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Nucci P (ed): Pediatric Cataract.

Dev Ophthalmol. Basel, Karger, 2016, vol 57, pp 49–68 (DOI: 10.1159/000442501)

Visual Rehabilitation in Pediatric Aphakia Michael X. Repka Johns Hopkins University School of Medicine, Baltimore, Md., USA

Abstract

This monograph discusses some of the choices and outcomes to be considered for each child undergoing cataract surgery and then during the beginning years of visual rehabilitation. Although the nature of care is described broadly, personalization of a child’s care varies considerably based on laterality (one or two eyes affected) and on the age at surgery. There are numerous choices that are made during the postoperative years to assist the child and family to deal the best they can with the problems that

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The management of childhood cataract begins at the initial contact with the family and typically extends far into the child’s future. Decisions affecting long-term care and visual outcomes are often made in these initial preoperative encounters. Treatment will vary depending on whether the cataract is unilateral or bilateral and whether it is infantile onset or later. Thorough discussion of the treatment options is needed, especially with description of the life-long management issues for the child. Visual outcomes will vary, with the best visual acuity results being observed in older children with bilateral cataracts. Visual rehabilitation of children with unilateral cataract requires use of a contact lens or an intraocular lens (IOL) for the best result with a chance for binocularity. Only about 50% of eyes with unilateral infantile cataract will develop vision of better than 20/200. For bilateral cataracts, both contacts and IOLs can be used, as well as aphakic glasses. Excellent visual outcomes are typical unless glaucoma develops, which occurs in up to 30% of cases. Cataract surgery after 1 year of age is associated with substantially better visual outcomes. The use of an IOL is most commonly accepted and performed for cataract in one or both eyes after 1 year of age. Prior to 1 year of age, significantly more secondary surgical procedures are required to manage opacification of the optical axis with the use of an IOL compared with the use of surgery and contact lens correction. Amblyopia therapy for unilateral cataract needs be continuous from the time of surgery until at least 8 years of age. It is often difficult to perform this therapy over such a long time period, with compliance with © 2016 S. Karger AG, Basel less than 30% of prescribed time during infancy at 5 years after surgery.

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they encounter. For instance, some parents simply cannot manage contact lenses because they themselves have poor vision or poor fine motor skills.

The diagnosis of cataract early in life is a transformative event for parents and their infant or young child. It has not been very many years since this diagnosis was associated with lifelong unilateral or bilateral irremediable blindness. For example, just 60 years ago, the management of monocular cataract was considered doomed to a poor outcome because of insufficient surgical instrumentation to remove the lens and lack of optimum optical correction [1]. These two problems were addressed in the 1970s with the introduction of vitrectomy instrumentation and extended-wear contact lenses that could be handled by a parent and worn by an infant [2–4]. These solutions made infantile cataract surgery safe and effective in the field of pediatric ophthalmology, with an excellent chance of restoration of useful and in many instances normal vision in both unilateral and bilateral cases.

Post-surgical rehabilitation requires coordinated efforts over many years involving parents, ophthalmologists, optometrists, schools, low vision/mobility specialists, occupational therapists, and pediatricians. For the child, this diagnosis is the beginning of life-long involvement with ophthalmology to obtain optimal ocular health monitoring, treatment, and visual rehabilitation over 90 or more years of life. While cataract surgery performed during childhood is often technically challenging and rarely routine, follow-up care is always difficult, time intensive and associated with many obstacles. Unilateral cataract has significantly greater impacts on families and is associated with more treatment difficulties in children than bilateral cataracts [5]. In the Infant Aphakia Treatment Study (IATS), about 8% of caregivers had a significantly elevated (above the 85th percentile) total stress score [6]. This score seems lower than consensus opinion, possibly because of support received from clinical coordinators and investigators working on the study. Bilateral cases may be less difficult for parental management because the need for amblyopia therapy is much less and acceptance of some form of refractive correction is much easier. Presumably, the need for intensive, years-long therapy is the source of the larger effect of unilateral disease. While stress is inevitable for these parents, it is not universal and likely can be managed with counseling and support from the physician, office staff and parental support groups.

Substantial support can be found in person and on the web (e.g., Pediatric Glaucoma and Cataract Family Association; pgfca.org).

After surgery, there are frequent postoperative visits to assess healing, intraocular pressure (IOP) elevation, and refractive error or contact lens fit, which are often quite difficult to complete. In many cases, a direct ophthalmoscope and retinoscope are the only instruments that can be used. Even after the postoperative period, these children continue to return for frequent exams. These visits are performed to monitor refraction, amblyopia therapy, the clarity of the optical axis and the IOP. These visits may occur at least quarterly, and for children with contact lenses, they can occur as often as monthly when the parents cannot independently manage the insertion and/or removal of the extended wear lenses. Clinicians should recognize that at each visit, it

may not be possible to obtain all of the desired information. However, if all of the data can be acquired over multiple visits, then they are still providing quality care.

