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PubMed2000

Contrast sensitivity evaluation after laser in situ keratomileusis.

OBJECTIVE: To determine the effects of laser in situ keratomileusis (LASIK) on best-corrected visual acuity (BCVA) and contrast sensitivity. DESIGN: Prospective, observational case series. PARTICIPANTS: One hundred twelve eyes, in 65 patients with myopia and myopia with astigmatism, who underwent LASIK. TESTING AND MAIN OUTCOME MEASURES: Best-corrected visual acuity using the Snellen visual acuity chart and contrast sensitivity using the CSV 1000 (Vector Vision, Dayton OH) was tested before surgery and 1 week, 1 month, and 3 months after surgery in patients who underwent LASIK. RESULTS: Contrast sensitivity was depressed for patient eyes with spherical equivalence (SE) between -1.25 diopters (D) and -13.75 D, at 12 cycles/degree for at least 3 months and at 18 cycles/degree for 1 week after LASIK. For patient eyes with SE between -1.25 D and -6.00 D, contrast sensitivity was depressed only at 12 cycles/degree for at least 3 months after LASIK. For patient eyes with SE between -6.00 D and -13.75 D, contrast sensitivity was depressed at 6, 12, and 18 cycles/degree 1 week after LASIK but returned toward preoperative levels by 1 month after surgery. Despite the slight decreases in contrast sensitivity, all scores were still within the range of normal values except for 12 cycles/degree for 3 months and 18 cycles/degree at 1 week after surgery in the high myopia group. Although highly myopic patients, compared with patients with low myopia, had slightly less BCVA before surgery, both groups maintained their preoperative BCVA at all postoperative visits. CONCLUSIONS: Based on this study, we conclude that LASIK has little effect on BCVA and contrast sensitivity for up to 3 months after surgery.

Adult↗
PubMed1993

[The variation of human contrast sensitivity with age and optic nerve disease].

Contrast sensitivity function (CSF) was measured in 85 normal subjects and in 23 patients with optic neuropathy, using a personal computer and video monitor system. CSF in normal controls showed an inverted U-shaped function against spatial frequency with a peak at about 4-6 cycles/degree. At higher spatial frequencies, contrast sensitivity decreased with increasing age. CSF in patients was compared with Snellen acuity, visual field examination, critical flicker fusion frequency (CFF) and pattern VEP (P-VEP). CSF and P-VEP were more sensitive than the others in detecting visual dysfunction in optic nerve disease. These results suggest that ranges of normal values should be established for each of several age groups, and that CSF is useful for evaluating visual dysfunction.

Adult↗
PubMed2004

Contrast sensitivity through hybrid diffractive, Fresnel, and refractive prisms.

BACKGROUND: Fresnel and wedge-shaped refractive prisms are used diagnostically and therapeutically in clinical practice. This article extends the study on the effect of prisms on visual acuity to the effect on contrast sensitivity by membrane Fresnel (F), refractive (R), and newly designed hybrid diffractive (C) prisms (ComPrisms), which combine a wedge-shaped refractive prism with a diffractive element. METHODS: Vistech contrast sensitivity function (CSF) Charts A, B, and C were used to measure the monocular and binocular contrast sensitivity of 21 and 20 subjects, respectively. CSF was measured without prisms (U), through the hybrid diffractive prisms, membrane Fresnel prisms, and acrylic refractive prisms in powers of 20delta, 30delta, and 40delta. RESULTS: Repeated measures analysis of variance calculations resulted in significant main effects in contrast sensitivity across prism types, prism powers, and between monocular and binocular measurements. Results of the Scheffé test for all possible contrast sensitivity comparisons between spatial frequencies are provided. It was found that as prism power increased from 20delta to 40delta, the rate of reduction in area under the CSF curve of ComPrisms became half that of the refractive and Fresnel prisms. CONCLUSIONS: Although all three prism types reduced contrast sensitivity with respect to the unaided condition, the ComPrisms at all powers provided significantly better contrast sensitivity than the refractive or Fresnel prisms of equivalent power. Significant binocular summations in contrast sensitivity were found without prisms and across all prism types and powers.

Adult↗
PubMed1993

Contrast sensitivity dysfunction in Alzheimer's disease.

We compared the spatial contrast sensitivity of six patients with mild to moderate Alzheimer's disease (AD) and six age-matched control subjects in a parametric design. Results demonstrate reduced contrast sensitivity in patients with AD at all but the lowest frequency tested. The results suggest that the effect of AD on spatial contrast sensitivity is stronger at higher frequencies and provide a rationale for complaints of poor vision in AD patients.

