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PubMed2002

Enhancement of contrast sensitivity and losses of chromatic discrimination with tinted lenses.

PURPOSE: Tinted lenses for everyday use should not impair visual acuity and contrast sensitivity or cause radical changes in color perception. The main aim of this study was to compare the performance in contrast detection and color discrimination tasks of a set of tinted lenses with that of gray filters of equal luminance under D65. METHODS: The contrast sensitivity functions of 10 observers were measured using sinusoidal gratings of mean luminance of 13 cd/m2 by the adjustment method. Color discrimination thresholds from white (x = 0.313, y = 0.330), green (x = 0.346, y = 0.407), and blue (x = 0.280, y = 0.253) were measured along 12 directions in the CIE-1931 xy diagram with and without lenses. RESULTS: Green, brown, and blue filters did not cause significant changes in contrast sensitivity compared with a gray filter of equal luminance, although chromatic discrimination was disturbed. Yellow and orange filters improved achromatic contrast at certain spatial frequencies, but impaired chromatic discrimination. CONCLUSIONS: Compared with gray filters of the same luminance, yellow filters may be useful when enhancement of low achromatic contrasts is desirable, although overall brightness decrements may occur. Nevertheless, these lenses cause tritan-like defects with discrimination losses increasing with the cutoff wavelength.

Accommodation, Ocular↗
PubMed2002

The contrast sensitivity function for detection and resolution of blue-on-yellow gratings in foveal and peripheral vision.

Previous studies using polychromatic gratings have shown that the peripheral grating contrast sensitivity function is significantly different when the task is resolution rather than detection. Specifically, in the middle frequency range, while resolution acuity drops suddenly to zero, detection performance continues up to much higher frequencies, accompanied by observations of aliasing. We wanted to determine if the same holds true for blue-cone isolating gratings in either foveal or peripheral vision. Contrast sensitivity function (CSFs) were measured at the fovea and 20 degrees eccentricity in the temporal retina under conditions of short-wavelength-sensitive (SWS)-cone pathway isolation using a two-alternative forced choice paradigm. The detection and resolution CSF were identical at the low frequency end but at higher frequencies resolution sensitivity falls abruptly while contrast detection remained possible till higher frequencies [cut-off frequencies: fovea detection 6.0 cycles (degree)(-1), resolution 4.6 cycles (degree)(-1); periphery detection 1.6 cycles (degree)(-1), resolution 1.05 cycles (degree)(-1)]. Aliasing was observable when spatial frequency exceeded the resolution limit. Medium/high contrast blue-cone-mediated resolution acuity is sampling limited in both the fovea and periphery. Previous studies of blue-cone contrast sensitivity which employed a detection task do not reflect the true resolution limit.

Color Perception↗
PubMed1991

Visual acuity and contrast sensitivity in cataract: summation and inhibition of visual performance.

Patients exhibiting uniocular cataract often report an improvement in vision on closing their cataractous eye. Such qualitative evidence suggests the presence of binocular inhibition--the converse of binocular summation (that is the normal superiority of binocular over monocular vision). To quantify the extent of inhibition in cataract, binocular and monocular visual acuity and contrast sensitivity were measured in 28 patients. Twelve patients showed binocular inhibition for visual acuity whilst 11 showed inhibition for contrast sensitivity measured at four cycles per degree (c.deg-1). Contrast sensitivity for 8 c.deg-1 targets was further recorded in a subset of 14 patients in whom seven showed inhibition. In patients who demonstrated inhibition, the mean decrement in performance for visual acuity was 13%. For contrast sensitivity at 4 and 8 c.deg-1 the mean decrement was 25% and 32% respectively. The clinical significance of these findings is discussed with respect to the assessment of visual function and management of the cataract patient.

Adult↗
PubMed2002

No sex differences in contrast sensitivity and reaction time to spatial frequency.

This study investigated the possibility of sex differences in spatial frequency processing by measuring contrast sensitivity and reaction time to spatial frequency in the same 20 men and 20 women. This is the first study to investigate sex differences in reaction time to spatial frequency and the first to study sex differences in contrast sensitivity and reaction time within the same participants. No sex differences were found in either contrast sensitivity or reaction time measures, suggesting that women and men process spatial frequency information similarly.

Adolescent↗
PubMed2006

Spherical aberration and contrast sensitivity after cataract surgery with the Tecnis Z9000 intraocular lens.

