Sub-classification of myopic glaucomatous eyes according to optic disc and peripapillary features

PURPOSE To investigate the sub-classification of myopic glaucomatous eyes by optic disc and peripapillary features. METHODS Optic disc tilt and torsion were determined from retinal nerve fiber layer photographs. Based on the location of the Bruch's membrane (BM) opening within the β-zone of the peripapillary atrophy (PPA) area, the widths of β-zone PPA (PPA1W), PPA+BM (PPA2W), and PPA-BM (PPA3W) were measured with enhanced depth imaging spectral-domain optical coherence tomography. Cluster analysis that employed partitioning around medoids was performed with these parameters, the presence of inward rotation of BM ending axial length (AXL), and central corneal thickness. RESULTS A total of 115 eyes (AXL≥24 mm) were included. Two clusters produced maximum overall silhouette widths (average = 0.43). Visual field (VF) mean deviation was not different between cluster 1 (52 eyes; -4.02±3.01 dB) and cluster 2 (63 eyes; -5.21±5.62 dB; p = 0.174). In cluster 1 compared to cluster 2, optic disc tilt was significantly greater, PPA1W and PPA3W were longer, and AXL was longer (all p<0.001). The presence of an inward rotation of BM ending was more frequent in cluster 2 (p = 0.043). Forty-one eyes (78.8%) in cluster 1 had superior VF defects while 10 eyes (19.2%) had inferior defects, and only one eye (2%) had defects in both hemifields. Eyes in cluster 2 were more evenly distributed: 55.6% had superior defects, 34.9% had inferior defects, and 9.5% had defects in both hemifields (p = 0.023). CONCLUSIONS Myopic glaucomatous eyes characterized by optic disc and peripapillary configurations can be classified as two distinct types, and the most distinct difference between the two was degree of optic disc tilt and width of PPA. The location of VF defects were also significantly different between two clusters.