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Results for “Contrast Sensitivity”

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PubMed1996

Contrast sensitivity with monofocal and bifocal intraocular lenses.

Bifocal intraocular lenses (BIOLs) reduce image contrast. We measured contrast sensitivity (CS) to evaluate the clinical significance of the loss in image contrast. Four groups were compared: 15 patients with a monofocal IOL, 13 with the True Vista BIOL, 13 with the AcuraSee BIOL, 11 with the diffractive BIOL. CS was measured using the Mentor B-VAT II-SG. Distance CS was slightly better in monofocal eyes than in all bifocal eyes, and distance CS was considerably better than near CS in eyes with the True Vista or the AcuraSee BIOL. With the diffractive BIOL, values were about the same at distance and near focus. Our results demonstrate that BIOLs reduce CS. thereby performing differently: both True Vista and AcuraSee favor distance vision, while the diffractive BIOL provides about the same contrast at distance and near focus.

Aged↗

PubMed1992

Color vision and contrast sensitivity tests in early diagnosis of primary open-angle glaucoma.

Color vision was examined by the Farnsworth 100 hue test in 48 eyes with ocular hypertension (OHT). Thirteen eyes had a general loss of color discrimination and 8 had a blue-yellow axis. Spatial contrast sensitivity was tested in 31 eyes with OHT by the Mentor B-VAT and was reduced in 8 of them. Temporal contrast sensitivity was explored in 40 eyes with OHT by the Flickersyst&m and showed abnormal responses in 11 eyes. According to the lack of specificity of the responses and the overlapping of the results of normal eyes and OHT eyes, those tests are not useful for classifying an individual patient. Such investigations however have the interest to show that macular mediated functions may be impaired early in glaucoma.

Adult↗

PubMed1999

Comparison of contrast sensitivity in different soft contact lenses and spectacles.

PURPOSE: To compare the visual performance of soft contact lenses and spectacles. METHODS: Twenty eyes of ten patients were examined. Each patient was fit with Acuvue, Cibasoft, and Biomedics contact lenses in random order. LogMar visual acuity and contrast sensitivity using the VectorVision CSV-1000 were measured. RESULTS: There was no significant difference in visual acuity between any contact lenses (P=.15). Contrast sensitivity at 12 cycles/degree was significantly lower for the Cibasoft lens compared to spectacles (P=.04). There was no significant difference between spectacles and contact lenses for remaining spatial frequencies (P=.07-.35). CONCLUSIONS: Visual acuity appears to be an insensitive method for evaluating soft contact lenses. The lathe-cut manufacturing process may be responsible for reduced visual function compared to cast-molded lenses. Further study in this area is needed.

Adult↗

PubMed1986

Effect of hemodialysis on contrast sensitivity in renal failure.

After a brief review of the ocular aspects of hemodialysis treatment for renal failure, we report on 10 patients who underwent this treatment. Contrast thresholds over a wide range of spatial frequencies and Snellen visual acuities were measured before and after treatment. Subtle changes in vision can be monitored by the contrast sensitivity function (CSF) technique. We conclude that there are measurable changes in contrast sensitivity after hemodialysis treatment for each of the 10 patients (20 eyes).

Adult↗

PubMed1989

Contrast sensitivity function and mobility in elderly patients with macular degeneration.

Eleven control subjects, 64-79 years of age, and 10 subjects with macular degeneration, 70-82 years of age, were included in this study. Each participant was tested for visual acuity, spatial and temporal contrast sensitivity, and mobility in an unfamiliar environment. The course was designed with a pair of steps, ramps, and a level pathway. The subjects were timed and videotaped. The number of errors was recorded. Visual acuity and contrast sensitivity were significantly different between groups. The time to complete the course was significantly different between groups; however, the difference did not remain significant after age-adjustment.

Aged↗

PubMed2006

Between- and within-individual effects of visual contrast sensitivity on perceptual matching, processing speed, and associative memory in older adults.

BACKGROUND: Although cross-sectional studies have demonstrated associations between visual contrast sensitivity and cognitive test performance, it remains unclear whether peripheral visual or perceptual factors explain the association. OBJECTIVE: We aimed at determining whether reducing static contrast of the study stimuli would simulate the performance deficits on measures of processing speed and associative memory that are associated with aging. METHODS: We investigated the mechanism by which vision and memory are associated in a sample of 91 volunteers aged 60-87 years. In tests of perceptual matching, digit-symbol matching, and associative memory, the level of static contrast of the stimuli was manipulated, with three contrast levels. The duration of stimuli presentation was also manipulated in the associative memory task in a full-factorial experimental design. Accuracy and response latencies (for correct trials) were measured. RESULTS: Experimental results showed that within subjects, lower contrast was associated with longer latencies, indicating an effect on information processing speed. Regression analyses replicated previous findings of a moderate to strong association between visual contrast sensitivity and cognitive performance in cross-sectional studies. CONCLUSION: These results provide support for a theory in which visual aging is associated with slower encoding of information as well as being involved at a more central level.

