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PubMed1998

Visual acuity, contrast sensitivity and retinal magnification in a marsupial, the tammar wallaby (Macropus eugenii).

The visual acuity of the tammar wallaby was estimated using a behavioural discrimination task. The wallabies were trained to discriminate a high-contrast (86%) square-wave grating from a grey field of equal luminance (1000-6000 cd m-2). Visual-evoked cortical potentials were used to measure the complete contrast sensitivity function. The stimulus was a sinusoidal phase reversal of a sinusoidally modulated grating of various spatial frequencies and contrasts with a mean luminance of 40 cd m-2). The behavioural acuity was estimated to be about 4.8 cycles/deg. The contrast sensitivity peaked at about 0.15 cycles/deg and declined towards both lower and higher spatial frequencies. The cut-off frequency of the contrast sensitivity function is slightly lower than the behaviourally measured acuity at about 2.7 cycles/deg. The retinal magnification factor was estimated anatomically from laser lesions to be about 0.16 mm/deg. Based on the known ganglion cell density and the retinal magnification factor, an anatomical upper limit to visual acuity of about 6 cycles/deg can be calculated. The differences in estimates of visual acuity between the behavioural and anatomical methods on the one side and physiology on the other side are discussed.

Animals↗
PubMed1990

Optimum level of visual contrast sensitivity for reading comprehension.

Reading comprehension scores were curvilinearly related to a visual contrast sensitivity measure of 155 elementary school children. Moderate contrast sensitivity for fine detail appeared to be optimal for reading; both low and high sensitivity were associated with lower reading comprehension.

Attention↗
PubMed1983

Use of various measures of visual acuity and contrast sensitivity in the evaluation of monocular occlusion and active vision training of three adult amblyopes.

Three adult amblyopic patients who underwent vision training involving monocular occlusion of the nonamblyopic eye and stimulation of the amblyopic eye using simple fixation exercises and a spinning grating procedure were evaluated using five different types of acuity testing and two methods of contrast sensitivity. It was found that contrast sensitivity and isolated Landolt C acuity improved sooner and to a greater extent than the more complex visual acuity tasks. One patient who improved only on the simpler tasks complained that the enhanced contrast due to training made vision in that eye less acceptable because it was more confusing. The results show that multiple measures of visual acuity and contrast sensitivity are necessary to adequately monitor the effects of occlusion therapy.

Adult↗
PubMed2006

Comparison of higher-order aberrations and contrast sensitivity between Tecnis Z9001 and CeeOn 911A intraocular lenses: a prospective randomized study.

BACKGROUND: The advent of wavefront technology in the past five years has provided some insight into the optical outcomes of cataract surgery. The Tecnis Z9001 intraocular lens (Tecnis IOL, AMO) with a modified prolate anterior surface was claimed to reduce or even eliminate ocular spherical aberration to improve the visual quality. The purpose of this study was to determine whether Tecnis IOLs can improve the quality of vision as evaluated by measuring visual acuity, wavefront aberration, and contrast sensitivity. METHODS: In an intraindividual prospective study, 20 patients with bilateral cataract were randomly assigned to receive a modified prolate anterior surface IOL (Tecnis Z9001, AMO) in one eye and a biconvex spherical surface IOL (CeeOn 911A, AMO) in the other. After 3 months, the following were investigated: best corrected visual acuity, pupil diameter, photopic and mesopic contrast sensitivity, and wavefront aberration of the whole eye (ocular), cornea, and internal plane. RESULTS: The differences in the best corrected visual acuity and pupil diameter between the two groups were not statistically significant. Negative 4th-order spherical aberration (Z(4)(0)) was found in the Tecnis group, whereas positive Z(4)(0) found in the CeeOn group for the internal and ocular plane. Statistically significant differences were found at the ocular higher-aberrations between the two IOLs. Contrast sensitivity testing showed significantly better results in the Tecnis group at visual angles higher than 1.0 degree under photopic conditions and at visual angles higher than 1.6 degree under mesopic conditions both without glare and with glare in comparison with the CeeOn group. CONCLUSIONS: The Tecnis Z9001 IOL with a modified prolate anterior surface produces negative spherical aberration and consequently reduces the higher-order aberrations in pseudophakic eyes. This leads to enhanced contrast sensitivity and improved functional vision compared to conventional spherical IOLs.

