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PubMedDate not supplied

Contrast sensitivity function after cataract extraction and intraocular lens implantation.

Divergent contrast sensitivity findings have been reported in patients with intraocular lens implants. The purpose of this study was to determine contrast thresholds of patients with good visual acuity after uncomplicated cataract extraction and posterior chamber conventional IOL implantation. Fifty-two eyes of fifty two patients, who had undergone uncomplicated extracapsular cataract extraction and posterior chamber intraocular lens implantation together with 48 eyes of 48 control subjects were tested for contrast sensitivity function. All of the patients had best corrected visual acuity 0.8 (20/25) or better, on the Snellen scale. Patients with concomitant eye disease were excluded. Contrast sensitivity was measured using stationary sine-wave gratings of four spatial frequencies (3.0 to 18.0 cycles/degree), at the testing distance of 8 feet. A loss of contrast sensitivity was found in patients with intraocular lens implants, compared with control subjects of similar age, sex and visual acuity. The loss was statistically significant at intermediate (6 cyc/deg) and high spatial frequencies (12.0 and 18.0 cycles/degree), while it was not statistically significant at low spatial frequencies (3 cyc/deg). This may be the reason of nonspecific visual complaints ('washed-out images'), despite normal Snellen acuity, after cataract surgery and monofocal IOL implantation.

Cataract Extraction↗
PubMed1995

Contrast sensitivity in organic-solvent-induced chronic toxic encephalopathy.

This is a study of visual contrast sensitivity in a series of subjects with previously diagnosed occupational organic-solvent-induced chronic toxic encephalopathy. Contrast sensitivity was measured for 16 subjects using the Vistech VCTS 6500 chart. The results were compared with age-stratified normal data. Six of the 16 subjects (37.5%) recorded abnormal contrast sensitivity results. Monocular abnormalities were found for two (33%) of these subjects. Statistically significant abnormalities in contrast sensitivity were observed at the intermediate spatial frequencies of three cycles per degree (cpd; P < .0005), 6 cpd (P < .025), and 12 cpd (P < .01). We conclude that contrast sensitivity is abnormal in some cases of occupational organic-solvent-induced chronic toxic encephalopathy. Intermediate spatial frequency channel neurones in the visual system may be more vulnerable to solvent toxicity than those of low or high spatial frequency. Contrast sensitivity testing may be a useful adjunct in the diagnostic process for this disease. Further research involving larger numbers of subjects is recommended.

Adult↗
PubMed2000

Contrast sensitivity and glare disability by halogen light after monofocal and multifocal lens implantation.

BACKGROUND: Standard examination of contrast sensitivity under conditions of glare disability is performed with incandescent light. A new halogen glare test that simulates glare as seen with oncoming vehicle headlights was used to measure glare disability in patients implanted with multifocal and monofocal intraocular lenses (IOLs). METHODS: 28 patients with an average age of 69 years (SD 12 years) were implanted with a monofocal IOL (SI-40NB, Allergan) and 28 patients with an average of 66 years (12 years) were implanted with a refractive multifocal IOL (Array-SA-40N, Allergan). All patients were followed for 5 months postoperatively. Contrast sensitivity at four spatial frequencies (3, 6, 12, and 18 cycles per degree, cpd) with and without a glare source were measured using the halogen glare test (CSV-1000 HGT). Statistical analysis was performed using the two sample Wilcoxon test. The local significance level was set at 0.05. RESULTS: When tested at the lowest spatial frequency (3 cpd) without halogen glare, contrast sensitivity was lower in the multifocal group than in the monofocal group (p=0.0292). With additional glare, there was no difference between both groups. At all other spatial frequencies (6, 12, and 18 cpd), when tested without halogen glare (6 cpd, p=0.5250; 12 cpd, p=0.8483; 18 cpd, p=0.9496) and with moderate (3 cpd, p=0.7993; 6 cpd, p=0.4639; 12 cpd, p=0.7456; 18 cpd, p=1.0) and high halogen glare (3 cpd, p=0. 1513; 6 cpd, p=0.2016; 12 cpd, p=0.3069; 18 cpd, p=0.9933), there was no statistically significant difference between groups. Patients in both groups of age 70 or older had reduced contrast sensitivity without halogen glare and with moderate and strong glare. When monofocal and multifocal patients older than 70 years of age were analysed separately, there was no statistically significant difference in contrast sensitivity with and without glare. Astigmatism >1 dioptre had no significant influence on contrast sensitivity and glare disability when monofocal and multifocal eyes were compared. CONCLUSION: Reduced contrast sensitivity was found in the multifocal group only at the lowest spatial frequency without halogen glare. The monofocal and multifocal groups had no statistically significant differences in contrast sensitivity with moderate and strong glare. These results suggest no difference in glare disability induced by halogen light similar to oncoming vehicle headlights for patients implanted with monofocal and multifocal IOLs.

