Uniform-Field Flicker Masking in Control and Specifically-Disabled Readers

Perception ◽  
1988 ◽  
Vol 17 (2) ◽  
pp. 203-214 ◽  
Author(s):  
Frances Martin ◽  
William J Lovegrove
Keyword(s):  
Test Stimulus ◽  
Contrast Sensitivity ◽  
Temporal Frequency ◽  
Control Group ◽  
Uniform Field ◽  
Complex Situation ◽  
Spatial Frequencies ◽  
Stationary Test ◽  
Disabled Readers ◽  
Transient System

Possible transient-system deficiencies in subjects with specific reading disabilities (SRDs) were investigated in groups of 13-year-old SRDs and control normal readers. In experiment 1, in which a 6 Hz uniform-field flicker (UFF) mask and a stationary test stimulus were used, it was found that the overall effect of UFF masking was to reduce differences in contrast sensitivity between SRDs and normal readers. In experiments 2a and 2b, with UFF masks of 6 and 20 Hz and a 6 Hz moving (experiment 2a) or flickering (experiment 2b) test stimulus, contrast sensitivity in both groups was decreased in the presence of the 6 Hz UFF mask. Only the control group, however, showed a further decrease in sensitivity with the 20 Hz UFF mask. This indicates that the groups differ in terms of a mechanism sensitive to high temporal frequencies. A 20 Hz counterphase flickering test stimulus was used in experiment 3 in the presence of 6 Hz UFF, and it was found that SRDs are less sensitive than controls to 20 Hz flicker across all spatial frequencies used. The 6 Hz mask, however, did not differentially affect the two groups. These findings provide further evidence for a transient-system deficit in the visual systems of SRDs, but also suggest a more complex situation by showing that the two groups differ in a high-temporal-frequency mechanism.

Flicker Contrast Sensitivity in Normal and Specifically Disabled Readers

Perception ◽  
1987 ◽  
Vol 16 (2) ◽  
pp. 215-221 ◽  
Author(s):  
Frances Martin ◽  
William Lovegrove
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Temporal Frequency ◽  
Temporal Contrast ◽  
Control Subjects ◽  
Visual Systems ◽  
Spatial Frequencies ◽  
Disabled Readers ◽  
Transient System

Temporal contrast sensitivity for counterphase flicker was determined for specifically disabled and normal readers to investigate whether the two groups differ in the functioning of their transient systems. In experiment 1, temporal contrast sensitivity was measured over a range of temporal frequencies with a spatial frequency of 2 cycles deg−1. Disabled readers were less sensitive than the control subjects at all temporal frequencies. In experiment 2, temporal contrast sensitivity was measured at a temporal frequency of 20 Hz over a range of spatial frequencies. Disabled readers were less sensitive than the controls at all spatial frequencies, with the differences between the groups increasing as spatial frequency increased. Both these findings are interpreted as supporting the hypothesis of a transient-system deficit in the visual systems of disabled readers.

Flicker Masking of Spatial-Frequency-Dependent Visible Persistence and Specific Reading Disability

Perception ◽  
1984 ◽  
Vol 13 (5) ◽  
pp. 527-534 ◽  
Author(s):  
Walter L Slaghuis ◽  
William Lovegrove
Keyword(s):  
Spatial Frequency ◽  
Reading Disabilities ◽  
Visible Persistence ◽  
Control Group ◽  
Uniform Field ◽  
Specific Reading Disability ◽  
Specific Reading ◽  
Spatial Frequencies ◽  
Transient System ◽  
Average Readers

The effect of 6 Hz uniform-field flicker masking of visible persistence at a range of spatial frequencies was investigated in 12-year-old children with specific reading disabilities and a control group of average readers. This reduced differences in visible persistence between the two groups. The results suggest that children with specific reading disabilities experience a deficit in their transient system.

Contrast Sensitivity and Visual-Field Thresholds in Patients with Thyroid Optic Neuropathy

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 194-194
Author(s):  
J Jankauskiene ◽  
R Lukauskiene ◽  
B Mickiene
Keyword(s):  
Visual Acuity ◽  
Visual Field ◽  
Contrast Sensitivity ◽  
Optic Neuropathy ◽  
Control Group ◽  
Ophthalmological Examination ◽  
Threshold Test ◽  
Spatial Frequencies ◽  
Snellen Visual Acuity ◽  
The Mean

