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

BACKGROUND: Keratoconus (KC) is a corneal ectasia disease in which the vision of some patients cannot achieve satisfaction by spectacle corrections. However, not everyone can embrace contact lenses to achieve better vision. Perceptual learning (PL) is a potential treatment for vision improvement in such patients. PURPOSE: To investigate the effectiveness and maintenance of PL on vision improvement in KC patients corrected with spectacles. DESIGN: Randomized, double-blind clinical trial. PARTICIPANTS: Thirty-five non-progressive KC patients aged 9 years or older with unsatisfied spectacle-corrected vision were enrolled. METHODS: Non-progressive KC patients with best spectacle-corrected distance visual acuity (CDVA) of 0 to 1.0 logMAR (Snellen equivalent range 20/20 to 20/200) and 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 questionnaires were measured at baseline, 3 months, and 6 months of follow-up. Statistics were analyzed following the intention-to-treat (ITT) principle. RESULTS: 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 = 0.0006). Eight out of seventeen (47.06 %) patients in the PL group reached CDVA improvement ≥ 2 lines (P=0.0010). 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 = 0.0011). The increase of 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 = 0.009). No side effects were observed and no subjects quit because of training difficulties. CONCLUSION: Three-month perceptual learning improved vision in KC patients and the improvement maintained after 3 months of treatment cessation. The results indicate that perceptual learning may be a promising therapy for KC patients with unsatisfied spectacle-corrected visual acuity.