Alcohol consumption is widely known to have a dehydrating effect, and previous studies have begun to examine how ethanol impacts the ocular surface and tear film, potentially increasing the risk for dry eye disease. This topic can be taken a step further, though, with deeper analysis and assessment of the immediate effects of alcohol on tear lipid layer and functional vision, according to a prospective controlled study conducted in Japan and published in Eye & Contact Lens.
The investigation recruited 44 volunteers and separated them into 2 groups; 22 patients (mean age 35.3 years), who drank 200 mL of 25% Japanese vodka (shochu) in 1 hour, and a control group of 22 sex- and age-matched participants, mean age 37.5 years, who drank 200 mL of water during the same period. Participants did not smoke, had no history of systemic or ocular disease, and displayed body mass index of 20 to 25 kg/m2. Breathalyzer and ocular tests were completed prior to the experiment, and also after 2 hours and 12 hours.
Researchers found that even though breath alcohol-level returned to baseline in 12 hours, functional visual acuity (FVA) and tear film instabilities were still present.
LogMAR visual acuity and mean visual maintenance ratio (VMR) of the 2 groups started off similarly (P >.05), but then significant changes occurred in those consuming alcohol. After 12 hours, mean logMAR FVA declined from -0.17 to 0.03 (P <.001). Mean VMR decreased from 98.5 to 93.3 at 12 hours (P <.001). Blink rates increased significantly for this group, starting at a pre-experiment average of 10.6 blinks per minute, rising to 13.5 blinks per minute after 2 hours, and to 15.1 blinks per minute after 12 hours.
DR-1 tear lipid layer interferometry revealed all those who consumed alcohol exhibited Yokoi grade 5 scores; the lipid layer spread partially across the cornea, with areas of lipid layer thinning and corneal surface exposure at 12 hours. Mean tear evaporation rate (TEROS) more than tripled in the alcohol group, from 2.5 gr/cm2/sec, to 8.8 gr/cm2/sec at 12 hours, while for water drinkers, TEROS remained between 2.23 gr/cm2/sec and 2.45 gr/cm2/sec. For the alcohol group, tear film break-up time (TBUT) was 15 seconds both at baseline and 2 hours, but increased to 5 seconds after 12 hours.
In Schirmer tests, the water intake group maintained tear quantity at mean 12.0 to 13.0 mm/5 min throughout the study. However, for alcohol drinkers, tears reduced from 13.7 mm/5 min at baseline, to 7.6 mm/5 min after 12 hours (P <.001). Visual analog scale (VAS) scores averaged approximately 20 points at baseline in both cohorts. While the control set remained near this level, the alcohol group increased to more than 30 points at 2 hours, and to more than 50 points after 12 hours (P<.001).
“It is our belief that alcohol intake induces increased tear evaporation due to dehydration, causing an increase in tear osmolarity,” the researchers add. “Although the tear osmolarity has not been assessed in this study, a possible increase in osmolarity is expected to cause dry eye symptomatology.”
Simsek C, Kojima T, Dogru M, et al. The early effects of alcohol consumption on functional visual acuity, tear functions, and the ocular surface Eye & Contact Lens.2021;47(1):20-26. doi:10.1097/ICL.0000000000000725