Albert Dichtl

Optic disc morphology in myopic primary open-angle glaucoma.

Abstract• Objective: To evaluate the morphology of the optic disc in highly myopic eyes with primary open-angle glaucoma. • Methods: Color stereo optic disc photographs of 44 patients with primary open-angle glaucoma and a myopic refractive error exceeding −8 diopters were morphometrically examined and compared with disc photographs of 571 patients with primary open-angle glaucoma and a myopic refractive error of less than −8 diopters. • Results: In the highly myopic group, compared to the control group, the optic disc was significantly (P<0.0001) larger, the disc shape was significantly (P<0.0005) more elongated, and the optic cup depth was significantly (P<0.0001) more shallow. The loss of neuroretinal rim was more concentric, and localized retinal nerve fiber layer defects were found significantly less frequently in the highly myopic group than in the control group. In the highly myopic group, zone beta of parapapillary atrophy was significantly (P<0.0001) larger. • Conclusion: The optic disc morphology in primary open-angle glaucoma differs significantly between highly myopic eyes and eyes with hyperopia or low to moderate myopia. The highly myopic eyes are characterized by secondary macrodiscs with elongated shape, shallow and concentric disc cupping, large parapapillary atrophy, and low frequency of localized retinal nerve fiber layer defects. Glaucomatous optic nerve damage in highly myopic eyes, compared to eyes with a normal refractive error, is more diffuse than localized.

Retinal nerve fiber layer thickness in human eyes

Abstract · Background: A study was carried out to measure the thickness of the retinal nerve fiber layer (RNFL) at the optic disc border. · Methods: RNFL thickness at the optic disc border was histomorphometrically measured on histological sections of 22 human eyes with normal optic nerves and 21 human eyes with absolute secondary angle-closure glaucoma. For three eyes with normal optic nerves, serial sections through the whole optic disc area were available. · Results: In the eyes with normal optic nerves, the RNFL at the optic disc border showed a double hump configuration with the highest mean thickness in the inferior quadrant (mean ± S.D: 266±64 µm), followed by the superior quadrant (240±57 µm), the nasal quadrant (220±70 µm), and finally the temporal quadrant (170±58 µm). In the three globes with serial sections, RNFL was thickest at the inferior disc pole (397±58 µm), followed by the superior disc pole (313±38 µm), the nasal disc pole (165±19 µm), and finally the temporal disc pole (131±15 µm). In the eyes with absolute glaucoma, mean thickness of the remainder of the RNFL was 40±18 µm with no marked differences between the disc regions. · Conclusions: In normal eyes, the RNFL shows a double hump configuration with its thinnest part at the temporal disc pole, followed by the nasal disc pole and the superior disc pole. RNFL is thickest at the inferior disc pole. In glaucomatous optic neuropathy, the inner limiting membrane moves backward about 60–100 µm at the temporal disc border, and more than 200 µm at the inferior and superior disc poles.

Visual field defect and perfusion of the juxtapapillary retina and the neuroretinal rim area in primary open-angle glaucoma

Abstract • Background: At this time little information is available about the relationship between glaucomatous visual field defects and impaired blood flow in the optic nerve head. The purpose of this study was to examine blood flow of the juxtapapillary retina and the rim area of the optic nerve head in primary open-angle glaucoma with a borderline visual defect. • Methods: Juxtapapillary retinal and neuroretinal rim area blood flow was measured by scanning laser Doppler flowmetry (SLDF). The visual field was evaluated by static perimetry (Octopus-G1). The optic nerve head was assessed on 15° color stereo photographs. We examined 116 eyes of 91 patients with POAG with controlled IOP and 66 eyes of 44 healthy individuals. The POAG group was divided into eyes with a mean defect lower than 2 dB (POAG group I) and in eyes with a mean defect equal to or greater than 2 dB (POAG group II). The mean age of POAG group I and POAG group II was 55±11 years and 57±10 years, respectively. The mean age of the control group was 45±15 years. The eyes of POAG group I had an average C/D ratio of 0.71±0.18 with an average mean defect of the visual field of 0.97±0.68 dB; the eyes of POAG group II had an average C/D ratio of 0.80±0.17 with an average mean defect of the visual field of 8.2±6.0 dB. The intraocular pressure on the day of measurement in POAG group I was 18.2±3.7 mmHg, in POAG group II 17.6±4.0 mmHg, and in the control group 15.1±2.5 mmHg. For statistical analysis, age-matched groups of 32 normal eyes of 32 subjects (mean age 52±10 years) were compared to 18 glaucomatous eyes of 18 patients (POAG group I, mean age 55±11 years) and 59 glaucomatous eyes of 59 patients (POAG group II, mean age 55±10 years). • Results: In the eyes of POAG group I and POAG group II, both juxtapapillary retinal blood flow and neuroretinal rim area blood flow were significantly decreased compared to an age-matched control group: neuroretinal rim area “flow” POAG group I −65%, POAG group II −66%; juxtapapillary retina “flow” POAG group I −52%, POAG group II −44%. All eyes of the POAG group I (MD<2 dB) and 56 of 61 eyes of the POAG group II (MD>=2 dB) showed a retinal perfusion lower than the 90% percentile of normal blood flow. We found no correlation between reduction of juxtapapillary or papillary blood flow and mean defect in POAG eyes. • Conclusion: Glaucomatous eyes with no defects or borderline visual field defects as well as glaucomatous eyes in an advanced disease stage show significantly decreased optic nerve head and juxtapapillary retinal capillary blood flow.

