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PubMed1990

The reliability of the Pelli-Robson contrast sensitivity chart.

Normative contrast sensitivity (CS) data were obtained using the commercially available Pelli-Robson chart from the dominant eye of 30 young (mean (+/- SD) age 22.5 +/- 4.3 years) and 42 older (mean (+/- SD) age 70.2+/- 6.7 years) subjects with normal healthy eyes. The majority of young subjects were found to have a CS of 1.80 log units or above. The majority of the older subjects were found to have a CS of 1.65 log units or above. CS results were obtained using both sides (A and B) of the Pelli-Robson chart from 30 (15 young and 15 older) of these subjects. These measurements were repeated under identical conditions, 2 weeks later. There was no significant difference between the results from sides A and B of the chart. The CS scores were shown to be repeatable to within +/- 0.15 log units or +/- 1 step. Therefore a significant change in CS score is +/- 2 steps or 0.30 log units. Slight improvements in reliability could be obtained by more careful permutation of letters on each step and a smaller step size. The restriction against these changes is the ensuing increased chart size.

Adult↗
PubMed1994

Effect of orientation on spatiotemporal contrast sensitivity in multiple sclerosis.

Spatiotemporal contrast sensitivity at three orientations, vertical, horizontal and oblique, was studied in 18 patients with clinically definite and laboratory-confirmed definite multiple sclerosis (MS). Nineteen age-matched control subjects were also studied under identical experimental conditions. Contrast thresholds for detecting steady and counterphase modulated (5 Hz) gratings ranging in spatial frequency from 0.5 to 12 c/deg were measured by a modified psychophysical method of limits. With the exception of two patients (three eyes) whose Snellen acuity scores were 20/70, all observers had acuity scores of 20/30 or better. All subjects were corrected for astigmatism. Orientation, spatial frequency and temporal frequency interacted differently in determining contrast sensitivity in the two groups of observers. For the controls, an oblique effect was present for both the steady and counterphase modulated gratings of high spatial frequencies, and there was no orientation-dependent loss of sensitivity for low spatial frequencies. For the observers with MS, there was no oblique effect, but sensitivity was dependent on orientation for the low spatial frequencies. Most patients with MS had reduced contrast sensitivity, compared to the controls, at one or more orientations. Counterphase modulation increased sensitivity to the low spatial frequencies and decreased sensitivity to the high spatial frequencies for both normal controls and patients with MS. In patients with MS this effect of temporal modulation on contrast sensitivity was markedly enhanced.

Adult↗
PubMed1994

Contrast sensitivity in a large adult population.

The contrast sensitivity test (using Vistech charts) was performed on a consecutive sample of 1612 eyes of 807 Republic of Singapore Air Force personnel (two diseased eyes excluded), which had no known ophthalmic disorder. This yielded a large sample norm of spatial Contrast Sensitivity Function (CSF) distribution curves, based on the local population. Although all subjects had their refractive errors fully corrected by spectacles, whenever necessary, to visual acuity of 6/6 or better, myopes had lower mean contrast sensitivity, in the higher spatial frequencies, compared to the emmetropic. Postulates were offered to explain this association, including the concept of micro-amblyopia. Pilots and aircrew performed consistently better than the ground crew, suggesting that target acquisition training may improve contrast sensitivity. Interestingly, sex was also shown to be associated with differences in contrast sensitivity: females were found to have lower spatial contrast sensitivity compared to males. Age was associated with poorer contrast sensitivity only at the lower spatial frequencies in this study sample, while race, with that of higher frequencies; Chinese having lower contrast sensitivity than other races (a heterogeneous group consisting of Malays, Indians, Eurasians and Others). The association of contrast sensitivity with race highlights the importance of using normograms based on the local population. All the above associations were statistically significant at P = 0.05, and independent of each other, based on analysis by multiple regression.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2005

An evaluation of the Mars Letter Contrast Sensitivity Test.

