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PubMed1995

Contrast sensitivity in Alzheimer's disease: a 1-year longitudinal analysis.

Spatial contrast sensitivity was evaluated in normal elderly adults and a group with probable Alzheimer's disease (AD) in three sessions over a 1-year period. There was evidence of a reduction over 1 year in contrast sensitivity for static, high spatial frequencies in both groups of subjects. A striking difference between the subject groups was observed in their response to flickered stimuli. Although normal elderly adults yielded good stability in sensitivity for both static and flickered spatial frequencies over the 1 year, AD patients experienced a significant decline in response to flickered (7.5 Hz) stimuli. The significant decline in sensitivity for low contrast, high temporal events in AD patients is consistent with reports of cell loss at the retinal and cortical levels of the magnocellular (M) channel in AD. Thus, the spatial contrast sensitivity change in AD may reflect a more rapid loss of cells specifically in the M channel over a 1-year period.

Adult↗
PubMed2000

Reduced recovery of temporal contrast sensitivity after flicker stress in patients with glaucoma.

PURPOSE: To compare recovery of temporal contrast sensitivity after flicker stress between control subjects and patients with glaucoma. METHODS: Forty-three patients with primary open-angle glaucoma and secondary open-angle or normal-tension glaucoma of the Erlangen Glaucoma Registry and 30 healthy control subjects had their temporal contrast sensitivity measured at 37 Hz and their recovery time determined after monocular exposure to 30 seconds of 58% contrast full-field flicker. Recovery time of temporal contrast sensitivity was measured as the time interval from cessation of flicker until twice the threshold value was reached. RESULTS: Patients with glaucoma had a significant reduction in temporal contrast sensitivity (P < 0.001). Recovery time was also significantly longer in patients with glaucoma (23.8 +/- 24.1 seconds) than in control subjects (7.6 +/- 2.6 seconds; P < 0.001). There was a significant positive correlation between recovery time and mean visual field defect (0.5; P < 0.001) and a significant negative correlation between recovery time and neuroretinal rim area of the optic disc (0.32; P = 0.04). CONCLUSIONS: Recovery of temporal contrast sensitivity after flicker stress is impaired in some patients with glaucoma. This might be the result of functional impairment of the inner retina, outer retina, or both in glaucoma.

Adaptation, Ocular↗
PubMed1993

Modeling the contrast-sensitivity functions of older adults.

To determine whether a parabolic template is a good description of the contrast-sensitivity functions (CSF's) exhibited by older adults, the curve-fitting method of Pelli et al. [J. Opt. Soc. Am. A 3(13), P56 (1986)] was applied to contrast-sensitivity data from 100 older subjects (ages 53-85 years). Although the method resulted in reasonable fits for most subjects, closer inspection revealed that this technique may be problematic. A significant number of observers had functions that were nonparabolic, and for many subjects the error tended to be concentrated at the peak of the CSF. In addition, in contrast to the study of Pelli et al., the peak contrast sensitivities of the subjects were only weakly related to Pelli-Robson contrast sensitivity and letter acuity. The data were also fitted with an asymmetric function of variable shape. Whereas this function provided a better fit to the nonparabolic CSF's, it resulted in inferior fits to most of the remaining data. These results demonstrate that the spatial CSF's of older adults cannot be described by a single parametric curve such as a parabola or a function of an exponential and that Pelli-Robson contrast sensitivity and letter acuity are not adequate predictors of their peak contrast sensitivities.

Adolescent↗
PubMed1999

Temporal contrast sensitivity with peripheral and central stimulation in glaucoma diagnosis.

AIMS: To evaluate temporal contrast sensitivity with full field, peripheral, and central stimulation and to determine the most sensitive corresponding retinal area for glaucoma damage. METHODS: Temporal contrast sensitivity was determined either with a full field, a peripheral annular area from 30 degrees to 90 degrees, or a central area from 0 degree to 30 degrees at a frequency of 37.1 Hz. 232 eyes of 232 subjects were included. They were classified into four groups: eyes with ocular hypertension (OHT, n = 54), "preperimetric" glaucomas (n = 73) with glaucomatous optic disc abnormalities but no visual field loss, "perimetric" glaucomas (n = 53) with visual field loss, and 52 normals. RESULTS: In all four groups, temporal contrast sensitivity was almost equal with full field and peripheral, but significantly higher than with central stimulation (p < 0.001). With regard to the diagnostic power of the three different stimulus areas, OHTs and glaucomas were found to be best discriminated from normals by peripheral stimulation. CONCLUSIONS: According to these results, temporal contrast sensitivity seems to be determined by peripheral retinal areas. As the diagnostic power of the three different stimulus areas was best with the peripheral stimulation, this condition should be used for early glaucoma diagnosis.

