Are large optic nerve heads susceptible to glaucomatous damage at normal intraocular pressure?

To evaluate the effects of the presence of glaucomatous visual field defects and of intraocular pressure elevations on optic nerve head topography, we analyzed 148 left optic nerve heads of 148 patients using laser scanning tomography. The optic discs are classified according to computerized static perimetry and documented IOP readings: 101 discs show normal visual fields (36 normal discs, 22 ocular hypertensives, 28 normotensive glaucoma suspects and 15 ocular hypertensive glaucoma suspects), 47 discs (34 high-pressure glaucoma discs, 13 normal-tension glaucoma discs) demonstrate glaucomatous visual field damage. A two-way analysis of variance discloses significant differences (P<0.01) between the groups of optic discs classified according to perimetry for most topometric parameters evaluated exept for disc area. Classification according to documented IOP (cut off at 21 mmHg) results in larger disc areas in normotensive discs compared to hypertensive optic nerve heads in the study population. Results suggest that large discs may be susceptible to glaucomatous visual field damage at statistically normal IOP readings.This study was supported in part by a grant from the Deutsche Forschungsgemeinschaft DFG Vo 437/1-1 Correspondence to: R.O.W. Burk     

Optic disc size and optic nerve damage in normal pressure glaucoma.

BACKGROUND--Recent reports indicate that eyes with normal pressure glaucoma have larger optic discs than eyes with primary open angle glaucoma or normal eyes. This study was performed to find whether, in normal pressure glaucoma, a large disc is associated with more optic nerve damage than a small disc. METHODS--Colour optic disc photographs of 74 patients with normal pressure glaucoma were assessed morphometrically. RESULTS--Taking the study group as a whole, the optic disc size decreased significantly (p = 0.04) with increasing visual field defect. In an intraindividual bilateral comparison, the side differences in the disc area of the right minus the left eye of the same individual were not significantly correlated with the side differences in the mean visual field defect. CONCLUSIONS--The results indicate that the eye with the larger optic disc, when compared with the contralateral eye with the smaller optic nerve head, showed neither a significantly more marked nor less pronounced glaucomatous optic nerve damage. It suggests that for a given patient the degree of glaucomatous optic nerve atrophy was not markedly associated with the optic disc size. The finding that patients with large visual field defects had smaller discs than patients with moderate perimetric loss may indicate that the results of previous cross sectional studies reporting on an unusually large disc size in normal pressure glaucoma may be due partially to selection.     

人眼视神经组织形态学研究视神经纤维计数和直径及视盘面积的测定

目的通过测量正常人眼视神经纤维数量、直径及视盘面积，为青光眼视神经损害研究奠定基础，并对其相互关系进行分析。方法应用一种计算机图像分析系统对15只正常人眼视神经断面和视盘进行检测。结果平均视神经纤维数为（10.08±1.61）×10⁵，神经纤维平均直径为（0.99±0.04）μm，平均视盘面积为（2.28±0.61）mm²。视神经纤维数随神经断面面积的增加而增加，而与视盘面积无关。结论本研究为临床推测视神经损害的预后及进一步研究青光眼的神经损害奠定了一定的基础。(中华眼底病杂志,1999,15:16-19)     

Preperimetric glaucoma diagnosis by confocal scanning laser tomography of the optic disc

