Contrast sensitivity testing.
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Glaucoma↗
Biomedical subjects
M Wolkstein
Publications and source records attributed to M Wolkstein.
Flicker threshold and pattern VEP latency in ocular hypertension and glaucoma.
Latency of the pattern visual-evoked potential (PVEP) was measured in 24 ocular hypertensive (OHT) patients, eight open-angle glaucoma (OAG) patients, and 37 control subjects. The PVEP stimulus was a 2.3 cycle/degree sinusoidal grating, counterphase-modulated at 1 Hz. Field size was 9 degrees and mean luminance 1.7 log ft-lamberts. For 22 of the 32 patients, a psycholphysical measure of dynamic contrast sensitivity at 8 Hz (DRC) was obtained with a 4 degrees diameter stimulus, by determining the mean value for the contrast sensitivities to a homogeneous flickering field and to a 1.2 cycle/degree counterphase-flickering grating. Patient DRC values were compared with previously published control data from 21 subjects. Mean PVEP latencies of both the OHT and the OAG patients were greater than normal (P less than 0.001), with the OAG value larger than the OHT value (P less than 0.001). Mean DRCs were lower than normal (P less than 0.002) for both patient groups, with the OAG value lower than the OHT value (P less than 0.025). DRC correlated with PVEP latency for these patients (r = -0.66, P less than 0.001).
Evoked Potentials, Visual↗
Contrast sensitivity in retinal disease.
Central vision in patients with retinal disorders has been studied with sinusoidal grating patterns. Impaired detection of fine high-contrast gratings has been observed in patients with retinitis pigmentosa and glaucoma despite 20/20 vision. Abnormal contrast sensitivity to coarse gratings occurred in patients with certain macular disorders and occasional glaucoma patients, some with near-normal Snellen acuity. Thus, contrast sensitivity measurements demonstrate central visual deficits not apparent with Snellen testing.
Glaucoma↗
Interocular comparison of contrast sensitivities in glaucoma patients and suspects.
Glaucoma affected the ability to detect low-contrast, flickering patterns ('DRC' measurement). DRC patterns were foveally viewed, of low spatial frequency, and flickering at 8 hertz. Interocular comparisons were performed in control subjects, in ocular hypertensives, and in glaucoma patients with asymmetric damage. Interocular differences in DRC tended to be of greater magnitude in the glaucoma patients than in the ocular hypertensive patients or control subjects. In the glaucoma patients DRC was consistently lower in the eye with the greater field defect than in the other (more normal) eye. In patients with optic disc asymmetry DRC was lower in the eye with the more abnormal disc. Treatment asymmetries did not appear to play a significant role in these relationships. When examined by interocular comparisons DRC showed no consistent relationship to Snellen visual acuity or to level of intraocular pressure at the time of DRC testing.
Form Perception↗
The ocular manifestations and functional effects of occupational argyrosis.
Thirty employees of an industrial plant involved in the manufacture of silver nitrate and silver oxide underwent ophthalmologic evaluation in an effort to evaluate the frequency and extent of ocular argyrosis. The most frequently noted ocular abnormality was pigmentation of the conjunctiva, present in 20 workers; corneal pigmentation occurred in 15 workers. A direct relationship existed between the levels of pigmentation and duration of employment. Ocular pigmentation was seen more frequently than cutaneous pigmentation. Ten workers noted decreased night vision, but electrophysiologic and psychophysiologic studies of seven of these ten workers demonstrated no functional deficits.
Adult↗
Abnormalities of central contrast sensitivity in glaucoma.
The detectability of foveally presented low-contrast flickering stimuli was determined for glaucoma patients, ocular hypertensives, and normal control subjects. Two types of stimuli, a homogeneous flickering field, and a counterphase flickering grating of low spatial frequency, were presented on a screen subtending 4 degrees of visual angle. The average of the contrast sensitivities to these two simuli (defined as the dynamic response coefficient) was consistently lower in glaucomatous than in normotensive eyes. The dynamic response coefficient was also below normal in half the ocular hypertensive eyes.
Adult↗
Visual association cortex and vision in man: pattern-evoked occipital potentials in a blind boy.
In a 6-year-old child who had been blind since the age of 2 years, occipital potentials of normal amplitude and waveform could be evoked not only by diffuse light flashes but also by alternating checkerboard ans sinusoidal grating patterns of low spatial frequency. Computerized tomography demonstrated destruction of the occipital lobes except of the primary visual projection area. Thus, in man, destruction of visual association cortices may result in loss of vision with partial preservation of pattern-evoked occipital potentials.
Blindness↗
[Clinical report of a conservative management in treating acute vitreous haemorrhage (author's transl)].
In the first hours after a vitreous haemorrhage dense enough to obscure the retina, the blood is usually confined to the posthyaloid space in an aqueous phase. Binocular occlusion and elevation provides sufficient immobilization of the eyes in 9 out of 10 patients for the blood cells to settle to the bottom of the space and make the retina available for examination and repair. Is this not done, blood will eventually enter the vitreous gel through holes that develop in the posterior hyaloid membrane. Blood in the gel does not settle and requires months to clear.
Acute Disease↗
Acute vitreous haemorrhage: a clinical report.
In the first hours after a vitreous haemorrhage dense enough to obscure the reina, the blood is usually confined to the posthyaloid space in an aqueous phase. Binocular occlusion and elevation provides sufficient immobilization of the eyes in nine out of 10 patients for the blood cells to settle to the bottom of the space and make the retina available for examination and repair. Blood enters the vitreous gel through holes that develop in the posterior hyaloid membrane. Blood in the gel does not settle and requires months to clear.
Bandages↗