Thyroid optic neuropathy is one of the most troubling complications of endocrine ophthalmopathies. It is related to the degree of extraocular muscle swelling in the apex of the orbit. The purpose of this study was to investigate contrast sensitivity and visual-field thresholds in patients with thyroid optic neuropathy. We examined twenty-two patients aged 29 – 63 years (mean 45.3 years). The control group consisted of fifteen healthy persons of similar age. Contrast sensitivity was measured by means of Volkov's charts (sinusoidal gratings) at eight spatial frequencies from 17.5 to 0.46 cycles deg−1. The visual field was investigated with a static automatic perimeter (Allgan Humphrey Field Analyzer) by means of the central 30-2 threshold test. All patients underwent a complete ophthalmological examination including best corrected Snellen visual acuity, fundus copy, and proptosis measurement with the Hertel exophthalmometer. The mean proptosis of patients was 19.4 mm. Fifteen of the patients had decreased visual acuity. Contrast sensitivity at low spatial frequencies was significantly reduced in the patients. It was established that a reduction of visual-field threshold accompanies the decrease of visual acuity. Our results show that contrast sensitivity and visual-field threshold testing are very sensitive at detecting early optic neuropathy and may be a useful means of following patients after treatment.

Influence of corneal guttae and nuclear cataract on contrast sensitivity

2020 ◽  
pp. bjophthalmol-2019-315206
Author(s):  
Victor A Augustin ◽  
Julia M Weller ◽  
Friedrich E Kruse ◽  
Theofilos Tourtas
Keyword(s):  
Contrast Sensitivity ◽  
Central Corneal Thickness ◽  
Corneal Thickness ◽  
Control Group ◽  
Study Group ◽  
Nuclear Cataract ◽  
Inclusion Criteria ◽  
Corneal Densitometry ◽  
Spatial Frequencies ◽  
Corneal Volume

AIMSTo evaluate the contrast sensitivity in patients with nuclear cataract and corneal guttae compared to patients with nuclear cataract without guttae.METHODSIn this retrospective, single-centre case series, 50 eyes of 50 patients fulfilling the inclusion criteria were enrolled. Patients with corneal guttae and nuclear cataract (n=25, study group) underwent triple Descemet membrane endothelial keratoplasty (DMEK). Patients with nuclear cataract and healthy corneas underwent cataract surgery (n=25, control group). Inclusion criteria were preoperative best-corrected visual acuity ≥20/40, no corneal oedema and similar lens opacity (nuclear opalescence 2.0–2.9). Outcome measures included MARS letter and OPTEC 6500P contrast sensitivity test, corneal volume, central corneal thickness and anterior and posterior corneal densitometry.RESULTSPreoperative MARS letter and OPTEC 6500P contrast sensitivity was significantly worse in the study group (MARS: p<0.001; OPTEC 6500P: p<0.007 at low spatial frequencies in daylight with and without glare and nightlight without glare). After surgery, there was no significant difference in MARS letter contrast sensitivity between groups (p=0.225). OPTEC 6500P contrast sensitivity remained significantly lower in the study group in daylight and nightlight with and without glare at most spatial frequencies (p<0.01) postoperatively. Preoperative and postoperative corneal volume, central corneal thickness and anterior corneal densitometry were equal in both groups (p>0.05). Posterior densitometry was significantly higher in the study group than in the control group preoperatively (p<0.001) but turned into equal values postoperatively (p=0.07).CONCLUSIONSCorneal guttae cause an additional significant decrease in contrast sensitivity in eyes with nuclear cataract. This is in favour of performing a triple DMEK even in eyes with a visual acuity of ≥20/40.

scholarly journals Contrast Sensitivity of Cats and Humans in Scotopic and Mesopic Conditions

2009 ◽  
Vol 102 (2) ◽  
pp. 831-840 ◽  
Author(s):  
Incheol Kang ◽  
Rachel E. Reem ◽  
Amy L. Kaczmarowski ◽  
Joseph G. Malpeli
Keyword(s):  
Contrast Sensitivity ◽  
Temporal Frequency ◽  
Companion Paper ◽  
Behavioral Data ◽  
Scotopic Vision ◽  
Visual Systems ◽  
Spatial Frequencies ◽  
Dim Light ◽  
The Right ◽  
Central Fixation

Human contrast sensitivity in low scotopic conditions is regulated according to the deVries–Rose law. Previous cat behavioral data, as well as cat and mice electrophysiological data, have not confirmed this relationship. To resolve this discrepancy at the behavioral level, we compared sensitivity in dim light for cats and humans in parallel experiments using the same visual stimuli and similar behavioral paradigms. Both species had to detect Gabor functions (SD = 1.5°, spatial frequencies from 0 to 4 cpd, temporal frequency 4 Hz) presented 8° to the right or left of a central fixation point over an 8 log-unit range of adaptation levels spanning scotopic vision and extending well into the mesopic range. Cats had 0.74 log unit greater absolute sensitivity than that of humans for spatial frequencies ≤1/8 cpd. Cats had better contrast sensitivity overall for spatial frequencies <1/2 cpd, whereas humans were more sensitive for spatial frequencies above this. However, most of the cat's sensitivity advantage for low spatial frequencies could be accounted for by the greater light-concentrating abilities of its optics. Contrast sensitivity to 4 cpd was poor or absent in the scotopic range for both species. For both, scotopic increment thresholds were proportional to the square root of retinal illuminance, in accordance with the deVries–Rose law. Overall, cat and human visual systems appear to operate under very similar constraints for rod vision, including the regulation of contrast sensitivity across adaptation levels. A companion paper compares sensitivity of neurons in the lateral geniculate nucleus to these behavioral data.

