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PubMed1989

Visual contrast sensitivity in drug-induced Parkinsonism.

The influence of stimulus orientation on contrast sensitivity function was studied in 10 patients with drug-induced Parkinsonism. Nine of the 10 patients had at least one eye with contrast sensitivity deficit for vertical and/or horizontal stimuli. Only generalised contrast sensitivity loss, observed in two eyes, was stimulus orientation independent. All spatial frequency-selective contrast deficits in 15 eyes were orientation dependent. The striking similarity between the pattern of contrast sensitivity loss in drug-induced Parkinsonism and that in idiopathic Parkinson's disease, suggests that generalised dopaminergic deficiency, from whatever cause, affects visual function in an analogous way.

Adolescent↗
PubMed1987

Contrast sensitivity: characteristics of a large, young, adult population.

Contrast sensitivity functions and complete eye examinations were obtained from 103 normal, healthy young adults (ages 21 to 40 years). Descriptive statistics were compiled for the group in order to provide normative information. Subsets of the population were evaluated with respect to the relations among the attributes of accommodation, visual acuity, refraction, spectacle wear, and contrast sensitivity. The influence of age in this restricted population was seen only at 16 cpd. In those subjects with better than 6/6 (20/20) Snellen acuity, there were statistically significant relations with the parameters of the contrast sensitivity function as compared to those observers with 6/6 (20/20) or poorer acuity. High spatial frequency resolution was significantly better for those observers with better than 6/6 (20/20) acuity in either eye. In addition, this study provides a broad base of normative data for variability from a large population confined to a specific age range and with refractive errors that ranged from minimal to more than average.

Adult↗
PubMed2004

Contrast sensitivity and color vision with a yellow intraocular len.

OBJECTIVE: To evaluate contrast sensitivity and color vision of yellow ultraviolet (UV) intraocular len (IOL) in cataract patients. DESIGN: Randomized clinical trial. METHODS: Extracapsular cataract extraction was performed in 60 senile cataract patients. The patients were randomly assigned to receive 30 yellow UV IOLs and 30 ordinary UV IOLs. Visual acuity, contrast sensitivity, and color vision were examined up to 6 months postoperatively. RESULTS: The yellow UV IOLs showed statistically significantly higher spatial contrast sensitivity than ordinary UV IOLs in the low and middle frequencies. There was no significant difference between yellow and ordinary UV IOL in color vision. Incidences of photophobia and cyanopsia were less in patients who received the yellow UV IOLs. CONCLUSIONS: Yellow UV IOLs are preferable to ordinary UV IOLs in preserving spatial contrast sensitivity and cause less photophobia and cyanopsia in the early postoperative period.

Aged↗
PubMed1989

Global spatiochromatic mechanism accounting for luminance variations in contrast sensitivity functions.

Psychophysical luminance and chromatic spatial contrast sensitivity functions (CSF's) exhibit a number of variations that depend on the average luminance of the stimulus grating. The contrast sensitivity at each spatial frequency and the maximum resolvable spatial frequency decrease with decreasing average luminance. Most prominently, luminance CSF's have peaks that shift toward lower frequencies, broaden, and disappear as luminance decreases. Chromatic CSF's are flat at low frequencies and do not exhibit luminance-related variations in shape. In this paper, we account for the luminance-dependent variations of CSF's by incorporating them into an earlier model that accounts for the basic high-luminance shapes of psychophysical luminance and chromatic spatial CSF's. These variations are modeled by increasing the spatial extent of a global center mechanism while decreasing the inhibitory effect of a global surround on that center. The results support the hypothesis that the global center mechanism changes size as a means of maintaining the dynamic range and controlling the signal-to-noise ratio as luminance varies.

Biomechanical Phenomena↗
PubMed1986

Changes in contrast sensitivity during the first hour of soft lens wear.

Changes in contrast sensitivity were monitored immediately before, during, and after 1 hour's soft lens wear. Soft lenses of three different center thicknesses, 0.03, 0.07, and 0.12 mm, were used. Results demonstrated a gradual reduction in contrast sensitivity during wear, with a faster but not instantaneous recovery after removal. An increase in soft lens center thickness caused a more pronounced loss of contrast sensitivity, with a slower recovery. The implications of this research on the various reasons put forward for the impairment of the contrast sensitivity function by soft lenses are discussed.