Before development of the Tonopen (Reichert Technologies, Depew, Ny., USA) and Icare Tonometer (Icare Finland Oy, Vantaa, Finland), frequent examinations under anesthesia were necessary to monitor children for the development of aphakic glaucoma. This serious condition may develop in up to 59% of surgically treated eyes [7, 8]. These tonometers have made periodic IOP testing in the office feasible for the majority of children. While it may not be possible during each visit, if the child is nursing, drinking a bottle, sleeping or being entertained with amusing antics, then the measurements can be successfully obtained during some of the visits. This technology has led to a marked reduction in the frequency of examinations performed under anesthesia, just at the time when there is increasing concern about general anesthetic neurotoxicity, which has life-long consequences on the developing brain [9]. However, for children who need to be examined, a consensus statement on pediatric anesthesia continues to note that it is unethical to withhold sedation and anesthesia from those who require it for optimal care [10]. The authors have recognized that relevant animal data are sufficiently robust but that more human research is needed. Some authors have suggested that repeated exposure to ketamine may be even worse [11].

Ketamine has been a commonly used anesthetic because a primary reason for performing an examination under anesthesia on a child with surgical aphakia has been for glaucoma detection and monitoring. The treating ophthalmologist should remain aware of changes in these recommendations for anesthetic care of children and be able to explain why an examination conducted under anesthesia is necessary. In any case, current opinion recommends that procedures performed under general anesthesia on children less than 3 years of age should be avoided if at all possible.

Ocular growth and the consequent change in refraction during early childhood following cataract surgery in one or both eyes are substantial and by no means uniform or predictable. The axial length of the human eye increases from 16.8 mm at birth to 23.6 mm for normal adult eyes [12]. In terms of refractive error change, much of this axial length alteration is offset by corneal flattening from 51.2 diopters (D) to 43.5 D, with the remainder offset by flattening of the lens. The combined effects of these three factors must be predicted and managed in both pseudophakic and aphakic eyes.

The logarithmic decline in refractive error of the aphakic eye appears to be affected primarily by age at surgery, but it may be impacted by vision, unilateral versus bilateral aphakia, and the presence of an implant. One mathematical model was used by McClatchey and Hofmeister [13] to calculate the magnitude of reduction in the aphakic spectacle correction, revealing that the refractive error declined from about +19.00

Visual Rehabilitation in Pediatric Aphakia

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Dev Ophthalmol. Basel, Karger, 2016, vol 57, pp 49–68 (DOI: 10.1159/000442501)

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Ocular Growth

Table 1. Axial length, keratometry and aphakic refraction in children by age Age group, years

Axial length, mm

Keratometry, D

Aphakic refraction, D

0–1 1–2 2–3 3–4 4–5 5–6 6–7 7–9 10 – 15

19.2 20.2 21.4 21.8 22.3 22.7 22.9 22.6 23.8

45.2 44.9 44.1 43.7 43.2 43.7 43.4 44.2 43.5

18.77 16.87 15.00 14.51 13.92 12.84 12.69 12.67 11.02

to +11.00 D between 6 months and 10 years of age (table 1). In most cases, surgical eyes do not achieve such a rapid or complete reduction in hyperopia unless there is increased IOP. In addition, early lens removal surgery in the eyes of monkeys without cataract appears to affect axial elongation, with pseudophakia retarding this growth more than aphakia [14, 15].

Early studies of the use of intraocular lenses (IOLs) in children reported that pseudophakic eyes have a slightly lower rate of refractive growth than aphakic eyes, further complicating preoperative decision-making [16]. Better visual acuity has been weakly associated with decreased ocular growth about 10% of the effect [17]. A subsequent retrospective study has confirmed a lower rate of refractive growth among pseudophakic compared with aphakic eyes, and this difference has been found to be clinically and statistically significant using a mathematical model (difference of 1.1 D, p = 0.03) [13]. The myopic shift was greatest in children who had undergone surgery at a younger age. The apparent myopic shift was also greater in eyes with high-power IOLs due to an optical phenomenon analogous to the effect of vertex distance [13]. This latter effect has been eliminated with the development of an updated model, and the difference in growth between aphakic and pseudophakic eyes is no longer significant, although the trend of greater myopic shift in aphakic eyes remains [18]. There is also a trend of a lower myopic shift in the eyes of patients who have undergone surgery prior to 6 months of age for both aphakia and pseudophakia. However, variability in the data is substantial; therefore, these data are more interesting than actionable.

A retrospective study evaluating the effect of age on unilateral surgery did not find a significant difference in axial length change in subgroups of patients who were younger and older than 18 months of age at surgery [19]. However, a trend of less growth was observed in the operated eyes of both age groups compared to the fellow eyes. The prospective IATS found slightly greater elongation in IOL-implanted eyes

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Axial length and keratometry were adapted from Gordon and Donzis [12]. Aphakic refraction was adapted from McClatchey and Hoffmeister [13].

compared with contact lens-treated eyes after 1 year [20]. The infants’ fellow eyes in both studies were also longer at baseline, as were those in all groups at follow-up, suggesting that surgery, reduced vision or changes associated with cataract affect(s) axial elongation.