AIM: To evaluate the ability of confocal scanning laser tomography of the optic nerve head to detect glaucomatous optic nerve damage in ocular hypertensive eyes without visual field defects. METHODS: The study included 50 normal subjects, 61 glaucoma patients with glaucomatous changes in the optic disc and visual field, and 102 "preperimetric" patients with increased intraocular pressure, normal visual fields, and glaucomatous appearance of the optic disc as evaluated on colour stereo optic disc photographs. For all individuals, confocal scanning laser tomographs of the optic nerve head were taken using the Heidelberg retina tomograph (HRT; software 2.01). RESULTS: Almost all investigated HRT variables varied significantly (p < 0.05) between the normal eyes and preperimetric glaucoma eyes with pronounced overlap between the two study groups. Corresponding to the overlap, sensitivity and specificity values were relatively low when HRT variables were taken to differentiate between normal and preperimetric glaucoma eyes. At a given specificity of 95% highest sensitivities were found for the variables "rim area in the superior disc sector" (24.8%), "nerve fibre layer thickness in the inferior disc sector" (26.5%), and "rim volume in the superior disc sector" (25.5%). A multivariate approach increased sensitivity to 42.2% at a given specificity of 95%. For the glaucoma group highest sensitivity values were reached by rim volume in the superior disc sector (73.8%) and rim area (72.1%); the multivariate approach reached 83.6%. CONCLUSIONS: Owing to pronounced overlapping between the groups, confocal scanning laser tomography of the optic nerve head has relatively low diagnostic power to differentiate between normal eyes and preperimetric glaucoma eyes. One of the reasons may be the biological interindividual variability of quantitative optic disc variables.     

Effect of retinal nerve fibre loss on the optic nerve head configuration in early glaucoma

Twenty-nine ocular hypertensive patients with an optic disc haemorrhage, normal optic discs and normal visual fields were followed in this partly retrospective study by means of sequential optic disc stereophotographs and retinal nerve fibre layer (RNFL) photographs for a period of up to 14 years (mean 5.2). During this time early structural glaucoma damage developed in 11 patients (12 eyes). RNFL photographs revealed a nerve fibre loss in 10 of the 12 cases (83%). However, even accurate cup to disc ratio measurements from disc stereophotographs enlarged 20 times showed a measurable increase of horizontal and vertical cup to disc ratios in only 33% and 42% of the pathological cases, respectively. This result indicates that haemorrhage-associated RNFL defects precede measurable changes of the optic disc configuration. Therefore, RNFL photography seems to be a useful and sensitive examination method for the detection of the earliest organic damage in glaucoma.     

Effect of aging on optic nerve appearance: a longitudinal study

AIM: To determine whether aging causes detectable changes in the appearance of the optic disc. METHODS: A retrospective longitudinal study was performed with quantitative and qualitative evaluations of digitised stereoscopic optic disc photographs of 224 eyes of 224 subjects. There were three groups: 100 normal subjects from the Framingham Eye Study, 68 glaucomatous patients followed longitudinally, and 56 normal subjects and glaucoma patients who had separate sets of disc photos taken on the same day. A disc was considered qualitatively worse if two of three experienced observers agreed that it was worse. Quantitative progression was defined as a >10% decrease in rim/disc area ratio measured with computer assisted planimetry. RESULTS: With quantitative evaluation, normal eyes (mean follow up 13 years) and same day eyes displayed no statistically significant difference in change of rim/disc area ratios (p=0.095), nor in the number of discs that progressed-five of 100 (5%) v two of 56 (4%) respectively. Glaucomatous eyes (mean follow up 9 years) showed a quantitative loss of disc rim in 24 of 68 (35%), and differed significantly from the normal eyes both in the change of rim/disc area ratio (p<0.0005) and number of discs that progressed (p<0.0005). With qualitative evaluation, the number of progressive discs in the glaucomatous eyes (31%) differed significantly (p<0. 0005) from the normal eyes (3%) and the same day eyes (0%). CONCLUSIONS: Over a period of follow up appropriate for long term outcome studies in glaucoma, there was no quantitatively or qualitatively detectable neuroretinal rim loss in normal aging optic nerves with stereoscopic optic disc photographs.     

