Central Retinal Vessels Research Articles

Finite Element Modeling of Optic Nerve Head Biomechanics

Biomechanical factors have been implicated in the development of glaucomatous optic neuropathy, particularly at the level of the lamina cribrosa. The goal of this study was to characterize the biomechanics of the optic nerve head using computer modeling techniques. Several models of the optic nerve head tissues (pre- and postlaminar neural tissue, lamina cribrosa, central retinal vessel, sclera, and pia mater) were constructed. Stresses, deformations, and strains were computed using finite element modeling for a range of normal and elevated intraocular pressures. Computed retinal surface deformations were compared with measured deformation patterns in enucleated human eyes. A sensitivity analysis was performed in which tissue properties and selected geometric features were varied. Acute IOP-induced deformation of the vitreoretinal interface was highly dependent on optic cup shape but showed a characteristic "W-shaped" profile that did not match the deformation of the anterior surface of the lamina cribrosa. The central retinal vasculature had surprisingly little effect on optic nerve head biomechanics. At an IOP of 50 mm Hg, strains (fractional elongation) in the lamina cribrosa averaged 4% to 5.5%, dependent on model geometry, with maximum strains up to 7.7%. Strains in the lamina cribrosa were more dependent on scleral stiffness, scleral thickness, and scleral canal diameter than on lamina cribrosa stiffness and optic cup shape. Computed levels of strain in the lamina cribrosa are biologically significant and capable of contributing to the development of glaucomatous optic neuropathy, even without considering the probable accentuating effect of the lamina cribrosa's microarchitecture. Depending on optic cup shape, IOP-induced deformation of the vitreoretinal interface may not match lamina cribrosa deformation. This finding implies that scanning laser tomography has limited ability to estimate lamina cribrosa deformation when imaging the anterior topography of the optic nerve head. Biomechanical effects in the lamina cribrosa depend strongly on scleral properties.

Regional Optic Nerve Damage in Experimental Mouse Glaucoma

To assess the relationship between regional variation of axon loss and optic nerve head anatomy in laser-induced experimental glaucoma in the mouse. Experimental glaucoma was induced unilaterally in eight NIH Swiss black mice. Intraocular pressure (IOP) was measured for 12 weeks, and the mice were killed. The eyes were enucleated, and both optic nerves were dissected and processed conventionally for electron microscopy. Low- and high-magnification images of the optic nerve cross sections 300 microm posterior to the globe were collected systematically and masked before analysis. For each nerve, cross-sectional area was measured in low-magnification micrographs. Axon number and density were determined in the high-magnification micrographs. Loss of axonal density was compared between the superior and inferior and nasal and temporal areas of the optic nerve cross section. Additional cross-section micrographs were collected at 10- or 20-microm intervals throughout the optic nerve head. In the treated (glaucoma) eyes, mean IOP was 44% higher than that in the control eyes. The optic nerve cross-sectional area, mean axonal density, and total axonal number were significantly less than those in the control eyes (P < 0.01 for each). Axon loss in the superior optic nerve was greater than in the inferior optic nerve in each glaucomatous eye (P = 0.012). The ratio of axonal density in the superior and inferior optic nerve (superior-to-inferior [S/I] ratio) in all treated eyes was <1.0 and significantly lower than that in the control eyes (P = 0.012). The central retinal vessels occupied approximately 20% of the central optic nerve head cross-sectional area, gradually shifted position ventrally as they progressed toward the scleral foramen (the mouse does not have a lamina cribrosa), and exited the inferior retrobulbar optic nerve adjacent to the posterior of the globe. Ocular hypertension in the mouse eye sufficient to cause optic nerve damage induces preferential loss of superior optic nerve axons. Optic nerve axon loss appeared less among the axons that were near the major optic nerve blood vessels at the scleral foramen. Topographic differences in optic nerve axon loss should be considered when evaluating optic nerve damage in experimental laser-induced glaucoma in the mouse.

Limitations of Color Doppler Sonography in the Imaging of Ocular Vessels

To describe a case where detection of blood flow in the central retinal artery and the central retinal vein was limited by an artifact evoked by the optic disc drusen. METHODS Case report. During color Doppler sonography, examination of optic disc drusen may generate an artifact--the so-called twinkling artifact--which can simulate blood flow and make evaluation of the central retinal vessels impossible. Twinkling artifact does not allow evaluation of color Doppler sonography in the imaging of ocular vessels.