Cataract↗
PubMed1986

The primate retina contains two types of ganglion cells, with high and low contrast sensitivity.

Previously, we discovered that the broadband cells in the two magnocellular (large cell) layers of the monkey lateral geniculate nucleus (LGN) are much more sensitive to luminance contrast than are the color-sensitive cells in the four parvocellular (small cell) layers. We now report that this large difference in contrast sensitivity is due not to LGN circuitry but to differences in sensitivity of the retinal ganglion cells that provide excitatory synaptic input to the LGN neurons. This means that the parallel analysis of color and luminance in the visual scene begins in the retina, probably at a retinal site distal to the ganglion cells.

Action Potentials↗
PubMed1990

A comparison of three clinical methods of spatial contrast-sensitivity testing in normal subjects.

Three methods clinically used for measuring spatial contrast sensitivity were performed monocularly in normal subjects to compare their sensitivity and applicability. The methods tested were (1) the Von Békésy tracking procedure, (2) the Method of Increasing Contrast, both carried out on a Nicolet CS-2000 automated Vision Tester, and (3) the Vistech Contrast Test System, a photographic test chart. The results show that the threshold sensitivities of the Von Békésy tracking procedure and the Method of Increasing Contrast were not significantly different. For sensitivity to middle and high spatial frequency, the Vistech test chart was found to approximate the Method of Increasing Contrast. With automated testing, a slower rate of contrast progression and a larger visual angle produced lower thresholds of detection of the contrast-sensitivity function. Using a slow rate of contrast progression, both the Vistech test chart and the Method of Increasing Contrast were rapidly conducted, easy to administer, and gave good approximations of the spatial contrast-sensitivity function.

Adult↗
PubMed1996

Development of grating acuity and contrast sensitivity in the central and peripheral visual field of the human infant.

Central and peripheral visual functions were measured simultaneously in 39 infants from 10 to 39 weeks old using a dual-frequency VEP technique. Central acuity and contrast sensitivity over a 4 deg circular field were measured at 6 or 8 Hz. Peripheral acuity and contrast sensitivity were measured simultaneously at the other rate with a semi-circular stimulus extending from 8 to 16 deg. The EEG was analyzed at 12 and 16 Hz to determine the separate responses for the central and peripheral fields. Both central and peripheral VEP acuity developed over the age range tested. Central acuity improved by about a factor of 2.6 over the age range tested, while peripheral acuity improved by about a factor of 2.2. Central acuity was always higher by an average factor of about 2.3. Contrast sensitivity showed similar development for the central and peripheral fields with an early rapid rise in sensitivity.

Adult↗
PubMed1991

Color-mediated contrast sensitivity in disabled readers.

Specific deficits in the processing of transient visual stimuli have been identified in reading-disabled children. It has been suggested that suitably chosen colored filters can assist reading-disabled children but this is controversial. In order to assess how colored lenses might assist a reading-disabled child, we compared contrast sensitivity judgments of 20 disabled readers with those made by 20 good readers of the same age. Contrast sensitivity thresholds were measured over a spatial frequency range of 0.4 to 12.8 cpd. Contrast sensitivity functions were recorded for each child under four different conditions. For each condition the child wore a spectacle frame with a colored filter which had been selected on the basis of the child's best and worst performances on a spatial location task (BEST and WORST), a neutral density optical filter (GRAY), and an untinted filter (CLEAR). The results showed that the best colored filter selected for each of the disabled readers dramatically reduced sensitivity as the spatial frequency moved into the range of printed material (i.e., sensitivity declined sharply from 0.4 to 12.8 cpd). In contrast, there was very little change in sensitivity for the good readers using their best filters. These provocative findings suggest that colored optical filters might improve transient-on-sustained inhibition in disabled readers. It is possible that individually designed filters will provide a way of mitigating the effects of weak transient processing in reading-disabled children. However, our results should not be interpreted as supporting the efficacy of prescribed, colored optical filters as a remediation technique for reading disability.

