Abstract
Purpose: :
To identify characteristics of myopic eyes with primary angle closure (PAC) using optical coherence tomography (OCT) and thus understand the mechanism leading to narrow angles. Since OCT does not require visible light, dilation or contact, eye measurements can be performed with the eye in its natural state.
Methods: :
Myopic PAC patients were examined using OCT (Visante AS). Myopic eyes without cataract of 11 non-diabetic study subjects were studied. Axial length, central anterior chamber depth (ACD), iris thickness at root, and lens thickness measurements were obtained from the images. Each of these measurements was then correlated to refraction data (spherical equivalent) which was used as a measurement of myopia. These data were analyzed using a statistics package (SAS Inc; Cary, NC) and Pearson correlation coefficient, coefficient of determination, p-value, mean, median, and standard deviation data were obtained.
Results: :
Analyses of 15 eyes revealed a statistically significant correlation between axial length and spherical equivalent in both right and left eyes (r = -0.88, p-value = 0.0044, left eyes, r = -0.79, p = 0.0330, right eyes). The correlation between lens thickness and spherical equivalent was significant for the group of left eyes (r = -0.80, p-value = 0.0183) but was not significant for the right eyes (r = -0.63, p-value = 0.1270). There was no statistically significant correlation between iris thickness or ACD and spherical equivalent. Mean axial length of 8 left eyes was 24.554±1.274 mm and that of 7 right eyes was 24.449±1.239 mm. Mean ACD of 8 left eyes was 2.891±0.279 mm and 2.951±0.238 mm in the 7 right eyes (normal eyes from literature ACD = 2.8 mm). Mean lens thickness of the 8 left eyes was 6.669±0.457 mm and 6.541±0.514 mm in the 7 right eyes in contrast to normal lens thickness from literature which ranges from 4.05 to 4.76 mm.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • myopia • anterior segment