Tear film instability on the ocular surface is considered one of the core pathological mechanisms of dry eye. Short tear film break-up time dry eye (sBUT) is a subcategory of evaporative dry eye that may have a significant effect on patient complaints of ocular pain, according to a new study.

 Upon evaluating corneal tactile and pain sensations in patients with sBUT dry eye—defined by an sBUT of <5 seconds, a normal Schirmer test (>5mm) and few epithelial lesions—Japanese researchers found that these patients were hypersensitive to corneal pain. This suggests that corneal hyperalgesia could partly account for subjective symptoms in patients with sBUT dry eye, they note in the study abstract. 

The study enrolled 60 patients with sBUT dry eye and 46 healthy controls. The researchers discovered that patients with sBUT dry eye had higher corneal pain sensitivities (26.3 ± 23.1mm) than healthy subjects (6.9 ± 16.4mm) but similar corneal tactile sensations (52.0 ± 15.5mm and 52.9 ± 14.9mm, respectively). In the 36% of patients with sBUT dry eye and corneal hyperalgesia, defined as a pain sensitivity ≥40mm, the team observed a strong significant correlation between the subjective pain score and the objective corneal pain sensation. However, for the entire cohort they found a weak positive correlation between the subjective pain score and the objective corneal pain sensation.