Child↗
PubMed2003

Reproducibility of morphoscopic contrast sensitivity testing with the Visual Capacity Analyzer.

PURPOSE: To determine the reproducibility of morphoscopic contrast sensitivity test values in healthy subjects using the Visual Capacity Analyzer (VCA) (L2 Informatique). SETTING: Institute of Vision Research, Department of Ophthalmology, Yong-Dong Severance Hospital, Yonsei University, Seoul, South Korea. METHODS: Five healthy volunteers were recruited for this study. With the VCA, 1 eye of each person was tested with different sized letters displayed on a computer screen at 11 spatial frequencies ranging from low (3.0 cycles/deg [cpd]) to high (30.0 cpd). The measurement was repeated 5 times under 2 screen luminance levels (maximum and 3 cd/m2). RESULTS: Under maximum luminance background, the coefficient of variation (CV) and reliability coefficient (RC) at the spatial frequencies examined ranged from 4.3% to 35.0% and 89.1% to 99.8%, respectively. Under a screen luminance of 3 cd/m2, the CV ranged from 0.5% to 15.9% and the RC, from 97.5% to 100.0%. CONCLUSION: At the spatial frequencies examined, morphoscopic contrast sensitivity testing using the VCA had a high level of reproducibility and may be useful in measuring a patient's visual function in the actual environment.

Adult↗
PubMed2005

Color vision and contrast sensitivity in epilepsy patients treated with initial tiagabine monotherapy.

The purpose of the study was to determine whether the use of a GABAergic antiepileptic drug (AED), tiagabine, affects color vision and contrast sensitivity. Twenty newly diagnosed patients with partial epilepsy (aged 19-72 years), receiving tiagabine as their initial monotherapy for 5-41 months were examined. Color vision was examined with the Standard Pseudoisochromatic Plates 2 (SPP2), with the Farnsworth-Munsell 100 Hue Test (FM100) and with the Color Vision Meter 712 (CVM) anomaloscope. Contrast sensitivity was measured with the Pelli-Robson letter chart. Three patients excluded from the color vision evaluation for congenital red-green color vision defects. Seven out of 17 patients (41%) had acquired color vision deficit examined with the FM100. The CVM anomaloscope revealed minor defects in two patients. Contrast sensitivity function was within normal ranges. The present study suggests that AED therapy with tiagabine, like with other established and newer AEDs may interfere with color perception.

Adult↗
PubMed1992

Contrast sensitivity of air-breathing nonprofessional scuba divers at a depth of 40 meters.

Photopic contrast sensitivity of air-breathing scuba divers was measured with a translucent test pattern at depths up to 40 m. The pattern was composed of sine wave gratings with spatial frequency and contrast changing logarithmically. The spatial transfer characteristics were measured at various depths under controlled optical conditions in seawater and in fresh water. Analysis indicates that the visual contrast sensitivity, and therefore probably also acuity, of sport divers is not affected up to depths of 40 m. This holds under ideal as well as poor diving conditions.

Adult↗
PubMed1992

[Contrast sensitivity in the fellow eye of unilateral age-related macular degeneration].

The VCTS 6000 Contrast Sensitivity Test System was used in testing the fellow eyes of 20 cases of unilateral age-related macular degeneration (ARMD), with age-matched normal controls. Among the patients, 25% of the fellow eyes showed minor contrast sensitivity reduction at medium and high spatial frequencies. This test may be useful in the diagnosis of subclinical ARMD.

Age Factors↗
PubMed2003

[Temporal contrast sensitivity in general population].