Adult↗
PubMed1989

Postnatal development of the spatial contrast sensitivity of X- and Y-cells in the kitten retinogeniculate pathway.

The sensitivity to spatial contrast patterns of single retinal ganglion cell axons and neurons in the A-layers of the dorsal lateral geniculate nucleus (LGNd) was measured in 4 1/2- and 6 1/2-week-old kittens and adult cats. Drifting sinusoidal grating stimuli were presented at 6-12 spatial frequencies to obtain spatial contrast sensitivity functions (SCSFs). The SCSFs were normalized for the postnatal growth of the kitten eye and were interpreted using a difference of Gaussians model of the receptive field (RF). The average optimal spatial frequency, spatial frequency bandwidth, and the proportion of cells that were selective for spatial frequency did not differ significantly between the kittens and adults for ganglion cells belonging to the cluster 1 (X-) or cluster 2 (Y-) functional types. The spatial resolution of kitten ganglion cells was also adultlike, except for that of Y-ganglion cells with peripheral RFs, which was significantly higher than in the adult. The spatial resolution of X-LGNd neurons with peripheral RFs was significantly poorer at 4 1/2 weeks than in the older animals. The proportion of X-LGNd neurons that were selective for spatial frequency increased between 4 1/2 and 6 1/2 weeks postnatally, but the spatial frequency bandwidth of selective cells did not change. The increased proportion of spatially selective LGNd neurons is probably due to the maturation of intrageniculate inhibitory circuits. Developmental changes in spatial resolution were interpreted as resulting from an increase (Y-retinal ganglion cells) or decrease (X-LGNd neurons) in RF center size. A model of retinogeniculate development is presented that attributes postnatal expansion of Y-retinal ganglion cell RF centers to increased functional convergence from more distal retinal neurons and reduction in LGNdX-cell RF center size to decreased convergence from X-retinal ganglion cells.

Animals↗
PubMed1984

[Effect of grid orientation of interference patterns on contrast sensitivity in white and colored light].

The contrast sensitivity of 34 healthy eyes and 32 suspected of having glaucoma was measured at 3, 6, 12, 18, and 24 cycles/degree with vertical, oblique and horizontal interference fringes. These were produced by the Haag-Streit Visometer as modified by Lotmar with an additional device for contrast variation. At all frequencies, maximum contrast sensitivities were found for vertical gratings. However, there was a tendency for oblique gratings to show relatively low contrast sensitivities at high spatial frequencies; the same applied for horizontal gratings at low frequencies. The effect of stimulus orientation was similar for white, red, green and blue light.

Adult↗
PubMed1996

[Improving contrast sensitivity by cut-off filters in high adaptation luminance levels in retinitis pigmentosa].

BACKGROUND: Contrast requirements in patients suffering from retinitis pigmentosa (RP) exceed those of healthy subjects. So far, studies examining contrast sensitivity have been performed at luminance levels of several 100 cd/m2. However, to simulate as closely as possible outdoor levels of luminance, several 1000 cd/m2 are necessary. PATIENTS AND METHODS: We used the Vistech contrast sensitivity charts at a standard high luminance of 5500 cd/m2. Contrast sensitivity was evaluated in 20 healthy subjects (visual acuity 1.10 +/- 0.15) and 25 patients with RP (visual acuity 0.50 +/- 0.29) with and without commercially available cut-off spectacle filters (Zeiss F 80, Zeiss F 90 and Rodenstock L 660. RESULTS: Patients with retinitis pigmentosa showed an increase of contrast sensitivity with all three cut-off filters. This was statistically significant at a spatial frequency of 1.5 cycl/deg (P < 0.027), but not for higher frequencies of 6-18 cycl/deg (P < 0.5). The healthy volunteers did not show any increase in contrast sensitivity values with cut-off filters. CONCLUSION: Evaluating contrast sensitivity at high levels of luminance is useful to identify patients who benefit from cut-off filters. All RP patients subjectively preferred to wear cut-off filters. A statistically proven beneficial effect of cut-off glasses could be found for low spatial frequencies. An individual fitting of the various types of cut-off filters is inevitable.

