Mesopic contrast sensitivity functions in amblyopic children

This study both measured and compared the mesopic contrast sensitivity function and the visual acuity in both normal and amblyopic eyes from amblyopic children using an ACV (visual acuity analyzer). Twenty one amblyopic children (mean age, 8.48 years; S.D., 1.68 years), 11 strabismic amblyopes and 10 anisometropic amblyopes, were tested. Based on a display of the standard optotypes, the minimal contrast level, at which the optotypes were correctly read for all sizes of displays from a distance of 1m, was measured. The contrast ranged from 1% to 99% and the spatial frequencies ranged from 0.6 to- 30cpd using a Landolt ring composed of low (0.6- 2.9 c.p.d.), intermediate (3.0 - 12.9 c.p.d.) and high level (13.0- 30.0 c.p.d.) frequencies. As the visual acuity decreased, the mesopic contrast sensitivity function decreased along the contrast sensitivity axis. However, the peak sensitivity was noted at the same spatial frequencies. A comparison between the normal eye and the corresponding amblyopic eye showed that under mesopic conditions, the contrast sensitivity functions decreased more in the intermediate spatial frequencies than in the other spatial frequencies. The mesopic contrast sensitivity function decreased in the amblyopic eyes, which suggests the possibility of its use an adjunct to an evaluation of amblyopia.     

Functional amblyopia in kittens with unilateral exotropia

Summary In two dark reared, 40 day old kittens unilateral divergent squint was induced be resecting the insertion of the medial rectus muscle. Behavioural testing revealed that the kittens used only the normal eye for fixation. Contrast sensitivity functions of the two eyes and visual acuity were determined behaviourally in a jumping stand whereby the kittens had to discriminate sine-wave gratings or variable spatial frequency and contrast from a flux equated homogeneous field. At photopic luminance levels the deviated eye showed a significant deficit in both kittens. This impairment was apparent over the whole range of spatial frequencies (0.18–0.99 c/deg) except for the lowest spatial frequency in one kitten. The interocular difference of visual acuity disappeared at scotopic luminance levels. In subsequent electrophysiological experiments contrast sensitivity functions were determined from cortical evoked potentials that were elicited by phase reversing square wave gratings. Comparison between behavioural and electrophysiological results revealed a very good correspondence between the two sets of data. It is concluded that exotropia without alternating fixation leads to functional amblyopia of the deviated eye.This study was partially supported by a grant from the Deutsche Forschungsgemeinschaft, SFB 50, KybernetikParts of this study were presented at the Meeting of the Physiological Society in Cambridge, England, June 1978, and at the ARVO Meeting in Sarasota, FL, USA, 1979     

Neural site of strabismic amblyopia in cats: spatial frequency deficit in primary cortical neurons

Summary The acuities of cells in the primary visual cortex of five tenotomized strabismic cats were measured. Previous behavioural studies have shown such animals to possess a severe amblyopia of approximately 1.5 octaves of spatial frequency, yet the acuities of both retinal ganglion and lateral geniculate X-cells are normal. The receptive fields of the cortical cells sampled were within 5° of the area centralis projection. On average, the acuities of cortical cells driven by the amblyopic eye were nearly 1 octave less than those for the non-deviating eye. However, the best cell acuities for each eye were nearly the same. The relationship between ocular dominance and cell acuity was found to be different for the two eyes despite a symmetrical ocular dominance distribution. The acuity deficit for cells driven through the amblyopic eye was present at all depths along the electrode tracks. We conclude that in this model amblyopia, the initial spatial processing deficit lies in the visual cortex, and most probably in the cells of layer IV. Further-more, the presence of a few cells driven by the amblyopic eye which can perform nearly as well as those from the fellow eye in processing high spatial frequencies gives new insight into the way in which strabismic and deprivation amblyopias differ.     

Relationship of visual cortex function and visual acuity in anisometropic amblyopic children

Purpose: To detect the functional deficit of the visual cortex in anisometropic amblyopia children using functional magnetic resonance imaging (fMRI) technique, and investigate the relationship between visual acuity and visual cortex function.Methods: Blood oxygenation level-dependent fMRI (BOLD-fMRI) was performed in ten monocular anisometropic amblyopia children and ten normal controls. fMRI images were acquired in two runs with visual stimulation delivered separately through the sound and amblyopic eyes. Measurements were performed in cortical activation of striate and extrastriate areas at the occipital lobe. The relationship between cortex function and visual acuity was analyzed by Pearson partial analysis.Results: The activation areas of both the striate and extrastriate cortices in the amblyopic eyes were significantly lower than that of the sound fellow eyes. No relationship was found between the striate and extrastriate cortex activation. No relationship was found between the visual cortical activation of striate, extrastriate areas and visual acuity of anisometropic amblyopes.Conclusions: BOLD-fMRI revealed the independent striate and extrastriate cortical deficits in anisometropic amblyopes. In addition, the visual acuity lesion and the striate and extrastriate cortical deficits were not parallel, and results of fMRI examination have much potential value in the evaluation of amblyopia.     

