Contrast Sensitivity In Adults Research Articles

Standard Amblyopia Therapy in Adults with Longstanding Amblyopia Improves Visual Acuity and Contrast Sensitivity.

Perceptual learning or dichoptic training may result in improved acuity in adult amblyopes. However, for amblyopic children (<18 years), most clinicians recommend standard part-time patching. The purpose of this study was to determine if standard amblyopia therapy results in an enhancement in vision in the amblyopic eye of adults. Fifteen amblyopes (20/30 or worse) were recruited and nine (age (SD) 32.9 (16.31)) with anisometropia or anisometropia and strabismus (ie, combined mechanism amblyopia) completed the study. Previous therapy did not exclude subjects. The subjects received a comprehensive eye exam and wore their best correction for at least four weeks prior to baseline testing. The non-amblyopic eye was patched for 2 hours per day (Amblyopia iNET training for 30 minutes and near/distance activities for 1.5 hours). The subjects had a baseline amblyopia evaluation followed by one visit per week for 12 weeks. At 12 weeks, the treatment was tapered off over one month and the subjects had a final amblyopia evaluation at 24 weeks. Contrast sensitivity was measured at baseline and 12 weeks with the Quick CSF system. The subjects had a significant improvement in visual acuity across the weeks (p < 0.001). At baseline, weeks 12 and 24, the average logMAR acuities (SE) were 0.55 (0.09), 0.41 (0.08), and 0.38 (0.09), respectively. Weeks 4 to 24 were significantly different (p < 0.001) from baseline. The average acuity improvement over the 24 weeks was 1.7 logMAR lines. There was a significant increase in the area under the log contrast sensitivity function (p = 0.002) and its estimated acuity (p = 0.036) from baseline to 12 weeks. Standard amblyopia treatment can result in an improvement in visual acuity and contrast sensitivity in adults with longstanding anisometropic or combined mechanism amblyopia even if they had prior therapy.

High-attention demand training improves contrast sensitivity in adults with amblyopia

High-attention demand training improves contrast sensitivity in adults with amblyopia

正弦光栅用于成人对比敏感度量测之研究

正弦光栅用于成人对比敏感度量测之研究

The effect of transcranial direct current stimulation on contrast sensitivity and visual evoked potential amplitude in adults with amblyopia.

Amblyopia is a neurodevelopmental disorder of vision that occurs when the visual cortex receives decorrelated inputs from the two eyes during an early critical period of development. Amblyopic eyes are subject to suppression from the fellow eye, generate weaker visual evoked potentials (VEPs) than fellow eyes and have multiple visual deficits including impairments in visual acuity and contrast sensitivity. Primate models and human psychophysics indicate that stronger suppression is associated with greater deficits in amblyopic eye contrast sensitivity and visual acuity. We tested whether transcranial direct current stimulation (tDCS) of the visual cortex would modulate VEP amplitude and contrast sensitivity in adults with amblyopia. tDCS can transiently alter cortical excitability and may influence suppressive neural interactions. Twenty-one patients with amblyopia and twenty-seven controls completed separate sessions of anodal (a-), cathodal (c-) and sham (s-) visual cortex tDCS. A-tDCS transiently and significantly increased VEP amplitudes for amblyopic, fellow and control eyes and contrast sensitivity for amblyopic and control eyes. C-tDCS decreased VEP amplitude and contrast sensitivity and s-tDCS had no effect. These results suggest that tDCS can modulate visual cortex responses to information from adult amblyopic eyes and provide a foundation for future clinical studies of tDCS in adults with amblyopia.

Dichoptic training improves contrast sensitivity in adults with amblyopia

Dichoptic training is designed to promote binocular vision in patients with amblyopia. Initial studies have found that the training effects transfer to both binocular (stereopsis) and monocular (recognition acuity) visual functions. The aim of this study was to assess whether dichoptic training effects also transfer to contrast sensitivity (CS) in adults with amblyopia. We analyzed CS data from 30 adults who had taken part in one of two previous dichoptic training studies and assessed whether the changes in CS exceeded the 95% confidence intervals for change based on test–retest data from a separate group of observers with amblyopia. CS was measured using Gabor patches (0.5, 3 and 10cpd) before and after 10days of dichoptic training. Training was delivered using a dichoptic video game viewed through video goggles (n=15) or on an iPod touch equipped with a lenticular overlay screen (n=15). In the iPod touch study, training was combined with anodal transcranial direct current stimulation of the visual cortex. We found that dichoptic training significantly improved CS across all spatial frequencies tested for both groups. These results suggest that dichoptic training modifies the sensitivity of the neural systems that underpin monocular CS.

