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PubMed1986

Electrophysiological assessment of contrast sensitivity in human infants.

Contrast sensitivity functions (CSF's) were measured for a group of 6-month-old infants using the visual evoked potential (VEP). Sine-wave luminance gratings were counterphase modulated at 12 contrast reversals per s and simultaneously swept in contrast. Each contrast sweep lasted 10 s, spanning a range of 0.5 to 40% contrast in 19 equal logarithmic steps. The amplitude and phase of the response at the second harmonic were determined by a discrete Fourier transform. Contrast thresholds were estimated from a linear extrapolation to zero-amplitude of the VEP amplitude vs. log-contrast function. Contrast sensitivity was found to be nearly adult-like at 1 c/deg, but was not yet mature at higher spatial frequencies.

Child Development↗
PubMed1982

Receptive field properties of x and y cells in the cat retina derived from contrast sensitivity measurements.

The contrast sensitivity to gratings drifting at 2.0 Hz has been measured for X and Y type retinal ganglion cells, and these data have been used to characterize the sizes and peak sensitivities of centers and surrounds. The assumption of Gaussian sensitivity distributions is adequate for both types of cells, but allows a better description of X than of Y cells. The size and peak sensitivity can be specified more precisely, in general, for the center than for the surround. The data also show that for both types of cells (1) center radius increases with eccentricity, but is two to three times larger than Y cells than for X cells at a given eccentricity, (2) spatial resolution is an excellent predictor of center size, (3) the larger the center or surround, the lower its small spot sensitivity at a specific mean lumminance and (4) the surround is nearly as strong as the center for large or diffuse stimuli. X cell surrounds are relatively weaker in the middle of the receptive field than Y cell surrounds, but X cell surrounds are larger relative to their centers.

Action Potentials↗
PubMed1981

Cross-species correspondence of spatial contrast sensitivity functions.

Spatial contrast sensitivity functions (CSFs) have been obtained for at least 9 species, including man. In the present paper, the shapes and octave band widths of these functions are compared. For most species, the shape of the CSF was an inverted-U, and the full width at half amplitude of the CSFs varied less than one octave. These similarities suggest that there is a close correspondence of the CSFs of these diverse animals; the major difference is the location of each CSF in the spatial frequency domain.

Animals↗
PubMed1983

Practical applications of the contrast sensitivity function.

The contrast sensitivity function, as a statement of visual capabilities over a wide range of object sizes, has proved to be a valuable tool in the study of visual mechanisms. This paper examines the more clinical applications of the function which may be of interest to practising optometrists. These applications include the assessment of binocularity and aids to the recognition of conditions not picked up by more conventional tests.

Adult↗
PubMed1981

Contrast sensitivity gratings in glaucoma family screening.

Contrast sensitivity was measured in the eyes of 200 consecutive patients attending the glaucoma family screening unit. One-third of the patients screened had an abnormal contrast sensitivity. Positive correlation (p less than 0.01) existed between this abnormal contrast sensitivity and cup : disc ratio, visual field loss, and age. No such correlation existed between contrast sensitivity and intraocular pressure.

Age Factors↗
PubMed1985

Contrast sensitivity in diabetics with and without background retinopathy.

Contrast sensitivity measurements were obtained from 64 patients with insulin-dependent (IDDM) and non-insulin-dependent (NIDDM) diabetes mellitus who had normal Snellen acuity and minimal or no visible diabetic retinopathy. Contrast thresholds were determined for stationary gratings at six spatial frequencies, ranging from 0.5 to 22.8 cycles/degree (c/deg), and for 1.0-c/deg gratings phase-alternated at 15 Hz. Data from each group of diabetic patients were compared with data from age-matched normal subjects. We found that (1) patients with IDDM and no retinopathy had normal contrast sensitivity, (2) patients with NIDDM and no retinopathy had abnormal contrast sensitivity at only one spatial frequency (22.8 c/deg), and (3) patients with NIDDM and background retinopathy had abnormal contrast sensitivity at all spatial frequencies tested. We also found a dissociation of Snellen acuity and contrast sensitivity, indicating that contrast sensitivity can be used as an early index of changes in the retina not demonstrated by measurements of visual acuity.

Adolescent↗
PubMed1998

Relationship between contrast sensitivity and metabolic control in diabetics with and without retinopathy.