PURPOSE: To determine whether implantation of an intraocular lens (IOL) with a modified prolate anterior surface (Tecnis Z9000, AMO) results in reduced spherical aberration and improved contrast sensitivity after cataract surgery. SETTING: Hospital NISA Virgen del Consuelo, Valencia, Spain. METHODS: In an intraindividual randomized prospective study of 30 patients with bilateral cataract, the Tecnis Z9000 IOL was compared with 2 IOLs with spherical surfaces, the AR40e (AMO) and the Stabibag (Ioltech). Ocular aberrations for a 4.0 mm pupil and 6.0 mm pupil were measured with a Hartmann-Shack aberrometer. Quality of vision was measured by visual acuity and contrast sensitivity under mesopic and photopic conditions. RESULTS: Eyes with the Tecnis Z9000 IOL had significantly less spherical aberration and a greater Strehl ratio after surgery. Significant reduction in coma aberration was also found in some cases. Refraction, visual acuity, and contrast sensitivity were not significantly different between the 3 IOL groups. CONCLUSION: A significant reduction in spherical aberration after Tecnis Z9000 IOL implantation was achieved, but visual acuity and contrast sensitivity were not affected by the aspheric silicone IOL compared to spherical acrylic IOLs.

Aged↗
PubMed1993

Impairment of colour contrast sensitivity and neuroretinal dysfunction in patients with symptomatic HIV infection or AIDS.

Ophthalmic and neurological complications are frequent findings in patients with AIDS. Little is known about neuroretinal dysfunction in patients with HIV infection. The purpose of this study was to measure and evaluate colour vision in patients with HIV infection or AIDS. Colour contrast sensitivity tests were performed on 75 patients (150 eyes) in different stages of HIV infection. A highly sensitive computer graphics system was used to measure tritan, deutan, and protan colour contrast thresholds. Patients were classified into three clinical groups: (a) asymptomatic HIV infection, (b) lymphadenopathy syndrome or AIDS-related complex, and (c) AIDS. Overall, tritan (p < 0.0001), deutan (p = 0.003), and protan (p = 0.009) colour contrast sensitivities were significantly impaired in patients with HIV infection compared with normal controls. Colour thresholds in patients with asymptomatic HIV infection (mean tritan threshold: 4.33; deutan: 4.41; protan: 3.97) were not impaired compared with normal controls. Colour vision was slightly impaired in patients with lymphadenopathy syndrome or AIDS-related complex (tritan: 6.25 (p < 0.0001); deutan: 4.99 (p = 0.02); protan: 4.45 (p = 0.05)). In patients with AIDS the impairment was even more marked (tritan: 7.66 (p < 0.0001); deutan: 5.15 (p < 0.0009); protan: 4.63 (p = 0.004)). Analysis of covariance controlling for age demonstrated a close association between impairment of tritan colour contrast sensitivity and progression of HIV disease (p < 0.0001). Following Köllner's rule, our study suggests that neuroretinal dysfunction occurs in patients with symptomatic HIV infection or AIDS. This is emphasised by the finding that the relative impairment in tritan vision compared with deutan/protan vision might reflect the difference in the number of cones or receptive fields. Measurement of tritan colour contrast sensitivity appears to be an appropriate and easily applicable method to detect early neuroretinal dysfunction in patients with HIV disease.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Contrast sensitivity and the near point of accommodation after work with a visual display unit.

After several hours of work with a visual display unit (VDU), operators become myopic for a short time. Such transient myopia may be evaluated by measuring contrast sensitivity to a modulated grating pattern. The aim of the present study was to determine whether there are any accumulative myopic effects after 1 day of VDU work. We examined grating contrast sensitivity in a group of 13 full-time workers and in 13 office employees who used VDUs only sporadically. The results, which were compared with the near point of accommodation, clearly illustrated that there is no decrease in contrast sensitivity. In the VDU group the decrease in the near point of accommodation was uniformly distributed between zero and 1.0 diopter, whereas among the non-VDU workers 77% of the decrease was between zero and 0.25 diopter. We conclude that the myopic changes in the refractive status of operators after VDU work are not evident in a decrease in contrast sensitivity. However, in VDU workers the dynamic range of accommodation was smaller, suggesting that the visual fatigue and visual stress that developed at work hindered visual activities after work.

Accommodation, Ocular↗
PubMed1992

Contrast sensitivity in clinical practice.

