Abstract
Purpose: :
To assess the microstructures of the cornea including the thicknesses of the epithelium and stroma in keratoconic and normal eyes by Fourier-domain optical coherence tomography (FD-OCT).
Methods: :
Twenty normal eyes and 57 keratoconic eyes were studied. The eyes were examined by FD-OCT combined with a low magnification corneal adapter (RTVue, Optovue Inc.). The scan was a "cross pattern", which consisted of vertical and horizontal lines with scan lengths of 6 mm. The thicknesses at the corneal vertex and at the superior, inferior, nasal, and temporal cornea 1.5 mm from the corneal vertex in keratoconic eyes with only smooth corneal thinning and corneal protrusion (KC-A group) were compared to those in normal eyes. The other keratoconic eyes (KC-B group) were classified according to their FD-OCT findings.
Results: :
Thirty of the keratoconic eyes were placed in the KC-A group and 27 in the KC-B group. Twenty-one eyes with stromal opacities, 4 eyes with a rupture of Descemet membrane, and 2 eyes with epithelial deposits were found in the KC-B group. The average thicknesses (µm) of the corneal epithelium/stroma at the corneal vertex, superior, inferior, nasal, and temporal cornea were 58.3/473.8, 56.2/493.3, 56.4/467.3, 55.0/471.4, and 54.6/486.6 in the normal eyes, and 42.8/403.1, 55.1/449.3, 49.3/396.8, 48.1/402.2, and 55.0/435.5 in the KC-A group, respectively. The stromal thicknesses at all the points and the epithelial thicknesses at the corneal vertex, inferior and temporal cornea were significantly thinner in the KC-A group than those in normal eyes (p<0.05). The correlations between the epithelial and stromal thicknesses at the corneal vertex were not significant in the control eyes (p=0.18) but significant in the KC-A group (r2=0.194, p=0.008).
Conclusions: :
FD-OCT is a useful instrument to measure the corneal epithelial and stromal thicknesses. Both the stroma and epithelium were thinner in keratoconic eyes than in normal eyes.
Keywords: keratoconus • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • cornea: clinical science