Ophthalmodynamometry in eyes with dilated episcleral veins.

To determine the central retinal vessel collapse pressure in patients with dilated episcleral veins. This clinical noninterventional comparative study included a study group of 10 eyes (6 patients) with dilated episcleral veins, and a control group consisting of 50 eyes of 40 patients with cataract or refractive problems. With topical anesthesia, a Goldmann contact lens fitted with a pressure sensor in its holding ring was placed onto the cornea. Pressure was asserted onto the globe by pressing the contact lens, and the pressure value at the time when the central retinal artery and vein started pulsating was noted as central retinal artery and vein collapse pressure. Central retinal vein collapse pressure was significantly higher (P<0.001) in the study group with dilated episcleral veins than in the control group (37.9 +/- 33.8 vs 5.1 +/- 8.4 relative units [RU]). In the central retinal artery, there was not significant difference in diastolic collapse pressure measured between the study and control groups (78.2 +/- 22.8 vs 74.2 +/- 18.8 RU, respectively; P = 0.74). As measured by a new ophthalmodynamometer with biomicroscopic visualization of the central retinal vessels during the examination, the central retinal vein collapse pressure measurements were significantly higher in eyes with dilated episcleral veins than in control eyes. Ophthalmodynamometric estimation of the central retinal vein collapse pressure may be helpful in the assessment of patients with dilated episcleral veins.

Influence of cilioretinal arteries on neuroretinal rim and parapapillary atrophy in glaucoma.

The pattern of neuroretinal rim loss and increase in the area of parapapillary atrophy in glaucoma depend on the localization of the central retinal vessel trunk in the lamina cribrosa. The purpose of the present study was to determine whether, in a similar way, the pattern of rim loss and progression of parapapillary atrophy are influenced by the presence and position of cilioretinal arteries. Color stereo optic disc photographs (15 degrees) for morphometric evaluation of the optic nerve head were used to compare the appearance of the optic disc in 41 patients exhibiting unilateral or bilateral cilioretinal arteries in the temporal horizontal disc region with the optic disc morphology of 127 patients without cilioretinal arteries. The areas of the neuroretinal rim and alpha and beta zones of parapapillary atrophy were measured in the total disc and in four disc sectors. Eyes with and eyes without cilioretinal arteries did not differ significantly in the areas of neuroretinal rim and alpha and beta zones of parapapillary atrophy, when measured in the whole optic disc and in the four disc sectors separately; in ratios of the temporal horizontal area to total area of rim and parapapillary atrophy; and in the ratio of temporal horizontal rim area-to-nasal rim area, neither in an interindividual comparison nor in an intraindividual intereye comparison. In contrast to the position of the central retinal vessel trunk, presence and position of cilioretinal arteries do not markedly influence the pattern of neuroretinal rim loss and progression of parapapillary atrophy in glaucoma.

Luminal characteristics of central retinal vessels in the anterior optic nerve of the young human.

To study the luminal characteristics of the central retinal vessels of young humans where the vessels pass through the anterior optic nerve. Serial sections of nine central retinal arteries (CRAs) and 13 central retinal veins (CRVs) from 12 eyes of 12 young donors (aged 20-29 years) without known ocular disease or anatomic malformation were examined by image analysis to determine their luminal dimensional differences right at, anterior to, and posterior to the lamina cribrosa. The average values of the mean area of the CRAs in the prelaminar, laminar, and retrolaminar portions were 16.5 x 10(3) microm2, 17.2 x 10(3) microm2, and 15.2 x 10(3) microm2, and mean perimetric lengths were 541 microm, 528 microm, and 492 microm, respectively. Differences were detected in perimetric length and theoretical luminal area between the laminar and retrolaminar portions, but not the prelaminar and laminar portions. The average values of the mean area of the CRVs in the prelaminar, laminar, and retrolaminar portions were 24.6 x 10(3) microm2, 13.3 x 10(3) microm2, and 7.8 x 10(3) microm2, and mean perimetric lengths were 689 microm, 544 microm, and 411 microm, respectively. There were marked differences between the prelaminar and laminar values and between the laminar and retrolaminar values in terms of the perimetric lengths and theoretical luminal areas. The results suggest that the resistance of blood flow in CRAs decreases when the blood enters the eye. The gradual constriction of CRVs from the prelaminar to the retrolaminar portion may act as a throttle mechanism in controlling the outflow of the blood and in maintaining the patency of the retinal venules and capillaries.