Initial Rehabilitative Choices

Visually significant cataract during childhood is promptly treated upon diagnosis with lens extraction and often with concurrent anterior vitrectomy/posterior capsulotomy. At that point, the work of visual rehabilitation with glasses, contact lenses, spectacles and IOLs begins [21]. Each treatment plays an important role in the process of care. Contact lens correction has been used for more than 30 years with good results. IOLs have been used for almost the same period of time, but issues with lens design, posterior capsule management and lack of Food and Drug Administration approval initially delayed their acceptance [22, 23]. Since these early reports, IOLs have been increasingly used over the last 20 years, initially for monocular cataract, and today for unilateral and bilateral cases, most juvenile cases and even many infantile cases. Most research in this area has consisted of small case series, slowing the development of clear practice guidance. An important exception is the IATS, which has prospectively studied the outcomes of children with unilateral cataract randomized to receive either an IOL or contact lens during the first year of life, after 4.5 years of follow-up. Follow-up visits at 1 year and 5 years have been reported [24, 25]. This key study is discussed later in this chapter.

Before the first surgery is undertaken, a thorough discussion is performed with the parents, and often the grandparents, to discuss what is going to happen over the next few months as well as over the next few decades. An open discussion of the many choices that they are about to be faced with that will impact rehabilitation in the years ahead is needed, plainly laying out the tasks at hand and openly discussing successes and failures that they and their child will encounter. These conversations may not fit well into an emergently scheduled appointment time but often occur over several days as the shock experienced by the parents of learning that their child will need surgery and be at risk of a lifetime of visual impairment has lessened.

While the constant use of spectacle lenses has been abandoned following adult cataract surgery, eyeglasses still have important roles in the management of pediatric cataract, even for patients using IOLs. There are many reasons for their continued use, so it is important to explain preoperatively that the surgery will not eliminate the need for glasses, that frequent changes will be necessary, and that quality production may

Visual Rehabilitation in Pediatric Aphakia

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Dev Ophthalmol. Basel, Karger, 2016, vol 57, pp 49–68 (DOI: 10.1159/000442501)

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Aphakic Spectacles

be hard to find. Glasses are prescribed to be worn constantly for protection from inadvertent injury of both eyes after 2 years of age for all postoperative children. In addition, the lens material protects the retina from UV radiation exposure. Perhaps most importantly, the power of a contact lens, and especially of an IOL, is rarely exact for the current refractive error; thus, fine-tuning of the refractive error with glasses is often needed, as discussed below for each treatment approach. The power of aphakic glasses is measured and the prescription is verified with the concave or flat surface toward the lensometer (back vertex power).

In some children with bilateral aphakia, the refractive solution chosen is aphakic spectacles. This may be because some parents cannot be expected to learn to handle contact lenses. Given the frequency of hereditable cataract, this is a common problem when the visual outcomes of the prior generation were not very good due to either amblyopia or glaucoma. Other children might find that eyeglasses are a suitable solution because of worry about the frequent loss of contact lenses (by the child or family), resulting in failure to sustain treatment, or because they simply cannot afford contact lenses or the lenses are not available.

While I generally choose contact lenses if IOLs have not been used, there are no data showing a poorer outcome from aphakic lenses. Aphakic glasses are typically well tolerated by children, although they are heavy and certainly not fashionable (fig. 1).

The lenses are very thick centrally and are associated with substantial magnification, which helps vision but is not attractive to children when they look at themselves or when other children look at them. In addition, they have a ring scotoma, which can be very annoying as objects pop in and out of the visual field.

Aphakic lenses come in a number of designs, and the choice greatly affects acceptance. An excellent optician and laboratory should determine the smallest lens and optic size that can reduce the central thickness and weight of the lens. In infants and toddlers up to about 2 years of age, it is satisfactory to use single vision lenses with the focal point at about 50–66 cm. After this age, it is customary to add a bifocal segment

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Fig. 1. Aphakic spectacles in an adolescent with aphakia, demonstrating substantial magnification.

to the distance correction, although I consider this choice with each parent and in some cases delay it for months to a year or more depending on the developmental state of the child.

The universally available lens material for aphakic lenses is CR-39, which is a plastic and is much lighter than glass. On occasion, a polycarbonate single vision lens is available, which is lighter and has a higher index of refraction, producing a quality product. Even so, these lenses are very thick centrally, and small frames are much preferred to maintain the reduced weight and magnification. In many cases, the bifocal segment is placed too low to be of much use. Many manufacturers use a lenticular design, with an optical lens of approximately 30 mm on a carrier lens (fig. 2). An alternative is the use of a full-sized aphakic lens, but with an aspheric front surface to reduce aberrations. A flat posterior lens surface will also reduce magnification. However, in the current lens market, the determining factors are the power, base curve, and frame shape and dimensions, with the lens size being a key determinant in the chosen lens design. The three available base curves in single vision are +16.00, +18.00, and + 19.00. More variety is available for lower powers and for bifocal lenses used by older children.

In unilateral aphakia, spectacles as the refractive solution are sub-optimal in most cases because the aniseikonia will be a barrier to development of binocularity due to the difference in image sizes between phakic and aphakic eyes. This difference is as much as 30%, making fusion impossible. On the other hand, if the child will not tolerate a unilateral contact lens and is not a candidate for a secondary IOL, then the use of spectacles during amblyopia therapy would be obligatory to have a chance of the development of any useful vision in the aphakic eye. The use of glasses would also be needed for protection. If the amblyopia does not improve, then it is reasonable at about 6 years of age to balance the lens powers so that the child will continue to have protection of the fellow eye without lens asymmetry.

