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At least 451 records · Page 25Linked to original sources
PubMed1986

Causes of visual impairment in children.

The populations formed by the pupils of the eleven Dutch institutions for visually handicapped children on the first of January 1980 were investigated, repeating the investigation of the International Association for Prevention of Blindness in 1970. The total number of pupils was nearly the same in both instances (1300 in 1970 and 1334 in 1980). No significant differences were found in the distribution of diagnoses and etiologies between the two groups. The congenital cataracts, the tapeto-retinal dystrophies and the optic nerve affections are still the three diagnostic groups with the highest prevalence (together 48.6%). To gain more reliable insight into morbidity patterns one needs longitudinal investigations with central registration of patient data, especially in studying the influence of pre- and perinatal problems.

Blindness↗
PubMed1986

Importance of pathological intraocular light scatter for visual disability.

For healthy eyes intraocular light scatter was investigated several decades ago. For pathological eyes, however, little is known. As clinical test several techniques have been proposed but none has gained general acceptance. A disadvantage of these tests was that quantities were estimated that related only indirectly to the amount of light scatter. We propose a method that gives a direct estimate of the light scatter. We studied patients with cataract, corneal dystrophy, iris and fundus hypopigmentation, etc. A remarkable finding was that visual acuity correlates rather weakly with the amount of scatter. Since, however, the amount of scatter causes a considerable loss of visual function, the results show that for these patients the visual acuity test gives a rather limited impression of their visual handicap. More attention to the problems associated with intraocular light scatter is needed.

Adolescent↗
PubMed1981

Clinical use of visual acuity measured with pupil responses.

The response of the pupil was measured to a foveally fixated small field in which a checkerboard was alternated with a blank field of equal luminance. Visual acuity was assessed with pupil responses in 70 subjects who visited our clinic. A high correlation was found between the visual acuity as measured with pupil responses and the subjective acuity, using the same checkerboard stimuli. We also compared the visual acuity as measure with with pupil responses with the Snellen acuity. The method of obtaining pupil visual acuity seems to compare favourable with other objective methods of measuring visual acuity.

Adolescent↗
PubMed1992

Does work with visual display units impair visual activities after work?

It is well established that visual display unit (VDU) operators complain of visual fatigue and visual stress during after-work hours. The present study was divided into two parts. In the first part, standard eye examinations were performed on a group of VDU workers (n = 32) and a control group (n = 15); those subjects who were found to have correct vision (n = 16 and 13, respectively) participated in the second part. The eye examinations revealed that on the average, the VDU workers suffered more than twice as many visual impairments as the controls. In those with correct vision, the near point of accommodation was measured at the beginning of the workday at the start of the week, and at the end of the workday, four days later. In the VDU group, the decrease in accommodation was uniformally distributed between zero and 1.0 diopter, whereas among the non-VDU workers, 77% of the decrease was between zero and 0.25 diopter. The dynamic range of accommodation in the VDU workers on the second examination was smaller than on the first. We conclude that some of the visual stress and visual fatigue that developed at work hindered visual activities after work.

Accommodation, Ocular↗
PubMed1991

On the relation between glare and straylight.

An overview is given of the basic phenomena that may lead to glare complaints in patients. Prominent among them is increased intraocular straylight; this can be measured. Other causes may include: increased sensitivity to normal straylight, the length of (increased) light and dark adaptation times, (small angle) neuronal lateral interaction. Distinction must be made between disability glare and discomfort glare. Tests have been proposed to determine glare-induced loss of various visual functions. Often the test results are thought to be directly related to straylight but this may be untrue.

Contrast Sensitivity↗
PubMed1991

Illumination research as part of a visual assessment of visually impaired individuals.

In this paper we describe a method for the preliminary assessment of the illumination needs of partially sighted individuals. The method is based on determining the smallest readable lettersize under different levels of illumination. Half of the partially sighted in our population had a performance that was dependent upon the level of illumination. At the same time, most of those for whom no improvement in performance was found, did express a preference for a certain level of illumination. Therefore, there remain discrepancies between the objectively determined optimal level and the preference for a certain level. We conclude that the current method is a useful but insufficient method of determining the illumination needs of partially sighted individuals.

Adolescent↗
PubMed1992

Whiplash and its effect on the visual system.

Whiplash or indirect injuries to the neck as a consequence of motor vehicle collisions are a common occurrence in which the frequency of ocular complications is largely unknown. Ophthalmic and oculomotor function was investigated in a longitudinal study of 39 cases who had their initial ophthalmological assessment within one week of the whiplash injury. Ten of 39 cases had ocular symptoms and signs which developed shortly after the accident. The principal abnormality in 6 of these was decreased convergence and accommodation, superior oblique muscle paresis in 2, decreased stereoacuity in 1 and bilateral vitreous detachments in 1 patient. All but 2 had complete resolution of their symptoms within 9 months. Four other patients were asymptomatic but had ophthalmic signs which resolved within 3 months. Oculomotor abnormalities following whiplash injuries are generally mild, have a good prognosis, and would appear from this study to be commoner than hitherto expected.

