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PubMed2000

The magnocellular deficit theory of dyslexia: the evidence from contrast sensitivity.

A number of authors have made the claim that dyslexia is the result of a deficit in the magnocellular part of the visual system. Most of the evidence cited in support of this claim is from contrast sensitivity studies. The present review surveys this evidence. The result of this survey shows that the support for the magnocellular deficit theory is equivocal. In the case of spatial contrast sensitivity there clearly are results that are consistent with the magnocellular deficit theory; however, these results are outnumbered both by studies that have found no loss of sensitivity and by studies that have found contrast sensitivity reductions that are inconsistent with a magnocellular deficit. Many of the studies of temporal contrast sensitivity are also difficult to reconcile with a magnocellular deficit. The evidence from studies of contrast sensitivity is therefore highly conflicting with regard to the magnocellular system deficit theory of dyslexia.

Contrast Sensitivity↗

PubMed1980

Contrast sensitivity in amblyopia due to stimulus deprivation.

Contrast sensitivity functions for sinusoidal gratings of varying spatial frequency and stimulus duration were determined for both eyes of 2 patients with amblyopia due to early occlusion and lid closure. The amblyopic eyes showed reduced contrast sensitivity over a wide range of spatial frequencies and stimulus durations, and the temporal integration time of the amblyopic eye was increased by comparison with the non-amblyopic eye at high spatial frequencies. When the gratings were flickered at 10 Hz the sensitivity for both flicker and pattern detection was reduced in the amblyopic eye over the entire spatial frequency range. Abnormal flicker perception by the amblyopic eyes was also evident in the reduced photopic luminosity functions of these patients.

Adult↗

PubMed1996

The association of postoperative subjective visual function with acuity, glare, and contrast sensitivity in patients with early cataract.

BACKGROUND: It has been shown in our previous studies that early cataracts affect vision in ways that can be measured by objective means and that this objective impairment in visual acuity, glare, and contrast sensitivity can be successfully reversed by cataract surgery. OBJECTIVE: To evaluate the association of subjective visual function with objective measures of acuity, glare, and contrast sensitivity in patients who were symptomatic from early cataract. METHODS: We administered a task-oriented questionnaire prior to and 4 months after cataract surgery to patients who were symptomatic from early cataract (median preoperative ETDRS [Early Treatment Diabetic Retinopathy Study] visual acuity of 20/40 [range, 20/20 to 20/80]); ETDRS visual acuity, disability glare, and contrast sensitivity were also measured at those times. RESULTS: Uncomplicated cataract surgery resulted in resolution or improvement of subjective symptoms for the great majority of subjects, and in a few subjects new symptoms developed or current symptoms worsened. We found a positive association between postoperative improvement in subjective visual function (as measured by the questionnaire) and postoperative improvement in objective visual function (as measured by visual acuity and contrast sensitivity). We also found that the greater the degree of preoperative impairment in objective visual function (as measured by visual acuity and contrast sensitivity), the greater the postoperative improvement in subjective visual function (as measured by the questionnaire). No such association was found for our disability glare test. CONCLUSIONS: Cataract surgery for symptomatic individuals with mild impairment in visual acuity does relieve visual symptoms, and preoperative measurement of contrast sensitivity can help determine who with early cataract is most likely to report subjective improvement in vision.

Adult↗

PubMed1990

Contrast sensitivity as a function of focus in patients with the diffractive multifocal intraocular lens.

Contrast sensitivity as a function of focus and visual acuity as a function of contrast were investigated in 19 patients with a diffractive multifocal intraocular lens and compared with 19 control patients with a conventional monofocal implant. The contrast sensitivity of the multifocal patients followed a bimodal curve with a maximum sensitivity at the far focus and a second peak at the near focus, corresponding to about +3 diopters in the spectacle plane. The maximum sensitivity of the multifocal group was 0.14 log units lower than the control group (P less than .05). In the near region, the contrast sensitivity of the multifocal patients exceeded that of the control group from +2 diopters and inward. No difference in distance visual acuity was found with high contrast letters. With intermediate contrast letters, the visual acuity of the multifocal patients was lower than that of the control group (P less than .05).

