Eyeworld

EW FEATURE 90 Corneal collagen crosslinking • September 2016 marginal degeneration is even more limited, especially given the variable progression sometimes exhibited in such patients. Anecdotal reports have found CXL is beneficial in Terrien's margin- al degeneration as long as the cornea thickness is above the range of treat- ment using the Dresden protocol, Dr. Lee said. "Our group has seen reduced astigmatism and improved flatten- ing on the cornea in anecdotal cases of radial keratotomy and Terrien's as well using an accelerated epithelial- on CXL protocol," Dr. Lee said. 2 Post-PK ectasia Dr. Trattler noted a common misun- derstanding that transplantation in keratoconus patients eradicates the disease. "You can get a recurrence of the keratoconus in eyes that have undergone a corneal transplant," Dr. Trattler said. "What you see is a pro- gressive shift in the corneal shape, the development of myopic astigma- tism, and thinning often occurs at the borders of the new graft and the original host cornea." Crosslinking can be effective in these patients, according to Dr. Trattler. Specifically, patients who have had transplants and develop ectasia in the transplant can stop the progression with CXL. Dr. Hersh said post-penetrating keratoplasty (PK) ectasia most frequently results from further progression of the keratoconus in the host cornea, rather than in the graft. The situation tends to be more prevalent with older, smaller-diame- ter grafts. "In graft eyes where the endo- thelium may be somewhat com- promised to start, I do think that crosslinking should be approached with caution, taking care not to treat corneas that are too thin," Dr. Hersh said. "In addition, the surgeon could consider treating only the inferior ectatic host area by not debriding the graft itself of epithelium before CXL." When displacing the UV light off center, additional consideration should be given to protecting the inferior limbal cells. In the future, topography-guid- ed CXL may have a place in such cases. However, that is one more area that requires further study to determine its safety and efficacy. EW References 1. Tabibian D, et al. PACK-CXL: Corneal cross-linking in infectious keratitis. Eye Vis (Lond). 2016;3:11. 2. Hafezi F, et al. Corneal collagen crosslinking for Terrien marginal degeneration. J Refract Surg. 2014;30:498–500. Editors' note: Dr. Hersh has financial interests with Avedro (Waltham, Massachusetts). Drs. Lee and Tu have no financial interests related to their comments. Dr. Trattler has financial interests with CXLO (Bethesda, Maryland). Contact information Hersh: phersh@vision-institute.com Lee: wblee@mac.com Trattler: wtrattler@gmail.com Tu: etu@uic.edu the cornea, which helps reduce the diurnal fluctuations that occur in patients with previous RK. "He found it stiffens and stabi- lizes the cornea, which is helpful," Dr. Trattler said. Unfortunately, treated patients also had a hyperopic shift from 0.5 D to 1 D. "If you have patients who have relatively good vision but are getting diurnal fluctuation in their vision, then patients have to decide if it is worthwhile undergoing the CXL procedure in light of the fact that they will become more hyperopic," Dr. Trattler said. "In patients who have some myopia to begin with, or who are hyperopic and wearing contact lenses or glasses routinely, the hyperopic shift really doesn't matter, so it would be worthwhile to undergo the procedure of cross- linking, as it can stabilize the cornea and reduce the amount of diurnal fluctuation." Terrien's benefit? Dr. Tu noted that the evidence for CXL's effectiveness in Terrien's Pushing continued from page 89

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