Corneal epithelium: should it stay or should it go?

April 1, 2007

It has not yet been demonstrated whether riboflavin penetrates more or less with or without de-epithelialization

C3-R treatment for keratoconus, corneal ectasia and all irregular astigmatisms is a strategy that is increasingly gaining favour with many surgeons worldwide and Roberto Pinelli, MD is an enthusiastic proponent of the technique. "Thanks to the research of Professor Spoerl and Professor Seiler, this technique has been opened up to the wider surgical community and has become an important part of my institute's research and development department."

To remove or not to remove: that is the question

"I visited the Boxer Wachler Vision Institute in Los Angeles about two years ago and learnt a great deal," enthused Dr Pinelli. "I came back to Italy and began my research in this field, performing my first treatment, without removing the epithelium, in January 2006."

Dr Pinelli is President of the Italian Refractive Surgery Society (SICR), which is now conducting a multicentre study into C3-R treatment, without removal of the epithelium.

Opinions vary regarding epithelial removal during C3-R treatment; it has long been thought that removing the epithelium was necessary to improve riboflavin penetration into the stroma. However, we are beginning to see that the treatment can be just as effective, when the epithelium is left intact.

"The fact is that it has not yet been demonstrated whether riboflavin penetrates more or less with or without de-epithelialization and, above all, it has not been demonstrated how far riboflavin does actually penetrate the stroma," remarked Dr Pinelli. Here, he presents some data from his own experience in performing C3-R without epithelial removal.

Was riboflavin penetration sufficient?

In order to deduce the extent of riboflavin absorption in the presence of the epithelium we performed fluoroscopy. The riboflavin 0.1% (PriaLight, PriaVision) was applied to the cornea via a saturated Merocel sponge for five minutes prior to the start of UVA light administration. The riboflavin was then applied every three minutes during the procedure. After six minutes, the riboflavin penetrated the epithelium; after 14 minutes it penetrated the middle stroma and after 30 minutes we observed its full diffusion. Overall, the investigators found that the epithelium does not significantly restrict riboflavin absorption and penetration.

On this basis, they conducted a comparative study to evaluate the difference between C3-R with and without de-epithelialization, on patients affected by keratoconus. Both groups (group A and group B) comprised of five subjects. Group A was treated monocularly with C3-R without de-epithelialization; group B was treated in the same way but with de-epithelialization.

Prior to treatment, all patients were assessed for uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction spherical equivalent (MRSE), biomicroscopy (corneal and lens transparency), intraocular pressure (IOP), corneal computerized topographic examination (Eyesys), linear scan optical tomography (Orbscan II), endothelial cell count and ultrasound pachymetry. In addition, a questionnaire was supplied so that levels of patient satisfaction in the two groups could be monitored. All examinations were repeated at six and nine months postoperatively. Exclusion criteria included pachymetry thinner than 400 μm and aphakic eyes.

Each eye was treated with proparacaine 0.5% for 30 minutes before exposure (approximately two drops every five minutes). Riboflavin was then applied to the cornea for 25 minutes before irradiation and was then activated by a 30-minute exposure to UVA light (370 nm fluence at 3 mW/cm2). Riboflavin solution was reapplied to the cornea every three minutes during UVA irradiation.