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At least 541 records · Page 30Linked to original sources
PubMedDate not supplied

Ocular malingering and hysteria: diagnosis and management.

Confronted with a claim of poor vision in the absence of any apparent pathology, the ophthalmologist must consider the possibility that the patient is malingering or hysterical. The authors define four categories of such patients, and recommend diagnostic approaches for each. Specific diagnostic tests are described, as are methods of managing patients once the diagnosis of malingering or hysteria has been made.

Evoked Potentials↗
PubMedDate not supplied

Visual loss "at stool".

A 25-year-old white man presented with a history of loss of consciousness and visual loss associated with a Valsalva maneuver. Examination revealed a visual acuity of "no light perception" in his right eye with a flat visual evoked potential. The patient was subsequently found to have a giant aneurysm of the anterior communicating artery which was treated by direct clipping via a transfrontal craniotomy. The patient slowly recovered good visual function in his right eye.

Adult↗
PubMedDate not supplied

Video display units and visual function.

The widespread use of visual display units (VDU) in the workplace has engendered visual complaints and concern for workers' health and safety. The detectable levels of radiation emitted from VDUs have been well below safety levels and exposure to VDUs does not appear to cause any organic damage to the eye. However, visual disturbance and eye discomfort affects many workers using VDUs, and these symptoms may be alleviated by a number of measures, including proper diagnosis of pre-existing ocular problems, use of special eyeglasses, and correct arrangement of lighting and furniture in the work area.

Cataract↗
PubMed1989

Visual field defects for unidirectional and oscillatory motion in depth.

Visual fields for oscillatory motion in depth were recorded for 21 subjects. Near fields were different from far fields in 8 and similar in 11 subjects. Visual fields for unidirectional motion in depth were recorded for 16 subjects for near and far disparities. Some subjects had fields that differed for approaching versus receding motion in depth and/or for near versus far disparities. In particular, for near disparities, approaching versus receding motion gave fields that were different in 5 and similar 7 subjects; for far disparities, approaching versus receding motion gave fields that were different in 1 and similar in 10 subjects. For approaching motion in depth, near fields differed from far fields in 3 and were similar in 8 subjects; for receding motion in depth, near fields were different from far fields in 5 and similar in 8 subjects. Because sensitivity to monocular frontal plane motion showed no irregularities corresponding to the stereomotion field defects, we conclude that (1) stereomotion field defects were chiefly due to defective cortical processing of motion. We also conclude that (2) stereomotion field defects--at least for unidirectional motion--are caused by loss of sensitivity to unidirectional motion in depth rather than to abnormal interactions between mechanisms for approaching and receding motion, and (3) the finding of directional-specific stereomotion blindness is better explained by the two-population than by the one-population hypothesis of stereomotion blindness. We suggest that the substantial incidence of stereomotion field defects in normally-sighted subjects has implications for clinical studies and for visual assessment of pilots.

Adult↗
PubMed1989

Binocular beats: psychophysical studies of binocular interaction in normal and stereoblind humans.

We describe a psychophysical method for assessing binocular integration using dichoptically-presented uniform fields. By temporally modulating uniform field luminances at different frequencies between the eyes, a rhythmic beat is produced--a visual percept characterized by undulations in luminance at a frequency equal to the arithmetic difference between the two monocular stimulus frequencies. Using a signal detection paradigm, we studied the beat as a function of modulation depth in normal and binocularly deficient subjects. Normal subjects easily detected the beat, even at low modulation depths, while stereoblind subjects (with stereoacuity worse than 2000 sec arc) failed to detect beats at any modulation depth or with any combination of stimulus frequencies tested. The beat provides evidence for the confluence of monocular signals into binocular integrating mechanisms. Our results therefore suggest that the status of functioning binocular mechanisms is related to the detectability of the beat. This uniform-field stimulus does not require accurate accommodation, fixation, vergence or high spatial resolution, thus making this technique particularly attractive for the study of binocular interaction in developing infants and in binocularly deficient adults.

Adult↗