WHATEVER HAPPENED TO?...

During the 20 years since the publication of the first issue of EuroTimes many new cataract and refractive technologies were introduced, often with much fanfare. Some of them showed promise of fulfilling unmet needs and solving long vexing problems, only to fade from the headlines, sometimes for reasons not entirely clear.

ANGLE SUPPORTED PHAKIC IOLS

Angle-supported phakic intraocular lenses (IOLs) are a technology that have gone through several iterations, with different lens designs, such as the Vivarte, the ICARE and more recently, the AcrySof Cachet lens, only to be withdrawn from the market for the same reason, excessive endothelial cell loss. This begs the question of whether it is time to abandon angle-supported IOLs altogether.

Among those who believe that is indeed the case is Michael C Knorz MD, Universitätsmedizin Mannheim, Germany, who noted that although the concept was attractive originally because the lenses were easier to implant and the lack of need for an iridectomy, they failed because of the delicate balance needed between the haptic design and intraocular anatomy.

“The problem is three-fold: first, the proximity to the corneal endothelium. If the lens is too close, there will be progressive damage. Unlike iris-supported phakic IOLs, the proximity to the endothelium varies with size – if the IOL is slightly too large, the increased compression of the haptics moves it forward, which increases the likeliness of endothelial cell loss. Second, the problem of sizing leads to varying pressure on the angle. If the pressure is too low, the IOL rotates. If it is too high, there is pupil ovalisation long-term. Third, because the IOL position is unstable in a significant percentage, a toric design is not possible,” Dr Knorz said.

He added that angle-supported phakic IOLs have lost one of their advantages over posterior chamber phakic IOLs in that the current version of the Visian Implantable Collamer Lens (ICL, Staar Surgical) no longer requires an iridectomy.

Oliver Findl MD, Hanusch Hospital, Vienna, Austria, told EuroTimes that he is also of the opinion that angle-supported phakic IOLs are finished as a concept. He added that it was out of fear of endothelial cell loss that he never implanted any of the AcrySof Cachet lenses.

FIVE-YEAR RESULTS

Thomas Kohnen MD, PhD, Goethe University, Frankfurt, Germany, takes a contrary view. He told EuroTimes that he has recently submitted a manuscript to revisions in Ophthalmology, reviewing the five-year results in 515 patients implanted with the AcrySof Cachet lens. It showed that the annualised central corneal endothelial cell loss was only 1.5 per cent, amounting to only 7.5 per cent over five years. Greater amounts of endothelial cell loss are reported in studies with the Artisan lens, he pointed out.

“From my own experience, I see my patients and the implantations we have done with the AcrySof Cachet. I am sorry that it has been withdrawn from the market. But as regards the demise of angle-supported phakic IOLs, if they aren’t on the market then nobody will be implanting them,” he added.

NOT REALLY ACCOMMODATING IOLS

Acommodating IOLs like the Crystalens (Bausch + Lomb), the HumanOptics IOL and the dual-optic Synchrony IOL promised cataract patients a reduced dependency on reading glasses, and unlike multifocal IOLs do not compromise contrast sensitivity. These lenses were designed to respond to accommodative forces of the ciliary contraction by moving the optic forward. However, several studies have failed to demonstrate that they actually provide any true accommodation.

“There isn’t any proof that any of these accommodating lenses work. In terms of the change in the axial position of the optic, the shift is very small, or even the wrong direction, and will also vary greatly between patients. There is no study that shows any actual dioptric change in refraction either,” Dr Findl told EuroTimes.

The Synchrony dual-optic IOL appeared to offer greater potential, because it required less movement of the optic to achieve an accommodative effect. Yet despite having completed a phase III FDA trial with the IOL, AMO have withdrawn the lens from the approval process.

“The Synchrony has not yet come to market and so far as I know there is a limited FDA trial and some very small case series here and there, but there is no proper randomised controlled trial that I know of that has been published. Maybe it would have worked, I don't know. But at present there is no good data in the published results,” Dr Findl said.

He noted that IOL calculation can pose a particular difficulty with the Synchrony. On the other hand these lenses also pose safety issues. For example, the Crystalens in its first designs, the AT45 and and the 5.0 had a lot of problems, such as the Z syndrome, which caused a very strong tilting of the optic in some cases. The HumanOptics 1CU had a very high posterior capsular opacification (PCO) rate and also had in-folding of their four small haptics in several cases.

