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[Qualitative and quantitative measurement of retinal nerve fiber layer in primary open angle glaucoma by optical
1Zhongshan Ophthalmic Center, Sun Yat-sen University of Medical Sciences, Guangzhou 510060, China. ykoct@gzsums.edu.cn
Objective:
To study the characteristics of optical coherence tomography (OCT) of primary open angle glaucoma (POAG), the difference of retinal nerve fiber layer (RNFL) thickness between normal persons and patients with POAG and the correlation between RNLF and visual field index.
Methods:
Eighty-three cases (149 eyes) with POAG and 83 normal persons (150 eyes) were tested by OCT with circular scans around the optic nerve head (diameter = 3.46 mm) to observe the features of OCT. Statistic analysis was taken to compare the difference of RNFL thickness in quadrants and means between normal and glaucomatous group, and the difference of the thickness among the stages in POAG. Linear correlation and regression analysis was used to show the correlation between RNFL thickness and visual field index of 115 eyes of glaucomatous patients.
Results:
The RNFL thickness measured by OCT in normal subjects is the thickest in superior and inferior quadrants, less in thickness in temporal and the thinnest in nasal quadrant. The curve showed double peaks. The RNFL of glaucomatous patients showed local thinness or defect, diffuse thinness or combination of the above two types. The mean RNFL thickness of normal group was (90.1 +/- 10.8) microm, (140.4 +/- 10.5) microm, (85.2 +/- 14.0) microm, (140.4 +/- 9.7) microm and (114.2 +/- 6.0) microm, of glaucomatous group was (56.0 +/- 31.0) microm, (81.0 +/- 36.3) microm, (47.1 +/- 27.5) microm, (73.4 +/- 38.4) microm and (64.6 +/- 28.8) microm in temporal, superior, nasal, inferior quadrant and the whole area, respectively. There is significant difference of RNFL thickness between the normal and glaucomatous group (P < 0.000), and there are significant differences among the three stages (early, developing and late) of glaucomatous group (P < 0.000). There is a close negative relationship between RNFL thickness and visual field index (r = -0.796, P < 0.0001). The sensitivity and specificity of RNFL thickness measured by OCT were 93.3% and 92.0%, respectively.
Conclusion:
OCT can quantitatively measure the RNFL thickness and show the difference of RNFL between normal persons and glaucomatous patients. The RNFL thickness gradually decreases while visual field defect increases with the development of POAG.