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PubMed2004

Visual performance with multifocal intraocular lenses: mesopic contrast sensitivity under distance and near conditions.

OBJECTIVE: To evaluate distance and near visual performance under bright (photopic) and dim (mesopic) conditions in patients who had undergone uncomplicated cataract extraction with multifocal or monofocal intraocular lens (IOL) implantation. DESIGN: Prospective, nonrandomized, masked, comparative, observational case series. PARTICIPANTS: Thirty-two eyes of 32 patients after zonal-progressive multifocal IOL implantation (Allergan Medical Optics Array SA-40N) and 32 eyes of 32 age-matched patients after monofocal IOL implantation (Allergan Medical Optics SI-40NB). INTERVENTION: All eyes underwent phacoemulsification and IOL implantation. MAIN OUTCOME MEASURES: At 18 months after surgery, the monocular contrast sensitivity (CS) function was measured with sinusoidal grating charts at distance and near, at one photopic luminance level and 2 mesopic luminance levels (85, 5, and 2.5 candelas per square meter). RESULTS: Under bright conditions, CS at distance in the multifocal group was not statistically different (P>0.01) from that in the monofocal group at any tested grating spatial frequency (1.5, 3, 6, 12, and 18 cycles per degree [cpd]). At low luminances, distance CS for the multifocal group was worse than that for the monofocal group at the highest test spatial frequencies (12 and 18 cpd; P<0.01). At near, photopic CS in the multifocal group was lower than at distance; patients with only a monofocal distance correction, however, could not detect the test gratings, even at the highest available contrast. With optimal near spectacle additions (i.e., using the distance correction of the multifocal IOL), there were no significant differences between the photopic near CS values for the multifocal and monofocal groups. When the luminance was decreased, near CS at all spatial frequencies was reduced in both groups. Contrast sensitivity in the near-corrected, multifocal group was significantly worse than in the near-corrected, monofocal group at high spatial frequencies (12 and 18 cpd). CONCLUSIONS: This work supports the findings of earlier authors that the Array multifocal IOL, with its center-distance design, is distance biased. Distance CS is within normal limits under bright photopic conditions but shows deficits at higher spatial frequencies (more than approximately 12 cpd) under dim mesopic conditions. Near CS obtained with the multifocal IOL is below that which can be achieved by an appropriate monofocal near correction, for all spatial frequencies and illumination conditions.

Aged↗

PubMed1997

Infant color vision: temporal contrast sensitivity functions for chromatic (red/green) stimuli in 3-month-olds.

In order to investigate the development of temporal contrast sensitivity functions (tCSFs) for chromatic (red/green) stimuli, we obtained chromatic contrast thresholds from 3-month-old infants and adults using behavioral techniques. Stimuli were moving or counterphase-reversing sinusoidal gratings of 0.25 c/deg. Five temporal frequencies were used: 0.7, 2.1, 5.6, 11 and 17 Hz (corresponding speeds = 2.8, 8.4, 22, 44 and 67 deg/sec). In order to compare chromatic results with those obtained under luminance-defined conditions, luminance tCSFs were also obtained from adults, and previously obtained infant luminance tCSFs were used (from Dobkins & Teller, 1996a). In accordance with previous studies, adults exhibited bandpass luminance tCSFs with peaks near 5 Hz and lowpass chromatic tCSFs that declined rapidly at temporal frequencies greater than 2 Hz, and the two curves crossed one another near 4 Hz. By contrast, infants exhibited bandpass rather than lowpass chromatic tCSFs with peaks near 5 Hz. These chromatic curves were quite similar in peak frequency and general shape to previously obtained infant tCSFs for luminance stimuli. Moreover, both chromatic and luminance tCSFs in infants were found to be quite similar in peak and shape to luminance tCSFs observed in adults. These findings point to the possibility that, for 3-month-old infants, both chromatic and luminance stimuli are detected by the same underlying mechanism under these conditions. We propose that such a mechanism is probably a physiological pathway dominated by magnocellular input. Earlier studies of infant color vision are discussed in this context.

Adult↗

PubMed1982

Amblyopic contrast sensitivity: insensitivity to unsteady fixation.

