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Kendrick Wang, Divya Srikumaran, Albert S Jun; Intraocular Lens Power Prediction for Cataract Surgery in Eyes with Corneal Ectasia. Invest. Ophthalmol. Vis. Sci. 2019;60(9):482.
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© ARVO (1962-2015); The Authors (2016-present)
Cataract is the leading cause of vision loss. An important factor to patient outcomes after cataract extraction and intraocular lens (IOL) implantation is the calculation of IOL power. There are several mathematical formulas that estimate the IOL power for implantation based on “normal” eyes with regular corneal topography. This project examines the outcomes of cataract surgery and the accuracy of IOL power prediction in individuals with corneal ectasia, resulting in abnormal corneal topography.
This study analyzed a cohort of 46 eyes with corneal ectasia which underwent cataract surgery at a single center. Pre- and post-operative data were gathered through retrospective chart review. Eyes with a best spectacle corrected visual acuity (BSCVA) of worse than 20/40 which were excluded. The IOL power selected and refractive outcome predicted by various formulas were determined and compared to the actual post-operative refraction result.
A total of eight eyes resulted in hyperopia. Hoffer Q, SRK/T, Holladay I, SRK/II, and Barrett formulas were applied to all patients where all biometry information was available. Of the remaining eyes the predicted refraction was calculated in all cases except for four eyes where the biometry values were outside the range of calculation for the Barrett formula. The mean theoretical predicted postoperative spherical equivalent (SE) by these formulas were not statistically equal via ANOVA analysis (p<0.001). The mean absolute difference of SE predicted by the Hoffer Q, SRK/T, Holladay I, SRK/II, and Barrett formulas compared to actual postoperative SE were 0.837 (95% CI: 0.558 – 1.116), 1.021 (95% CI: 0.657 – 1.385), 0.729 (95% CI: 0.487– 0.973), 1.237 (95% CI: 0.753 – 1.721), and 0.714 (95% CI: 0.443 – 0.985) respectively. Topographic information was also obtained and will also be presented. Further, this data was utilized to put forth appropriate “adjustments” and algorithms to diminish the error between predicted and actual postoperative refraction.
Current “standard” formulas fail to accurately predict IOL power for eyes with corneal ectasia. All formulas had statistically significant absolute error compared to postoperative SE. Postoperative vision could improve with refinement of IOL formulas for eyes with abnormal corneal topography.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Table 1: Mean absolute difference and 95% confidence interval between each formula and actual postoperative SE.
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