Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Contrast Sensitivity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed2006

Improved contrast sensitivity and visual acuity after wavefront-guided laser in situ keratomileusis: in-depth statistical analysis.

PURPOSE: To evaluate changes in contrast sensitivity and visual acuity following wavefront-guided laser in situ keratomileusis (LASIK) procedures with the Visx CustomVue system. SETTING: Six clinical sites that participated in an Investigational Device Exemption clinical study. METHODS: Two hundred seventy-four myopic astigmatic eyes (spherical equivalent range -0.63 to -6.00 diopters) completed 6 months of follow-up examinations. Wavefront-guided procedures using the WaveScan aberrometer and Star S4 excimer laser system with variable spot scanning were performed at 6 clinical locations. Visual acuity and contrast sensitivity under photopic, mesopic, and mesopic-with-glare lighting conditions were tested preoperatively and over a 6-month follow-up period. This study was a retrospective analysis of contrast sensitivity data with controls for the effects of retinal magnification, mesopic pupil size, and the influence of prior soft contact lens wear on visual outcome. RESULTS: Patients experienced statistically significant improvements in contrast sensitivity at all spatial frequencies and under all lighting conditions (P<.05, Student t test). Contrast sensitivity under mesopic conditions with glare improved in 40% of patients. There was more improvement at higher (12 cycles per degree [cpd], 18 cpd) than lower (3 cpd) spatial frequencies. No correlation was found between mesopic pupil size and contrast sensitivity. Results stratified by spectacle or soft contact lens wear were similar. Soft contact lens wearers had slightly higher disability glare scores than spectacle wearers. CONCLUSIONS: A significant number of patients experienced improved corneal optical quality after wavefront-guided LASIK. The contrast sensitivity in most patients was unchanged. Contrast sensitivity improved in a significant number of patients. There was no correlation between mesopic pupil size and mesopic or mesopic-with-glare contrast performance. Spectacle wearers improved more than soft contact lens wearers.

Adult↗
PubMed1998

[The Pelli-Robson contrast sensitivity test].

The author gives the first information on the practical experiences with the new examining method finding out the sensitiveness to contrast according to Pelli-Robson at ophthalmology department in Trnava. This examining method allows to gain more complex and quality information about sight quality. It makes possible to reify the lower sight quality in cases of normal values of central visual acuity examined by a classic method, e.g. by means of Snellen optotypes. The examination is more and more used at some chosen professions, those requiring work under difficult light conditions, such as drivers, pilots, engine-drivers etc. The examination can quicker help to discover endangered eye diseases.

Contrast Sensitivity↗
PubMed1997

Contrast sensitivity loss is coupled with capillary dropout in patients with diabetes.

PURPOSE: To assess the relationship of foveal microcirculation to contrast sensitivity function in early diabetes mellitus. METHODS: Twenty patients with diabetes with visual acuity of 20/25 or better without clinically significant macular edema were evaluated. Measurements of contrast sensitivity at four spatial frequencies (3, 6, 12, and 18 cycles/degree [c/deg]), macular capillary blood velocity (CBV), capillary density (PIA: perifoveal intercapillary area), foveal avascular zone (FAZ), and microaneurysm count were performed. Contrast sensitivity data collected from age-matched normal subjects and previously published normal angiographic data were used for comparison with our cohort with diabetes. RESULTS: The CBV was significantly reduced (P < 0.0001) and PIA and FAZ were significantly enlarged (P < 0.0001) when compared with healthy subjects. Contrast sensitivity was significantly lower in the group with diabetes at 6 (P = 0.01) and 12 (P = 0.002) c/deg as compared with healthy control values. FAZ and PIA correlated significantly (FAZ; r = -0.60, P = 0.005; PIA; r = -0.54, P = 0.02) with contrast sensitivity at 12 c/deg. CONCLUSIONS: The alterations of the perifoveal network are related to selective disturbances of central visual function as measured by contrast sensitivity. In patients with diabetes measurement of contrast sensitivity may provide a clinical adjunct in further identifying early ischemic diabetic maculopathy.

Adult↗
PubMed1999

Modelling spatial contrast sensitivity functions for chromatic and luminance-modulated gratings.

