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At least 19 recordsLinked to original sources
PubMed1991

Assessment of potential contrast sensitivity. Part I: Preoperative prediction of contrast sensitivity following intraocular lens implantation.

Preoperative contrast sensitivity functions (CSFs) were determined for 15 cataract patients using laser-generated patterns that effectively bypassed the optical components of the eye. These functions were compared with postoperative CSFs determined using traditional methods by transmission through the optics of the eye. Accurate prediction of postoperative contrast sensitivity occurred in 91% of the cases (ten of 11) for patients with preoperative visual acuity of 20/200 or better and in 67% of all the cases (ten of 15). Prediction failures occurred when the laser interferometer was not able to penetrate the cataract or when postoperative complications occurred. These results suggest that preoperative measurement of laser interferometric CSF is a useful predictor of postoperative CSF for patients with mild to moderate cataracts that can be bypassed by the laser and with better than 20/200 preoperative visual acuity. The problem of assessment when lens opacity is advanced is addressed in Part II.

Aged↗
PubMed1992

The common cold, pattern sensitivity and contrast sensitivity.

Results from two studies involving challenge with respiratory syncytial viruses showed that volunteers who developed colds were more sensitive to a visually distracting pattern presented prior to virus challenge than were volunteers who did not get a cold. Volunteers with sub-clinical infections reported more illusions after virus challenge than they had done before, whereas uninfected volunteers and those with colds tended to report fewer illusions on the second test. These effects did not occur when volunteers were challenged with either a coronavirus or rhinovirus. Overall, the results confirm that behavioural measures may be related to susceptibility to subsequent illness, and that viral infections may influence visual perception. They also show that the effects vary according to the nature of the infecting agent, which agrees with results from studies looking at other aspects of behaviour.

Adolescent↗
PubMed1991

Assessment of contrast sensitivity. Part II: The relationship between objective lens opacity and laser interferometric contrast sensitivity in the cataract patient.

The laser interferometer can effectively bypass the optics of the eye and measure retinal function in patients with immature cataracts. However, it is not known how much laser interferometric measurements are impaired by cataract density. In this study we compared objective lens opacity using the IntraOptics opacity lensmeter with contrast sensitivity (CS) measured by a Randwal He-Ne laser interferometer. Comparison of lens opacity with CS in the cataract population revealed an inverse linear relationship between objective lens opacity and retinal contrast sensitivity. Separation by cataract type showed correlation coefficients as high as -0.91 for nuclear sclerotic predominant cataracts and as low as no significant correlation for posterior subcapsular predominant cataracts. Comparisons of before and after implantation surgery contrast sensitivities (as measured by the laser interferometer) with preoperative lens opacities (as measured by the IntraOptics opacity lensmeter) quantified the extent to which laser interferometric measurements underestimated potential retinal function. We found that for all cataracts, other than posterior subcapsular predominant cataracts, potential contrast sensitivity (in decibels) was underestimated by about 0.2 to 0.3 times the opacity measured by this technique.

Adult↗
PubMed1979

Age variations in normal human contrast sensitivity.

The visual contrast sensitivity (the reciprocal of contrast threshold) was studied as a function of age. Psychophysical measurements of binocular and monocular contrast thresholds were made for 33 normal observers at spatial frequencies within the range 0.5 to 40 cycles/degree. The observers were divided into three different age groups: young, middle-aged, and old subjects with the age ranges 6--10 years, 20--40 years, and 60--70 years, respectively. All observers had healthy eyes, normal vision, and Snellen visual acuity of 1.0 or better in both eyes. In all groups, contrast sensitivity for binocular and monocular viewing peaked at a spatial frequency around 3--5 cycles/degree and showed the typical attenuation at low and high spatial frequencies. The binocular contrast sensitivity was higher than the monocular. There was no significant difference between young and middle-aged subjects with regard to contrast sensitivity. Subjects aged 60 years or more showed significantly lower contrast sensitivity than younger subjects for most spatial frequencies above 4 cycles/degree. We may thus conclude that both the binocular and monocular contrast sensitivity seemed independent of age within the range of 6 to 40 years. For higher ages studied (above 60 years), there was a loss of sensitivity in the middle and high frequency regions.

Adolescent↗
PubMed1992

Binocular contrast summation and inhibition in amblyopia. The influence of the interocular difference on binocular contrast sensitivity.