Adolescent↗
PubMed1991

Binocular contrast sensitivity testing for low vision patients.

Contrast sensitivity testing is often included in primary care and low vision examinations. This test is designed to provide information regarding the quality of a patient's vision. This clinical study provides a method to assess the binocularity of a low vision patient with contrast sensitivity testing. The method allows the practitioner to determine if monocular or binocular conditions are optimal for the use of a near low-vision device.

Adult↗
PubMed1996

Retinal illuminance and contrast sensitivity in human infants.

Several investigators have related infants' low contrast sensitivity to immaturities in the optics and receptor lattice of the immature eye. A critical element in the modeling is how much the lower photon catch of the immature retina reduces sensitivity; the assumptions vary from square-root to Weber's law and lead to very different modeling outcomes. We measured the relationship between retinal illuminance and contrast sensitivity at different spatial frequencies. The sweep visual-evoked potential was used to measure thresholds in 2- and 3-month olds and adults over a 2.5-log-unit range of illuminances. The contrast threshold vs illuminance functions were fit by power functions. The best-fitting exponents for adults were about -0.5 at higher spatial frequencies (consistent with square-root law) and lower at lower frequencies. The best-fitting exponents for 2- and 3-month olds were -0.2 to -0.35 which indicates that threshold is less affected by changes in illuminance than is the case in adults. These results suggest that none of the models relating optical and receptoral immaturities to infants' spatial vision has assumed an appropriate relationship between lower photon catch and contrast sensitivity. Once the models are modified to incorporate the relationship obtained in the present experiment, the predictions fall well short of explaining 2-month olds' low contrast sensitivity.

Adult↗
PubMed1989

Contrast sensitivity versus static visual field testing during experimental elevation of intraocular pressure.

Contrast sensitivity testing has been recommended as a more sensitive indicator of early visual loss than visual field testing. Using gravity inversion to induce an intraocular pressure rise, we performed contrast sensitivity testing on each eye of 10 normal subjects in the upright and inverted positions. Contrast sensitivity results were not altered in the head-down position, even though in 5 of the 10 subjects (7 of 20 eyes), visual field alterations on static perimetry were elicited during inversion. In both of these evaluations, the subject's results in the upright position served as the control, freeing us from reliance upon age-matched populations. We conclude that precise measurement of static thresholds with automated perimetry is more sensitive than routine contrast sensitivity testing in detecting visual dysfunction related to transient acute elevations of intraocular pressure.

Adult↗
PubMed1978

Contrast sensitivity function for stereopsis.

Contrast thresholds for stereopsis from narrow-band-filtered random-dot stereograms were compared with contrast thresholds for simple detection of similar narrow-band noise. Centre frequencies of filters were in the range 2.5--15 cycles deg(-1). It was found that the contrast sensitivity function for stereopsis is similar in shape to that for detection, suggesting that as far as contrast requirements are concerned the mechanisms of global stereopsis do not show a bias in sensitivity to any particular spatial frequency but instead require a constant level of suprathreshold contrast regardless of spatial frequency.

Depth Perception↗
PubMed1999

[The evaluation of contrast sensitivity in children and adolescents with insulin-dependent diabetes mellitus].

PURPOSE: The evaluation of contrast sensitivity in children and adolescents with type I diabetes mellitus with and without retinopathy, taking into account metabolic control. MATERIAL AND METHODS: We examined 100 young patients (71 without retinopathy and 29 with background retinopathy on fluorescein angiography) and 60 control non-diabetic subjects matched for age and sex, without visual or systemic symptoms. Contrast sensitivity was measured in spatial frequency of 3, 6, 12 and 18 cycles/degree (c/d). RESULTS: Contrast sensitivity was significantly lower (p < 0.001) in four spatial frequencies in all diabetic patients and in IDDM patients without retinopathy than in control group. Patients with IDDM and retinopathy had abnormal contrast sensitivity at spatial frequency 18 c/d when compared with patients without retinopathy. There was no correlation between contrast sensitivity and HbA1c values. CONCLUSIONS: Contrast sensitivity measurement in children and adolescents with type I diabetes is useful in the evaluation of the nature of early abnormalities in retinal function of diabetics.

Adolescent↗
PubMed1991

Reduced contrast sensitivity when viewing through an aircraft windscreen.