We extended our detection model of achromatic spatial vision (Rovamo, J., Mustonen, J., & Näsänen, R. (1994a). Modelling contrast sensitivity as a function of retinal illuminance and grating area. Vision Research, 34, 1301-1314) to colour vision by taking into account the fact that due to the spatio-chromatic opponency of retinal ganglion cells and dorsal lateral geniculate nucleus (dLGN) neurons, equiluminous chromatic gratings are not affected by precortical lateral inhibition. We then tested the extended model by using Mullen's experimental data (Mullen, K. J. (1985). The contrast sensitivity of human color vision to red-green and blue-yellow chromatic gratings. Journal of Physiology, 359, 381-400). The band-pass shape of the spatial contrast sensitivity function for luminance-modulated green and yellow gratings transformed to a low-pass shape, resembling the chromatic spatial contrast sensitivity function for red-green and blue-yellow equiluminous gratings, when the effect of precortical lateral inhibition on grating contrast was computationally removed by dividing luminance contrast sensitivities by spatial frequency (i.e. by af, where a = 1 degree). After the removal of this direct effect of lateral inhibition, there still remained a residual shape difference between the spatial contrast sensitivity functions for chromatic and luminance gratings. It was due to indirect reduction of grating visibility by quantal noise high-pass filtered by precortical lateral inhibition. When this indirect effect of quantal noise was also removed, contrast sensitivity for luminance gratings was about twice the sensitivity for chromatic gratings at all spatial frequencies. This was evidently due to the fact that the chromatic contrast of the equiluminous grating at the opponent stage (Cole, G. R., Hine, T. & McIihagga, W. (1993). Detection mechanisms in L-, M-, and S-cone contrast space. Journal of the Optical Society of America A, 10, 38-51) was about half of the luminance contrast of either of its chromatic component. Thus, if the contrast of the equiluminous chromatic grating were not expressed as the Michelson contrast of one chromatic component grating against its own background (Mullen, K. J. (1985). The contrast sensitivity of human color vision to red-green and blue-yellow chromatic gratings. Journal of Physiology, 359, 381-400) but as chromatic contrast at the opponent stage, contrast sensitivity would be the same for chromatic and luminance gratings.

Color Perception↗
PubMed2005

[Contrast sensitivity and stereopsis in pseudophakic patients with multifocal intraocular lens].

PURPOSE: To evaluate the contrast sensitivity and stereopsis tests in patients who underwent bilateral implantation of multifocal intraocular lens. METHODS: Tests of contrast sensitivity using the Pelli-Robson chart and stereopsis evaluation with the Titmus Stereo Test were performed in 20 patients 30-60 days after the bilateral implantation of Acrysof Restor multifocal intraocular lens. RESULTS: The binocular contrast sensitivity test demonstrated that 6 patients (30%) presented 1.80 log units, 13 (65%) 1.65 and in only 1 (5%) the sensitivity was 1.50 log units. By the other hand, the monocular test in right eye showed 17 patients (85%) with 1.65 log units and 3 (15%) with 1.50. In the left eye, the test presented 16 patients (80%) with 1.65 log units and 4 (20%) with 1.50 log units. The average and the standard deviation of the contrast sensitivity were 1.63 (+/-0.05) for right eye, 1.62 (+/-0.06) for left eye and 1.69 (+/-0.08) for binocular test. Stereopsis test disclosed 12 patients (60%) presenting 40", 6 (30%) 50" and only 2 (10%) 60" (average: 45" and standard deviation: 6.88"). CONCLUSIONS: The Acrysof Restor intraocular lens provided results of contrast sensitivity and stereopsis in accordance with the criteria of normality established previously in other studies for phakic and pseudophakic patients. Therefore, this intraocular lens does not decrease visual functionality.

Aged↗
PubMed1997

Contrast sensitivity in infants and children with Down syndrome.