Aged↗
PubMedDate not supplied

The relationship between anterior corneal aberrations and contrast sensitivity in conventional LASIK.

PURPOSE: To evaluate the changes of anterior corneal aberrations before and after laser in situ keratomileusis (LASIK) and to assess the correlation between contrast sensitivity and anterior corneal aberrations. METHODS: Right eyes of 51 patients including 6 males and 45 females undergoing conventional LASIK from September 2000 to July 2003 were enrolled. The calculation of anterior corneal aberrations before and after LASIK was obtained by analyzing the corneal topography from TMS-1 by using VOL-CT Version 6.23 software. Contrast sensitivity was measured after LASIK with an MCT 8000 under daytime and nighttime settings and with glare conditions. The differences of the Zernike coefficients and root mean square (RMS) of anterior corneal aberrations before and after LASIK were analyzed. The changes of contrast sensitivity at 1.5, 3, 6, 12, and 18 cpd were added separately for daytime and nighttime contrast sensitivity with and without glare after LASIK and were correlated with the changes of anterior corneal aberrations. RESULTS: Vertical coma, RMS of coma-like RMS of spherical-like, RMS of trefoil-like and RMS of higher-order anterior corneal aberrations increased significantly after LASIK surgery. There were no significant correlations between the changes of anterior corneal aberrations and the changes of contrast sensitivity at daytime and nighttime, with and without glare. Contrast sensitivity at daytime and nighttime decreased at each spatial frequency after LASIK. CONCLUSIONS: LASIK surgery induces changes of the anterior corneal aberrations. However, changes in anterior corneal aberrations did not correlate with the changes of contrast sensitivity at daytime and nighttime, with and without glare.

Adult↗
PubMedDate not supplied

A comparative study for mesopic contrast sensitivity between photorefractive keratectomy and laser in situ keratomileusis.

BACKGROUND AND OBJECTIVE: To compare the effect on visual performance of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with mesopic contrast sensitivity. PATIENTS AND METHODS: Postoperative visual performance for 40 eyes undergoing PRK and 40 eyes undergoing LASIK was compared with mesopic contrast sensitivity at 1, 3, and 6 months postoperatively. Eyes were divided into two groups (< -6.0 D and > -6.25 D). Mesopic contrast sensitivity was performed with the patient's best-corrected visual acuity of 20/20 or better under photopic conditions. RESULTS: A significant decrease in mesopic contrast sensitivity from preoperative baseline was obtained at all spatial frequencies for the PRK and LASIK groups (P < .05). There was no statistically significant difference at 1 or 3 months postoperatively in both groups (P > .05). At 6 months postoperatively, LASIK significantly decreased mesopic contrast sensitivity more than PRK in myopia with a refractive error of less than -6.0 D, especially at the middle and high spatial frequencies of 6, 9, and 12 cycles per degree (P < .05). However, no statistically significant differences in mesopic contrast sensitivity between PRK and LASIK were found in myopia with a refractive error of greater than -6.25 D (P > .05). CONCLUSIONS: In broad-beam excimer laser refractive surgery, PRK seemed to have a more significant effect on mesopic contrast sensitivity than LASIK for myopia with a refractive error of less than -6.0 D at 6 months postoperatively.

Adult↗
PubMed1983

Effects of amblyopia therapy on contrast sensitivity as reflected in the visuogram.

A quantitative evaluation of the Cambridge amblyopia treatment on contrast sensitivity was performed for 2 groups, one comprising 11 children with strabismic amblyopia (S) and another of 10 children with combined strabismic and anisometropic amblyopia (S & A). Contrast sensitivity deficits were expressed in dB CSL (Contrast Seeing Level) in relation to normal sensitivity of the same age group and represented in the form of visuograms. Mean contrast sensitivity losses in dB CSL were estimated within the low, medium and high spatial frequency ranges, as well as over the total frequency band. On an average S & A amblyopia was found to affect contrast sensitivity of all spatial frequencies, while S amblyopia affected mainly the higher frequency band, but to a smaller extent. After therapy average contrast sensitivity improved for both S and S & A groups, and reached the same, subnormal levels. The relation between highest resolvable spatial frequency (according to our method) and Snellen acuity was different for the 2 amblyopia groups. No correlation was found between improvements in contrast sensitivity and Snellen acuity, which is why both parameters should be estimated.

