Abstract
Purpose: :
To our knowledge, this is the first study to determine whether there are different patterns of retinal nerve fiber layer (RNFL) thickness as measured by spectral domain optical coherence tomography (SD-OCT) for four different types of open angle glaucoma (OAG): primary OAG (POAG), normal tension glaucoma (NTG), pseudoexfoliation glaucoma (PXG), and pigmentary glaucoma (PDG). These results were also compared to normal controls.
Methods: :
SD-OCT (Heidelberg Engineering, Heidelberg, Germany) RNFL thickness values were measured for 4 quadrants as well as the superior nasal, superior temporal, inferior nasal and inferior temporal sectors. Differences in RNFL thickness were analyzed using analysis of variance (ANOVA) while adjusting the alpha level under Bonferroni criteria. Pairwise t-test was undertaken for contralateral eye comparisons.
Results: :
The study population consisted of 344 eyes of 172 patients: 44 patients with OAG, 29 with NTG, 42 with PXG, 9 with PDG, and 48 without glaucoma. The mean global RNFL thickness values were significantly thinner in glaucoma patients (70.30 ± 18.0µm for POAG, 71.90 ± 17.1µm for NTG, 73.88 ± 18.7µm for PXG, 65.11 ± 18.1µm for PDG) compared to normals (90.10 ±17.9µm). The RNFL thickness was significantly different for superior, inferior and nasal quadrants among the different subtypes of OAG (p< 0.0001) and for the control group. Only the temporal quadrant was not significantly different between the 5 groups (p= 0.55). POAG patients had more inferior than superior RNFL quadrant thinning, PXG and PDG patients had more superior than inferior RNFL quadrant thinning, and NTG patients had similar degrees of RNFL thinning for inferior and superior quadrants. We only found inter-eye asymmetry in RNFL thinning in the temporal quadrant for the POAG group (p=0.007).
Conclusions: :
This study suggests that SD-OCT may be able to detect significant differences in patterns of RNFL thinning for the different subtypes of OAG. Overall RNFL is significantly thinner in OAG compared to normal patients. Significant differences in patterns of RNFL thinning were found among all studied subtypes of OAG. POAG patients appear to have more inferior RNFL thinning, PXG and PDG patients have more superior RNFL thinning, and NTG patients had similar degrees of superior and inferior quadrants RNFL thinning.
Keywords: imaging/image analysis: clinical