EyeWorld India June 2021 Issue

REFRACTIVE EWAP JUNE 2021 35 Contact information Carones: fcarones@carones.com Cummings : abc@wellingtoneyeclinic.com Reinstein : dzr@londonvisionclinic.com E pithelial thickness mapping was FDA approved in the U.S. in 2017, but awareness about its utility—and in some minds, its necessity—is growing. Three international ophthalmologists—Francesco Carones, MD, Arthur Cummings, MD, and Dan Reinstein, MD— shared their experience with the technology and offered insights on where they think it fits in ophthalmic practices now and in the future. Dr. Carones said he has been using epithelial mapping for 4 years. It’s a routine part of his practice, and he thinks it will become routine for anterior segment ophthalmology in the future. “Many anterior segment surgeons are not doing this on a routine basis yet because anterior segment OCT technology being able to map epithelial thickness became available only recently, and this kind of technology has some significant cost. We are still in that phase of early adoption where surgeons have to buy the instrument,” Dr. Carones said. Dr. Reinstein developed epithelial mapping and applications as a bioengineering research fellow working in D. Jackson Coleman’s lab with Ronald Silverman, PhD. Dr. Reinstein was the first to measure the epithelium of the cornea in vivo in 1991 using very high frequency (VHF) digital ultrasound and the first to produce a map of the epithelium in 1993. He went on to develop the first method of mapping the full epithelial The utility of epithelial mapping by Liz Hillman Editorial Co-Director This article originally appeared in the March 2021 issue of EyeWorld . It has been slightly modified and appears here with permission from the ASCRS Ophthalmic Services Corp. profile of the cornea by 1997 when he began scanning and elucidating the epithelial changes in LASIK and analyzing the complications of corneal refractive surgery. With this work and the commercialization of the first epithelial mapping device (ArcScan Insight 100 VHF and other anterior segment OCT devices with this capability), Dr. Reinstein is considered to be the “father” of this new diagnostic field of layered corneal diagnostics. “Having developed and worked with VHF digital ultrasound for 20 years prior, I was excited to help Optovue develop the first OCT prototype device to map the corneal epithelium in 2012 and commercially launched in 2015. Most anterior segment OCT manufacturers are now developing this capability for their devices,” Dr. Reinstein said. “This is becoming the standard of care for refractive surgery diagnostics.” Dr. Carones described epithelial mapping as a diagnostic and screening tool that can help ensure the right treatment is pursued in certain cases. It’s first important to understand what a normal epithelial map looks like so it can be used as a baseline for comparison. Dr. Reinstein and colleagues published in 2008 that normal epithelium was 5.7 μm thicker inferiorly than superiorly and 1.2 μm thicker nasally than temporally. 1 The mean central thickness was 53.4 μm. According to Dr. Reinstein’s work, the average central epithelial thickness was 53.4 μm with a standard deviation of 4.6 μm. “This indicated that there was little variation in central epithelial thickness in the population,” he said. “The thinnest epithelial point within the central 5 mm of the cornea was displaced on average 0.33 mm (±1.08) temporally and 0.90 mm (±0.96) superiorly with reference to the corneal vertex. Studies using OCT have confirmed this superior-inferior and nasal-temporal asymmetric profile for epithelial thickness in normal eyes.” 2 Dr. Reinstein first postulated in 1994 that this inferior/ superior asymmetry is produced by the balance of forces of epithelial outward growth and the combined inward forces produced by the eyelids, the upper eyelid producing more inward force than the lower lid, he explained. 3 A diagnostic and screening tool Epithelial mapping has been described by Dr. Reinstein and colleagues as a very sensitive and specific method to detect keratoconus even earlier than topographic and tomographic devices. 4 “If the keratoconus is early enough, it cannot be detected on topography or tomography,” Dr. Cummings said. “If the epithelial maps show a thinning of the epithelium, however, that would indicate that the stroma beneath the thinned epithelium may be bulging or ectatic. The