Visual Rehabilitation in Pediatric Aphakia

Nucci P (ed): Pediatric Cataract.

Dev Ophthalmol. Basel, Karger, 2016, vol 57, pp 49–68 (DOI: 10.1159/000442501)

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Fig. 2. Lenticular design of aphakic glasses, showing the carrier lens with aphakic correction of about 30 mm in the center.

Fig. 3. Bilateral aphakic child wearing contact lenses, with good vision in both eyes.

The spectacle lenses should have good UV absorption characteristics (at least below 380 nm), and a tint may help with light sensitivity. Some children like lenses that darken when they go outside.

The most common method of correcting monocular aphakia and binocular aphakia in infancy is the use of an extended-wear contact lens (fig. 3). Success with monocular cataract surgery and rehabilitation was reported for the first time in 1973. In a case series, 2 of 21 children developed 20/40 vision, something that was considered impossible prior to that time [2]. Arguably, the most common contact lenses prescribed today were introduced many years ago and retain many advantages. They are the Silsoft® and Silsoft® Super Plus Contact Lenses (Bausch & Lomb, Incorporated, Bridgewater, N.J., USA), which are made from a silicon elastomer with excellent oxygen permeability [26]. A silicon extended-wear lens is used because it can be worn for as long as a month at a time without a problem compared to rigid lenses, which must be handled daily. The lens design is lenticular, with a ‘bubble’ of material on the central aspect of the anterior lens surface. In many cases, it is this shape that allows parents and physicians to actually see the otherwise clear lens on the corneal surface. The Silsoft® line is available in a range of powers (from +11.50 to +32.00 D in varied steps). A younger patient typically begins with a Silsoft® Super Plus, which comes in three base curves (7.5, 7.7, and 7.9), a diameter of 11.3 mm and powers ranging from +23.00 to +32.00 D in 3 D steps (+23.00, +26.00, +29.00, and +32.00). Silsoft® aphakic lenses come in 5 base curves (7.5, 7.7, 7.9, 8.1, and 8.3 mm), two diameters (11.3 and 12.5 mm), and powers ranging from +11.50 to +20.00 D in 0.50 D steps. The vision of most aphakic children may be suitably corrected with these lenses [27, 28].

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Contact Lenses

Visual Rehabilitation in Pediatric Aphakia

Nucci P (ed): Pediatric Cataract.

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For infants and most young children, I initially prescribe a +29.00 D and 7.5 mm base curve lens. If this does not provide enough plus power with an overcorrection of about +2.00 D, then a +32.00 D lens is ordered, and the +29.00 D lens is retained for use later during the first year of life. The investigators in the IATS have recommended using a +32.00 D lens if the initial refraction cannot be determined during the first postoperative week, and this situation does occur frequently, on occasion due to thin vitreous hemorrhage [29]. The fit is assessed by watching for excessive motion or decentration with blinking and frequent dislodging of the lens from the eye by the eyelids. Given the steep corneas of the children being fit these lenses, they do not move much, even when they fit well. A fluorescein dye assessment of the tear layer between the cornea and posterior surface of the lens may be performed. It should show the presence of some dye under the apex of the lens and at the far edges, with the lens riding on the peripheral cornea. A lens that moves too much or falls out frequently may be too flat, and the next steeper base curve may be substituted to achieve better retention. However, for the very youngest infants, a suitably tight lens may not be available, and the lens will fall out periodically. This problem seems to self-correct in just a few months as the eye grows a bit, the cornea flattens and the fit improves.

Another important problem with silicon lenses like the SilsoftÂŽ is the hydrophilic coating, which is added to improve the wettability of the anterior lens surface. This coating tends to degrade after a few months of use, causing the lens to appear frosted.

In addition, crystalline deposits frequently form on the anterior surface. These two factors plus eye growth cause individual lenses to rarely last for more than 6 months.

This property does not seem to harm fit but makes over-refraction more difficult than with a new lens. On occasion, it causes the examiner to think that there is opacification of the posterior capsule or the posterior IOL surface with secondary cataract formation. The difference is obvious, with a clear retinoscopic reflex and easier refraction observed when the contact lens is removed.

The refractive errors of infants and children change frequently during the first year of life, with marked slowing thereafter. Frequent confirmation of the correct contact lens is needed, usually every other month during the first 18 months of life and then every 3–4 months until 3 years of age. Silicone contact lenses may be worn from 1 to 30 days prior to removal and cleaning if tolerated. In most cases, the lenses easily last the full month. Parents who themselves are successful contact lens wearers most rapidly gain expertise with their insertion and removal, often when the baby is nursing or has fallen asleep. On occasion, the lens will remain out for a day if there is no replacement lens available or there is amblyopia in the fellow eye.

This should not be a cause for concern and can be used therapeutically. These lenses are cleaned and disinfected with a multi-purpose solution made for soft contact lenses. The manufacturer of these solutions recommends an 8-hour period for adequate disinfection. If the patient has bilateral aphakia, then the parents can rotate a single lens between eyes if necessary while they are waiting to receive a replacement lens.

