Novel Method of IOL Power Calculation Using Scanning-Slit Topography–Based Keratometry in Myopic LASIK Cataract Surgery Patients: Retrospective Study
To evaluate a novel method for calculating intraocular lens power after myopic LASIK using orbscan total mean and optical power values and to compare it with IOL master and Manual keratometry methods.
This retrospective study comprised 12 eyes of 10 patients who had phacoemulsification with IOL implantation after myopic LASIK using Orbscan total mean and optical power values at 1.5 mm for IOL power calculation using SRK T & SRK 2 formulae. The topography based powers and the IOL master and manual keratometric values were compared. The expected residual spherical equivalents for the implanted IOL power with various formulae like SRK T, SRK 2, Haigis & Holiday 2 using orbscan based powers, IOL master and manual keratometric values were calculated individually and compared with the achieved residual spherical equivalents.
There was significant difference in K1 values between IOL Master Vs Orbscan, IOL Master Vs Manual K and Orbscan Vs Manual K with P value of 0.0076, 0.0206 and 0.0037 respectively and also in K2 values between IOL Master Vs Orbscan, Orbscan Vs Manual K with P value of 0.0022 and 0.0047 respectively though there was no difference between the IOL master and manual methods for K2 values(p value 0.5560). Mean(SD) of achieved residual spherical equivalent is 0.77(1.19). Orbscan based powers with SRK T mean(SD) expected residual spherical equivalent was -0.35(0.67)(P= 0.754).
Orbscan based total mean and optical power values in SRK T formulae are more reliable than the IOL master or Manual keratometry values in post myopic LASIK patients for IOL power calculation.