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At least 307 records · Page 17Linked to original sources
PubMedDate not supplied

[Ring-like figures in the fundus oculi detected by ophthalmoscopy in transformed light].

Examinations of the fundus oculi in red-free polarized light, carried out in 19 patients (12 with albinism and 7 with the albinotic type of the fundus oculi) have revealed for the first time a peculiar ring-like figure. Since there is no evidence that this figure is formed by retinal folds, the authors suppose that it may result from light wave interference. Light waves on the fundus oculi of albinos may be reflected not only by the internal border membrane, but by Bruch's membrane or sclera as well. These waves, overlapping each other, form a figure identical to Newton's interference rings. The presence of a ring-like figure in the centre of the fundus oculi may be regarded as an additional clinical sign of albinism of the fundus oculi. Together with other signs, this phenomenon may be used as a marker of albinism gene carriership.

Adolescent↗
PubMedDate not supplied

The effect of compression on clinical diagnosis of glaucoma based on non-analyzed confocal scanning laser ophthalmoscopy images.

BACKGROUND AND OBJECTIVE: To evaluate the effect of different image compression formats of non-analyzed Heidelberg Retina Tomography (HRT; Heidelberg Engineering, Heidelberg, Germany) images on the diagnosis of glaucoma by ophthalmologists. MATERIALS AND METHODS: Thirty-three topographic and reflectance images taken with the HRT representing different levels of disease were transformed using nine different compression formats. Three independent ophthalmologists, masked as to contour line and stereometric parameters, classified the original and compressed HRT images as normal, suspected glaucoma, or glaucoma, and Kappa agreement coefficients were calculated. RESULTS: The Tagged Image File Format had the largest file size and the Joint Photographic Experts Group (JPEG) 2000 format had the smallest size. The highest Kappa coefficient value was 1.00 for all ophthalmologists using the Tagged Image File Format. Kappa values for JPEG formats were all in the range of good to excellent agreement. Kappa values were lower for Portable Network Graphic and Graphics Interchange Format compression formats. CONCLUSION: Image compression with JPEG 2000 at a ratio of 20:1 provided sufficient quality for glaucoma analysis in conjunction with a relatively small image size format, and may prove to be attractive for HRT telemedicine applications. Further clinical studies validating the usefulness of interpreting non-analyzed HRT images are required.

Data Compression↗
PubMed1990

Measurement of eye rotations in three dimensions and the retinal stimulus projection using scanning laser ophthalmoscopy.

A transformation algorithm is introduced to specify eye rotations in three dimensions from two-dimensional translations of ocular fundus landmarks dynamically monitored by means of the novel Scanning Laser Ophthalmoscope (SLO). The rotation parameters are expressed as Y-X-Z Euler angles and in terms of the rotation axis and one rotation angle. Additionally, the angular distance of the retinal stimulus projection can be evaluated relative to the fovea. By simultaneously operating as eye movement measurement device, fundus camera, and visual target projector, the SLO opens a variety of new applications for the combined analysis of eye movements and the underlying 'retinal events' in vision and oculomotor research.

Algorithms↗
PubMed1989

Ocular torsion measured by TV- and scanning laser ophthalmoscopy during horizontal pursuit in humans and monkeys.

Ocular torsion during horizontal foveal pursuit and fixation was measured in five human subjects and two trained monkeys (Macaca fascicularis) by direct analysis of the ocular fundus rotation. In the monkeys the fundus images of either eye were generated with a TV-ophthalmoscope while the contralateral eye pursued an 8' visual target moving sinusoidally (0.3-0.9 Hz, +/- 5 degrees) in the horizontal plane. In the humans a scanning laser ophthalmoscope (SLO) generated the fundus image of the ipsilateral eye, which pursued the visual target (same parameters as in the monkeys) mixed electronically into the laser scan raster. The image sequences were stored on videotape and subjected to a frame-by-frame rotation analysis. In both the humans and the monkeys, torsion (fundus rotation about the visual axis) sinusoidally modulated (up to 8 degrees peak-to-peak) during foveal pursuit, approximately in phase with horizontal eye position. Intorsion (nasal movement of the upper eye pole) or extorsion was found during pursuit in the temporal or nasal direction. Torsion showed considerable intra-individual fluctuation and interindividual variability with regard to phase and modulation depth relative to the pursuit movements, and was interspersed with irregularly occurring rapid deflections. Torsion of the conjugate, nonpursing eye was similar to torsion of the pursuing eye. In contrast, torsion during fixation was only loosely correlated with horizontal eye position. Slow torsional drifts and large, rapid deflections (up to 6 degrees) occurred in either direction at a given fixation point in the horizontal plane. We conclude that ocular torsion during horizontal pursuit in primates is actively generated by a separate, neural oculomotor subsystem.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Carbon disulfide effects on the visual system. I. Visual thresholds and ophthalmoscopy.

The visual effects of carbon disulfide exposure were studied in macaque monkeys with measurements of visual thresholds, fluorescein angiography and fundus photography. Five monkeys were exposed by inhalation for 6 hr a day, 5 days a week to 256 ppm carbon disulfide (CS2). The motor dysfunction observed in these monkeys appeared to be entirely reversible. All five suffered severe reductions in visual acuity and contrast sensitivity although flicker resolution was not affected. Visual loss was found to be irreversible, with degeneration of substantial numbers of retinal ganglion cells (companion paper) in those monkeys permitted to survive after the termination of exposure. None of the monkeys developed retinal microaneurysms or hemorrhages, major accepted signs of visual toxicity in CS2 exposed humans; thus, permanent visual loss may result from carbon disulfide exposure even in the absence of retinal vascular effects.

Animals↗