Contrast sensitivity was studied in diabetic adolescents and young adults with and without retinopathy in order to evaluate their central vision, to analyze the relationship of metabolic control to the presence and severity of retinopathy, and to re-evaluate the response to this test after a significant improvement in metabolic control. Twenty adolescent and young adult diabetics without retinopathy and 40 diabetics with retinopathy of varying degree were enrolled in the study; 20 healthy age and sex-matched subjects served as controls. Contrast sensitivity was assessed with a CSV-1000 contrast testing instrument, testing for four spatial frequencies, 3, 6, 12 and 18 cycles per degree (cpd). Diabetics with no retinopathy showed a weak but significant difference at 18 cpd compared with controls (P = 0.04), while diabetics with background retinopathy showed a significant reduction of contrast sensitivity at 12 and 18 cpd when compared with controls (P < 0.001). In patients with preproliferative/proliferative retinopathy a highly significant reduction of contrast sensitivity at all frequencies was found compared with controls. Furthermore, these patients had a significantly lower mean contrast sensitivity than patients without retinopathy. The patients were re-evaluated after a significant amelioration of metabolic control. An improvement in contrast sensitivity was found in diabetics without retinopathy and with background retinopathy, while there was no change observed in diabetics with severe retinopathy. These results show that diabetic adolescents and young adults with and without signs of retinopathy observed by fluorescein angiography have a reduced contrast sensitivity, which is more severe in patients with preproliferative/proliferative retinopathy. A significant amelioration of metabolic control is associated with an improvement of contrast sensitivity in all patients with the exception of those patients who had signs of preproliferative/proliferative retinopathy observed by fluorescein angiography. In summary, this longitudinal study provides the first evidence that reduced contrast sensitivity is reversible in diabetics with or without background retinopathy only.

Adolescent↗
PubMed1984

The relationship of contrast sensitivity functions to sports vision.

Contrast sensitivity, a more recent test of visual function, has never been studied in its relationship to sports vision. The hypothesis that contrast sensitivity functions among college varsity level baseball players significantly differs from that of a random sample of optometry students was tested using Arden grating plates. A statistically significant difference was found at the 98 percent confidence level, demonstrating that in this study, a sample of college varsity level baseball players have higher level contrast sensitivity functions than those of a randomly selected sample of Southern California College of Optometry students.

Adolescent↗
PubMed1990

Peripheral contrast sensitivity in glaucoma and ocular hypertension.

Contrast sensitivity has been measured in patients with glaucoma and ocular hypertension, the latter graded into high, medium, and low risk clinical groups. Measurements were made centrally and peripherally at 10 degrees, 15 degrees, 20 degrees, and 25 degrees off-axis at each of the four meridians 45 degrees, 135 degrees, 225 degrees, and 315 degrees. A sine wave grating of 1.9 cycles/degree, reversing at 1 Hz was used. It was displayed on a 100-Hz refresh rate monitor. Normal values were established to compare those from 41 eyes from patients with either primary open angle glaucoma (POAG) with minimal field loss detectable on a Humphrey perimeter, or raised IOP and/or disc changes but no field loss (OH). Those with POAG had normal central contrast sensitivity, but at 20 degrees and 25 degrees eccentricity the values were greater than 2 standard deviations above the normal mean. This was also the case for high risk OH, but not for low risk patients. All the high risk patients except one who had abnormal peripheral contrast sensitivity had possible field defects (threshold elevation at one or more points more than 5 but less than 10 dB above normal mean). Only one of those with normal peripheral contrast sensitivity had such 'suspect points'. The results are assessed in terms of screening of glaucoma suspects.

Contrast Sensitivity↗
PubMed1989

[Contrast sensitivity in dialyzed patients].

In a group of 57 patients with chronic terminal renal insufficiency, treated by haemodialyses a significantly reduced sensitivity to contrast was observed. Changes in the sensitivity to contrast do not correlate with the period of dialyzation treatment.

Adolescent↗
PubMed1993

The effects of grating area and spatial frequency on contrast sensitivity as a function of light level.

Contrast sensitivity was measured as a function of retinal illuminance (I) for vertical cosine gratings of various circular areas (A) and spatial frequencies (f < or = 4 c/deg). Spatial frequency and grating diameter varied in inverse proportion to each other in order to keep the relative grating area (A x f2) constant at either 3.14, 12.6, 50.3, or 201 square cycles. At all grating areas and spatial frequencies contrast sensitivity in dim light first increased in proportion to the square root of retinal illuminance. Then the increase saturated and contrast sensitivity became independent of luminance level in bright light. For gratings with constant relative area contrast sensitivity functions were similar in shape and had the same maximum sensitivity but were shifted horizontally towards lower illuminances with decreasing spatial frequency. However, when replotted as a function of retinal illuminance divided by spatial frequency squared, contrast sensitivity functions fell on a common curve at all levels of relative retinal illuminance (I/f2).

