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Results for “Contrast Sensitivity”

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PubMed1984

Spatial contrast sensitivity of the tree shrew.

Spatial contrast sensitivity functions (CSFs) were measured for 3 tree shrews. Our two-alternative forced-choice discrimination paradigm required the animals to discriminate a vertical sine-wave luminance grating from a homogeneous field of the same size (16 degrees) and mean luminance (35 cd/m2). Spatial frequencies tested ranged from 0.1 to 2.0 c/deg and grating contrast was varied trial-by-trial using a modified staircase technique. Small between-subject variations in the shape of the CSFs appeared to be correlated with our estimates of refractive error for each animal. In general, the CSFs were of the typical band-pass type with peak sensitivity occurring at approximately 0.7 c/deg. Estimates of grating acuity derived from the CSFs ranged from 1.2 to 2.4 c/deg and are within the limitations set by the eye size and retinal anatomy of the tree shrew.

Animals↗

PubMed1988

Age-related changes in contrast sensitivity in central and peripheral retina.

Eight young (average age 20.4 years) and eight elderly (average age 64.4 years) observers took part in three experiments designed to study age-related changes in peripheral retinal function. A further eight young (average age 22.3 years) and eight elderly (average age 63.8 years) observers took part in a replication of experiment 3. All observers had normal or better-than-normal visual acuity and no evidence of ocular pathology. All testing was monocular and the eye with better visual acuity was used. In the first experiment contrast sensitivity was measured in central retina and 10 deg temporally, at spatial frequencies of 0.2, 0.8, 2.0, and 5.0 cycles deg-1. Young observers had better contrast sensitivities than older observers, but only at higher spatial frequencies (2.0 and 5.0 cycles deg-1). For both groups, contrast sensitivity was poorer with peripheral presentation of stimuli than with central presentation, but not for the lowest spatial frequency used (0.2 cycle deg-1). In the second experiment observers had to detect the presence of a sharp edge (square-wave luminance profile), while in the third and fourth experiments the target was a "fuzzy' edge (sine-wave profile). Edges were again presented centrally or 10 deg temporally. As expected from the data of experiment 1, young observers were better able to detect the sharp edge than were the older observers in both central and peripheral viewing conditions. For both age groups, edge detection was better during central viewing than during peripheral viewing. However, contrary to expectations based on the results of experiment 1, detection of the fuzzy edge was better for central than for peripheral viewing for both age groups in experiments 3 and 4. The apparent (and expected) equality of performance found in experiment 3 for young and elderly observers in detecting the fuzzy edge was shown to be due to the range of contrast values used. When appropriate contrast values were used in experiment 4, young observers detected fuzzy edges presented in central retina better than did elderly observers. The results of experiment 1 show sparing of the ability to process low spatial frequencies across (i) age and (ii) retinal location, and are discussed in terms of the notion of (i) models of age-related loss of visual function and (ii) cortical magnification. The results of experiments 2, 3, and 4 provide some support for the proposition that the contrast sensitivity of observers may be used to predict their performance on other visual tasks.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗

PubMed1995

Comparison of temporal and spatiotemporal contrast-sensitivity tests in normal subjects and glaucoma patients.

Contrast sensitivity (CS) is reduced in glaucoma diseases. This study compares the value of different CS measurements in glaucoma diagnosis. The study population consisted of age-matched groups of 31 normal subjects (age, 36-59 years; median, 47 years; mean +/- SD, 47.4 +/- 7 years) and 59 glaucoma patients with optic disk damage and visual field defects (age, 36-63 years; median, 53 years; mean +/- SD, 52.3 +/- 7 years). Three types of CS determination were carried out in all subjects: (1) temporal CS of a sinusoidally flickering light (37 Hz) in a ganzfeld bowl, (2) spatiotemporal CS (alternating pattern: 2.5 Hz, 1 cycle/degree; screen size, 5.3 degrees x 4.3 degrees) in a temporal upper retinal area (13.8 degrees horizontal, 4.2 degrees vertical), and (3) spatial CS of a static pattern (three spatial frequencies: 0.6, 3.0, and 12 cycles/degree; screen size, 5.3 degrees x 4.3 degrees) with central fixation. In glaucoma patients the results of CS tests with flickering stimuli were highly significantly correlated with the perimetric mean sensitivity (MS; Octopus G1 program: temporal CS, r = 0.67, P < 0.001; spatiotemporal CS, r = 0.8, P < 0.001). For spatial CS the frequency of 3.0 cycles/degree showed the strongest correlation with MS (r = 0.64, P < 0.001). Only the peripherally localized, spatiotemporal CS showed a strong correlation with optic disk damage (r = 0.59, P < 0.001). On the other hand, the full-field flicker test achieved the best separation between normal subjects and glaucoma patients (specificity, 90%; sensitivity, 71%). These results indicate that tests for temporal resolution are more sensitive to glaucoma defects than are tests for spatial resolution.

