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At least 217 records · Page 12Linked to original sources
PubMed1979

Oculogravic illusion in response to straight-ahead acceleration of CF-104 aircraft.

Experimental subjects wore goggles that restricted monocular vision to a luminous line fixed relative to the head, and they were exposed on one occasion to a straight-ahead acceleration of an aircraft and on another occasion to a tilting chair. The magnitude of change of direction of the resultant accleration was the same on both occasions, but the perceived movement of the luminous line from the two stimuli was very different. In response to the aircraft stimulus, the oculogravic illusion was experienced and the luminous line was perceived as tilting relative to the subject, in response to the tilting chair stimulus, the line was perceived as remaining fixed relative to the subject. It was concluded that the oculogravic illusion, as experienced in the aircraft (and previously in centrifuges), is a true illusion and not merely a fact of physics.

Acceleration↗
PubMed1984

Increase of GABA receptor binding activity after short lasting monocular deprivation in kittens.

GABA receptor activity, as measured by [3H]muscimol binding, was investigated in visual and auditory cortex of 5 weeks old kittens with different visual experience. Binocular deprivation since birth did not affect the GABA receptor binding activity. Three days of monocular vision resulted in an increase of [3H]muscimol binding in the visual cortex of both normally reared (144 percent) and binocularly deprived kittens (149 percent). Neither 3 days of normal binocular vision in deprived animals nor 3 days of binocular deprivation in normally reared ones produced significant changes in GABA receptor binding activity. In all experimental conditions [3H]muscimol binding in auditory cortex was similar. We suggest that activation of the GABA-ergic system is due to asymmetric visual input, possibly connected with mechanisms of ocular dominance shift.

Animals↗
PubMed1982

The precision of gaze. A review.

This paper reviews advances in our knowledge about the stability of the human being's line of sight while fixating objects stationary with respect to himself. Recent technological developments made it possible to measure gaze with a high degree of accuracy when the head was free of artificial support. Measurements made with the head free while the subject sat, as still as possible, show that gaze is half as stable as when the head is held rigidly. Precision deteriorates by an additional factor of five when the head is moved actively or passively within a range of natural physiological frequencies and amplitudes. Fixation errors and retinal image motions associated with such imprecision of gaze under natural conditions would not be expected to degrade monocular vision in light of current psychophysical evidence. Binocular fixation errors and differences in retinal image motions in each of the eyes, associated with imprecision of vergence under natural conditions, cannot, however, be reconciled with current psychophysical knowledge of binocular vision attained thus far only under artificial conditions.

Biophysical Phenomena↗
PubMedDate not supplied

[A neuronal network model, discerning faint image contours in the presence of primary receptor parameter scatter].

The neuron network model reproducing a number of phenomena concerned with peculiarities of monocular vision of moving and stationary relative to the retina objects was investigated. An analysis has shown that fulfillment of additional requirement of remaining model efficiency under condition of primary receptors parameters scatter may be realised in aforesaid model by insignificant modification of network structure.

Models, Theoretical↗
PubMed1994

Presbyopic drivers' vision through a convex rear view mirror.

BACKGROUND: Monovision is a commonly used modality for the presbyope who wants to wear contact lenses. If the add for near vision is in the left eye, driving an automobile creates a circumstance whereby the lens wearer cannot obtain a clear image in that eye of distant objects seen in the driver's side outside rear view mirror. METHODS: We have discovered that a stick-on convex mirror eliminates this problem by neutralizing either some or all of the power of the add. RESULTS: The driver wearing an add in the left eye can then obtain a clear image in that eye of objects behind and to the side of the automobile.

Automobile Driving↗
PubMed1998

[Oculocerebral syndrome: an infrequent pathological manifestation of carotid occlusion].

INTRODUCTION: The simultaneous occurrence of impaired visual and ipsilateral hemisphere symptoms is uncommon. It is associated with carotid pathology. CLINICAL CASES: We present three cases under the name of oculocerebral syndrome, in which there were symptoms of monocular ischemia and ipsilateral cerebral ischemia. In two of these cases the monocular vision loss was transient, and in the third case it was permanent due to occlusion of the central retinal artery. In all three cases there was evidence of obstruction of the internal carotid artery. CONCLUSION: The pathological process involved may be mixed, embolic-hemodynamic.

Aged↗
PubMed2001

Initial recovery of vision after early monocular deprivation in kittens is faster when both eyes are open.