Adult↗
PubMed1994

Contrast sensitivity after resolution of central serous retinopathy.

The contrast sensitivity of 21 patients was measured using TV equipment (Wavetek 143 function generator and Sony PVM-90CE video monitor) and the Vistech test 6-15 years after the acute stage of central serous retinopathy. In the majority of cases contrast sensitivity was lower in the affected eye. The difference between the affected and the fellow eye was statistically significant at 1 and 6 cycles/degree (c/d) but not at 19 c/d. In 13/21 cases (62%) the results of the Vistech test were consistent with those of the TV test. Contrast sensitivity did not correlate with the duration of the disease or with the ultimate clinical picture of the macula. At 6 c/d there was a statistically significant correlation between visual acuity and contrast sensitivity. If the visual acuity was less than 1.0, contrast sensitivity was decreased, but decreased contrast sensitivity was also observed in four eyes with normal visual acuity, indicating that the level of visual deficit may not be established by measurement of visual acuity alone.

Adult↗
PubMed1997

Contrast sensitivity in diabetic pregnancy.

PURPOSE: To evaluate the correlation between the changes in contrast sensitivity and retinopathy throughout pregnancy in diabetic women with mild background diabetic retinopathy. METHODS: Contrast sensitivity (Vistech 6500 Contrast Test System) was measured in 22 type I diabetic women with mild background retinopathy [0-16 microaneurysms (MAs)/eye and occasional small intraretinal hemorrhages] and 10 healthy pregnant women at the 12th and 32nd weeks of pregnancy and 3 months after delivery. Red-free fundus photography was also performed at all visits. RESULTS: Throughout pregnancy contrast sensitivity was lower in the diabetics than in the controls at 1.5, 3.0, and 6.0 cycles per degree (cpd). During the course of pregnancy, contrast sensitivity decreased at 1.5 and 6.0 cpd in patients with more than five new MAs compared to those with fewer than five new MAs during pregnancy. Likewise, contrast sensitivity decreased at 6 cpd in patients with an increase in MA count during pregnancy and at 6 and 12 cpd in patients with a baseline MA count of two or more MAs. CONCLUSIONS: Contrast sensitivity, especially at low to mid-range spatial frequencies, is decreased in diabetic women with mild retinopathy. Even small changes in retinopathy are reflected in a decrease in contrast sensitivity during and after pregnancy. Thus, contrast sensitivity seems to be a sensitive indicator of changes in minimal background retinopathy.

Adult↗
PubMedDate not supplied

Mesopic contrast sensitivity function after laser in situ keratomileusis.

PURPOSE: To evaluate contrast sensitivity under mesopic conditions in patients who have undergone uncomplicated bilateral laser in situ keratomileusis (LASIK) for myopia. METHODS: Best-corrected monocular contrast sensitivity was measured with the Stereo Optical F.A.C.T. chart at 1.5, 3, 6, 12, and 18 c/deg in 20 patients (20 left eyes) before and after bilateral LASIK (with the Nidek EC-5000 excimer laser and the Automated Corneal Shaper). Mean preoperative refractive error was -6.40 +/- 1.28 D (range -4.00 to -8.00 D) and postoperative mean refractive error was -0.41 +/- 0.45 D (range -0.75 to +0.50 D). Contrast sensitivity function was measured before and 6 months after surgery using four different chart luminances: 85, 5, 2.5, and 0.1 cd/m2, the first being a photopic level and the rest mesopic. Log contrast sensitivity values at each spatial frequency were used for statistical analysis and normalized values for graphical representation. RESULTS: Contrast sensitivity of postoperative LASIK eyes did not differ from preoperative values at a photopic level (85 cd/m2). However, under mesopic conditions (5 cd/m2 or less) a statistically significant reduction (P<.01) in contrast sensitivity was found at high spatial frequencies (12 and 18 c/deg), although no significant contrast sensitivity differences were observed at low and middle spatial frequencies (P>.01 for 1.5, 3 and 6 c/deg). CONCLUSIONS: LASIK induced significant reductions in contrast sensitivity under mesopic conditions only at high spatial frequencies, even though the photopic contrast sensitivity function was normal.

Adult↗
PubMed1985

Spatial contrast sensitivity in patients with multiple sclerosis.

