EyeWorld Asia-Pacific September 2019 Issue

(΍HFW RI $VWLJPDWLVP LQ 7RSR JXLGHG 7UHDWPHQWV Dr. Rohit Shetty 7 *RRG XQGHUVWDQGLQJ RI F\OLQGHUV DQG G\QDPLF relationship between lens and cornea is HVVHQWLDO WR HQVXUH VXFFHVVIXO DVWLJPDWLF FRUUHFWLRQZLWK &RQWRXUD TM . In future, use of WKH =VPRGHO DQG UD\ WUDFLQJ WHFKQRORJ\ LV expected to provide further insights in topo- JXLGHG DVWLJPDWLVP WUHDWPHQW Figure 3: Galilei pie charts is a valuable tool to understand cylinders LJůŝŶĚĞƌ ǁŝƚŚ ƉƌĞĚŽŵŝŶĂŶƚ ůŽǁĞƌ ŽƌĚĞƌ ĂďĞƌƌĂƟŽŶ CASE 1 CASE 2 LJůŝŶĚĞƌ ǁŝƚŚ ƉƌĞĚŽŵŝŶĂŶƚ ŚŝŐŚĞƌ ŽƌĚĞƌ ĂďĞƌƌĂƟŽŶ custom ablation treatment (T-CAT) protocol PRGLȴHG E\ WRSRJUDSKLFDO QHXWUDOL]DWLRQ WHFKQLTXH (TNT) and refraction with WaveLight ® EX500, along ZLWK D VWDQGDUG FURVV OLQNLQJ SURWRFRO $ VLJQLȴFDQW gain in UCVA and BCVA was seen with good stability at 12-month follow-up, highlighting the ongoing improvement in patient’s vision beyond the initial laser treatment. In addition, manifest astigmatism; steepest keratometry, refractive, keratometricand topographic data reached VWDWLVWLFDO VLJQLȴFDQFH DIWHU WKH WULSOH SURFHGXUH WKXV KLJKOLJKWLQJ WKH EHQHȴFLDO H΍HFW RI FURVV OLQNLQJ LQ keratoconus patients. One of the important considerations while treating astigmatism is understanding cylinders. Cylinders are made of higher and lower order aberrations (HOA and LOA) and GALILEI pie charts are a great WRRO WR XQGHUVWDQG F\OLQGHUV )LJXUH ȊΖI WKHUH are two patients, both with high cylinders, but one has predominant astigmatism and other one predominant coma; the axis changes according to the dominance,’ explained Dr. Shetty. In case 1, when the patient has predominant astigmatism with LOA, the patient’s axis and topolyzer axis match. In this situation a WFO- ablation would result in a superior quality visual outcome. However, in case 2, where the measured D[LV DQG SDWLHQW D[LV DUH GL΍HUHQW WKH *$/Ζ/(Ζ PDS shows both astigmatism and coma. A WFO-ablation in this patient will have a residual F\OLQGHU RI FRPD DQG DVWLJPDWLVP DQG hence poor quality of vision with glass correction. “This is where Contoura TM plays an important role, where it corrects the HOA, and the resulting cylinder is predominantly 2nd order astigmatism explaining the superior quality vision”, highlighted Dr. Shetty. Another common confusion that occurs while treating astigmatism is when the patient accepts higher cylinder than that measured on topography. The reason for this confusion is explained by real- time aberrometry of lenticular astigmatism, which shows corneal astigmatism being balanced by the lens astigmatism. Prof. Shetty estimated that at least RI KLV &RQWRXUD70 SDWLHQWV KDYH LVVXHV ZLWK higher cylinders than what is seen on topography. $ PRGHO RI =ȇV FRQVLVWLQJ RI =HUQLNH S\UDPLG zero rule and lens compensation by zonules, might allow better understanding of interplay of lens and cornea. Ray tracing, a new computer- based algorithm that uses data from several GL΍HUHQW PHDVXUHPHQWV LV H[SHFWHG WR SURYLGH LQGLYLGXDOL]HG DEODWLRQ SURȴOH IRU WUHDWPHQW RI astigmatism in the near future.