The optic disc hemifield test

PURPOSE: To evaluate whether an optic disc hemifield test comparing the superior half of the optic disc with the inferior disc half is useful for glaucoma diagnosis. METHODS: The clinical observational study included 1268 patients with primary or secondary open-angle glaucoma and 649 normal subjects. The glaucoma group was divided into 1118 patients with glaucomatous visual field defects ("perimetric glaucoma"), and 150 patients with optic nerve head changes and normal visual fields ("preperimetric glaucoma"). Color stereo optic disc photographs were morphometrically evaluated. The optic disc area was divided into four sectors: temporal horizontal (60 degrees), superotemporal (90 degrees), inferotemporal (90 degrees), and nasal (120 degrees). Area and width of the neuroretinal rim were measured, and the ratio of superotemporal-to-inferotemporal rim area, the ratio of superior (12 o'clock)-to-inferior (6 o'clock) rim width, the difference of inferotemporal minus superotemporal rim area, and the difference of inferior rim width minus superior rim width were calculated. RESULTS: For the differentiation between the normal group and the whole glaucoma group, and for the differentiation between the normal group and the preperimetric glaucoma group, respectively, areas under the ROC curves were significantly smaller for the parameters of the optic disc hemifield test (superior-to-inferior rim width ratio: 0.448 and 0.412, respectively; and superotemporal-to-inferotemporal rim area ratio: 0.395 and 0.434, respectively) than for any other rim parameter tested such as inferotemporal rim area (0.827 and 0.745, reps.), total rim area (0.814 and 0.741, respectively), and superotemporal rim area (0.781 and 0.705, respectively). DISCUSSION: An optic disc hemifield test with the parameters superior-to-inferior rim width ratio and superotemporal-to-inferotemporal rim area ratio is not markedly helpful for the morphometric diagnosis of glaucomatous optic nerve damage, either in the preperimetric stage or in the perimetric stage of the disease.     

Scanning laser tomography to evaluate optic discs of normal eyes

PURPOSE: To investigate the effects of age, eye refraction, and disc area on topographic parameters of the optic nerve head in normal volunteers, using the Heidelberg Retina Tomograph. METHODS: Seventy-seven eyes of 77 normal volunteers were examined by scanning laser tomography. The topographic parameters analyzed were disc area, cup area, cup/disc area ratio, rim area, cup volume, rim volume, mean cup depth, maximum cup depth, cup shape measure, height variation contour, mean retinal nerve fiber layer thickness (MnRNFLT), and retinal nerve fiber layer (RNFL) cross-section area. The effect of age, refraction, and disc area on each parameter was analyzed by the multiple linear regression model. RESULTS: Significant declines in MnRNFLT and RNFL cross-section area were found with increasing age (P < .05). The mean cup depth and maximum cup depth were significantly deeper in myopic subjects (P < .05). Large discs had large cup area, cup/disc area ratio, rim area, cup volume, mean cup depth, cup shape measure (P < .01), and maximum cup depth (P < .05). The MnRNFLT was smaller in large discs (P < .01). Rim volume was unaffected by age, refraction, or disc area. CONCLUSIONS: The age, refraction, and disc area were related to several optic disc parameters obtained by the Heidelberg Retina Tomograph. Because of these relationships, care should be taken to analyze the appearance of the optic disc on the basis of these parameters in patients with glaucoma or other diseases. Rim volume appears to be a good parameter for evaluating the optic disc without considering age, refraction, or disc area.     

Human optic nerve fiber count and optic disc size.