OBJECTIVE: To define the normal range of values for temporal contrast sensitivity (TCS) in the general population. MATERIAL AND METHOD: The study group consisted of 140 healthy subjects (280 eyes). Measurements were performed using a prototype designed to produce a red color flicker test (660 nm) with variable frequency and modulation, projected în the central visual field. We conducted test with 10, 20 and 30 Hz with highest illumination level. Subjects have been grouped according to age decades as well as sex. Each group was separately evaluated for distribution type, mean and confidence interval. Statistical differences were assessed using ANOVA with one variable. RESULTS: No significant differences could be found between male and female subjects and the response pattern is very similar în all age groups. Temporal contrast sensitivity presents a normal distribution, with a limited dispersion of data around mean value for the respective decade. TCS slightly decreases with age but correlation parameters do not gain statistical significance. Normal range was defined for age decades using the S score, which quantifies the distance from the mean and as such compensates for the differences generated by the non-linear relationship between age and TCS. The test S < 0 defines pathological circumstances with a specificity of 96.5% at 10 Hz, 99.3% at 20 de Hz and 95.4% at 30 de Hz respectively. CONCLUSIONS: We managed to establish normal TCS range of values for the general population using a test with a very good specificity. These normal values, obtained within a statistically significant group, represent the first step în using TCS în ophthalmologic research. Abnormal TCS changes can now be compared with normal values for each age group.

Adolescent↗
PubMed1991

The effects of parvocellular lateral geniculate lesions on the acuity and contrast sensitivity of macaque monkeys.

The effects of ablating the visual pathway that passes through the parvocellular (dorsal) LGN were tested in 2 macaque monkeys by measuring acuity and both luminance and chromatic contrast sensitivity. Thresholds were tested monocularly before and after ibotenic acid was used to lesion parvocellular layers 4 and 6 of the contralateral geniculate. The injections were centered at the representation of 6 degrees in the temporal field on the horizontal meridian, and vision was tested with localized stimuli at this location. In addition, in one of the monkeys, a lesion was made in magnocellular layer 1 of the opposite geniculate, and the same thresholds were tested. Physiological and anatomical reconstructions demonstrated complete destruction of the target layers in 1 parvocellular lesions and in the magnocellular lesion, and sparing of the nontarget layers in the tested region. Parvocellular lesions caused a 3-4-fold reduction in visual acuity within the affected part of the visual field, while the magnocellular lesion did not affect acuity. Both luminance and chromatic contrast sensitivity, tested with stationary gratings of 2 c/degree, were severely reduced by parvocellular lesions, but not affected by the magnocellular lesion. However, when luminance contrast sensitivity was tested with 1 c/degree gratings, counterphase modulated at 10 Hz, it was reduced by both parvocellular and magnocellular lesions. This study demonstrates that the parvocellular pathway dominates chromatic vision, acuity, and contrast detection at low temporal and high spatial frequencies, while the magnocellular pathway may mediate contrast detection at higher temporal and lower spatial frequencies.

Animals↗
PubMed2001

Impaired temporal contrast sensitivity in dyslexics is specific to retain-and-compare paradigms.

Developmental dyslexia is a specific reading disability that affects 5-10% of the population. Recent studies have suggested that dyslexics may experience a deficit in the visual magnocellular pathway. The most extensively studied prediction deriving from this hypothesis is impaired contrast sensitivity to transient, low-luminance stimuli at low spatial frequencies. However, the findings are inconsistent across studies and even seemingly contradictory. In the present study, we administered several different paradigms for assessing temporal contrast sensitivity, and found both impaired and normal contrast sensitivity within the same group of dyslexic participants. Under sequential presentation, in a temporal forced choice paradigm, dyslexics showed impaired sensitivity to both drifting and flickering gratings. However, under simultaneous presentation, with a spatial forced choice paradigm, dyslexics' sensitivity did not differ from that of the controls. Within each paradigm, dyslexics' sensitivity was poorer at higher temporal frequencies, consistent with the magnocellular hypothesis. These results suggest that a basic perceptual impairment in dyslexics may be their limited ability to retain-and-compare perceptual traces across brief intervals.

Adult↗
PubMed2002

Spatial contrast sensitivity of migraine patients without aura.

