Influence of optic disc size on neuroretinal rim shape in healthy eyes.

PURPOSE: To evaluate the influence of optic disc size on segmental neuroretinal rim area in healthy eyes. PATIENTS AND METHODS: The study included 193 eyes of 193 healthy patients with physiologic disc cupping. On 15 degrees color stereophotographic optic disc diapositives, optic disc area and neuroretinal rim area were morphometrically determined in 36 radial optic disc segments each measuring 10 degrees. RESULTS: The correlations of segmental rim area to disc area were significantly strongest (P < 0.01) and the regression lines were steepest in the inferior disc region, and the values were lowest in the temporal disc region. Complementary to the rim data, the correlations of segmental cup area to disc area were significantly strongest (P < 0.01) and the regression lines were steepest in the temporal disc region, and the values were lowest in the inferior disc region. In comparison with neuroretinal rim area, cup area was significantly (P < 0.01) more strongly correlated with disc area and the regression line was steeper in the whole optic disc and in each disc segment. The regional distribution of the widest rim part and smallest rim part was independent of disc size. CONCLUSIONS: The increase of rim area and cup area with increasing disc size differs between various disc regions. Because cup area increases more than rim area with increasing disc size, correction for disc size may be more important for segmental cup area than for segmental rim area. The rim shape with respect to the location of the smallest or broadest rim part is independent of disc size.

Comparison of measurements of neuroretinal rim area between confocal laser scanning tomography and planimetry of photographs.

BACKGROUND: To compare neuroretinal rim area measurements by confocal scanning laser tomography and planimetric evaluation of optic disc photographs. METHODS: For 221 patients with primary and secondary open angle glaucoma, 72 subjects with ocular hypertension, and 139 normal subjects, the optic disc was morphometrically analysed by the confocal scanning laser tomograph HRT (Heidelberg retina tomograph) and by planimetric evaluation of stereo colour optic disc photographs. RESULTS: Absolute rim area and rim to disc area were significantly (p < 0.0001) larger with the HRT than with planimetric evaluation of photographs. Differences between the two methods were significantly (p < 0.01) larger in normal eyes with small cupping than in normal eyes with large cupping, and differences were significantly (p < 0.01) larger in glaucomatous eyes with marked nerve damage than in glaucomatous eyes with moderate nerve damage. Coefficients of correlations between rim measurements of both methods were R2 = 0.60 for rim to disc area and R2 = 0.33 for absolute rim area. Planimetric measurements of rim area correlated significantly (p < 0.05) better than HRT determinations of rim area with mean visual field defect and retinal nerve fibre layer visibility. CONCLUSIONS: Measurements of absolute rim area and rim to disc area are significantly larger with the HRT compared with planimetry of disc photographs. Differences between both methods depend on disc area, cup size and glaucoma stage. The reason may be that the HRT measures the retinal vessel trunk as part of the neuroretinal rim. The differences between both methods, which should be taken into account if disc measurements performed by both methods are compared with each other, may not influence the main advantage of the HRT--that is, morphological follow up examination of patients with glaucoma.

Optic disc morphology in "age-related atrophic glaucoma".

BACKGROUND: This study was performed in order to evaluate whether, in primary open-angle glaucoma (POAG), patients with a different degree of fundus tessellation vary in optic disc morphology and level of intraocular pressure. METHODS: Color stereo optic disc photographs of 562 patients with POAG and a myopic refractive error of less than -8 diopters were morphometrically examined. According to the degree of fundus tessellation, the total group was divided into a tessellated subgroup (n = 256) and a nontessellated subgroup (n = 306), both matched for neuroretinal rim area and refractive error. RESULTS: In the tessellated subgroup, as compared to the nontessellated subgroup, the mean maximal intraocular pressure values were significantly lower, the parapapillary atrophy was significantly larger, the optic cup was significantly more shallow, frequency of disc hemorrhages was lower, the mean visual field defect was significantly more marked, and patient age was significantly higher. Within the whole study group, the degree of fundus tessellation increased significantly (P < 0.005) with decreasing mean maximal intraocular pressure, decreasing optic cup depth, and increasing degree of parapapillary atrophy. In the subgroups with the highest degree of fundus tessellation, parapapillary atrophy was the greatest and the mean maximal intraocular pressure was the lowest compared to other subgroups. CONCLUSION: At the low-pressure end of POAG, marked fundus tessellation is associated with large parapapillary atrophy, shallow disc cupping, mostly concentric emaciation of the neuroretinal rim, and high patient age. The results suggest a distinct subtype of POAG in older patients with relatively low intraocular pressure leading to a mainly diffuse atrophy of the optic nerve.

Optic disc morphology in juvenile primary open-angle glaucoma.

BACKGROUND: The aim of the study was to evaluate whether, in primary open-angle glaucoma (POAG), patients younger than 40 years differ in optic disc morphology from patients older than 40 years. METHODS: Out of a total group of 419 patients with POAG, we formed and compared two subgroups, one consisting of 37 patients with an age of less than 40 years, the other composed of 382 patients with an age equal to or more than 40 years. Both subgroups were matched for neuroretinal rim area. We examined the optic disc morphometrically using stereo disc photographs. RESULTS: The younger subgroup, as compared to the older subgroup, showed deeper and steeper optic disc cupping, concentric emaciation of the neuroretinal rim, a significantly smaller area of parapapillary atrophy, and significantly higher maximal and minimal intraocular pressure measurements (P < 0.001). The size and shape of the optic disc and the diameter of the retinal vessels at the optic disc border did not vary significantly. CONCLUSIONS: In POAG, patients younger than 40 years differ in optic disc morphology from patients older than 40 years. The younger patients with POAG have high minimal and maximal intraocular pressure readings and an optic disc morphology with deep and steep cupping, concentric loss of neuroretinal rim, and an almost unremarkable parapapillary atrophy. POAG in patients under 40 represents chronic high-pressure open-angle glaucoma with mainly diffuse optic nerve damage.