Study: Dry eye and vision
More gleanings from the DREAM Omega 3 study. Really, the saving grace of that study - whose chief result (that Omega 3s were no better than placebo) has been widely disputed, not to say discredited - as best I understand - on the basis that they should not have used an olive oil placebo - is that they gathered so much data that it can be re-crunched to learn lots of other things.
Anyway, I really like the questions being asked in this study, which are all about digging deeper into the details of the relationship between dry eye and cruddy vision. Since historically, vision quality has tended to get short shrift in eye care (maybe really this is just my old grudge against the LASIK world showing up again), I particularly like to see investigation into the distinction between visual acuity and vision quality (quality encompasses things like contrast sensitivity, starbursts/halos, etc).
You know the vision parts of the OSDI survey? This study found that scoring poorly on those correlates to poorer visual acuity (i.e. the best line you can make out on an eye chart). On the other hand, poor tear film stability e.g. with a low tear break-up time, plugged meibomian glands etc has a closer relationship with contrast sensitivity.
Impact of Dry Eye on Visual Acuity and Contrast Sensitivity: Dry Eye Assessment and Management Study. Szczotka-Flynn et al (for the Dry Eye Assessment and Management (DREAM) Study Research Group), Optom Vis Sci. 2019 May 20
Identification of the association of specific signs of dry eye disease with specific visual function deficits may allow for more targeted approaches to treatment.
The purpose of this study was to explore the association of dry eye signs and symptoms with visual acuity (VA) and contrast sensitivity in the Dry Eye Assessment and Management study.
Baseline data from participants in the Dry Eye Assessment and Management study were used in this secondary cross-sectional analysis. Standardized procedures were used to obtain results on the Ocular Surface Disease Index (OSDI), high-contrast logMAR VA, contrast sensitivity, tear film debris, tear breakup time (TBUT), corneal fluorescein staining, meibomian gland evaluation, conjunctival lissamine green staining, and Schirmer test scores. Generalized linear models that included age, refractive error status, and cataract status were used to assess the association between VA and contrast sensitivity with OSDI score and each dry eye sign. The Hochberg procedure was used to account for multiple comparisons.
Among 487 participants (974 eyes), worse VA was associated with worse mean score on the OSDI vision subscale (39.4 for VA 20/32 or worse vs. 32.4 for VA 20/16 or better; adjusted linear trend, P = .02); scores were not associated with contrast sensitivity. Severe meibomian gland plugging and abnormal secretions were associated with worse mean log contrast sensitivity (1.48 for severe vs. 1.54 for not plugged [P = .04] and 1.49 for obstructed vs. 1.57 for clear [P = .002], respectively). Longer TBUT was associated with better mean log contrast sensitivity (1.57 for TBUT >5 seconds and 1.51 for TBUT ≤2 seconds, P < .0001).
Worse VA rather than worse contrast sensitivity drives vision-related symptoms in dry eye. Greater tear film instability was associated with worse contrast sensitivity.