Comparing Rod-Mediated Dark Adaptation in Older Adults before and after Cataract Surgery

Abstract

Purpose: Studies on age-related macular degeneration often use rod-mediated dark adaptation (RMDA) to evaluate macular functional health, studying eyes with cataract and pseudophakic eyes within the same sample. We examine a poorly understood issue-whether rod intercept time (RIT), a measure of RMDA, changes after cataract surgery and intraocular lens (IOL) insertion as compared to RIT before cataract surgery. Cataract may serve as a filter reducing photo-bleach magnitude prior to surgery, biasing RMDA interpretation.

Methods: A pre-/post-cataract surgery design was used. Persons with nuclear sclerotic and/or cortical cataract per the electronic health record were enrolled. Prior to cataract surgery, visual acuity, RMDA, and the LOCS III classification documenting cataract presence/severity were measured. Thirty days after surgery (mean), visual acuity and RMDA were repeated, followed by fundus photos to document macular health.

Results: Twenty-four participants (mean age 72.7 years, standard deviation 5.6) enrolled. All eyes had nuclear sclerotic and nuclear color cataract; 68% had cortical cataract. All IOLs were monofocal with 21 having blue blocking characteristics and 3 had clear IOLs. Most eyes had higher RIT post-surgery (15.6 min, SD 6.7) as compared to pre-surgery (13.7 min, SD 6.4), p = 0.0006, meaning that RMDA was slower post-surgery. Eyes with moderate cataract (<4 on any LOCS III grade) had RIT that increased on average by 0.7 min; those with more advanced cataract (≥4) had RIT that increased by 3.1 min (p = 0.0116). Results were unchanged when clear IOLs were removed from analysis.

Conclusion: RMDA was significantly slower (RIT was greater) following cataract surgery, with the greatest impact on RIT in older eyes after surgery for more advanced cataract. These findings suggest that persons with more advanced cataract may bias results when evaluating RMDA using RIT.

Keywords: Rod-mediated dark adaptation; cataract; cataract surgery.

Figure 1.

Examples of RIT changes comparing RMDA before cataract surgery to after cataract surgery. The top row (A and B) shows two eyes who had LOCS III grades for nuclear sclerosis, nuclear color and/or cortical < 4. The bottom row (C and D) shows two participants who had LOCS III grades for nuclear sclerosis, nuclear color and/or cortical ≥ 4. Note how the bottom row shows greater increase in RIT from pre- to post-surgery, also as depicted in Table 3.