Aged↗

PubMed2004

Influence of spectacle-related changes in retinal image size on contrast sensitivity function after laser in situ keratomileusis.

PURPOSE: To evaluate changes in contrast sensitivity after laser in situ keratomileusis (LASIK) for the correction of myopia using a monitor-based method and considering the preoperative minification effect of high-diopter spectacles. SETTING: Department of Ophthalmology, University of Vienna Medical School, Vienna, Austria. METHODS: Fifteen eyes of 11 patients had LASIK to correct myopia. The best corrected visual acuity (BCVA) and contrast sensitivity function (CSF) were measured preoperatively and 1, 3, and 6 months postoperatively using the AcuityMax (Science 2020) computer program. The error in contrast sensitivity measurement due to different angular sizes of the test figures deriving from the spectacle refractions before and after LASIK were considered. RESULTS: Preoperatively, and at 1, 3, and 6 months, the mean Snellen BCVA was 0.93 +/- 0.19 (SD), 0.80 +/- 0.26, 0.85 +/- 0.21, and 0.84 +/- 0.27, respectively. The best mean CS (measured at 1.1 logMAR) was 1.17 +/- 0.05, 1.12 +/- 0.07, 1.13 +/- 0.08, and 1.18 +/- 0.04, respectively. The strongest CS changes were observed at 0.7 logMAR (6 cycles per degree), where CS was 1.10 +/- 0.07 preoperatively and 1.06 +/- 0.09, 1.07 +/- 0.12, and 1.14 +/- 0.07, at 1 month, 3 months, and 6 months, respectively. With correction for the spectacle effect, the preoperative CS was approximately 3% higher and CS at 3 months for intermediate optotype sizes was significantly inferior to preoperatively. CONCLUSIONS: With correction of different retinal image sizes before and after LASIK (due to different spectacle refraction), the CS was significantly below the preoperative values at 1 and 3 months and approached the preoperative values at 6 months. The proposed method is potentially capable of quality monitoring and method comparisons after photorefractive surgery.

Adult↗

PubMed1981

Contrast sensitivity in children with strabismic and anisometropic amblyopia. A study of the effect of treatment.

The contrast threshold of sinusoidal gratings of varying contrast and frequency was examined in children with amblyopia due to strabismus or anisometropia. In strabismic amblyopia the contrast sensitivity is depressed for only a limited band of high spatial frequencies. In anisometropic amblyopia depression of the contrast sensitivity function (CSF) was found over the whole frequency range. The CSF could not be predicted from the visual acuity measurements in amblyopic eyes due to strabismus, whereas a rough correlation was observed in anisometropia. During occlusion treatment of the dominant eye in anisometropia the visual acuity and the contrast sensitivity function of the amblyopic eye improved in parallel. The study indicates that the abnormalities in spatial vision are different in amblyopia due to strabismus or anisometropia during childhood. Determination of the contrast sensitivity function seems to be an additional tool besides acuity measurements to document changes of visual function during treatment of amblyopia.

Amblyopia↗

PubMed2003

Do daily wear opaquely tinted hydrogel soft contact lenses affect contrast sensitivity function at one meter?

PURPOSE: To investigate the effects of daily wear opaquely tinted hydrogel soft contact lenses on contrast sensitivity functions, as measured using the Pelli-Robson chart viewed at 1 meter. METHODS: Contrast sensitivity was measured in 48 healthy individuals before and 6 hours after soft contact lens wear. Twenty-four subjects used clear soft contact lenses and 24 used tinted soft contact lenses. RESULTS: The contrast sensitivity scores were significantly decreased monocularly and binocularly (P = 0.000 and P = 0.002, respectively) in the colored contact lens group whereas there were no significant changes in the clear contact lens group (P = 0.317 and P = 0.317, respectively). CONCLUSIONS: Color-tinted contact lenses were associated with a reduction of contrast sensitivity function. Therefore, those who wear colored contact lenses should be informed about the possible consequences of tinted contact lens wearing.

Adult↗

PubMed1982

Contrast sensitivity in diabetics with retinopathy and cataract.