A new contrast sensitivity (CS) card test was used to estimate contrast sensitivity in 18 infants and children with Down syndrome (DS). The results showed that although the overall shape of the contrast sensitivity functions (CSFs) of the subjects with DS was the typical inverted-U, their CSFs were depressed in comparison to control subjects and this relative loss became larger with increasing spatial frequency. In addition, there was little improvement in CS with age and the mean CSF among children with DS (mean age = 7.3 years) was equivalent statistically to a group of 12-month-olds without DS. The Teller Acuity Cards (TAC) were also used to assess visual acuity in 17 of the 18 children in our sample. The results of these tests showed that their visual acuity (VA) was significantly lower than normal, but was consistent with that extrapolated from each subject's CSF. Taken together with previous anatomical and developmental findings, our results suggest that the deficits in spatial vision among children with DS is due primarily to restricted cortical development, and secondarily, to the additional accommodative and ocular conditions that are prevalent in this population.

Adolescent↗
PubMed2004

Spatio-temporal luminance contrast sensitivity and visual backward masking in schizophrenia.

The aim of two experiments was to investigate the relationship between spatio-temporal contrast sensitivity and visual backward masking in normal observers and in subgroups with positive or negative symptoms in schizophrenia. Experiment 1 measured contrast sensitivity for stationary and counterphase-modulated sinusoidal gratings at four spatial (0.5, 2.0, 4.0, 8.0 cycles/degree) and four temporal frequencies (0, 4.0, 8.0, 16.0 Hz). The results showed that there were no differences in spatio-temporal contrast sensitivity between the control and positive-symptom group, and in comparison with these groups, contrast sensitivity was significantly lower at all spatial and temporal frequencies in the negative-symptom group. Experiment 2 measured the visibility of a Landolt C target with a constant target stimulus duration of 4.0 ms followed by a 150-ms backward mask, which was presented at 12 stimulus onset asynchronies from 0 to 110 ms in the same groups of observers. Consistent with the findings of the previous experiment, there were no significant differences in backward masking between the control and positive-symptom group, and in comparison with these groups, visual backward masking was significantly higher at all stimulus onset asynchronies from 40 to 110 ms in the negative-symptom group. The present findings show that there were no significant differences in contrast sensitivity and in backward masking between normal observers and a group with positive symptoms in schizophrenia. It was concluded that the reduction in contrast sensitivity for low spatial frequency counterphase flicker in the negative-symptom group is consistent with a reduction in the 'contrast gain control' mechanism of magnocellular channels, and that the reduction in contrast sensitivity for medium and high stationary gratings is consistent with a disorder in parvocellular channels. It was proposed that a disorder in magnocellular channels in the negative-symptom group may enforce a reliance on parvocellular channels that results in longer temporal summation and visible persistence, slower visual processing of single target stimuli at threshold and higher levels of sensory integration, and backward masking when multiple stimuli are presented rapidly in time.

Adult↗
PubMed1990

Objective measurement of contrast sensitivity using the steady-state visual evoked potential.

Contrast sensitivity functions (CSFs) were determined electrophysiologically with the steady-state visual evoked potential (VEP). Psychophysical CSFs obtained by the method of increasing contrasts were also measured concurrently with the VEP trials. The VEP contrast thresholds were obtained using a rapid recording technique in which the contrast of a counterphase sinewave modulated at a temporal frequency of 7.5 Hz was swept from 0.5% to 40% over a period of 22 s in 39 equal logarithmic steps. For this pattern reversal stimulus, the amplitude and phase of the second harmonic response as a function of contrast were measured using a discrete Fourier transform (DFT). Contrast sensitivities at five spatial frequencies ranging from 0.5 to 14.9 cpd were measured. The VEP contrast thresholds were determined by a linear extrapolation to zero amplitude. The contrast threshold obtained by the two methods correlated at 0.816 for 14 subjects. For all five spatial frequencies there were no significant differences between the contrast sensitivities derived from the two methods.

Adult↗
PubMed1993

Effects of target distance and pupil size on letter contrast sensitivity with simultaneous vision bifocal contact lenses.