Visual disturbances are frequent symptoms in migraine. Since there is a possibility of separate damage in the magno- or parvo-cellular visual pathway in migraine patients, we performed a study including the measurement of static and dynamic spatial contrast sensitivity on 15 patients suffering from migraine without aura under photopic and scotopic conditions. Fifteen healthy volunteers without primary headache served as controls. The results revealed a marked decrease in contrast sensitivity at low spatial frequencies in the migraine patients. Spatial contrast sensitivity demonstrated some lateralization, as the sensitivity to low spatial frequencies obtained through separate eyes showed significantly larger side-differences in migraine patients than in control subjects. These findings suggest that the mechanisms responsible for vision at low spatial frequencies are impaired in migraine patients. This might indicate impaired function of the magnocellular pathways in this condition.

Adult↗
PubMed2002

Colour contrast sensitivity in ocular hypertension. A five-year prospective study.

PURPOSE: To evaluate a peripheral colour contrast sensitivity test as a tool for early diagnosis of glaucoma in a five-year prospective study. PATIENTS AND METHODS: Peripheral colour contrast sensitivity was measured with a computer graphics system developed by Arden et al. The test colours were varied along the protan, deutan and tritan colour confusion axes on a scale from 0 to 100 percentage units. Fifty-five ocular hypertensive (OH) patients examined with the colour contrast test, stereoscopic photography of the optic discs, and measurements of visual fields (Humphrey 24-2 glaucoma hemifield test (GHT)) in 1994, were re-examined after five years. RESULTS: Ten patients were 'outside normal limits' in the GHT at follow-up. This group of 10 patients did not differ in colour contrast thresholds at the test in 1994 from the 45 who were still 'normal' (or 'borderline') at follow-up. Neither were there proportionally more patients with GHT 'outside normal values' for the patients with high colour contrast thresholds (> 30% units) in 1994 regarding any of the three colour axes. As judged from patient files, 27 patients had developed glaucoma during follow-up. Although there were differences between these 27 glaucoma patients and the remaining OH group at the colour contrast test in 1994, these differences did not reach statistical significance for any of the colour axes (largest difference in the tritan axis: 6.2% units, P = 0.0745). At follow-up, however, there was a significant difference in colour contrast for the protan axis between the clinical glaucoma group and the OH group (6.7% units, P = 0.0105). CONCLUSION: The method used for colour contrast measurement did not reveal glaucomatous changes before conventional perimetry (Humphrey 24-2, GHT). Neither did it predict the patients who, in our clinic, subsequently developed glaucoma during a five-year period. A change over time in colour contrast in the protan axis for an OH patient may, however, indicate glaucoma development.

Color Perception↗
PubMed1966

The contrast sensitivity of retinal ganglion cells of the cat.

1. Spatial summation within cat retinal receptive fields was studied by recording from optic-tract fibres the responses of ganglion cells to grating patterns whose luminance perpendicular to the bars varied sinusoidally about the mean level. 2. Summation over the receptive fields of some cells (X-cells) was found to be approximately linear, while for other cells (Y-cells) summation was very non-linear. 3. The mean discharge frequency of Y-cells (unlike that of X-cells) was greatly increased when grating patterns drifted across their receptive fields. 4. In twenty-one X-cells the relation between the contrast and spatial frequency of drifting sinusoidal gratings which evoked the same small response was measured. In every case it was found that the reciprocal of this relation, the contrast sensitivity function, could be satisfactorily described by the difference of two Gaussian functions. 5. This finding supports the hypothesis that the sensitivities of the antagonistic centre and surround summating regions of ganglion cell receptive fields fall off as Gaussian functions of the distance from the field centre. 6. The way in which the sensitivity of an X-cell for a contrast-edge pattern varied with the distance of the edge from the receptive field centre was determined and found to be consistent with the cell's measured contrast sensitivity function. 7. Reducing the retinal illumination produced changes in the contrast sensitivity function of an X-cell which suggested that the diameters of the summating regions of the receptive field increased while the surround region became relatively ineffective.

Animals↗