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PubMed1995

The contributions of ON- and OFF-pathways to contrast sensitivity and spatial resolution in goldfish.

DL-2-amino-4-phosphonobutyric acid (APB) reduces the sensitivity of ON- and OFF-responses in goldfish retina, although the ON-responses are reduced significantly more than the OFF-responses. This paper describes the effects of APB on behavioral sensitivity of goldfish to spatial sinusoidal gratings. Fish were classically conditioned to suppress respiration upon presentation of gratings drifting at 1 Hz; contrast thresholds were measured by an observer-based two-alternative forced-choice procedure. Thresholds were repeated following intraocular injections of APB or physiological saline. Saline had no effect, but APB dramatically reduced contrast sensitivity and shifted contrast sensitivity functions to lower spatial frequencies. The results suggest that both ON- and OFF-pathways are necessary for normal spatial vision and that the effects of APB are consistent with the disruption of both ON- and OFF-pathways.

Aminobutyrates↗
PubMed1984

Contrast sensitivity determined with the spatial bandwidth equalization technique: threshold, suprathreshold, and spatiotemporal measurements.

Contrast sensitivity functions were obtained from normal subjects using a spatial bandwidth equalization (SBE) technique and the more conventional display method. Static sensitivity measurements obtained with the two methods were in good agreement. However, when the patterns were counterphase flickered , sensitivity to the lower spatial frequencies was enhanced using the conventional method while sensitivity measured with the SBE technique was slightly depressed. The SBE method also was used to investigate suprathreshold contrast perception with static and flickering gratings. In general, the perception of contrast was independent of spatial frequency content of the stimulus, especially with increasing contrast levels and flicker frequencies. These studies have shown that the SBE technique is an acceptable method to assess static contrast sensitivity and suprathreshold contrast perception.

Humans↗
PubMed2006

Driver contrast sensitivity and reaction times as measured through a salt-covered windshield.

BACKGROUND: The objective of this study was to use contrast sensitivity measurements to determine the effect of windshield salt film on driver vision. This effect simulates road salt spray that dries in place on a vehicle windshield during winter driving conditions. METHODS: Ten emmetropic subjects were tested to assess contrast sensitivity functions through windshields that were clear compared with the same stimuli as viewed through windshields coated with salt film. Achromatic stimuli were generated by a VisionWorks system and were presented at 4 spatial frequencies (0.5, 3, 10, and 20 cycles per degree). RESULTS: A significant reduction in contrast sensitivity through the salt film was found at all spatial frequencies. In addition, reaction time to detect the stimuli was also found to be increased significantly at 2 of the 4 spatial frequencies through the saline-covered windshield. CONCLUSION: The results of this study indicate that windshield salt film reduces the ability to detect high and low contrast objects in a simulated driving environment as well as increases the subjects' reaction times.

Adult↗
PubMed1992

[Contrast sensitivity and vision].

From results of the contrast sensitivity test (n = 65, r = 0.834) it is possible to estimate visual acuity with considerable provedes, however, in addition also information on vision at low contrast conditions and on vision of large objects. It may therefore be expected that in future the two-dimensional visuogram will replace in clinical practice the commonly used test used for assessment of visual acuity.

Contrast Sensitivity↗
PubMed1987

Reliability and validity of simple photographic plate tests of contrast sensitivity.

Sets of edge and square wave grating photographic plates of varying contrasts were used to measure the mid to low spatial frequency range of the contrast sensitivity function (CSF) of 20 subjects with evident ocular disease and 20 age-matched normal subjects. Both plate tests were shown to have good test-retest reliability and to correlate well with electronic cathode ray tube (CRT) measures of CSF. The edge test, when administered in 2-dB steps of ascending contrast, has optimum sensitivity of 0.70 and specificity of 0.84 for detecting the patient with ocular disease with a fail criterion of less than 38 dB. A measure of edge contrast sensitivity was also shown to be a good predictor of the peak of the CSF, which is shown to be largely independent of the visual acuity of the subject. The 2 c/deg and 4 c/deg plates did not provide more information about the visual difficulties of subjects than the edge test. We advocate the use of an edge test as a simple clinical measure of low spatial frequency contrast sensitivity that provides information about visual dysfunction not provided by a measure of visual acuity.

Adult↗
PubMed1990

Effect of levodopa on contrast sensitivity and scotomas in human amblyopia.

