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Biomedical subjects

R Held

Publications and source records attributed to R Held.

At least 55 records · Page 3Linked to original sources
PubMed1983

The development of vergence does not account for the onset of stereopsis.

The onset of measurable stereopsis in human infants occurs at approximately 4 months of age, directly following a period of rapid oculomotor development. The experiment reported here was designed to investigate whether the onset of stereopsis is determined solely by the onset of accurate oculomotor coordination or whether neural development in the binocular visual system is necessary. These alternatives were examined by means of a testing procedure which ensured that stimuli were presented within 1.4 deg of the horopter. That these stimuli are insensitive to errors of vergence was verified by testing thirty infants aged 6 to 10 months who were known to have stereoacuity of at least 1 min of visual angle. All but one infant retained the ability to make stereo discriminations with simulated vergence errors of up to 30 prism diopters. Results obtained from a group of forty-four infants tested longitudinally between 0 and 6 months showed a mean age of onset of stereopsis of 4.1 months. Thus, ensuring that stimuli are presented near to the horopter does not significantly alter estimates of the age of onset of stereopsis. These results suggest that neural development which is critical for the ability to make stereo discrimination must occur during the first 3 months of life.

Child Development↗
PubMed1983

The development of binocular summation in human infants.

The difference in pupil diameter between monocular and binocular viewing conditions was used as a measure of binocular luminance summation in 97 infants aged 0 to 12 months. No significant difference in pupil diameter under monocular versus binocular viewing conditions was found until the end of the fourth month of life. The age of onset was positively correlated with the age of onset for stereopsis as assessed by preferential looking. By the end of the 6th month, the difference in pupil diameter under the two viewing conditions was adult-like in magnitude. The procedure provides an objective measure of binocular function that is not affected by fixation error. The data suggest that the visual pathways by which signals from the two eyes converge are not functional until the 4th month of life.

Adult↗
PubMed1982

Visual acuity of infants with ocular diseases.

We tested the visual acuities of 110 infants with ocular disorders by a preferential-looking technique that provides fast, accurate measurements for preverbal children. The results were used to confirm initial clinical evaluations and to prescribe and monitor treatment. The test was particularly helpful in assessing the effects of occlusion therapy. The child sat on a parent's lap 50 cm away from a black partition containing two circular screens. A grating was projected on one screen and a homogeneous field was projected on the other. A hidden observer watched the infant's eye and head movements to determine which screen was preferred.

Age Factors↗
PubMed1982

Color-contingent tilt aftereffect: spatial frequency specificity.

The stimulus specificities of the color-contingent tilt aftereffect resemble those involved in the McCollough aftereffect, with the major exception that the magnitude of the former increases monotonically with the spatial frequency of matched inducing and test gratings; this monotonic increase is not found for the achromatic tilt aftereffect. Like the McCollough aftereffect, the color-contingent tilt aftereffect is tuned to the spatial frequency of the inducing gratings and can be induced on both oblique and main axes of the retina.

Color Perception↗
PubMed1982

Stereoacuity development for crossed and uncrossed disparities in human infants.

The development of stereoacuity for crossed and uncrossed disparities was assessed by means of a preferential looking procedure in a cross-sectional sample of infants aged 2-12 months and by following a longitudinal sample over the first 8 months of life. Crossed stereoacuity was found to develop earlier but at approximately the same rate as uncrossed stereoacuity. These data are consistent with the hypothesis that there exist two binocular mechanisms, one subserving disparity detection and one for uncrossed disparity detection.

Adult↗
PubMed1982

The postnatal development of monocular optokinetic nystagmus in infants.

Monocular optokinetic nystagmus (OKN) was studied in 24 human infants aged 3-35 weeks using electro-oculography and moving vertical gratings. At a constant velocity of 25 deg/sec, infants display direction dependent slow phase asymmetries until approximately 5 months after birth. A comparison was made of the cumulative eye displacement during the slow phases of OKN for nasal and temporal movement.

Age Factors↗
PubMed1982

Binocular adaptation that cannot be measured monocularly.