The monocular contrast sensitivity loss in amblyopia is well documented. We investigated the influence of interocular sensitivity difference on binocular contrast sensitivity in amblyopia. Monocular and binocular contrast sensitivity functions of six amblyopes (three strabismic and three anisometropic) were measured. The monocular contrast sensitivity loss depended on the type of amblyope. Anisometropic amblyopes generally showed high frequency losses. Strabismic amblyopes showed losses at both low and high spatial frequencies. Binocular performance was assessed in terms of binocular ratios (binocular/non-amblyopic). A binocular ratio greater than 1 indicates binocular summation (binocular > monocular) while a ratio less than 1 shows binocular inhibition (binocular < monocular). In all subjects, the binocular ratio depended on the difference between the amblyopic and the non-amblyopic eye. Minimal interocular difference produced binocular summation, the magnitude of which decreased as the difference between the two eyes increased. Further increases in the monocular difference produced binocular inhibition. Anisometropic amblyopes showed a greater degree of binocular summation at low spatial frequencies compared to strabismic amblyopes. Both types of amblyopes showed binocular inhibition at high spatial frequencies. Clinical implications of binocular summation and inhibition in amblyopia are discussed.

Adolescent↗
PubMed1990

[Contrast sensitivity and diabetes].

Contrast sensitivity has been assessed in 24 diabetic patients in order to test the hypothesis that contrast sensitivity is impaired in the early stages of diabetes mellitus. All patients had 20/20 vision. Some evidence of visual dysfunction was observed in 33% of the diabetics with no retinopathy and 83% of the 6 patients with retinopathy when compared to 48 age-matched controls. Contrast sensitivity was mainly reduced in the mid-range spatial frequencies and correlated with the degree of retinopathy. The accurate assessment of visual dysfunction in diabetes is very important, as new drugs (i.e. aldose reductase inhibitors) are currently under evaluation.

Contrast Sensitivity↗
PubMed1992

[Adverse effect of antiepileptic drugs on the visual recognition--a contrast sensitivity function study].

Contrast sensitivity function (CSF) was measured in 16 patients (14-60 yr.) with epilepsy to investigate adverse effect of antiepileptic drugs on the central nervous system. Eight patients were treated with phenytoin, while 8 were given polytherapy (phenytoin in combination with phenobarbital, carbamazepine or valproic acid). Thirty-one normal controls (19-59 yr.) were also subjected to this study. Vertical sinusoidal gratings with various spatial frequencies (0.5-20.0 c/deg) were presented on a video monitor. Contrast sensitivity (reciprocal of threshold contrast) was determined at each spatial frequency. CSF of normal subjects showed an inverted U-shaped function against the spatial frequencies with a peak at 6 c/deg (medium size pattern). There was no significant difference in CSF values between normal controls and patients with epilepsy. However, 3 patients with polytherapy showed the significant reduction of contrast threshold. Since these patients did not complain of visual disturbance with normal visual acuity, CSF abnormality was considered as having subclinical visual dysfunction. These results suggest that CSF is useful for evaluating the adverse effect of antiepileptic drugs on the visual recognition, and that polytherapy is responsible for CSF abnormality. Therefore, monotherapy should be scheduled from the onset of therapy.

Adult↗
PubMed1992

Contrast sensitivity during horizontal visual pursuit: dynamic sensitivity functions.

The contrast sensitivity functions of college students for grating targets presented at angular velocities of 0, 30, 60, and 90 deg s-1 were determined for target durations of 200 and 600 ms. The most pronounced effects of target movement were evident at the mid to high spatial frequencies in which sensitivity was markedly reduced as velocity increased. These adverse effects were greatest in the 200 ms condition, in which performance was largely limited to the saccadic eye movement system. In the 600 ms condition, in which both saccadic and smooth pursuit eye movements were possible, contrast sensitivity for the low-frequency target actually improved significantly for the 30 and 60 deg s-1 targets, whereas only adverse effects of target motion were found for targets of mid and high spatial frequencies. The results are discussed in terms of the limitations of traditional visual assessment procedures and the practical and theoretical benefits of conceptualizing the joint effects of target composition and target movement.

Adult↗
PubMed1991

Contrast sensitivity in amblyopia.