Evaluation of the retinal nerve fiber layer

In normal eyes, the retinal nerve fiber layer (RNFL) is usually best visible in the inferior temporal part of the fundus, followed by the superior temporal region, the nasal superior region and the nasal inferior region. This distribution correlates with the configuration of the neuroretinal rim, the diameter of the retinal arterioles, the location of the foveola, and the lamina cribrosa morphology. With increasing age, the RNFL visibility decreases diffusely without preferring special fundus regions and without the development of localized defects. With all optic nerve diseases, the visibility of the RNFL is decreased in addition to the age-related loss, in a diffuse and/or a localized manner. The localized defects are wedge-shaped and not spindle-like defects, running toward or touching the optic disk border. Typically occurring in about 20% of all glaucoma eyes, they can be found also in other ocular diseases, such as optic disk drusen, toxoplasmotic retinochoroidal scars, longstanding papilledema or optic neuritis due to multiple sclerosis. Since they are not present in normal eyes, they almost always signify an abnormality. RNFL evaluation is especially helpful for early glaucoma diagnosis and in glaucoma eyes with small optic disks. In advanced optic nerve atrophy, other examination techniques, such as perimetry, may be more helpful for following optic nerve damage. Considering its great importance in the assessment of optic nerve anomalies and diseases and taking into account the feasibility of its ophthalmoscopic evaluation using green light, the retinal nerve fiber layer should be examined during any routine ophthalmoscopy.

Histomorphometry of the optic disc in highly myopic eyes with absolute secondary angle closure glaucoma

AIM To evaluate histomorphometrically the optic nerve head in highly myopic eyes with absolute secondary angle closure glaucoma. METHODS Optic disc sections of 16 highly myopic eyes with an axial length of more than 26 mm and of 19 eyes with an axial length of less than 26 mm were histomorphometrically evaluated. All eyes had been enucleated due to painful absolute secondary angle closure glaucoma. RESULTS In the highly myopic eyes compared with the non-highly myopic eyes, mean optic disc diameter was significantly larger (mean 2.33 (SD 0.55) mm versus 1.77 (0.50) mm; p=0.01), and the optic cup was significantly shallower (optic cup depth 0.34 (0.29) mm versus 0.63 (0.23) mm; p=0.03). The peripapillary scleral ring was significantly broader (0.58 (0.65) mm versus 0.08 (0.06) mm; p=0.001), and the β zone (0.83 (0.74) mm versus 0.28 (0.25) mm; p=0.006) of the parapapillary chorioretinal atrophy was significantly larger in the highly myopic eyes. CONCLUSIONS The results of the present study agree with biomorphometric data of the optic nerve head in highly myopic eyes with glaucoma. In the highly myopic group, a markedly enlarged peripapillary scleral ring characterised by absence of Bruch’s membrane and choriocapillaris contributes in addition to α and β zone to the parapapillary atrophy.

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

PURPOSE To compare laser tomographic scanning evaluation with photographic measurement of size and shape of the neuroretinal rim. METHODS 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. RESULTS 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. CONCLUSIONS 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.

Echographic Measurement of Optic Nerve Thickness Correlated With Neuroretinal Rim Area and Visual Field Defect in Glaucoma