PURPOSE: The Mars Letter Contrast Sensitivity Test (initially known as the Lighthouse Letter Contrast Sensitivity Test) is similar in design to the Pelli-Robson Test but may offer several advantages. This study evaluates the repeatability of the Mars test and its agreement with the Pelli-Robson test in normal and low-vision subjects. METHODS: Fifty-four subjects were tested (age 22-86 years), including 20 normally sighted young adults, 17 normally sighted older adults, and 17 adults with low vision (20/16 to 20/250). Subjects were tested with both contrast sensitivity tests and with the ETDRS visual acuity chart. After a short break, subjects were retested with an alternate form of each contrast sensitivity test. The chart forms used (two Pelli-Robson and three Mars) and the order of testing were varied systematically. Testing was monocular with habitual correction and, for subjects over 40 years of age, included appropriate near add. Letter-by-letter scoring was used for both tests. Repeatability and agreement were assessed by determining the 95% limits of agreement (LoA): +/- 1.96 standard deviations of the differences between administrations or tests. RESULTS: The Mars test showed excellent agreement with the Pelli-Robson test, with 95% LoA of +/- 0.21 log units for all subjects. The Mars test was similarly repeatable (95% LoA = +/-0.20 log units) to the Pelli-Robson test (95% LoA = +/-0.20 log units) among all subjects. CONCLUSION: The new Mars Letter Contrast Sensitivity Test shows excellent agreement with the Pelli-Robson test and has similar repeatability. There are subtle differences in the actual contrast levels on different forms of the Mars test, and adjusting for these differences leads to superior repeatability of the Mars test. Thus, the Mars test may be a useful alternative to the Pelli-Robson test offering several advantages, including smaller size, improved durability, and ease of use.

Adult↗
PubMed1990

Paired comparison of contrast sensitivity in diffractive multifocal IOLs and conventional monofocal IOLs.

Multifocal intraocular lens (IOL) optics produce a retinal image of reduced contrast, which results from splitting incoming light between multiple focal points. This study sought to determine whether the reduced-contrast image results in functional loss of contrast sensitivity. Contrast sensitivity was measured in patients in the US Food and Drug Administration (FDA) study of the 3M Diffractive IOL, using the Pelli-Robson Letter Chart. Fifty-eight of these patients, including six from our clinic, were 'best-case' patients with no pathology, and also had paired multifocal/monofocal implants. Data from these 'best-care' patients with paired eyes indicate no functional difference in contrast sensitivity. Additional data obtained on our six patients with the Regan Low Contrast Charts suggest small predictable differences may exist for some patients at very low contrast levels. Further study is needed to determine whether these differences have functional significance.

Aged↗
PubMed1987

The contrast sensitivity function and childhood amblyopia.

We measured contrast sensitivity function and visual acuity in both eyes of strabismic and anisometropic amblyopic patients. There was a linear relationship between contrast sensitivity function and visual acuity in the amblyopic eye. As visual acuity decreased, the contrast sensitivity function decreased along the contrast sensitivity axis, and peak sensitivity shifted to lower spatial frequencies. After patching therapy, when visual acuity reached 20/20 in each eye, suggesting that the amblyopia was cured, there continued to be statistically significant difference in the contrast sensitivity functions between the eyes. The contrast sensitivity function from the previously amblyopic eye was depressed compared to the nonamblyopic eye. A comparison between patients with strabismic and anisometropic amblyopia showed that, when matched for visual acuity, the contrast sensitivity functions were similar for both the nonamblyopic and amblyopic eyes. However, a large difference was found between the amblyopic and nonamblyopic eyes of each group.

Amblyopia↗
PubMed1997

VISTECH contrast sensitivity testing in primary open angle glaucoma.

Contrast sensitivity has been recommended as a screening and diagnostic test in primary open angle glaucoma (POAG). We tested contrast sensitivity (CS) using Vistech charts in 184 eyes of 95 patients. Three groups were examined--established primary open angle glaucoma, glaucoma suspects and age matched controls. The distribution of contrast sensitivities amongst the three groups were similar. The median contrast sensitivity of glaucoma suspects and controls were well within normal limits while that of the POAG group fell along the lower limit of normal. In all three groups the younger subjects scored better than the older, indicating a depression of contrast sensitivity with increasing age. Even if depression of any one spatial frequency was considered abnormal, the test yielded a sensitivity of 55.4% and specificity of 69.5%. Similarly contrast sensitivity testing was found to be of little use in detecting field defects a maximum sensitivity of 47.3% and specificity of 73.3%. Vistech contrast sensitivity testing is not a useful test in POAG screening or diagnosis.

Adult↗
PubMed1987

The use of computerized contrast sensitivity, Arden gratings and low contrast letter charts in the assessment of amblyopia.

Contrast sensitivity measured with an electronic display was compared with Arden gratings and low contrast letter charts in normal and amblyopic children and adults. The low contrast letter charts and the Arden gratings used in the conventional manner revealed no additional information over that obtained by conventional Snellen acuity. However, the interocular differences found with each plate of the Arden gratings compared favourably with the computerized CSF. With the addition of an extra plate to test at a higher spatial frequency, the Arden gratings would be a useful technique for monitoring amblyopia therapy.

Adult↗
PubMed1985

Clinical detection of abnormalities in central vision in chronic simple glaucoma using contrast sensitivity.