In the optic nerve head, the optic nerve fibers are represented by the neuroretinal rim. The rim area showing a high interindividual variability is positively correlated with the optic disc size. This study was performed to address the question of whether, in addition to having a larger neuroretinal rim, eyes with large optic discs also have a higher count of optic nerve fibers compared to eyes with small optic nerve heads. Histologic semithin sections of 72 optic nerves of 56 cornea donors were histomorphometrically evaluated using a computerized image analyzer. The optic nerve fiber count increased significantly (P = 0.01) with enlarging optic disc size. The nerve fiber count was positively correlated with the retrobulbar optic nerve cross section area. It decreased with advancing age, with a mean annual loss of about 4,000 fibers. The nerve fiber density per disc area decreased with increasing optic disc area. Mean and median of the minimal nerve fiber diameter was larger in older subjects. The results may indicate that the optic nerve fiber count, and the anatomic reserve capacity in progressive optic neuropathies, are higher in eyes with large optic discs than in eyes with small optic nerve heads. The optic nerve fiber population decreased with advancing age. This is important for progression, pseudoprogression, and prognosis of optic neuropathies. Optic nerve fiber crowding is more marked in eyes with small optic discs than in eyes with large optic nerve heads. The age-related loss of predominantly small optic nerve fibers can potentiate the optic nerve atrophy in glaucoma and Alzheimer's disease, with both damaging preferentially large axons.     

Ranking of optic disc variables for detection of glaucomatous optic nerve damage

PURPOSE: To describe optic disc variables assessed by evaluation of clinical optic disc photographs and to compare sensitivity and specificity of these optic disc parameters in identifying patients with ocular hypertension who have nerve fiber layer defects and normal visual fields and patients with visual field defects. METHODS: The study included 500 normal subjects, 132 patients with ocular hypertension with retinal nerve fiber layer defects and normal visual fields (preperimetric glaucoma), and 840 patients with glaucomatous visual field defects. Color stereo optic disc photographs were morphometrically evaluated. RESULTS: Highest diagnostic power for the separation between the normal group and the preperimetric glaucoma group had the vertical cup-to-disc diameter ratio corrected for its dependence on the optic disc size, total neuroretinal rim area, rim-to-disc area ratio corrected for disc size, and cup-to-disc area ratio corrected for disc size. Diagnostic power was lower for rim area in the temporal inferior and temporal superior disc sector, cup area corrected for disc size, and horizontal cup-to-disc diameter ratio corrected for disc size. Less useful for the differentiation between the normal subjects and the preperimetric glaucoma group were size of zones alpha and beta of parapapillary chorioretinal atrophy, and ratios of neuroretinal rim width and rim area comparing various optic disc sectors with each other. CONCLUSIONS: In subjects with ocular hypertension with retinal nerve fiber layer defects and normal conventional achromatic visual fields, the vertical cup-to-disc diameter ratio corrected for optic disc size, total neuroretinal rim area, rim-to-disc area ratio, and cup-to-disc area ratio corrected for disc size are the most valuable optic disc variables for early detection of glaucomatous optic nerve damage. Correction for optic disc size is necessary for optic disc variables directly or indirectly derived from the optic cup. Parapapillary atrophy is less important in the early detection of glaucoma.     

Glaucomatous optic nerve atrophy in small discs with low cup-to-disc ratios

Glaucomatous optic nerve damage has generally been associated with high cup-to-disc ratios. Fifteen eyes of nine patients with increased intraocular pressure and glaucomatous visual field loss but low cup-to-disc ratios are reported. The optic disc area was significantly (P less than 0.01) smaller than in 429 normal subjects and 556 glaucoma patients with high cup-to-disc ratios. Parapapillary chorioretinal atrophy was significantly larger and retinal nerve fiber bundles were significantly less visible than in the normal group. The latter two parameters were not significantly different in the glaucoma groups with low and high cup-to-disc ratios when the groups were matched for mean perimetric loss. The authors conclude that in eyes with small optic discs, glaucomatous optic nerve damage may be indicated more sensitively by parapapillary changes than by cup-to-disc ratios. Glaucomatous eyes with small optic nerve heads can have misleadingly low cup-to-disc ratios.     

