Cumulative Curve to Detect Neuroretinal Rim Area Defects in Glaucomatous Optic Nerve Heads

The aim of the study was to evaluate the capacity of rim area/disc area (RA/DA) cumulative curve analysis to distinguish optic nerve heads (ONHs) with a glaucomatous visual field from those with a normal visual field. One hundred and fifty-four subjects were consecutively recruited for the study. All the ONHs were analyzed by Image-net X Rev.3/51b (Topcon, The Netherlands), and all subjects were assessed by Humphrey 30-2 visual field (Humphrey Instruments, Inc, San Leandro, CA). Thirty-six equally spaced rim sectors of each optic disc were obtained from all ONHs and the median RA/DA cumulative curve was calculated. To increase the sensitivity of this analysis between early glaucoma and normal eyes, the cumulative curves were subsequently divided into two equal segments, and the slopes of their respective regression lines were compared. A significant difference (p<0.001) was found for the median 36 sector RA/DA values between glaucomatous eyes and normals. Because the cumulative curves distribution of early glaucomatous eyes were within the normal range, the cumulative curves of these cases with early glaucomatous damage were divided into two equal segments of 18 sectors, and the slopes of their regression lines were compared: a significant difference (p<0.05) was found in all these cases. Normal eyes were shown to be true negatives in 93% of cases in which no significant difference was observed between the two slopes. Analysis of the RA/DA cumulative curve from 36 sectors of optic disc is a valid method for the identification of glaucomatous disc pathology. However, further calculation of the slopes of the two RA/DA regression lines is needed to identify early glaucomatous damage.