two slightly concave sharp edges, and was a little less than an inch long. In general, the incision used for ICCE was constructed in a similar manner as the incision used for ECCE albeit slightly larger. Barraquer, on the other hand, proposed a more scleral incision with a conjunctival flap completely covering the sectioned area. An advantage of this approach was the absence or rapid resolution of striate keratitis, in contrast to those encountered with corneal incisions. (Barraquer, 1959) Phacoemulsification, introduced by Kelman in 1967, was the next exciting step in the field of cataract surgery as it enabled intraocular lens removal through a small incision. However, the development of intraocular lenses made it necessary to extend the initial incision in order to accommodate lens implantation – temporarily impeding the progression to small-incision cataract surgery. (Kelman, 1967) The development of new technology - especially the development of foldable intraocular lenses – has allowed for the widespread use of small corneal incisions in ophthalmic surgery. 2. Scleral incisions Superiorly placed scleral tunnel incisions are still used nowadays by beginning cataract surgeons and in manual small incision cataract surgery (MSICS) – a procedure introduced by Blumenthal and derived from ECCE. (Blumenthal M, 1992) The principal feature of MSICS is hydrodissection and hydrodelineation of the lens lamella, followed by hydroexpression of the nucleus core into the anterior chamber. MSICS does not require an ophthalmic viscoelastic device nor complex instrumentation, and for this reason is commonly used in developing countries where cost is a major issue. (Haldipurkar SS, 2009) Scleral incisions induce significantly less astigmatic change compared to clear corneal incisions. (Olsen T, 1997) However, peribulbar or retrobulbar anesthesia is required. Scleral tunnel classifications are listed in Table 1.
7DEOH &ODVVLͤFDWLRQ RI VFOHUDO WXQQHO LQFLVLRQV &RQMXQFWLYDO IODS DUFKLWHFWXUH
Limbal-based flap Fornix-based flap
%DVHG RQ VFOHUDO JURRYH VKDSH
Smile incision
Following the limbus
Straight incision
Straight line
Frown incision
Curve opposite to the limbus
Blumenthal side cut
Straight line with sides receding from limbus
Chevron ‘v’ incision
V-incision, sides receding from the limbus
19
HIST ORY AND EVOLUT ION OF MODERN CATARACT SURGERY
Conjunctival flaps are created prior to the scleral incision – with peritomy size measured according to the size of the intended incision. Fornix-based flaps provide unobscured visualization compared to limbal-based flaps. Fine proposed vertical releasing incisions in the conjunctiva and Tenon’s with the same width as the flap. (Fine, Architecture and construction of a self-sealing incision for cataract surgery, 1991) These incisions should extend approximately 5 mm back, with the sub-Tenon’s bluntly dissected with scissors. 0.5 to 1.0 mm of conjunctiva should remain attached to the limbus during peritomy, and the created flap is folded upside down. Subsequently, light cautery is performed, and the scleral bed is stamped with a 5 x 8 mm grid of dots with methylene blue. Primarily a curvilinear groove of approximately 0.3 mm depth is placed with the anterior limit of the incision placed 2–3 mm behind the limbus. The width of the incision may reach up to 7.0 mm, depending on the requirements of the intended procedure. Linear or curvilinear incisions following the limbus might be easier to create, however these induce greater astigmatism. While creating the incisions, the globe should be kept stable with either a Weck twist grip or with forceps. Chevron incisions have two arms forming an obtuse angle, each of which passes laterally from the apex. This method allows for better surgical control of a rigid IOL during insertion sequence. (Pallin, 1990) Frown incisions might be more difficult to create, although their advantage is that they cause lower surgically induced astigmatism (SIA). (Singer, 1991) Following groove creation, a crescent knife is used to create dissect a scleral tunnel forward to Descemet’s membrane. At this point, a side port is made and aqueous is exchanged for viscoelastic in order to stabilize the anterior chamber. A sharp keratome blade is brought into the scleral tunnel, continues within the tunnel and subsequently advances into the anterior chamber. The stepped incision creates an internal corneal lip that has valve properties. The surgeon should constantly guide the tip of the blade, as a straight cut in Descemet’s membrane is necessary for correct architecture and self-sealing properties of the incision. During the surgery, it