Abstract
Purpose :
To assess the impact of total keratometry (TK) and the accuracy of newer formulas on intraocular lens (IOL) power calculation for individuals with prior radial keratotomy (RK).
Methods :
Retrospective review of patients with prior RK who underwent cataract extraction and IOL implantation between 2019 and 2023 at the Bascom Palmer Eye Institute and Dean McGee Eye Institute. Inclusion criteria were availability of TK values from an IOL Master 700, refraction performed 45 to 180 days post-operatively, and best corrected visual acuity of 20/50 or better. Eyes were excluded if they had complicated cataract surgery, prior vitrectomy, vision limiting pathologies, or mean keratometry (Km) greater than 47 D. A-constants were found via IOLCon and ULIB. Refractions predicted by formulas using predicted (K) and measured (PK) posterior keratometry and using the double K method (DK) were compared to post-operative refractions.
Results :
109 eyes from 82 patients were included. Mean age was 69 years ± 7.20 and 39.02% (n=32) were male. 12.84% (n=14) of eyes had 4 RK incisions, 55.05% (n=60) of eyes had 8 RK incisions, and 10.09% (n=11) of eyes had 16 RK incisions. The average Km was 38.91 D ± 3.49. Post RK formulas (Barrett True K NH, Barrett True K TK, DK Holladay 1 (IOLMaster/Lenstar), DK SRK, Pearl DGS post RK) and standard formulas with TK (Barrett Universal 2.0 TK, Cooke K6 TK, EVO 2.0 TK, Hoffer QST TK, SRK/T TK, Holladay I TK) were ranked by root mean square error. Primary outcomes were median absolute error and percentage of eyes with postoperative refractive error within 0.5 and 1.0D.
Conclusions :
Eyes with prior RK continue to cause refractive surprises after cataract surgery. To our knowledge, this study provides the largest dataset of post-RK eyes assessed for IOL predictions and is the first to evaluate the impact of total keratometry on the performance of post-refractive and non-refractive formulas.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.