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Biomedical subjects

G L Kandel

Publications and source records attributed to G L Kandel.

At least 19 recordsLinked to original sources
PubMed1991

Variable expression of albinism within a single kindred.

We studied the albinotic characteristics in 13 members of a white family (age range, 2 to 73 years), which were graded according to severity and were correlated with visual acuity. Clinical, electrophysiologic, and biochemical characteristics of this family do not fit any known category of human albinism. The degree of heterogeneity in expression of albinotic features was unexpected. The correlation between visual acuity and nystagmus was particularly strong. The brown-haired propositus had severe skin involvement, iris transillumination, fundus hypopigmentation, and foveal hypoplasia. He had no manifest nystagmus, however, and his visual acuity was nearly normal. These observations suggest that nystagmus imposes a visual deficit beyond that related to foveal hypoplasia alone.

Adolescent↗
PubMed1988

Meridional differences in the directional sensitivity of the human color mechanisms.

The directional sensitivity (DS) of the red (pi 5), green (pi 4), and blue (pi 1) color mechanisms was measured for both the horizontal and vertical pupil meridians, thus localizing the peak of each pi-mechanism DS function within the two-dimensional pupillary aperture. In the horizontal meridian, there were greater differences among observers in DS function peak locations than there were for any one observer. Along the vertical meridian, peak location differences within observers were similar to those found in the horizontal meridian, whereas among-observer differences were much smaller. Significant differences between horizontal and vertical DS function halfwidths were also found for at least one pi-mechanism of each observer. It is concluded that meridional variations exist in either the morphology or orientational distribution of foveal photoreceptors, and that more than one alignment mechanism is responsible for photoreceptor orientation in the human fovea.

Accommodation, Ocular↗
PubMed1985

A simple grating visual acuity test for impaired children.

Twenty-five developmentally delayed or neurologically impaired nonverbal children, aged 2 to 15 years, referred for visual acuity assessment, were beyond the age at which standard preferential-looking techniques are considered to be effective and none could be tested with Snellen letters, illiterate Es, or Allen pictures. Our method, in which the children learn to point to grating stimuli, enabled us to obtain monocular visual acuity estimates in 19 of the 25 patients. When indicated, patching therapy was begun and was monitored with this method. Similar testing of 31 unimpaired children showed good prediction of recognition visual acuities except in patients with visual acuities worse than 20/160. The grating method accurately identified or excluded amblyopia in 26 of 31 children (84%). We consider this a clinically useful test of visual acuity in nonverbal impaired children.

Adolescent↗
PubMed1984

Albinotic characteristics in congenital nystagmus.

We studied 26 white patients (19 males and seven females), ranging in age from 1 to 57 years, with congenital nystagmus for the characteristics of albinism. None of the patients was known to be an albino and none had readily apparent signs of albinism. The study also included 26 controls matched by age, sex, race, and complexion. Twelve of the 26 patients with congenital nystagmus had one or more of the following characteristics: detectable iris transillumination (six of 25 patients), choroidal depigmentation (four of 22 patients), and abnormal tanning history (eight of 26 patients). Iris transillumination and abnormal tanning were not found in any of the controls but two controls showed choroidal depigmentation and one showed blunting of the macular reflex (this was determined to be age-related). These differences were significant for iris transillumination (P = .01), blunting of the macular reflex (P = .01), and abnormal tanning (P = .002) but not significant for choroidal depigmentation (P = .38). Within the group of patients with congenital nystagmus, iris transillumination was significantly associated with blunting of the macular reflex (P = .03), choroidal depigmentation (P = .03), and abnormal tanning (P = .004) but not with eye color (P = .16) or visual acuity (P = .33). These findings suggested that many patients with apparently isolated congenital nystagmus may have subclinical albinism or a form of albinoidism.

Adolescent↗
PubMed1982

The Stiles--Crawford function of an albino observer.

Stiles--Crawford functions (SCF's) were measured for both eyes of an albino observer with a marked pendular nystagmus using an eye position monitoring system. Both eyes demonstrated directional sensitivity as revealed by their SCF's. The directional sensitivity of both eyes was less than that of either the foveal or parafoveal region of normal observers. In addition, there was a significant difference between the SCF's for the albino observer's two eyes. Our results suggest that the psychophysical SCF is predominantly the result of the orientational distribution of groups of receptors on the retina.

Adult↗
PubMed1980

Clomiphene treatment of the idiopathic hypofertile male: high-dose, alternate-day therapy.

Increasing reports suggest that clomiphene citrate (clomid) is useful in the treatment of idiopathic hypofertile males. Recent studies have advocated low-dose, cyclic therapy (25 mg daily for 25 days, 5 days' rest) and, although significant clinical responses have been reported, the hormone response has been erratic. This study of 53 patients, given high-dose, alternate-day therapy (100 mg three times/week), shows an over-all positive response rate of 66% and a pregnancy rate of 26%. Significant gonadotropin and testosterone surges were seen in the responders, but a selective lack of a follicle-stimulating hormone surge was noted in a small group of nonresponders. Clomiphene given in this dosage seems to be safe for periods of up to 15 months and appears to be a rational and useful agent for the treatment of this patient group.

Adrenal Cortex Hormones↗
PubMed1980

Are the dominant eyes of amblyopes normal?

The common assumption that the dominant eyes of unilateral amblyopes are normal eyes is shown to be unjustified. The dominant eyes of unilateral amblyopes are shown to have reduced sensitivity, reduced acuity, and a horizontal eccentricity of fixation when compared to eyes of persons with normal acuity and normal binocular fixation.

Amblyopia↗
PubMed1979

Laterality for stereognostic accuracy of children for words, shapes, and bigrams: a sex difference for bigrams.

Children identified nonsense shapes by touch better with their left hand and words better with their right hand. Bigrams were processed by boys as shapes and by girls as words, which suggests a sexual dimorphism of brain functioning for bigrams. A relative specialization of the hemisphere for stereognostic processing is also suggested, since the accuracy of identification by both hands was greater than chance for all three types of stimuli.

Adolescent↗
PubMed1977

Monocular fixation and acuity in amblyopic and normal eyes.

We studied the relation between eccentricity of monocular fixation and the minimum angle of resolution invisually normal subjects and in both the amblyopic and dominant eyes of amblyopes. For the amblyopic and visually normal eyes, this relation was linear; resolution was poorer at the eccentrically fixating locus than at the corresponding region of the normal eye. The dominant eyes of the strabismic amblyopes had a nasal component of eccentric fixation that was less than that of the companion amblyopic eyes, but greater than the that found in the visually normal eyes. In terms of the eccentricity of monocular fixation, the domonant eyes of strabismic amblyopes were different from the normal eyes.

Adult↗
PubMed1976

Experimentally induced variations in the dark adaptation functions of a severe strabismic amblyope.

Dark adaptation curves were determined for an amblyopic and a normal control subject following a variety of preadaptation conditions. Sizable between-eye differences were found in the dark adaptation functions of only the amblyope; the magnitude of such differences varied with this subject's distance from the light preadapting screen and with the effective size of his pupils during the light preadaptation period. Marked differences were also found between the dark adaptation functions of both eyes of the amblyopic subject and those of the normal subject. The preadaptation-dependent changes in the dark adaptation function of the amblyopic subject are hypothesized to result from anomalies of amblyopic eye light adaptation which are referable to disturbances of retinal receptor alignment.

Age Factors↗