Impact of epithelial basement membrane dystrophy and Salzmann nodular degeneration on biometry measurements

Abstract

To determine the effects of epithelial basement membrane dystrophy (EBMD) and Salzmann nodular degeneration (SND) on optical biometry measurements. Department of Ophthalmology, Duke University Eye Center, Durham, North Carolina, USA. Retrospective case series. Cataractous eyes with EBMD or SND scheduled for superficial keratectomy (SK) or phototherapeutic keratectomy (PTK) had baseline biometry. Repeat biometry was performed 30days or more postoperatively and compared with baseline. The primary outcome measures were keratometry (K) values, axial length and magnitude, and axis of corneal astigmatism. Secondary outcome measures were the change in intraocular lens (IOL) power, toricity, and axis. In the EBMD group (26 eyes), the mean absolute intersession difference showed an increase in mean K values (P<.001) and a change in IOL spherical power predicting a postoperative spherical equivalent (SE) closest to zero (P<.001) in 21 of 26 eyes (8=0.5 diopter [D]; 9=1.0 D; 4>1.0 D). In toric IOL-eligible eyes, the recommended IOL toricity changed for 16 of 24 eyes, with a mean cylinder power change of 1.2 D. In the SND group (13 eyes), the mean absolute intersession difference showed an increase in mean K values (P=.023) and a change in IOL spherical power predicting a postoperative SE closest to zero (P<.001) in 11 of 13 eyes (3=0.5 D; 3=1.0 D; 5>1.0 D). The recommended IOL toricity changed for 10 of 11 eyes (mean cylinder power change 1.5 D). Both EBMD and SND altered K measurements as evidenced by clinically significant changes in keratometry after SK or PTK. These changes affected the spherical and toric IOL power. Appropriate management of EBMD and SND before cataract surgery can yield more reliable biometric data for surgical planning.