A comparison was made of the speed of visual recovery in the deprived eye of kittens after a 6-day period of monocular deprivation imposed at 5-9 weeks of age in two postdeprivation conditions. In one condition, binocular recovery (BR), both eyes were open, whereas in the other condition, reverse lid-suture (RLS), the formerly nondeprived eye was closed to force the animal to use the originally deprived eye. In littermate pairs, BR kittens began to recover form vision 12 to 30 h before those subjected to RLS. The vision of the deprived eye of the BR animals remained superior to that of their RLS littermates for 4-8 days. Although this finding is difficult to reconcile with competitive mechanisms of synaptic plasticity, it supports a prediction of an alternative model of synaptic plasticity [Bienenstock, E. L., Cooper, L. N. & Munro, P. W. (1982) J. Neurosci. 2, 32-48] for slower initial recovery with RLS because of the time required to reset the modification threshold.

Aging↗
PubMed1999

How do general practitioners diagnose and manage patients with transient monocular loss of vision of sudden onset?

Symptoms of transient loss of vision in one eye differ widely. They may have different causes and therefore carry a different prognosis. We studied the influence of differences between characteristics of transient monocular blindness on the diagnosis and management by general practitioners (GPs). A postal questionnaire, was sent to 1600 GPs in The Netherlands along with four case vignettes describing a case history of a 56-year-old man with transient monocular disturbances of vision of sudden onset. We introduced random permutations in the following four elements of the history: partial or complete visual field involved, blurring or blacking out of vision, attacks lasting minutes or hours, and patients having covered either eye during the attack or not. Respondents were asked about the probable diagnosis and the preferred management. For each of the 16 permutations about 50 responses were obtained (overall response rate 54%). Ischemic transient monocular blindness (ITMB) was chosen as the most likely diagnosis in 49%. In 12% primary ocular disease was suspected. Involvement of the complete visual field, blacking out of vision, and short attacks were identified as independent predictors of a diagnosis of ITMB. A diagnosis of ITMB would have resulted in referral to a specialist in 72% of patients. Antithrombotic treatment would have been initiated in only 36% of ITMB patients. GPs consider brief attacks with complete blacking out of vision most typical for retinal ischemia. They refer only three-quarters of patients with probable ITMB to a specialist and start antithrombotic medication in only one-third of these patients. Therefore further education with regard to transient monocular blindness is needed.

Amaurosis Fugax↗
PubMed1983

Use of various measures of visual acuity and contrast sensitivity in the evaluation of monocular occlusion and active vision training of three adult amblyopes.

Three adult amblyopic patients who underwent vision training involving monocular occlusion of the nonamblyopic eye and stimulation of the amblyopic eye using simple fixation exercises and a spinning grating procedure were evaluated using five different types of acuity testing and two methods of contrast sensitivity. It was found that contrast sensitivity and isolated Landolt C acuity improved sooner and to a greater extent than the more complex visual acuity tasks. One patient who improved only on the simpler tasks complained that the enhanced contrast due to training made vision in that eye less acceptable because it was more confusing. The results show that multiple measures of visual acuity and contrast sensitivity are necessary to adequately monitor the effects of occlusion therapy.

Adult↗
PubMed1991

Binocular visual impairment in glaucoma.

Monocular and binocular vision was assessed in patients with glaucoma (n = 21), in patients with ocular hypertension (n = 20), and in age-matched visual control subjects (n = 20) using three tests: color vision with the Lanthony Desaturated D-15 test, low spatial frequency contrast sensitivity with the Pelli-Robson chart, and stereoacuity with the RANDOT test. No significant differences were found among the groups in the severity or type of color vision loss. Monocular contrast sensitivity testing showed considerable overlap among groups but a significant loss of contrast sensitivity in the glaucoma patients relative to ocular hypertensives and control subjects. Binocular testing also showed a significant loss of contrast sensitivity in the glaucoma patients compared with both the ocular hypertensives and the control subjects. Stereoacuity also was significantly impaired in the glaucoma patients. These results indicate that two tests of binocular function, stereoacuity and binocular contrast sensitivity testing, may have utility in identifying early glaucomatous damage.

Aged↗
PubMed1998

Threshold perimetry of each eye with both eyes open in patients with monocular functional (nonorganic) and organic vision loss.

PURPOSE: To report a novel binocular perimetry test to identify monocular functional vision loss. METHODS: In a prospective study, 10 patients with monocular functional vision loss, 10 patients with monocular organic vision loss, and 10 normal subjects were tested using a Humphrey automated perimeter attachment that performs central threshold perimetry of both eyes in a single test. First, patients were tested after being told their "good" (unaffected) eye was being tested; this was followed by a second identical test said to be on the "bad" (affected) eye. Two measurements were calculated for each subject: the functional component (deltaF), defined as the difference (in dB) between the mean threshold of the first and second tests, and the organic component (deltaO), the difference (in dB) between the mean threshold of the unaffected and affected eyes. RESULTS: Patients with monocular functional vision loss produced lower thresholds when they thought their affected eye alone was being tested but little intereye difference (mean deltaF +/- SD = 17.35 +/- 7.50 dB; mean deltaO = 0.01 +/- 1.40 dB). Patients with monocular organic vision loss had little difference between tests and lower thresholds in their affected eye (mean deltaF = 0.84 +/- 1.15 dB; mean deltaO = 9.01 +/- 4.71 dB). Normal subjects demonstrated little intertest or intereye differences (mean deltaF = -0.15 +/- 0.78 dB; mean deltaO = -0.05 +/- 0.51 dB). CONCLUSION: This perimetry method effectively distinguished between normal subjects, patients with monocular functional vision loss, and patients with monocular organic vision loss.

