Abstract
Introduction: Cannabis is widely used and becoming legal in many countries. While 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.
Methods: Participants were members of the Dunedin Study (n=1037), a longitudinal cohort followed since birth. Cannabis use has been measured by self-report at every assessment from age 18 to 45. Ocular health data were collected as part of a larger assessment at age 45 (2017-2019). Statistical analysis was performed in 2022.
Results: Cannabis use and ocular health data were obtained from 887 Study members. Generalised estimating equation analysis showed 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 (GC-IPL). However, when controlling for tobacco smoking and socioeconomic status (known to be associated with these ocular health domains), the associations with visual acuity, arterioles, and venules were no longer significant. The association with GC-IPL remained significant in this adjusted model.
Conclusions: Persistent cannabis use appears to be neither harmful nor beneficial to the eye at age 45, although the thicker inferior GC-IPL 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.