The Perceived Spatial Frequency, Contrast, and Orientation of Illusory Gratings

Perception ◽  
1980 ◽  
Vol 9 (6) ◽  
pp. 695-712 ◽  
Author(s):  
Mark A Georgeson
Keyword(s):  
Spatial Frequency ◽  
Temporal Frequency ◽  
Interocular Transfer ◽  
Contrast Threshold ◽  
Supporting Evidence ◽  
Uniform Field ◽  
Apparent Contrast ◽  
Spatial Frequencies ◽  
The Matrix ◽  
Matching Techniques

Illusory vertical gratings (V) and diagonal gratings (D) can be seen on a uniform field after inspection of a vertical grating. When using simultaneous and successive matching techniques the spatial frequencies of the V effect were found to be about 2 octaves below and 1–2 octaves above the adapting spatial frequency, but to be invariant with temporal frequency. At high adapting frequencies the D effect dominated, and was about 0·8 octave below the adapting spatial frequency, oriented about ±35° from vertical. The apparent contrast of V was about twice the value of the contrast threshold at its apparent spatial frequency. D effects seen during adaptation were about 60° from vertical and 3 octaves below the adapting frequency. The results are interpreted in terms of inhibition and disinhibition in an organized matrix of tuned channels, and the dominant pattern of inhibition in the matrix is inferred. Supporting evidence from neurophysiology, neuroanatomy, and psychophysics is briefly reviewed. An appendix deals with the question of interocular transfer of the aftereffect.

Contrast sensitivity in relapsing–remitting multiple sclerosis assessed by sine-wave gratings and angular frequency stimuli

2014 ◽  
Vol 31 (6) ◽  
pp. 381-386 ◽  
Author(s):  
JÁKINA G. VIEIRA-GUTEMBERG ◽  
LIANA C. MENDES-SANTOS ◽  
MELYSSA K. CAVALCANTI-GALDINO ◽  
NATANAEL A. SANTOS ◽  
MARIA LÚCIA DE BUSTAMANTE SIMAS
Keyword(s):  
Multiple Sclerosis ◽  
Visual System ◽  
Contrast Sensitivity ◽  
Sine Wave ◽  
Angular Frequency ◽  
Control Group ◽  
Spatial Frequencies ◽  
Relapsing Remitting ◽  
The One ◽  
Sine Wave Gratings

AbstractPrevious studies have shown that multiple sclerosis (MS) affects the visual system, mainly by reducing contrast sensitivity (CS), a function that can be assessed by measuring contrast sensitivity function (CSF). To this end, we measured both the CSF for sine-wave gratings and angular frequency stimuli with 20 participants aged between 21 and 44 years, of both genders, with normal or corrected to normal visual acuity. Of these 20 participants, there were 10 volunteers with clinically defined MS of the relapsing–remitting clinical form, with no history of optic neuritis (ON), as well as 10 healthy volunteers who served as the control group (CG). We used a forced-choice detection paradigm. The results showed reduced CS to both classes of stimuli. Differences were found for sine-wave gratings at spatial frequencies of 0.5, 1.25, and 2.5 cycles per degree (cpd) (P < 0.002) and for angular frequency stimuli of 4, 24, and 48 cycles/360° (P < 0.05). On the one hand, comparing the maxima of the respective CSFs, the CS to angular frequency stimuli (24 cycles/360°) was 1.61-fold higher than that of the CS to vertical sine-wave gratings (4.0 cpd) in the CG; for the MS group, these values were 1.55-fold higher. On the other hand, CS in the MS group attained only 75% for 24 cycles/360° and 78% for 4.0 cpd of the 100% CS estimates found for the CG at the peak frequencies. These findings suggest that MS affects the visual system, mostly at its maximum contrast sensitivities. Also, since angular frequencies and sine-wave gratings operate at distinct levels of contrast in the visual system, MS seems to affect CS at both high and low levels of contrast.

scholarly journals Are Contrast Sensitivity Functions Impaired in Insulin Dependent Diabetics Without Diabetic Retinopathy?