Correlation between neuroretinal rim and optic disc areas in normal melanoderm and glaucoma patients

BACKGROUND: To evaluate optic disc size and its relationship with neuroretinal rim areas. MATERIAL AND METHODS: The study was prospective; 400 hundred patients with 292 glaucomatous and 108 non glaucomatous were enrolled in this study.Optic disc size quantification was assessed by the use of Goldmann 3 mirror contact lens; diameter reading were adjusted by the magnification factor of the lens, squares of the disc and the cupping were calculated using an ellipse formula, the neuroretinal rim area was then obtained by reducing the cupping area from the whole optic disc area. RESULTS: The mean age of the sample was 36.80 years (sd: 15.68 years).The average value of the vertical disc diameter was 2.045 mm (sd: 0.254) for glaucoma patients and 1.966 mm (sd: 0.237) in the control group; p<0.001. Neuroretinal rim area was 1.886 mm(2) (sd: 0.675) in the glaucoma group; and 2.165 mm(2) (sd: 0.425) in the control one; p<0. 004. In the glaucoma group, 72.97% of large optic disc were found (vertical diameter over 1.90 mm); and 63.80% in the control one. In the control group, neuroretinal rim area was wider in the large optic discs compared to the small discs, p<0.001, Anova test. Neuroretinal rim area was thinner in the glaucoma large disc compared to the control, p<0.005, Student test. Meanwhile, there was no difference in the medium and the small discs in the glaucoma and control groups; p > 0.005, Student Newmann test. CONCLUSION: Neuroretinal rim areas are thinner in the large glaucoma discs compared to the non glaucoma large discs. In Africa, this parameter could be helpful in the diagnosis and survey of glaucoma patients.     

Is the nasal optic disc sector important for morphometric glaucoma diagnosis?

BACKGROUND/AIM: Since the central retinal vessel trunk usually located in the nasal optic disc sector can render difficult the delineation of the neuroretinal rim and optic disc, the aim of this study was to evaluate whether the nasal region of the optic nerve head is important, or can be left out, for the morphometric glaucoma diagnosis. METHODS: The clinical observational study included 1337 patients with primary or secondary open angle glaucoma and 649 normal subjects. The glaucoma group was divided into 1187 patients with glaucomatous visual field defects ("perimetric glaucoma"), and into 150 patients with optic nerve head changes and normal visual fields ("preperimetric glaucoma"). Colour stereo optic disc photographs were morphometrically evaluated. RESULTS: Highest diagnostic power for the separation between the normal group and the perimetric glaucoma group, and for the differentiation between the normal group and the preperimetric glaucoma group, had the sum of inferotemporal rim area plus superotemporal rim area, the sum of inferotemporal rim area plus superotemporal rim area plus temporal rim area, and the inferotemporal rim area as single parameter. The lowest diagnostic precision had the nasal rim area as single parameter or in combination with rim measurements in other disc sectors. CONCLUSION: Excluding the nasal optic disc sector does not markedly decrease the diagnostic power of morphometric optic disc analysis in glaucoma diagnosis. It may have importance for an automated computerised morphometric detection of glaucomatous optic nerve damage.     

Nerve fiber layer and optic disc fluorescein defects in glaucoma and ocular hypertension

Photographs of the optic discs and fluorescein angiograms of 31 patients with open-angle glaucoma and 43 patients with ocular hypertension were evaluated for nerve fiber layer (NFL) defects and absolute fluorescein filling defects. All of the glaucomatous eyes showed both defects. Of the 43 ocular hypertensive eyes, in which both NFL and absolute fluorescein filling defects were evaluated, 9% had only NFL defects, 19% had only fluorescein filling defects, 14% had both defects, and 58% had neither defect. The percent area of fluorescein defect in the optic disc increased with severity of NFL defect in glaucoma and ocular hypertension. This study confirms the relationship of fluorescein filling defects and NFL defects to glaucomatous abnormalities and thus the association between vascular damage to the optic nerve and axon loss in glaucoma. The earliest objective evidence of glaucomatous damage can be detected with a combination of NFL evaluation and optic disc fluorescein angiography.     

