The antidepressant effect of Ambient Illumination may be attenuated by opthalmic diseases

Abstract

Abstract: : Purpose: This study investigated the relationships of ambient illumination to depressed moods and the contribution of eye diseases as an explanatory factor.Methods: Seventy Black (59%) and White (41%) Americans participated in the study (women, 73% and men 27%; average age = 68.27 ± 5.97 years). Baseline measures included physical health, depressed mood (G DS), sleep quality (PSQI) and sociodemographic information. Participants who met study criteria underwent a comprehensive eye exam, providing data on visual acuity, visual field defects, intraocular pressure, cup–to–disk ratio, and nerve fiber layer thickness. During the week that followed eye exams, participants wore an actigraph (Actiwatch–L) at home to monitor ambient illumination levels. Cosine analyses were performed on the logarithm of measured illumination, yielding average daily illumination levels and acrophase timings. Results: Of the sample, 85% reported being in good to excellent health. None of the volunteers were legally blind, but 27% were visually impaired; 5.8% received a diagnosis of glaucoma; 7.2%, cataract; and 7.2%, ocular hypertension. The median daily illumination in this sample was 518 lux, with acrophase timing averaging 14.30 ± 1.29 hours. Participants exposed to lower ambient illumination reported more depressed mood [r_p = –0.33, p < 0.05]; age, sex, ethnicity, BMI, education, and sleep duration were controlled. With further control for visual acuity, intraocular pressure, visual field mean deviation, cup–to–disk ratio, nerve fiber layer thickness, and diagnosis, the magnitude and significance of the correlation diminished [r_p = –0.26, NS]. Individuals receiving daily illumination later in the day were characterized by more depressed mood [r_p = 0.36, p < 0.01]; this correlation was, however, not significant after control for the covariates [r_p = 0.18, NS]. Conclusions: Our findings suggest that ambient illumination has an antidepressant effect, and that its biologic effects may be attenuated by eye diseases. It remains unclear how differing eye diseases might differentially compromise retinal input to the SCN, although one might conjecture that individuals with glaucomatous retinopathies may be at increased risks for circadian malsynchronization. It is believed that the peripheral ganglion cell damage noted in glaucoma might be particularly harmful to the melanopsin cells, which are the hypothesized circadian photopigment transducing environmental light cues to the SCN via the retinohypothalamic tract.

Keywords: circadian rhythms • photoreceptors • melatonin