Using simulated presbyopia we measured the effects of target vergence and pupil size on letter contrast sensitivity while subjects wore accurately centered simultaneous vision bifocal contact lenses. These experiments examined the increase in depth of focus provided by two bifocal contact lenses, and the effects of pupil size on near and distance vision. Monocular contrast sensitivity was assessed with three different designs of soft contact lenses. First, as a single vision control, we measured contrast sensitivity with a Bausch & Lomb, Optima 38 lens corrected for distance. We then measured contrast sensitivity with an Allergan Optical, Hydron Echelon, which is a diffractive simultaneous bifocal and a CIBA Vision, Spectrum, which is a concentric design, center-near, two-zone simultaneous vision bifocal. In general both bifocal contact lenses improved contrast sensitivity at near but decreased contrast sensitivity at distance (when compared to the single vision lens). With a fixed 3.5-mm artificial pupil, the Echelon lens had two clear peaks of sensitivity, one at distance (0.00 D) and one at near (-2.00 D), but the Spectrum lens had no clear peaks. Performance of the Spectrum lens depended on its center zone size. Near (-2.00 D) and distance (0.00 D) contrast sensitivity was measured with pupil sizes that ranged from 1 to 6 mm. The results showed that visual performance with a diffractive lens was almost independent of pupil diameter up to 3 to 4 mm but, as predicted, performance with the two-zone lens depended critically on pupil size.

Contact Lenses, Hydrophilic↗
PubMed1997

Development of temporal contrast sensitivity in human infants.

The time course for the development of the temporal contrast sensitivity function in humans is uncertain. Some studies indicate that temporal contrast sensitivity is immature in infants. However, earlier work suggests that critical flicker fusion is adult-like by 2 months. We traced the development of temporal contrast sensitivity to uniform field flicker in 2-, 3- and 4-month-old infants using a modified preferential-looking technique that employed a rating scale. Two-month-old infants exhibited highest sensitivities at 1 and 2 Hz. Three- and 4-month infants exhibited peak sensitivity at 4 and 8 Hz, respectively. Overall temporal contrast sensitivity increased with age and the peak frequency shifted toward higher temporal frequencies. Using this paradigm, no infant subjects showed responses to 32 Hz, the highest temporal frequencies tested.

Age Factors↗
PubMed1991

Visual acuity and contrast sensitivity in relation to falls in an elderly population.

Visual acuity and contrast sensitivity were measured in 95 residents of a hostel for the aged (mean age = 83 years) using a dual-contrast letter chart and the Melbourne Edge Test (MET). Vision (as measured by visual acuity, the MET, low-contrast visual acuity, and difference between high- and low-contrast acuity) decreased significantly with age and all four measures were significantly correlated. Subjects with a clinical eye disorder had poorer vision than those without a disorder although the differences were not significant. Visual acuity and contrast sensitivity were not associated with body sway when subjects were standing on a firm base. However, when the subjects were placed in a situation which provided reduced support (standing on a compliant surface), body sway was associated with poor visual acuity and contrast sensitivity. There was also a difference in contrast sensitivity between those who fell one or more times in a year of follow-up and those who did not fall. It appears that reduced vision may be a predisposing factor to postural imbalance and falls in elderly persons.

Accidental Falls↗
PubMed2002

The dependence of binocular contrast sensitivities on binocular single vision in normal and amblyopic human subjects.

We have measured monocular and binocular contrast sensitivities in response to medium to high spatial frequencies of vertical sinusoidal grating patterns in normal subjects, anisometropic amblyopes, strabismic amblyopes and non-amblyopic esotropes. On binocular viewing, contrast sensitivities were slightly but significantly increased in normal subjects, markedly increased in anisometropes and esotropes with anomalous binocular single vision (BSV) and significantly reduced in esotropes and exotropes without BSV. Application of a prismatic correction to the strabismic eye in order to achieve bifoveal stimulation resulted in a significant reduction in contrast sensitivity in esotropes with and without anomalous BSV, in exotropes and in non-amblyopic esotropes. Control experiments in normal subjects with monocular viewing showed that degradative effects of the prism occurred only with high prism powers and at high spatial frequencies, thus establishing that the reduced contrast sensitivities were the consequence of bifoveal stimulation rather than optical degradation. Displacement of the image of the grating pattern by 2 deg. in normal subjects and anisometropes by a dichoptic method to simulate a small angle esotropia had no effect on the contrast sensitivities recorded through the companion eye. By contrast, esotropes showed similar reductions in contrast sensitivity to those obtained with the prism experiments, confirming a fundamental difference between subjects with normal and abnormal ocular alignments. The results have thus established a suppressive action of the fovea of the amblyopic eye acting on the companion, non-amblyopic eye and indicate that correction of ocular misalignments in adult esotropes may be disadvantageous to binocular visual performance.