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Following surgery, the contact lens is placed at the 1-week postoperative visit, although some clinicians perform this placement as early as the completion of surgery.

Initial monitoring of the contact lens is part of postoperative care, often once weekly for 2 weeks. Following that period, I have the parents bring their infant to the office at least monthly for removal and reinsertion of the contact, with checking of the IOP and refraction during most of these visits. The process is greatly expedited by the availability of a second set of lenses, so that there is no wait for cleaning and a spare can be used if one lens falls out. As the family gains facility with lens handling, these visits become quarterly. As the child ages, the Silsoft® base curve may be flattened to 7.7 mm to improve centration and retention. Some children seem to maintain the steep corneal curvature well into their teenage years and continue to do well with a 7.5 base curve in the Silsoft® lens.

During the first few years after infant lensectomy, it is common to have contact lenses lost or rubbed from the eye. In many cases, the parents will find the lens in clothes or bed linens or among toys. In most of these cases, the lens will still be useable after cleaning and disinfection in a multi-purpose solution. The loss rate is about one lens per year per eye in my experience, similar to the rate reported 30 years ago (0.75 lens/year) [30]. As these children age, new lenses will typically be bought less frequently because of the slowing of the rate of change in refractive error, but surface deterioration then becomes more of a factor in determining the timing of replacement.

Rigid gas-permeable lenses are a less costly alternative with many more options, but they require more experience with customization and trial-and-error fitting. In many places, contact lens fitters have limited expertise with infants and young children, substantially reducing the theoretical advantage of a wider range of parameters for fitting. Rigid materials that allow for extended wear are available, and the lenses can be manufactured with especially steep base curves and higher powers that are not available in silicon lenses. Lens diameters range from 7.8–9.5 mm. The base curve is typically fit 1.0–1.5 mm steeper than the flattest keratometry reading. The IATS group has recommended fitting the initial trial lens based on a formula of the base curve plus 1.3 mm to derive the lens diameter. The lenses should be lenticular in design to reduce edge thickness and increase comfort as the lids move over the lens.

During infancy through about 18 months of age, contact lenses should be adjusted to overcorrect hypermetropia by approximately +2.00 D. Silsoft® lenses for these children often range from –4.00 to –1.00 D in 3 D steps. For toddlers, the contact lens correction should be nearly emmetropic for distance or overcorrected by up to +1.00 D. These children should have bifocal spectacles prescribed, which are to be worn over the contact lenses when they begin to participate in close-range activities.

Spectacles also serve as injury and UV protection for both eyes.

The IATS provided quality prospective data on the outcomes of unilateral infantile cataract treated with contact lenses. At 4.5 years, the median logMAR visual acuity was 0.90 (Snellen equivalent, 20/159), with about 50% of treated eyes having visual

acuity of less than or equal to 20/200 [25]. However, visual acuity of 20/32 or better was found in 23%. The fellow eye of unilateral aphakic children should be treated based on its refractive error.

The management of children with bilateral aphakia who wear contacts lenses has long been successful in terms of postoperative outcomes. A recent report has mirrored my experience, demonstrating that two lenses are not much harder than one to manage and that the visual outcome is usually very good, unless glaucoma develops [31].

Probably the most important factor easing the treatment burden is that these children often do not need amblyopia therapy beyond refractive correction.

An important concern with contact lens correction is the cost of purchasing the lenses over many years. The current discounted price of a single Silsoft® lens is about USD 150 (as of January 2016), which may be cost prohibitive for many families.

The use of lens implants for aphakia during childhood is widely accepted for visual rehabilitation in older children and is being increasingly accepted during infancy [32, 33].

Typically, IOLs are used after 1 year of age for most children and for both unilateral and bilateral cataracts. This minimum age for implantation in normal children has continued to decline as more experience has been gained and good outcomes have been achieved, in spite of the absence of regulatory approval [33–35]. In the past, monocular implants were offered during the first year of life or whenever contact lens use in the estimation of the physician and parents would not be easily achieved. However, 5-year follow-up results have been reported by the IATS [25], providing substantial information about the impact of the choice of refractive rehabilitation for unilateral cataract in infants. At this time, the IATS group has concluded that the weight of evidence at 5 years is in favor of contact lens use with a secondary implant provided later, assuming no extenuating circumstances [25]. In spite of the power of this study, it is important that surgeons do not generalize the results to children older than 1 year of age, to those with bilateral infantile cataracts, and to those with other ocular anomalies. Such children were not included in the IATS. A much smaller study randomized children under 2 years of age (mean age of about 6 months) with unilateral cataract to lensectomy with a primary IOL or lensectomy with a contact lens and a secondary IOL after a mean of 32 months of contact lens use [36]. These authors reported similar outcomes in visual acuity and adverse events.

A small single-piece IOL with an optic diameter of 5.0–5.5 mm designed for capsular bag fixation is implanted [28, 37, 38]. The most frequently used implants are acrylic and foldable. These lenses have been quite successful for primary aphakia and also in the posttraumatic cataract setting [39]. Visual rehabilitation after unilateral trauma has been remarkably successful with the use of IOLs.