The neurotransmitter dopamine (DA) is involved in several visual functions. Visual deprivation decreases retinal DA concentration in chickens and monkeys. In animals with deprivation amblyopia, several studies suggest that neurotransmitters are involved in visual-cortical plasticity and can restore partial visual acuity in adult cats. We investigated in a cross-over, double-masked study the influence of levodopa on contrast sensitivity and binocular suppression in human adult strabismic and amblyopic patients. After one single administration of levodopa, a significant increase in contrast sensitivity and decrease of the size of the fixation point scotoma was found. No changes could be detected after placebo administration. Levodopa did not induce changes in contrast sensitivity in the dominant eyes of the patients or in normal subjects. In conclusion, we found a short-term effect of levodopa on contrast sensitivity and fixation point scotomas in amblyopic eyes of adult patients.

Adult↗
PubMed2002

Contrast sensitivity to radial frequencies modulated by Jn and jn Bessel profiles.

We measured human contrast sensitivity to radial frequencies modulated by cylindrical (Jo) and spherical (jo) Bessel profiles. We also measured responses to profiles of jo, j1, j2, j4, j8, and j16. Functions were measured three times by at least three of eight observers using a forced-choice method. The results conform to our expectations that sensitivity would be higher for cylindrical profiles. We also observed that contrast sensitivity is increased with the j n order for n greater than zero, having distinct orderly effects at the low and high frequency ends. For n = 0, 1, 2, and 4 sensitivity tended to occur around 0.8-1.0 cpd while for n = 8 and 16 it seemed to shift gradually to 0.8-3.0 cpd. We interpret these results as being consistent with the possibility that spatial frequency processing by the human visual system can be defined a priori in terms of polar coordinates and discuss its application to study face perception.

Adult↗
PubMed1986

An assessment of decision-making as a possible factor in the age-related loss of contrast sensitivity.

The possibility that changes in decision-making may contribute to the age-related decline in contrast sensitivity has been investigated in nineteen young subjects (ages 21-38 years) and twenty-seven old subjects (ages 55-92 years). A signal detection paradigm was employed in which the detection of stationary sinusoidal grating patterns was measured at 3 and 15 cycles deg-1 for a range of contrasts which were psychophysically equivalent for each subject. A decline in contrast sensitivity with age at the spatial frequencies studied was confirmed for contrast thresholds obtained both by the ascending method and from the 50% hit rate for detection of the grating pattern. The criterion adopted for decision-making, expressed as both beta and percentage bias, did not change significantly between young and old subjects at 15 cycles deg-1. At 3 cycles deg-1, criterion beta did not change significantly at X0.8, X1.0, or X1.2 contrast threshold, but at contrast giving 50% hit rate there was a significant increase with age. The percentage bias increased significantly at contrast threshold but not at 50% hit rate. It is inferred from the results that the loss of contrast sensitivity was not accountable in terms of the adoption of a more conservative criterion by older subjects. Hence visual loss in ageing is attributed to changes within the visual pathway rather than within higher decision-making centres.

Adult↗
PubMed1987

Normative contrast sensitivity functions: the problem of comparison.

Sixty college age observers who were prescreened for 6/6 (20/20) acuity were examined twice on an automated contrast sensitivity system. A significant practice effect was evident in the obtained contrast sensitivity functions (CSF's). In addition, marked differences were found between the contrast sensitivity scores in the present work and the normative CSF reported by other investigators using similar methods. Implications for the rapid assessment of CSF in applied settings and for the use of published CSF norms are discussed.

Adult↗
PubMed2000

Screening for CMV retinitis using chromatic discrimination thresholds and achromatic contrast sensitivity.

BACKGROUND: Many patients with cytomegalovirus retinitis (CMVR) are unaware of visual disturbance so screening is advocated for patients with HIV and low CD4 counts. Many tests of retinal function have been recommended but few are effective at detecting CMVR. We assess the potential of chromatic discrimination thresholds and achromatic contrast sensitivity as screening tests for patients with CMVR. METHOD: 11 HIV+ patients with CMVR, 16 age matched HIV+ patients, and 29 age matched controls were recruited. Visual acuity, chromatic discrimination thresholds, and achromatic contrast sensitivity were measured. Fundal examination was performed by slit lamp biomicroscopy for HIV+ patients. Those with CMVR were photographed and the CMVR graded from the photographs. RESULTS: Loss of chromatic discrimination was found in patients with CMVR (tritan p<0.0005, red/green p<0.05). The same group had deterioration in achromatic contrast sensitivity at 2.2, 3.4, and 10 cpd (p<0.05). There was correlation between the zone of CMVR with chromatic gratings (tritan r=0.83, p<0.005). No statistically significant difference was found between the HIV+ patients and the controls for all tests (p>0.1). CONCLUSIONS: HIV+ patients with CMVR have a loss of chromatic discrimination and achromatic contrast sensitivity and this may be used to screen HIV+ patients for CMVR.

AIDS-Related Opportunistic Infections↗
PubMed1994

Influence of type and severity of pure forms of age-related cataract on visual acuity and contrast sensitivity. Italian American Cataract Study Group.