Visual defect was assessed by contrast sensitivity and perimetry in 50 patients with chronic simple glaucoma. Abnormal contrast sensitivity using static gratings was found in patients with full central fields (i.e. a field of 15 degrees or more around fixation for the 12e isopter). It appears that central vision is affected by nerve fibre damage in the early stages of glaucoma, even in the presence of full central fields and normal visual acuity. Contrast sensitivity using temporally modulated gratings was reduced in the glaucoma patients, although this was found to be a less sensitive measure of visual loss than static contrast sensitivity function. These findings are discussed, and it is suggested that static contrast sensitivity function provides a simple method for detecting early visual defect in glaucoma and ocular hypertension.

Female↗
PubMed1980

Loss of contrast sensitivity following contusional eye injury.

Contrast sensitivity was evaluated in 95 patients who regained a visual acuity of 6/6 following a contusional injury of one eye. The injuries occurred 2 to 12 years prior to examination. A book of printed sinusoidal grating patterns of varying contrasts and spatial frequencies was used, and 15 patients were found to have a significant difference in contrast sensitivity between injured and uninjured eye. Eight patients had abnormalities of the media or fundus, and in 2 patients amblyopia was probably a factor. Five patients had a defect in contrast sensitivity in their injured eye, although no structural abnormalities could be detected on full clinical examination. Alterations in contrast sensitivity appeared to be a sensitive indicator of functional abnormality in eyes which appeared normal on ophthalmoscopy and other clinical investigations.

Adolescent↗
PubMed1990

Gain, noise, and contrast sensitivity of linear visual neurons.

Contrast sensitivity is a measure of the ability of an observer to detect contrast signals of particular spatial and temporal frequencies. A formal definition of contrast sensitivity that can be applied to individual linear visual neurons is derived. A neuron is modeled by a contrast transfer function and its modulus, contrast gain, and by a noise power spectrum. The distributions of neural responses to signal and blank presentations are derived, and from these, a definition of contrast sensitivity is obtained. This formal definition may be used to relate the sensitivities of various populations of neurons, and to relate the sensitivities of neurons to that of the behaving animal.

Animals↗
PubMed1997

Surround effects on the shape of the temporal contrast-sensitivity function.

The shape of the temporal contrast-sensitivity function at low temporal frequencies is sensitive to the relative luminance of the test and the surround. We show that this effect is due to greater sensitivity, in different conditions, either to the internal luminance modulation in the test or to temporal changes in the spatial contrast at the edge of the test. We measured temporal contrast sensitivity in tests at various luminance levels combined with surrounds at levels of higher, lower, or equal luminance as the test; compared the sensitivity for contrast modulation to luminance modulation at different temporal frequencies; and compared temporal contrast sensitivity in uniform and textured surround of equal mean luminance. Temporal contrast sensitivity was similar on equiluminant steady and out-of-phase modulating surrounds, indicating that the measured sensitivity for small tests in equiluminant surrounds is based on the detection of the temporal modulation of the spatial contrast at the edge of the test field. For all temporal frequencies, contrast sensitivity decreased as a monotonic function of the absolute magnitude of the Michelson contrast between test and surround. When small test fields of moderate to high intensities are embedded in dark surrounds, the sensitivity at lower spatial frequencies is similar to the sensitivities measured for a large test and may reflect sensitivity for luminance modulation within the test.

Contrast Sensitivity↗
PubMed1984

Contrast sensitivity in asymmetric glaucoma.

We measured central contrast sensitivity in both eyes of 27 patients with asymmetric glaucomatous visual field loss or optic disc cupping. In 15 patients contrast sensitivity was less in the eye that by perimetry or ophthalmoscopy was the more severely damaged. In 10 patients contrast sensitivity was the same in the two eyes. In two patients, it was impaired more in the eye with the normal visual field. However, the latter two patients had ophthalmoscopic evidence of optic nerve damage (disc hemorrhage or large cup) in the eye with the lower contrast sensitivity, even though the visual field was normal. Asymmetry of contrast sensitivity was not found in normal control subjects. These results suggest that glaucoma does alter central vision, even when visual acuity remains normal and visual field defects are far from fixation. Contrast sensitivity may be impaired by a different mechanism than that which leads to visual dield loss. Although the two types of visual dysfunction often occur together, some patients may have more severe impairment of central vision (as measured by contrast sensitivity testing) in one eye and more severe loss of peripheral vision (as measured by perimetry) in the other eye.

Glaucoma↗
PubMed1992

Effect of contact lens correction of sine wave contrast sensitivity in keratoconus patients after penetrating keratoplasty.