Pseudoexfoliation syndrome in eyes with ischemic central retinal vein occlusion

To determine histopathologically the prevalence of pseudoexfoliation (PEX) material in eyes enucleated secondary to ischemic central retinal vein occlusion (CRVO) and to evaluate eyes with PEX material in the anterior segment and CRVO ultrastructurally for PEX deposits in the vicinity of central retinal vessels. These deposits could explain an association of CRVO and PEX. All surgically enucleated eyes with secondary angle closure glaucoma due to rubeotic iris secondary to ischemic CRVO (1981-1998) available were re-analyzed light microscopically for the presence of PEX in the anterior segment (n=120; 76.9+/-8.5 years [range: 51-91]). Eyes with PEX in the anterior segment and available optic nerve cross sections were examined by electron microscopy for PEX material in the retrolaminar (n=7) and intralaminar central retinal vessels (n=3). All eyes surgically enucleated because of malignant melanoma of the choroid aged 70 years and older (1981-1998) with sections available served as age-matched controls (n=107; 76.4+/-5 years [range: 70-91]). PEX material was present light microscopically in the anterior segment in 12 of 120 eyes with CRVO (10%) compared to 2 of 107 age-matched eyes with choroidal malignant melanoma (1.9%; p<0.05). Electron microscopically, neither structural alterations of the vessel wall nor PEX deposits were found in association with central retinal vessels both in the intra- and retrolaminar areas in any of the 7 eyes with PEX in the anterior segment and CRVO analyzed. Histopathologically, PEX is significantly more common in eyes enucleated secondary to CRVO compared to eyes enucleated because of an intraocular tumor. This most likely is due to the secondary open angle glaucoma in eyes with PEX as a known risk factor for CRVO. According to the small number of optic nerves analyzed here, there seems to be no morphologically evident PEX vasculopathy in the central retinal vessels both within and immediately behind the lamina cribrosa in eyes with PEX in the anterior segment and CRVO potentially causing retinal venous thrombosis.

Diagnosis and pathogenesis of glaucomatous optic neuropathy: morphological aspects1111Supported by Deutsche Forschungsgemeinschaft (SFB 539)

Glaucomatous optic neuropathy is classified by morphologic changes in the intrapapillary and parapapillary region of the optic nerve head and the retinal nerve fibre layer. These changes can be evaluated using descriptive optic nerve head variables which are the size and shape of the optic disc; size, shape and pallor of the neuroretinal rim; size of the optic cup in relation to the area of the disc; configuration and depth of the optic cup; cup-to-disc diameter ratio and cup-to-disc area ratio; position of the exit of the central retinal vessel trunk on the lamina cribrosa surface; presence and location of splinter-shaped haemorrhages; occurrence, size, configuration and location of parapapillary chorioretinal atrophy; diffuse and/or focal decrease of the diameter of the retinal arterioles; and visibility of the retinal nerve fibre layer. Assessment of these variables is useful for the early detection of glaucomatous optic nerve damage, to follow-up patients with glaucoma, to differentiate various types of the chronic open-angle glaucomas, and to get hints for the pathogenesis of glaucomatous optic nerve fibre loss.

Morphological variations of the peripapillary circle of Zinn–Haller by flat section

AIMSTo evaluate the morphometric and morphological variations of the circle of Zinn–Haller (CZH) in the human eye.METHODS42 human enucleated eyes were used in this study. After transverse flat thick sections...

Effect of an internal carotid stenosis on orbital blood velocity.

To examine how an internal carotid artery (ICA) stenosis influences the orbital blood velocity and to determine which velocity parameters are most useful. The study group comprised 94 randomly selected patients examined with orbital US; most of the patients had a carotid artery stenosis. There were 58 men and 36 women, ranging in age from 22 to 88 years with a mean age of 63.1 years. The ICA stenosis grade was determined with carotid US. Peak systolic (Vp) and end-diastolic blood velocities, systolic acceleration, mean velocity, pulsatile index (PI) and resistance index (RI) were measured within the central retinal artery (CRA) and the ophthalmic artery (OA), and peak velocity was measured within the central retinal vein (CRV). The area under the ROC curve was used to compare the outcome of diagnostic tests. Only a severe (> or =80%) ICA stenosis decreased orbital blood velocity significantly, while milder stenoses did not cause significant flow decrease or side differences. According to ROC curve analysis, the threshold values giving the highest accuracy in detecting a > or =80% ICA stenosis were Vp < or =0.08 cm/s for the CRA and Vp < or =0.14 cm/s for the OA. The sensitivities for detecting a > or =80% ICA stenosis were 45% for Vp CRA and 60% for Vp OA. Systolic acceleration also decreased in severe stenoses, but RI, PI and velocity in the CRV did not correlate with ICA pathology. Reversal of OA flow was seen in 92% of ICA occlusion and in 47% of severe ICA stenosis. Orbital Doppler combined with carotid Doppler can be helpful in the diagnosis of the ocular ischaemic syndrome and in the evaluation of whether the symptoms are related to occlusion of the ophthalmic or central retinal vessels or are a consequence of carotid artery stenosis.

