Vision Improvement in Keratoconus Patients Trained With Perceptual Learning: A Randomized Controlled Trial

To investigate the effectiveness and maintenance of perceptional learning (PL) on vision improvement in keratoconus (KC) patients corrected with spectacles. Randomized, double-blind clinical trial. Non-progressive KC patients 9 years of age or older who had best spectacle-corrected distance visual acuity (CDVA) of 0 to 1.0 logMAR (Snellen equivalent range 20/20 to 20/200) and who were contact lenses intolerant were enrolled. Eligible subjects were randomized into PL and control groups to receive PL and placebo training for 3 months, respectively. Spectacle-corrected visual acuity, contrast sensitivity function (CSF), stereoacuity, and visual functioning and quality of life were measured at baseline, 3 months, and 6 months of follow-up. Statistics were analyzed following the intention-to-treat principle. After 3 months of training, the CDVA of patients in the PL group improved as compared to the placebo group (0.17 ± 0.15 logMAR vs 0.02 ± 0.06 logMAR; P = .0006). Eight of 17 (47.06%) patients in the PL group reached CDVA improvement ≥2 lines (P = .0010). This improvement persisted for at least 6 months (from baseline) as compared to the placebo group (0.17 ± 0.17 logMAR vs 0.01 ± 0.07 logMAR; P = .0011). The increase in CSF in the PL group mainly was found for moderate spatial frequency (0.11 ± 0.17 log units at 3 cpd; 0.12 ± 0.19 log units at 6 cpd). Linear regression indicated that patients with worse initial CDVA achieved better gains in CDVA after PL (P = .009). No side effects were observed, and no subjects withdrew from the study because of training difficulties. Three-month PL improved vision in KC patients, and the improvement was maintained after 3 months of treatment cessation. The results indicate that PL may be a promising therapy for KC patients with unsatisfied spectacle-corrected visual acuity.