is important to avoid applying traction on the roof of the scleral tunnel. At the end of the procedure the scleral wound integrity is checked by applying pressure with a Weck-cel sponge. Only a correct tunnel incision architecture, at least 1–2 mm into the clear cornea, has self-sealing wound properties. Placing a horizontal suture might be recommended in cases of leakage, which occurs in less than 5% of cases. (Fine, Architecture and construction of a self-sealing incision for cataract surgery, 1991) For incisions 5.0 mm-wide or larger, an infinity suture should be placed. (Fine, Architecture and construction of a self-sealing incision for cataract surgery, 1991) Subsequently, the conjunctival flap is unfolded back and placed in its bed. Frequently it is adherent within one hour, not necessitating the placement of a suture. Astigmatism with scleral incisions Scleral tunnels under 3.0–3.2 mm of size hardly produce any irreversible corneal changes. (Hayashi K, 1995) (Samuelson SW, 1991) Koch defined the so called “incisional funnel”, created by two imaginary lines which separate as the distance from the limbus increases. Incisions within this funnel are astigmatically neutral. Longer incisions can be made further from the limbus, while closer to the limbus only shorter ones, in order to sustain corneal stability. 20
Chapt e r 2 Th e h i s to r y of inc is i ons i n Cataract S ur g e r y
Complications of scleral incisions Creating a scleral incision might be more challenging and time consuming. The conjunctiva is highly vascular and hemostasis might be required during the procedure, sometimes on more than one occasion. Initial grooves that are too superficial could lead to a thin and fragile scleral flap that is prone to tearing or lacerations. Initial grooves that are too deep could lead to premature anterior chamber penetration. Corneal tunnels that are performed too anteriorly might cause striae during manipulation of the phacoemulsification tip or an instrument, hampering visualization. 3. Clear Corneal Incisions Clear corneal incisions (CCI) are now preferred by an increasing number of cataract surgeons worldwide. 2–4 Historically these procedures were first done with incisions that were 4 mm long. Small incisions for performing cataract surgeries started out as 3 mm astigmatically neutral scleral tunnels. Girard and Hoffman are credited as the first to call this posteriorly located incision as such. Along with Kratz, they described the creation of a corneal shelf prior to entering the anterior chamber through the cornea. This was said to prevent iris prolapse, and made the wound strong and waterproof. Following these initially described techniques, self-sealing scleral tunnel incisions have varied with respect to width and scleral groove configuration. Other authors subsequently describing their own variations to the clear corneal incision. Arnott and Shimizu started using clear corneal incisions for phacoemulsification in the late 1970s. Arnott first introduced temporal clear corneal incisions for secondary anterior chamber intraocular lens (IOL) implantation more than 40 years ago. Fine used clear corneal cataract incisions for phacoemulsification after the development of foldable IOL implants, initially closing incisions with a suture but later shifting to self-sealing corneal incisions.5 Initially, the indications for CCI included patients with pre-existing filtering blebs, taking anti-coagulants, (Park HJ, 1997) with blood coagulation disorders or cicatrizing diseases such as ocular cicatricial pemphigoid or Stevens-Johnson syndrome. As these incisions can be performed under topical anesthesia, they became more and more commonly used because of the decreased risk of complications associated with regional blocks – namely lid hematoma, diplopia, ptosis, globe penetration, or optic nerve injury. (Ali-Malkkila T, 1991) (Duker JS, 1991) (Kim C-H, 2016) (Devoto, 1997) Other advantages of CCIs include ease of approach to the incision site, preservation of options for future filtering surgeries, increased stability in refractive results, no need for bridle sutures, and ease of drainage due to the inferior location of the lateral canthal angle to the incision. Preoperative Evaluation Routine baseline ophthalmologic examination is needed prior to performing any cataract surgery – this includes baseline visual acuity, automated and subjective refraction with best corrected vision, intraocular pressure measurement, anterior chamber and crystalline lens evaluation and posterior pole examination. Additional tests that may be requested include endothelial cell count and corneal pachymetry, as well as keratometry. As cataract surgeries are increasingly becoming refractive procedures, computerized corneal topography and corneal aberrometry should, perhaps, be considered the most important pre-operative examinations. 21