PURPOSE To determine whether echographic measurements of the pial diameter of the optic nerve are significantly correlated with glaucomatous changes of the optic disk and retinal nerve fiber layer. METHODS In 31 patients with primary open-angle glaucoma and 16 normal control subjects, optic nerve thickness was determined by measuring the maximal pial diameter of the optic nerve using standardized A-scan echography. The optic disks were morphometrically examined using color stereo photographs, and the retinal nerve fiber layer was assessed using wide-angle red-free fundus photographs. RESULTS Optic nerve thickness as measured echographically decreased significantly (P < .001) with decreasing neuroretinal rim area, diminishing visibility of the retinal nerve fiber layer, narrowing of the retinal arterioles, enlarging parapapillary atrophy, and increasing mean visual field defect. In an intraindividual bilateral comparison, side differences in the optic nerve thickness were significantly correlated with side differences in neuroretinal rim area (P < .0001), diameter of retinal arterioles (P = .003), and visual field defect (P < .0001). In the differentiation of normal and glaucomatous eyes, sensitivity and specificity were higher for echographic measurements of the optic nerve thickness than for parapapillary atrophy and diameter of retinal arterioles but worse than for determination of the neuroretinal rim area. CONCLUSIONS Echographic measurements of optic nerve thickness are significantly correlated with glaucomatous changes of the optic disk and retinal nerve fiber layer. In patients with opaque media, echographic measurement of optic nerve thickness may be helpful in distinguishing among normal eyes, eyes with medium advanced glaucoma, and eyes with markedly progressed glaucoma.

Course of the optic nerve fibers through the lamina cibrosa in human eyes

Abstract• Background: This study investigated whether regional variations in the course of the optic nerve fibers through the lamina cribrosa may be one of the reasons why the local susceptibility for glaucomatous optic nerve fiber loss differs among the various regions of the optic disc. • Methods: The study included 34 human eyes enucleated because of a malignant melanoma of the peripheral choroid without involvement of the anterior chamber angle or the optic nerve. Anterior-posterior sections through the pupil and the optic disc were histomorphometrically evaluated. In the central region and the peripheral part of the optic disc, we measured the thickness of the lamina cribrosa and the length of the lamina cribrosa “channels” through which the nerve fibers pass.• Results: In the peripheral parts of the disc, compared with its central region, the lamina cribrosa was significantly thicker (P<0.0001, Wilcoxon test), the lamina cribrosa “channels” with the nerve fibers passing through were significantly longer (P<0.0001), and the ratio of length of the fiber “channels” to the thickness of the lamina cibrosa was significantly higher (P=0.0001).• Conclusion: The lamina cribrosa is thicker and the course of the optic nerve fibers through the lamina cribrosa is more curvilinear in the disc pheriphery than in the disc center. These variations in the anatomy of the lamina cribrosa may be one of several factors influencing the regional susceptibility for glaucomatous optic nerve fiber loss within the optic nerve head.

Optic disc morphology in pigmentary glaucoma

AIM To evaluate the morphology of the optic nerve head in eyes with pigmentary glaucoma. METHODS Colour stereo optic disc photographs of 62 patients with pigmentary glaucoma and 566 patients with primary open angle glaucoma were morphometrically evaluated. By prestudy selection, mean visual field defect and neuroretinal rim area were not significantly different between the two groups (p=0.89 and p=0.45). RESULTS The pigmentary glaucoma group did not vary significantly (p >0.10) from the primary open angle glaucoma group in size and shape of the optic disc, configuration of neuroretinal rim, depth of optic cup, area of alpha zone of parapapillary atrophy, diameter of retinal vessels at the disc border, and frequency of disc haemorrhages and localised retinal nerve fibre layer defects. The beta zone of parapapillary atrophy was slightly, but not statistically significantly (p=0.06), smaller in the pigmentary glaucoma group. The mean maximal intraocular pressure and mean intraocular pressure amplitude were significantly (p<0.001) higher in the pigmentary glaucoma group. CONCLUSIONS In contrast with the characteristic morphology of the anterior segment and despite significantly higher intraocular pressure peaks and a larger pressure amplitude, eyes with pigmentary glaucoma compared with eyes with primary open angle glaucoma do not show a pathognomonic morphology of the optic disc and retinal nerve fibre layer. The slightly smaller beta zone of parapapillary atrophy may correspond to higher intraocular pressure in pigmentary glaucoma.

Advances in the assessment of optic disc changes in early glaucoma.

&NA; Looking for early glaucomatous changes in the morphology of the optic disc and retinal nerve fiber layer, ocular hypertensive subjects should be checked to determine 1) whether the neuroretinal rim has its characteristic physiologic form with its largest parts in the inferior and superior disc regions and its smaller part in the temporal disc sector; 2) whether zone &bgr; of the parapapillary chorioretinal atrophy is present or whether zone &agr; is abnormally large; 3) whether the visibility of the retinal nerve fiber layer is diffusely reduced; and 4) whether localized defects of the retinal nerve fiber layer can be detected. Usually not occurring in normal eyes, an optic disc hemorrhage also indicates abnormality. These variables can be evaluated in every routine ophthalmoscopic examination, or by applying sophisticated techniques such as the scanning laser tomography and measurement of the height and contour of the parapapillary retinal nerve fiber layer.