Richard Packard FRCS, Prince Charles Eye Unit, Windsor, UK, told EuroTimes that the lack of function in the lens is the reason why very few ophthalmic surgeons in Europe implant them. However, he noted that the quest for a truly accommodating lens will continue until the goal has been achieved. Alcon is working with Google to help in the search for entrepreneurs to develop something which may well involve shape change of the lens and have an electronic basis.

LIGHT ADJUSTABLE LENS

Refractive surprises following cataract surgery have figured strongly as a problem in the history of IOLs and numerous features have been added to IOL design and biometric technology over the years to enhance the predictability of the procedure. In the early years of the millennium, a revolutionary concept was introduced, the light-adjustable lens (LAL, Calhoun Vision), which allowed for the postoperative adjustment of its dioptric power.

There have been a number of studies with the LAL which have shown that it enables a very considerable degree of accuracy within a quarter of a dioptre, and the lens appears close to being approved by the FDA. However, some factors may prove to be barriers to the wide use of the lens. For instance, the lens requires patients to wear special UV-blocking glasses for the weeks prior to the final lock-in of the adjusted refraction. It also requires the use of an expensive machine to perform what would be in
most cases a small amount of refractive adjustment.

“I thought the LAL was a nice concept, but it is impractical to use. First, patients have to wait too long and are inconvenienced too much by the glasses. Second, the expense of the additional procedures is too high, both regarding monetary and time requirements. I do not believe it will gain a significant market share,” said Dr Knorz.

Prof Kohnen agreed with that assessment and he pointed out that, even when the lens, the digital light delivery device and physicians experienced with the lens are available, patients still tend to find it an unappealing option. “I think this lens will fail because it's too complicated. We have access to the lens but find few patients opting for the lens,” he added.

LTK AND CONDUCTIVE KERATOPLASTY

Laser thermal keratoplasty (LTK) for hyperopia was being strongly promoted and studied 20 years ago. The technique involved the use of a holmium laser to cause a contraction of the corneal tissue to increase the curvature of the central cornea. It was followed by conductive keratoplasty, for hyperopia and presbyopia, which employed the same principle. Both techniques were granted FDA approval but both proved unsatisfactory and have now been abandoned.

“The main reason is lack of effect over time. Secondly, there were too many side effects. In all procedures which correct hyperopia, we have significant optical side effects due to the relatively small optical zone created. These side effects limit the amount of correction possible, and cause patient dissatisfaction,” said Dr Knorz.

“Another important reason is the availability of better techniques. The typical problem of the hyperopic patient is not just distance vision, but mainly near vision. None of the corneal procedures can address these two problems permanently, maybe with the exception of monovision techniques. An early cataract surgery or refractive lens exchange with a modern multifocal IOL or EDOF-IOL (extended depth of focus IOL), however, permanently solves the problem of distance and near glasses,” he added.

CORNEAL IMPLANTS FOR HYPEROPIA

Various corneal implants have come and gone over the years. The early designs, like LTK, were designed as treatments for hyperopia. However, all had biocompatibility issues and proved not to be entirely reversible, in that patients would be left with worse vision in their treated eye than they started with after the implant has been removed.

“Corneal implants that were used for hyperopia produce scarring and opacity which, of course, is unacceptable. It is also not acceptable to have inlays which when taken out still leave patients with reduced visual acuity problems,” said Prof Kohnen.

Now there are a range of new corneal inlays for presbyopia, including the KAMRA Inlay (AcuFocus), the Flexivue Microlens™ (Presbia) and the Raindrop Near Vision Inlay (Revision Optics).

Dr Knorz noted that it is still too early to say if these new inlays will stand the test of time.

“Any implant in the cornea causes some scarring long-term. That is also true for KAMRA and most likely for the other inlays. Will this affect vision? It is hard to tell but likely. What we do not know yet is how much change is acceptable. The KAMRA definitely works in most patients, and once it performs as required the effect is lasting. It remains to be seen what the long-term fate will be,” he said.

Michael C Knorz: knorz@eyes.de

Oliver Findl: oliver@findl.at

Thomas Kohnen:
kohnen@em.uni-frankfurt.de

Richard Packard:
mail@eyequack.vossnet.co.uk