Contrast sensitivity testing reveals visual deficits not detected by standard acuity tests, providing a more sensitive measure of visual performance. Sine wave contrast sensitivity functions were examined for spectacle and contract lens correction of keratoconic eyes after penetrating keratoplasty (PKP). Contrast sensitivity was significantly higher for middle and high spatial frequencies with a rigid gas permeable contact lens than with glasses, even when Snellen acuity was identical for both forms of correction. Contrast performance correlated with subjective assessments of vision quality. This may be related to the quality of the keratometry mire images and suggests that mild irregularities in graft contour may be affecting contrast sensitivity. When considering the options for optical correction of grafted eyes, an evaluation of contrast sensitivity may help determine whether contact lens correction would optimize visual performance.

Adult↗
PubMed1996

The effect of pupil and observation distance on the contrast sensitivity function.

Measuring the contrast sensitivity function (CSF) is becoming more frequent in the analyses that are routinely done in optometric practice. This measurement is generally done in far vision, and the observation distance and its effects are not considered to significantly alter this function. Among these effects we should point out the accommodation of the visual optical system to the stimulus and the errors in accommodation associated with this, changes in pupil diameter and therefore in retinal illumination when the observation distance changes, the different level of aberrations (spherical aberration, astigmatism) for different cases, and so on. All of these factors contribute to the fact that the contrast sensitivity of a visual system varies according to the accommodative stimulus. In this study we attempt to clarify the influence of these different parameters by evaluating the CSF for three observation distances. The study was done in monocular vision, with a natural pupil and with a 3 mm artificial pupil that made it possible to maintain the same level of retinal illumination for all distances.

Accommodation, Ocular↗
PubMed1994

Measuring and predicting the effects of alcohol consumption on contrast sensitivity for stationary and moving gratings.

Contrast sensitivity was measured for 12 healthy young males while sober, after ingestion of an alcohol placebo, and after ingestion of alcohol (95% grain alcohol; mean estimated blood alcohol level = .088%). Observations were made for both stationary gratings and gratings that traveled through a circular path and required pursuit eye movements. The significant alcohol-related reduction in contrast sensitivity was 2.6 times greater for moving (.29-log-unit reduction) than for stationary gratings (.11-log-unit reduction). The loss in contrast sensitivity for the moving gratings of high spatial frequency (12 cpd) was particularly severe (.37 log unit). Estimated blood alcohol level was correlated with the loss in contrast sensitivity for moving gratings (r = .61), but not with the loss for stationary gratings. Estimated blood alcohol level was strongly correlated with the difference between the loss in contrast sensitivity to moving and stationary gratings (r = .75). These results are consistent with reports that alcohol consumption degrades the ability to make pursuit eye movements. Subjects' perceived intoxication level was not a reliable predictor of any index of visual performance.

Adult↗
PubMed1990

Normative contrast sensitivity data for young children.

Contrast sensitivity (CS) was measured in children ages 3 to 7 years using the Vistech Contrast Sensitivity distance chart (VCTS 6500). The purpose of the study was to determine how effectively the technique could be used with young children and to establish normative data for this age group. Of 286 children participating in a vision screening, the contrast sensitivity function (CSF) was measurable on 241 (84%) under binocular conditions and 229 (80%) under both binocular and monocular conditions. The 219 binocular CSF's and 208 monocular CSF's obtained from visually normal children were used to establish normative data and then compared to similar data from 50 visually normal young adults. The results indicated that there is an effect of age between 3 and 7 years, children are significantly less sensitive than adults, and adult-like levels of CS are not yet reached at 7 years of age. In addition, although the children's mean contrast thresholds fell within the norms provided with the VCTS 6500, the variability in the children's CSF's precludes using the Vistech data for diagnostic purposes in the young. The normative data are presented to assist the clinician in evaluating CS in young children when using the VCTS 6500.

Adult↗
PubMed1989

Measurement of spatial contrast sensitivity with the swept contrast VEP.

Contrast response functions (CRFs) for the VEP were obtained with a Discrete Fourier Transform (DFT) technique employing swept contrast gratings. VEP CRFs in infants were found to have a form similar to those observed in adults, being linear functions of log contrast over a range of near-threshold contrasts. CRFs with low and high contrast lobes were present in infants, as they are in adults. Contrast thresholds were estimated by extrapolation of the CRF to zero microvolts. The effects of additive EEG noise and of the DFT data window on the shape of the measured CRF are considered. For large signals, the measured CRF is nearly independent of the additive noise, but at small signal values additive noise introduces a small bias towards larger amplitudes. The VEP signal-plus-noise distribution was modeled as a family of Rice distributions in order to evaluate the effects of bias on the estimates of threshold. The amount of bias depends inversely upon the slope of the CRF. The amount of bias introduced by a smoothing window also depends upon slope of the CRF as well as the sweep rate. The combined effects of additive noise and window bias were such that the total bias was nearly independent of CRF slope. Sweep VEP contrast thresholds were shown empirically to be unaffected by changes in the range of contrast swept.

Adult↗