Adult↗
PubMed2006

Impairment of contrast sensitivity in long-term lorazepam users.

RATIONALE: Oculomotor balance and contrast sensitivity are known to be impaired after an intake of a single dose of lorazepam. To the best of our knowledge, these effects have not been explored in long-term users of lorazepam, despite the potential importance of such deficits in everyday life. OBJECTIVE: We tested the ophthalmological effects and contrast sensitivity for static stimuli in long-term lorazepam users. MATERIALS AND METHODS: There were 15 lorazepam users and 15 sex-, age- and education level-matched control subjects tested, using a simple blind procedure. RESULTS: The ophthalmological effects were scarce, with a discrete exophoria. Visual acuity was preserved. Contrast sensitivity, however, was more markedly impaired, consistent with the effects of an acute dose of lorazepam. The effects were not correlated with anxiety or sedation. CONCLUSIONS: The results are discussed in terms of their possible impact on everyday life. As visual acuity does not allow the detection of the impairments that are observed in the present study, it is suggested that a more systematic exploration of contrast sensitivity be carried out in long-term users of benzodiazepines.

Adult↗
PubMed1993

Prospective evaluation of the effect of pseudophakic cystoid macula edema on contrast sensitivity.

OBJECTIVE: To evaluate the effect of pseudophakic cystoid macular edema (PCME) on contrast sensitivity. DESIGN: Best-corrected visual acuity, fluorescein angiogram, and contrast sensitivity measurements were obtained before surgery and at 8 weeks and 8.5 months after surgery. Eyes were classified as having no PCME, transient PCME, or persistent PCME. PARTICIPANTS: The study population consisted of 31 consecutive patients undergoing extracapsular cataract extraction with posterior chamber intraocular lens implantation between September 1990 and March 1991. MAIN OUTCOME MEASUREMENTS: Outcomes were best-corrected visual acuity and contrast sensitivity. RESULTS: Analysis of variance showed a significant decrease for all spatial frequencies at 8 weeks (P < .005) and for higher frequencies at 8.5 months (P < .05) in both PCME groups and for higher frequencies at 8 weeks in the transient PCME group. CONCLUSION: Decrease in contrast sensitivity associated with PCME may account for persistent visual difficulties despite good Snellen visual acuity.

Cataract Extraction↗
PubMed1993

Contrast sensitivity function in Graves' ophthalmopathy and dysthyroid optic neuropathy.

Contrast sensitivity function was measured by a computer automated method on 38 eyes with dysthyroid optic neuropathy and 34 eyes with Graves' ophthalmopathy only. The results were compared with 74 healthy control eyes. Disturbances of contrast sensitivity functions were found in both groups when compared with controls. The eyes affected with dysthyroid optic neuropathy showed pronounced loss of contrast sensitivity in the low frequency range, which facilitates differentiation between the two groups.

Adult↗
PubMed1992

Sawtooth contrast sensitivity: effects of mean illuminance and low temporal frequencies.

Temporal contrast sensitivity was measured for mirror-image sawtooth (rapid-on and rapid-off) and sine waveforms for a 1.8 deg foveal target. In one experiment, contrast sensitivity was measured for 2-26 Hz stimuli at target mean illuminance levels of 5-1260 td. At 5 td, contrast sensitivity functions for sawtooth and sine waveforms, expressed in terms of the Fourier fundamental amplitude, are equivalent. At higher light levels, sawtooth sensitivity increasingly exceeds sine sensitivity and rapid-off (decremental) sawtooths show progressively greater sensitivity than rapid-on (incremental) sawtooths. This pattern of results was obtained for two color-normal observers and for a deuteranopic observer. In a second experiment, sawtooth and sine sensitivity was tested at 500 td with an extended low-frequency range, to 0.5 Hz. Rapid-off and rapid-on sensitivities declined only slightly at low temporal frequencies in contrast with sine sensitivity. To interpret our data, we evaluate two single-pathway models (last-stage asymmetric detector and compressive response-intensity non-linearity) and a dual-pathway model in which incremental and decremental waveforms are detected by separate ON and OFF visual mechanisms.

