Repeatability and Reproducibility of Macular Thickness Measurements Using Optical Coherence Tomography (OCT) in Normal Eyes Before and After Pupil Dilation

Abstract

Background Optical coherence tomography (OCT) is one of the most valuable imaging techniques in the evaluation of macula. The repeatability and reproducibility of OCT are of crucial importance in reassuring this tool’s efficacy in evaluating the structure of the retina. Objective This study aims to investigate the repeatability and reproducibility of OCT in measuring the macular thickness in normal eyes before and after pupil dilation. Methods A total of 44 eyes of healthy individuals in the age range of 20 to 50 years were employed for the measurement of macular thickness in the central 6 mm using the Cirrus SD-OCT tool. Results According to ICC, the repeatability of macular thickness was 0.95 (95% CI, 0.95 - 0.96). The mean macular thickness before and after pupil dilation was statistically significant in the nasal quadrant of the outer 6 mm ring (N2) and the inferior quadrant of the outer 6 mm ring (I2) (P=0.0001). The highest repeatability before and after pupil dilation was seen in the nasal quadrant of the inner 3 mm ring (N1) and the central ring (C), respectively. Conclusion This study shows that measuring the macular thickness using the Spectral domain cirrus OCT (SD-OCT) has acceptable repeatability and reproducibility. Since the absolute value of the mean difference between the three measurements in the N2 and I2 regions was statistically significant, using a single method (i.e., whether to apply the eye drop) is preferable for follow-ups in cases where the measurements are needed within 3 to 6 mm in center of the macula.