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Biomedical subjects

R Held

Publications and source records attributed to R Held.

At least 37 records · Page 2Linked to original sources
PubMed1989

[Posterior uveitis caused by highly malignant B cell lymphoma].

A diagnostic vitrectomy was performed on three patients with posterior uveitis of unknown origin and whose vitrous body was markedly affected. In all cases, cells of high-grade B-cell lymphoma (earlier referred to as reticulum cell sarcoma) were identified by cytological analysis of the specimen. In addition to the ocular findings, one of the three patients showed clinical and radiological evidence of a tumorous mass in the area of the right thalamus at the time of diagnosis. This was interpreted as a cerebral manifestation of the lymphoma. Initially, the other two patients did not show any cerebral involvement. One of them, however, developed clinical symptoms 9 months after diagnosis, which were radiologically verified as tumor infiltration of the cerebellum and the diencephalon. Under radiation therapy, the ocular findings disappeared within a few weeks.

Adult↗
PubMed1987

Vernier acuity is less than grating acuity in 2- and 3-month-olds.

Vernier acuity and grating acuity were measured longitudinally starting at 1 or 2 months of age in 22 infants, using a two-alternative, forced-choice preferential looking technique. For vernier acuity, the motion-sound display was employed. For grating acuity, a preferential looking method was employed. Steps of the stimulus (vernier offset and spatial frequency of the grating) and procedures were basically identical between the two acuity tests. The range of stimuli was set so as to compare the two acuities at younger ages. Results show: vernier acuity is less than grating acuity at 11-12 weeks of age or younger, and the developmental rate of vernier acuity is greater than that of grating acuity in the first half-year of life. To interpret the data, it was speculated that: the mean sampling distance (center-to-center distance between receptive fields) may influence vernier acuity more than grating acuity, whereas the size of the receptive field may influence grating acuity more than vernier acuity: when the mean sampling distance is large relative to the size of the receptive field, vernier acuity may be less than grating acuity. Thus, the neonatal visual system, just as the visual system in the periphery and in strabismic amblyopia, may be characterized by spatial undersampling.

Age Factors↗
PubMed1987

Orthogonal astigmatic axes in Chinese and Caucasian infants.

Caucasian infants are known to have a high incidence of astigmatism. The axis of greatest power is usually in the orientation orthogonal to the most common type found in Caucasian adults, with-the-rule astigmatism. We now find that Chinese infants also have a high incidence of astigmatism relative to adults, but its orientation is orthogonal to that of Caucasian infants. The source of this racial difference is not clear. It is unlikely to be due to the most obvious difference, the structure of the eyelids.

Adolescent↗
PubMed1986

Pre-stereoptic binocular vision in infants.

In a preferential looking experiment, identical patterns (vertical stripes) were presented to both eyes on one of two screens while orthogonal patterns (vertical stripes in one eye and horizontal stripes in the other) were presented on the other screen. Most infants younger than 3.5 months of age originally showed a preference for the dichoptic (interocularly orthogonal) pattern. At an average age of 3.5 months, however, they showed a sudden shift of preference from this pattern to the interocularly identical pattern. The full shift from a preference for one stimulus to the other (both statistically significant) occurred within a few weeks in most cases. The onset age of the shift in preference agreed with the onset age of fusion-rivalry discrimination found in a previous study (Birch et al., 1985). The original preference for the bincularly orthogonal patterns may be interpreted as a preference for a grid (interocularly emergent intersections) over a grating, judging from results of two control experiments. These data suggest that the pre-stereoptic system non-selectively combines information from the two eyes without regard to edge orientation because it loses eye-of-origin information at a relatively early stage of binocular visual processing. Thus, the pre-stereoptic system does not have the capability of interocular suppression. The theoretical and clinical significance of the new findings are discussed along with a neuronal model of cortical development of ocular segregation and binocular pathways.

Adult↗
PubMed1985

Infant astigmatism and meridional amblyopia.

The orientation preferences of 70 infants aged 7 to 53 weeks with significant astigmatism [1.0 or more diopters (D)] were measured using a preferential looking procedure with paired gratings. The preference data show the consequences of the blurring effects of astigmatism when these are not compensatable by accommodation. Data from infant astigmats tested with optical correction look like those of nonastigmats. We have found no evidence for the development of meridional amblyopia during the first year of life.