Accidents, Traffic↗
PubMed1994

Binocular interactions and steady-state VEPs. A study in normal and defective binocular vision (Part II).

BACKGROUND: Recent evidence indicates that an index of binocular activity may be found in some properties of steady-state visual evoked potentials (VEPs), such as amplitude facilitation and phase shortening. We evaluated binocular interactions with steady-state VEPs in normal subjects as well as in patients with concomitant strabismus and defective binocular vision. METHODS: Steady-state (8-Hz) VEPs to counterphased sinusoidal gratings (1.2 c/deg spatial frequency) of low contrast (3.2%) were recorded in 19 esotropic patients and in 18 age-matched controls. Patients had either anomalous retinal correspondence (ARC, n = 10) or suppression (n = 9) in casual seeing conditions (striated glasses). In all subjects, both binocular and monocular VEPs displayed a major component at twice the stimulation frequency (second harmonic), whose amplitude and phase were measured. A binocular interaction index was obtained by comparing binocular VEPs (BVEPs) with the sum (vectorial) of the two monocular VEPs (SMVEPs). RESULTS: In normal subjects, BVEPs were larger in amplitude than SMVEPs (facilitation), and shortened in latency (phase). On average, both ARC and suppression patients displayed loss in amplitude facilitation and absence of phase shortening. However, 50% of ARC patients showed clear VEP facilitation. In both ARC and suppression patients, the amplitude ratio BVEP/SMVEP was negatively correlated with the amount of the angle of deviation. CONCLUSION: These results suggest that losses in amplitude facilitation and phase shortening of binocular steady-state VEPs reflect abnormal binocular interactions associated with different forms of sensorial adaptation in concomitant strabismus.

Adolescent↗
PubMed1986

Static vergence and accommodation: population norms and orthoptics effects.

The steady-state characteristics of the accommodation and vergence systems can be described by a model with six major oculomotor parameters. These include the system biases (tonic vergence and accommodation) and forward-loop gains (vergence and accommodative gains), as well as the interactive system gains (AC/A and CA/C ratios). We investigated these parameters in two populations: (1) 22 visually-normal asymptomatic individuals, and (2) 21 visually-abnormal symptomatic individuals before and after conventional orthoptic therapy. Two parameters related to system gain differentiated between the symptomatic and asymptomatic individuals: the slope of the fixation disparity curve with accommodation open-looped and the slope of the accommodative response/stimulus curve. Following orthoptic therapy, 4 static model parameters and 1 dynamic clinical parameter showed changes toward the normal mean; this included tonic accommodation, slope of the fixation disparity curve with accommodation closed-loop (2.5D), slope of the accommodative response/stimulus curve, the CA/C ratio, and the +/- 2D monocular accommodative flipper rate.

Accommodation, Ocular↗
PubMed1975

Interocular transfer of the motion after-effect in normal and stereoblind observers.

The extent of interocular transfer of the motion after-effect was measured in 4 stereoblind subjects and in 19 subjects having varying degrees of stereopsis. Stereoblind individuals failed completely to show any interocular transfer of this after-effect, while subjects with good stereopsis exhibited between 55 and 82 percent transfer (mean 73 percent). Furthermore, normal subjects who manifested a clear eye dominance tended to show greater transfer from the dominant to the nondominant eye than vice versa. Individuals who either had a history of a strabismus or possessed some other early impediment to clear binocular vision tended to show less transfer. Overall there was a significant positive correlation of 0.75 between the extent of interocular transfer and the subject's stereoacuity. It is argued that the extent of interocular transfer of this after-effect provides a measure of the proportion of the total number of visual cortical neurons that are binocular. Thus stereoblind humans, who show no transfer whatsoever may, like cats and monkeys deprived of concordant binocular visual input early in life, suffer from a lack of binocular neurons.

Depth Perception↗
PubMed1978

[Focal migraine attacks without headaches (author's transl)].

The migraine without headaches is a special form of focal migraine, a migraine accompagnée without headaches. The diagnostic classification of the transient focal disturbances is made possible by careful analysis of the attacks. This type of attack starts in a localized manner (primarily in the ophthalmic area), develops corresponding to the cortical representation, and is not always restricted to one vascular area. Typical is the slow spread of symptoms over a period of ten minutes, on the average. This allows a differentiation from transient ischemic attacks or focal epilepsy. The diagnosis is supported by hereditary factors, early onset of manifestation and change of the side of focal symptoms (in 11 of 16 patients). Of 409 migraine patients, 16 were such cases, corresponding to an occurrence of 4%. There were no signs of symptomatic etiology for these transient focal disturbances.

Adult↗