Neuro–Retinal Rim Area in POAG and PACG

Abstract

Abstract: : Purpose:To compare neuroretinal rim area in cases of POAG and PACG with differing amounts of field loss. Methods: 206 people (139 men, 67 women) in a trial of glaucoma surgery underwent pre–operative stereo disc photography, gonioscopy and repeated static, automated, white–on–white perimetry (MD within 2dB on repeat testing). Computer–assisted planimetric measurements of the disc and neuro–retinal rim (NRR) area in mm² were corrected for ocular magnification. Mean defect was used to stratify cases by severity (Mild: 0 to–10 dB, Moderate: –11 to –20 dB, Severe: < –20 dB). Left disc planimetry data were transposed to right eye equivalents. Twelve disc NRR segments were identified by degrees from vertical in a clockwise direction. Results: 119 subjects with POAG and 87 with PACG were examined, mean age: 61.5 years (36 to 84). Median disc area did not differ between POAG and PACG cases (3.80 vs. 3.87, P= 0.455). Median NRR in POAG and PACG did not differ between mild (1.44 vs 1.59, P= 0.24), moderate (1.13 vs 1.06, P= 0.63) or severe cases (0.91 vs 0.89, P= 0.49). In severe cases (MD< –20 dB), two sectors of the inferior neuroretinal rim, 120° to 150° and 210° to 240°, POAG cases had a significantly smaller NRR than cases of PACG (0.052 vs 0.072, P= 0.043 and 0.059 vs 0.079, P= 0.014, respectively). The 180°–210° sector showed a trend toward NRR in POAG< PACG (0.066 vs 0.081, P=0.054). No other sectors showed a significant difference between POAG and PACG. There was no evidence of such a difference in mild or moderate disease. Following Bonferroni correction, and assuming independence between each sector of NRR, none of the differences remained significant. Conclusions: We identified, for a similar severity of field loss, a trend towards smaller areas of the inferior NRR sectors in cases of POAG compared with PACG. Although these differences were not statistically significant after Bonferroni correction, they do correspond with localisation of depressed retinal sensitivity previously reported from the same dataset.

Keywords: optic disc