Association Between Diabetes Mellitus and CT-Measured Optic Nerve Sheath Diameter: A Retrospective Observational Study

Diabetes mellitus is associated with microvascular, neurological, and ocular complications. The optic nerve sheath contains a cerebrospinal-fluid-containing subarachnoid space and can be assessed quantitatively on imaging. However, evidence regarding differences in CT-measured optic nerve sheath diameter (ONSD) between diabetic and non-diabetic patients remains limited.

To evaluate the association between diabetes mellitus and ONSD measured by CT and determine whether significant differences exist between diabetic and non-diabetic individuals.

This retrospective observational study included 104 patients aged 18-85 years who underwent non-contrast brain CT between June 2022 and June 2023. The sample comprised 52 diabetic and 52 non-diabetic patients. ONSD was measured bilaterally at 3 mm and 8 mm posterior to the globe using electronic calipers on the Syngo.via workstation. Patients with intracranial, orbital, or optic nerve conditions likely to affect ONSD were excluded. Group differences were evaluated using independent-samples t-tests. Multivariable linear regression models were additionally used to assess the association between diabetes status and ONSD after adjustment for age and sex.

Mean age was 56.50 ± 13.08 years in the diabetic group and 45.94 ± 16.57 years in the non-diabetic group. Mean ONSD was greater in diabetic patients at all four sites: right 3 mm, 6.09 ± 0.59 versus 4.39 ± 0.53 mm; left 3 mm, 5.93 ± 0.65 versus 4.52 ± 0.62 mm; right 8 mm, 4.86 ± 0.57 versus 3.73 ± 0.48 mm; and left 8 mm, 4.89 ± 0.59 versus 3.78 ± 0.49 mm. All unadjusted comparisons were statistically significant (t = 15.46, 11.32, 10.93, and 10.44, respectively; all p < 0.001). After adjustment for age and sex, diabetes remained significantly associated with greater ONSD at all four sites.

Diabetic patients had larger CT-measured ONSD than non-diabetic patients at both 3 mm and 8 mm posterior to the globe. The association remained significant after adjustment for age and sex. These findings support an association between diabetes mellitus and increased ONSD measurements but do not establish causality or a diagnostic cutoff. Prospective studies with standardized measurements and detailed clinical characterization are warranted.