Contrast sensitivity responses were determined in diabetic subjects with retinopathy, macular disease and cataract. The test proved reliable in discriminating between different degrees of cataract and between diabetics with no retinopathy, mild background retinopathy and early maculopathy. Background retinopathy was shown to produce a loss of contrast sensitivity particularly at the low and medium frequencies. These thresholds increased with macular involvement. Mild cataract was correlated with loss at the low and medium spatial frequencies, whilst moderate cataract suppressed sensitivity to all frequencies. Results are compared to colour discrimination in each patient.

Adolescent↗

PubMedDate not supplied

The development of spatial and temporal contrast sensitivity.

This paper reviews work on the development of spatial and temporal contrast sensitivity in human infants. Both electrophysiological and behavioral techniques have been used. Infants' spatial contrast sensitivity functions exhibit a large deficit in spatial resolution and overall contrast sensitivity relative to adult functions. These measurements also reveal continuous development between one and six months of age. Infants' temporal resolution does not exhibit a large deficit relative to adults'. Indeed, critical flicker frequency is essentially adult-like by two months of age. This combination of coarse spatial resolution and fine temporal resolution is analogous to what is observed in the peripheral retina of the adult visual system.

Adult↗

PubMed1999

Lack of covariation of the effects of luminance and eccentricity on contrast sensitivity.

BACKGROUND AND PURPOSE: Qualitative individual differences in visual processing along various stimulus dimensions have been previously documented. For instance, as compared to the foveal contrast sensitivity function (CSF), the peripheral CSF of some subjects shifts toward lower frequencies, but it scales down for others; also, sensitivity to low spatial frequencies increases monotonically with luminance in some subjects, but it displays a decline at high luminances in others. Although these qualitatively distinct eccentricity- and luminance-related patterns have been thoroughly described separately, their joint occurrence has never been studied. This study aimed at determining whether there is covariation between the effects of luminance and eccentricity on contrast sensitivity, i.e., whether each eccentricity-related pattern occurs with one and only one of the luminance-related patterns. METHODS: We have measured contrast sensitivity to sine-wave grating patches as a function of luminance and eccentricity in a sample of 18 subjects. RESULTS: We found positive evidence of lack of covariation between the effects of eccentricity and luminance: we found subjects who show the same eccentricity-related pattern but differ as to their luminance-related patterns, and we have also found a subject who, unlike the rest, shows qualitatively distinct luminance-related patterns at different eccentricities. CONCLUSION: The dependence of contrast sensitivity on eccentricity and luminance is subject to qualitative variations both across and within individuals, suggesting that meaningful conclusions on the effects of luminance and eccentricity on contrast sensitivity cannot be drawn when the data from all available subjects are aggregated.

Adult↗

PubMedDate not supplied

[Visual contrast sensitivity in healthy Mexican population].

This paper presents a descriptive study of visual contrast sensitivity on 224 healthy Mexican individuals. Central tendency measures, Student's t test, as well as simple frequencies were the statistical tests used for data analysis. A format to evaluate visual contrast sensitivity adequate to healthy Mexican population is proposed, taking into account that the normal visual contrast sensitivity curve of Mexicans was found to be lower than the international standards.

Adolescent↗

PubMed1995

Nimodipine, a centrally active calcium antagonist, exerts a beneficial effect on contrast sensitivity in patients with normal-tension glaucoma and in control subjects.

BACKGROUND/PURPOSE: The use of calcium antagonists in patients with normal-tension glaucoma (NTG) currently is under investigation. The aim of this study is to evaluate the effect of an acute dose of oral nimodipine, a centrally active calcium antagonist, on spatial contrast sensitivity in patients with NTG and in age-matched control subjects. METHODS: Spatial contrast sensitivity was measured using the Pelli-Robson and the Vistech 6000 charts in 14 patients with NTG and in 17 control subjects. Testing was performed at baseline and at two subsequent sessions. Measurements were recorded 2 hours after oral administration of either nimodipine or placebo in a randomized, double-masked manner. Data were analyzed using unpaired, two-tailed Student's t test for between-group comparisons and repeated measures analysis of variance for within-group comparisons. RESULTS: Using the Pelli-Robson charts, baseline contrast sensitivity was significantly lower in patients with NTG compared with control subjects (P < 0.05, unpaired Student's t test). There was a significant increase in log contrast sensitivity after administration of nimodipine compared with baseline and placebo in patients with NTG (baseline, 1.39 +/- 0.38; placebo, 1.41 +/- 0.40; nimodipine, 1.51 +/- 0.39) and in control subjects (baseline, 1.62 +/- 0.11; placebo, 1.64 +/- 0.10; nimodipine, 1.81 +/- 0.14) (P < 0.05, repeated measures analysis of variance). A similar trend was observed using the Vistech charts. CONCLUSION: These results suggest that central visual function as measured by Pelli-Robson and Vistech contrast sensitivity is impaired in eyes with NTG. An acute, oral administration of nimodipine, a calcium antagonist, improved contrast sensitivity in patients with NTG and in control subjects. The mechanism of this improvement is not fully understood. Further studies are needed to evaluate the effect of long-term administration in glaucoma.