Adaptation, Ocular↗
PubMed1984

Spatial contrast sensitivity of dark-reared cats with striate cortex lesions.

We measured the spatial contrast sensitivity of two dark-reared cats before and after bilateral ablations of area 17 and parts of area 18. These lesions produced large deficits in the contrast sensitivity of both cats at intermediate and high spatial frequencies. This postoperative reduction in contrast sensitivity in dark-reared cats is relatively similar to the sensitivity deficits produced by the same cortical lesions in normally reared cats. However, both pre- and postoperatively, the normally reared cats exhibited contrast sensitivity that is clearly superior to that of the dark-reared cats. The results demonstrate both that striate cortex is significantly involved in the spatial contrast sensitivity of dark-reared cats and that dark rearing produces widespread deficits, independent of those in striate cortex, through much of the visual system.

Animals↗
PubMed1991

Comparison of contrast sensitivity functions across three orientations: implications for theory and testing.

The contrast sensitivity functions of a large group of observers (N = 71) were determined for three orientations of test gratings: vertical, oblique, and horizontal. Comparison of group means indicated that, consistent with previous findings for the 'oblique effect', sensitivity was poorer for the oblique orientation-but only for the mid-high spatial frequencies. Correlation analyses indicated that contrast sensitivity for a particular spatial frequency at a given orientation was highly correlated with contrast sensitivity for that same frequency at the other two orientations. Factor analysis of the intercorrelations revealed two strong factors, a low frequency factor, and a mid-high frequency factor. Results are discussed in terms of: (a) the implications for contrast-sensitivity testing across orientations, (b) the basis for the oblique effect, and (c) a different type of evidence for a dichotomy among spatial-frequency channels that may reflect the distinction between X cells and Y cells or between the parvocellular and magnocellular systems.

Adult↗
PubMed1975

Contrast sensitivity of individual colour mechanisms of human vision.

1. Contrast sensitivity functions of isolated colour mechanisms were measured at spatial frequencies from 0-2 to 32 c/deg. The contrast sensitivity vs. spatial-frequency functions of the red (pi5) and green (pi4) mechanisms are similar, while the blue (pi3) mechanism has lower absolute sensitivity and lower resolving power. Isolation of a single mechanism never increases its maximum sensitivity. 2. The shape of the contrast sensitivity function of a colour mechanism is established within the mechanism. Little if any inhibitory interaction takes place among colour mechanisms. 3. Differences that have been reported between the sensitivities of the red and green mechanisms, as well as the apparent "supersensitivity" of the isolated green mechanism, may be artifacts that result from the extrapolation procedures that were used to estimate the absolute sensitivities of the colour mechanisms.

Adaptation, Ocular↗
PubMed2002

Contrast sensitivity after laser in situ keratomileusis. one-year follow-up.

PURPOSE: To determine whether contrast sensitivity measurement, a more sensitive test of visual function than visual acuity, better characterizes visual outcomes after laser in situ keratomileusis (LASIK). SETTING: Hong Kong Laser Eye Centre, Hong Kong, China. METHODS: Contrast sensitivity was monitored in 41 LASIK patients for 1 year. Seven spatial frequencies (0.3, 0.8, 1.5, 3.4, 6.9, 10.3, and 20.5 cpd) were tested with 15 sequences per spatial frequency, and a staircase technique was used for target presentation. RESULTS: There was a general depression in the contrast sensitivity function after LASIK; 1.5 cpd and 3.4 cpd were the most affected frequencies. Recovery took at least 6 months. The reduction in contrast sensitivity was greater for higher amounts of myopia. CONCLUSION: The post-LASIK nonpermanent depression in contrast sensitivity was probably due to optical factors.

Adult↗
PubMed1990

Assessment of the Vistech contrast sensitivity test for repeated-measures applications.

Contrast sensitivity using Vistech plates was measured repeatedly in normal subjects to determine predictive power. The contrast sensitivity measures were quite stable from the first administration, and practice effects were not observed. Test-retest reliability was lowest for the lower spatial frequencies, but was adequate throughout if more than one measurement was made. Threshold scores for all five spatial frequencies were generally not independent and factor analysis revealed that only two spatial frequency domains were relatively independent: high and low. The correlations between adjacent spatial frequencies were highest, and correlations decreased as distance between spatial frequencies increased. To detect subtle differences all three Vistech plates should be used to arrive at a threshold for each spatial frequency and, if time permits, more measures should be taken at the lower spatial frequencies to compensate for the lower reliability. This method is believed to be adequate for repeated-measures clinical and experimental studies.