Optic disc excavation in the atrophic stage of Leber's hereditary optic neuropathy: comparison with normal tension glaucoma

BACKGROUND: Abnormal optic disc excavations are reportedly seen in patients with Leber's hereditary optic neuropathy (LHON), a mitochondrial dysfunction disease. We examined the disc morphology in the eyes of patients with LHON at the atrophic stage and compared it to that in eyes with normal-tension glaucoma (NTG). METHODS: We studied 15 LHON patients with the 11778 mutation, 15 patients with NTG, and 25 normal subjects. The optic disc morphology was analyzed by Heidelberg retinal tomography (HRT). Ten parameters of the optic disc obtained by HRT were evaluated, including the diagnostic classification of glaucoma. RESULTS: Six of the nine morphological HRT parameters of the LHON patients, the exceptions being disc area, mean cup depth, and maximum cup depth, differed significantly from those of the normals. NTG patients had a significantly greater mean and maximum cup depth than LHON patients. The HRT glaucoma diagnostic software classified 22 (73%) of the 30 optic discs in LHON patients as glaucomatous. CONCLUSION: The optic discs at the atrophic stage of LHON eyes have glaucoma-like morphological changes. However, the cups were significantly deeper in NTG than LHON. The similarity in the optic disc findings in LHON and NTG suggests that alterations in mitochondrial function may be related to optic disc excavations.     

Optic nerve damage in highly myopic eyes with chronic open-angle glaucoma

PURPOSE: To compare the amount of optic nerve damage in relation to intraocular pressure in highly myopic eyes with chronic open-angle glaucoma versus non-highly myopic eyes with chronic open-angle glaucoma. METHODS: The comparative clinical observational study included 1841 eyes of 1100 patients with chronic open-angle glaucoma. The highly myopic study group consisted of 25 eyes with a myopic refractive error equal to or higher than -8 diopters. It was subdivided into eyes with an optic disc size larger than 2.7 mm2 and eyes with an optic disc smaller than 2.7 mm2. The control group included the remaining, non-highly myopic eyes (n=1816). For all patients, a morphometric analysis of color stereo optic disc photographs was performed. Main outcome measures were morphometric optic disc measurements and intraocular pressure. RESULTS: In the highly myopic, large-optic-disc study group compared with the control group, maximal and minimal intraocular pressure readings were significantly (p<0.05) lower and neuroretinal rim area corrected for optic disc size was slightly (p=0.16) smaller. Comparing the total highly myopic study group with a control group adjusted for optic disc area, neuroretinal rim area was significantly (p=0.039) smaller in the study group with no significant difference in intraocular pressure measurements between the groups. CONCLUSIONS: At a given intraocular pressure in chronic open-angle glaucoma, optic nerve damage may be more pronounced in highly myopic eyes with large optic discs than in non-highly myopic eyes. This may suggest a higher susceptibility for glaucomatous optic nerve fiber loss in highly myopic eyes than in non-highly myopic eyes.     

Quantitative evaluation of the optic nerve head in early glaucoma

AIMS—Progressive loss of neuroretinal rim tissue is known to occur early in glaucoma and measurement of the neuroretinal rim area is possible by magnification corrected analysis of optic disc photographs (planimetry). This study was performed to determine whether the facility to distinguish between glaucomatous and normal optic discs could be improved upon by: (a) taking into account the known relation between optic disc size and neuroretinal rim area, and (b) measuring rim area in a number of segments, in order to detect focal changes.
METHODS—Planimetric examination of the optic disc photographs of 88 control subjects and 51 patients with early visual field defects was performed. In the control group, multiple linear regression analysis was performed between neuroretinal rim area and optic disc area, age, sex, eye side, refraction, and keratometry. This was repeated for the whole disc and for each of twelve 30 degree segments. Normal ranges were defined by the 98% prediction intervals of the regression analysis and the sensitivity and specificity for correct identification of optic discs in the two groups determined.
RESULTS—Multiple linear regression demonstrated significant associations between the neuroretinal rim area and optic disc area and age in normal subjects. Sensitivity and specificity for glaucoma diagnosis, using the cut off derived from the 98% prediction intervals, was 37.7% and 98.9% respectively when total neuroretinal rim area alone was considered, and 88.7% and 94.3% respectively when the 30 degree segments were included. The most frequent pattern of neuroretinal rim loss was diffuse, followed by thinning in more than one sector and then by thinning in the inferotemporal sector alone.
CONCLUSIONS—This method of optic disc analysis enables the examiner to identify glaucomatous optic discs at the stage of early perimetric loss with a high degree of precision. Optic disc photography is simple, and fundus cameras are widely available. This method for glaucoma case identification may therefore be suitable for the primary care setting as well as hospital practice.