Adult↗

PubMed2002

Contrast sensitivity of patients with severe motor and intellectual disabilities and cerebral visual impairment.

We attempt to evaluate the residual visual capacities of nine patients (seven males and two females; age range 4 to 35 years, mean 13.8 +/- 9.98) with cerebral visual impairment coupled with severe motor and intellectual disabilities by their contrast sensitivities to sine-wave gratings. Two methods were used for detecting the occurrence of ocular responses to stimuli: (1) detection of optokinetic nystagmus to drifting sinusoidal gratings by naked-eye observation and electronystagmography and (2) detection of ocular pursuit for a drifting Gabor patch by naked-eye observation. We succeeded in measuring the sensitivities of eight cases. For the remaining one case, only the Gabor method could be applied. Most cases showed low contrast sensitivity in both higher (2 and 4 cycles/degree) and lower (0.125 and 0.25 cycles/degree) spatial frequencies and relatively high contrast sensitivity in the middle (0.5 and 1 cycle/degree) range of spatial frequencies. We conclude that the residual visual capacities of patients with severe motor and intellectual disabilities and cerebral visual impairment can be measured fairly accurately by these behavioral methods.

Adolescent↗

PubMed1992

[Multifocal and monofocal implant. Comparative functional results (contrast sensitivity and dynamic visual acuity)].

The functional results (contrast sensitivity and dynamic visual acuity) of 19 multifocal (3 M design) and 14 monofocal intraocular (IOL) were compared. Best corrected visual acuity was > or = 8/10 P 2. Major differences of functional performance in favour of monofocal IOL's were found under standard conditions of vision (low contrast and illumination levels). Dynamic visual acuity allowed accurate evaluation of the difference of performance between these two models of implant. The indications for multifocal IOLs were reconsidered in the light of these results.

Aged↗

PubMed1981

Contrast sensitivity and central vision in reattached macula.

Macular functions were studied in patients recovering after surgery for retinal detachment involving the macula. Central vision was assessed by visual acuity, grating acuity, metamorphopsia, and contrast sensitivity tests for 5 months up to 3 years post-operatively. Impairment of contrast sensitivity was generally observed at high and intermediate spatial frequencies as compared to age-matched controls. In 2 cases, both with low visual acuity, an attenuation was also found at low spatial frequencies. Reductions of visual and grating acuity were closely related indicating that the test target for acuity determination is of minor importance in evaluating recovery in retinal detachments. The majority of the patients studied had different degrees of metamorphopsia. The reduction of the contrast sensitivity at intermediate spatial frequencies corresponded to the reduction in acuity. Our study thus presents no evidence for a selective vulnerability of specific contrast channels unrelated to acuity loss.

Adult↗

PubMed1995

Survey of colour contrast sensitivity in non-ophthalmic users of blue-green wavelength argon lasers.

BACKGROUND: Previous studies have shown that ophthalmologists using blue-green argon laser may suffer subtle defects in their colour vision. A reduction in colour contrast sensitivity in the tritan colour confusion axis, an early manifestation of blue cone photoreceptor injury by the high energy photons of the laser, has been demonstrated and has prompted a reappraisal of laser safety in ophthalmology. Argon laser is also frequently used in scientific research, often at higher power output and for longer periods than is used in clinical practice. The scientists operating these lasers are at risk of developing similar phototoxic retinal injury. METHODS: The colour contrast sensitivity of 18 scientists who regularly use short wavelength argon laser was investigated. RESULTS: Eye protection was infrequently used and individuals had been subjected to between 580 and 7200 hours of cumulative laser exposure during the course of their research. CONCLUSION: The use of blue-green argon laser by the scientists investigated was not associated with a significant reduction in colour contrast sensitivity.

Adult↗

PubMed1992

Contrast sensitivity and glare in cataract using the Pelli-Robson chart.

There is a need for a convenient, clinically applicable test of glare disability which can be used in the preoperative evaluation of patients with cataract. In this study, contrast sensitivity (using the Pelli-Robson letter chart), near vision, and visual acuity were compared, with and without the introduction of a glare source in 70 patients with cataract, 15 with intraocular lenses, and 19 controls. A disposable pen torch was shone at the pupillary margin to induce glare. Contrast sensitivity demonstrated the most marked reduction during glare testing. Cortical cataracts were most affected followed by posterior subcapsular opacities. The glare disability was significantly less in pseudophakic patients and was absent from patients with non-cataractous phakic eyes. Glare testing with a disposable pen torch and a Pelli-Robson contrast sensitivity letter chart provides a rapid test of glare disability which can be easily incorporated into the clinical appraisal of patients with cataract.