1999 ◽  
Vol 42 (4) ◽  
pp. 133-138 ◽  
Author(s):  
Vladimír Liška ◽  
Miroslav Dostálek
Keyword(s):  
Visual Acuity ◽  
Diabetic Retinopathy ◽  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Dependent Diabetes Mellitus ◽  
Control Group ◽  
Study Group ◽  
Sensitivity Functions ◽  
Spatial Frequencies ◽  
Insulin Dependent

Purpose: To confirm the influence of multilevel metabolic disturbance of insulin dependent diabetes mellitus (IDDM) on the vision even before the onset of the other changes routinely evaluated by ophthalmologists. Methods: Contrast sensitivity functions (CSFs) were estimated using the VCTS 6500 board. The standardised measurement procedure was performed. The value of the threshold contrast sensitivity was obtained for five spatial frequencies (1.5 - 3 - 6 - 12 - 18 c/deg). Other data was collected (duration of diabetes, BCVA, funduscopy, fluoresceine angiography, HbA1C). The study group consisted of 48 IDDM patients (94 eyes) without diabetic retinopathy and with Snellen BCVA > 1.0. The control group (56 normals, 98 eyes) was age and BCVA matched. Results: Highly statistically significant decrease of the CSFs in all spatial frequencies in the study group was obtained. Correlation between duration of the diabetes and impaired degree of CSFs was present in the middle spatial frequency. No significant changes in CSFs were found among patients with pathological value of glycated hemoglobin HbA1c (>7.8 %). Conclusions: If compared with routinely used Snellen visual acuity, the CSFs are more complex descriptors of the subjects vision abilities. IDDM has an influence on these sensitive functions, especially during examination in the middle spatial frequency of 6 and 12 c/deg, before disturbing visual acuity and before changes in the retinal morphology. Decrease of CSFs was influenced mainly by the patients’ age and partially (in the middle spatial frequency) by the IDDM duration.

scholarly journals The “Spinner” Illusion: More Dots, More Speed?

i-Perception ◽  
2017 ◽  
Vol 8 (3) ◽  
pp. 204166951770797
Author(s):  
Hiroshi Ashida ◽  
Alan Ho ◽  
Akiyoshi Kitaoka ◽  
Stuart Anstis
Keyword(s):  
Test Stimulus ◽  
Temporal Frequency ◽  
Angular Speed ◽  
Circular Path ◽  
Reference Stimulus ◽  
Spatial Frequencies ◽  
Sinusoidal Gratings ◽  
Speed Perception ◽  
Perceived Speed

The perceived speed of a ring of equally spaced dots moving around a circular path appears faster as the number of dots increases (Ho & Anstis, 2013, Best Illusion of the Year contest). We measured this “spinner” effect with radial sinusoidal gratings, using a 2AFC procedure where participants selected the faster one between two briefly presented gratings of different spatial frequencies (SFs) rotating at various angular speeds. Compared with the reference stimulus with 4 c/rev (0.64 c/rad), participants consistently overestimated the angular speed for test stimuli of higher radial SFs but underestimated that for a test stimulus of lower radial SFs. The spinner effect increased in magnitude but saturated rapidly as the test radial SF increased. Similar effects were observed with translating linear sinusoidal gratings of different SFs. Our results support the idea that human speed perception is biased by temporal frequency, which physically goes up as SF increases when the speed is held constant. Hence, the more dots or lines, the greater the perceived speed when they are moving coherently in a defined area.

scholarly journals Visual Functions in Aphakia After Secondary Intraocular Lens Implantation

1997 ◽  
Vol 40 (3) ◽  
pp. 75-78
Author(s):  
Hana Langrová ◽  
Dagmar Hejcmanová ◽  
Jaroslav Peregrin
Keyword(s):  
Contrast Sensitivity ◽  
Intraocular Lens ◽  
Control Group ◽  
Intraocular Lens Implantation ◽  
Computerized Method ◽  
Spatial Frequencies ◽  
Lens Implantation ◽  
Before And After ◽  
Snellen Chart ◽  
Secondary Intraocular Lens Implantation

21 aphakic eyes of 21 patients corrected by glasses (A-G) were examined 1 and 6 months before and after secondary intraocular lens implantation (SILI). Visual acuity (VA) was tested using Snellen chart and computerized method with Landolt rings (CL). Contrast sensitivity (CS) was measured using computerized Contrast sensitivity system 8010 in spatial frequencies from 0.74 to 29.55 c/deg. Preoperative best corrected VA (BCVA) in A-G eyes was significantly lower in comparison with control group of the same age only using computerized method with Landolt rings. A reduction of BCVA by both methods at 1 month and its return to original values after 6 months were noted. Significantly lower values of CS were found in A-G patients before SILI compared to the control group of the same median age in spatial frequencies from 3.69 to 29.55 c/deg. After 1 and 6 months the values stayed on the preoperative level, except the frequency 29.55 c/deg, which increased significantly (p < 0.01) 6 months after SILI.

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