Seiler vs Holladay: the presbyopia debate

September 16, 2008

The search for a presbyopic treatment that is universally effective and universally applicable is viewed in the industry and the profession as the holy grail because of the number of people in the presbyopic age group today.

The search for a presbyopic treatment that is universally effective and universally applicable is viewed in the industry and the profession as the holy grail because of the number of people in the presbyopic age group today.

Dr Jack Holladay believes corneal inlays are that holy grail. "The results are very exciting. We are getting 20/16 at distance and 20/16 at near. Best of all, we're not affecting the mechanics of the eye or changing the cornea, and the process is completely reversible," he said.

He was speaking to delegates during the Controversies in Cataract and Refractive Surgery symposium in a debate that sought to answer the question: Presbyopia,, the multifocal cornea: corneal inlays or presbyopic LASIK?

Dr Holladay described the Acufocus corneal inlay. "It utilizes what is known as the pinhole effect which improves depth of field. It's similar to reducing your pupil down to 1.6 mm. With 0.5 D of myopia you'd have 20/16 vision at distance and 20/16 at near, due to the increased depth of field. The Acufocus corneal inlay provides that 1.6 mm aperture," he said.

He showed a series of photos where the aperture of a camera was progressively reduced to f22, with a corresponding increase in the depth of field.

"The inlay has a 1.6 mm aperture, while the outer diameter is 3.8 mm, and we put fenestrations in the polyvinyl difluoride (PVDF) annulus, which is the same material in IOL haptics.

"The thousands of fenestrations have small holes, less than 24 microns in diameter, to allow glucose, water and other metabolites to exchange freely through the annulus, without letting in light."

He said the first 41 cases in Turkey are now out for two years and "all of these patients now have 20/16 at near and distance, and are extremely happy, as is the operating surgeon, Dr Faruk Yilmez."

He said the advantage of this technique lies with the inlays, where the pinhole effect has very little impact, if any, on the cornea. "The inlay doesn't modify the optics of the eye, all we do is increase the depth of field and this appears to be a very good method of treatment," he said.

"The bottom line is that well over 95% of these Acufocus inlay patients are 20/16 at distance and near and love the effect. It's only a monocular procedure, we only do it in one eye, but that's the effect."

Dr Theo Seiler replied that when talking about multifocality or asphericity of the cornea we always think maybe we should transfer what we know about IOLs to the cornea. Of those lenses, accommodating effects cannot be applied to the cornea, and monovision is well known.

So he said he would try to transfer three IOL approaches to the cornea, enhanced depth of field (DOF), multifocal diffractive IOLs and bifocal refractive IOLs.

Two approaches for enhanced DOF are the Acufocus and the aspheric hyperprolate cornea. He said the Acufocus suffered from some disadvantages, namely low light problems, limited prospective study data and cosmetic problems. "I have heard complaints about the cosmetic impact of the Acufocus," he said.

He said excellent software exists for profiling corneal presbyopic software. If you are looking for 0.4 m focus for a 2.5 mm pupil and a 5 m focus for a 5 mm pupil, he said, the software will tell you to aim for -1.5 D in the central cornea and an asphericity constant Q of -0.7 to 0.9 or hyperprolate.

What does this look like? He said in the inner area you have 45 D on the cornea and as the diameter enlarges it jumps down to 40 D. "Centrally, you are myopic, and in the mid-periphery you are nearly a little bit hyperopic. Does this work? Yes, it does. You are looking at the cornea of my dentist," he said, prompting laughter from the audience. "He never uses reading glasses."

He said the driving force is the pupil diameter, nothing changes in the optics, just the size of the pupil. He added that miosis increases with age and so the effect should improve as the patient gets older.

He said there were disadvantages: the technique needs a good near reflex, there is limited prospective data and currently it is not a bilateral solution.

He then turned his attention to the multifocal cornea. He said due to healing, a proposed array design is currently not possible at the healing surface, but that currently localized crosslinking was under investigation.

Similarly, bifocal refractive corneal treatments are available but there is limited prospective data, it was not reversible, "and that is the main problem." Finally, he said, dissatisfaction was high with the method.

He concluded his talk by saying that there were many options for corneal presbyopic correction, but monovision is currently the only clinically accepted approach. "All the others need clinical studies for which we are eagerly waiting," he said.

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