Adolescent↗
PubMed1989

Using argon laser blue light reduces ophthalmologists' color contrast sensitivity. Argon blue and surgeons' vision.

Color contrast sensitivity was measured in laser operators before and after laser use. After argon blue-green laser treatment sessions, sensitivity was reduced for colors lying along a tritan color-confusion line for several hours. This acute effect is due to specular "flash-backs" from the aiming beam off the surface of the contact lens. It is caused only by argon 488-nm light, when the aiming beam intensity is high. In addition, a correlation has been demonstrated between the number of years of laser experience and a chronic reduction in tritan color contrast sensitivity. It is suggested that repeated acute changes caused by the argon lasers may cause cumulative effects and produce a chronic threshold elevation. A simple method of eliminating the acute effect is documented.

Adult↗
PubMed1997

Contrast sensitivity measurement in evaluations of visual symptoms caused by exposure to triethylamine.

OBJECTIVES: To determine whether blurred vision caused by exposure to triethylamine (TEA) can be detected by the measurement of contrast sensitivity. METHODS: 41 cold box core makers of three foundries and 82 control workers were examined. A detailed ocular and medical history was obtained from the subjects. The contrast sensitivity of the core makers was measured on Monday and Friday of the same week both before and immediately after work and also on a third day, when air samples of TEA were collected. Contrast sensitivity and visual acuity were measured by optotype figures at full contrast, 2.5% contrast, and 0.6% contrast. The changes in contrast sensitivity were used for the analysis. The results of binocular vision and the results of the dominant eye were analysed. Urine specimens for the analysis of TEA were collected on every occasion when contrast sensitivity was measured. RESULTS: 78% of the core makers had had symptoms of blurred vision, and 31% had had trouble driving or working. The breathing zone eight hour time weighted average TEA concentrations were 0.3-60 mg/m3. The mean urinary TEA concentration after the shift was 35 mmol/mol creatinine. Continuous monitoring showed high peaks of TEA leakage at a core making machine. Changes in binocular visual acuity did not differ between the exposed and unexposed workers. The contrast sensitivity decreased in 49% of the core makers and 21% of the controls (P = 0.002). CONCLUSIONS: The blurred vision caused by exposure to TEA can be documented by measuring contrast sensitivity. The mechanism by which TEA produces symptoms remains an issue of further study.

Adolescent↗
PubMed1999

Noise and its effects on photoreceptor temporal contrast sensitivity at low light levels.

We studied photoreceptors in the locust (Schistocerca americanus) visual system to determine the extent to which quantal noise and intrinsic neural noise limit temporal sensitivity. Typical computational models of the temporal contrast sensitivity function are deterministic, reflect only filter characteristics, and lack explicit noise sources [J. Opt. Soc. Am. 58, 1133 (1968); Vision Res. 32, 1373 (1992)]. We report here that the temporal contrast sensitivity function, at low light levels, is not simply the reflection of a filter function. Our evidence suggests that, at low backgrounds, noise, in conjunction with temporal filtering, plays a role in shaping the temporal contrast sensitivity function. At a given low adaptation level, quantal noise limits sensitivity at low temporal frequencies, while intrinsic noise limits sensitivity at relatively higher temporal frequencies.

Animals↗
PubMed2001

Visual acuity and contrast sensitivity in different types of posterior capsule opacification.

PURPOSE: To compare the visual acuity (VA) and contrast sensitivity in 2 types of posterior capsule opacification (PCO) in pseudophakic eyes before and after neodymium:YAG (Nd:YAG) capsulotomy and to evaluate vision test results after Nd:YAG capsulotomy. SETTING: Department of Ophthalmology, Taipei Veterans General Hospital, National Yang-Ming University, Taipei, Taiwan. METHODS: Fourteen eyes with fibrosis-type PCO and 15 eyes with Elschnig-pearl-type PCO were enrolled prospectively. Before and 1 week after Nd:YAG capsulotomy, VA and contrast sensitivity were assessed using the illiterate E version of the Bailey-Lovie chart and the Vistech VCTS 6000 chart, respectively. RESULTS: Before capsulotomy, the mean logMAR acuity in the group with Elschnig-pearl-type PCO was 0.47 +/- 0.32 (SD) and in the group with fibrosis-type PCO, 0.17 +/- 0.07. The difference between the 2 groups was significant (P =.002). After capsulotomy, there was no significant between-group difference (P >.05). Before capsulotomy, the contrast sensitivity was significantly worse (P <.01) at all spatial frequencies in the group with pearl-type PCO, especially at 6 cycles per degree. After capsulotomy, there was no significant between-group difference (P >.05) at any spatial frequency. CONCLUSIONS: After cataract surgery, patients with pearl-type PCO had lower VA and contrast sensitivity than those with fibrosis-type PCO. An Nd:YAG capsulotomy improved the VA and contrast sensitivity in patients with both types of PCO.

