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Query: UMLS:C0038379 (strabismus)
 9,317 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The karyotype 46,XX/69,XXY was found in a 13-year-old mentally subnormal patient with club feet, strabismus, eunuchoid habitus, small penis, midscrotal urethrovaginal opening, small descended left testis, and small undescended right testis; no ovarian tissue could be found at laparotomy. Triploid:diploid cell ratios were 60:40 and 4:96 in skin fibroblasts and curculating lymphocytes, respectively. In the triploid line, two of the no. 13 chromosomes had unusually large satellites and one of the no. 22 chromosomes had a brightly fluorescent zone on its short arms. The patient's father was heterozygous for both these autosomal markers; the mother carried neither marker. This, together with the single Y, indicated that the extra haploid set was derived from the father. Of several possible mechanisms, we favor the suggestion that double fertilization occurred; one sperm nucleus immediately fused with the egg nucleus producing the diploid line; the second sperm nucleus was incorporated later into one of the two cells resulting from the first division of the zygote, producing the triploid line.
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PMID:A diploid-triploid human mosaic with cytogenetic evidence of double fertilization. 24 May 27

Stereopsis testing has received renewed interest because of its relationship to strabismus and amblyopia. This paper discusses clinical implications of stereo responses on traditional line stereograms and on newly developed random dot stereograms in normals, strabismics and amblyopes. Random dot stereograms are computer generated which when binocularly fused give rise to stereoscopic depth.
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PMID:Clinical stereopsis testing: contour and random dot stereograms. 36 8

Kittens appear visually immature at eye opening and studies were conducted to trace changes with maturity. Longitudinal determinations of optical quality indicate that optical factors may not limit visual performance in young kittens. Estimates of visual axis alignment in alert kittens at various ages show that functional visual divergence does not occur even when the pupillary axes are divergently misaligned. It is thus possible that fused binocular vision may occur in very young kittens, suggesting that procedures that disrupt binocularity may have effects at the cortical level. Single-unit analysis of striate cortex in kittens monocularly deprived for varying periods during the first three postnatal weeks confirms this possibility. Effects are also found for kittens reared with monocular defocus to simulate anisometropia. Binocular recovery from the effects of monocular deprivation is found to be quite limited in kittens given binocular exposure following unilateral lid-suture. The recovery that occurs requires active visual input rather than a cessation of imbalance in the two eyes. A long period of binocular exposure appears to be ineffective in restoring binocular connections in a cat reared with optically induced strabismus.
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PMID:Some neural and non-neural factors in visual development of the kitten. 74 13

Certain plastic prisms, when used with polarized tests (eg, stereopsis), can destroy the uniqueness of each eye's view. We investigated this effect by administering the Randot stereotest to 12 visually normal observers. The test was administered monocularly (simulating suppression), under habitual conditions, and through six representative prisms, both fused and monocularly. Whereas stereo thresholds with an anaglyphic random dot stereogram (TNO) were not significantly affected by the prism, fusing through some of the prisms resulted in significantly poorer stereo thresholds and a failure to detect random dot stereopsis (RDS) on the polarized stereotest. Furthermore, some subjects appreciated RDS viewing monocularly through each of the prisms. Thus, it is important to conduct polarized testing through prisms that are known not to interfere with polarization. This optical phenomenon is explained here.
J Pediatr Ophthalmol Strabismus
PMID:Erroneous findings in polarized testing caused by plastic prisms. 224 41

The eyes of adult barn owls (Tyto alba) are virtually fixed in the head in positions that are highly consistent from one individual to the next. However, early in development the eyes are exodeviated; the eyes achieve their adult positions during the owl's second month of life. Disruption of binocular vision in baby owls leads to permanent, highly abnormal eye positions and interocular alignment. Of three owls raised with both eyelids sutured closed, two developed exotropic strabismus and one developed esotropic strabismus. Two owls reared with monocular vision developed esotropic strabismus, whereas three owls reared with fused, but optically deviated binocular vision developed normal eye positions. Thus, the alignment of the eyes in adults results from an active process that depends on fused binocular vision during early life. Extracellular microelectrode recordings from the optic tecta of strabismic owls reveal that many units retain binocular inputs from corresponding points of the two eyes: the left-eye and right-eye receptive fields of individual units are misaligned by an amount predicted by the direction and magnitude of the strabismus. These results indicate that an innately determined pattern of connections in the brain anticipates the eye positions necessary to achieve binocular fusion. The hypothesis is put forth that the powerful activation of such binocular neurons by strong, synchronous inputs from the two eyes is the signal required by the optimotor system that proper eye alignment has been attained.
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PMID:Fused binocular vision is required for development of proper eye alignment in barn owls. 248 36