Contact Lenses, Hydrophilic↗
PubMed2005

Repeated measurements of contrast sensitivity reveal limits to visual plasticity after early binocular deprivation in humans.

Contrast sensitivity improves in visually normal children until 7 years of age and is impaired in children who experienced early visual deprivation from bilateral congenital cataracts. Here, we investigated whether the deficits after early visual deprivation change during childhood by retesting the contrast sensitivity of seven patients treated for bilateral congenital cataract who had been first tested before 7.5 years of age, and of two patients first tested after 11 years of age. For the younger group, contrast sensitivity at low spatial frequencies improved after 1- and 2-year intervals, while their sensitivity at mid and high spatial frequencies did not change. There was no systematic change in the two older patients. The results indicate that early visual input sets up the neural substrate for later improvement in contrast sensitivity at mid and high spatial frequencies. However, there is sufficient plasticity during middle childhood to allow some recovery at low spatial frequencies. The results shed new light on the role of early visual experience and the nature of developmental plasticity.

Cataract↗
PubMed1975

Contrast sensitivity in meridional amblyopia.

Contrast (modulation) sensitivities for gratings of various spatial frequencies and orientations have been determined for meridional amblyopes. The entire contrast sensitivity function is reduced for gratings oriented in the amblyopic meridian. Therefore, neural elements that process a broad range of spatial frequencies are affected by meridional amblyopia.

Amblyopia↗
PubMed1988

Contrast sensitivity in patients with posterior chamber intraocular lens implants.

Divergent contrast sensitivity findings have been reported in patients with intraocular lens implants. In this study, contrast sensitivity to stationary sine-wave gratings of six spatial frequencies from 0.5 to 22.8 cycles/degree was measured psychophysically in 13 patients with posterior chamber intraocular lens implants and in 10 controls. Corrected visual acuity was 0.7 to 1.0 in the intraocular lens group and 0.9 to 1.0 in the reference group. The age, the pupil diameter and the rate of subtle age-related macular changes were equal in the two groups. No statistically significant difference in mean contrast sensitivity between the patients and the controls was observed at any spatial frequency examined.

Age Factors↗
PubMed1985

The effect of vertical differential prism on the binocular contrast sensitivity function.

The binocular contrast sensitivity function is measured using horizontal sinusoidal gratings with base-down prism before the right eye. In photopic conditions one prism-dioptre causes a significant drop in sensitivity at all spatial frequencies and in mesopic conditions as little as a half prism-dioptre has a similar effect. The implications for a physiological tolerance for unintended vertical differential prism in spectacles are discussed.

Adaptation, Ocular↗
PubMed2006

Contrast sensitivity and color vision in HIV-infected individuals without infectious retinopathy.

PURPOSE: To investigate the relationship between abnormal contrast sensitivity and abnormal color vision among human immunodeficiency virus (HIV)-infected individuals who have normal visual acuity and to seek host factors that predict these abnormalities. DESIGN: Noninterventional, cross-sectional study. METHODS: We evaluated 71 HIV-infected subjects with visual acuity of 20/25 or better, clear media, and no vision-threatening retinal lesions. Visual function was determined using the Pelli-Robson contrast sensitivity test and the Farnsworth-Munsell 100-Hue color test (FM-100). Results were compared with published values for normal populations and to measures of HIV disease severity. We evaluated two levels of impairment for each visual function. "Mild dysfunction" was defined as > or =1 standard deviation (SD), but <2 SD from normal means. "Abnormal" was defined as > or =2 SD from normal means. RESULTS: The prevalences of abnormal contrast sensitivity and abnormal color vision were 7.0% and 9.9%, respectively. We did not identify relationships between impaired contrast sensitivity and impaired color vision. Impaired color vision was associated with increasing age (r = 0.36, P = .002). We could not identify significant correlations between either contrast sensitivity or color vision values and the following factors: current or nadir (lowest previous) CD4+ T-lymphocyte count, HIV blood level, and Karnofsky score. CONCLUSIONS: Abnormal contrast sensitivity and abnormal color vision can occur independently in HIV-infected individuals and can be present in the absence of severe immunosuppression.

