Subclinical Ocular Surface Dysfunction And Reduced Contrast Sensitivity In Prediabetes

Prediabetes, a metabolic state characterized by impaired glucose regulation, is considered the most important precursor of type 2 diabetes mellitus and is estimated to affect approximately 7% of the adult population worldwide. Increasing evidence indicates that microvascular and macrovascular alterations may already occur during the prediabetic stage. The aim of this study was to evaluate ocular surface parameters and contrast sensitivity in individuals with prediabetes and to compare these findings with those of healthy controls in order to identify potential early ocular changes associated with the prediabetic condition.

This comparative cross-sectional study was conducted at the Department of Ophthalmology of a tertiary-care university hospital, including prediabetic patients referred from the endocrinology clinic.

This comparative cross-sectional study included 112 individuals diagnosed with prediabetes according to the American Diabetes Association (ADA) criteria and 80 healthy controls with a similar age and sex distribution. Prediabetic participants were referred from the endocrinology clinic to the ophthalmology department for ocular evaluation. All participants underwent a comprehensive ophthalmic examination including non-anesthetized and anesthetized Schirmer tests and tear break-up time (TBUT) measurement for the assessment of ocular surface parameters. Contrast sensitivity was evaluated using a computerized system at multiple spatial frequencies ranging from 1.5 to 18 cycles per degree (cpd).

When the prediabetic group was compared with the healthy control group, no statistically significant difference was observed in the non-anesthetized Schirmer test results (p = 0.337). However, the anesthetized Schirmer test and TBUT values were significantly lower in the prediabetic group (p = 0.014 and p < 0.001, respectively), indicating impaired basal tear secretion and reduced tear film stability. Furthermore, contrast sensitivity analysis demonstrated significantly decreased contrast perception across all spatial frequencies in prediabetic individuals compared with healthy controls (p < 0.001).

Prediabetic individuals exhibit alterations in ocular surface homeostasis characterized by reduced basal tear secretion and decreased tear film stability. In addition, the reduction in contrast sensitivity suggests that subtle functional changes in the visual system may occur before the development of clinically apparent diabetic ocular complications. These findings highlight that ocular surface evaluation and contrast sensitivity testing may provide valuable insights for detecting early ocular involvement in the prediabetic stage.