Functional amblyopia (a typically unilateral loss of visual acuity of unknown origin) is frequently accompanied by unsteady fixation. Measurements taken under conditions of retinal-image stabilization indicate that this fixation problem does not contribute to the currently measured losses in spatial contrast sensitivity of the amblyopic eye. Indeed, retinal image motions recorded from unsteadily fixating eyes do not produce spatial contrast sensitivity losses when superimposed on the central field of a normal subject, indicating that such losses are not an immediate consequence of unsteady fixation.

Adolescent↗

PubMed1989

Spatial and temporal contrast sensitivity in hemianopia. A comparative study of the sighted and blind hemifields.

Spatial and temporal contrast sensitivity was measured, under identical test conditions using spatially and temporally localized stimuli, in 4 normally sighted human subjects and in 3 healthy hemianopic subjects whose stable visual field loss exhibited foveal sparing. Testing was undertaken at central fixation and at a variety of eccentric loci along the horizontal meridian of the sighted and perimetrically blind field. In comparison with the normal (control) sensitivities obtained in this study, spatial and temporal sensitivities in the sighted hemifield in subjects with striate cortical lesions were both reduced; in addition, we were unable to demonstrate greater-than-chance performance at any extrafoveal locations in the blind hemifield.

Contrast Sensitivity↗

PubMed1992

A new technique to measure contrast sensitivity in human infants.

We used a new time-efficient procedure to obtain binocular contrast sensitivity functions (CSFs) from 80 infants aged 1-, 3-, 6-, and 12-months-old. The test consisted of 5 sets of large (50 by 28 cm) cards constructed by mounting a 7.2 degrees circular sine wave grating with 1 of 5 spatial frequencies (0.3, 0.6, 1.2, 2.4, and 3.6 cpd at 60 cm) onto light gray matteboard. Each card also contained a second 7.2 degrees unpatterned patch of equal space-average luminance. Depending upon the set, the contrast within the gratings ranged from approximately 25 to 0.5%. To judge the subject's detection of each grating we used a rapid version of preferential looking (PL) similar to that developed for the Teller Acuity Cards. Results showed that compared to previous techniques, the card procedure allows one to estimate an infant's CSF much more simply, rapidly, and inexpensively.

Contrast Sensitivity↗

PubMed1981

Contrast sensitivity of neurons in pigeon optic tectum.

An analysis of contrast sensitivity of neurons in the optic tectum of intact and wulst-ablated pigeons was carried out using moving light bars. (1) Changes of contrast from 0.1% to 89%, obtained with different bar luminances, induced increases of response amplitude linearly related to log contrast. (2) The units differed in their contrast threshold but 90.7% had a contrast threshold below 2.5%. (3) Both contrast threshold and threshold-saturation range values were independent of the location of the units in the tectal layers. (4) Contrast threshold remarkably increased on passing from low photopic to scotopic adaptation levels. (5) The relationship between unit responses and contrast values, as well as the contrast threshold value, did not differ between intact and wulst-ablated animals.

Animals↗

PubMed1989

Role of spherical aberration in contrast sensitivity loss with radial keratotomy.

A technique is described to determine the change in image contrast as a result of the spherical aberration induced by the radial keratotomy procedure. The hypothesis that the loss in contrast sensitivity of the RK eye is due to the change in spherical aberration postsurgically, is found to be acceptable for some patients. However, this is not a sufficient explanation in all cases. This conclusion may be due to assumptions inherent in the technique derived for calculating spherical aberration or to other factors of importance in the post-RK eye.

Contrast Sensitivity↗

PubMedDate not supplied

[Contrast sensitivity].

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Contrast Sensitivity↗

PubMed1996

[Contrast sensitivity].

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Contrast Sensitivity↗

PubMed1992

How useful are contrast sensitivity charts in optometric practice? Case reports.

There are now a number of commercially available contrast sensitivity (CS) charts for clinical use. Although a great deal has been written about CS, there is little information regarding its usefulness in optometric practice. In this study 3 commercially available charts (the Vistech system, Pelli-Robson, and Cambridge charts) were used by 6 optometrists in clinical practice over a 14-month period. This report includes a review of the research literature on clinical CS testing, and contains case records from the in-practice study which indicate situations in which the measurement of CS proved useful.