Exit of the retinal central vascular trunk and extent of para-papillary atrophy

To evaluate whether the position of the central retinal vessel trunk exit on the lamina cribrosa spatially correlates with the location of parapapillary atrophy in glaucoma. Color stereo optic disc photographs of 79 patients with primary or secondary open-angle glaucoma and 53 normal subjects were morphometrically evaluated. We determined the position of the central retinal vessel trunk exit on the lamina cribrosa surface and measured the area of parapapillary atrophy in four 90 degrees quadrants. After correction for normal values, the beta zone area of parapapillary atrophy in the glaucoma eyes was significantly larger, when measured in the disc quadrant most distant to the central retinal vessel trunk exit than as if measured in the quadrant containing the vessel trunk exit. Position of the central retinal vessel trunk exit on the lamina cribrosa influences the location of parapapillary atrophy in glaucoma. The longer the distance to the central retinal vessel trunk exit, the more enlarged is parapapillary atrophy.

P–378 - A novel method for evaluation of drug action on rat central retinal blood vessels

P–378 - A novel method for evaluation of drug action on rat central retinal blood vessels

Dysversion of the optic disc and axial length measurements in a presumed amblyopic population

Purpose: Our purpose was to evaluate anatomic variations of eyes presumed to be amblyopic. Method: Computer imaging and photography of the optic discs of 205 amblyopic subjects were performed and the axial lengths of 183 of the subjects were measured. The paired optic nerve images were evaluated for symmetry of disc contours and orientation of central blood vessels to detect optic nerve head dysversion. Dysversion of the optic nerve head, which is also referred to as segmental hypoplasia, is a congenital disorder characterized by the central retinal vessels emerging temporal to the vertical midline of the disc and being directed nasally or the nerve head tilting in a vertical direction resulting in a downward or oblique tilting of the discs with the blood vessels emerging at the superior or inferior disc rim. Results: Ninety-three subjects had optic nerve dysversion. There was a greater degree of anisometropia ( P ≤ .004) in subjects with dysversion (anisometropia factor of 2.51 ± 2.15) than in the subjects with symmetric discs (anisometropia factor of 1.76 ± 1.63). Axial lengths of the amblyopic eyes were significantly smaller ( P < .0001) than those of the nonamblyopic eyes. There was no statistical difference ( P ≤ .879) in length between amblyopic eyes with dysversion and those with symmetric discs. Conclusion: Optic disc dysversion was identified in 45.4% of patients who were previously assumed to be amblyopic. There are anatomic malformations in the eyes of a significant proportion of the presumed amblyopic population. This suggests that, in these individuals, congenital peripheral factors rather than impaired cortical development may be responsible for decreased unilateral acuity.

Ocular Blood Flow Velocities in Patients With Proliferative Diabetic Retinopathy After Panretinal Photocoagulation

Color Doppler imaging allows for simultaneous two-dimensional anatomical imaging and Doppler measurement of blood-flow velocity. Because hemodynamic changes have been seen in diabetic patients after photocoagulation by other techniques, the author compared 25 eyes of 25 patients with proliferative diabetic retinopathy before and 6 months and 1 year after panretinal photocoagulation with a matched control group of 30 eyes of 30 healthy volunteers. The ophthalmic artery, short posterior ciliary artery, central retinal vessels, and vortex veins of all patients were examined, and the systolic, diastolic, and mean arterial velocities were measured. Panretinal photocoagulation was performed with these parameters: 800-1000 spots, 0.1 second, 500 μm argon laser. The blood velocity was significantly lower in diabetic patients than in normals in the ophthalmic artery and the central retinal artery. After treatment, blood-flow velocities were significantly lower than before photocoagulation in the ophthalmic artery, the central retinal artery and the central retinal vein. No statistically significant differences were found between 6 months and 1 year after panretinal photocoagulation. No significant correlations were found between age and blood velocities in diabetics and healthy volunteers. Eyes with proliferative diabetic retinopathy showed lower ocular perfusion velocities than normals in the ophthalmic artery and the central retinal artery. Photocoagulation resulted in a reduction in ocular bloodflow velocities in the ophthalmic artery, the central retinal artery and the central retinal vein; these values did not change significantly during 1 year of follow-up.

