Primary Open-angle Glaucoma and Normal Tension Glaucoma Diagnosis: The Role of Macular Thickness Asymmetry

Document Type : Original Article

Authors

1 Department of Ophthalmology, Faculty of Medicine, Al-Azhar University, Cairo, Egypt

2 Department of Ophthalmology, Faculty of Medicine [for girls], Al-Azhar University, Cairo, Egypt

Abstract

Background: According to reports, the macula provides a number of potential physiological and anatomical benefits for glaucoma detection and management.
The Aim of the work: This study aims to determine if spectral domain optical coherence tomography [SD-OCT] measures of macular and peripapillary retinal nerve fiber layer [RNFL] thickness can reliably differentiate between primary open-angle glaucoma [POAG] and normal-tension glaucoma [NTG].
Patients and Methods: A prospective study enrolled 10 healthy participants, 29 glaucomatous patients: 13 with POAG and 16 with NTG. Diagnosis based on intraocular pressures, visual fields, and optic nerves. The following parameters were measured by SD-OCT B-scans: RNFL thickness [circumpapillary scan] and macular thickness [posterior pole asymmetry scan] in both eyes and then recorded in addition to the calculated inter-eye and intra-eye differences [asymmetry parameters]. Receiver operator characteristic [ROC] analysis was used to determine the optimum cut off value for the studied diagnostic markers [RNFL and macular thickness].
Results: Inferior macular thickness asymmetry [intereye] had the highest discrimination for normal-POAG [AUC=0.838, sensitivity = 61.5% at 80% specificity], followed by inferior RNFL thickness [intereye] asymmetry [AUC=0.808, sensitivity = 61.5% at 80% specificity]. For normal-NTG total macular thickness asymmetry [intereye] had the highest discrimination [AUC=0.756, sensitivity = 68.8 % at 80% specificity], followed by inferior RNFL thickness [intereye] asymmetry [AUC=0.700, sensitivity = 62.5 % at 80% specificity].
Conclusion: For the discriminating of NTG and POAG, the macular parameters function is comparable to the RNFL parameters. The top SD-OCT metrics with the best discriminating skills were intereye Inferior macular thickness asymmetry, the total retinal nerve fibre layer thickness, the intereye inferior retinal nerve fibre thickness, and the inferior macular thickness

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