Delta Journal of Ophthalmology (Jan 2022)
Accuracy of intraocular lens power calculation using Scheimpflug tomography and OKULIX ray-tracing software in paracentral corneal scarring not interfering with postoperative refraction
Abstract
Purpose The aim of this study was to evaluate the accuracy of intraocular lens (IOL) power calculation using Scheimpflug tomography and OKULIX ray-tracing software in cases of paracentral corneal scarring. Patients and methods The study was conducted on 40 consecutive eyes: 20 with corneal scarring and coexisting cataract and 20 controls with clear cornea, for whom uneventful phacoemulsification and IOL implantation was performed. Preoperatively, Scheimpflug tomography and OKULIX ray-tracing software and third-generation IOL power calculation formulas were used for IOL power calculation. Accuracy of IOL power calculation was evaluated by subtracting the expected and achieved spherical refraction, 3 months postoperatively and was recorded as the mean absolute error (MAE). The distance uncorrected visual acuity for each eye was measured preoperatively and 3 months postoperatively; the visual acuity was scored and converted to the logarithm of the minimum angle of resolution (LogMar) for statistical analysis. Results In cases of corneal scarring, all eyes (100%) yielded a postoperative spherical refraction which differed by less than 1 D from the predicted. In 16 (80%) eyes, the postoperative spherical refraction was within 0.50 D from the expected. The MAE was 0.2 D in cases of corneal scarring, which did not differ significantly from the controls (MAE=0.1 D), P=0.142. In corneal scarring cases, the distance uncorrected visual acuity showed significant improvement from 1.3 LogMar (Snellen’s equivalent 20/400), preoperatively, to 0.5 LogMar (Snellen’s equivalent 20/60), 3 months postoperatively. Conclusion Scheimpflug tomography combined with OKULIX ray-tracing software for the calculation of IOL power provided accurate results in cases of corneal scarring.
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