Tear meniscus analysis with Fourier-domain optical coherence tomography in keratoconus.

PURPOSE To measure the lower tear meniscus dynamics with Fourier domain-optical coherence tomography (FD-OCT) in keratoconus patients without dry eye findings to evaluate the effects of the corneal ectasia on lower tear meniscus parameters, and to determine the most affected meniscus variable from the corneal ectasia in keratoconus. METHODS Prospective, clinical study. Forty-one eyes of 25 keratoconus patients without dry eye and 40 eyes of 20 healthy subjects were included. The lower tear meniscus analysis with FD-OCT, and corneal topography, keratometry, and pachymetry measurements were performed in all eyes. The main outcomes, including the lower tear meniscus height (TMH), depth (TMD), area (TMA), and angle between cornea and the tear meniscus (α-angle), were assessed. The results were compared between the patients and the control subjects. RESULTS The average keratometric power was 53.94 ± 5.76 D (between 44.46 to 63.75 D) in keratoconic eyes. It was 43 ± 0.8 D (between 40.50 to 45.94 D) in the controls. The average TMH, TMD, and TMA values did not show any statistically significant difference between the patients and the controls (p = 0.39, p = 0.824, p = 0.516, respectively). However, the average value of the α-angle was significantly higher in keratoconic eyes when compared to controls (p = 0.031). It was positively correlated with the keratometric power (r = 0.577, p = 0.001). CONCLUSIONS The TMH, TMD, and TMA did not show any change with the corneal protrusion; however, the α-angle had positive correlation with the keratometric power in keratoconic eyes.