Visual Rehabilitation in Pediatric Aphakia

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Intraocular Lenses

Current IOLs are not designed to be interchanged (although some interchangeable IOLs are in development). Consequently, the current models do not adjust for the myopic shift of the growing eye. This leads to the complicated planning process for determining the power of the lens to be implanted. The second preoperative issue to consider and develop a plan for is management of the posterior capsule, as nearly every capsule opacifies quickly (fig. 4). Primary posterior capsulectomy and anterior vitrectomy are advocated for most children younger than 4 years of age. Both of these decisions may differ depending on the maturity and health status of the child, whether the surgery will be unilateral or bilateral, and if bilateral, how soon the surgery will be required.

If an IOL is to be used, the parents need be advised that glasses will be necessary for many years for protection and for fine-tuning of the IOL. Many patients may have parents who have received IOLs, after which no glasses were needed, leading to potential confusion.

The health status of a child is important to consider before proceeding with cataract surgery. Is the child a candidate for the use of eyeglasses or contact lenses? If neither is likely to be successful, then IOL implantation will afford at least partial correction of the aphakic refractive error, allowing for a better quality of life. Can the child sit for a YAGlaser posterior capsulotomy in the office or will they be unable to tolerate in-office evaluations and laser capsulotomy, need frequent examinations under anesthesia and be unwilling to have incisional capsulotomy? A child who can complete an office examination with a slit lamp is a better candidate for an IOL without removal of the posterior capsule primarily. If frequent sedated examinations are going to be likely, then a more precisely selected IOL should be placed during a secondary surgery performed at a later age.

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Fig. 4. Anterior segment view of a posterior chamber IOL with a dense posterior capsule and cruciate capsulotomy made with a neodymium-YAG laser. Even capsulotomy of this size may be difficult for retinoscopy and ophthalmoscopy.

Once the decision has been made to proceed with IOL implantation, consideration of the power of the IOL is necessary. The target refractive error is a pre-surgical objective for the immediate postoperative refractive error. In nearly all cases, this error will be hyperopic, given the expected myopic shift of most children. The planned target refractive error varies substantially with age and widely among experts. One consensus scheme adopted in the IATS suggests target refractive errors of about +8.00 D in young infants, +6.00 D later during the first year of life, +4.00 to +5.00 D at 2 years of age, and +2.00 D at 6 years of age, with extrapolation in between ages and adjustments based on the state of the fellow eye [24]. Beyond this age, a target of low hyperopia of about +1.00 D to emmetropia is used. Similar targets are used for bilateral and unilateral cases.

A few surgeons have preferred to target close to emmetropia in unilateral infantile cataract cases, performing adjustments in later years with myopic spectacles, removing a piggyback IOL or simply planning to perform a lens exchange. Adopting any of these approaches requires that the child wear spectacles or contact lenses in addition to the implant at some point. These spectacles are typical single vision glasses worn to see intermediate focal distances until 2–3 years of age, after which a bifocal should be prescribed for most toddlers and school-aged children. Some high school-aged students may prefer monovision for functional and social reasons, especially those who have good vision but poor or absent fusion.

For the older patient with unilateral cataract, the target refractive error may be modified by the refractive development of the fellow eye or if there is a family history of refractive development. In most cases, this modification tends to make the target error less hyperopic.

Once the decision is made for a primary IOL placement, the surgeon needs to calculate the power of the IOL based on the planned target refractive error and biometry of the surgical eye, keratometry and axial length. Keratometry can be performed separately with a keratometer or a hand-held keratometer/refractor (e.g., Retinomax) or by corneal topography or optical biometry, which captures many measurements in addition to the axial length and corneal curvature. In some cases, keratometry can be estimated to be about +45.00 D, as it introduces minimal error into calculations.

For determination of axial length, both contact and immersion A-scans have been used with reasonable success. The immersion A-scan may be slightly more accurate than the contact A-scan, but the differences are small given the inherent inaccuracy of the prediction of individual future eye growth [40, 41]. While nearly all adolescents and teenagers can undergo these tests in an office, younger children may need to have them performed in an operating room under anesthesia immediately before surgery.

Optical biometry was introduced in 2000 and can be used not only for determining axial length and keratometry but also for measuring anterior chamber depth, lens thickness, pachymetry and retinal thickness if desired. The key advantage in its

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Target Refractive Error

pediatric usage is that it is a noncontact technique, allowing for success in many younger children. One other advantage of optical biometry is that the axial length is measured to the center of the macula, while this value can only be estimated with ultrasound. This advantage is the most important if there is a posterior staphyloma.

A disadvantage is that it does not work well with dense cataracts, which are more common among pediatric patients. Optical biometry is much more accurate for measuring axial length than ultrasound, but this precision is probably relatively unimportant in pediatric care because it is offset by the substantial variability of eye growth following surgery. In my opinion, this instrument has allowed for the completion of IOL power planning for more children prior to surgery rather than during the operative session. This allows time for thorough consideration of the refractive issues for each individual patient.