We collected and evaluated the results of contrast sensitivity (CS) examination by means of Vistech chart with an arranged testing distance 208 and 420 cm covering spatial frequencies 1.15-27.25 cycles/degree (c/deg). Our test was comprised of normal population and patients with chronic renal insufficiency including the group of waiting patients, dialysed patients and dialysed patients after neuroretinopathy and also patients after kidney transplantation and those with Alport's syndrome. We gave our attention to the results of visual acuity (VA) and contrast sensitivity (CS) examination in patients after surgery for detached retina, aphakic patients and patients with artephakia. We examined and evaluated CS in patients with intraocular hypertension. All patients reached the VA values 6/9-6/6. 1. The results of examination of 100 healthy persons of different age displayed significant differences in age groups covering all spatial frequencies between the groups 21-50, 51-60 and 61-80 years whereas in sets of higher age we registered differences in the region of medial spatial frequencies only. These data served us to create control groups in the individual partial groups. 2. Patients with chronic renal insufficiency have CS significantly lowered. These examinations suggest that there is a certain relation between renal and retinal functions and that the dialyzation treatment is not able as yet to compensate fully all changes evoked by renal insufficiency. A clear tendency to normalize CS after renal transplantation is suggestive of a certain reversibility of these changes. This is valid for transplant patients with a clear lens. If opacity of the posterior cortex of the lens occurs after a long-time cortisone treatment, a substantial fall in the CS curve is registered in all spatial frequencies in spite of the VA being 6/9-6/6. Patients with neuroretinopathy have CS always significantly disturbed. These changes are reversible although this reversibility is not complete. The new way of dialyzation treatment secures a relatively rapid normalisation of pathological changes in the fundus and repair of subjective functions. At the same time we came to the conclusion that the prognostic outlooks of these patients have become distinctly better as far as their subjective visual functions are concerned. 3. Patients after surgery for detached retina displayed in all cases in the operated eye highly reduced CS in median and low spatial frequencies simultaneously with a statistically significantly lower threshold visual acuity and reduced slope of the acuity function in the diseased eye.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMedDate not supplied

Postoperative wavefront analysis and contrast sensitivity of a multifocal apodized diffractive IOL (ReSTOR) and three monofocal IOLs.

PURPOSE: To compare visual acuity, total and high order wavefront aberrations (coma, spherical aberration, and other terms of high order aberration), and contrast sensitivity in 105 eyes implanted with 4 different types of intraocular lenses (IOLs) (1 multifocal apodized diffractive IOL and 3 monofocal IOLs). METHODS: A prospective study comparing four types of IOLs (Alcon ReSTOR [50 eyes], Alcon Acrysof MA30AC [20 eyes], Alcon Acrysof SA60AT [20 eyes], and Mediphacos Acqua IOL [15 eyes]) was carried out. All eyes were targeted for emmetropia. Complete ophthalmological examination, including uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), contrast sensitivity (Pelli-Robson chart), and wavefront analysis, was performed 2 months postoperatively. RESULTS: All eyes in all groups had BSCVA > or = 20/32 postoperatively. Mean total aberration root-mean-square (RMS) values were: 0.72 +/- 0.25 microm (ReSTOR), 0.94 +/- 0.26 microm (MA30), 0.84 +/- 0.23 microm (SA60), and 2.04 +/- 0.77 microm (Acqua). Mean higher order aberration values were: 0.35 +/- 0.15 microm (ReSTOR), 0.41+/- 0.12 microm (MA30), 0.43 +/- 0.13 microm (SA60), and 0.85 +/- 0.50 microm (Acqua). The Acqua IOL showed statistically significant more total and higher order aberrations when compared with the other IOLs (P < .05). The ReSTOR IOL showed statistically significant less induction of spherical aberration when compared to the monofocal IOLs (P < .05). Mean contrast sensitivity values were: 1.64 +/- 0.08 (ReSTOR), 1.72 +/- 0.08 (MA30), 1.70 +/- 0.07 (SA60), and 1.65 +/- 0.11 (Acqua). CONCLUSIONS: Different types of IOLs resulted in measurably different postoperative higher order aberration patterns. The multifocal apodized diffractive IOL (ReSTOR) induced significantly less spherical aberration compared to the monofocal IOLs. Contrast sensitivity revealed better values with MA30 and SA60 IOLs when compared to ReSTOR. The integration of wavefront technology in evaluating pseudophakic patients represents a step towards better understanding and analyzing postoperative visual quality.

Aged↗
PubMed1990

Development of contrast sensitivity and acuity of the infant colour system.

We have monitored the development of infant colour vision by measuring chromatic contrast sensitivity and acuity in eight young infants over a period of 6 months. Steady-state visual evoked potentials (VEPS) were recorded in response to both chromatic (red-green) and luminance (red-black or green-black) patterns that were reversed in contrast over time. For most infants, no response could be obtained to chromatic stimuli of any size or contrast before 5 weeks of age, although luminance stimuli of 20% contrast gave reliable responses at that age. When responses to chromatic stimuli first appeared, they could be obtained only with stimuli of very low spatial frequency, 20 times lower than the acuity for luminance stimuli. Both contrast sensitivity and acuity for chromatic stimuli increased steadily, more rapidly than for luminance stimuli. As the spectral selectivities of infant cones are similar to those of adults, the difference in rate of development of luminance and chromatic contrast sensitivity and acuity stimuli probably reflects neural development of the infant colour system.

