A contra-lateral comparison of the visual effects of a photochromic vs. non-photochromic contact lens

• Published in: Contact lens & anterior eye Vol. 43; no. 3; pp. 250 - 255
• Main Authors: Renzi-Hammond, Lisa, Buch, John R., Cannon, Jessica, Hacker, Lauren, Toubouti, Youssef, Hammond, Billy R.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.06.2020
• Subjects: Chromatic contrast; Glare; Photochromic lenses; Photostress recovery; Chromatic contrast; Photochromic lenses; Glare; Photostress recovery
• ISSN: 1367-0484; 1476-5411; 1476-5411
• DOI: 10.1016/j.clae.2019.10.138

•Photochromic contact lenses can adapt their level of light filtration to the viewer’s viewing conditions.•In this study, we tested a photochromic contact lens against a non-photochromic lens using ecologically relevant stimuli.•The photochromic lens significantly improved vision under glare and photostress conditions and reduced glare discomfort.•The photochromic lens improved chromatic contrast sensitivity but did not improve vernier acuity.•Photochromic contact lenses improve visual function in conditions designed to match a variety of outdoor viewing conditions. To compare the effects of a photochromic contact lens vs. a non-photochromic control lens on visual function. A subject-masked, prospective contralateral eye design was used. Sixty-one subjects were enroled based on age (using a 2:1 allocation ratio for ages 18–39 and 40–65 years, respectively). The study lenses were senofilcon A with photochromic additive (Test) that filtered over the entire lens, compared to a non-photochromic Control with no tint. The Test lens was partially activated during testing with a steady-state transmittance of approximately 62%. Eligible subjects were tested using both study lenses, with Test and Control lens randomized by eye. Five visual function outcomes were tested: photostress recovery (PSR), glare disability (GD), glare discomfort (GDC), chromatic contrast (CC) and vernier acuity (VA). Iris colour and macular pigment density were assessed as control variables. PSR was measured as the time needed to recover sight of a target after an intense xenon flash exposure; GD was evaluated as the energy needed to veil a central target by a surrounding xenon annulus; GDC was measured using bio-imaging of the squint response and by self-report using a 9-item Likert scale; CC was measured as thresholds for a yellow grating target superposed on a 460-nm background; VA was determined by measuring vernier offsets of light lines through apertures. Based on our stimulus conditions, PSR was 43% faster using the Test vs. the Control. The eye wearing the Test had 38% less squint (GDC) compared to the Control. GD was improved by 36% in the Test vs. Control and CC was enhanced by 48% with the Test. There was no significant difference in VA. There was a beneficial influence on visual function when comparing the photochromic with the non-photochromic contact lens. This benefit was seen specifically with respect to PRT, GDC, GD and CC thresholds.