Purpose: The aim of this study was to evaluate the association between diabetes mellitus (DM) and keratoconus.
Methods: We conducted 2 substudies: (1) Retrospective comparison of the prevalence of DM in patients with keratoconus with that of control patients without keratoconus and (2) Cross-sectional study of the severity of keratoconus in diabetic keratoconus-affected patients and nondiabetic keratoconus-affected patients. Patients seen at the Wills Eye Hospital Cornea Service from January 2008 to August 2012 were included. Study 1 included 1377 patients with keratoconus and 4131 controls without keratoconus. Study 2 involved 75 type 2 diabetic keratoconus-affected patients and 225 nondiabetic keratoconus-affected patient, excluding patients with bilateral keratoplasty. In patients with a history of a corneal transplant in 1 eye, the other eye was included. Keratoconus severity was based on the topographic mean keratometry in the more severely affected eye.
Results: Two of 1377 (0.15%) keratoconus-affected patients had type 1 DM, which was similar to that of 20 of the 4131 (0.49%) matched controls (P = 0.139). The prevalence of type 2 DM was higher in patients with keratoconus (93/1377, 6.75%) than in matched controls (200/4131, 4.84%) (P = 0.005). When categorized by age group, the prevalence of type 2 DM was higher in patients with keratoconus than in those without keratoconus in patients aged between 25 and 44 years (P = 0.036) and 45 and 64 years (P = 0.047). Using multinomial logistic regression analyses, the probability/risk of being in the severe keratoconus-affected group as opposed to the mild keratoconus-affected group was higher in patients with DM than in those without DM (P = 0.006; odds ratio = 2.691; 95% confidence interval, 1.330–5.445).
Conclusions: There may be a positive association between type 2 DM and the presence and severity of keratoconus.