HIST ORY AND EVOLUT ION OF MODERN CATARACT SURGERY
Techniques Various techniques for creating clear corneal incisions have been explored and developed in the course of the history of cataract surgery. Advances in phacoemulsification technology have already enabled the transition from large scleral incisions to increasingly smaller clear corneal incisions. However, patient expectations with regard to visual recovery and refractive stability drives the development of even newer technology in order to provide good outcomes. Improved understanding of wound healing and newly available technology for imaging gives surgeons an in vivo picture of wound architectu- Figure 5. Clear corneal incision 6 re and other factors that may affect post-operative outcomes and optical quality– such as astigmatism, and lower order and higher order aberrations. Fine gave a classification of incisions according to the entry site.5 Scleral corneal incisions involve entry into the anterior chamber through incisions posterior to the limbus, usually made with a peritomy and a scleral flap. In limbal incisions, on the other hand, the anterior chamber can be entered through the limbus and the conjunctival insertion. As these first two incisions involve manipulation of the conjunctiva, there is a propensity to induce bleeding or to cause conjunctival swelling – both of which would make the surgery technically more difficult hence making it take longer to complete. Scleral tunnels are also fraught with possible complications such as scleral disinsertion if made too deep, or tunnel roof problems if made to shallow. Clear corneal incisions are made anterior to the conjunctival insertion. These have risen in popularity because they have been associated with improved surgical efficiency, better cosmesis and faster visual recovery. Similarly, incisions might be classified based on the groove depth; with no groove (single plane), with a shallow groove (400 Pm) and deep groove (over 400 Pm). These are summarized in Table 2. 7DEOH &ODVVLͤFDWLRQ RI FRUQHDO LQFLVLRQV %DVHG RQ H[WHUQDO LQFLVLRQ ORFDWLRQ
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Clear corneal incision
Entry anterior to conjunctival insertion
Limbal corneal incision
Entry through the conjunctiva and limbus
Scleral corneal incision
Entry posterior to the limbus
Single plane
No groove
Shallow groove
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Deep groove
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Chapt e r 2 Th e h i s to r y of inc is i ons i n Cataract S ur g e r y
Clear corneal incisions may be made temporally, nasally or superiorly. Traditionally, the choice of incision location depended on the laterality of the eye to be operated on as well as surgeon preference. A survey conducted on ASCRS members worldwide in 2003 showed an increasing trend in creating temporal incisions over incisions located superiorly.3 As the creation of the clear corneal wound is one of the most critical steps in cataract surgery, it is vital to ensure proper incision configuration during construction. There are many variables that contribute to the dynamic morphology of the corneal incision intraoperatively and in the early postoperative period. Basic entry approaches may vary when creating clear corneal incisions. The critical angle of entry for human globes is said to range between 46 to 48Ëš for clear corneal incisions, and between 36 to 49 Ëš for limbal incisions. Wound edges tend to be better apposed with high intraocular pressures in smaller angles, with a tendency to gape in response to lowered intraocular pressures. An inverse relationship was reported with larger angles.7 Several authors advocate for the use of biplanar or even triplanar incisions as these types of wound architecture are said to exhibit more stability and resistance to aqueous leakage. On anterior segment imaging, these incisions exhibit an arcuate profile, and have greater stability because of the so-called tongue in groove configuration.6,8,9 Carefully constructed triplanar incisions exhibiting square geometry are said to be the most stable. The pre-incision technique, wherein a 2.85 mm clear corneal groove is made with the side edge of the knife parallel to the limbus, prior to performing the clear corneal incision and entering the anterior chamber, has been described. It is said to facilitate the surgery by controlling the incision and enabling extension as needed later in the procedure. The pre-incision also showed no significant keratometric refractive changes up to 3 months after surgery.10