Contrast sensitivity function (CSF) for sinusoid gratings of varying spatial frequencies was determined for each eye of 21 cases with unilateral amblyopia. The CSF of all amblyopic eyes, except one, showed reduced sensitivity when compared with the non-amblyopic eye of the same person. The curve showed reduction more significantly at middle and high spatial frequencies. The cut-off frequency was shifted toward lower spatial frequencies. The relationship between CSF and various degree of amblyopia was also discussed.

Adolescent↗
PubMed1990

Paired comparison of contrast sensitivity in diffractive multifocal IOLs and conventional monofocal IOLs.

Multifocal intraocular lens (IOL) optics produce a retinal image of reduced contrast, which results from splitting incoming light between multiple focal points. This study sought to determine whether the reduced-contrast image results in functional loss of contrast sensitivity. Contrast sensitivity was measured in patients in the US Food and Drug Administration (FDA) study of the 3M Diffractive IOL, using the Pelli-Robson Letter Chart. Fifty-eight of these patients, including six from our clinic, were 'best-case' patients with no pathology, and also had paired multifocal/monofocal implants. Data from these 'best-care' patients with paired eyes indicate no functional difference in contrast sensitivity. Additional data obtained on our six patients with the Regan Low Contrast Charts suggest small predictable differences may exist for some patients at very low contrast levels. Further study is needed to determine whether these differences have functional significance.

Aged↗
PubMed1990

Gain, noise, and contrast sensitivity of linear visual neurons.

Contrast sensitivity is a measure of the ability of an observer to detect contrast signals of particular spatial and temporal frequencies. A formal definition of contrast sensitivity that can be applied to individual linear visual neurons is derived. A neuron is modeled by a contrast transfer function and its modulus, contrast gain, and by a noise power spectrum. The distributions of neural responses to signal and blank presentations are derived, and from these, a definition of contrast sensitivity is obtained. This formal definition may be used to relate the sensitivities of various populations of neurons, and to relate the sensitivities of neurons to that of the behaving animal.

Animals↗
PubMed1992

Effect of contact lens correction of sine wave contrast sensitivity in keratoconus patients after penetrating keratoplasty.

Contrast sensitivity testing reveals visual deficits not detected by standard acuity tests, providing a more sensitive measure of visual performance. Sine wave contrast sensitivity functions were examined for spectacle and contract lens correction of keratoconic eyes after penetrating keratoplasty (PKP). Contrast sensitivity was significantly higher for middle and high spatial frequencies with a rigid gas permeable contact lens than with glasses, even when Snellen acuity was identical for both forms of correction. Contrast performance correlated with subjective assessments of vision quality. This may be related to the quality of the keratometry mire images and suggests that mild irregularities in graft contour may be affecting contrast sensitivity. When considering the options for optical correction of grafted eyes, an evaluation of contrast sensitivity may help determine whether contact lens correction would optimize visual performance.

Adult↗
PubMed1990

Normative contrast sensitivity data for young children.

Contrast sensitivity (CS) was measured in children ages 3 to 7 years using the Vistech Contrast Sensitivity distance chart (VCTS 6500). The purpose of the study was to determine how effectively the technique could be used with young children and to establish normative data for this age group. Of 286 children participating in a vision screening, the contrast sensitivity function (CSF) was measurable on 241 (84%) under binocular conditions and 229 (80%) under both binocular and monocular conditions. The 219 binocular CSF's and 208 monocular CSF's obtained from visually normal children were used to establish normative data and then compared to similar data from 50 visually normal young adults. The results indicated that there is an effect of age between 3 and 7 years, children are significantly less sensitive than adults, and adult-like levels of CS are not yet reached at 7 years of age. In addition, although the children's mean contrast thresholds fell within the norms provided with the VCTS 6500, the variability in the children's CSF's precludes using the Vistech data for diagnostic purposes in the young. The normative data are presented to assist the clinician in evaluating CS in young children when using the VCTS 6500.

Adult↗
PubMed1992

Contrast sensitivity in patients with nuclear cataracts.