Numerous formulas have been developed for calculation of IOL power. In a number of studies of pediatric IOL surgery on the hyperopic or short eye, which is basically every childhood cataract, the Sandler-Retzlaff-Kraff (SRK)/Theoretic, SRK II, Holladay I, and Hoffer Q formulae are preferred, with no clear differences in outcomes [42–44]. For unilateral cataract in infants, the IATS group found that the Holladay I and SRK/Theoretic formulae resulted in equally good predictions [45], that the absolute prediction error was 1.8 D (the mean of the absolute values of postoperative refraction), and that it was greater with shorter axial lengths. Adjustments to the manufacturer’s A constant based on personal outcomes should be considered when sufficient experience is obtained.

It is expected that although many children having cataract surgery at a young age will be left aphakic, some will have secondary IOLs placed. In some of these cases, they will be placed due to contact lens intolerance, while in others, they will be placed to allow for a couple of years to pass so that the infant eye can grow and the IOL power selection can be more accurate. This sequential approach has been of some concern because every child would have to have a minimum of two surgeries per eye. This concern has been somewhat allayed based on the results of the IATS, which has found that early IOL placement is associated with an increased risk of having a second (or more) procedure for occluded visual axis, with at least as good of an outcome for vision compared with contact lenses. If the anterior segment is deep enough, secondary implant surgery with anterior vitrectomy and sculpting of the Soemmering’s ring is generally straightforward to perform, as a firm capsular support for sulcus implantation is present.

The utility of the secondary IOL approach for infants has been shown in retrospective case series. Kim et al. [46] reported 37 infants who received bilateral surgery, with IOL placement at about 2 years of age. This highly selected group without com-

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Secondary Intraocular Lens Implantation

plications such as glaucoma would be expected to do well and did so, achieving bestcorrected visual acuity of 20/40 or better in 44.0% of eyes with a median of 20/50.

The target refractive error for secondary implants is based on the general rules described above and then adjusted for individual patient characteristics. Less has been reported about prediction errors for these patients, but these errors should be decreased because the children are typically older and have longer axial lengths, more accurate biometry, and fewer subsequent myopic shifts. In teenagers, the target is typically emmetropia, allowing for minor myopic shifts.

Surgical aphakia is a rare cause of visual loss in the population. However, these children seem to dominate the amblyopia management of many pediatric ophthalmology practices because they have frequent visits over many years and do not have as good outcomes as children with strabismic or anisometropic forms of amblyopia. The low prevalence of vision loss occurs simply because cataract is far less common than the other causes of amblyopia. Shaw et al. [47] reported that among 1,531 amblyopic children, strabismus was the cause in 45%, anisometropia in 17%, a combination of the two in 35%, and deprivation due to cataract or corneal scarring in 3%. However, significant visual impairment from amblyopia among this childhood cataract subgroup is quite high. Over the last 20 years, while much clinical research has been completed showing the value of refractive correction, patching, and atropine eye drops for anisometropic and strabismic amblyopia, there has been minimal research evaluating the impacts of active amblyopia therapies on aphakia/pseudophakia.

Amblyopia treatment requirements vary greatly between bilateral and unilateral cases. In general, many children having bilateral surgery will not require amblyopia treatment other than refractive correction with timely updates. The diagnosis of amblyopia in bilateral cases can be difficult in this group because of the unreliability of fixation preference as a means of diagnosing amblyopia [48] until the child is old enough to respond accurately to an eye chart. On the other hand, the physician should expect that every unilateral case will have substantial amblyopia, unless there are problems with the fellow eye (e.g., optic nerve anomaly or mild cataract) and should recommend substantial amblyopia therapy over many years.

Conventional approaches to amblyopia treatment are typically employed, starting with ensuring for the proper refractive correction. For unilateral cataract, occlusion therapy begins immediately after refractive correction is placed. A commonly quoted rule for infants is 1 hour per month of age per day for up to 50% of waking hours, which is then continued for years. Many families will have difficulty adhering to this schedule, so frequent conversations with the parents should take place about the need to maintain the occlusion. In most cases, the patching will continue, but the clinician needs to assess whether the patching is causing undue stress with no evidence of im-

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Amblyopia Therapy

provement. By about 3 years of age, when the child is able to undergo optotype testing, management can be based on observed visual acuity performance. The nearly exclusive use of pharmacological penalization for children who are noncompliant with patching makes its effectiveness unknown in this situation. However, if occlusion is not possible, then it is a reasonable option for unilateral cases.

Optical penalization is an approach involving the placement of a high plus contact lens over the fellow eye, used for children with unilateral aphakia. It has been found to be as successful as patching in one small case series [49]. This approach may be feasible because the parents are familiar with contact lens use in the aphakic eye in many cases. A second use of optical penalization is for bilateral cases, in which a lens is not placed in the better eye every day, leaving the patient with very blurred and hyperopic vision at all distances in the preferred eye. Titration and monitoring of the effectiveness of the treatment should be performed, as it can be very potent and could induce a reversal of the amblyopia.

Follow-Up Care

The decision to perform lens surgery on a child is never made casually, as long-term follow-up is so intensive and is carried out over many years, with issues that extend for a lifetime. The surgeon should have the follow-up plan in place prior to surgery.