Contrast sensitivity tests a basic visual function which is not examined by conventional visual acuity testing or visual evoked responses. It is frequently abnormal in patients with multiple sclerosis. The lack of relationship between VERs and SCSF implies that contrast sensitivity measures aspects of the visual system not examined by the conventional electrophysiological technique, probably visual function situated beyond the anterior visual pathway. It is therefore a useful complementary diagnostic test for patients with multiple sclerosis. Both VER and spatial contrast sensitivity separately detect a high proportion of patients with multiple sclerosis. When used in combination, the two techniques give a yield which approaches 100%. Contrast sensitivity testing as used here is cumbersome and time-consuming. Use of fewer spatial frequencies and/or adaptation of VER techniques for estimation of a contrast threshold may be more applicable for clinical use.

Adult↗
PubMed1991

[Contrast sensitivity in aphakia and artiphakia].

Examination of the contrast sensitivity in aphakic eyes corrected by glasses and in artephakias provides information which cannot be obtained by measurement of visual acuity and is thus a suitable supplement of the basic test of visual functions. Contrast sensitivity declines significantly with advancing age. Contrast sensitivity of aphakic eyes corrected by glasses corresponds to values of contrast sensitivity of phakic eyes of the same age group. Artephakias with an iris clip lens have a contrast sensitivity reduced by cca one half as compared with a control group, while in artephakias with a posterior chamber lens there is a decline by one third, as compared with a control groups of the same median age.

Adult↗
PubMed1991

Effects of spherical and astigmatic defocus on acuity and contrast sensitivity: a comparison of three clinical charts.

Two contrast sensitivity charts (Vistech and Pelli-Robson) have become available to the eye care practitioner. Their value as clinical tools for the assessment of visual function may be enhanced because of either an insensitivity to the effects of optical focus or a hypersensitivity to defocus. We compared the sensitivity to defocus of these charts to the traditional Snellen chart by examining the effect of up to +/- 5.00 D of spherical and astigmatic defocus on performance with each chart. In order to simulate the two types of clinical examination scenarios, tests were performed both with and without mydriatic/cycloplegic agents. The Pelli-Robson contrast sensitivity chart was very resistant to the effects of all types of optical defocus. As predicted, the high spatial frequencies on the Vistech chart were sensitive to defocus. However, although contrast sensitivities for the low frequencies were affected less, optical defocus produced significant decreases in low frequency Vistech contrast sensitivity. In addition, the Vistech chart was very insensitive to axis 180 blurring lenses. There was no indication that either contrast sensitivity chart was more sensitive to defocus than the standard Snellen chart.

Adult↗
PubMed2000

[Synopsis of various electrophysiological tests in early glaucoma diagnosis--temporal and spatiotemporal contrast sensitivity, light- and color-contrast pattern-reversal electroretinogram, blue-yellow VEP].

BACKGROUND: Of the three glaucoma-defining criteria intraocular pressure, optic-nerve damage, and visual field damage, the latter is a late symptom. Therefore, in order to improve an early sensory diagnosis, new tests are necessary. It is the aim of the present paper to test new sensory methods, to rank them in an order of sensitivity, and to base them on possible pathophysiological mechanisms. PATIENTS AND METHODS: The tests were carried out in subjects of the Erlangen Glaucoma registry: Normals, patients with ocular hypertension, and patients with open-angle glaucoma without or with field defects. The tests are designed to preferentially probe the function of different groups of ganglion cells. Psychophysical methods: Temporal contrast sensitivity in a ganzfeld as "Erlangen flicker test" and spatio-temporal contrast sensitivity to test Magno-cell function. Electrophysiological methods: Pattern-reversal electroretinogram with a luminance-contrast pattern to test Magno-cell function, color-contrast pattern electroretinogram for Parvo-cell function, and blue-on-yellow visual evoked potential to test the "blue-sensitive" pathway. RESULTS: The most sensitive test is the temp.CS, it is significantly reduced in OHT (p < 0.01). The spatio-temp.CS is reduced in perimetric stages (p < 0.01). The BY-VEP is altered in the preperimetric stage (p < 0.01), the PR-ERG in perimetric stages (p < 0.01). The CC-ERG is reduced in even later stages. These results are in agreement with the hypothesis that tests selective for non-redundant neurons are of early diagnostic value. Multivariate analyses increase the early diagnostic value when different functions are tested in combination. CONCLUSIONS: When a particular test is taylored to the the special needs of certain groups of ganglion cells sensory defects can be observed before the occurrence of optic-nerve damage (OHT). The most sensitive psychophysical test is the "Erlangen flicker test" which is a screening test selective for M cells. The most sensitive electrophysiological test is the BY-VEP testing the blue-sensitive ganglion cells.

Color Perception↗