Figure 6. Artist's interpretation of a cross-section view of clear corneal incisions6
23
HIST ORY AND EVOLUT ION OF MODERN CATARACT SURGERY
Figure 7. In vivo anterior segment Ocular Coherence Tomography (OCT) of a 2.20 mm incision showing the incision angle, configuration of a stromal incision, and internal and external wound characteristics11
Figure 8. Anterior segment OCT of a 2.20 mm incision 1 day postoperatively, showing a Descemet’s flap and endothelial gaping.11
When clear corneal incisions were first introduced and described, they were as wide as 4.0mm. Since then, progressively smaller incisions have been used for cataract surgeries. Previously, the maximum incision width that could be left without sutures was 3.5 mm. Masket and Belani found that nearly square 3.0 mm incisions, resulted in ease of closure and resistance to hypotony in the early postoperative period.12 Cataract surgery with even small incisions – called micro-incisionshas developed in the last 14 years. Microcoaxial cataract surgery is performed with 2.2 mm corneal incisions, while biaxial cataract surgery is performed with incisions less than 2.0 mm.13 The advantages of using micro-incisions include ease of incision construction, greater intra-operative anterior chamber stability, minimized astigmatism, and faster wound healing. There is still a debate ongoing between the advocates of biaxial surgery and microcoaxial surgery, as some authors have reported larger incision angles in these groups with a change in configuration from arcuate to linear over time.8 These were attributed to the sleeveless tips used in the former, and the modifications in the fluidics settings, which could theoretically lead to more traumatic changes in the incision edge.14 However, there are studies that provide contrary results, showing insignificant differences in immediate postoperative stability and long-term healing between biaxial and microcoaxial incisions.13,15
24
Chapt e r 2 Th e h i s to r y of inc is i ons i n Cataract S ur g e r y
Instrumentation – microsurgical blades and the advent of the femtosecond laser Over the past decades, with the evolution of cataract surgery, a variety of instruments and tools have been conceptualized and created in terms of the construction of clear corneal incisions. Microsurgical blades and keratomes, in particular, have been the mainstay of these instruments. They have been manufactured with several materials – diamond, sapphire, stainless steel, and ceramic composites among others. Regardless of the material used for the keratome, it is important to consider blade edge sharpness and penetration when selecting the blade for use. Up to a point the sharper a blade is, the more control a surgeon has and the more reproducible the incisions become. A material’s hardness can affect corneal penetration. Diamonds, for example, are used to make thin, rigid and sharp blades. Blade entry into the anterior chamber requires a smaller blade, with less chances of keratome tilting and of damaging adjacent ocular structures.16,17 In contrast, metal blades are thicker and have to be made longer and at a sharp angle in order to enable corneal penetration. A steel keratome would understandably cost less than a diamond keratome, but it is usually meant for single use as its performance is reduced with more uses. Diamond blades last longer, however they cost much more. The use of ceramics and ceramic composites is still being investigated but its effectivity compared to the two more well-known materials remains to be seen.16 The femtosecond laser was first introduced in 2001, and has since been used for a variety of corneal and refractive procedures such as LASIK, SMILE and corneal transplantation. It has also been adapted for use in several steps in cataract surgery- especially in the creation of the clear corneal incision, capsulotomy, and lens fragmentation. Since then, several groups have published studies detailing the benefits of using femtosecond lasers for creating clear corneal incisions. Imaging studies of manually created clear corneal incisions – even those made by highly experienced surgeons - reveal that they often end up as one-plane or two-plane incisions instead of the intended tri-plane incisions. Grewal and Basti reported only 19% of manually created incisions with tri-planar geometry. In contrast, femtosecond-laser created incisions were found to be within 10% of the intended length, depth and angle measurements.18 Femtosecond laser-created incisions have been shown to Figure 9. The image-guided system for the femtosecond laser be truly multi-planar, and hence leak-free. platform allows the surgeon to plan details such as incision As these incisions are made with computer placement, length, depth, and number of planes24