Age Factors↗
PubMed1987

Contrast sensitivity function in nephropathic cystinosis.

Cystinosis is a rare autosomal recessive metabolic disorder in which nonprotein cystine accumulates within most body organs due to a defect in lysosomal cystine transport. The pathognomonic ocular manifestations of cystinosis are the presence of distinctive iridescent crystals within ocular tissue and a pigmentary retinopathy. We measured spatial contrast sensitivity in seven patients with infantile-onset nephropathic cystinosis and compared their contrast sensitivity function with that measured in ten age-matched controls. Spatial contrast sensitivities in the patient group were significantly lower than those in the normal group. Loss of contrast sensitivity in the patients with nephropathic cystinosis was more pronounced at higher spatial frequencies. We speculate that this loss of contrast function is primarily a manifestation of corneal disease, with secondary contributions from retinal changes and central nervous system dysfunction.

Adolescent↗
PubMed1982

Temporal contrast sensitivity and cortical magnification.

We measured temporal and spatial contrast sensitivity functions of foveal and peripheral photopic vision at various locations in the nasal visual field. Sensitivity decreased monotonically with increasing eccentricity when it was measured by using the same test gratings at different eccentricities. When the gratings were normalized in area, spatial frequency, and translation velocity by means of the cortical magnification factor M so that the calculated cortical representations of the gratings became equivalent at different eccentricities, the temporal contrast sensitivity functions became similar at all eccentricities. The normalization was effective under all experimental conditions that included various kinds of temporal modulation from 0 to 25 Hz (movement, counterphase flicker and on-off flicker) and different threshold tasks (detection, orientation discrimination, and discrimination of movement direction), independently of the subjective appearances of the gratings at threshold. We conclude that central and peripheral vision are qualitatively similar in spatiotemporal visual performance. The quantitative differences observed without normalization seem to be caused by the spatial sampling properties of retinal ganglion cells that are directly related to the values of M used in the normalization.

Humans↗
PubMed1988

Contrast sensitivity for oscillating sine wave gratings during ocular fixation and pursuit.

The influence of pursuit eye movements on the visibility of sine wave gratings was investigated by the simultaneous measurement of eye movements and contrast thresholds under different viewing conditions. It was concluded that: 1. with moving gratings contrast sensitivity during ocular pursuit was equal to contrast sensitivity during maintained fixation on a stationary target, provided that the magnitude of retinal image motion (0-20 deg/sec) was equal in both cases; 2. accurate pursuit eye movements led to a paradoxical suppression of the visibility of low spatial frequency gratings; 3. the visibility of high spatial frequency gratings remained unchanged during accurate pursuit eye movements; 4. iso-contrast-sensitivity resulting from both pursuit and non-pursuit conditions could be used to quantify the ocular pursuit performance.

Contrast Sensitivity↗
PubMed2006

Measurement of contrast sensitivity and glare under mesopic and photopic conditions following wavefront-guided and conventional LASIK surgery.

PURPOSE: To compare contrast and glare vision in a prospective study of eyes treated using conventional and wavefront-guided LASIK surgery. The reproducibility of a glaremeter device used to quantitatively measure glare and halo was also determined. METHODS: Ninety-two eyes of 46 patients underwent conventional LASIK surgery and 104 eyes of 52 patients underwent wavefront-guided LASIK surgery. Visual acuity, glare disability measured using a glaremeter, and contrast sensitivity assessed using a Pelli-Robson chart were measured monthly for 6 months postoperatively. Glaremeter testing was performed under both mesopic (5.4 +/- 0.4 cd/m2) and photopic (78.3 +/- 4.4 cd/m2) conditions. To evaluate the reproducibility of the glaremeter, 36 eyes of 18 nonoperated myopic patients were tested. RESULTS: The coefficient of variation and the reliability coefficient for the glare test were 13.6% and 95.2%, respectively. The glaremeter showed that glare disability under mesopic conditions differed between conventional and wavefront-guided LASIK eyes over 6-month follow-up (907.5 +/- 491.5 vs 986.1 +/- 448.0 pixels preoperatively and 1717.1 +/- 521.2 vs 1407.8 +/- 411.3 pixels at 6 months, P<.0001). At 6 months, contrast sensitivity log values were 1.62 +/- 0.31 and 1.78 +/- 0.34 for conventional and wavefront-guided LASIK eyes, respectively (P=.010). The visual complaint score was lower in the wavefront-guided LASIK group (P=.0116). CONCLUSIONS: Compared to conventional ablation, wavefront-guided ablation provided superior outcomes in terms of postoperative glare under mesopic conditions, subjective complaints, and contrast sensitivity. In addition, it appears the glaremeter can be used for clinical quantitative evaluation of glare and halo.