Spatial contrast sensitivity and lens density were measured in 30 subjects (18 patients with pure nuclear cataracts and 12 age-matched controls). Contrast sensitivity was assessed using two techniques: a conventional monitor method in which gratings were viewed through the cataract (overall spatial contrast sensitivity) and a laser interferometer method in which gratings were formed directly on the retina (interferometric spatial contrast sensitivity), thus reducing the effect of an opaque lens on grating contrast. The degree of lens nuclear opacity was measured by assessing the density of Zeiss Scheimpflug slit-lamp video camera images. A contrast sensitivity loss was found by using both methods; this reduction reached statistical significance only when monitor stimuli were used. There was a significant correlation between lens nuclear density and sensitivity loss at spatial frequencies from 4 to 16 cycles/degree (r = .56 to .79 and P less than .05 to less than .001). A correlation coefficient of .82 (P less than .001) characterized the relationship between visual acuity (log of the minimal angle of resolution) and lens density. Nuclear lens opacity significantly affects contrast sensitivity; pure nuclear cataracts produce spatial visual losses at intermediate and high spatial frequencies.

Aged↗
PubMed1991

Isolating the effects of primary open-angle glaucoma on the contrast sensitivity function.

We evaluated spatial contrast sensitivity functions in age-matched and lens density-matched healthy eyes, eyes with primary open-angle glaucoma, and eyes with ocular hypertension. We also controlled for refraction, visual acuity, pupil size, and previous ocular history. We found an overall reduction in contrast sensitivity for the glaucomatous eyes with a significant difference at 12 cycles per degree (P less than .012). Eyes with ocular hypertension were not significantly different from normal eyes. Significant differences were noted at several spatial frequencies with less careful controls for age and lens effects. We concluded that spatial contrast sensitivity may be a useful adjunctive diagnostic test for glaucoma, but interpreting the results without other clinical data may lead to errors in diagnosis.

Aged↗
PubMed1991

The importance of measuring binocular contrast sensitivity in unilateral cataract.

Monocular and binocular contrast sensitivities were measured in patients with uniocular cataract. The cataractous eye showed a greater monocular loss at higher spatial frequencies compared to lower spatial frequencies. Binocular contrast sensitivity depended on the contrast sensitivity differences between the two eyes. At low spatial frequencies, where the monocular sensitivity difference was minimal, binocular summation was obtained. As the sensitivity difference increased at higher spatial frequencies, the binocular contrast sensitivity decreased steadily until it reached a level below the sensitivity of the cataractous eye, demonstrating binocular inhibition. The clinical implications of binocular inhibition obtained with uniocular cataract are discussed.

Aged↗
PubMed1990

Peripheral contrast sensitivity in glaucoma and ocular hypertension.

Contrast sensitivity has been measured in patients with glaucoma and ocular hypertension, the latter graded into high, medium, and low risk clinical groups. Measurements were made centrally and peripherally at 10 degrees, 15 degrees, 20 degrees, and 25 degrees off-axis at each of the four meridians 45 degrees, 135 degrees, 225 degrees, and 315 degrees. A sine wave grating of 1.9 cycles/degree, reversing at 1 Hz was used. It was displayed on a 100-Hz refresh rate monitor. Normal values were established to compare those from 41 eyes from patients with either primary open angle glaucoma (POAG) with minimal field loss detectable on a Humphrey perimeter, or raised IOP and/or disc changes but no field loss (OH). Those with POAG had normal central contrast sensitivity, but at 20 degrees and 25 degrees eccentricity the values were greater than 2 standard deviations above the normal mean. This was also the case for high risk OH, but not for low risk patients. All the high risk patients except one who had abnormal peripheral contrast sensitivity had possible field defects (threshold elevation at one or more points more than 5 but less than 10 dB above normal mean). Only one of those with normal peripheral contrast sensitivity had such 'suspect points'. The results are assessed in terms of screening of glaucoma suspects.

Contrast Sensitivity↗
PubMed1991

[Contrast sensitivity in aphakia and artiphakia].

Examination of the contrast sensitivity in aphakic eyes corrected by glasses and in artephakias provides information which cannot be obtained by measurement of visual acuity and is thus a suitable supplement of the basic test of visual functions. Contrast sensitivity declines significantly with advancing age. Contrast sensitivity of aphakic eyes corrected by glasses corresponds to values of contrast sensitivity of phakic eyes of the same age group. Artephakias with an iris clip lens have a contrast sensitivity reduced by cca one half as compared with a control group, while in artephakias with a posterior chamber lens there is a decline by one third, as compared with a control groups of the same median age.

Adult↗