25
HIST ORY AND EVOLUT ION OF MODERN CATARACT SURGERY
Figure 10. Anterior segment OCT images comparing the profile of clear corneal incisions created with the femtosecond laser (A) and with a metal keratome (B)18
guidance, they have been demonstrated to be precisely created and repeatable, with a consistent multi-planar architecture. This has been demonstrated in cadaveric eyes, as well as in clinical studies.18–21 Femtosecond lasers have been used with cataract surgeries in various ways, and have even been applied to coaxial small incision cataract surgery, and bimanual and coaxial micro-incision cataract surgery with excellent outcomes and insignificant changes in higher order aberrations.22 Because incisions made with the femtosecond laser are highly stable, these have also been clinically shown to have significantly better sealability – requiring less wound hydration and anterior chamber reformation.23 OCT imaging of femtosecond-laser generated incisions showed lower endothelial gaping and misalignment, Descemet membrane detachment, and posterior wound retraction.18 Furthermore, the use of the femtosecond laser with other steps in cataract surgery limits intraoperative wound manipulation and effective phacoemulsification time – giving added protection to the endothelium, and decreasing the risk of Descemet’s membrane detachment and subsequent difficulties with wound sealing.21,24 Patient screening and selection is key when contemplating femtosecond laser-assisted cataract surgery, as a subset of patients are poor candidates – such as patients with glaucoma or a functioning bleb or valve, patients with orbital anatomy that does not allow for effective docking, and patients who are unable to position for the femtosecond laser.25 While there is no significant difference in inflammatory cell response after performing surgery with a femtosecond laser-created corneal incision, upregulated postoperative wound-healing response has been demonstrated such that topical steroids are still needed during the early postoperative phase.26 An important limitation to the widespread use of the femtosecond laser is the significant cost in acquiring and maintaining these machines, and the subsequent additional expense shouldered by the patient. Other cost considerations include training of staff and increased time required to
26
Chapt e r 2 Th e h i s to r y of inc is i ons i n Cataract S ur g e r y
counsel patients about the technology.25 Another concern that has been raised regarding the incorporation of the femtosecond laser into standard cataract surgeries is the need to transfer patients from one machine to another in order to perform different steps of the procedure. Creation of the incision, capsulotomy and lens fragmentation are performed with the femtosecond laser, after which the rest of the cataract surgery is completed with the phacoemulsification machine in the surgical suite. This involves an added step to the surgery, prolonging operative time. Once the logistics performing surgery on two platforms has been addressed, and once manufacturers find ways to lessen the cost of acquisition and maintenance of these machines, it would be safe to say that femtosecond lasers will become even more present in the field of refractive and cataract surgery in the years to come. Complications Some complications are unique to clear corneal incisions. If the conjunctiva is unintentionally incised, ballooning of the conjunctiva can develop which may compromise visualization of anterior structures. Early entry into the anterior chamber might result in an incision of insufficient length to be self-sealing, with an increased tendency for iris prolapse, and later requiring the placement of a suture at the conclusion of the procedure. Late entry may result in a corneal tunnels that are too long, leading to difficulty in insertion of instruments into the anterior chamber, leading to formation of striae in the cornea during manipulation and hampering visualization of the anterior chamber.9 Manipulation of the phacoemulsification handpiece intraoperatively may result in tearing of the roof of the CCI, particularly at the edges, compromising the ability to self-seal, or occasionally resulting in minor detachment, or scrolling of Descemet’s membrane. Incisional burns similarly compromise