Loss Of Contrast Sensitivity Research Articles

Normal Values for Photopic and Mesopic Letter Contrast Sensitivity

The exponential increase of patients having refractive surgery has increased the number of patients with night vision disturbances, such as decreased contrast sensitivity. However, there are no standard contrast sensitivity scales in normal persons in the mesopic range. We describe Pelli-Robson contrast sensitivity under photopic and mesopic luminance conditions in a large Spanish population over a wide range of age groups to provide normal values. A further aim was to evaluate the effect of photopic visual acuity on photopic and mesopic contrast sensitivity. A cross-sectional study was performed on 292 participants stratified by age into six groups. Binocular contrast sensitivity was determined with best spectacle correction using the Pelli-Robson letter chart at 1 m under photopic (85 cd/m2) and mesopic (0.15 cd/m2) luminance conditions. Phototopic letter contrast sensitivity began to decrease gradually from the 61 to 70-year-old age group onward, and for mesopic conditions, from the 51 to 60-year-old age group onward. The reduction in mean contrast sensitivity between the oldest and the youngest age groups was 0.20 log units (photopic) and 0.33 log units (mesopic). Loss in contrast sensitivity due to luminance (two successive triplets) increased slightly with age. Both photopic and mesopic letter contrast sensitivity significantly improved as photopic visual acuity increased. Under mesopic conditions, Pelli-Robson contrast sensitivity began to decline 1 decade earlier than under photopic conditions and was affected by visual acuity. Normal values for mesopic contrast sensitivity could be of help in deciding whether mesopic function is normal or a decrease in contrast sensitivity is pathologic in nature.

Ocular dominance column width and contrast sensitivity in monkeys reared with strabismus or anisometropia.

To study the relationship between the width of ocular dominance columns in primary visual cortex and spatial contrast sensitivity functions in monkeys with strabismus or anisometropia during infancy. Adult monkeys having had monocular visual abnormalities induced in infancy were tested behaviorally for spatial contrast sensitivity and then subjected to functional enucleation of one eye to reveal the ocular dominance columns (ODCs) of the primary visual cortex by cytochrome oxidase (CO) staining. The relative widths of the left and right eyes' ODCs were measured and related to the contrast sensitivity functions. The relative widths of the ODCs having input from eyes with strabismic or anisometropic amblyopia were reduced in proportion to the age of onset and the duration of the early visual abnormality. The relative losses in contrast sensitivity were in ordinal agreement with the losses in relative width of the ODCs. Amblyopia induced by the early monocular abnormalities of strabismus or anisometropia is proportional to the loss in cortical afference as reflected in the reduction in width of the respective ODCs in the primary visual cortex.

Mesopic contrast sensitivity in the presence or absence of glare in a large driver population.

To evaluate mesopic contrast sensitivity in conditions of glare and no glare in a vehicle driver population, and to explore the effects of age, habitual spectacle correction, photopic visual acuity and driving exposure. A cross-sectional study was performed on 297 drivers stratified by age into six groups. The mesopic contrast sensitivity was measured in the absence or presence of glare using the Mesotest II (Oculus, Germany) in each subject both with habitual and best spectacle correction. A questionnaire on the subject's driving habits was completed. There were no significant differences between contrast sensitivity measured with habitual or best spectacle correction. In conditions of no glare, the mesopic contrast sensitivity gradually got worse from 51 to 60 years onwards, and from 41 to 50 years onwards in the presence of glare. In both conditions, the total decrease in contrast sensitivity was 0.3 log units. The with-glare and without-glare mesopic contrast sensitivity improved as photopic visual acuity increased. Forty-five per cent of drivers who reported difficulties in driving at night were unable to perform any of the tests with glare, compared to 20% without glare. However, the effect of driving habits on contrast sensitivity was only significant in the oldest age group. The mesopic contrast sensitivity and glare sensitivity seem to be stable until the age of 50 years, from which point they start to decline at a rate of 0.1 log contrast sensitivity loss per decade. Drivers with poor visual acuity and/or older drivers who avoided night driving presented worse mesopic contrast sensitivity and greater glare sensitivity.