Comparison Between Tomographic Scanning Evaluation and Photographic Measurement of the Neuroretinal Rim

To compare laser tomographic scanning evaluation with photographic measurement of size and shape of the neuroretinal rim. For 25 normal eyes and 32 glaucomatous eyes, the optic disks were examined with the Heidelberg Retina Tomograph (software version 1.11) for confocal laser tomographic scanning evaluation, and color stereoscopic optic disk photographs for planimetric measurements. Area and width of the neuroretinal rim were determined as percentages of the disk area and diameter, respectively. For the normal and glaucomatous eyes, the tomographic results compared with the photographic measurements disclosed significantly larger values for the relative width and relative area of the neuroretinal rim. The differences between both methods were most marked in the nasal part of the optic disk and least marked in the temporal disk region. The relative differences increased significantly (P < .05) with increasing degree of glaucomatous optic nerve damage. In normal and glaucomatous eyes, the Heidelberg Retina Tomograph determines the neuroretinal rim, expressed as percentage of optic disk measurements, to be significantly larger than when the rim is evaluated on optic disk photographs. Because parts of the central retinal vessel trunk are defined as neuroretinal rim in the algorithm of the Heidelberg Retina Tomograph, the differences between Heidelberg Retina Tomograph measurements and photographic determinations of the rim are largest in the nasal disk region and smallest in the temporal disk area. The neuroretinal rim shape and neuroretinal rim area differ appreciably between the two methods. These differences increase with increasing degree of glaucomatous optic nerve damage.

Ocular blood flow velocities in patients with proliferative diabetic retinopathy after scatter photocoagulation. Two years of follow-up.

Color Doppler imaging allows for simultaneous two-dimensional anatomic imaging and Doppler measurement of blood flow velocity. Because hemodynamic changes have been seen in diabetic patients after photocoagulation by other techniques, the authors compared 25 eyes with proliferative diabetic retinopathy before, 6 months after, 1 year after, and 2 years after panretinal photocoagulation with a matched control group of 30 healthy volunteers (55 eyes). The ophthalmic artery, short posterior ciliary artery, central retinal vessels, and vortex veins of all patients were examined, and the systolic, and diastolic, and mean arterial velocities were measured. Panretinal photocoagulation was performed with these parameters: 800-1000 spots, 0.1 second, 500-microns argon laser. Student's t test revealed that the perfusion velocity was significantly lower in diabetic patients than in healthy controls (V systolic in the ophthalmic artery: 31.7 +/- 6.7 cm/s vs. 36.6 +/- 7.0 cm/s, respectively, P = 0.03). After treatment, blood flow velocities were significantly lower than before photocoagulation (V systolic in the ophthalmic artery: 6 months after treatment, 26.9 +/- 7.2 cm/s, P = 0.018; 1 year after photocoagulation, 25.5 +/- 7.0 cm/s, P = 0.009; and 2 years after photocoagulation, 25.7 +/- 6.8 cm/s, P = 0.01). No statistically significant differences were found between 6 months, 1 year, and 2 years after panretinal photocoagulation. No significant correlations were found between patient age and blood velocities in diabetics and healthy volunteers. Eyes with proliferative diabetic retinopathy showed lower ocular perfusion velocities than controls. Photocoagulation resulted in a reduction in ocular blood flow velocities; these values did not change during 2 years of follow-up.

High resolution magnetic resonance imaging of the anterior visual pathway in patients with optic neuropathies using fast spin echo and phased array local coils.

High resolution MRI of the anterior visual pathways was evaluated using frequency selective fat suppressed fast spin echo (FSE) sequences in conjunction with phased array local coils in patients with optic neuropathies. Fifteen normal controls and 57 patients were examined. Coronal T2 weighted fat suppressed FSE images were obtained in 11 minutes with an in plane resolution of 0.39 x 0.39 mm. The optic nerve and its sheath containing CSF were clearly differentiated. Central retinal vessels were often visible. In demyelinating optic neuritis and in anterior ischaemic optic neuropathy high signal within the nerve was readily delineated. Meningiomas and gliomas involving the optic nerve were precisely visualised both in the orbit and intracranially. Extrinsic compression of the optic nerves was readily visualised in carotid artery ectasia and dysthyroid eye disease. Enlarged subarachnoid spaces around the optic nerves were demonstrated in benign intracranial hypertension. High resolution MRI of the anterior visual pathway represents an advance in the diagnosis and management of patients presenting with optic neuropathy.