Accommodation, Ocular↗
PubMed1996

Characterization of spatial aliasing and contrast sensitivity in peripheral vision.

Psychometric performance was measured for contrast detection and spatial resolution tasks in foveal and peripheral vision. Objective evidence was obtained for a quantitative difference between resolution acuity and detection acuity in the peripheral field. These two types of spatial acuity differed by up to an order of magnitude (3 vs 30 c/deg at 30 deg eccentricity) and they varied with stimulus contrast in distinctly different ways. Contrast sensitivity at the resolution limit was an order of magnitude above the absolute threshold of unity and the shape of the contrast sensitivity function was significantly different from that measured for foveal vision. The results suggest that current models of eccentricity scaling of contrast sensitivity be re-evaluated to take account of the extensive aliasing zone of spatial frequencies which becomes functional in peripheral vision when the retinal image is well focused.

Contrast Sensitivity↗
PubMed2004

Ocular higher-order aberrations and contrast sensitivity after conventional laser in situ keratomileusis.

PURPOSE: To investigate prospectively the relation between induced changes in higher-order aberrations of the eye and changes in contrast sensitivity by conventional laser in situ keratomileusis (LASIK) for myopia. METHODS: In 200 eyes of 110 consecutive patients (mean age, 32.7 +/- 8.4 years) undergoing LASIK, ocular aberrations and contrast sensitivity function were determined before and 1 month after surgery. The amount of myopic correction was 5.2 +/- 2.8 D (range, 1.0-13.0). Ocular higher-order aberrations were measured for a 4-mm pupil using the Hartmann-Shack wavefront analyzer (KR-9000PW; Topcon, Tokyo, Japan). The root mean square (RMS) of the third- and fourth-order Zernike coefficients was used to represent coma- and spherical-like aberrations, respectively. Total higher-order aberrations were calculated as the RMS of the third- and fourth-order coefficients. Contrast sensitivity and low-contrast visual acuity were measured. From the contrast sensitivity data, the area under the log contrast sensitivity function (AULCSF) was calculated. RESULTS: LASIK significantly improved logMAR best corrected visual acuity (Wilcoxon signed-rank test, P <0.001), but significantly reduced AULCSF (P <0.001) and low-contrast visual acuity (P=0.007). Total higher-order (P <0.001), coma-like (P <0.001), and spherical-like (P <0.001) aberrations were significantly increased after LASIK. The greater the amount of achieved myopia correction was, the more the changes in contrast sensitivity function and ocular higher-order aberrations were. The induced changes in AULCSF by LASIK showed significant correlations with changes in total higher-order (Pearson r=-0.221, P=0.003), coma-like (r=-0.205, P=0.006), and spherical-like (r=-0.171, P=0.022) aberrations. The changes in logMAR low-contrast visual acuity by surgery significantly correlated with changes in total higher-order (r=0.222, P=0.003), coma-like (r=0.201, P=0.007), and spherical-like (r=0.207, P=0.005) aberrations. CONCLUSIONS: Conventional LASIK significantly increases ocular higher-order aberrations, which compromise the postoperative contrast sensitivity function.

Adolescent↗
PubMedDate not supplied

Luminance and color contrast sensitivity and VEP latency in subjects with normal and defective binocularity.

Luminance contrast sinusoidal gratings (spatial frequencies 1, 2 and 4 cycles/degree) were compared with the corresponding color contrasting patterns (along the protan, deutan and tritan axes) to see whether they demonstrated normal binocular function in humans, and distinguished between normals and persons with defective binocularity. Contrast sensitivity and transient pattern VEP latency (on-responses) were measured in normals (n = 11, median age 36, range 12-46 years) and subjects with no stereopsis (n = 6, median age 13, range 8-38 years). The normal group had significantly higher contrast sensitivity with binocular stimulation for all patterns except tritan contrast gratings of 2 and 4 c/deg. The stereo-deficient group showed no higher binocular contrast sensitivity for any pattern. Differences between groups were significant with all gratings of 4 c/deg, and also with protan and deutan contrast gratings of 2 c/deg. In the normal group, binocular VEP latency was significantly shorter than the monocular with protan contrast gratings of 2 c/deg and tritan contrast gratings of 1 and 2 c/deg. Differences between the normal and the stereo-deficient groups were significant for all color contrast patterns of 2 c/deg; and tritan contrast gratings of 1 c/deg. We conclude that color contrast sensitivity and VEP measurements are potentially useful for demonstrating binocular function, and for separating normals from stereo-blind subjects. Color contrast patterns however are less effective than the corresponding luminance contrast patterns in evoking cortical potentials.