The Contrast Sensitivity Function (CSF) of an experienced observer was measured under normal viewing conditions, when looking through an aircraft windscreen and when looking through the windscreen in the presence of a glare source. We found that contrast sensitivity was significantly reduced for frequencies above about 6 cycles/degree viewed through the windscreen and that the addition of a glare source further reduced contrast sensitivity for all spatial frequencies greater than 1 cycle/degree. These results demonstrate that the CSF is a sensitive metric of degraded visual performance when viewing through optical transparencies.

Aerospace Medicine↗
PubMed1993

Contrast sensitivity for the stationary and drifting vertical stripe patterns in patients with optic nerve disorders.

Subjective contrast sensitivity for the stationary and horizontally drifting vertical stripe patterns was measured in normal subjects and in patients with glaucoma, optic neuritis and optic atrophy. Contrast sensitivity was also determined objectively using an eye movement reflex (optokinetic nystagmus) recorded by means of electro-oculography. The contrast sensitivity for the drifting stripe patterns in normal subjects was characterized by a depression of sensitivity at the high spatial frequency and an increased contrast sensitivity at the low spatial frequency in comparison with the results of stationary stripe patterns. The measurement of contrast sensitivity for the horizontally drifting vertical stripe patterns was found to be more sensitive for detection of minor damage to the optic nerve than that for the stationary patterns. The results of the subjective contrast sensitivity and the objective one determined using an eye movement reflex showed a good correlation.

Adolescent↗
PubMed1995

Visual acuity vs letter contrast sensitivity in retinitis pigmentosa.

This study examined the quantitative relationship between foveal visual acuity and contrast sensitivity for large-letter optotypes in a group of patients with retinitis pigmentosa (RP), in order to assess more completely the extent of foveal vision loss in this group of hereditary retinal dystrophies. High-contrast visual acuity and large-letter contrast sensitivity were measured with a computer-based testing system and with commercially available letter charts (Lighthouse Distance Visual Acuity Test; Pelli-Robson Contrast Sensitivity Chart). Findings from 20 patients with typical RP or Usher syndrome were compared with those from 15 age-similar control subjects with normal vision. On both the computer-based test and the chart tests, the patients with RP showed approximately equal reductions in visual acuity and large-letter contrast sensitivity. However, intersubject controls was greater for contrast sensitivity than for visual acuity on both test protocols. As a result, the patients with RP required a greater reduction in contrast sensitivity than in acuity to exceed the normal range, indicating that visual acuity was the more sensitive index of the loss of foveal visual function.

Adult↗
PubMed2004

Comparison of angular frequency contrast sensitivity in young and older adults.

The aim of the present study was to measure contrast sensitivity curves for angular frequencies in the range between 2 and 96 cycles/360 masculine in older human adult volunteers and to compare these measurements with the more usual contrast sensitivity functions for sine-wave gratings. All subjects were free of identifiable ocular disease and had normal acuity. We measured the contrast thresholds for young adults (N=6; age range, 20-26 years) and older adults (N=6; age range, 60-67 years) using the psychophysical forced-choice method. In this paradigm the volunteers had to choose the stimulus containing a test frequency at low contrast (e.g., either a sine-wave grating or an angular frequency stimulus), or another neutral stimulus at mean luminance (without any contrast). Older adults presented a loss in contrast sensitivity at high and medium angular frequencies compared to the young adults (i.e., from 8 to 96 cycles/360 degrees). Contrary to expectation, contrast sensitivity at low angular frequencies, i.e., 2 and 4 cycles/360 degrees, was better for the older group than for the younger group. On the other hand, contrast sensitivity for sine-wave gratings at 3 and 4 cpd was higher for young adults as expected. These results suggest age-related changes in the contrast sensitivity function for angular frequencies.

Adult↗
PubMed1996

Selective broad-band spatial frequency loss in contrast sensitivity functions. Comparison with a model based on optical transfer functions.