Aged↗

PubMed1993

Comparison of acuity, contrast sensitivity, and disability glare before and after cataract surgery.

We assessed vision before and after uncomplicated extracapsular cataract extraction and intraocular lens implantation in 72 symptomatic patients with acuity equal to or better than 20/80 and no other ocular abnormality. Contrast sensitivity was measured with the Pelli-Robson Letter Chart (Metropia Ltd, Cambridge, England) and disability glare was measured under daytime conditions with the Brightness Acuity Tester (Mentor O&O Inc, Norwell, Mass) and under nighttime conditions with a computer-controlled video display. Prior to surgery there was significant disability glare that was not correlated with acuity. There was also a loss in contrast sensitivity that was moderately correlated with acuity (r = -.43; P < .001). Following surgery, most patients' scores returned to normal on all tests. Improvement in disability glare and contrast sensitivity was independent of improvement in acuity. Furthermore, patients with the poorest preoperative vision were as likely to regain normal function after surgery as those with the best preoperative vision.

Adult↗

PubMed1982

Contrast sensitivity functions and specific reading disability.

Contrast sensitivity functions for normal and specifically disabled readers were measured in two experiments. Each study showed that specifically disabled readers and controls differ in the pattern of relative sensitivity across spatial frequencies. Both studies provide evidence of differences between normal and disabled readers on measures of visual mechanisms fundamental to the reading process.

Child↗

PubMed1988

Spatial contrast sensitivity in benign intracranial hypertension.

Spatial Contrast Sensitivity (CS) was studied in 20 patients with benign intracranial hypertension (BIH). At presentation CS loss was found in 43% of the eyes, and impairment of visual acuity attributed to BIH in only 16%. Nine patients had blurred vision or visual obscurations, all of whom had abnormal CS. The clinical application of CS measurement in BIH for monitoring the progression or regression of the disease is illustrated by serial measurements in 11 patients. Progressive visual loss in longstanding papilloedema and improvement of visual function in subsiding papilloedema can occur without any change in Snellen acuity or visual field charting.

Adolescent↗

PubMed1982

Temporal contrast sensitivity in central serous choroidopathy.

Temporal contrast sensitivity (TCS), a function of foveal sensitivity to sinusoidally modulated stimuli, was measured in 35 patients with central serous choroidopathy. Attenuation of the sensitivity at high temporal frequency was observed even when visual acuity was not impaired. In patients whose visual acuity was impaired, attenuation of the sensitivity of middle and/or low frequency as well as at high frequency was observed. In many cases TCS recovered to various degrees as the condition improved, even when little recovery of visual acuity was observed.

Adult↗

PubMed1991

Visual contrast sensitivity of U.S. Navy jet pilots.

Good visual contrast sensitivity (CS) is often described as a visual capability important for success as a military aviator and so has been suggested as a physical standard for personnel selection and retention. To evaluate this idea, we measured the CS of 135 U.S. Navy fighter pilots ranging in age from 24 to 44 years (mean = 30.20, S.D. = 4.06) and compared these to the CS of non-aviators. We obtained the non-aviator data from published studies of other investigators who used similar procedures with the same widely used, commercially available apparatus (Nicolet CST 2000). In addition to this comparison, we correlated the pilots' CS with their air-to-air target detection distances measured during air combat maneuver training and to their night carrier landing performance scores. The major findings were: 1) The mean CS of the aviators and the non-aviators were within +/- 1.0 S.D. of each other in most instances, and those few instances where a greater difference was found were parsimoniously explained by methodological and procedural factors; 2) sensitivities to different spatial frequencies were highly correlated among themselves, indicating much redundancy among the measurements; 3) there was no evidence of a relationship between CS and air-to-air target detection distances or night carrier landing performance.

Adult↗

PubMed1996

Color and luminance vision in human amblyopia: shifts in isoluminance, contrast sensitivity losses, and positional deficits.

The deficits for contrast detection and positional accuracy were compared for chromatic and luminance mechanisms within a group of strabismic and anisometropic amblyopes. We found that the isoluminant point was shifted towards red in the amblyopic compared to the fellow normal eye. This was not accounted for by eccentric fixation by the amblyopic eye. Contrast sensitivity deficits were similar for luminance and color stimuli in normal and amblyopic visual systems. In the majority of our amblyopic subjects, however, the deficits in positional acuity were greater for the chromatic than the luminance stimuli.

Adolescent↗

PubMed2003

Effect of photorefractive keratectomy and laser in situ keratomileusis in high myopia on logMAR visual acuity and contrast sensitivity.

