EyeWorld India December 2019 Issue

42 EWAP DECEMBER 2019 REFRACTIVE by Chiles Aedam R. Samaniego Þi7œÀ` čÈ>‡*>VˆwV Senior Staff Writer Contact information Hill: …ˆJ`œV̜À‡…ˆ°Vœ“ Koch: dkoch@bcm.edu Raviv: tal.raviv.md@gmail.com This article originally appeared in the October 2019 issue of EyeWorld . It has DGGP UNKIJVN[ OQFKƂGF CPF CRRGCTU here with permission from the ASCRS Ophthalmic Services Corp. T oday, surgeons are able to achieve desired refractive outcomes with greater precision than ever before. EyeWorld corresponded with three experts on how to best utilize biometry and astigmatism management to achieve emmetropia, improving patient satisfaction and ensuring surgeons’ success in refractive cataract surgery. Biometry: Due for an upgrade? The right biometer can help better achieve desired refractive outcomes. “I think that the [two] key elements œv ÃÌ>Ìi‡œv‡Ì…i‡>ÀÌ Lˆœ“iÌÀÞ are (1) optical measurement of axial length, by optical low Vœ…iÀi˜Vi ÀiyiV̜“iÌÀÞ Q" ,R œÀ «ÀiviÀ>LÞ ÃÜi«Ì‡ÃœÕÀVi OCT, which has the advantage of being able to measure axial through much more dense cataracts than OLCR can, and (2) measurement of corneal curvature with at least 18 LEDs, preferably in more than one ring,” said Douglas Koch, MD. “Lacking these, an upgrade will dramatically improve outcomes.” The latest biometers have certainly improved keratometry readings, said Tal Raviv, MD, noting that “both the LENSTAR Q >>}‡-ÌÀiˆÌR >˜` " >ÃÌiÀ 700 [Carl Zeiss Meditec] take multiple simultaneous measurements on multiple points of the central and paracentral cornea to derive their K1 and K2.” They also indicate whether the tear w“ ˆÃ ՘ÃÌ>Li] ÀiµÕˆÀˆ˜} optimization—a critical factor for refractive outcomes. “If a surgeon is using an early generation optical biometry with old software, then moving to a newer biometer with the most recent IOL power selection methods would allow for better outcomes,” said Warren Hill, MD. The technology, however, isn’t without limitations. “No one should trust a single measurement, in my view,” Dr. Koch said. “I can cite plenty of examples where my biometer gave incorrect readings, almost always due to inaccurate corneal measurements.” As such, he recommended performing topography. “Topography is essential (1) to Vœ˜wÀ“ ̅i “iÀˆ`ˆ>˜ >˜` ̜ > lesser extent the magnitude of the astigmatism, (2) to detect abnormal topography such as keratoconus, and (3) if one has a Placido device, to evaluate the ocular surface by examining the quality of the mires,” he said. Dr. Raviv agreed that “every refractive surgeon needs topography.” He explained: “Biometers only give two Ks and a steep axis and it’s critical to see the whole picture. Is the topography regular? Irregular? Flat in one area from a small Salzmann nodule or scar or ¶ *>Vˆ`œ `ˆÃV‡L>Ãi` topographers are best in my hands for cataract purposes, ܅iÀi -V…iˆ“«yÕ} >Ài VÀˆÌˆV> for corneal refractive.” IOL power calculation and formulas Even with the best keratometers, measurements should be validated for IOL power calculations. “In general, IOL power calculations are best carried out using high quality autokeratometry with the application of validation guidelines for the ëiVˆwV ˆ˜ÃÌÀՓi˜Ì Liˆ˜} used,” Dr. Hill said. Regarding the formulas used for these Precision refractive cataract surgery Biometry, astigmatism control, and enhancements to optimize outcomes AT A GLANCE • The latest biometry devices are essential but must be validated >VVœÀ`ˆ˜} ̜ ˆ˜ÃÌÀՓi˜Ì‡Ã«iVˆwV guidelines and are best paired with topography. • The use of multiple IOL calculation formulae is recommended; the Barrett and Hill-RBF are generally acknowledged as achieving the best results. • Astigmatism control can be achieved using relaxing incisions for lower, toric IOLs for higher levels of astigmatism. • Enhancements, whether by corneal procedures or IOL exchange, require additional skills or partnering with other surgeons but are an essential component of refractive cataract surgery. Dr. Koch said the choice between an LRI or toric IOL depends on a surgeon’s “comfort level with both technologies.” LRIs (above) can be successful for low amounts of astig- matism, Dr. Hill said, but toric IOLs are preferred for 0.5 D or more of ATR astigmatism and 1 D or more of WTR. Source: Rex Hamilton, MD