Eyeworld

85 November 2017 EW MEETING REPORTER Dr. Saad said the results of this and other analysis do not confirm the specificity or the sensitivity of PTA as an independent risk factor for ectasia. Topographic and tomo- graphic screening should be used to eliminate eyes with keratoconus. He also said there is a need to evaluate the utility of percent volume altered as a risk factor. IOL calculations—optimized traditional approaches vs. models developed through artificial intel- ligence pattern recognition—were presented by Thomas Olsen, MD, Aarhus, Denmark, and Warren Hill, MD, Mesa, Arizona, respectively. The original IOL power calcula- tion formulas were based on statisti- cal models and since then have been optimized by optics. Optimizing involves looking at outcomes and applying some constant toward the formula in an attempt to achieve zero prediction error. First, you need to get the true corneal power from the keratometry reading, which is very accurate with laser biometry, Dr. Olsen said. Unbi- ased measurements should be used to predict the true IOL position, and Dr. Olsen advocated for using ray tracing technology, especially in problematic eyes. Dr. Hill discussed the develop- ment of a calculator using artificial intelligence to detect patterns. the odds ratio, Dr. Santhiago said, and based on his research this ratio showed an association between PTA of 40% or more and ectasia risk. Alone, Dr. Santhiago said, PTA is not enough to evaluate a patient for LASIK risk, but it adds to a body of other risk factors. He later explained that we know there will be people with high PTA who will never devel- op ectasia—similar to how a patient with posterior capsule rupture is at higher risk for endophthalmitis but might never get endophthalmitis— but said he still considers it a viable risk factor. Dr. Saad discussed research that evaluated the sensitivity and spec- ificity of PTA in eyes with normal topography as a risk factor and, ultimately, he deemed it not a risk factor. First, to define a risk factor, you need to be able to detect it with high specificity of what is normal and what is abnormal. Dr. Santhiago's research showed 97% of patients with more than 40% PTA had a specificity of 89%. Dr. Saad added that specificity isn't enough; sensitivity is needed to determine risk, and thus, a multi- center study was conducted with 31 eyes that developed ectasia postop compared to 80 cases eyes that did not. Of the 31 ectatic eyes, 23 had normal topographies; at 40% PTA in this group, sensitivity was 47% and specificity 90%. The mean postop CSMT was found to be lowest in patients who received TA. Additionally, Dr. Wield- ers noted that the incidence of CME at 6 and 12 weeks postop was 0% in patients who received TA when measured at both of these times. Without TA, it was 7.6% at 6 weeks and 8.7% at 12 weeks. Bevacizumab had a 3.5% incidence of CME at 6 weeks and a 4.7% incidence at 12 weeks, compared to 4.3% at 6 weeks with no bevacizumab and 4.3% at 12 weeks with no bevacizumab. Dr. Wielders noted, however, that although TA can effectively reduce the risk of CME after cataract surgery in diabetics, increased IOP is a risk. The study found signifi- cantly higher IOP in patients who received TA. At 12 weeks postop, six patients in the TA group had an IOP greater than or equal to 25 mm Hg compared to zero patients with no TA. Fifteen patients in the TA group had an IOP increase greater than or equal to 5 mm Hg, compared to one patient with no TA. Dr. Wielders concluded that a single subconjunctival TA injection effectively prevents the develop- ment of CME after cataract surgery in diabetic patients. But she stressed that the risk of developing CME should be carefully weighed against the risk of developing increased IOP. Intravitreal bevacizumab had no significant effect in preventing CME after cataract surgery. JCRS symposium covers controversies The Journal of Cataract & Refractive Surgery symposium had panelists de- bating different viewpoints on three controversial topics in the field. Percent tissue altered (PTA) for predicting post-LASIK ectasia risk was discussed by Marcony Santhia- go, MD, Rio de Janeiro, Brazil, and Alain Saad, MD, Paris, France. Dr. Santhiago explained why he thinks PTA is a risk factor for corneal ectasia. PTA, by definition, is flap thickness plus ablation depth divid- ed by central corneal thickness. Dr. Santhiago discussed a case control study that showed a PTA of 40% or more was higher in a group that developed ectasia. When looking at risk factors, one needs to look at The mean CSMT was found to be the lowest in the combination treatment group. CSMT was 9.6 µm higher in the dexamethasone group at 6 weeks compared to the combination treatment group, Dr. Nuijts said. It was 6.9 µm higher in the dexameth- asone group at 6 weeks compared to the bromfenac group, and 2.7 µm higher in the bromfenac group at 6 weeks compared to the combination treatment group. Dr. Nuijts said there were similar results for other OCT parameters, and no differences in mean CDVA. Dr. Nuijts also shared the inci- dence of CME at 6 and 12 weeks. At 6 weeks postop, the bromfenac group had a 4.1% incidence of CME, compared to 8.1% in the dexa- methasone group, and 1.9% in the combination group. Meanwhile, at 12 weeks, the bromfenac group had a 4.1% incidence, the dexametha- sone group had an 8.5% incidence, and the combined group had a 2.3% incidence. He also noted the inci- dence of clinically significant CSME at 12 weeks: 3.6% in the bromfenac group, 5.1% in the dexamethasone group, and 1.5% in the combined group. In conclusion, Dr. Nuijts said CSMT was 9.6 µm higher in the dexamethasone group at 6 weeks compared to the combination treat- ment group. Patients treated with a combination of topical bromfenac 0.09% and dexamethasone 0.1% have a lower risk of developing CSME after cataract surgery com- pared to patients treated with brom- fenac or dexamethasone. Dr. Wielders shared the PREMED study results for diabetic patients. In the study, 213 diabetic patients were included, with most (about 96%) having type 2 diabetes, and 85% having no diabetic retinopathy at baseline. A 2x2 factorial design was used, Dr. Wielders said, with 60 patients in the control group, 51 patients receiving 40 mg triamcinolone acetonide (TA), 50 patients receiv- ing 1.25 mg bevacizumab, and 52 patients receiving a combination. All patients received topical bromfenac and dexamethasone. The follow-up was at 6 and 12 weeks postop. continued on page 86 View videos from ESCRS 2017: EWrePlay.org Simon Holland, MD, discusses results of a combined treatment protocol of topography-guided PRK, PTK, and CXL for keratoconus.

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