PURPOSE: To compare effect of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) on contrast sensitivity (CS) and best corrected visual acuity (BCVA) in high myopia. METHODS: 38 myopes (PRK) and 31 patients (LASIK) were examined before and 1, 3, 6, and 12 months postoperatively. Mean preoperative spherical equivalent was -8.0 +/- 1.7D (PRK) and -9.2 +/- 2.1D (LASIK). CS was tested on a computerized system of the Contrast Sensitivity 8010 Type at 6 spatial frequencies (0.74 and 29.55 c/deg), BCVA was measured on logMAR charts. RESULTS: At 12 months postoperatively, mean spherical equivalent was -0.6 +/- 1.0D (PRK) and -1.0 +/- 0.8D (LASIK). Postoperative values of CS were significantly higher in the PRK group, except for spatial frequencies of 3.69 and 7.39 c/deg up to 3 months postoperatively. The initial significant decrease of BCVA lasted up to 6 months after PRK. In the LASIK group BCVA was not significantly different from its preoperative level at the 3-months follow-up. CONCLUSIONS: The significant improvement of CS after PRK suggest that PRK can improve quality of vision in eyes with high myopia. Although recovery of BCVA after LASIK was faster than after PRK, there may be a persistent decrease in CS.

Contrast Sensitivity↗

PubMed1980

Contrast sensitivity measures and accuracy of image stabilization systems.

Recently, it has been argued that the precision of image stabilization is reflected in the magnitude of the differences in contrast sensitivity measures obtained with and without image stabilization. Here we present two sets of data, one showing large and the other small differences in contrast sensitivity to sinusoidal gratings viewed under stabilized and unstabilized, normal conditions. Both sets of data were obtained by the use of the same apparatus optimized for image stabilization. Large differences occur between unstabilized and stabilized measures of sensitivity only when the observer is allowed to scan the unstabilized test grating, or to prolong inspection of the stabilized target thus allowing for disappearance of the stabilized image. On the other hand, when the target is presented for a few seconds and the observer fixates on it, normal image motion, which results from eye movements of fixation, is found to enhance contrast sensitivity by only a small amount. It would appear, therefore, that the extent of reduction of sensitivity for a stabilized grating cannot be used as an index of the precision of image stabilization.

Adult↗

PubMed1988

Contrast sensitivity in rats with increased or decreased numbers of retinal ganglion cells.

Contrast thresholds were measured electrophysiologically on striate cortex in normal rats and in rats in which either the superior colliculi were removed bilaterally or unilaterally at 5 days of age, or one eye was removed on the day of birth. Despite the fact that the collicular ablation leads to the degeneration of more than half the retinal ganglion cells, contrast sensitivity was normal in this group, with the possible exception of sensitivity at very low spatial frequencies below 0.1 c/deg. The result is strong evidence that retinal ganglion cells which project to thalamus as well as to mid-brain escape the degenerative effects of neonatal mid-brain lesions. The contrast sensitivity of neonatally operated one-eyed rats was significantly and substantially better than that of normal rats tested monocularly. The increased sensitivity was greatest in the cortex ipsilateral to the remaining eye. This supernormal sensitivity is presumably related to the increase in the number of ganglion cells in the remaining eye, especially those projecting ipsilaterally from the temporal retina and which show a five-fold expansion of their terminal zone in the thalamus.

Animals↗

PubMed2006

Using contrast sensitivity to estimate the cost-effectiveness of verteporfin in patients with predominantly classic age-related macular degeneration.

AIMS: To re-evaluate the cost-effectiveness of photodynamic therapy with verteporfin (Visudyne, Novartis AG, Switzerland) in patients with predominantly classic and classic choroidal neovascularization (CNV) owing to age-related macular degeneration (AMD), using new evidence on the impact of contrast sensitivity on health status. METHOD: A health economic model is used to synthesise the evidence on contrast sensitivity and treatment rates from the TAP Investigation with health state utilities and costs. Impairment of visual function is estimated using a Markov model to predict transitions between states of contrast sensitivity. Each state is associated with costs and a health state utility. Total expected costs and benefits for a cohort of patients over a defined number of cycles are calculated. The expected health state utility for each disease state was estimated using results from a study of 209 patients with AMD in Sheffield. The model includes the costs associated with treatment and monitoring in the verteporfin treatment arm and costs offset by delaying the deterioration of visual function. RESULTS: Beyond 3 years, the annual costs of the verteporfin arm are estimated to be less than the annual costs of the control arm, owing to the cost associated with higher blindness prevalence in the control arm. Over time, the results show that both the incremental utility and cost decreases. By 10 years, the estimated incremental cost-effectiveness is approximately pound20 996 per Quality-Adjusted Life Years. CONCLUSION: The results of this study suggest that the verteporfin therapy in the treatment for patients with predominantly classic and classic CNV owing to AMD is encouraging.

Aged↗