The tilt aftereffect (TAE) is used to demonstrate the existence of a purely binocular process in human vision. A purely binocular process is a process that can be activated only by matched inputs to the two eyes. It is insensitive to monocular stimulation. The TAE can be produced by exposure to a bipartite field with the top tilted to the left of vertical, the bottom to the right. After such adaptation a pair of colinear lines appears bent in the opposite direction. A cyclopean random-dot stereogram can be used as an adapting stimulus. It produces a 2 degree TAE when a cyclopean test stimulus is used and a 1 degree TAE when a binocular but noncyclopean test stimulus is used. If the same noncyclopean pattern is viewed monocularly, no TAE is measurable. The TAE does not transfer from cyclopean adaptation to monocular testing. Apparently, cyclopean stimuli activate a 'purely binocular process' that cannot be activated by either eye alone.

Adaptation, Ocular↗
PubMed1981

Development of visual acuity in infants with congenital cataracts.

The visual acuity of 4 infants with congenital cataracts was measured serially during the first year of life by a preferential looking technique. Two infants with bilateral cataracts and no measurable acuity before surgery showed rapid development of acuity to normal levels for age after surgery and optical correction. In an infant with a unilateral cataract and an infant with a cataract and persistent hyperplastic primary vitreous marked differences in monocular acuities were found after surgery. Acuities became equal in the latter case after occlusion of the normal eye, while the other infant recovered acuity with 'bi-ocular' viewing. These acuity measurements demonstrate the sensitivity of the human visual system to binocular and monouclar visual form deprivation in the first year of life.

Cataract↗
PubMed1980

Stereoacuity of human infants.

Stereograms were presented in a two-choice preference procedure. The mean age at which stereopsis was first demonstrable was 16 weeks. By a mean age of 21 weeks, infants had achieved stereoacuity of 1 minute of arc or better. In comparison with the relatively slow development of visual acuity, the time course for the development of stereoacuity is extremely rapid.

Age Factors↗
PubMed1980

Quick assessment of preferential looking acuity in infants.

A simple and rapid method for assessing the visual acuity of infants can be a valuable tool for eye care specialists as well as for researchers in vision. We have developed a preferential looking (PL) procedure that uses simple equipment to obtain measures of PL acuity in a few minutes. Infants ranging in age from 2 weeks to 1 year can be tested. Sessions on infants without any visual problems are completed in less than 5 min. Computer simulations of the technique show that the fast procedure attains almost 80% accuracy in assessing infants' PL acuity thresholds. When PL acuity thresholds obtained by the 60-trial method of constant stimuli were compared to those obtained by the fast method on the same infants, they were identical on 70% of the sessions and only off by one-half octave in an additional 20% of the sessions. Interobserver reliability was also high. The ease and rapidity of the procedure make it appropriate for use in the clinic.

Age Factors↗
PubMed1980

Preferential looking acuity in infants from two to fifty-eight weeks of age.

The fast preferential looking procedure was used to obtain measures of acuity in a group of infants without visual problems whose ages spanned the 1st year of life. The results show an increase in acuity on horizontal and vertical square wave gratings from about 6/360 Snellen at 4 weeks of age to about 6/18 at 1 year. Acuity on obliquely oriented gratings (045) increases more slowly so that by 1 year of age it is only 6/36.

Age Factors↗
PubMed1980

The effectiveness of a retinoscope beam as an accommodative stimulus.

Two experiments with adult subjects and one with infant subjects showed that the beam of a retinoscope, when viewed monocularly in a dark surround, does not stimulate accommodation. In this situation, the eye assumes an intermediate focus that is correlated with the individual's intermediate dark focus or resting state of accommodation. These results provide further evidence that near retinoscopy is a useful method of refraction which controls accommodation by minimizing effective stimulation. The technique is particularly valuable for refracting infants or young children who would otherwise require cycloplegia, and it may be an effective clinical method for the correction of night myopia and related anomalies in adults.

Accommodation, Ocular↗
PubMed1979

Hans-Lukas Teuber.

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Bibliographies as Topic↗