The clinical and anatomical features of a live-born diprosopic lamb are described. There are no complete anatomical analyses of two-faced lambs in the literature despite the frequency of conjoined twinning in sheep. The lamb had two heads fused in the occipital region. Each head had two eyes. The pinnae of the medial ears were fused. Caudal to the neck the lamb appeared grossly normal. The lamb was unable to raise its heads or stand. Both heads showed synchronous sucking motions and cranial reflexes were present. Nystagmus, strabismus, and limb incoordination were present. The respiratory and heart rates were elevated. There was a grade IV murmur over the left heart base and a palpable thrill on the left side. Each head possessed a normal nasopharynx, oropharynx, and tongue. There was a singular laryngopharnyx and esophagus although the hyoid apparatus was partially duplicated. The cranial and cervical musculature reflected the head duplications. The aortic trunk emerged from the right ventricle just to the right of the conus arteriosus. A ventricular septal defect, patent foramen ovale, and ductus arteriosus were present along with malformed atrioventricular valves. Brainstem fusion began at the cranial medulla oblongata between cranial nerves IX and XII. The cerebella were separate but small. The ventromedial structures from each medulla oblongata were compressed into an extraneous midline remnant of tissue which extended caudally to the level of T2. The clinical signs therefore reflected the anatomical anomalies. A possible etiology for this diprosopus might be the presence early in development of an excessively large block of chordamesoderm. This would allow for the formation of two head folds and hence two "heads."
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PMID:Clinical and anatomical observations of a two-headed lamb. 370 86

Stimuli on corresponding points of both retinae that cannot be fused may cause binocular rivalry: the stimuli suppress each other alternately. This effect was used to study the influence of image sharpness upon binocular inhibition. Blurring an image means decreasing its contrast and attenuating its high spatial frequencies. Both factors diminish the time that a stimulus is perceived during rivalry. This fact has implications both for normal vision--as objects off the horopter are normally blurred--and for disturbed vision when the image of one or both eyes is (locally) deteriorated. In both cases, the binocular field of view can be combined from the 'good' parts of both eyes. Hence, the field of view may consist, in a piece-meal fashion, of parts stemming from the right or the left eye exclusively and others where both images are superimposed. We present evidence for the hypothesis that there is a common neural mechanism causing both binocular rivalry and functional amblyopia in anisometropia and strabismus. Consequences of the results on rivalry suppression for the pathophysiology and therapy of strabismic amblyopia are discussed.
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PMID:Non-fusable stimuli and the role of binocular inhibition in normal and pathologic vision, especially strabismus. 664 79

In order to elucidate the type, size and depth of suppression scotomata in microstrabismus and small angle convergent strabismus, we performed binocular static perimetry in 14 subjects with strabismus and four normal observers. The strabismic cases had an objective angle of convergent squint between 1 and 8 deg, visual acuity between 0.1 and 1.25, and limited stereopsis. During testing the subjects fused pictures on two Friedmann visual field analyzers. Right and left eyes were studied separately under both monocular and binocular viewing conditions. In five strabismics a suppression scotoma was found in the squinting eye, with a diameter of 5-30 deg and a depth ranging from 4 to 14 dB. No suppression scotomata could be detected in the nine other subjects nor in the four normal observers. In conclusion, only 36% of subjects with strabismus were found to have a suppression scotoma. These scotomata were centered around the fixation point of the squinting eye, in some cases also encompassing the foveal area, and varying in depth and size.
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PMID:Quantitative perimetry under binocular viewing conditions in microstrabismus. 937 78

Vergence adaptation is an important element of comfortable binocular single vision and probably contributes to the high incidence of orthophoria or small angles of heterophoria in the normal population. Where binocular single vision has been absent for a period of time, restoration of good visual acuity appears to enable the vergence adaptation mechanism to become active again. A case is presented in which a moderate to large angle of deviation rapidly 'disappeared' once good visual acuity was restored and the disparate images could be fused. Known factors concerning vergence adaptation are discussed in relation to such clinical cases.
Strabismus 1999 Dec
PMID:The role of vergence adaptation in recovery of binocular single vision (BSV) following sensory strabismus. 1069 15

A model of the cross-link interactions between accommodation and convergence predicted that heterophoria can induce large accommodation errors (Schor, Ophthalmic Physiol. Opt. 1999;19:134-150). In 99 consecutive patients with intermittent tropia or decompensated phoria, we tested these interactions by comparing their accommodative responses to a 2.50-D target under binocular fused conditions (BFC) and monocular occluded conditions (MOC). The accommodative response in BFC frequently differed from that in MOC. The magnitude of the accommodative errors in BFC, ranging from an accommodative lag of 1.80 D (in an esophoric patient) to an accommodative lead of 1.56 D (in an exophoric patient), was correlated with distance heterophoria and uncorrected refractive errors. These results indicate that heterophoria affects the accuracy of accommodation to various degrees, as the model predicted, and that an accommodative error larger than the depth of focus of the eye occurs in exchange for binocular single vision in some heterophoric patients.
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PMID:Accuracy of accommodation in heterophoric patients: testing an interaction model in a large clinical sample. 1634 34


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