Adult↗

PubMed2003

Monocular chromatic contrast threshold and achromatic contrast sensitivity in children born prematurely.

PURPOSE: To study the effect of prematurity on monocular chromatic contrast thresholds (CCT) and achromatic contrast sensitivity (ACS). DESIGN: Case-control study. METHODS: A prospective study of 59 children born at less than 33 weeks' gestation was undertaken. Subjects were identified during routine neonatal screening for retinopathy of prematurity and recalled for testing at age 7 to 13 years. Five had stage 1 retinopathy of prematurity, seven had stage 2, and three had stage 3. Sixty-eight full-term children were recruited as controls. Those with major cerebral or eye disease were excluded. The CCT and ACS were measured monocularly in the eye with better visual acuity using static, computer-generated, sinusoidal gratings, displayed on a high-resolution monitor. The CCT and ACS were determined using a randomized double-staircase reversal algorithm. The ACS was measured at five spatial frequencies (0.22, 0.44, 0.88, 1.75, and 3.50 cycles/degree), and the CCT was measured along red-green and tritan confusion axes. RESULTS: Red-green (P =.326) and tritan (P =.910) contrast thresholds and ACS (P >.394 for all spatial frequencies) were similar to the control group. CONCLUSIONS: Previous research suggests that prematurity adversely affects color vision and ACS. This study used a computerized psychophysical test that minimized the test errors inherent in many previous studies. Unexpectedly, CCT and ACS were found to be similar to full-term children.

Adolescent↗

PubMed1986

[Contrast sensitivity].

In some patients with neural or ophthalmological lesions, normal visual acuity co-exists with a significantly diminished ability to see larger objects. The converse may also occur. Based upon many years of academic research and some years of clinical application, spatial contrast sensitivity function appears to give the most general description available for the basic aspects of spatial vision performance. This review surveys the main theoretical and experimental works in neurophysiology and psychophysiology which established the significance of contrast sensitivity.

Humans↗

PubMed1993

Influence of the contrast sensitivity function on the reaction time.

The reaction time (RT) vs spatial frequency (SF) curve is determined, using gratings from 1 to 40 c/deg, at seven different contrast levels between 0.95 and 0.02. The form of the RT/SF function: (a) replicated the inverse of the contrast sensitivity function (CSF) at near threshold contrast levels; (b) behaved differently at higher contrasts, exhibiting two branches at contrast close to 1. The interpretation is that there are two factors determining this function: (1) the transition from the operation of fast transient channels at low SF to the operation of slow sustained channels at high SF, the transition taking place within a narrow SF band close to 6 or 8 c/deg (depending on the subject) and (2) the contrast attenuation by the optical and neural transfer function, operating throughout the SF range. At high contrasts, the effect of the first factor can be clearly observed, because the effect of the second factor does not change with spatial frequency except in a region where the RT/SF function changes rapidly. At lower contrasts, however, the second factor becomes increasingly relevant while the first becomes less and less observable.

Contrast Sensitivity↗

PubMedDate not supplied

Relationship between corneal aberrations and contrast sensitivity after hyperopic laser in situ keratomileusis.

PURPOSE: To evaluate the relationship between corneal aberrations and contrast sensitivity (CS) after hyperopic laser in situ keratomileusis (H-LASIK). METHODS: In 13 patients (13 eyes) who underwent H-LASIK, we measured CS and corneal topography preoperatively and at 1 year postoperatively. Photopic and scotopic CS values were measured at 3, 6, and 12 cycles/degree (cpd) using an MCT-8000 contrast tester. Corneal aberrations were determined from the data on corneal topography using CTView. The corneal high-order aberrations were defined as the sum of the third- and fourth-order aberrations in the 4-mm zone and the sum of the third- to sixth-order aberrations in the 6-mm-zone. RESULTS: Under scotopic conditions at 12 cpd, the changes in CS significantly correlated with changes in the corneal aberrations. Scotopic CS was significantly deteriorated by glare, but photopic CS was not significantly changed. H-LASIK induced a significant increase in corneal aberrations that positively correlated with the amount of correction, regardless of the improvement in logMAR corrected visual acuity. LogMAR corrected visual acuity did not significantly correlate with corneal aberrations. Furthermore, decentration significantly correlated with the changes in the 6-mm zone corneal aberrations. CONCLUSIONS: In eyes after H-LASIK, the changes in scotopic CS significantly correlated with those in the corneal aberrations, which might have resulted from decentration or ablation profiles in H-LASIK and a relatively small optical zone. Further studies will be needed to validate this relationship.