Light scattering and optical aberrations as objective parameters to predict visual deterioration in eyes with cataracts

Purpose: To predict the visual deterioration of eyes with cortical (CC) or nuclear (NC) cataract from objective data on ocular higher-order aberration (HOA) and forward (FLS) and backward light scattering (BLS). Setting: Osaka University Medical School, Osaka, Japan. Methods: Twenty-two eyes with mild NC, 41 eyes with mild CC, and 11 normal eyes were examined. Higher-order aberrations were calculated with the Zernike polynomials up to the fourth order from the values obtained by wavefront analysis using the Hartmann-Shack aberrometer. Forward light scattering was calculated from the size of the aberrometer spot images for the central 4 mm, and backward light scattering (BLS) was calculated from the optical density of the Scheimpflug images. The relationship between the area under the log contrast sensitivity function (AULCSF) curve and HOAs, FLS, and BLS was examined. Results: Area under the log contrast sensitivity function was moderately correlated with the HOAs, FLS, and BLS. Multiple linear regression analysis revealed that the AULCSF was predicted by the linear combination of these variables ( R 2=.484, P<.001). Area under the log contrast sensitivity was predicted by BLS and HOA ( R 2=.555) in the NC group and by FLS and HOAs ( R 2=.540) in the CC group. Conclusions: Loss of contrast sensitivity was predominantly due to BLS and HOA in eyes with NC and FLS and HOA in eyes with CC. Higher-order aberrations, FLS, and BLS, variables that are obtained objectively, can be used to predict quantitatively the visual deterioration in cataractous eyes.

Effect of positive and negative defocus on contrast sensitivity in myopes and non-myopes

This study investigated the effect of lens induced defocus on the contrast sensitivity function in myopes and non-myopes. Contrast sensitivity for up to 20 spatial frequencies ranging from 1 to 20 c/deg was measured with vertical sine wave gratings under cycloplegia at different levels of positive and negative defocus in myopes and non-myopes. In non-myopes the reduction in contrast sensitivity increased in a systematic fashion as the amount of defocus increased. This reduction was similar for positive and negative lenses of the same power ( p=0.474). Myopes showed a contrast sensitivity loss that was significantly greater with positive defocus compared to negative defocus ( p=0.001). The magnitude of the contrast sensitivity loss was also dependent on the spatial frequency tested for both positive and negative defocus. There was significantly greater contrast sensitivity loss in non-myopes than in myopes at low-medium spatial frequencies (1–8 c/deg) with negative defocus. Latent accommodation was ruled out as a contributor to this difference in myopes and non-myopes. In another experiment, ocular aberrations were measured under cycloplegia using a Shack–Hartmann aberrometer. Modulation transfer functions were calculated using the second order term for defocus as well as the fourth order Zernike term for spherical aberration. The theoretical maximal contrast sensitivity based on aberration data predicted the measured asymmetry in contrast sensitivity to positive and negative defocus that was observed in myopic subjects. The observed asymmetry in contrast sensitivity with positive and negative defocus in myopes may be linked to the altered accommodative response observed in this group.

Orientational contrast sensitivity and chromatic contrast thresholds in multiple sclerosis

PurposeTo investigate abnormalities of orientational contrast sensitivity (CS) and chromatic contrast threshold (CCT) in multiple sclerosis (MS). DesignCase control study. MethodsNine subjects (mean age, 42 ± 11 years; range, 20–62 years) with MS, an expanded disability status scale of 3 or less, and normal visual acuity (VA) (logarithm of the minimum angle of resolution [logMAR] VA less than .1) in the tested eye were age-matched with 20 controls. Achromatic CS and CCT were measured using static, computer-generated sinusoidal gratings displayed on a high-resolution monitor. The CS and CCT of each subject were determined using a randomized double-staircase reversal algorithm; CS was measured at five spatial frequencies with horizontal orientation and three with vertical orientation; CCT was measured along the red-green and tritan confusion axes. The sensitivity thresholds of subjects were examined in relation to the mean sensitivity of controls for each spatial frequency. ResultsTwo subjects had loss of horizontal and vertical CS, and three had isolated vertical loss. When compared with the control mean, there were significant reductions in red-green (P = .016) and tritan (P = .016) discrimination thresholds. ConclusionThis study used a computerized psychophysical test designed to minimize many of the test errors associated with earlier studies. It provides confirmatory evidence that MS may be associated with a loss of orientational CS and color vision, in the absence of reduced VA.

