Correlation between Corneal Endothelial Cell Density and Central Ocular Surface Temperature in Normal and Keratoconus Eyes

Purpose: In keratoconus (KC), an increase of the corneal back surface area may result in endothelial cell density (ECD) decrease and an increase of the corneal front surface area in ocular surface temperature (OST) decrease due to increased heat dissipation. Along with these hypotheses, we aimed to analyse the correlation between ECD and central corneal OST in patients with KC and healthy controls. Patients and methods: A total of 154 eyes with KC (mean age 36.1 +/- 12.5 years) and 92 healthy eyes (mean age 36.4 +/- 12.8 years) were examined. Corneal front and back surface area at the central 5 mm corneal diameter (FSA and BSA) were calculated based on Pentacam measurement data: FSA or BSA = 2x3.14xR(R-root R-2-D/2)(2), where R referred to corneal front or back surface radius of curvature and D to the corneal front or back surface diameter (5 mm for the present study), respectively. ECD was determined by specular microscopy (EM-3000) and central corneal OST by thermography (TG-1000). Results: ECD was significantly lower in KC (2498 +/- 356/mm(2)) patients than in controls (2638 +/- 294/mm(2); p <.001). FSA (20.35 +/- 0.26 mm(2) vs. 20.17 +/- 0.03 mm(2)) and BSA (20.84 +/- 0.58 mm(2) vs. 20.45 +/- 0.08 mm(2)) were significantly higher in KC patients than in controls (p =.001; p <.001), but the average central corneal OST did not differ significantly between both groups (34.2 +/- 0.6 degrees C vs.34.3 +/- 0.7 degrees C; p =.62). OST at the corneal centre correlated weakly, positively with ECD (r = 0.2; p <.05), but OST did not correlate with FSA (r = 0.045) or BSA (r = 0.064). Conclusions: Endothelial cell density seems to have a mild impact on central ocular surface temperature in keratoconus and normal subjects. This effect is not correlated to the corneal front or back surface area.