The significance of the retinal nerve fiber layer and macular thickness measurements in the early diagnosis of glaucoma using optical coherence tomography

Objective To measure the retinal nerve fiber layer (RNFL) and macular thickness in glaucoma patients using optical coherence tomography (OCT) and to compare the correlation of both measurements with the early diagnosis of glaucoma. Methods The retinal nerve fiber layer and macular thickness of 41 glaucoma patients (64 eyes) and 62 normal subjects(101 eyes)were measured with a Stratus OCT. Parameters were compared between normal subjects and both early glaucoma patients and glaucoma patients. Comparisons included RNFL thickness in the superior, inferior, nasal, and temporal quadrants and the mean macular thickness in 4 quadrants of the inner and outer rings and total macular volume. The power of each parameter to detect early glaucoma was evaluated by area using the receive operating characteristic curve (ROC).Results All RNFL and macular parameters (RNFL thickness in 4 quadrants and mean macular thickness in different sections and total macular volume) showed statistically significant differences when normal subjects and glaucoma patients were compared(P=0.014～0.000). The highest ROC value for RNFL was mean thickness(0.961) followed by the inferior(0.928) and superior (0.924) RNFL. The highest ROC value for the macula was the inferior outer ring(0.876). All RNFL measurements and the four quadrants of the macular outer ring、and total macular volume showed statistically significant differences when normal subjects and early glaucoma patients were compared (P=0.021～0.000). The highest ROC value for RNFL was mean thickness(0.877)followed by the superior(0.783) and inferior (0.767) RNFL. The highest ROC value for the macula was for the inferior outer ring (0.728). Conclusion RNFL thickness is a more powerful indicator than macular thickness for detecting glaucoma. However, macular thickness provides a new detection method for the early diagnosis of glaucoma.