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Optic Disc Parameters (optic + disc_parameter)

Distribution by Scientific Domains

Medical Sciences	100%

Selected Abstracts

Measurement of optic disc parameters on digital fundus photographs: algorithm development and evaluation

ACTA OPHTHALMOLOGICA, Issue 8 2008
Herman Bartling
Abstract. Purpose:, To develop and evaluate a simple and rapid algorithm for optic disc measurements on digital fundus photographs, relying on the macula,disc centre distance as a reference when converting length expressed in pixels to metric distance. Methods:, Measurements were performed on fundus photographs from 68 normal subjects, acquired using five different cameras. The magnification factor and actual size in ,m of 1 pixel was known for only one camera. The measurements from this camera were compared to corresponding measurements from a confocal scanning laser ophthalmoscope. Results:, Using the described algorithm, no significant differences in mean disc or cup size were observed between the tested cameras, despite differences in magnification factor (range 0.5,2.5). There were no significant differences between disc and cup measurements obtained with the confocal scanning laser ophthalmoscope and those obtained with the described algorithm in the 20 subjects examined. Conclusion:, The algorithm described in the current study provided clinically relevant measurements of optic disc parameters. The final program can be used directly on the acquired images, with the examined subject still available for re-examination. [source]

The influence of age, sex, race, refractive error and optic disc parameters on the sensitivity and specificity of scanning laser polarimetry

ACTA OPHTHALMOLOGICA, Issue 4 2004
Vital P. Costa
Abstract. Purpose:,To evaluate the influence of age, sex, race, refractive error and optic disc topography on the sensitivity and specificity of scanning laser polarimetry (SLP) in the diagnosis of glaucoma. Methods:,A total of 88 normal individuals and 95 glaucoma patients were included in this study. Glaucoma was defined on the basis of both optic nerve damage and visual field defects. Scanning laser polarimetry, optic disc topography, automated perimetry and refractometry were performed in all subjects. The sensitivity and specificity of SLP were assessed applying a previously calculated cut-off to a previously described linear discriminant function (LDF). Results:,The sensitivity and specificity of SLP in the study population were 82% and 83%, respectively. Sensitivity and specificity were not affected by age, sex, race, average disc diameter or disc area. The sensitivity of SLP tended to be higher in myopes (93%) than in emmetropes (80%) and hyperopes (71%) (p = 0.08). Sensitivities were higher in individuals with cup areas > 0.96 mm2 (89%), rim areas , 1.36 mm2 (92%), and cup area/disc area ratios > 0.45 (89%) (p < 0.05). Stepwise logistic regression analysis indicated that the presence of a cup area > 0.96 mm2 and a rim area < 1.36 mm2 significantly increased the sensitivity of the LDF, whereas a cup area/disc area ratio , 0.45 significantly increased the specificity of the LDF. Conclusion:,The sensitivity and specificity of SLP may be influenced by refractive error and optic disc parameters that are affected by glaucomatous damage (cup area, rim area and cup area/disc area ratio). These parameters must be considered in studies evaluating the sensitivity and specificity of optic nerve/retinal nerve fibre layer imaging technologies. [source]

Comparability of three-dimensional optic disc imaging with different techniques

ACTA OPHTHALMOLOGICA, Issue 1 2000
A study with confocal scanning laser tomography, raster tomography
ABSTRACT. Purpose: We wanted to compare optic nerve head topography measurements and discrimination between normal and glaucomatous eyes with two entirely different three-dimensional optic disc imaging techniques, confocal scanning laser tomography (Heidelberg Retina Tomograph, Heidelberg Engineering) and raster tomography (Glaucoma-Scope, Ophthalmic Imaging Systems). Methods: Both eyes of 225 normal subjects and 229 eyes of 166 patients with glaucoma at different stages were imaged with the Heidelberg Retina Tomograph and the Glaucoma-Scope. Optics discs were analysed in 15° sectors around the circumference. Depth measurements were calibrated on objects with known dimensions. Results: We observed no significant differences in absolute measurements of maximum cup depth and cup area between the two instruments. We observed small differences in absolute measurements of disc anti rim area between the two instruments. Discrimination between normal and glaucomatous eyes was close to identical for the two instruments. Both instruments had the same ability to distinguish glaucomatous regional alterations of optic nerve head topography from normal disc configuration. Conclusion: Both instruments while using entirely different principles for three-dimensional optic disc imaging gave very similar results. This correspondence of results implies that the same optic disc parameters can be analysed, and the results interpreted similarly for both methods, and probably with other three-dimensional imaging instruments. It may also indicate that results of studies with one of the instruments have general validity. [source]

Optic nerve head parameters of an indigenous population living within Central Australia

CLINICAL & EXPERIMENTAL OPHTHALMOLOGY, Issue 9 2006
John A Landers MBBS MPH
Abstract Purpose:, Clinical examination of the optic disc is an essential element in the assessment of its health. Previous work has described normal optic disc appearance among different races. No such description of optic discs exists for indigenous Australians, who are at low risk of developing glaucoma. This study was designed to evaluate optic disc parameters of indigenous Australians. Methods: A sample of 208 indigenous Australians were recruited as they presented to remote clinics in Central Australia. Each subject underwent optic disc photography using a Topcon TRC-NW100 digital fundus camera. Optic discs were measured and analysed with Topcon ImageNet 2000 software. Results: Among other parameters, mean vertical disc diameter and disc area were 2.13 ± 0.21 mm (mean ± SD) and 3.13 ± 0.57 mm2, respectively, for right eyes and 2.14 ± 0.21 mm and 3.16 ± 0.58 mm2 for left eyes. When compared with published studies, these parameters were significantly larger than Caucasians, but similar to African individuals. Conclusion:, Our results suggest that indigenous Australians have optic discs that are larger than those of Caucasians, but similar to those of Africans who are considered to at a greater risk of glaucoma. Factors other than optic disc area are likely to underlie the higher prevalence of primary open angle glaucoma among African individuals. [source]