Eyeworld

EW MEETING REPORTER 72 July 2018 Reporting from the BRASCRS annual meeting, May 16–19 São Paulo, Brazil into toric IOL calculations. He sug- gested using regression formulas or measuring using available technolo- gy. He noted the specific regression formulas available but added that it's still not possible to predictably measure the posterior cornea for individual patients. It's also important to take into account the against-the-rule (ATR) drift with age, Dr. Koch said. He sug- gested targeting a small amount of with-the-rule (WTR) astigmatism to account for the ATR shift with age. Dr. Koch said he uses relaxing incisions for less than or equal to 1.5 D WTR and less than or equal to 0.5 D ATR. For anything above that, he said a toric would be a good choice. For greater than 4 D, he does a toric first and defers relaxing incisions. Dr. Koch next stressed the im- portance of alignment. It's import- ant to know the difference that can occur between when a patient is sitting and lying down and noted that he still uses manual marking. His last tip was about prevent- ing postoperative rotation. This usu- ally occurs in the first 24 hours, and patients most at risk are those with large capsules or high myopes. To help prevent this, Dr. Koch suggested removing all OVD from behind the IOL, pushing the IOL posteriorly to "seat it," leaving the eye at a normal IOP (don't leave it overinflated), moving the eye to test meridian and also sometimes for power. He suggested looking at the patient's glasses because they can give you clues about what the total corneal astigmatism is (particularly posterior astigmatism). If there are discrepancies, remeasure or defer. Dr. Koch said that he likes to use Placido mires for all patients. This can help screen for epithelial base- ment membrane dystrophy (EBMD) and Salzmann's, and it's a good way to screen for dry eye. Dr. Koch's next tip was to be skeptical about readings because different devices may give different readings. You need more than one measurement, he said, and you need to verify the raw data. Tear film issues and cornea issues can alter measurements, as can the ability of the technician to get readings. His fifth tip was to factor in the posterior cornea. To do this, he suggested measuring the ante- rior cornea (in limited zones) and extrapolating the posterior corneal curvature. Ignoring the posterior cornea creates errors, Dr. Koch said, particularly in post-LASIK, kerato- conus, and post-PKP patients. The posterior cornea is very important for calculating total corneal astigma- tism, he added, mentioning that the posterior cornea tends to be steep vertically in most patients. Dr. Koch discussed incorporat- ing posterior corneal astigmatism Pineda said Brillouin microscopy can be used to detect subtle differences in biomechanical properties of the cornea, can factor in and measure the fact that the cornea gets stiffer with age, can be used for assessing the cornea after crosslinking, can evaluate the cornea regionally, can be used to assess after laser vision correction, and can be used to look at the crystalline lens, among other functions. In conclusion, Dr. Pineda said that corneal biomechanics are cen- tral to understanding many corneal conditions, however, better tech- nology is needed to assess corneal biomechanics. Brillouin microscopy offers the ability to measure viscoelastic properties of the cornea and lens noninvasively and tomographically, without corneal deformation. It can be used for screening patients at risk for ectasia prior to keratorefractive surgeries. Dr. Pineda added that Brillouin microscopy may prove useful for evaluating effectiveness of crosslink- ing treatments and may have a role in quantifying the impact of presby- opic therapies/interventions. Ultimately, Brillouin microsco- py could be combined with other technology as a predictive surgical planning tool, Dr. Pineda said. Astigmatism correction Douglas Koch, MD, Houston, discussed 10 tips in astigmatism correction. He questioned what the thresh- old for correction is. He said that for a monofocal IOL this threshold would be between 0.5 and 0.75 D of astigmatism, while with multifocal IOL patients, it's less than 0.5 D. Overall, more than 50% of patients are going to need astigmatism cor- rection, he said. His second tip was to "rethink your SIA." You need to know your surgically induced astigmatism (SIA), Dr. Koch said, adding that it can be calculated and is likely very small. Next, he recommended looking at three data points or more. He suggested using biometer LEDs for power/meridian and topography for View videos from the 2018 BRASCRS: EWrePlay.org Bruna Ventura, MD, discusses a technique involving partial haptic amputation for lens subluxation.

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