The “topography” of glaucomatous defect using OCT and visual field examination

Aim: To describe the modifications in the superior and inferior retinal nerve fiber layer (RNFL) thickness regarding the distribution of the VF defects for the horizontal meridians in glaucomatous patients and the differences in the RNFL thickness topography between glaucomatous and healthy subjects. Methods: One hundred twenty eyes of 91 patients affected by glaucoma and 94 eyes of 51 normal patients were retrospectively reviewed. Computerized 30°VF (Octopus G1 Dynamic strategy) and optical coherence tomography (OCT) ONH and 3D disk analysis were performed in all cases. The RNFL thickness measures analyzed in both groups were superior-nasal (SN), superior-temporal (ST), inferior-nasal (IN), and inferior temporal (IT) sectors. The VFs were classified according to the distribution of the VF defect as for the horizontal meridian in the pattern deviation plot as superior, inferior, predominantly superior, or predominantly inferior. Result: In the glaucomatous group, 78 eyes (65%) showed a predominantly superior VF defect, while 38 eyes (32%) showed a predominantly inferior VF defect. Fifty-six eyes (46.7%) presented an exclusively superior, and 27/120 eyes (22.5%) presented an exclusively inferior VF defect. In the control group, the thickest RNFL sector was IT. The ST sector showed the thickest RNFL in presence of an exclusive superior VF defect. In case of an exclusive inferior VF defect, the thickest RNFL was the IT sector. VF showing superior defect presented a more altered MD than the VF with an inferior defect. Conclusion: Glaucomatous damage affects both the superior and inferior neural rim almost simultaneously. However, the neural rim loss seems to be asymmetric, involving the inferior or superior rim depending on the predominant involvement of the superior or inferior hemifield at the VF test. Particularly, the IT sector appears to be the most compromised in glaucomatous eyes. Therefore, the asymmetry between superior and inferior RNFL could support the diagnosis of glaucoma.