Optical Coherence Tomography Reveals Changes to Corneal Reflectivity and Thickness in Individuals with Tear Hyperosmolarity

PURPOSE To investigate whether tear hyperosmolarity, a feature of dry eye disease (DED), affects central corneal thickness (CCT), corneal light reflectivity, and/or tear film reflectivity. METHODS This prospective, cross-sectional study involved 48 participants (38 with hyperosmolar tears and 10 controls with normo-osmolar tears). Symptoms and signs of DED (tear osmolarity, sodium fluorescein tear break-up time, ocular surface staining, Schirmer test) were assessed. CCT, and the reflectivity of the cornea and the tear-epithelial interface were quantified relative to background noise using Fourier-domain optical coherence tomography (FD-OCT). RESULTS CCT of eyes with severe tear hyperosmolarity, defined as eyes in the upper quartile of the hyperosmolar group, was less than control eyes (539.1 ± 7.4 vs. 583.1 ± 15.0 μm, P = 0.02) and eyes with less severe tear hyperosmolarity, defined as hyperosmolar eyes in the lower quartile (622.7 ± 5.8 μm, P < 0.0001). CCT showed a negative linear relationship with tear osmolarity for values above 316 mOsmol/L (R2 = 0.17, P = 0.01). Central corneal reflectivity was lower in hyperosmolar eyes than normo-osmolar eyes (45.1 ± 0.3 vs. 48.1 ± 0.6 pixels, P = 0.02); the greatest relative difference was in the anterior stroma, where corneal reflectivity was 4.7 ± 1.9% less in hyperosmolar eyes (P < 0.01). Peak reflectivity of the tear-epithelial interface was 4.8% ± 3.5% higher in the hyperosmolar group than the normo-osmolar tear group (P = 0.04). CONCLUSION Individuals with significant tear hyperosmolarity and clinical signs of symptoms of DED show reduced CCT and altered corneal reflectivity. TRANSLATIONAL RELEVANCE Anterior segment FD-OCT provides novel insight into corneal microstructural differences in individuals with DED.