Adult↗
PubMed1984

Central and peripheral contrast sensitivity in amblyopia with varying field size.

The purpose of the present study was to establish the extent of the amblyopic deficit at 0 degree, 10 degrees, and 20 degrees retinal eccentricity using contrast sensitivity measures for sine wave gratings subtending various field sizes. Contrast sensitivity functions were shown to vary with stimulus field size, retinal location and degree of amblyopia. Foveally, peak contrast sensitivity of amblyopic eyes increased markedly with increasing field size, to reach the same magnitude as that of the contralateral non-amblyopic eyes for large fields. Peripherally, peak contrast sensitivity remained lower in the amblyopic eyes for all field sizes examined. High spatial frequency cut-offs were reduced both centrally and peripherally with all field sizes in the amblyopic eyes. The effect of increasing field size on the cut-off acuity was found to be smaller than the effect on peak contrast sensitivity. The most significant conclusions drawn from the results are that: (1) The amblyopic deficit in terms of both peak contrast sensitivity and acuity is not restricted to the central foveal region; and (2) amblyopic eyes benefit to a greater extent from increased stimulus field size than non-amblyopic eyes in terms of peak contrast sensitivity. A model is proposed which suggests that the results obtained are due to fewer and/or less sensitive cortical neurons being driven by the amblyopic eye in humans with naturally occurring amblyopia.

Adult↗
PubMed2005

[The influrence of visual acuity and contrast sensitivity on subjective evaluation of visual function before and after cataract surgery].

PURPOSE: To assess the influence of visual acuity and contrast sensitivity on subjective evaluation of visual function investigated by means of questionnaires in patients before and after cataract surgery. METHODS: Visual acuity was tested on Snellen projection optotypes and logMAR optotype chart with Landolt rings, contrast sensitivity was tested on Pelli-Robson chart. The questionnaire included Visual Functioning Index VF-14, Cataract Symptom Score and Global Measures of Vision--self-reported trouble and satisfaction with vision. 37 cataract patients were examined, including completing the questionnaire, 1 day before and 7 weeks after the surgery. RESULTS: Most patients (65%) suffer from moderate troubles with their vision and are moderately dissatisfied (51%) before cataract surgery. After the surgery, a majority of patients have no troubles (51%) and are very satisfied (54%). Visual acuity (VA) correlates only with VF-14, namely only VA of non-operated eye (p < 0.01), binocular VA before (p < 0.001) and after surgery (p < 0.05). Contrast sensitivity (of non-operated eye, operated eye, binocular) correlates with more subjective parameters (VF-14, self-reported trouble and satisfaction with vision), namely both before and after the surgery (p < 0.05, p < 0.01, p < 0.001). CONCLUSION: After cataract surgery, visual acuity, contrast sensitivity and subjective parameters of visual functions significantly improve. Subjective parameters correlate more with contrast sensitivity then with visual acuity. Contrast sensitivity is more related than visual acuity to real world in patients with cataract.

Aged↗
PubMed2005

[Contrast sensitivity to intraocular lens TECNIS Z-9000].

PURPOSE: To evaluate the increase in contrast sensitivity to intraocular lens TECNIS Z-9000 (Pfizer) compared with other intraocular lenses. METHOD: We implanted a TECNIS Z-9000 lens in 18 patients who had another type of intraocular lens implanted in their other eye. We then tested contrast sensitivity under both mesopic and photopic conditions using the VCTS (Vision Contrast Test System) provided by Vistech Consultants Inc. RESULTS: There was an improved contrast sensitivity at low and medium frequencies, following TECNIS-Z 9000 lens implantation, however this improvement did not reach statistical significance. There were significant differences at high frequencies, which are directly related to the quality of visual function. CONCLUSIONS: TECNIS Z-9000 lens implantation (with a modified anterior surface) achieves a significant improvement in contrast sensitivity, meaning in practice an increase in the quality of visual function.

Contrast Sensitivity↗
PubMed1997

Glare disability and contrast sensitivity before and after cataract surgery.

