The effects of photochromic lenses on visual performance

Abstract

Background

The purpose of the current study was to evaluate the effects of filtering by an activated photochromic lens on visual performance in healthy adults. Glare disability, glare discomfort, heterochromatic contrast thresholds and photostress recovery time were assessed.

Methods

A subject‐masked, randomised, cross‐over design was employed. Seventy‐five healthy adults were recruited, aged 19 to 73 years (mean = 45.61 ± 13.24 years). Visual functions were measured using three different photochromic lenses that were partially activated with a steady state transmittance of 63 per cent T (Gray1), 71 per cent T (Gray2), and 71 per cent T (Brown). These lenses were compared with a clear (92 per cent transmission) polycarbonate lens. Glare disability was assessed as the intensity of a white (xenon)‐light annulus necessary to obscure a central grating target. Heterochromatic contrast thresholds were measured as absolute thresholds for a monochromatic 570 nm target superimposed on a 460 nm circular background. Glare discomfort was quantified using bio‐imaging of the squint response as well as a Likert‐based self‐report scale. Photostress recovery time was recorded as the time necessary to regain sight of a grating target after intense light exposure. Glare discomfort and photostress recovery were only assessed for the Gray1 lens compared to placebo. Lens order was randomised between subjects and conditions.

Results

All visual functions measured were significantly improved (p < 0.05) for all of the activated photochromic lenses tested versus the clear lens. In the glare disability and heterochromatic contrast conditions, numeric differences (p < 0.09) were also seen between each of the three different activated photochromic lens types. Glare discomfort and photostress recovery times were improved in the Gray1 condition, as quantified by both the squint and subjective responses (p < 0.05).

Conclusion

Adding filtering via a photochromic lens significantly increased subjects' abilities to cope with intense broadband and shortwave lighting conditions and to adapt back to normal viewing after being presented with an intense photostressor.

Key words:

• chromatic contrast
• glare
• photochromic lenses
• photostress
• visual performance

Acknowledgement

This study was funded by Transitions Optical.

Notes

a Strategic filtering and neural adaptation are likely complementary, which is why photochromic lenses can be a good strategy with patients who have cone dystrophy with a slowed photopic response.1987

b The global plano sunglasses market was valued at USD 10.82 billion in 2012 and is expected to grow at a compound annual growth rate of 8.0 per cent from 2013 to 2020. http://www.grandviewresearch.com/industry‐analysis/plano‐sunglasses‐industry

c Halogen has a spectrum2010 that is relatively deficient in short‐wave energy (400 to 500 nm) but peaks in the middle‐ to long‐wave region. We chose this target because this is a likely spectrum for objects that are typically encountered in the real environment.2015