Long Lasting Effects of Daily Theta Burst rTMS Sessions in the Human Amblyopic Cortex

BackgroundIt has been reported that a single session of 1 Hz or 10 Hz repetitive transcranial magnetic stimulation (rTMS) of the visual cortex can temporarily improve contrast sensitivity in adults with amblyopia. More recently, continuous theta burst stimulation (cTBS) of the visual cortex has been found to improve contrast sensitivity in observers with normal vision. Objective/HypothesisThe aims of this study were to assess whether cTBS of the visual cortex could improve contrast sensitivity in adults with amblyopia and whether repeated sessions of cTBS would lead to more pronounced and/or longer lasting effects. MethodscTBS was delivered to the visual cortex while patients viewed a high contrast stimulus with their non-amblyopic eye. This manipulation was designed to bias the effects of cTBS toward inputs from the amblyopic eye. Contrast sensitivity was measured before and after stimulation. The effects of one cTBS session were measured in five patients and the effects of five consecutive daily sessions were measured in four patients. Three patients were available for follow-up at varying intervals after the final session. ResultscTBS improved amblyopic eye contrast sensitivity to high spatial frequencies (P < 0.05) and there was a cumulative improvement across sessions with asymptotic improvement occurring after 2 daily sessions of stimulation. The contrast sensitivity improvements were stable over a period of up to 78 days. ConclusionsThese initial results in a small number of patients indicate the cTBS may allow for enduring visual function improvements in adults with amblyopia.

Visual contrast sensitivity in adults with schizophrenia and relatives not affected

The aim of this study was to measure visual contrast sensitivity (CS) for vertical sine-wave gratings with spatial frequencies of 0,6; 5 and 10 in adults with medicated schizophrenic and no-affected relatives in the range of 20-30 years old. We measured the visual CS for ten volunteers without schizophrenia, nine schizophrenia patients and five no-affected relatives, all volunteers were free from identifiable ocular disease and had normal acuity, except the condition schizophrenia. We use a temporal two-alternative forced-choice psychophysical method with mean luminance of 40.1 cd/m². The results showed maximum contrast sensitivity occurred in the range of 5.0 cpd for both groups and that the visual CS for participants with schizophrenia was lower than those of adults without schizophrenia and the non-affected relatives. These results showed changes in the visual mechanisms that process vertical sine-wave gratings related the schizophrenia.

Measuring Spatial Contrast Sensitivity in Adults and Children by Combining Sine Waves with Landolt Cs.

Measuring Spatial Contrast Sensitivity in Adults and Children by Combining Sine Waves with Landolt Cs.

Electrophysiological and Psychophysical Differences between Early- and Late-Onset Strabismic Amblyopia

To compare visual evoked potentials (VEPs) and contrast sensitivity in adults with early- or late-onset strabismic amblyopia. Twelve adults with early- and 12 with late-onset strabismic amblyopia with similar ranges of visual acuity were studied. Pattern-onset VEPs to 30-minute checks were recorded at a range of contrast levels. Contrast sensitivity (CS) was measured at 3.2 cyc/deg using a two-alternative, forced-choice staircase method. There was no significant difference in VEP CII latency or amplitude between amblyopic and fellow eyes across all contrast levels for the early-onset group, but in the late-onset group, CII latencies were significantly longer and amplitudes smaller in the amblyopic eye. CII responses in both amblyopic and fellow eyes of the early-onset amblyopes were of significantly shorter latency and smaller amplitude than normal. In the late-onset group the CII responses from the amblyopic eye were of significantly increased latency and reduced amplitude compared with normal, whereas latency and amplitude of fellow eye responses did not differ significantly from normal. Late-onset amblyopes showed reduced CS across the central field for the amblyopic eye, but increased CS for the fellow eye compared with normal. In the early-onset group, central CS did not differ between amblyopic and fellow eyes or from normal. There are significant differences in the electrophysiological and psychophysical characteristics of adults with early- and late-onset strabismic amblyopia.

Effect of acute hypoglycemia on visual information processing in adults with type 1 diabetes mellitus

EWING, F. M. E., I. J. DEARY, R. J. McCRIMMON, M. W. J. STRACHAN AND B. M. FRIER. Effect of acute hypoglycemia on visual information processing in adults with type 1 diabetes mellitus. PHYSIOL BEHAV 64(5) 653–660, 1998.—Acute hypoglycemia in people with type 1 (insulin-dependent) diabetes mellitus causes general impairment in cognitive performance. The effects on more specific cognitive processes are less well defined. Acute hypoglycemia has been shown to impair visual information processing in nondiabetic human subjects and has now been examined in 16 adult subjects with type 1 diabetes. All subjects had normal visual acuity and no diabetic retinopathy, and their median (range) age was 24 (18–47) years with a median (range) duration of type 1 diabetes of 8 (2–18) years and a mean (SD) HbA 1c of 8.5 (1.3)%. A hyperinsulinemic glucose clamp technique was used to maintain arterialized blood glucose at 5.0 mmol l − 1, and on separate test days, either euglycemia was continued or hypoglycemia (2.6 mmol l − 1) was induced. During each condition subjects performed tests of visual processing and cognitive function. Hypoglycemia caused a significant disruption in general cognitive ability as assessed by digit symbol ( p < 0.001) and trail-making B ( p < 0.05) tasks. Conventional measures of visual acuity were unaffected by hypoglycemia, but visual information processing deteriorated significantly as indexed by inspection time ( p < 0.005) and visual change detection ( p < 0.01). Contrast sensitivity tended to deteriorate during hypoglycemia ( p = 0.06). In conclusion, hypoglycemia impairs important aspects of early visual information processing and contrast sensitivity in adults with type 1 diabetes. Further research is needed to evaluate the functional relevance of such changes for everyday tasks that require the intake of visual information at speed and under conditions of low contrast.