Optical coherence tomography in measuring retinal nerve fiber layer thickness in normal subjects and patients with open-angle glaucoma

Objectives To investigate image characteristics and thickness of the retina l nerve fiber layer (RNFL) in normal and glaucomatous eyes using optical co herence tomography (OCT), and analyze the relationship between RNFL thickne ss and visual field index. Methods Eighty-three normal persons (150 eyes) and 83 patients with primary open angle glaucoma (POAG, 149 eyes) underwent OCT examinations with 3.4 m m diameter circle scan to calculate the RNFL thickness. Statistical analysi s was used to compare differences in RNFL. thickness in quadrants and means between the normal and glaucomatous groups and the different stages of POA G. Linear correlation and regression analysis were used to show the correla tion between RNFL thickness and visual field index of 115 eyes in glaucomat ous patients. Reproducibility, sensitivity and specificity of RNFL measurem ents using OCT were evaluated. Results RNFL thickness measured by OCT in normal subjects was thicker in su perior and inferior, less in temporal, and thinnest in nasal quadrants. The curve showed double peaks. RNFL of glaucomatous patients showed local thin ning or defect, diffuse thinning, or both. The mean RNFL thicknesses of the normal group in the temporal, superior, nasal and infeior quadrants were 9 0.1 +/- 10.8 mum, 140.4 +/- 10.5 um, 85.2 +/- 14.0 mum, and 140.4 +/- 9.7 m um, respectively with a mean of 114.2 +/- 6.0 mum. The numbers for the glau comatous group were respectively 56.0 +/- 31.0 mum, 81.0 +/- 36.3 mum, 47.1 +/- 27.5 mum, and 73.4 +/- 38.4 mum for the four quadrants, with a mean of 64.6 +/- 28.8 mum. There was a significant difference in RNFL thickness be tween the normal and glaucomatous groups (P < 0.000), acid the three stages (early, developing and late) of glaucomatous groups ( P < 0.000). There wa s a close negative relationship between RNFL thickness and visual field ind ex (r = -0.796, P < 0.0001). The sensitivity and specificity of RNFL thickn ess in POAG measured using OCT were 93.3% and 92.0%, respectively. Conclusions OCT can quantitatively measure RNFL thickness differences betwe en normal persons and glaucomatous patients. RNFL thickness gradually decre ases while visual field defect increases with the development of POAG.