EyeWorld India December 2019 Issue

EWAP DECEMBER 2019 43 REFRACTIVE calculations, he recommends the >ÀÀiÌÌ >˜` ˆ‡, vœÀ“Տ>ð Dr. Raviv agreed, noting “the published literature has demonstrated the superiority of >ÀÀiÌÌ 1˜ˆÛiÀÃ> >˜` ˆ‡, over all older formulas.” 1,2 The Barrett formulas—with Û>Àˆ>˜Ìà vœÀ «œÃ̇ Ƃ- É*, É, cases and for toric IOLs—were created by Graham Barrett, MD, and are available on the ASCRS website at >ÃVÀðœÀ}ÉL>ÀÀiÌ̇ ̜ÀˆV‡V>VՏ>̜À , among other websites. i>˜Ü…ˆi] ̅i ˆ‡, Calculator is available via rbfcalculator.com , where it is `iÃVÀˆLi` >à º>˜ >`Û>˜Vi`] Ãiv‡ validating method for IOL power selection employing pattern recognition and sophisticated data interpolation.” “The current version 2.0 is based on 12,419 implantations,” Dr. Hill said. “This works for biconvex and meniscus IOLs from +32.00 D `œÜ˜ ̜ qx°ää ° “As the database increases in size, the depth and accuracy œv ̅i ˆ‡, “i̅œ` ܈ advance,” he added. “Version 3.0, which will be released in the future, will add lens thickness, ܅ˆÌi‡Ìœ‡Ü…ˆÌi >˜` ̅i Vi˜ÌÀ> corneal thickness as input parameters. I anticipate that the calculation range for version 3.0 will be the same as for version 2.0.” /…i ˆ‡, >À̈wVˆ> intelligence calculator is licensed ̜ >>}‡-ÌÀiˆÌ >˜` œ«Ìˆ“ˆâi` vœÀ use with the LENSTAR LS 900. Dr. Koch recommends these formulas but makes allowances for surgeon experience. “I think that ophthalmologists should T o further enhance one’s refractive outcomes for cataract surgery, I cannot emphasize more on the importance of audit and data analysis of one’s surgical outcomes. As surgeons, we tend to remember our patients who turn out plano rather than those who missed their refractive targets. Without detailed postoperative analysis, opportunities for improvement are inevitably lost. User Group for Laser Interference Biometry (ULIB) intraocular lens (IOL) constants are good starting values for surgery. However, after collecting surgical data of a fair number of patients (50 cases), we can start IOL constant optimization. Optimization eliminates systematic errors inherent in the surgical process, from biometry measurements to surgery to refraction. With modern small incision «…>Vœi“ՏÈwV>̈œ˜] ÃÕÀ}iœ˜ v>V̜Àà >Ài ÕÃÕ>Þ ˜œÌ ̅i “>ˆ˜ V>ÕÃi for any deviation of lens constants. The type of biometer, how measurements are taken, and how refraction is performed have greater impact. That is why personalizing lens constant for a particular practice would improve refractive outcomes. Data required for optimization would be the preoperative biometric measurements, IOL model and power, and postoperative manifest refraction. Postoperative refraction should be performed at least 1 month after surgery, and optimization should be done separately for different biometers. Electronic medical records (EMR) are very useful in data retrieval and can greatly reduce the time and ivvœÀÌ ˜ii`i`° œÃÌ “œ`iÀ˜ Lˆœ“iÌiÀÅ>Ûi LՈÌ‡ˆ˜ " Vœ˜ÃÌ>˜Ì optimization capabilities in which the machine can automatically calculate the optimized IOL constant after the postoperative ÀivÀ>V̈œ˜ ˆÃ i˜ÌiÀi`° Ƃ˜ >ÌiÀ˜>̈Ûi ܜՏ` Li Ãiv‡«Àœ}À>““ˆ˜} œv known, published IOL formulas on Excel spreadsheets (e.g. Holladay ] -, É/®] >˜` L>VŽ‡V>VՏ>̈˜} ̅i " Vœ˜ÃÌ>˜Ìà ̜ >ÌÌ>ˆ˜ > “i>˜ predictive error of zero. Care must be taken for the latter option to ensure the formula is accurately replicated on Excel. For new, unpublished formulas such as the Barrett Universal II, optimization would require the biometer as they cannot be programmed onto Excel on our own. Apart from reducing systematic errors, optimization is also necessary for any comparison of the predictive accuracies of different formulas. The surgeon can then determine which formula provided him or her the best outcomes for different types of eyes and IOLs. Therefore, optimization and data analysis are crucial steps in raising our performance, to provide the most accurate refractive outcomes for our patients. 'FKVQTUo PQVG &T ;GQ FGENCTGF PQ TGNGXCPV ƂPCPEKCN KPVGTGUVU Tun Kuan Yeo, MD Department of Ophthalmology, Tan Tock Seng Hospital 11 Jalan Tock Seng, Singapore 308433 tun_kuan_yeo@ttsh.com.sg ASIA-PACIFIC PERSPECTIVES use formulas that they have optimized with their experience, if they have tracked their outcomes, PLUS one or more of the newer or more sophisticated formulas: Barrett Universal II, ˆ‡, ] œ>`>Þ Ó] >˜` "Ãi˜]» he said. “These latter [four] are typically going to outperform older formulas in eyes at the extremes: short/long axial length, shallow anterior chamber, unusual corneal power.” Dr. Raviv cited the Ladas Super Formula (LSF) as “promising, but more data is forthcoming.” Initially developed by John Ladas, MD, the current iteration, according to the website (iolcalc.com ), improves on the original LSF “using two major studies of more than 4,000 eyes” and introduced >À̈wVˆ> ˆ˜Ìiˆ}i˜Vi ºÌœ ˆ“«ÀœÛi performance and harness the power of machine learning.” Astigmatism control Astigmatism control can spell the `ˆvviÀi˜Vi LiÌÜii˜ > Ã>̈Ãwi` >˜` >˜ ՘Ã>̈Ãwi` «>̈i˜Ì° Surgeons can opt for either relaxing incisions or a toric IOL. “LRIs can be successfully used for low amounts of astigmatism. In our practice, we sometimes ÕÃi vi“ÌœÃiVœ˜` >ÃiÀ‡>ÃÈÃÌi` AKs for small amounts of astigmatism,” Dr. Hill wrote. “However, we prefer toric IOL placement for ATR astigmatism of 0.50 D or more and WTR astigmatism of 1.00 D or more.” Generally, Dr. Raviv prefers toric IOLs. “Studies that compare relaxing incisions to toric IOLs show a greater