self-sealability, result in corneal edema and severe induced astigmatism.27 In addition, manipulations in the proximity of the wound can cause epithelial abrasion. Clear corneal incisions have been found to be significantly associated with an increased risk of endophthalmitis28, especially in incisions with persistent leakage leading to ocular hypotony.29 In cataract surgery databases the risk for postoperative wound leak or rupture was reported to be 0.02–1.1%.30,31 Although this complication might be associated with endophthalmitis, subsequent wound suturing is infrequent. For example in a study by Zaidi et al. of the 11 of 1000 consecutive patients undergoing PCS with wound dehiscence only one eye required formal wound revision.30 In a study on 100 consecutive eyes Chee checked the water-tightness by dripping 5% povidone-iodine on the corneal incisions in the operating room.32 Wound leakage at the conclusion of PCS was present in 31% of consecutive eyes. Most of the cases were related to the side-port incisions and were asymptomatic, requiring only additional hydration. Tamsulosin intake might increase the probability of wound dehiscence with the relative risk of 3.81 compared to control.33 It was believed that limbal incisions manifest greater stability and faster healing compared to CCIs.34 Histological studies conducted on feline eyes showed that limbal incisions had an earlier fibroblastic response and presented stability 7 days after surgery. However, the main issue for evaluating an incision safety is sealing rather than healing. Thus, CCIs that remain closed at the conclusion of surgery, probably remain sealed afterwards. Other critique was related to relatively lower strength of CCIs compared to scleral incisions.35,36
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HIST ORY AND EVOLUT ION OF MODERN CATARACT SURGERY
It should be noted that poor wound apposition is believed to result in postoperative hypotony. Interestingly, in a study by Shingleton neither paracentesis not keratome incision leakage was noted by fluorescein strip testing at the completion of surgery in eyes with hypotony defined as IOP lower than 10 mmHg 30 minutes postoperatively.37 It was concluded that early hypotony may be a result of a disequilibrium between postoperative aqueous production and outflow, rather than incisional leakage. Suturing did not affect the incidence of postoperative hypotony in this study. Improving Post-Operative Outcomes with Clear Corneal Incisions Wound Closure Sutureless clear corneal incisions have become the standard of care when it comes to performing cataract surgeries. Several groups, however, have raised concerns that incisions left without definitive closure might have a propensity to leak in the early post-operative phase, increasing the risk for endophthalmitis.38 Intraocular pressure fluctuation is common in the early post-operative period, and hypotony can create a relative vacuum, allowing the ingress of fluid and potential pathogens into the eye.29,39,40,39 In order to improve outcomes with regard to wound closure and healing, several measures have been proposed including the use of block anesthesia, intracameral antibiotics prior to ending the surgery, making three-planed square incisions, and using appropriate instruments and techniques with the aim of avoiding wound manipulation and thermal injury in order to preserve wound integrity. Care should be taken when inserting intraocular lenses, as these have been shown to exert force on the wound margins, causing distortion of the surrounding tissue, and possible uncontrolled tears to the margins. Steps to improve surgical results have been advised and these include matching the injector’s external nozzle to incision size, enlarging the incision with a keratome to accommodate the intraocular lens and the injector nozzle41, and even inserting intraocular lenses faster to lessen the damage42. Postoperative eye patching is also being advocated by some groups, especially in incisions deemed to be with compromised integrity or if significant
Figure 11. Stromal hydration being performed on the main incision48
28
Chapt e r 2 Th e h i s to r y of inc is i ons i n Cataract S ur g e r y
Figure 12. Anterior segment imaging of a clear corneal incision 1 day postoperatively, with adjacent stromal edema. There is good apposition of the wound edges, and no endothelial or epithelial gaping is seen.11