Adult↗
PubMed1995

Visual acuity and contrast sensitivity in the elderly.

The visual acuity of the better eye in the elderly inhabitants of three communities (476 persons, aged 70 years or more) ranged from 0 to 1.4 (mean 0.7), and 12% saw less than 0.3. The logarithm of binocular contrast sensitivity ranged from 1.0 to 2.75 (n = 412, mean 2.19) in the Cambridge test and from 0.15 to 1.95 (n = 468, mean 1.48) in the Pelli-Robson test. The 72 subjects with healthy eyes had a mean visual acuity of 1.03 (range 0.5-1.4) in the better eye, and the two contrast sensitivity tests gave mean values of 2.45 and 1.69, respectively. Cortical, nuclear and mixed cataracts and macular pathology impaired both contrast sensitivity and visual acuity. The correlation between the three tests was good in the whole sample and in the different subgroups of cataract and macular changes. Individually, however, a few contradictory results were obtained. According to these results measurement of contrast sensitivity does not add much to the general information obtained in the elderly by visual acuity measurement alone, but in selected cases it may give valuable information.

Aged↗
PubMed1987

Contrast sensitivity of the human pattern electroretinogram.

Contrast thresholds for the pattern electroretinogram (PERG) were measured using lock-in amplifier retrieval of the retinal signal and a swept contrast display. Contrast sensitivity functions (CSF) developed from these PERG contrast thresholds were compared with those established psychophysically under identical stimulus conditions. Whereas the PERG CSF showed a band-pass characteristic across temporal frequency, the psychophysical CSF (and a temporal CSF developed from visual evoked potential contrast thresholds) had a low-pass pattern. Across spatial frequency, the PERG and psychophysical CSFs had similar shapes, although the PERG CSF peaked at a lower spatial frequency than the psychophysical CSF.

Adult↗
PubMed1985

Effect of age on contrast sensitivity function: uniocular and binocular findings.

Monocular and binocular contrast sensitivity function for a range of spatial frequencies was measured in two groups of subjects with normal vision. Statistically significant differences in performance between the younger group (age 20-30 years) and the older group (age 50-87 years) were found at all spatial frequencies sampled between 0.40 and 19 X 25 cpd. In the age range 50-87 years there was a linear decline in contrast sensitivity with age for medium and high spatial frequencies, but sensitivity for low spatial frequencies was independent of age.

Adult↗
PubMed2006

Contrast sensitivity in seasonal and nonseasonal depression.

BACKGROUND: Psychophysics has been used for the early diagnosis of many diseases that affect the visual pathway including those not usually considered vision-related (e.g., Parkinson's disease). Little has been done, however, to investigate visual functioning in psychological disorders known to be effectively treated by phototherapy. We measured the static and dynamic spatial contrast detection thresholds of seasonally depressed (SAD), nonseasonally depressed (Depressed) and nondepressed (Control) individuals. METHODS: Two psychophysical experiments which measured luminance contrast detection thresholds were conducted. Experiment 1 presented static, vertically oriented Gabors with center spatial frequencies ranging from 0.3 to 12.0 cpd (cycles per degree). Experiment 2 presented 0.5, 1.5 and 4.0 cpd Gabors whose phases were sinusoidally reversed at 2.0, 4.0, 8.0, 16.0, and 32.0 c/s (Hz). RESULTS: SAD showed significantly greater contrast sensitivities than Controls for static spatial frequencies equal to or greater than 6.0 cpd. Depressed showed significantly greater contrast sensitivities at 6.0 cpd and 12.0 cpd. With phase modulation, the SAD group showed significantly enhanced contrast sensitivity with 4.0 cpd-2.0 Hz Gabors. All other results at lower spatial-higher temporal frequencies were not significant. LIMITATIONS: Most of the subjects were drawn from the student population instead of the community or clinics, even though they met the criteria for clinical depression. Antidepressant use was not controlled for among the subjects. CONCLUSIONS: These findings suggest that clinical depression can enhance contrast sensitivity when stimuli elicit strong parvocellular responses. These enhancements implicate differences in retinal functionality. Mechanisms that link neuromodulatory activity to retinal signal processing are proposed.

Adult↗