Evaluation of the relationship between dry eye syndrome severity and corneal sensitivity.

Purpose: This study aimed to evaluate the relationship between the objective severity of dry eye disease subjective symptoms, and corneal sensitivity.

Methods: The study included 62 eyes from 31 healthy volunteers and 150 eyes from 75 patients diagnosed with dry eye disease . Participants underwent the Schirmer I test, tear break-up time assessment, and corneal staining evaluation using the Oxford Scale. Subjective symptoms were assessed through the Ocular Surface Disease Index questionnaire and a modified Ocular Surface Pain Score questionnaire. Corneal sensitivity was measured in five corneal regions using a Cochet-Bonnet esthesiometer. Dry eye disease severity was graded from 1 to 5 based on the Oxford Scale. Comparative analyses were performed.

Results: Schirmer I and tear break-up time values were significantly lower in the DED group, while Ocular Surface Disease Index and Ocular Surface Pain Score were significantly higher (p<0.001 for all). Corneal sensitivity in all quadrants was significantly lower in DED patients (p<0.001 for all). A strong correlation was observed between the Ocular Surface Pain Score and the Ocular Surface Disease Index (r=0.983, p<0.001). Central corneal sensitivity exhibited a moderate positive correlation with Schirmer I and tear break-up time (p<0.001, r=0.583 and 0.657, respectively) and a moderate negative correlation with Ocular Surface Disease Index and Ocular Surface Pain Score (p<0.001, r=0.625 and -0.631, respectively). Disease severity progression was associated with increased Ocular Surface Disease Index and Ocular Surface Pain Score, but no statistically significant difference was found between Grades 3 and 5. Similarly, corneal sensitivity decreased with advancing disease severity, yet no significant difference was observed between Grades 4 and 5.

Conclusion: Corneal sensitivity decreases in dry eye disease and is negatively correlated with disease severity. Subjective symptoms increase with disease progression and show a positive correlation with severity. The absence of significant differences between the advanced stages suggests that neuropathic mechanisms and subbasal nerve plexus deterioration play a role in chronic and late-stage dry eye disease.