Corneal diameter distribution and its determinant factors in elderly population: Tehran Geriatric Eye Study

To determine the distribution and normative range of corneal diameter in individuals aged over 60, and its association with demographic variables, certain comorbidities, anthropometric measurements, additional ocular biometric indices, and refractive errors.

This population-based cross-sectional study involved participants aged over 60 residing in Tehran, selected by a multi-stage cluster random sampling. Following the acquisition of informed consent, comprehensive ophthalmological and optometric evaluations, including slit lamp examination, visual acuity assessment, and refraction, were conducted. Ocular biometric parameters, including corneal diameter, were assessed using the Pentacam AXL.

A total of 4596 eyes (2292 right eyes and 2304 left eyes) from 2414 older individuals were examined. The mean age with 95% confidence interval (CI) of the study participants was 66.74y (66.51-66.97y), with 58.68% identifying as female. The corneal diameter in the older population had a normal distribution, with a mean of 11.82 mm (95%CI: 11.80-11.84), and a normal range of 11.02-12.62 mm. According to the results of multiple linear regression, a deeper anterior chamber (b=0.30, P<0.001), a university education level (b=0.08, P=0.001), and hyperopia (b=0.04, P=0.005) exhibited a positive correlation with corneal diameter, whereas female gender (b=-0.05, P<0.001), a thicker cornea (b=-0.01, P<0.001), a higher mean keratometry (b=-0.09, P<0.001), and astigmatism (b=-0.03, P=0.013) demonstrated an inverse correlation with corneal diameter. The corneal power was the most important factor that influencing corneal diameter. Nonetheless, the variables of myopia, axial length, diabetes, blood pressure, body mass index (BMI), economic situation, and age exhibited no significant association with corneal diameter.

The corneal diameter range measured by Pentacam AXL in the elderly population is greater than certain prior studies and lesser than others. The findings serve as a reference for clinicians assessing corneal diameter in the elderly for clinical application.