Age Factors↗

PubMed1981

Reading performance in low vision patients: relation to contrast and contrast sensitivity.

Closed circuit television (CCTV) systems have proven useful in professional and recreational rehabilitation of the partially sighted. However, the parameters for optimum performance on such systems have not been examined. This investigation shows that contrast is an important parameter in CCTV reading performance; for many patients, even slight contrast reductions significantly reduce reading performance. Distance acuity is not a good predictor of CCTV reading performance, nor is performance on conventional contrast sensitivity measures. However, a commercially available test for contrast sensitivity (the Arden plates) may be useful for predicting CCTV reading performance.

Aged↗

PubMed1980

Contrast sensitivity in retinal disease.

Central vision in patients with retinal disorders has been studied with sinusoidal grating patterns. Impaired detection of fine high-contrast gratings has been observed in patients with retinitis pigmentosa and glaucoma despite 20/20 vision. Abnormal contrast sensitivity to coarse gratings occurred in patients with certain macular disorders and occasional glaucoma patients, some with near-normal Snellen acuity. Thus, contrast sensitivity measurements demonstrate central visual deficits not apparent with Snellen testing.

Glaucoma↗

PubMed1991

Selective effects of low doses of apomorphine on spatiotemporal contrast sensitivity in healthy volunteers: a double-blind placebo-controlled study.

1. Apomorphine (1 and 5 micrograms kg-1) and placebo were given to nine normal volunteers, using a Latin-square design and double-blind procedures. The visual perception of static and moving patterns (static and motion contrast sensitivity) was evaluated before and 15 min after the dose administration. 2. Apomorphine (1 and 5 micrograms kg-1), as compared with placebo, led to a significant overall reduction of the visual perception of movement. This effect was dose-related, and apomorphine (5 micrograms kg-1) induced a more pronounced decrease in the visual perception of movement than apomorphine (1 microgram kg-1). With apomorphine (5 micrograms kg-1), the reduction was more pronounced for low spatial frequencies, and was linearly inversely correlated to the spatial frequency for a temporal frequency of 3 Hz. Finally, no significant effect of apomorphine was observed for sensitivity to static patterns. 3. Several non exclusive hypotheses may be suggested: The effects of apomorphine may result from stimulation of retinal D1- and/or D2-dopaminergic receptors. Apomorphine may increase the surround inhibition of ganglion cells' receptive-fields. This modification of the centre-surround balance may explain the decrease in contrast sensitivity for low spatial frequencies. The specific effects of apomorphine on the visual perception of movement support the hypothesis that apomorphine preferentially affects the magnocellular pathway which mediates sensitivity to moving patterns.

Adult↗

PubMed1987

Contrast sensitivity and pattern ERG in Waldenstrom's macroglobulinaemia.

Patients with Waldenstrom's macroglobulinaemia (WM) and age matched controls have been examined using tests of contrast sensitivity and pattern electroretinography. The patients with WM were in remission on maintenance treatment and had only moderately elevated plasma viscosity. They showed evidence of abnormal contrast sensitivity but there was no significant difference in amplitude of the pattern ERG between patients and controls.

Blood Viscosity↗

PubMed1985

The influence of nystagmoid oscillation on contrast sensitivity in normal observers.

Normal observers subjected to retinal image motion equivalent to that experienced by congenital nystagmats were found to display a contrast sensitivity function with characteristics similar to those shown by nystagmat observers. The amplitude, frequency and waveform (and hence foveation time) of nystagmic oscillation were varied, with alteration of the waveform producing the most significant effect on the contrast sensitivity function. The pseudocycloid waveform with the longest percentage foveation time per cycle was commensurate with the best visual resolution of medium-to-high spatial frequency targets. For all waveforms the length of the foveation period showed good correlation with visual resolution of the targets.

Adult↗

PubMed1985

Fechner's paradox in binocular contrast sensitivity.

It is generally accepted that binocular spatial contrast sensitivity in normal observers is higher than monocular sensitivity by some 42% across all spatial frequencies, an amount predictable on the basis of neural summation of the two monocular responses. Such summation predicts that a reduction of sensitivity in one eye would result in a fall in binocular sensitivity to a level approaching, but never lower than, that of the other eye. We present evidence that reduction in monocular sensitivity caused by reduced luminance can, in some subjects, lower binocular sensitivity to a level below that of the other eye, an analogue of Fechner's brightness paradox. In other subjects the expected summation occurs and binocular sensitivity always remains at or above the monocular level.