Contrast sensitivity loss with aging: sampling efficiency and equivalent noise at different spatial frequencies.

The relative contributions of optical and neural factors to the decrease in visual function with aging were investigated by measurement of contrast detection at three different spatial frequencies, in the presence of external noise, on young and older subjects. Contrast detection in noise functions allows two parameters to be measured: sampling efficiency, which indicates neural changes, and equivalent noise, which demonstrates optical effects. Contrast thresholds were measured in the presence of four levels (including zero) of externally added visual noise. Measurements were obtained from eight young and eight older visually normal observers. Compared with young subjects, older subjects showed significantly (p < 0.05) lower sampling efficiencies at spatial frequencies of 1 and 4 cycles per degree (c/deg) and significantly higher equivalent noise levels for gratings of 10 c/deg. Neural and optical factors affect contrast sensitivity loss with aging differently, depending on the spatial frequency tested, implying the existence of different mechanisms.

Contrast-processing deficits in melanoma-associated retinopathy.

To evaluate the hypothesis that patients with melanoma-associated retinopathy (MAR) have a selective functional loss within the magnocellular (MC) pathway of the cone system, with sparing of parvocellular (PC) pathway function. Two patients with MAR, ages 57 and 61 years, with normal Snellen visual acuity, participated in the study. Contrast sensitivity was measured at spatial frequencies ranging from 0.25 to 8 cycles per degree (cpd), using two paradigms (steady pedestal and pulsed pedestal) designed to assess the functional integrity of the MC and PC pathways, respectively. Results in patients with MAR were compared with those in 10 visually normal observers, aged 23 to 57 years. Both patients with MAR showed a loss of contrast sensitivity compared to normal observers, but the pattern of loss differed for the two testing paradigms. For the steady-pedestal paradigm (presumed MC-pathway mediation), the patients' sensitivity loss was greatest at the lowest spatial frequency (0.25 cpd) and the sensitivity loss decreased systematically with increasing spatial frequency. For the pulsed-pedestal paradigm (presumed PC-pathway mediation), the sensitivity loss was greatest at an intermediate spatial frequency of 1 cpd. For both paradigms, the patients' sensitivities were within the normal range at the highest spatial frequency (8 cpd), consistent with their normal visual acuity. The contrast sensitivity deficits of patients with MAR under photopic conditions are not specific to the MC pathway, as proposed previously, but instead are related to the spatial frequency of the test target. The overall pattern of contrast sensitivity loss shown by the patients with MAR is consistent with the dysfunction at the level of the retinal bipolar cells that is presumed to underlie the MAR syndrome.

Effect of intraocular lens implantation on visual acuity, contrast sensitivity, and depth of focus

Purpose: To determine the role of spherical and irregular aberrations in the optics of the natural eye and after intraocular lens (IOL) implantation in terms of visual acuity, contrast sensitivity, and depth of focus. Setting: Laboratory of Experimental Ophthalmology, University of Groningen, Groningen, The Netherlands. Methods: Visual acuity and defocus-specific contrast sensitivity in 11 pseudophakic patients (IOL group) and 27 age-matched phakic subjects were compared. The results were obtained psychophysically. Spherical and irregular aberrations were subsequently estimated by comparing the measured myopic shift (optimum focus of contrast sensitivity at 4 cycles per degree [cpd] compared to that at 16 cpd) and depth of focus with those of theoretical eye models with varying amounts of irregular and spherical aberrations. Results: The best corrected visual acuity and best corrected contrast sensitivity in the IOL group did not significantly differ from that in the phakic group. The depth of focus was larger in the IOL group at a pupil diameter of 6.0 mm ( P<.05). Comparison with theoretical eye models suggested a higher amount of spherical aberration in the IOL group; irregular aberration was almost the same in both groups. Conclusions: There was a higher amount of spherical aberration in the IOL group, related to a larger depth of focus, without loss of contrast sensitivity at optimum focus or loss of visual acuity. This might contribute to better quality of vision in pseudophakic subjects than in presbyopic phakic subjects.