Adult↗
PubMed1993

Aging and neural spatial contrast sensitivity: photopic vision.

This study investigated the extent to which older adults' loss in spatial contrast sensitivity at a photopic level is attributable to neural changes in the aged visual system. Laser interferometry was used to generate interference fringes which bypass the optics of the eye in presenting a grating target on the retina. Older adults in good eye health exhibited on average a small but statistically significant loss (0.1-0.2 log unit) in contrast sensitivity across the spatial frequency range tested, although there was considerable overlap between young and old adults. This loss in contrast sensitivity for interference fringes accounted for less than half of the photopic contrast sensitivity loss at higher frequencies reported for older adults in studies using conventional direct-viewing techniques in which the optics of the aged eye are not bypassed. We conclude that neural changes in the aged visual system have a rather minor contribution to older adults' loss in spatial contrast sensitivity at a photopic level.

Adolescent↗
PubMed1988

Contrast sensitivity in age-related macular degeneration.

Low-contrast charts were used to investigate the possibility that patients with drusen have visual deficits not detected by standard Snellen charts. We compared performance on Regan letter charts between 52 eyes with drusen and Snellen acuity of 20/20 and 27 control eyes. The drusen group read fewer letters than the control group on all of the charts tested. This difference increased as the contrast of the charts decreased. The loss of performance on all of the Regan charts correlated with drusen severity. Twenty-one eyes with drusen and normal Snellen acuity also were tested with a Ginsburg contrast sensitivity chart and compared with age-matched normal controls. The results showed a loss of contrast sensitivity at high spatial frequencies and a loss of peak contrast sensitivity with increasing drusen severity. These results suggest that in patients with drusen, low-contrast charts may be useful for measuring visual loss not detected by standard Snellen charts.

Adult↗
PubMed1981

Contrast sensitivity in anisometropic amblyopia.

Contrast sensitivity functions were measured for sinusoidal gratings from a sample of 10 anisometropic amblyopes. A high spatial frequency deficit was found from tests of the amblyopic eyes of all subjects. This defect decreased with spatial frequency and was correlated with the magnitude of anisometropia. Controls were instituted to rule out psychophysical method and residual defocus as possible causes of these effects. At low spatial frequencies, there were small differences between the two eyes. For some subjects, sensitivities of the amblyopic eyes appeared actually higher than normal whereas the reverse was found for most of the others. Additional tests demonstrated that the low-frequency differences could be accounted for by magnification differences (aniseikonia) between the two eyes. These findings are consistent with the idea that monocular contrast deprivation is the causal agent in anisometropic amblyopia.

Adolescent↗
PubMed1984

Contrast sensitivity and orientation selectivity in lamina IV of the striate cortex of Old World monkeys.

Contrast sensitivity and orientation selectivity were measured for neurons in lamina IV of macaque striate cortex. Contrast sensitivity was determined for a range of spatial frequencies, using a staircase method. The stimuli were at the optimal orientation, direction and speed of drift for each neuron. The assignment of each recording site to a subdivision of lamina IV was made by histological reconstruction of each electrode penetration from sections reacted for cytochrome oxidase and stained for Nissl substance. Neurons in the magnocellular recipient zone of IVc (IVc alpha) have high contrast sensitivities, while those in the parvocellular recipient zone (IVc beta) have low contrast sensitivities. Both of the upper subdivisions of lamina IV (IVa and IVb) contain a mixture of neurons with high and low contrast sensitivities. There were orientation selective neurons within all subdivisions of lamina IV, even in IVc, whereas non-oriented neurons were found only in those subdivisions that receive a direct parvocellular geniculate input (IVa and IVc beta).

Animals↗
PubMed1993

Contrast sensitivity and disability glare in the middle years.

Spatial contrast sensitivity and disability glare were measured in a large sample (n = 90, 30 per decade) of middle-aged subjects, aged 21-50 years, who had clear media and were ophthalmologically normal. We found no significant differences in the contrast sensitivities as a function of age in the middle years for (1) gratings generated on a monitor; (2) interference gratings generated in the retinal plane; (3) gratings in the presence of glare; and (4) mesopic increment thresholds with and without glare. The large sample size provides sufficient statistical power (0.8) for one to conclude that contrast sensitivity, optical quality, and foveal neural sensitivity are unlikely to vary more than 0.1 log unit between the ages of 21 and 50 in ophthalmologically normal subjects with clear media.

Adult↗