Accommodation, Ocular↗
PubMed1985

Development of acuity and stereopsis in infants with esotropia.

Visual acuity and stereopsis of 19 esotropic infants and toddlers, 36 normal infants and 7 children with refractive anomalies were measured during the first three years of life using newly developed preferential looking procedures. Children with infantile esotropia corrected with prisms equal in size to the deviation show some degree of binocularity up to at least 21/2 years, as measured by a polaroid bar stereogram procedure with a 1800 seconds of arc disparity. A few children, who did not receive any therapeutic intervention, failed this test during the first and second year. However, all older subjects (over 6 years of age) with a history of infantile esotropia failed the test.

Adolescent↗
PubMed1985

Preferential-looking assessment of fusion and stereopsis in infants aged 1-6 months.

The ability of infants to discriminate zero-disparity stimuli from both reverse contrast (rivalrous) and disparate (stereoscopic) stimuli was investigated in a two-alternative, forced-choice, preferential-looking paradigm. Few infants under 4 months of age demonstrated discrimination for any stimulus pairing. Of the infants tested at 4 months of age, approximately 70% preferred zero-disparity stimuli to reverse contrast stimuli, and 82% preferred stereoscopic stimuli to zero-disparity stimuli. Nearly 100% of 5- and 6-month-old infants exhibited these preferences. These findings suggest that sensory fusion is not present at birth but develops rapidly over the first 6 months of life. The time course for the development of sensory fusion was similar to the time course for the development of stereopsis in nine infants tested longitudinally.

Adult↗
PubMed1985

The development of visual acuity in infant astigmats.

Acuity for vertical, horizontal, and oblique gratings was measured in 77 infant astigmats using a preferential looking procedure. Measurements were made with the refractive error uncorrected. Most of the infant astigmats were slightly to moderately hyperopic with respect to the test distance of 50 cm. Their acuity was not significantly different from that of a group of non-astigmatic infants. Average acuity for vertical and horizontal gratings increased from 6/200 at 1 month of age to 6/24 at 1 yr. Average acuity for oblique gratings increased more slowly, so that by 1 yr of age it was only 6/33. The only infants to show reductions in acuity were those with a strong myopic focus and one infant with a very strong hyperopic focus. When this infant was tested with optical correction, acuity improved to normal levels. This suggests that meridional amblyopia develops sometime after the first year of life or that it is confined to high spatial frequencies.

Astigmatism↗
PubMed1984

Anisotropic resolution in children's vision.

Grating acuity was measured for 4 orientations in 111 children aged 3-8 yr. Results showed that 73% of the children had better acuity for horizontal and vertical compared to oblique gratings, 14% showed no anisotropy, and 13% had better acuity for oblique gratings. The magnitude of the oblique effect was 0.2 octaves, similar to that found in both younger children and adults.

Astigmatism↗
PubMed1984

Development of vernier acuity in infants.

The development of vernier acuity in human infants aged 2-9 months was assessed by a preferential looking procedure using a vernier-motion display. The displacement of vernier offsets gives the impression of motion only when the vernier offsets are detected. Grating acuity of the same group of infants was also measured by a preferential looking procedure. Vernier acuity was found to be superior to grating acuity only after 3 months of age. This superiority of vernier acuity was compared with the superiority of stereoscopic acuity to grating acuity. The two classes of hyperacuity proved to be almost equivalent in terms of their developmental time-courses. A common physiological basis for the development of hyperacuities is suggested.

Child Development↗
PubMed1984

Astigmatism in children: changes in axis and amount from birth to six years.

Noncycloplegic refractions of 1,000 children aged 0-6 years revealed a high incidence of astigmatism, especially in the first 2 years of life. Before age 41/2 years, most of the astigmatism was against-the-rule and after that age most was with-the-rule. Of 19 children who did not show astigmatism in the first year, only one acquired it by 4 years. Of 29 children who had large amounts of astigmatism in the first year, all showed elimination or a large reduction in the amount of the cylindrical error by 4 years. These results are relevant to the etiology of astigmatism.

Age Factors↗
PubMed1983

Monocular visual form deprivation in human infants.