Contour integration in amblyopic monkeys

Amblyopia is characterized by losses in a variety of aspects of spatial vision, such as acuity and contrast sensitivity. Our goal was to learn whether those basic spatial deficits lead to impaired global perceptual processing in strabismic and anisometropic amblyopia. This question is unresolved by the current human psychophysical literature. We studied contour integration and contrast sensitivity in amblyopic monkeys. We found deficient contour integration in anisometropic as well as strabismic amblyopic monkeys. Some animals showed poor contour integration in the fellow eye as well as in the amblyopic eye. Orientation jitter of the elements in the contour systematically decreased contour-detection ability for control and fellow eyes, but had less effect on amblyopic eyes. The deficits were not clearly related to basic losses in contrast sensitivity and acuity for either type of amblyopia. We conclude that abnormal contour integration in amblyopes reflects disruption of mechanisms that are different from those that determine acuity and contrast sensitivity, and are likely to be central to V1.

Topographic change in the central macula coupled with contrast sensitivity loss in diabetic pregnancy.

To study macular topography and contrast sensitivity (CS) in diabetic and nondiabetic women during pregnancy and post partum. A prospective study of 46 pregnant women with insulin-dependent diabetes and 11 nondiabetic pregnant controls. Macular surface topography was analyzed by Heidelberg Retinal Tomograph. Volume above the reference plane (VARP) was measured with 1.0-, 1.5-, 2.0-, and 3.0-mm-diameter circles. CS was measured with the Vistech 6500 Contrast Test System. The diabetic women had greater VARP than the controls measured with the 1.5-mm diameter circle. In diabetic women, the mean VARP was 0.084+/-0.064 mm(3) (mean +/- SD) in the first trimester, 0.080 +/- 0.056 mm(3) in the third trimester, and 0.087 +/- 0.067 mm(3) 3 months post partum compared with the values of 0.069+/-0.043, 0.054+/-0.024, and 0.036+/-0.020 mm(3) in the controls ( P=0.036 between groups). In diabetic women requiring laser treatment, the difference from controls was more significant ( P<0.001). CS at 3 cpd and 6.0 cpd was lower in diabetic women than in controls throughout pregnancy and post partum ( P=0.012 and P=0.043). A statistically significant negative correlation appeared between macular topography and CS during the third trimester; between cpd 6 and VARP 1.5 mm ( r=-0.471, P=0.001), and between cpd 6 and VARP 2.0 mm ( r=-0.446, P=0.002). In the diabetic women, especially in those with clear progression of retinopathy during pregnancy and post-partum, the macula seemed to be slightly more elevated than in the controls, and CS was lower at mid-range spatial frequencies. CS loss in the diabetic women correlated with macular elevation during the third trimester.

Border distinctness in amblyopia

On the basis of the contrast sensitivity loss in amblyopia which mainly affects higher spatial frequencies, one would expect amblyopes to perceive sharp edges as blurred. We show that they perceive sharp edges as sharp and have veridical edge blur perception. Contrary to the currently accepted view, this suggests that the amblyopic visual system is not characterized by a blurred visual representation.

Noise Provides Some New Signals About the Spatial Vision of Amblyopes

Amblyopia results in a loss of contrast sensitivity and position acuity. Here we report the results of experiments using noise to try to better understand the nature of the neural losses in amblyopia. In the first experiment, we used noise to derive the template or classification image used to detect a target and to discriminate its position. We found that some amblyopic observers show markedly abnormal templates for the position task and moderately abnormal classification images for the detection task; however, the abnormal template could not fully account for the loss of performance (efficiency). Reduced efficiency in the amblyopic visual system may reflect a poorly matched template, a high fraction of internal to external noise, or both. Comparison of the observers' performance with that of their template suggests that the amblyopes have a high fraction of internal (relative to external) noise. To analyze the internal noise further, we used a "double-pass" technique, in which observers performed the identical experiment twice. The amount of disagreement between the two experiments provides another estimate of the fraction of internal noise. Amblyopes show a much higher fraction of stimulus-dependent internal noise than do normal observers. We conclude that the loss of efficiency in amblyopia is attributable in part to a poorly matched template, but to a greater degree, to a high fraction of internal (relative to external) noise.