PURPOSE: To compare the relationship between logMAR visual acuity (VA) and cataract severity and between contrast sensitivity (CS) and cataract severity in pure types of age-related lens opacities. METHODS: Analysis included patients followed in the ongoing Italian-American Study of the Natural History of Age-Related Cataract. Lens opacities were classified and graded according to the Lens Opacities Classification System II (LOCS II). Visual acuity was measured with the Early Treatment Diabetic Retinopathy Study Chart. Contrast sensitivity was measured with the Pelli-Robson chart. RESULTS: Data from 1,076 eyes were used for the analysis (366 clear lenses; 550, 124, and 36 eyes with cortical, nuclear and posterior subcapsular cataract, respectively). In age-adjusted analyses, increasing severity of all three cataract types was associated with progressively higher logMAR VA, which translates into poorer acuity, and lower CS scores. For both VA and CS, the effect of increasing severity was greatest for nuclear and least for cortical opacities. After adjusting for age and VA, CS scores were no longer associated with cataract type and severity, with the exception of advanced cortical opacities. CONCLUSIONS: Increased cataract severity, as determined by LOCS II grading, is strongly associated with both VA and CS scores. Contrast sensitivity scores obtained from testing at low spatial frequency do not seem to offer additional information over standard VA testing in early cortical and posterior subcapsular opacities nor in nuclear cataracts.

Aged↗
PubMed2000

Spatial covert attention increases contrast sensitivity across the CSF: support for signal enhancement.

This study is the first to report the benefits of spatial covert attention on contrast sensitivity in a wide range of spatial frequencies when a target alone was presented in the absence of a local post-mask. We used a peripheral precue (a small circle indicating the target location) to explore the effects of covert spatial attention on contrast sensitivity as assessed by orientation discrimination (Experiments 1-4), detection (Experiments 2 and 3) and localization (Experiment 3) tasks. In all four experiments the target (a Gabor patch ranging in spatial frequency from 0.5 to 10 cpd) was presented alone in one of eight possible locations equidistant from fixation. Contrast sensitivity was consistently higher for peripherally- than for neutrally-cued trials, even though we eliminated variables (distracters, global masks, local masks, and location uncertainty) that are known to contribute to an external noise reduction explanation of attention. When observers were presented with vertical and horizontal Gabor patches an external noise reduction signal detection model accounted for the cueing benefit in a discrimination task (Experiment 1). However, such a model could not account for this benefit when location uncertainty was reduced, either by: (a) Increasing overall performance level (Experiment 2); (b) increasing stimulus contrast to enable fine discriminations of slightly tilted suprathreshold stimuli (Experiment 3); and (c) presenting a local post-mask (Experiment 4). Given that attentional benefits occurred under conditions that exclude all variables predicted by the external noise reduction model, these results support the signal enhancement model of attention.

Attention↗
PubMed2004

Effect of blue staining of expandable hydrophilic intraocular lenses on contrast sensitivity and glare vision.

PURPOSE: To evaluate the effect of trypan blue staining of expandable hydrophilic acrylic intraocular lenses (IOLs) on contrast sensitivity and glare. SETTING: Department of Ophthalmology, Federal University, and Oculistas Associados, Rio de Janeiro, Brazil. METHODS: Phacoemulsification with expandable hydrophilic IOL implantation was performed in 19 eyes. Group 1 (stained group) consisted of 12 eyes with the IOL unintentionally stained by trypan blue 0.1% solution during surgery; Group 2 (unstained group) consisted of 7 eyes with IOLs that were not stained because trypan blue was not used during surgery. The eyes were examined postoperatively for Snellen best corrected visual acuity (BCVA), contrast sensitivity BCVA, and glare vision. The examiners were masked to whether the IOL was stained by trypan blue. Inclusion criteria included a BCVA of 20/30 or better 1 month postoperatively. Patients who had other ocular pathology or previous ocular surgery were excluded from the study. RESULTS: The mean postoperative BCVA was 20/24 in the stained group and 20/23 in the unstained group (P =.73). The mean contrast sensitivity visual acuity was 20/31 in the stained group and 20/26 in unstained group (P =.10). The mean glare visual acuity was 20/75 and 20/33, respectively (P =.03). CONCLUSIONS: Patients with expandable hydrophilic acrylic IOLs stained with trypan blue performed significantly worse on a glare vision test than patients whose IOLs were not stained. Cataract surgeons should avoid using trypan blue with this IOL type.

Acrylic Resins↗
PubMed1975

Changes in the contrast sensitivity function induced by contact lens wear.

