The right mix: keratoconus treatments

Intacs in the eye.

ntacs in the cornea.
Source: Addition Technology Inc.

Lamella layer of the cornea.
Source: Addition Technology, Inc.

Keratoconus treatment options way beyond contacts and glasses—and even penetrating keratoplasty in advanced stages of disease—are now available in various forms. Recently, clinical use of Intacs (Addition Technology, Des Plaines, Ill.) has met with success, as has corneal cross-linking. But the treatment intersection of Intacs and transepithelial cross-linking (CXL) has been marked by some controversy. If you believe some research, Intacs is good, Intacs plus CXL is better, and CXL alone is best. Other research finds differently. A recent study, published in the August 2009 issue of Cornea, explains the controversial research well and adds its own conclusions to the mix. That study finds that CXL does enhance Intacs cases in certain ways, detracts in others, but generally may not be as good as CXL alone (or even as good as results with CXL and Intacs in other studies).
Searching for the right mix

Aylin Ertan, M.D., Department of Cataract and Refractive Surgery, Kudret Eye Hospital, Ankara, Turkey, and colleagues began their research by studying 25 eyes of 17 bilateral keratoconus patients who underwent Intacs implantation. The same eyes subsequently underwent CXL. The mean time between Intacs implantation and CXL treatment was 3.98 months. “CXL after Intacs resulted in an additional improvement in UCVA, BCVA, sphere, cylinder, and keratometry,” Dr. Ertan reported. In particular: • Vision improved by 1.9 Snellen lines of UCVA after Intacs and by 1.2 Snellen lines additionally after CXL.
• BCVA also improved by 1.7 Snellen lines after Intacs and by 0.36 Snellen lines additionally after CXL.
• Spherical, cylindrical, mean K, and steepest K values decreased by 2.08 D, 0.47 D, 2.22 D, and 1.27 D, respectively, after Intacs treatment. • The same values decreased by 0.5 D, 0.15 D, 0.35 D, and 0.76 D, respectively, after CXL.
“In our study, treating keratoconus with Intacs followed by CXL resulted in more regular topography with visual improvement,” Dr. Ertan reported. owever, the results weren’t altogether stunning.
“In our hands, CXL treatment after Intacs was not as effective on mean K values and on manifest refraction as compared with previous studies,” Dr. Ertan reported. Changes in sphere and cylinder after CXL were not statistically significant.
CXL is carried out by using UV-A and riboflavin, a photosensitizer, to stiffen the cornea, Dr. Ertan noted. Other research findings in favor of CXL plus Intacs (instead of Intacs alone) posited that the better combined result instead of Intacs alone could arise from “biomechanical coupling from local collagen changes around the segments,” Dr. Ertan reported. The combination might be better than Intacs only, but not CXL only. “Our improvement in refractive and topographic results with Intacs and CXL are not as favorable as those reported with CXL treatment alone,” Dr. Ertan found. “In our study, UCVA improved by 1.2 lines and mean K value decreased by 0.35 D, 2 months after CXL treatment. [Other CXL only research] showed a mean K reduction of 2.1 D, which is more than our result when we compare only CXL treatment change.”
Of course, there are safety considerations at play with cross-linking treatment. Some case reports suggest a possible link between cross-linking and DLK, as well as reactivating herpetic keratitis. While UV radiation should be below harmful levels, harmful consequences of its usage are possible. “Cross-linking with the epithelium removed versus transepithelial treatment is another controversial issue,” Dr. Ertan noted. “Applied riboflavin must diffuse into the corneal stroma for treatment efficiency. The intact epithelium is a barrier that slows the absorption of riboflavin into the cornea so it penetrates slowly and incompletely. Cross-linking treatment without removing epithelium causes inadequate penetration of riboflavin and therefore enhances UV penetration and results in possible cell damage.”

Eager to learn

John D. Sheppard, M.D., professor of ophthalmology, microbiology, and immunology, Eastern Virginia Medical School, Norfolk, Va., said he would love to perform cross-linking. “You have to be associated with a research center to do that, but it is becoming the standard of care for select people,” Dr. Sheppard said. Dr. Sheppard, who has referred several patients to Emory University’s Atlanta facilities for cross-linking, has also performed Intacs implantations, but with reservations. “I don’t like Intacs,” Dr. Sheppard said. “I have used them for keratoconus. You get great results in some patients and no results in others. Insurance often doesn’t pay for these procedures.” There are other options for some patients with keratoconus—even glasses. “I have a couple people in glasses with non-cicatricial keratoconus,” Dr. Sheppard said. More advanced cases of keratoconus include scarring of the cornea, and that’s when surgery becomes necessary, he said.

Editors’ note: Dr. Ertan has no financial interests related to this study. Dr. Sheppard has no financial interests related to his comments.

Contact information

Ertan: aylinclzy@gmail.com
Sheppard: 757-622-2200, docshep@hotmail.com