corneal epithelial damage was sustained during surgery, as it has been found to be helpful in promoting epithelial healing and reduced epithelial gaping on the first post-operative day43. Modified Seidel testing, wherein a sponge is applied to the incision edge in order to locate a leak, has been suggested.44 However, the force applied has not been standardized, and it is important to note that physiologic intraocular pressure fluctuations range from 5 to 40 mmHg, and even up to 1.0 ounce of force applied45, or an intraocular pressure drop to 5 mmHg39 has been shown to cause wound gaping and leakage.46 Stromal hydration, first described by Fine et al, is the most common technique used to reinforce the self-sealing clear corneal incision. It is effective – Mifflin et al have shown that at least 50% of incisions leaked before hydration as compared to after stromal hydration.47 With stromal hydration, there is decreased risk of fluid ingress into the anterior chamber.48 It is typically performed by hydrating the lateral walls and roof of the internal stromal tunnel with a forceful injection of fluid from a small-bore cannula. Wong developed an alternative wherein hydration is performed on an anterior or supraincisional stromal pocket – which is said to provide enhanced wound sealing.46,47 While balanced salt solution is commonly used, stromal hydration with cefuroxime has also been suggested as an additional step to give antibiotic prophylaxis prior to the conclusion of the surgery.49 Anterior segment imaging studies have shown stromal hydration effects to be present from 24 hours to at least one week after surgery. Sutures are used to seal the wound when a leak has been observed in spite of stromal hydration in routine cataract surgeries50, and particularly in cases with corneal thermal injury.51 Non-absorbable sutures are regarded as superior to absorbable sutures, because they allow exact wound apposition and retain their tensile strength through the wound healing process.52 Suture technique depends on incision size and location. The traditional method of suture placement is the vertical suture wherein the needle is passed from the corneal apex side of the incision and aiming it toward the scleral side. The suture is then tightened and tied – usually with a 3-1-1 knot.53 Additional sutures may be required, depending on the wound closure achieved, and the knots need to be buried at the end of the procedure. Several alternative suturing techniques are employed by other groups. In one technique, the needle is passed through the scleral side of the
29
HIST ORY AND EVOLUT ION OF MODERN CATARACT SURGERY
Figure 13. The traditional vertical corneal suture technique.53
Figure 14. The reverse suturing technique proposed by Narvaez et al 53
incision first, exits on the cornea side towards the apex, and closed with an adjustable 1-1-1- knot.53 An X-stitch may also be used – aside from the vertical component, it has a radial component which approximates the wound edges. This may lead to with-the-rule (WTR) astigmatism. (PH, 1994) Horizontal mattress sutures have been reported to reduce initial post-operative WTR astigmatism with corneoscleral incisions 54, and Fine further developed the principles of horizontal suturing to develop the infinity suture for longer incisions. (IH, 1991) Intrastromal corneal sutures have also been proposed.55 The traditional suturing method has inherent problems as knot burial may sometimes lead to anterior chamber shallowing, subconjunctival hemorrhage, or loosening of adjacent sutures – prolonging the surgery. Loose sutures or exposed knots may cause foreign body sensation. In addition, loose, or broken sutures may act as foci of infections, tissue necrosis or leak. Tight sutures cause wound distortion and Surgically Induced Astigmatism (SIA); multiple stitches tend to induce more astigmatism as well.56 Due to suture-related complications, several groups have advocated for suture removal as soon as epithelialization occurs. Several wound closure products for topical application are currently being explored.46,57 These include cyanoacrylate glue, fibrin, and polyethylene glycol-based products.58 Hydrogel ocular bandages have been developed as a promising class of sealants.59,60 Two formulations for corneal wound closure are commercially available –the Ocuseal liquid ocular bandage (Beaver-Visitec International) and 30
Chapt e r 2 Th e h i s to r y of inc is i ons i n Cataract S ur g e r y
Figure 15. Horizontal intrastromal corneal suture55