Keywords: optic disc; glaucoma; case finding; imaging     

Detection of glaucoma-like optic discs in a diabetes teleretinal program.

BACKGROUND: Glaucoma is typically an insidious-onset disease with serious visual consequences that has been positively linked to diabetes mellitus (DM) in several studies. We assessed the sensitivity and specificity of a diabetes teleretinal program to identify the glaucoma-suspicious optic disc. METHODS: Outpatients with DM (N = 1,644) presenting to Veterans Affairs ambulatory clinics participated in a nonmydriatic digital retinal imaging (NMDRI) program. Technicians transmitted digital retinal images electronically to readers for grading and eye care recommendations. Patients were referred for ophthalmic care based on the level of diabetic retinopathy and other ocular findings, including optic nerve changes suspicious for glaucoma. We retrospectively reviewed the electronic medical records of patients labeled as glaucoma suspects (N = 175) and compared them with those of patients from the same imaging pool who were not regarded as glaucoma suspects (N = 175). Ophthalmic data obtained from a comprehensive eye examination after digital retinal imaging was used to determine which patients met predefined criteria for the optic disc suggestive of glaucoma. RESULTS: Assessment of clinical data obtained after NMDRI found that 103 of 175 (59%) glaucoma suspects had glaucoma-suspicious optic discs. In the comparison group, only 7 of 175 (4%) had glaucoma-suspicious optic discs. CONCLUSIONS: Although specificity was high (96%), modifications in diabetes teleretinal imaging programs are needed to improve the sensitivity of detecting the optic disc that is suspicious for glaucoma.     

Ability of a confocal scanning laser ophthalmoscope (TopSS) to detect early glaucomatous visual field defect

AIMS: To evaluate the ability of the confocal scanning laser ophthalmoscope (TopSS) to detect early glaucomatous visual field defect using our unique discriminant criteria. METHODS: The optic discs of 110 eyes of normal Korean subjects were examined and normal values for each variable were obtained according to the size of the optic disc. The five most sensitive optic disc variables for discriminating glaucoma were then applied to one eye of 80 Korean subjects with primary open angle glaucoma or normal tension glaucoma. Only eyes with an optic disc size of 2.0-3.0 mm(2) and a contour tilt of less than 3 degrees were included. These variables were used to develop unique discriminant criteria for detecting early glaucomatous visual field defect and their sensitivity and specificity were calculated in three groups of patients with visual field loss. RESULTS: The five most sensitive variables were half the depth area, cup/disc (C/D) ratio, total area of the neuroretinal rim (NRR), volume above, and localised thinning of the NRR. The following criteria were used to diagnose glaucoma: (1) total area of the NRR decreased and one of the other four variables abnormal, and (2) total area of the NRR normal, localised thinning of the NRR, and one of the other three variables abnormal. The sensitivity of these criteria was 89.7% in patients with a mildly impaired visual field and 100% in those with a moderately or severely impaired visual field; the specificity was 89.1%. CONCLUSIONS: The discriminant criteria used had high sensitivity and specificity in the diagnosis of glaucoma and the TopSS can be useful in the early detection of changes in the glaucomatous optic disc.