Eyeworld

37 EW CORNEA June 2017 corrected visual acuity, even with one topography or Pentacam image that showed changes consistent with keratoconus, a surgeon could feel justified in recommending early crosslinking without long-term eval- uation to reduce risk of progression and thus reduce risk of losing the ability to maximize best corrected vision. As for cases of post-refractive surgery corneal ectasia, age is not so much a factor for monitoring progression as these cases are more unpredictable, Dr. Kanellopoulos said. He added that in his prac- tice the most sensitive criteria for evaluating a patient with corneal ectasia is looking at corneal epithe- lium maps obtained with anterior segment OCT. Dr. Kanellopoulos warned that detection of keratoconus can be masked by epithelium remodeling, which is why he advises epithelium mapping. If it is unavailable, he ad- vised looking at topographic maps, not just keratometries, and looking at the steepest part of the cornea. "An increase in the index of height decentration seems to be the most sensitive proof for the diagnosis of keratoconus with the exception of the central 'nipple' cones," he said. The current, on-label procedure for crosslinking in the U.S. requires epithelial debridement and a corneal thickness of 400 µm after this pro- cedure. The cornea (as thick as 350 µm) can be swelled up to 50 µm us- ing a hypotonic riboflavin solution, to allow for safe crosslinking. "Patients who have very thin corneas are not candidates, and I have seen cases of damage to the endothelium from crosslinking performed on a thin cornea," Dr. Raizman said. There are different epithelial debridement techniques, and Dr. Raizman said each is effective and depends on the physician's pref- erence. Dr. Raizman uses a round blade and removes the epithelium in a manner similar to what is done for PRK. Dr. Hersh uses 20% alcohol in either a 9-mm birdbath or a 9-mm cellulose sponge. Drs. Greenwood and Swan also said they use dilute alcohol to perform a superficial corneal topography as well as simu- lated K readings. Dr. Hersh, medical monitor for the FDA crosslinking trials, 1 acknowledged that this informa- tion might not be available for all patients due to a lack of past corneal topographies or use of different de- vices, making it difficult to compare measurements. As such, it's import- ant to take the patient's subjective visual history (e.g., "Has your vision been getting worse over time?") and the actual change in refraction. If a medical record of refraction over time is not available, Dr. Hersh said looking at the patient's old glasses can be helpful. "Increase in myopia or partic- ularly an increase in astigmatism is another indication of progression," he said. Age is also a factor in determin- ing when to offer crosslinking. In younger patients—those 15 to 25 years old—A. John Kanellopoulos, MD, clinical professor of ophthal- mology, New York University Med- ical School, New York, and medical director, Laservision.gr Institute, Athens, Greece, said keratoconus is more unpredictable and thus requires close follow-up, every 3 months, to document progression. Dr. Kanellopoulos said while topog- raphy is helpful for tracking progres- sion, he noted research that suggests the most sensitive metric is the in- dex of height decentration, which is available on most Pentacam (Oculus, Arlington, Washington) and Placido disc topographies. 2 From 25 to 35 years old, Dr. Kanellopoulos said ker- atoconus patients become less prone to abrupt, unexpected changes and could be followed up with every 6 months to a year. Similarly, kerato- conus progression becomes even less likely at 35 and older. "Nevertheless, we've seen changes in patients in their 50s, 60s, and 70s. Although an exception, one cannot exclude any progression of keratoconus while the patient's age advances," Dr. Kanellopoulos said. Russell Swan, MD, in fellow- ship, Vance Thompson Vision, Sioux Falls, South Dakota, echoed a similar sentiment, saying that if a younger keratoconus suspect was referred with documented increasing astigmatism or degradation in best A F R E S H P E R S P E C T I V E ™ © 2017 Lacrivera, a division of Stephens Instruments. All rights reserved. lacrivera.com ( 855 ) 857-0518 dryness fatigue redness sorie redness irritation ijouble vision pain irritation burning dry itching dryness redness sore tired gritty pain irritation dry vision sensitivity foreign body sensation dryness redness sore tired pain irritation burning dry itching sensitivity foreign body sensation eysandy fatigue redness eye tired irritation sore tired pain excess watering gritty sensitivity foreign body sensation itching burning gritty excess Your LASIK results speak for themselves. Don't let post-op dry eye talk over them. Fight post-op dry eye with the VeraPlug ™ and let your patients enjoy the enhanced visual acuity they expect from day one. VeraPlug. ™ For healthier, happier patients. continued on page 40

• Blank Page
• Blank Page (1)