Form Perception↗

PubMed1983

Contrast sensitivity in albinotic patients.

Vertical and horizontal grating contrast sensitivity functions (CSF) were measured on eight albinotic patients. Several of these patients also had CSF measurements performed through their telescopic aids. For all the patients, the horizontal grating CSF was more sensitive than the vertical grafting CSF. Although there are many pathological problems that could result in this sensitivity difference (high astigmatism, neural modification, etc.), we propose that in this case, the nystagmoid eye movements are the main causative factor. Through the telescopic aid, the CSF resolution acuity and peak sensitivity increased. The increase in resolution was somewhat less than would be predicted based on magnification. The increase in sensitivity is believed to be the result of stimulation of more sensitive peripheral retina. This increase in sensitivity is an added benefit to these patients corrected with low vision aids.

Albinism↗

PubMed1981

Neural contrast sensitivity measurements with a laser interference system for clinical and screening application.

A He-Ne laser interference device for clinical measurements of the neural contrast sensitivity fraction (CSF) is described. The system uses planoparallel glass plates for the generation of sinusoidal gratings on the retina. Incoherent light from two light-emitting diodes is superimposed for reducing the contrast to a range from 2 X 10-3 to 0.5. The device is coupled with a microcomputer that calculates the contrast sensitivity (CS) and permits control of the system by a dialogue program. The mean CSF for normal observers (95 eyes) is presented, and the data are compared with overall CS values from other authors. Pathologic CSFs of three patients are shown as examples for the clinical application. For screening purposes the CS values for five spatial frequencies are compared with the normal CSF. And loss-of-contrast values are calculated.

Equipment Safety↗

PubMed1995

Effects of exposure to simulated altitudes on visual fields, contrast sensitivity, and dazzle recovery.

Previous studies have shown that visual performance may be impaired at altitudes above 12,000 ft when supplementary oxygen is not used. What is not known is whether there may be subtle changes in visual function at altitudes to which airline cabins are usually pressurized. In this study, we measured spatial and temporal contrast sensitivity, central visual field thresholds, and macular photostress recovery time in 12 male subjects at sea level and at simulated altitudes of 7000 ft and 12,000 ft. Our results showed insignificant changes in spatial and temporal contrast sensitivity, central visual field thresholds and dazzle recovery time with respect to simulated altitudes.

Adult↗

PubMed2002

Mental image generation and the contrast sensitivity function.

In one experiment, observers were instructed to generate small and large visual mental images in a light-adapted or a dark-adapted viewing condition, and to rate the vividness of each image. In light-adapted viewing, small images were generated faster than large images. However, the pattern of results was reversed in dark-adapted viewing. Furthermore, the dark-adapted images were more vivid than the light-adapted images. The results show that mental images can be mapped onto some regions of the contrast sensitivity function (CSF), so that the latency (and vividness) of a particular image can be predicted. Since the CSF reflects visual processes occurring mainly in V1, the results agree with functional magnetic resonance imaging data in indicating that early visual pathways participate in imagery. Nonetheless, imagery and perception may involve different processes hosted by the same neural structures as indicated by the direct relationship between image latency and contrast sensitivity.

Cognition↗

PubMed1989

High and low contrast acuity and clinical contrast sensitivity tested in a normal population.

Visual acuities obtained with a high contrast Bailey-Lovie chart (HCBL) and a low contrast Bailey-Lovie chart (LCBL) were compared with clinical contrast sensitivity function (CSF) measurements in a group of normal subjects with a wide range of refractive errors. We found high and significant correlations for the measurements obtained with the visual acuity tests, and between measurements obtained with the acuity tests and the CSF chart. These results indicate that the CSF test provides little additional information as a screening test in routine practice, and could probably be restricted in its use to patients in whom ocular disease is suspected.

Age Factors↗

PubMed2000

Retest variability of human infant contrast sensitivity: how many tests are sufficient?

Retest variability of a new infant contrast sensitivity (CS) card procedure was assessed by binocular measurement of a group of 20 6-month-olds twice within a 1-week period. Coefficient of reliability analyses showed that within-subject variability between tests was only slightly less than variation across subjects, which suggests that results from a single test are a poor predictor of an infant's "true" visual functioning. To determine how many tests are needed to estimate when infant CS stabilizes to within an acceptable (0.15 log unit) criterion, a second experiment was conducted in which a small group of subjects was tested repeatedly over a 2-week period. The results showed that averaging performance on 2 to 3 tests was required before an accurate estimate of the subject's performance could be obtained. Our results suggest that caution should be taken in the interpretation of a single measurement of infant visual functioning.

Contrast Sensitivity↗