Persistent Cannabis Use and Ocular Health in Midlife

Cannabis is widely used and is becoming legal in many countries. Although some acute ocular effects of cannabis are well known (e.g., reduced intraocular pressure, vasodilation), little is known about the consequences of long-term cannabis use for ocular health. The aim of this study was to examine the association between persistent cannabis use across adulthood and measures of ocular health in midlife.

Participants were members of the Dunedin Study (N=1,037), a longitudinal cohort followed since birth. Cannabis use has been measured by self-report at every assessment from age 18 years to age 45 years. Ocular health data were collected as part of a larger assessment at age 45 years (2017-2019). Statistical analysis was performed in 2022.

Cannabis use and ocular health data were obtained from 887 study members. Generalized estimating equation analysis showed that higher cannabis use was associated with poorer visual acuity, wider retinal arterioles and venules, and a thicker inferior hemifield of the ganglion cell-inner plexiform layer. However, when controlling for tobacco smoking and SES (known to be associated with these ocular health domains), the associations with visual acuity, arterioles, and venules were no longer significant. The association with ganglion cell-inner plexiform layer remained significant in this adjusted model.

Persistent cannabis use appears to be neither harmful nor beneficial to the eye at age 45 years, although the thicker inferior ganglion cell-inner plexiform layer hemifield in users of cannabis suggests biologically plausible neuroprotection. Further assessments as this cohort ages will illuminate the relationship between persistent cannabis use and ocular neuroprotection.