A preferential looking technique was used to measure visual acuity in human infants under one year of age who experienced monocular visual form deprivation. Of the 14 cases reviewed, 9 infants had monocular occlusion as therapy for esotropia; 3 infants had unilateral opacities of the ocular media; and 2 infants had unilateral eyelid closure from infection or burns. Despite differences in exact mode of deprivation, the effects on visual acuity were similar. There was a reduction in visual acuity in the deprived eye and a simultaneous increase in acuity of the non-deprived eye. These effects of monocular deprivation were not permanent. Recovery occurred with reverse deprivation or by simple cessation of the deprivation.

Cataract↗
PubMed1983

Binocular visual form deprivation in human infants.

Visual acuity was measured with a preferential looking technique in infants and toddlers with binocular form deprivation. Of the 10 children in the study, there were 5 with congenital cataracts and 5 with uncorrected high refractive errors. Infants with cataract surgery before 2 months of age showed normal early development of visual acuity. A 4 to 6 month delay before treatment resulted in reduced acuity but recovery subsequently occurred. Infants with high hyperopia or astigmatism showed no acuity deficits in the first year of life when tested with optical correction. One case of early meridional amblyopia was detected in the third year of life. The deficit was not permanent and, after a period of optical correction, there was recovery of visual acuity to normal levels.

Age Factors↗
PubMed1983

Visual acuity and its meridional variations in children aged 7-60 months.

A new operant procedure was used to assess grating acuity in children aged 7-60 months. The procedure was successful for 95% of the children sampled and had high test-retest reliability. Visual acuity for main axis (horizontal and vertical) gratings improved from 6/15 at 12 months to 6/6 at 60 months. For the 7-16 month age group, preferential-looking estimates of acuity agreed well with operant estimates. Acuity for oblique gratings was approximately 1/4 octave lower than main axis acuity throughout the age range. The results suggest that the human visual system continues to develop throughout the first 5 years of life.

Adult↗
PubMed1983

Shared characteristics of stereopsis and the purely binocular process.

Wolfe and Held (1981) Vision Res. 21, 1755-1759 demonstrated the existence in the human visual system of a purely binocular process. A purely binocular process is defined as a process that responds only to binocular stimulation and not to stimulation of either eye alone. In this paper, some of the characteristics of the purely binocular process are investigated. We find: (1) the process is less sensitive to high spatial frequencies than is the visual system as a whole. (2) It is insensitive to stimuli near the detection threshold for the visual system as a whole. (3) It makes a greater contribution to the appearance of vertically oriented stimuli than to the appearance of horizontally oriented stimuli. (4) The function of the purely binocular process can be disrupted by blurring the image in one eye (artificial anisometropia). Each of these properties of the purely binocular process is similar to the known characteristics of stereopsis. This suggests that the purely binocular process is a necessary stage in stereopsis.

Adaptation, Ocular↗
PubMed1983

Psychophysical assessment of visual acuity in infants with visual disorders.

The measurement of visual acuity is an essential part of the eye examination of adults, but is rarely attempted in infants being examined for presumed or known eye disease. We have used a preferential looking technique to test visual acuity of infants attending a hospital eye clinic. Serial measurements of acuity of infants attending a hospital eye clinic. Serial measurements of acuity in infants with certain eye diseases can provide examples of the effects of visual deprivation on the developing human visual system. Amongst 14 cases of monocular visual form deprivation in early life, there were 9 infants who had monocular occlusion as therapy for esotropia; 3 infants who had unilateral opacities of the ocular media; and 2 infants who had unilateral eyelid closure from infection or burns. Despite differences in exact mode of deprivation, the effects on visual acuity were similar. There was a reduction of visual acuity in the deprived eye and a simultaneous increase in acuity of the non-deprived eye. These effects of monocular deprivation were not permanent. Recovery occurred with reverse deprivation or by simple cessation of the deprivation. Of 10 children with binocular visual form deprivation, there were 5 who had bilateral congenital cataracts and 5 who had bilateral uncorrected high refractive errors. Infants with cataract surgery before 2 months of age showed normal early development of visual acuity. A 4-6 month delay before treatment resulted in reduced acuity, but recovery subsequently occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