Aged↗
PubMed2000

The full-field temporal contrast sensitivity test for glaucoma: influence of cataract.

PURPOSE: To determine the influence of lens opacities on temporal contrast sensitivity, measured by the full-field flicker test ("Erlangen flicker test"). METHODS: Thirty-six consecutive patients (mean age 71.1+/-11.6 years, 12 male, 24 female, refractive error -1.5+/-3.8 dpt) with cataract (visual acuity 0.21+/-0.16, retinal acuity 0.56+/-0.32, no glaucoma) were studied. Temporal contrast sensitivity (full-field flicker test, 37.1 Hz) and lens opacity (back scatter Lens Opacity Meter, Interzeag) were measured preoperatively and on the 3rd postoperative day. STATISTICS: nonparametric tests (Wilcoxon-test, Spearman correlation coefficient, Mann-Whitney U-test). RESULTS: No significant difference was seen in temporal contrast sensitivity pre- and postoperatively, but there was a significant difference in lens opacity measurements pre- and postoperatively. No significant correlation was found between temporal contrast sensitivity and lens opacity values preoperatively and postoperatively. CONCLUSION: The temporal contrast sensitivity, measured by the full-field flicker test, seems to be independent of lens opacity due to the range of cataract included in this study. The data indicate that the full-field flicker test is useful for early glaucoma detection even in patients with cataract formations.

Aged↗
PubMed1993

Correlation of spatial contrast sensitivity and visual fields in glaucoma.

Perimetry is the standard examination in glaucoma, whereas contrast sensitivity is often proposed as a complementary test. This study investigates the extent to which the outcomes of the two tests correlate. One eye each of 44 glaucoma patients and 16 glaucoma suspects was tested with the Haag-Streit Visometer and the Octopus 201 perimeter (program G1). Contrast sensitivities correlated highest with the center of the visual field (Spearman's rho = 0.76; P < 0.001) and slightly less with the mean sensitivity of the entire visual field (rho = 0.63; P < 0.001). Mean contrast sensitivity correlated weakly with the square root of corrected loss variance (rho = -0.45; P < 0.001) and short-term fluctuation (rho = -0.34; P < 0.007). The two tests differed considerably only in very few patients. We recommend careful evaluation of the central area of glaucomatous visual fields whenever contrast sensitivity testing is not available.

Contrast Sensitivity↗
PubMed1992

Infant temporal contrast sensitivity at low temporal frequencies.

The data on infant temporal contrast sensitivity functions (TCSFs) are scarce and contradictory. Earlier studies suggest that critical flicker frequency (CFF) is adultlike at 2-3 months postnatal (Regal, D. M., 1981 Vision Research, 21, 549-555), while contrast sensitivity at low temporal frequencies remains poor. If both of these findings are true, then infant TCSFs are much flatter than those of adults. In the present study, we have re-investigated 2-month-olds' contrast thresholds at low temporal frequencies. To match the conditions of Regal's CFF study, test fields were embedded in a luminance-matched surround. As in previous studies, low contrast sensitivities were found. Models of infants' flat TCSFs are discussed.

Contrast Sensitivity↗
PubMed1988

The relationship between hue discrimination and contrast sensitivity deficits in patients with diabetes mellitus.

In an attempt to elucidate more fully the pathophysiologic basis of early visual dysfunction in patients with diabetes mellitus, color vision (hue discrimination) and spatial resolution (contrast sensitivity) were tested in diabetic patients with little or no retinopathy (n = 57) and age-matched visual normals (n = 35). Some evidence of visual dysfunction was observed in 37.8% of the diabetics with no retinopathy and 60.0% of the diabetics with background retinopathy. Although significant hue discrimination and contrast sensitivity deficits were observed in both groups of diabetic patients, contrast sensitivity was abnormal more frequently than hue discrimination. However, only 5.4% of the diabetics with no retinopathy and 10.0% of the diabetics with background retinopathy exhibited both abnormal hue discrimination and abnormal contrast sensitivity. Contrary to previous reports, blue-yellow (B-Y) and red-green (R-G) hue discrimination deficits were observed with approximately equal frequency. In the diabetic group, contrast sensitivity was reduced at all spatial frequencies tested, but for individual diabetic patients, significant deficits were only evident for the mid-range spatial frequencies. Among diabetic patients, the hue discrimination deficits, but not the contrast sensitivity abnormalities, were correlated with the patients' hemoglobin A1 level. A negative correlation between contrast sensitivity at 6.0 cpd and the duration of diabetes also was observed.

