Corneal thickness differences between type 2 diabetes and non-diabetes subjects during preoperative laser surgery...

To evaluate the differences in corneal thickness between type 2 diabetes subjects with HbA1c under 7.0% and non-diabetes subjects during their preoperative laser surgery examinations.

The mean of five consecutive corneal thickness measurements at the central and mid-peripheral cornea was obtained by means of noncontact scanning-slit corneal topography (Orbscan Topography System II; Orbscan, Inc., Salt Lake City, UT, USA) in 35 myopic non-insulin dependent type 2 diabetes subjects (17 males and 18 females) and 48 healthy myopic controls (23 males and 25 females).

The corneal thickness values at the central and mid-peripheral cornea were significantly higher in the diabetic group (p<.001). The diabetic subjects presented the highest thickness value in the superior cornea (n=22; 62.9%) followed by the nasal (n=9; 25.7%) and the temporal (n=4; 11.4%) cornea, but never in the inferior cornea. The control subjects presented the highest thickness value in the superior cornea (n=19; 39.6%) followed by the nasal (n=18; 37.5%), the inferior (n=6; 12.5%), and the temporal (n=3; 6.3%) cornea. The central corneal thickness (CCT) of the diabetes patients was not statistically correlated with their HbA1c (r²=.078; p=.104), body mass index (r²=.007; p=.633), and time from diagnosis of diabetes (r²=.025; p=.363), but it was correlated with their corneal endothelial cell density values (r²=.543; p<.001).

Diabetes subjects with HbA1c under 7.0% who are candidates for laser refractive surgery present thicker corneas than their age-matched control subjects. In these patients, there is a correlation between their CCT values and their corneal endothelial cell density values, so when higher CCT values were found, lower corneal endothelial cell density values were observed.