Early contrast sensitivity loss and oxidative damage in healthy heavy smokers

AbstractObjective: The purpose of this study was 1) to evaluate visual functions and the activities of antioxidant enzymes in plasma and erythrocytes in smokers in comparison with non‐smokers, 2) to evaluate the correlations between visual functions and the oxidant/antioxidant system. We hypothesized that the changes in antioxidant system and consequently lipid peroxidation depend on smoking may affect sophisticated visual tests including contrast sensitivity (CS) and pattern visual evoked potentials (PVEP)Subjects: This non‐randomised control study included 24 chronic, heavy smokers who were smoking more than 20 cigarettes per day at least for last 10 years. Sixteen age and sex‐matched, healthy, non‐smokers were taken as controls. All volunteer subjects were accumulated from the outpatient clinic. To rule out the effect of alcoholism and malnutrition, we chose young, healthy heavy smokers who maintained adequate diet and who had no alcohol consumption history.Following visual acuity and color vision tests, all subjects were applied to CS and PVEP tests. Values of CS, N75‐P100 amplitude and P100 wave latency were compared between the study and control subjects. Superoxide dismutase (SOD) and catalase (CAT) activities in plasma and erythrocytes were determined by spectrophotometer. Plasma malondialdehyde (MDA) level, as an end product of lipid peroxidation, was assessed by spectrofluorometric method.Results: CS was determined to be significantly reduced in smokers compared to non‐smokers, although central vision and PVEP responses were not affected. Erythrocyte SOD activity and plasma MDA levels were significantly increased in smokers compared to controls. There were positive correlations between plasma SOD and erythrocyte SOD; CS and erythrocyte SOD; and CS and plasma SOD.Conclusions: The results suggest the possible association between early CS loss and increase in antioxidant enzyme activities thus reflecting an increased oxidative damage due to cumulative effect of chronic smoking. Elevated concentrations of lipid peroxidation products in the plasma of smokers may directly show the increased oxidative damage in these subjects.

Processamento visual da forma em idosos: curvas de limiar de contraste para freqüências angulares e senoidais

O objetivo deste trabalho foi mensurar curvas de sensibilidade ao contraste para freqüências angulares e senoidais em idosos. Foram estimados limiares de contraste para um grupo de jovens com idade entre 20-26 anos e um grupo de idosos com idade entre 60-67 anos. Todos os sujeitos apresentavam acuidade visual normal e se encontravam livres de doenças oculares identificáveis. As freqüências angulares e senoidais estimadas com o método psicofísico da escolha forçada foram: 2, 4, 8, 16, 24, 32, 48, 64 e 96 ciclos/360º e 0.5, 1, 2, 3, 4, 6 e 9 cpg, respectivamente. Os resultados mostraram declínio na sensibilidade ao contraste nos idosos nas freqüências angulares e senoidais médias e altas comparados aos jovens. Encontramos, ainda, que a sensibilidade ao contraste dos idosos nas freqüências angulares baixas é melhor do que a dos jovens. Estes resultados são consistentes com alterações na sensibilidade ao contraste relacionados ao processo de envelhecimento.

The impact of acuity on performance of four clinical measures of contrast sensitivity in Alzheimer's disease.

Investigations of contrast sensitivity losses in Alzheimer's disease (AD) have yielded mixed findings, with some investigators reporting deficits and others not. Potential reasons for these discrepancies include differences between samples and assessments utilized and the failure of some investigators to account for acuity differences between groups. To investigate these issues, we administered four clinical contrast sensitivity assessments to the same group of AD patients and elderly control participants and examined the impact of acuity on performance for each assessment. Results revealed group differences across the spatial frequency range. Further, group acuity differences significantly affected performance on two of the four measures (the Regan and the Vistech but not on the Pelli-Robson or Freiburg assessments). Information regarding the availability of established age norms, test-retest reliability data, and other factors including the time, cost, and training needed to administer each measure is provided to aid clinicians and researchers in their search for an effective measure of contrast sensitivity.