Resure adherent ocular bandage (Ocular Therapeutix Inc). Papers have reported the use of corneal welding or photochemical processes as a way to seal clear corneal incisions – although caution is advised as it may involve the use of toxic light-absorbing dyes and is said to denature collagen fibers.61,62 Surgically induced astigmatism, corneal aberrations, and optical quality Increased patient expectations have led to several added considerations when planning for cataract surgery. Factors that play significant roles in refractive outcomes and hence optical quality include effective lens position, management of pre-existing corneal astigmatism, and surgically induced astigmatism – the last two of which may be theoretically addressed or even worsened with placement of corneal incisions. Corneal biomechanical properties, such as hysteresis, are also believed to influence the cornea’s reaction to a surgical procedure – and using these to better predict refractive outcomes are being studied.63 Corneal refractive changes after cataract surgery are related to both the size and location of the incision. While no significant difference was found in terms of astigmatic outcomes between nasal or temporal incisions, Song et al found a greater flattening effect and greater negative coma higher order aberrations in superiorly located incisions. They attributed these results to the smaller vertical corneal diameter as compared to the horizontal, hence a closer location to the visual axis, and to possible mechanical changes induced by the upper lid.64 Longer clear corneal incisions were also found to induce significant astigmatism – briefly causing flattening in the total and anterior cornea and wound-related steepening in the posterior cornea – in the immediate postoperative period.65 With increased understanding of aberrations and topographic changes created by incisions on the cornea, several groups have advocated placement of the main incision in the steeper axis – especially in eyes with preoperative mild to moderate astigmatism less than 2.60D66 as this has been shown to induce corneal flattening along that meridian.67,68 There is also a dynamic change in the magnitude of astigmatism after the surgical procedure. According to Holladay astigmatism is lowest between 60 and 365 days post operatively.69,70 Although some studies suggest that astigmatism decreases as far as 6 months after surgery,71,72 majority of the authors agree that the most substantial decline is observed up to 3 months after the surgery.73,74 These
31
HIST ORY AND EVOLUT ION OF MODERN CATARACT SURGERY
Figure 16. Insignificant corneal changes in patients who underwent coaxial microincision surgery (top) and biaxial microincision surgery (bottom)81
findings are significant as they indicate the time for prescribing spectacles. On the other hand, Ostri et al. found that automated refraction is stable 1 week after uncomplicated cataract surgery. However, there is a trend for inconstancy if the refractive target is missed with 1.0D or more.75 In long-term follow-up after phacoemulsification cataract surgery a change towards against-therule astigmatism of about 0.2–0.4 D in a period of 10 years was observed. Such a change occurred in both the cataract surgery group and the control group with no statistically significant difference.76 Postoperative corneal astigmatism tended to be lesser when performed with scleral incision than with 3.0mm corneal incisions. However, with incision width at 2.0 mm or less – which are commonly used today – induced astigmatism of the central cornea is the same as that of scleral incision surgery.77 Statistically insignificant astigmatic changes were noted with smaller corneal incisions78–80. Corneal aberrations – astigmatism, spherical, coma, and higher order aberrations- as an objective means to evaluate corneal optical quality, also showed insignificant changes with decreased incision size.13,80,81 Interest has recently been generated as to wavefront aberration and astigmatic changes induced by femtosecond laser-created corneal incisions. Clear corneal incisions made with the femtosecond laser, 2.75 mm in size and made with three planes, were found to induce less steepening on anterior central corneal topography, as compared to manually created incisions82. Initial papers comparing manual clear corneal incisions made by experienced surgeons to femtosecond laser-created incisions have shown no significant difference in induced astigmatism83 – although results might vary among laser platforms as some incision-locating systems might rely on the limbus measurements thus affecting incision location84. Significant differences were also found in terms of wavefront aberration changes in incisions made with femtosecond lasers as opposed to manually created incisions. These differences were attributed to the biomechanical impact induced by cutting the corneal lamellae with a blade as opposed to with a femtosecond laser85. 32