Aged↗

PubMed1992

Abnormalities in color vision and contrast sensitivity in Parkinson's disease.

Dopamine is a neurotransmitter found in the retina. Delays in the visual evoked responses and abnormalities in contrast sensitivity occur in patients with Parkinson's disease. Improvement in the P100 has followed L-dopa therapy. Suspected abnormalities at the retinal level in Parkinson's disease are observed in reductions in photopic, scotopic, and pattern-derived electroretinograms. We studied 35 patients with Parkinson's disease and 26 controls of comparable age and visual acuities using visual evoked responses, color vision, and contrast sensitivity testing. Contrast sensitivity thresholds were significantly different at most frequencies tested, using both stationary and temporally modulated sinusoidal gratings. The total error score of the Farnsworth-Munsell 100 Hue Test revealed significant differences between the patients and controls. The contrast thresholds derived from certain spatial frequencies and the total error in color score were significantly related to the duration of disease. A stepwise discriminant analysis correctly identified 94% of the patients and 94% of the controls. The significant error in chromatic discrimination observed in Parkinson's disease patients may be due to altered intraretinal dopaminergic synaptic activity in these patients.

Color Perception↗

PubMed1989

Spatiotemporal contrast sensitivity and colour vision in multiple sclerosis.

Measures of contrast sensitivity and colour vision were taken from a group of 18 multiple sclerosis patients. Contrast sensitivity losses, measured at 5 spatial frequencies and 4 temporal frequencies, were found to be significant in 11 patients. Red/green (Rayleigh equation) and green/blue (Engelking-Trendelenburg equation) Pickford-Nicolson anomaloscope settings were abnormal in 15 patients. Correlating each of the 20 spatiotemporal losses with the colour losses revealed that in 19 conditions the red/green loss was greater than the green/blue loss. None of the green/blue losses correlated significantly with spatiotemporal losses while between 2 and 8 cycles/deg 11/12 spatiotemporal conditions showed significant correlations with red/green colour loss. These results support a locus of damage before the cortex at a stage in the visual pathway where red/green chromatic information may be encoded in pathways which also code luminance information.

Adult↗

PubMed1991

Assessment of cycloplegic effects on the vistech contrast sensitivity test in Army aviator candidates.

This study was designed to provide information regarding two aspects of contrast sensitivity testing of aviator candidates: first to determine whether contrast sensitivity functions (CSF's) obtained with the Vistech Visual Contrast Test System (VCTS) are affected by cycloplegia and second to determine whether the VCTS provides useful CSF's under clinical screening conditions in a timely and simple manner. Contrast sensitivity thresholds were obtained at 5 spatial frequencies from 106 aviator candidates before and after administering a cycloplegic. CSF's obtained under cycloplegia were reduced by about 20%. The VCTS provided useful CSF's under military screening conditions, and added about 6 min to the time required for the standard flight physical.

Adult↗

PubMed1992

Contrast sensitivity vision testing: new screening technology for family physicians.

Contrast sensitivity vision testing is the new technology in visual screening. Easy to administer and quick to perform, contrast sensitivity vision testing appears to be cost-effective for use by family physicians. It is a more sensitive indicator of ocular disease than traditional Snellen acuity testing and may detect ocular pathology at an early stage when Snellen acuity is still normal.

Adult↗

PubMed2006

Influence of pupil diameter on the relation between ocular higher-order aberration and contrast sensitivity after laser in situ keratomileusis.