Lapses in follow-up care nearly always lead to a poor outcome. Failure leads to lost visual opportunities for the child that cannot be restored later in life.

The possibility that the one-time placement of an IOL, which is highly successful in older children, teens and adults, with consistent partial correction of the aphakia, leads to better vision 5 years after surgery with less hassle and expense, has seemed to be an obvious area of patient care improvement [50]. Testing this hypothesis has been the primary objective of the IATS, in which infants with unilateral cataract younger than 6 months of age were randomized to receive either lensectomy with contact lens correction or IOL implantation. To judge the outcomes, it is important to recall that all eligible infants had a normal posterior segment, no microphthalmos, and normal general development. These criteria ensured for a reasonably homogenous group of enrolled infants with a reasonable chance of a successful visual outcome for the testing of the study hypothesis. However, the case selection represents a best-case scenario for management of monocular infantile cataract. Thus, these outcomes may not be generalizable to all cases of monocular cataract, to patients of other ages, to eyes with anatomic abnormalities, or to infants with bilateral cataracts.

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Summary of Key Outcomes from the Infant Aphakia Treatment Study

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The primary outcome was assessed at 1 year of age, at which time there were no apparent differences in visual acuity [24]. However, intraoperative complications were 2.5 times more common in the IOL group compared with the contact lens group, illustrating the difficulty of IOL surgery in infant eyes. Much of this difficulty was related to iris prolapse or iris damage. The report on patients at 1 year of age noted that a significantly greater number of additional intraocular surgeries were required by the IOL group [24]. One surprising finding was that the contact lens group was using a contact lens for 86% of waking hours, while the pseudophakic group was using glasses for only 58% of waking hours.

The secondary outcomes of visual acuity and complications were assessed at about 5 years of age, which provided more informative results for practitioners and parents about which approach was to be preferred. Fifty-seven participants in the contact lens group and 55 in the IOL group completed visual acuity testing [25]. The median logMAR visual acuity did not differ between the treatment groups (0.90 (20/159) for both groups). More than twice as many treated eyes in the contact lens group had a visual acuity ≥20/32 [contact lens, 13 of 57 (23%); and IOL, 6 of 55 (11%)]. Unfortunately, each approach left about 50% of the children with a visual acuity of 20/200 or worse, indicating that neither of these approaches are the optimal treatment in this age group.

The IATS measured parental stress, which was surprisingly low. Nine percent of caregivers in the IOL group had a significantly elevated (above the 85th percentile) total stress score compared with 7% of those in the contact lens group [6]. These findings are at odds with an earlier report by Birch et al. [5], who found that children treated with an aphakic contact lens for monocular cataract had more treatment difficulties compared with those treated with an IOL. An important issue is the accuracy of the selected IOL. The IATS group had data for 43 eyes with a mean axial length of 18.1 ± 1.1 mm at the time of surgery [51]. The mean absolute prediction error was the smallest using the SRK/T formula (1.4 ± 1.1 D), followed by the Holladay 1 formula (1.7 ± 1.3 D). These differences seem quite small given the variability in subsequent eye growth.

Maintenance of amblyopia therapy is difficult. The IATS investigators, using parent-reported adherence and a study-specified target of 75% of prescribed patching hours, found that even during year one, this threshold was achieved by only about half of the families. By the time of the 5-year outcome assessment, only 33% of patients in the contact lens group and 15% of those in the IOL group achieved that threshold [25].

Practically, these rates likely overestimate compliance.

The diagnosis of glaucoma or suspected glaucoma 5 years after surgery was about 30%, with no difference between treatment approaches. This rate is more than double the rate of 12%, which was reported at 1 year after surgery, confirming the importance of careful follow-up monitoring of IOP and of performing optic nerve evaluations [52].

The glaucoma was open angle in most cases (19 of 20 cases, 95%), and most eyes received medication (19 of 20, 95%), while 8 of 20 eyes (40%) underwent surgery [53].

A younger (vs. older) age at surgery was associated with an increased risk of glaucoma (26 vs. 9%, respectively) (hazard ratio, 3.2; 95% CI, 1.2–8.3), and a smaller (vs. larger) corneal diameter was correlated with an increased risk of glaucoma/suspected glaucoma (hazard ratio, 2.5; 95% CI, 1.3–5.0).

The rates of additional intraocular surgeries differed significantly; at 5 years, 21% of the patients in the contact lens group and 72% of those in the IOL group had at least one surgery. Most of these surgeries were for the clearing of the visual axis. While this difference is dramatic, it will be partially offset by the expectation that some of the patients in the contact lens group will elect to undergo placement of a secondary IOL. In terms of cost, retrospective analysis was conducted based on Georgia Medicaid physician reimbursement data as well as the supplies used during the study on patients up to 5 years of age [54]. The 5-year treatment costs were similar for IOLs and contact lenses. The supplies (including glasses and contacts) were twice as expensive in the contact lens group [54]. These data did not include the substantial time lost from work by caregivers for attending frequent office visits.

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Michael X. Repka, MD, MBA Johns Hopkins University School of Medicine 600 North Wolfe Street Baltimore, MD 21287-9028 (USA) E-Mail mrepka @ jhmi.edu

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