PURPOSE: To determine whether brightness-induced glare decreases spatial contrast sensitivity and visual acuity in preoperative cataract patients with functional visual complaints and to compare preoperative with postoperative results. SETTING: Sir Mortimer B. Davis Jewish General Hospital, Montreal, Quebec, Canada. METHODS: Twenty patients with a visual acuity of 20/70 or better at the time of chart selection and no other ocular pathology who were referred for cataract surgery were evaluated with the Optec 3000 vision tester to assess contrast sensitivity and visual acuity in the presence and absence of glare. Testing was done preoperatively and 1 and 3 months postoperatively. RESULTS: An analysis of variance indicated that there were statistically significant double interactions between the preoperative/postoperative and glare/no-glare variables and between the preoperative/postoperative and spatial frequency variables. Postoperatively, visual acuity and contrast sensitivity improved to within normal limits. There were no statistically significant differences in visual acuity and spatial contrast sensitivity between 1 and 3 months postoperatively. CONCLUSION: Spatial contrast sensitivity and glare testing provided objective assessment of patients who had good visual acuity yet also had functional complaints.

Adult↗
PubMed2005

Contrast sensitivity function of sound eye after occlusion therapy in the amblyopic children.

To verify the changes of mesopic and photopic contrast sensitivity function of sound eye whose visual acuity was kept the same after occlusion therapy in the amblyopic children. Fourteen sound eyes of amblyopic children (mean; 7.67 years; S.D., 1.50 years) who kept their visual acuity the same after the occlusion therapy were tested. The children had 6 hours of part-time patch therapy for 3 months prior to this examination. Among 14 amblyopic children, 8 were anisometric and 6 were strabismic amblyopes. Using the visual capacity analyzer which measures the minimal contrast level at from low to high spatial frequencies, the contrast sensitivity of sound eye was measured, under both photopic and mesopic condition, before and after 3 months of occlusion therapy. Comparing the contrast sensitivity of sound eye after the occlusion therapy to that before the occlusion, there was no statistical difference in photopic condition. When it comes to mesopic condition, the contrast sensitivity decreased at the intermediate spatial frequency level (3-13 c.p.d, p=0.028) after the occlusion therapy. The occlusion caused statistically significant decrease in mesopic contrast sensitivity, when the visual acuity was not changed after the occlusion therapy. It may indicate that mesopic contrast sensitivity can be considered as a useful tool for early detection of hidden occlusion amblyopia.

Amblyopia↗
PubMed1979

Visual resolution, contrast sensitivity, and the cortical magnification factor.

This study shows that photopic contrast sensitivity and resolution can be predicted by means of simple functions derived by using the cortical magnification factor M as a scale factor of mapping from the visual field into the striate cortex. We measured the minimum contrast required for discriminating the direction of movement or orientation of sinusoidal gratings, or for detecting them in central and peripheral vision. No qualitative differences were found between central and peripheral vision, and almost all quantitative differences observed could be removed by means of a size compensation derived from M. The results indicated specifically that (1) visual patterns can be made equally visible if they are scaled so that their calculated cortical representations become equivalent; (2) contrast sensitivity follows the same power function of the cortical area stimulated by a grating at any eccentricity; (3) area and squared spatial frequency are reciprocally related as determinants of contrast sensitivity; and (4) acuity and resolution are directly proportional to M, and the minimum angle of resolution is directly proportional to M-1. The power law of spatial summation expressed in (2) and (3) suggests the existence of a central integrator that pools the activity of cortical neurons. This summation mechanism makes the number of potentially activated visual cells the most important determinant of visibility and contrast sensitivity. The functional homogeneity of image processing across the visual field observed here agrees with the assumed anatomical and physiological uniformity of the visual cortex.

Brain Mapping↗
PubMed1996

Monocular contrast sensitivity in 3- to 36-month-old human infants.

A recently developed psychophysical "card" technique was used to evaluate monocular contrast sensitivity in ninety 3-, 6-, 12-, 24-, and 36-month-old human infants. Results showed that for 3-, 6-, 24-, and 36-month-olds, monocular contrast sensitivity functions were very similar to binocular contrast sensitivity functions estimated in a previous experiment. However, at 12-months, monocular contrast sensitivity functions were significantly lower (about 1 octave) than binocular contrast sensitivity functions, a trend also observed in developmental studies of visual acuity. This asymmetry suggests that the neural substrate underlying the development of monocular and binocular spatial vision undergoes different rates of development, at least during the months surrounding the end of the first postnatal year.

Aging↗