PURPOSE: Contrast sensitivity functions (CSFs) were measured under various optical conditions in healthy observers together with CSFs from selected patients. Threshold increases across the spatial frequency range were compared with predictions of a theoretical optical model based on modulation transfer functions. METHODS: Contrast thresholds for various spatial frequencies were determined with a computer-automated method of ascending limits in a control group and a group of patients with various visual pathway diseases ranging from retinal disorders, such as diabetic retinopathy, to neural disorders, such as multiple sclerosis. For normal control subjects, simulated contrast sensitivity losses also were effected by manipulating pupil diameter and dioptric blur. Modulation transfer functions of the eye's optics in polychromatic light were calculated. The wave aberration function included standard spherical aberration, coma, and small amounts of irregular aberrations. RESULTS: Experimentally, slight dioptric blur (e.g., 0.4 to 0.75 D) introduced increased CSF thresholds within either a narrow or broad bandwidth. For the latter, decreased CSF sensitivity occurred across a spatial frequency range as broad as 1 log unit, from low spatial frequencies (2 cyc/deg), and for pupil sizes equal to or larger than 3 mm. Predictions based on an optical model are qualitatively and quantitatively in agreement with these findings. Contrast sensitivity losses of the patients were neither specific nor selective to the pathologic condition at hand. Furthermore, various CSF losses optically induced in the control subjects were indistinguishable from nonoptically induced pathologic CSF profiles. CONCLUSIONS: Selective broad-band contrast sensitivity loss may be optically induced by slight refractive error. As a result, selective contrast sensitivity loss at lower and intermediate spatial frequencies concurrent in patients with various pathologic, neuro-ophthalmologic conditions cannot be a priori attributed to neural factors without carefully controlled and well-defined optical variables.

Adult↗
PubMed2003

The ability of periorbitally applied antiglare products to improve contrast sensitivity in conditions of sunlight exposure.

BACKGROUND: Sun glare decreases athletes' contrast sensitivity and impairs their ability to distinguish objects from background. Many commercial products claim to reduce glare but have not been proven effective in clinical studies. OBJECTIVE: To determine whether glare-reducing products such as eye black grease and antiglare stickers reduce glare and improve contrast sensitivity during sunlight exposure. DESIGN AND METHODS: We tested 46 subjects for contrast sensitivity using a Pelli-Robson contrast chart. Each subject served as an internal control and then was randomized to either application of eye black grease, antiglare stickers, or petroleum jelly at the infraorbital rim. All testing was performed in conditions of unobstructed sunlight. RESULTS: Analysis of variance revealed a significant difference between eye black grease (mean +/- SD, Pelli-Robson value, 1.87 +/- 0.09 logMAR units) and antiglare stickers (1.75 +/- 0.14 logMAR units) in binocular testing (P =.02). No statistical difference was found between the groups in right eyes, left eyes, or in combined data from the right and left eyes. Paired t tests demonstrated a significant difference between control (mean +/- SD, 1.77 +/- 0.14 logMAR units) and eye black grease (1.87 +/- 0.09 logMAR units) in binocular testing (P =.04). There was also a significant difference between control (mean +/- SD, 1.65 +/- 0.05 logMAR units) and eye black grease (1.67 +/- 0.06 logMAR units) in combined data from the right and left eyes (P =.02). CONCLUSION: Eye black grease reduces glare and improves contrast sensitivity in conditions of sunlight exposure compared with the control and antiglare stickers in binocular testing.

Adolescent↗
PubMed2006

A "bright zone" in male hoverfly (Eristalis tenax) eyes and associated faster motion detection and increased contrast sensitivity.

Eyes of the hoverfly Eristalis tenax are sexually dimorphic such that males have a fronto-dorsal region of large facets. In contrast to other large flies in which large facets are associated with a decreased interommatidial angle to form a dorsal "acute zone" of increased spatial resolution, we show that a dorsal region of large facets in males appears to form a "bright zone" of increased light capture without substantially increased spatial resolution. Theoretically, more light allows for increased performance in tasks such as motion detection. To determine the effect of the bright zone on motion detection, local properties of wide field motion detecting neurons were investigated using localized sinusoidal gratings. The pattern of local preferred directions of one class of these cells, the HS cells, in Eristalis is similar to that reported for the blowfly Calliphora. The bright zone seems to contribute to local contrast sensitivity; high contrast sensitivity exists in portions of the receptive field served by large diameter facet lenses of males and is not observed in females. Finally, temporal frequency tuning is also significantly faster in this frontal portion of the world, particularly in males, where it overcompensates for the higher spatial-frequency tuning and shifts the predicted local velocity optimum to higher speeds. These results indicate that increased retinal illuminance due to the bright zone of males is used to enhance contrast sensitivity and speed motion detector responses. Additionally, local neural properties vary across the visual world in a way not expected if HS cells serve purely as matched filters to measure yaw-induced visual motion.

Animals↗