The Ability of Disc-to-Fovea Distance to Disc-Diameter Ratio to Estimate Optic Disc Size

PURPOSE: To investigate the usefulness of the measurement of disc-to-fovea distance to disc-diameter ratio (DF/DD ratio) in detecting large and small discs. METHODS: A total of 300 randomly selected subjects were included in the present study. All patients underwent stereoscopic disc photography and DF/DD ratio, which is the shortest distance between disc margin and fovea divided by mean disc diameter was determined by planimetry. The diagnostic accuracy of DF/DD ratio was evaluated using areas under the receiver operating characteristics curves (AUCs), sensitivity, and specificity. RESULTS: No significant differences in disc-to-fovea distance were observed among small and large disc groups. The DF/DD ratio was significantly lower in subjects with large discs (1.74 +/- 0.27) compared with subjects with small discs (2.70 +/- 0.15). AUCs of the DF/DD ratio were 0.942 and 0.947 in detecting large and small discs, respectively. In detecting disc size by a fixed DF/DD ratio of 2.0, sensitivity was 100% for both large and small discs, and specificity was 70.1% and 40.9% for the large and small discs, respectively. CONCLUSIONS: The DF/DD ratio may be a simple and useful clinical aid in detecting large and small discs. The 2.0 fixed DF/DD ratio, showed 100% sensitivity in detecting both large and small discs, although medium discs may be misdiagnosed as small discs more often than as large discs.

Optic disc area in Malaysian population / 国际眼科杂志(Guoji Yanke Zazhi)

· AIM: To evaluate the optic disc parameters in the three main ethnic groups of Malaysia (Malay, Chinese and Indian). Possible relationships between optic disc parameters and gender, intraocular pressure and axial length of eye were also studied. · METHODS: The study included 244 eyes of 122 subjects (61 cases with open angle glaucoma and 61 non- glaucomatous individuals) with clear ocular media. Magnification corrected measurements of optic disc diameters and area were done using Zeiss FF450 Plus fundus camera. Differences between the three ethnic groups were tested by using ANOVA. The association between factors such as gender, intraocular pressure and axial length of the eye, and the optic disc size was tested through Pearson's bivariate correlation analysis. · RESULTS: The overall mean vertical optic disc diameter as (1.96 ± 0.20) mm, horizontal optic disc diameter was (1.84±0.20)mm and optic disc area was (2.84±0.56)mm2. Indians had larger optic disc area compared to Malay and Chinese. However, the difference was not statistically significant. · CONCLUSION: Optic disc size is larger in Malaysian population than Caucasians, Among the three ethnic groups, Indians have the largest optic disc size without any statistical difference.

Optic disc of the myopic eye: relationship between refractive errors and morphometric characteristics

Because the optic disc in myopic eyes is different from a normal optic disc, there are many difficulties in examining the optic discs of myopic eyes. To study optic disc change due to myopia, we performed a morphometrical study of stereophotographs of 61 men, 109 eyes, who had no glaucoma history. The range of refractive error was from +0.75 diopter to -12.75 diopter, and all subjects had intraocular pressure below or equal to 21 mmHg. According to the increase in the myopic degree, the temporal slope of the disc cup was significantly decreased, but the ratio of the vertical disc diameter (VDD) to the horizontal disc diameter and the ratio of the width of peripapillary atrophy (PPA) to the VDD were significantly increased. The above results suggests that in high myopia the optic disc was tilted and the rim-cup border was indistinct and there are some problems in the estimation of the morphometric parameters. Also in evaluation of the PPA of myopic glaucoma patients, there may be some difficulty in deciding whether it is due to myopic change or glaucomatous damage.