Eyeworld

76 | EYEWORLD | SPRING 2024 R EFRACTIVE by Liz Hillman Editorial Co-Director About the physicians Scott D. Barnes, MD Chief Medical Officer, STAAR Surgical Colonel (retired), U.S. Army Womack Army Medical Center Fort Bragg, North Carolina New York, New York, Erik Mertens, MD, FEBOphth Medical Director Medipolis Antwerp, Belgium Audrey Rostov, MD Cornea, Cataract, and Refractive Surgeon Seattle, Washington William Trattler, MD Director of Cornea Center for Excellence in Eye Care Miami, Florida Blake Williamson, MD Williamson Eye Center Baton Rouge, Louisiana Clearing up the confusion: get the right anterior chamber depth for ICL A mong the important indications for use of the EVO ICL (STAAR Sur- gical)—age, amount of myopia, astigmatism correction, etc.—there is one parameter that some surgeons say could be causing confusion. "Yes, I do think there can be some confu- sion," Audrey Rostov, MD, said. "Yes, absolutely. It's confusing," William Trattler, MD, said. "100% agree ... there is significant confu- sion," Scott D. Barnes, MD, said. The FDA's indication specifies that the EVO ICL should be used in patients "with an anterior chamber depth of 3.0 mm or greater." It further defines this as "when measured from the cor- neal endothelium to the anterior surface of the crystalline lens." "There is confusion because nobody agrees on what the term 'anterior chamber depth' really means. Does it include the epithelium or is it measured just from the endothelium? De- pending on which textbook and which literature report you look at, it may say anterior chamber depth is measured from the endothelium," Dr. Barnes said, adding later that some instru- ments report ACD from epithelium to anterior capsule and others have the ability to subtract the cornea and report the measurement from the endothelium or both. "Yes, absolutely there is confusion on it, and some instruments cannot separate that out and they just record ACD. Some instruments separate it out and report ACD endo vs. ACD epi (as with Orbscan); others report ACD internal vs. external, as with Penta- cam where "ext" includes the corneal thickness and "int" is from the endothelium. Some others will also display AQD or AD, meaning 'aque- ous depth,' which means the ACD without the corneal thickness. … You have to know your machines and what they're reporting." Dr. Rostov said similar. In terms of sizing for the ICL, she said, "it's important to know that you should be measuring from the endotheli- um, not the epithelium. You want to make sure about this because otherwise you could choose the wrong size lens or you may not even have enough anterior chamber depth to permit use of the ICL." Dr. Rostov said she uses Pentacam (Ocu- lus) to measure anterior chamber depth from the endothelium as well as white to white. If a surgeon is using biometry for these measure- ments, like the IOLMaster (Carl Zeiss Meditec), improper sizing could occur. Dr. Rostov has found that white to white measurements with biometers is generally larger. With Pentacam, Dr. Rostov said she can set it to measure from endothelium (internal). If you were to use a device that measures from the epithelium (external cornea), you need to subtract out the pachymetry of the cornea, she said. "The reason this is important is you want to make sure you get right sizing of ICL," Dr. Rostov said. "If you put in ICL and you don't have enough anterior chamber depth, you could get narrowing of anterior chamber. The vault of the ICL could be too high. In a shallow anterior chamber, you have the potential for angle clo- sure glaucoma. Make sure you have enough AC depth. Strict on-label use of the ICL is a 3-mm anterior chamber depth as measured from the endothelium." Dr. Trattler says with use of the LASSO formula he has felt comfortable implanting ICLs in patients below the 3.0 mm, on-label ACD indication. Source: William Trattler, MD continued on page 78

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