Contrast sensitivity functions (i.e. minimum contrast required to resolve a sine wave grating as a function of spatial frequency) were determined for subjects when wearing normal spectacle corrections and when wearing either hard or soft contact lenses. Corections provides a more definitive evaluation of visual performance with contact lenses than do the conventional clinical procedures.

Adult↗
PubMed1999

[Effect of luminance on contrast sensitivity and glare in the mesopic range].

BACKGROUND: Elderly persons applying for driving licence frequently are not able to fulfil the recommendations given by DOG and relating to twilight vision without and with glare. One reason may be the low level of luminance used for this test. MATERIALS AND METHODS: We compared contrast threshold with and without glare in the mesopic range of vision measured by two types of Rodenstock Nyktometers. One instrument was the standard, commercially available instrument (500) and in the other instrument (500 S) the luminance of the viewing field was raised by a factor of three and the luminance of the glare source by a factor of 2.2. We tested 50 persons divided in three groups aged 20 to 49, 50 to 59 and over 60 years. RESULTS: With the standard instrument, some of the younger persons and nearly all of the elder ones were not able to fulfil the requirements for driver licensing. With the modified instrument (500 S), the group of the elder was divided in a greater part now able to fulfil the recommendations and a smaller one unable even at this luminance level. The standard deviation of the measured contrast sensitivity was one step of the contrast scale of the instruments. We also tested the influence of adaptation time on the contrast sensitivity. Only very few persons showed slightly better results after 15 minutes of adaptation compared to 5 minutes. DISCUSSION: The luminance of today's headlights of motor cars is significantly higher than those at the time when the DOG rules where acquired. Testing contrast sensitivity without and with glare on a higher luminance level will reduce the number of those persons not able to fulfil the requirements for drivers licensing. The revision of these rules is discussed.

Adult↗
PubMed2005

[Long-term effects of iterative diving on visual field, color vision and contrast sensitivity in professional divers].

PURPOSE: To assess long-term functional effects of iterative diving, we studied visual field, color vision, and contrast sensitivity in 21 French Navy professional divers and 21 controls. PATIENTS AND METHODS: This retrospective study investigated a population of 21 divers and 21 controls. All subjects were male. The inclusion criterion for divers was a total number of dives greater or equal to 1,000. Exclusion criteria for the two groups were glaucoma, ocular hypertension, smoking, and vasospastic risks. Additional exclusion criteria for controls were any history of diving practice and of hyperbaric oxygen therapy. The visual field was examined with a Humphrey Central 30-2 threshold test. Moreover, we explored spatial contrast sensitivity using Metrovision Moniteur Ophtalmologique "STAT" program and color vision with desaturated 15 hue test. RESULTS: None of the divers had any loss of spatial contrast sensitivity. There was a high frequency of yellow-blue axis color vision defects (45.2%) in the diver group. Regarding visual field, corrected pattern standard deviation was significantly higher in divers (p<0.01). CONCLUSION: These findings suggest that iterative diving may cause subclinical functional effects on vision. Further studies will be needed to determine the exact setting of this repercussion upon macula and/or the optic nerve.

Adult↗
PubMed1983

Effects of luminance on contrast sensitivity in senile macular degeneration.

Patients with senile macular degeneration (SMD) often have difficulties in adapting to changing luminance levels. They may complain of problems at both high and low luminance levels, although some patients have their vision function markedly improved at high luminance levels. We examined the effect of luminance on the contrast sensitivity function in six patients with SMD and five normals of approximately the same age. The contrast sensitivity of the SMD patients compared to the control subjects was reduced at 72 cd/m2 but was comparable to that of the controls at 0.007 cd/m2. The peak of the contrast sensitivity function was moved to lower spatial frequencies at all luminances in the SMD group, and the slope of the function relating contrast sensitivity to luminance was reduced. These data suggest that adaptation mechanisms which optimize contrast detection are disrupted in SMD. Further disturbances of function might be expected in the dynamics of the adaptation process.

Adaptation, Ocular↗
PubMed1996

Contrast sensitivity in one-eyed subjects.

The effects of early monocular form deprivation on the developing mammalian visual system, and the anatomical and physiological consequences of early monocular enucleation, suggest that the remaining eye of human subjects who had the other eye removed early during development might be capable of supernormal performance. To test this inference, the achromatic contrast sensitivity of the remaining eye of subjects who had the other eye removed at different ages after birth was compared with that of normal subjects tested under monocular and binocular conditions. The results show that all subjects who had an eye removed during early development had a higher contrast sensitivity than the better eye of control subjects. Furthermore, the earlier in development that the eye was removed, the lower the spatial frequency at which contrast sensitivity is enhanced compared with measurements made in the better eye of control subjects, and the larger the range of spatial frequencies over which contrast sensitivity is supernormal.

Adolescent↗