Adult↗
PubMed1996

Development of contrast sensitivity across the visual field in macaque monkeys (Macaca nemestrina).

Interpretation of measurements of visual performance in infants must be based on knowledge of the locus of highest sensitivity in the infant retina. While we know that adult contrast sensitivity and spatial resolution is highest at the fovea, recent anatomical data show that the infant fovea is relatively immature. We have studied that variation of contrast sensitivity across the visual field during development in infant monkeys in order to investigate the behavioral consequences of this immaturity. The results show that, unlike adults, the sensitivity of the infant foveal region is similar to that of the near periphery. Central contrast sensitivity and spatial resolution improve substantially relative to the periphery over the first 20-40 postnatal weeks. Thus, contrast sensitivity in the periphery is relatively mature in infants with respect to more central regions of the visual field. The maturation pattern seen behaviorally is consistent with physiological and anatomical maturation patterns in macaque monkey.

Aging↗
PubMed1996

[Spatial contrast sensitivity in patients with severe myopia].

PURPOSE: The purpose of this study was to assess the effects of amount of myopia, axial elongation staphyloma and type of optical correction on contrast sensitivity of high myopic subjects. METHODS: Fifty-one patients (91 eyes) were selected on the following qualifications: myopia > or = 8 dpt and/or axial length > or = 26 mm, and visual acuity > or = 0.1 recorded through spectacle lenses. Contrast sensitivity was measured using a "Moniteur Ophtalmologique" for all subjects when corrected with spectacle lenses, and thereafter on a lot of patients (50 eyes) wearing a contact lens. RESULTS: Contrast sensitivity obtained with spectacle lenses was significantly decreased over the whole spatial frequency range. The higher the spatial frequency was, the lower contrast sensitivity was. The impairment increased with the amount of myopia and axial length, but without positive correlation. Contrast sensitivity was significantly lower for only the three highest spatial frequencies measured (6.4; 12.8 and 25.6 c/deg), when a staphyloma (n = 52) was present by comparison with results obtained for eyes without staphyloma (n = 39). Differences between the two situations (spectacle lens vs. contact lens) were not significant for eyes wearing daily spectacle lenses; conversely, for myopic subjects generally fitted with contact lenses, contrast sensitivity with contact lenses was significantly better than that measured with spectacles for the three highest spatial frequencies tested. CONCLUSION: This suggests that the decrease in contrast sensitivity measured in high myopia is related to defects in the optical and neuro-retinal systems.

Adult↗
PubMed2000

Contrast sensitivity measured by 2 methods after photorefractive keratectomy.

PURPOSE: To study contrast sensitivity in eyes that had flying-spot excimer laser photorefractive keratectomy (PRK) and to compare a subjective method (Vision Contrast Test System [VCTS] 6500) and an objective method (visual evoked potential [VEP]) of measuring contrast sensitivity. SETTING: Istituto Clinica Oculistica, Università degli Studi, Bari, Italy. METHODS: Contrast sensitivity changes over time were evaluated in 26 eyes. The baseline values were compared with measurements 3, 6, and 12 months after PRK using the VCTS 6500 and VEP. Contrast threshold and VEP amplitude were classified by myopic correction. RESULTS: Contrast threshold values changed significantly over time (P <.001). Significant differences were found between mean contrast threshold preoperatively and 12 months postoperatively (P <.001) at all spatial frequencies. A significant relationship was established between baseline and 12 month measurements at 18 cycles per degree. Mean VEP amplitude measurements also changed significantly over time (P <.001) and showed a significant relationship between baseline and 12 month measurements (P <.001). A significant relationship was also established between baseline and 12 month VEP amplitude values at 100% of grating contrast. Patients with high myopia complained significantly more at a lower contrast threshold and at lower VEP amplitude values than patients with low myopia. CONCLUSIONS: Three months after PRK, contrast threshold and VEP amplitude values were reduced. Partial recovery was established at 6 months, although patients reported permanent impairment under low-contrast conditions, especially if the myopia correction was more than 6.0 diopters.

Adult↗