Impact of Cataract Surgery on Low Luminance Visual Acuity Deficit Measurements

PURPOSE: The impact of cataract surgery on low luminance visual acuity deficit (LLVAD) measurements was investigated by measuring the LLVAD before and after cataract surgery. DESIGN: Prospective, longitudinal study. PARTICIPANTS: Patients undergoing cataract surgery. METHODS: Photopic luminance (PL)–best-corrected visual acuity (BCVA) and low luminance (LL)–BCVA were obtained using the ETDRS chart. Low luminance visual acuity deficit scores were calculated by subtracting the LL-BCVA letter score from the PL-BCVA letter score. To demonstrate the reproducibility of these visual acuity measurements, we used data from drusen-only eyes previously published in the Complement Inhibition with Eculizumab for the Treatment of Nonexudative Age-Related Macular Degeneration (COMPLETE) study. The PL-BCVA, LL-BCVA, and LLVAD measurements obtained at an interval of 3 months in this cohort were used for comparison. In the current study, the impact of cataract surgery on LLVAD measurements was analyzed by comparing the PL-BCVA, LL-BCVA, and LLVAD measurements before and after cataract surgery. MAIN OUTCOME MEASURES: The reproducibility of the visual acuity measurements and the changes in LLVAD measurement after cataract surgery. RESULTS: In the COMPLETE study, no clinically significant differences were found in the PL-BCVA, LL-BCVA, or LLVAD measurements between baseline and the 3-month follow-up visits with a change of –1.1 letters, –1.3 letters, and 0.1 letters, respectively (P = 0.02, P = 0.11, and P = 0.88, respectively). In the current study, significant increases were found in the PL-BCVA and LL-BCVA measurements, with a change of 7.3 letters and 10.2 letters after cataract surgery (P < 0.001 for both), and a statistically significant decrease in LLVAD measurements was found, with a change of –3.0 letters after cataract surgery (P = 0.002). CONCLUSIONS: Because of the variable effect of cataracts on LL-BCVA measurements and the significant change in LLVAD measurements after cataract surgery, investigators should be aware that cataract surgery during a trial will have an unpredictable impact on LLVAD measurements, and pseudophakic and phakic patients should be analyzed separately.