Adult↗

PubMed2005

Contrast sensitivity functions to stimuli defined in Cartesian, polar and hyperbolic coordinates.

Recent electrophysiological studies indicate that cells in the LGN, V1, V2, and V4 areas in monkeys are specifically sensitive to Cartesian, polar and hyperbolic stimuli. We have characterized the contrast sensitivity functions (CSF) to stimuli defined in these coordinates with the two-alternatives forced-choice paradigm. CSFs to Cartesian, concentric, and hyperbolic stimuli have had similar shapes, with peak sensitivity at approximately 3 c/deg. However, the Cartesian CSF peak sensitivity has been at least 0.1 log units higher than that to stimuli in any other coordinate system. The concentric-Bessel CSF has a low-pass shape, peaking at 1.5 c/deg or below. The radial CSF has a bell shape with maximum sensitivity at 8 c/360 degrees. Only the concentric-Bessel CSF could be explained in terms of the components of maximum amplitude of the Fourier transform. Neural models, which in previous studies predicted the responses to Cartesian and polar Glass patterns, failed to account for the full CSFs data.

Contrast Sensitivity↗

PubMed1984

Ocular refraction and visual contrast sensitivity of the rabbit, determined by the VECP.

The ocular refraction of the rabbit was determined by inserting spherical lenses of between -3 and +4D and measuring the relative VECP amplitude in response to checkboard patterns of 21 min arc. The rabbit's eye was found to be almost emmetropic (+0. 5D ). The contrast sensitivity function of the rabbit's visual system was determined by recording the VECP in response to reversed gratings of different spatial frequencies. The contrast sensitivity was found to be highest at 0.35 c/deg with an upper cut-off frequency at 3 c/deg, corresponding to a grating acuity of 10 min arc.

Animals↗

PubMed1987

Contrast sensitivity and visual acuity of the pigmented rat determined electrophysiologically.

The contrast sensitivity function of the rat was assessed by investigating the relationship between the amplitude of visually evoked cortical potentials (VECP) and the spatial frequency and contrast of grating stimuli. Pattern reversal VECPs were recorded in Area 17 in the region of representation of the central binocular visual field. Transient responses were obtained with a 1 Hz contrast reversal. The mean contralateral monocular CSF peaked around 0.1 c/deg, with a threshold sensitivity of 20-25, low frequency attenuation and a high frequency cut-off of 1.18 c/deg. The mean binocular CSF showed a cut-off of 1.20 c/deg, which matches several behavioural measurements of visual acuity. The greater binocular sensitivity in the low frequency range (0.04 c/deg) could be tentatively attributed to the greater influence of the population of large ganglion cells that reaches its maximal density in the ipsilateral projection.

Animals↗

PubMed2002

Using a single test to measure human contrast sensitivity from early childhood to maturity.

Despite the emerging scientific and clinical importance of measuring human contrast sensitivity (CS), developmental data are sparse, especially those obtained with a single methodology. We used a new, time-efficient, psychophysical card procedure to evaluate binocular CS in groups of 20 4- to 9-yr-olds and 10 adults. Combined with data from infants and toddlers obtained previously with the same method, our results show that CS is adult-like by 9 years of age. However, the pattern of development is asymmetrical across spatial frequency (SF): Sensitivity at high SF (which is very poor near birth) shows dramatic improvement over the first three years, but sensitivity at low SF shows much more gradual development, a result which may be explained by differences in the maturation of the underlying neural SF channels. Also notable is that the method shows clinical potential due to its relative speed, ease of use, and consistent results across such a broad age range.

Adult↗