PURPOSE: To investigate the influence of pupil diameter on the relation between induced changes in ocular higher-order wavefront aberrations and changes in contrast sensitivity by conventional laser in situ keratomileusis (LASIK) for myopia. METHODS: In 215 eyes of 117 patients (age, 33.2 +/- 8.3 years) undergoing LASIK for myopia of -1.25 to -13.5 D (-5.28 +/- 2.55 D), ocular wavefront aberrations and contrast sensitivity function were determined before and 1 month after surgery. Preoperative photopic pupil diameter was measured with a digital camera. Ocular higher-order aberrations were measured for a 4-mm pupil with a Hartmann-Shack wavefront analyzer. The root-mean-square (RMS) of the third- and fourth-order Zernike coefficients was used to represent coma- and spherical-like aberration, respectively. From the contrast-sensitivity data, the area under the log contrast sensitivity function (AULCSF) was calculated. RESULTS: One hundred five eyes had a photopic pupil diameter of 4 mm or larger, and the remaining 110 had a photopic pupil diameter smaller than 4 mm. There were no statistically significant differences in the background clinical data between these two groups. In the eyes with a photopic pupil diameter of 4 mm or larger, the changes in third-order comalike aberrations did not correlate with the changes in AULCSF (Pearson correlation coefficient, r = -0.037, P = 0.723) and 10% low-contrast visual acuity (r = 0.125, P = 0.224), but fourth-order spherical-like aberrations correlated significantly with the changes in AULCSF (r = -0.229, P = 0.024) and 10% low-contrast visual acuity (r = 0.221, P = 0.038). In the eyes with photopic pupil size smaller than 4 mm, there were significant correlations between the changes in comalike aberrations and the changes in AULCSF (r = -0.487, P < 0.001) and 10% low-contrast visual acuity (r = 0.310, P = 0.003), but spherical-like aberrations showed no correlation with the changes in AULCSF (r = -0.078, P = 0.485) and 10% low-contrast visual acuity (r = 0.208, P = 0.158). CONCLUSIONS: In eyes with larger photopic pupil diameter, increases in spherical-like aberration dominantly affect contrast sensitivity, whereas in eyes with smaller pupil size, changes in coma-like aberration exert greater influence on visual performance.

Adolescent↗

PubMed2000

Measuring contrast sensitivity in patients with Graves' ophthalmopathy complicated by ocular hypertension and suspect glaucoma or dysthyroid optic neuropathy.

The present study compares contrast sensitivity functions of patients with uncomplicated Graves' ophthalmopathy, patients with ophthalmopathy and elevated intraocular pressure or suspect glaucoma, and patients with dysthyroid optic neuropathy (DON). Aim of the study was to investigate the clinical potential for the contrast sensitivity functions (CSF) in distinguish between the groups. Contrast sensitivity measurements were obtained from twenty-seven subjects with endocrine ophthalmopathy. Group I included patients with uncomplicated ophthalmopathy (n=20 eyes); group II included patients with ophthalmopathy, intraocular pressure > or = 24 mmHg with and without early visual field defects, and no evidence of apical crowding on coronal computed tomography scan (n=14 eyes); group III included patients with DON (n=12 eyes). Contrast thresholds were determined for stationary and 6.87 Hz phase-alternating gratings at eight spatial frequencies from 0.18 to 15.7 c/deg. Data from each group was compared with data from age-matched normal subjects. Observers with uncomplicated ophthalmopathy had normal CSFs. Eyes affected with DON showed contrast sensitivity disruption at overall intermediate-high spatial frequencies. Eyes with elevated intraocular pressure or suspect glaucoma had pronounced sensitivity loss in the low frequency range (0.18-0.70 c/deg) as compared to eyes with DON. This study shows that CSF detects visual function abnormalities noninvasively in patients with complicated Graves' ophthalmopathy. Results also indicate that the clinical potential for CSF in distinguish between patients suffering from ophthalmopathy complicated by ocular hypertension or suspect glaucoma and patients with DON improves when a temporal modulation of 6.87 Hz and gratings of low spatial frequency (< 1 c/deg) are used.

Adult↗