Impact of Cataract Surgery on Rod-Mediated Dark Adaptation in Older Adults

Abstract

Purpose : There is little to no information available on the impact of phakia versus pseudophakia on the rate of rod-mediated dark adaptation (RMDA) in older adults. RMDA is increasingly used to understand the pathogenesis of AMD and considered as a potential endpoint measure in trials. There is some concern as to whether phakic and pseudophakic participants should be considered separately in studies evaluating rod intercept time (RIT), a measure of the rate of RMDA. Cataract reduces intensity and increases intraocular light scatter reaching the retina. The current analysis compares RIT in a sample of older adults before versus after cataract surgery.

Methods : Sixteen adults, ages ≥ 60 years old with nuclear sclerotic and/or cortical cataract were recruited from three cataract surgeons at UAB. One eye, scheduled for cataract surgery, was studied in each participant. Prior to surgery, RMDA was measured with the AdaptDx, and a slit-lamp photo of the cataractous lens was taken. The Lens Opacity Classification II system (LOCS II) was used by a trained, masked grader to assess the type and severity of the cataract. Approximately 2-3 weeks following surgery, RMDA was again measured. Fundus photography was performed. A trained, masked grader evaluated macular health using the AREDS 9-step classification system.

Results : Eyes had normal macular health (13), early (2) or intermediate AMD (1). Mean visual acuity improved after cataract surgery from 20/25 to 20/20, p=0.02. Mean RIT before cataract surgery was 13.2 minutes (SD 7.3), and mean RIT after cataract surgery was 14.8 minutes (SD 7.3), p=0.03. This difference is within test-retest limits of agreement for RIT. Eyes with more severe cataract (≥ 4 in LOCS II grades in nuclear opacity, nuclear color and/or cortical cataract) had greater increase in RIT post-surgery compared to those with less severe cataract (p=0.0057).

Conclusions : Considering the sample regardless of cataract severity, measuring RIT in pseudophakia provides values similar to RIT measured before cataract surgery, taking test-retest repeatability into account. However, those with more advanced cataract yielded slower RMDA (higher RIT) post-surgery as compared to eyes with mild cataract, perhaps stemming from the bleaching light being more intense after cataract removal. Results can facilitate decisions in AMD clinical trial design where RMDA is used as an outcome measure.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.