Purpose: To evaluate the association between dry eye disease (DED) parameters and corneal sensitivity in patients with type 2 diabetes mellitus (T2DM) and to determine if peripheral neuropathy severity correlates with ocular surface changes.

Methods: A cross-sectional study was conducted on 94 patients with T2DM attending a tertiary care ophthalmology department. All participants underwent comprehensive ocular examination including Ocular Surface Disease Index (OSDI) questionnaire, tear film breakup time (TBUT), corneal fluorescein staining (CFS), Schirmer I test (without anesthesia), and central corneal sensitivity measurement using a Cochet-Bonnet esthesiometer. Diabetic peripheral neuropathy (DPN) was assessed using the Michigan Neuropathy Screening Instrument (MNSI). Correlations were analyzed using Pearson’s coefficient and multivariate regression.

Results: Of 94 T2DM patients (mean age 58.3 ± 9.4 years; 51.1% female), 71 (75.5%) met diagnostic criteria for DED. Mean corneal sensitivity was significantly lower in diabetic patients with DED (4.8 ± 1.2 cm) compared to those without DED (5.9 ± 0.6 cm, p<0.001). TBUT showed a moderate positive correlation with corneal sensitivity (r=0.52, p<0.001), while OSDI score demonstrated a negative correlation (r=-0.48, p<0.001). Patients with longer T2DM duration (>10 years) had 3.2-fold higher odds of severe corneal hypoesthesia (≤4 cm on esthesiometry). DPN presence (MNSI ≥2.5) was associated with significantly reduced corneal sensitivity (mean 4.5 vs. 5.7 cm, p<0.001) and shorter TBUT (4.1 vs. 7.8 seconds, p=0.002).

Conclusion: Corneal sensitivity is markedly reduced in T2DM patients with DED, and this reduction parallels the severity of peripheral neuropathy. Routine corneal esthesiometry should be considered in diabetic patients presenting with dry eye symptoms, as standard DED therapies may be less effective in the setting of neurotrophic corneas.

KEYWORDS: Type 2 Diabetes Mellitus, Dry Eye Disease, Corneal Sensitivity, Diabetic Neuropathy, Neurotrophic Keratopathy.