Photodynamic Therapy for Subfoveal Choroidal Neovascularisation in Various Diseases among which Age-related Macular Degeneration: An Update

Summary Photodynamic therapy (PDT) with Verteporfin represents a major advance in the treatment of subfoveal choroidal neovascularisation (CNV). Patients presenting this disease tend to lose about 2 lines of visual acuity in the first 3–6 months after PDT, after which vision can be stabilised for at least 4 years. Contrast sensitivity loss secondary to subfoveal CNV is also strongly reduced by PDT. The latter is essential to the quality of life and functional ability, especially in low vision patients. In addition PDT of subfoveal CNV was shown to be quite safe. Some of the recent data obtained in the Visudyne clinical trials are summarised with an emphasis on subgroup analysis. The observed initial loss in visual acuity, the necessity for repetitive treatment and the inherent relatively high cost of the procedure, as well as the lack of response in some subgroups of patients, has led to the search for improvements on the initial procedure. In this paper we present some of the approaches taken. Finally, the selectivity issues central to PDT of subfoveal CNV are discussed.

Effect of defocus on contrast sensitivity in myopes and non‐myopes

Purpose: Myopes have altered accommodative responses when compared with non‐myopes. We examined the contribution of the optical input to this known altered accommodative response by assessing the defocused contrast sensitivity function in myopes and emmetropes.Methods: Contrast sensitivity (CS) to 20 spatial frequencies was measured under cycloplegia, with up to ±3 D of defocus, in myopes and non‐myopes. The differences in the contrast sensitivity functions as a result of defocus were analysed for the different spatial frequencies in the two groups. In addition, the optimum defocus at which peak contrast sensitivity occurred was compared between the two groups.Results: The loss in contrast sensitivity with defocus was less symmetrical with positive and negative defocus in the myopic group, although there was no latent accommodation left following cycloplegia. Defocus decreased contrast sensitivity symmetrically in non‐myopes. The magnitude of decrease in CS was dependent on the spatial frequency tested, and was significantly different in myopes and non‐myopes at 3 and 6 c deg−1.Conclusions: Differences in the effects of blur on CS exist between myopes and non‐myopes. Existing models of spherical aberration may explain this asymmetry in positive and negative defocus in myopes.

Computer colour tests for the major causes of blindness using an inexpensive PC system

Background: Computer‐graphics methods of assessing acquired losses of colour vision are superior in many ways to all others. They can employ briefly flashed stimuli, that can be presented in the retinal periphery; any luminance signal can also be masked by dynamic random luminance noise; and chromaticity can be varied very precisely. We have devised a program that is designed to detect and quantify disturbances in the three major blinding conditions (glaucoma, ARM and diabetes).Methods: The tests can be performed very rapidly, using standard PCs.Results: Normal results from age‐matched groups prove prominent tritan losses in all 3 three conditions. In diabetes, relatively large abnormalities can be detected before the appearance of mild background retinopathy, and worsen with the appearance of microaneurysms. In suspected glaucoma, abnormalities can be detected when conventional perimetry is ambiguous. There is a good correlation with minor changes on the Heidelberg Retinal Tomograph (HRT). The loss is related to IOP. In ARM, even with normal visual acuity, very large losses of tritan contrast sensitivity can be seen. Although patients can see the colours on the monitor screen, the targets (small optotypes) cannot be recognised, apparently because of the presence of very small tritan scotomas, which can be demonstrated when the target is flashed briefly.Conclusions: Colour vision testing permits rapid screening of patients at risk of developing sight‐threatening disorders, and thus is potentially of considerable use in health‐care programmes.

A Clinical Evaluation of an Aspheric Multifocal Intraocular Lens and its Implications for the Developing World

To evaluate the clinical performance of a new aspheric multifocal intraocular lens (IOL), and to compare the results with a corresponding monofocal IOL. Two groups of 20 patients each were implanted with a multifocal and monofocal IOL and prospectively studied. Distance and near vision, contrast sensitivity, depth of focus, and quality of vision were assessed in both groups. In 85% of multifocal cases and 100% of monofocal cases, the corrected distance vision was 6/9 or better. With distance correction, 80% of multifocal cases had near vision of N9 or better against 10% of monofocal cases. The mean addition required for near vision N6 was +0.8 diopters (D) and +2.6 D in the multifocal and monofocal groups, respectively. Multifocal cases showed significantly decreased contrast sensitivity and increased depth of focus. Multifocal IOLs are a good option for those with nonexacting visual requirements. The loss in contrast sensitivity seems to be an acceptable trade-off for satisfactory unaided near vision.