Adolescent↗
PubMed1989

Contrast sensitivity for letter and grating targets under various stimulus conditions.

Measurement of visual acuity for letters of different contrasts has been suggested as a clinical way to evaluate contrast sensitivity in patients with vision abnormalities. If variable-contrast letter acuity provides information similar to the contrast sensitivity function (CSF), then comparable effects should be seen in stimulus manipulations which simulate decreased vision. Using both our own and published data, we compared the effects of diffusive blur, dioptric blur, and eccentric viewing on contrast sensitivity for letter and grating targets. A diffuser placed close to the eye reduces contrast sensitivity fairly evenly across all spatial frequencies, with similar results for letters and gratings. However, dioptric blur reduces sensitivity substantially more to letters than to comparably fine gratings. Eccentric viewing also produces a larger sensitivity loss for letters than for gratings. Because some stimulus manipulations produce dissimilar changes in contrast sensitivity for letters and gratings, it is questionable whether the results of one measure can be used to draw inferences about the other. It is proposed that local or relative phase discrimination has an important role in explaining the different responses to letter and grating targets.

Adult↗
PubMed1987

Flicker contrast sensitivity in normal and specifically disabled readers.

Temporal contrast sensitivity for counterphase flicker was determined for specifically disabled and normal readers to investigate whether the two groups differ in the functioning of their transient systems. In experiment 1, temporal contrast sensitivity was measured over a range of temporal frequencies with a spatial frequency of 2 cycles deg-1. Disabled readers were less sensitive than the control subjects at all temporal frequencies. In experiment 2, temporal contrast sensitivity was measured at a temporal frequency of 20 Hz over a range of spatial frequencies. Disabled readers were less sensitive than the controls at all spatial frequencies, with the differences between the groups increasing as spatial frequency increased. Both these findings are interpreted as supporting the hypothesis of a transient-system deficit in the visual systems of disabled readers.

Adolescent↗
PubMed1998

Contrast sensitivity and glare disability after radial keratotomy and photorefractive keratectomy.

OBJECTIVES: To study the effects of radial keratotomy (RK) and photorefractive keratectomy (PRK) on contrast sensitivity and glare disability using 4 different devices, and to correlate subjective complaints with obj ective scores of visual performance. METHODS: Preoperative contrast sensitivity for 30 eyes undergoing RK and 30 eyes undergoing PRK was compared with contrast sensitivity at 1, 3, and 6 months postoperatively using the CSV 1000, MCT (Multivision Contrast Tester) 8000, and Pelli-Robson chart. The BAT (Brightness Acuity Tester) and MCT 8000 were used to test for daytime and nighttime glare disability, respectively. At 3 and 6 months postoperatively, a questionnaire was administered to assess visual performance subjectively. RESULTS: Contrast sensitivity decreased after RK and PRK up to the sixth postoperative month, while glare disability was significantly increased at 1 month after PRK as determined by the MCT 8000 and the BAT, and at the third and sixth months after RK using the MCT 8000. Compared with RK, PRK significantly decreased contrast sensitivity as measured with the MCT 8000 at all spatial frequencies 1 month postoperatively. No significant difference in visual performance between patients undergoing RK and PRK was observed with the CSV 1000, the Pelli-Robson chart, or the BAT up to 6 months postoperatively. No consistent difference was found between glare disability scores of patients undergoing RK and PRK when measured with the MCT 8000. Subjective reports of problems with night driving and blurring correlated only with glare disability scores of the MCT 8000 3 months after RK. CONCLUSIONS: Both RK and PRK reduce contrast sensitivity and cause glare disability; however, the relative effect is highly dependent on the time postoperative testing is performed and the instrument used for testing. Contrast sensitivity and glare disability, as measured by the instruments used in this study, do not accurately reflect patients' subjective assessment of visual performance in daily life.

Adult↗