Adolescent↗
PubMed2001

Binocular summation for grating detection and resolution in foveal and peripheral vision.

Peripheral monocular grating resolution has been shown to be limited by the sampling density of the underlying retinal ganglion cells. We wanted to determine if peripheral resolution is also sampling limited binocularly; and, if so, how great is any improvement in either detection or resolution when viewing binocularly? We measured detection and resolution acuity for sinusoidal gratings in foveal and peripheral vision both monocularly and binocularly. Detection and resolution acuity were very similar in foveal vision and displayed a binocular improvement of 5% over best monocular acuity. However, in peripheral vision, while detection acuity improved by 6% binocularly, resolution acuity improved by 16%, with a subsequently smaller aliasing zone. This improvement was greater than predicted by probability summation and implies that the two monocular ganglion cell sampling arrays combine at a higher level resulting in a higher binocular sampling density.

Female↗
PubMedDate not supplied

Binocular vision regained after monocular traumatic aphakia by wearing contact lenses.

In this study 35 patients with monocular traumatic aphakia were enrolled to document the degree of binocular vision gained by optical correction with contact lenses. The most important factors in achieving binocular vision were the interval between formation of the traumatic cataract and surgery and between the operation and starting wearing contact lenses. There was a statistically significant correlation between these two intervals and the achievement of near stereopsis and normal visual acuity.

Adolescent↗
PubMed1993

Experimental myopia in a diurnal mammal (Sciurus carolinensis) with no accommodative ability.

1. We examined the functional morphology of the intra-ocular muscles of the grey squirrel using pharmacological and histological methods. Using sympathomimetic (phenylephrine) and parasympathomimetic (carbachol) agents, administered by transcorneal iontophoresis, the response of the iris sphincter and dilator muscles and the ciliary muscle were recorded. Measurement techniques included both streak retinoscopy and coincidence optometry for measurement of ocular refraction and high resolution ultrasonography to monitor changes in the intra-ocular component dimensions. 2. The grey squirrel was found not to possess a functional accommodative system. No change in ocular refraction or intra-ocular dimensions could be induced with 40% carbachol. Marked changes in pupil diameter occurred with topical application of both phenylephrine (dilation) and carbachol (constriction). Histological findings were in agreement with pharmacological findings in showing well developed iris sphincter and dilator muscles but only a poorly developed ciliary muscle. 3. Calculation of the depth of focus of the grey squirrel eye reveals that this could be sufficient to account for the behavioural observations of near viewing habits. 4. We then determined whether we could induce axial elongation of the vitreous chamber and a consequent myopia by monocular deprivation (MD) of pattern vision. 5. Monocular deprivation of pattern vision produced a significant experimental myopia due to axial elongation of the vitreous chamber in the deprived eye. 6. The results demonstrate that a functional accommodative system is not necessary to induce experimental myopia in the grey squirrel eye.

Accommodation, Ocular↗
PubMed1986

Sudden loss of vision in a monocular patient, caused by visual cortex infarction.

Infarction of the occipital cortex usually causes loss of the contralateral half of the visual field in both eyes. Although cases with complete transient loss of vision have been described, this is due to involvement of the second half of the cortex in the pathologic process. We report a case of a one-eyed patient with almost complete loss of vision in her only eye because of an infarction of the ipsilateral occipital cortex. During the patient's hospitalization, the temporal half of the visual field recovered. The case is of interest because of the difficulties in diagnosing cortical blindness in a one-eyed patient.

Aged↗
PubMed1978

Monocular versus binocular contrast thresholds for movement and pattern.

The superiority of binocular vision over monocular vision has been compared for the detection of stationary sinusoidal grating patterns, and for the detection of the apparent movement induced by rapidly phase-reversing such gratings. The thresholds for binocular and monocular pattern perception were in the ratio 1:2 1/2, as found by previous workers. For apparent movement, however, binocular thresholds were lower than monocular thresholds by a factor of 1.9; for every subject tested (n = 20) the ratio for movement detection was larger than the ratio for pattern detection. The effects of combining inputs from the two eyes cannot be explained solely by linear summation models, but may in some circumstances depend on the nonlinearities of certain types of nerve cell.

Form Perception↗