The interrelationship between the sectorial disc and the visual field changes in patients with normal tension glaucoma

Abstract

To investigate the changes of the sectorial discs and visual fields, and their interrelationships in patients with normal tension glaucoma (NTG). 26 patients with NTG were undergone the optic nerve and visual field examinations with HRT-II and HFA II in a time interval of less than 5 months. The parameters in the study including cup shape measure (CSM), rim area (RA), rim volume (RV), mean cup depth (MCD) and cup volume index (CVI) were compared between the global discs and the sectorial discs in eyes with the evidences of preperimetric or early visual field defect (MD < or = 4 dB). The CVI was proposed to be equal to CV/(DA x MCD + RA x RNFLT), where DA was disc area and RNFLT was retinal nerve fiber layer thickness. The linear correlations were evaluated between the visual field MD and each of 5 parameters in sectorial discs. The sectorial disc areas were mostly in correspondence to the damaged hemifields (CVI: 92.68%, RA: 87.80%, RV: 82.93%). In addition, a correlation was seen for CSM and MCD (63.41% and 53.66%; chi2 = 23.17, P < 0.05). The comparison between preperimetric and early defects were significantly difference (t = 1.735 approximately 6.536, P < 0.05 approximately P < 0.05, one-sided t test). The correlation between CSM and MD was negative (r = -0.3002, P > 0.05), however the positive correlation was demonstrated in RA versus MD (r = 0.3105, P < 0.05). The examination of the 5 parameters of sectorial discs had even closer relationship than those of global discs scanning in the detection of early vision field defect and it is valuable in diagnosis of early glaucoma.