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Novel Artificial Implant Shows Promise for Corneal Oedema
Corneal oedema patients could experience shorter waiting times. Dermot McGrath reports
Anovel artificial endothelial implant may provide a safe, efficient, and cost-effective treatment modality for chronic corneal oedema and dispense the need for donor tissue in severely compromised corneas, according to Gerd Auffarth MD, PhD, FEBO.
“The results to date with this implant are very encouraging. The surgery is much easier than conventional Descemet membrane endothelial keratoplasty (DMEK), and the implant is very forgiving in terms of intraoperative handling,” he said. “We have not experienced implant-related material degradation so far. No immunosuppression is required, and the implant is “Both patients had very compromised corneas with severe effective at reducing corneal swelling and relieving the pain from pain deriving from bullous keratopathy after multiple surgeries, bullous keratopathy.” corneal decompensation, and failed DMEK. On postoperative day
The EndoArt® implant (EyeYon Medical) is embedded through one, we could see clear corneas and a marked decrease in corneal a clear corneal incision and positioned on the posterior stroma thickness,” he said, adding the follow-up on both patients is now using an air-gas mixture. over 30 months and 36 months, respectively, and the corneas
“The implant looks like a contact lens—it is dome-shaped, remain clear with no recurrence of oedema. 6.0 mm in diameter, and made of optically clear and flexible Looking at the analysis of the global data of EndoArt devices, hydrophilic material that is bio-compatible and bio-stable. It works Prof Auffarth said a total of 100 patients received implants to date by preventing the transfer of aqueous humour into the cornea, with up to 36 months follow-up. For 22 patients, the implantation thereby decreasing chronic corneal swelling,” Prof Auffarth said. was performed as part of the first-in-human study, while for Importantly, the implant allows vital nutrients to reach the cornea another 25 patients as part of the phase II study with a new on the periphery while blocking the harmful build-up of fluid in surgical protocol. the centre. Under the new protocol, 80% of 20 patients implanted needed
Prof Auffarth presented some case studies of some of the first just one rebubbling procedure or less, while 44% required patients implanted with the device in Heidelberg, Germany, zero rebubbling. in June 2019. “We have learned a lot since the first cases were performed more than two years ago. The descemetorhexis needs meticulous endothelial removal with no tags or overlapping. We know now the optimal design of the implant is the 6.5 mm model in eyes with white-to-white corneal diameter greater than 10.8 mm. Rebubbling is best performed with 10% PFP air-gas mixture. We also use a single 10/0 nylon suture and keep the patient supine for four hours postoperatively,” Prof Auffarth said, concluding the implant held a lot of promise considering the chronic shortage of donor tissue worldwide. “With a device like this, there is no waiting list or eye bank needed for human tissue. It is safe, easy to implant, and can be removed or exchanged if necessary. The costs are lower than for conventional transplants, and it is a less traumatic surgery, which is obviously appealing to the patient,” he said. “It will be interesting to see what other expanded indications might enable this implant to be used in an ambulatory day care setting.” Prof Auffarth gave this presentation at the 40th Congress of the ESCRS in Milan. Gerd Auffarth MD, PhD, FEBO is Chairman of the Department of Ophthalmology at the Heidelberg University Eye Hospital and Head of the David J Apple Center for Vision Research, Heidelberg, Germany. Gerd.Auffarth@med.uni-heidelberg.de
No Free Lunch in Optics Binkhorst Lecture focuses on compromises and challenges in optics. Dermot McGrath reports from the 39th Congress of the ESCRS in Amsterdam
Every intraocular lens designed to correct presbyopia, irrespective of its design properties and material, involves a trade-off in visual performance once implanted in the eye, said Gerd Auffarth MD, FEBO, during the The cornea, the crystalline lens, and the implanted IOL can all contribute to chromatic aberration. The type of IOL material used also plays a role in the extent of the chromatic aberration, Prof Auffarth explained. annual Binkhorst Medal Lecture.
In a wide-ranging lecture focused on the inherent compromises in multifocal and presbyopic-correcting IOLs, Professor Auffarth stressed the importance of neuroadaptation and brain function in the performance of any implanted lens, adding it was important to appreciate how intraocular lenses perform under real-life conditions once inside the eye.
“If an intraocular lens company tells you that its new lens is perfect and that everything is great, we should be immediately on our guard as the reality is a lot more complex than that—there really is no such thing as a free lunch in IOL optics,” he said.
Turning to the question of optical performance, Prof Auffarth noted presbyopia correction remains one of the greatest challenges in ophthalmology.
He said any attempt to correct presbyopia, a natural but complex process of physiological insufficiency of accommodation associated with eye ageing, needs to take due account of three interrelated concepts: visual quality, depth of field, and dysphotopsia.
“If we want to increase the depth of field, we will reduce visual quality and increase dysphotopsia. We have to play with the aberrations of the eye and other factors to maximise visual quality and balance out a certain amount of depth of focus in order to achieve our goal,” he said.
Dysphotopsias include a wide range of visual symptoms such as halos, glare, and starbursts, but not all of them are necessarily caused by the implanted IOL, he noted.
“The optics of an intraocular lens are really the reason for the halos. However, glare and starbursts can also be introduced by refractive error, defocus issues, ocular surface diseases, or other opacification in the optical pathway,” he said.
Chromatic aberration is another important influencing factor in IOL performance. It occurs when light rays pass through an optical media at different points according to their wavelength. Longitudinal chromatic aberration (LCA) causes shorter wavelengths to focus in front of longer wavelengths resulting in a difference of focus. “IOL material affects chromatic aberration and has a direct impact on it. For instance, hydrophilic IOLs have a lower LCA than hydrophobic lenses. While a refractive optic produces a given chromatic aberration, with a diffractive optic, the chromatic aberration can be manipulated and reversed to reduce the dispersion.” While this sounds beneficial in principle, the reality is LCA correction actually has a negative impact on the depth of focus in pseudophakic eyes, Prof Auffarth concluded. “Once again we are back to the reality of there being no free lunch in optics,” he said. Prof Auffarth said the variety of lenses on the market, using different optical principles, and the terminology used to describe them—enhanced monofocal, extended depth of focus (EDOF), extended range of vision (ERV), and trifocal lenses—was understandably confusing for many ophthalmologists. “These categories are overlapping and interacting, and it is really difficult sometimes to match the patient profile with the lens category being proposed,” he said. He noted that as a gen“Once again we are back to the reality of there being no free eral rule, the further one moves away from monofocal designs towards EDOF-ERV and then trifocal lenses, the greater the propensity for dysphotopsias to occur. lunch in optics.” One compelling solution to try to maximise the specific advantages of different lenses is by adopting a mix-and-match approach Prof Auffarth calls “binocular trifocal”. “We can for instance put a bifocal lens in one eye for distance and near vision, and an EDOF lens in the other eye for distance and intermediate vision. Or we can try blended vision with an EDOF lens in both eyes but use different power additions to target different distance ranges,” Prof Auffarth said. Combining different lens types in an individualised manner can achieve better binocular visual outcomes with enhanced depth of focus and reduced incidence of dysphotopsias, he concluded. Professor Auffarth is Head of the International Vision Correction Centre (IVCRC) and Director of the David J Apple International Laboratory for Ocular Pathology in Heidelberg, Germany. Gerd.Auffarth@med.uni-heidelberg.de