Color Doppler US of the orbit.

Color Doppler imaging of the orbit shows promise in evaluation of several types of orbital abnormalities. The most promising use is for evaluation of vascular disorders. Screening for orbital varices and cavernous-carotid fistulas is easily accomplished. Color Doppler imaging can also be useful in diagnosis of ocular ischemia, central retinal vessel occlusion, and anterior ischemic optic neuropathy. In cases of inflammatory disease, it may be helpful in searching for complications of infection and in monitoring the size of fluid collections. In cases of tumors, color Doppler imaging can be used to monitor lesion size and in surgical planning. More work needs to be done to determine the role of color Doppler imaging in evaluation of trauma and congenital abnormalities. An understanding of the basic anatomy of the orbit, examination techniques, and common disease processes in the orbit will allow the radiologist to offer this potentially valuable modality to referring clinicians.

Optic Disk Risk Factors for Nonarteritic Anterior Ischemic Optic Neuropathy

The anatomic characteristics of a relatively small optic nerve head, absent to small physiologic cup, abnormal branching pattern of central retinal vessels, and a lush nerve-fiber bundle layer elevating the disk margins are associated with the occurrence of certain ischemic disease states. These diseases include the following: (1) nonarteritic anterior ischemic optic neuropathy, (2) anterior ischemic optic neuropathy of the young, (3) the papillopathy in patients with juvenile insulin-dependent diabetes mellitus, and (4) Leber's hereditary optic neuropathy. The finding of such a disk at risk should signal the possible later development of visual dysfunction. Ordinarily, when an ophthalmologist discusses risk factors in relationship to the optic disk, the topic is that of open-angle glaucoma and the predictability of the ultimate development of visual field loss. In the early 1980s, Hoyt suggested that certain disk characteristics may predispose an individual to the development of nonarteritic anterior ischemic optic neuropathy (Hoyt, W. F., unpublished data, presented at the Rocky Mountain Neuro-Ophthalmologic Society Meeting, February 1982). Specifically, in these cases he noted that the unaffected eye has a small or absent physiologic cup. Several investigators went on to confirm Hoyt's observation that these crowded disks are at risk for developing nonarteritic anterior ischemic optic neuropathy.! The hallmarks of the disk at risk are as follows: (1) relatively small optic nerve head, (2) absent to small physiologic cup, (3) increased number of branches of the central retinal vessels within the disk, and (4) a normal, healthy-appearing nerve-fiber bundle layer with heaping up of at least the superior, nasal, and inferior fibers (Fig. 1). These disks are similar in many ways to those described by Rosenberg, Savino, and GlaserS,6 as being characteristic of pseudopapilledema. Presumably, a small physiologic cup is the

Shape of the neuroretinal rim and position of the central retinal vessels in glaucoma.

Glaucomatous neuroretinal rim loss can occur in a sequence of sectors with the temporal inferior disc sector as the first and the nasal superior disc sector as the last to be affected. This study evaluated whether the position of the central retinal vessel trunk is correlated with this pattern of glaucomatous rim loss. Morphometrically stereo colour optic disc photographs of 157 glaucomatous eyes and 67 normal eyes were checked. In the normal and glaucomatous eyes, the central retinal vessel trunk was located eccentrically in the upper nasal quadrant of the optic disc. Taking into account the vertically oval disc shape, the distance to the central vessel trunk was largest for the temporal inferior disc region and shortest for the nasal superior disc area. An abnormal form of the glaucomatous neuroretinal rim was found in eyes with an atypical location of the retinal vessel trunk. Also in these glaucomatous eyes, the rim loss was usually most and least marked in that sector with the longest and shortest distance, respectively, to the central retinal vessel trunk. One could infer that the sequence of rim loss in glaucoma is dependent upon the distance of the region to the central retinal vessel trunk; the further away the region from the retinal vessel trunk, the more likely it is to be affected by rim loss. This suggest that the distance from the central retinal vessels is one factor among others that is correlated with the regional vulnerability of the neuroretinal rim to the glaucomatous process.