Retinotopic maps and foveal suppression in the visual cortex of amblyopic adults

Amblyopia is a developmental visual disorder associated with loss of monocular acuity and sensitivity as well as profound alterations in binocular integration. Abnormal connections in visual cortex are known to underlie this loss, but the extent to which these abnormalities are regionally or retinotopically specific has not been fully determined. This functional magnetic resonance imaging (fMRI) study compared the retinotopic maps in visual cortex produced by each individual eye in 19 adults (7 esotropic strabismics, 6 anisometropes and 6 controls). In our standard viewing condition, the non-tested eye viewed a dichoptic homogeneous mid-level grey stimulus, thereby permitting some degree of binocular interaction. Regions-of-interest analysis was performed for extrafoveal V1, extrafoveal V2 and the foveal representation at the occipital pole. In general, the blood oxygenation level-dependent (BOLD) signal was reduced for the amblyopic eye. At the occipital pole, population receptive fields were shifted to represent more parafoveal locations for the amblyopic eye, compared with the fellow eye, in some subjects. Interestingly, occluding the fellow eye caused an expanded foveal representation for the amblyopic eye in one early–onset strabismic subject with binocular suppression, indicating real-time cortical remapping. In addition, a few subjects actually showed increased activity in parietal and temporal cortex when viewing with the amblyopic eye. We conclude that, even in a heterogeneous population, abnormal early visual experience commonly leads to regionally specific cortical adaptations.     

Behavioural studies of spatial vision in cats reared with convergent squint: Is amblyopia due to arrest of development?

Summary Visual acuity and contrast sensitivity were measured behaviourally in normal adult cats and cats reared with monocular convergent squint from 3, 6, 8, 12, and 24 weeks of age. The visual acuity of the squinting eye was significantly lower than that of the non-squinting eye in cats with squint from 3, 6, and 8 weeks of age. No significant difference in acuity between eyes was found in the 12- and 24-week squinting cats and in the controls.Contrast thresholds at all spatial frequencies tested (range 0.13–2.0 c/ °) were higher in the squinting eye than in the non-squinting eye of cats with squint from 3 and 6 weeks of age, but differences were greater at the higher spatial frequencies. In the 8-week squinting cat, contrast thresholds were increased only at higher spatial frequencies. No significant differences in contrast sensitivity were found in the cat with squint from 24 weeks of age and in the controls.The degree of disturbance of spatial vision in squinting cats was most related to the age at onset of the squint, i.e., the earlier the onset, the more profound the amblyopia. The period of susceptibility extended from about 3 to 12 weeks of age. When compared with data on the development of visual acuity in kittens, the pattern of results from the present study suggests that convergent squint can arrest the development of spatial vision.This work was supported by the M. R. C.     

Visual functions after laser photocoagulation in central serous chorioretinopathy

The authors evalute the visual functions of patients with unilateral central serous chorioretinopathy (CSC) and compare them with their non-affected eye and with a control group. Fourteen patients with CSC treated with direct laser-photocoagulation were examined preoperatively and followed-up, up to 2 years postoperatively. Baseline best corrected visual acuity (BCVA) and contrast sensitivity (CS) of both eyes of patients was significantly lower in comparison with the controls. BCVA and CS in affected eyes were significantly lower compared to the fellow eye of patients. The final BCVA and CS of patients did not differ significantly from the controls, except CS of affected eyes in the spatial frequency of 3.69 c/deg. Two years after laser treatment, there were only nonsignificant differences of both photopic full-field electroretinography (phERG) and multifocal electroretinography (mfERG) responses between the treated, the nonaffected eye of the patients and the control group with exception of a significantly longer P1 implicit time in the parafoveolar region in affected eyes. Colour discrimination was normal in 85.8% of affected eyes of the patients. Despite a significant improvement of macular function in CSC eyes, functional examination methods do not prove complete resolution of function 2 years after laser-treatment.     

Visual acuity in the blue cone monochromat

1. To isolate the blue cones of the normal eye, blue sine-wave gratings were superimposed on a bright yellow background. Threshold contrasts for resolution of the gratings were then determined.2. Under these conditions visual acuity for high contrast gratings on four normal subjects was on the average 0.31 min(-1). This is about a factor of 6 lower than grating acuity under optimal conditions.3. The contrast sensitivity of two subjects who lack the normal red and green receptor mechanisms was measured using blue sinusoidally modulated gratings. Visual acuity was found to be greatly reduced from normal. The low acuity of these individuals is due to both a reduction in contrast sensitivity and a reduction in resolution.4. The spatial resolving characteristics of these subjects resembles the vision of the normal eye under conditions which isolate the blue sensitive mechanisms.5. The vision of the cone monochromat differs significantly from that of the more typical rod monochromat. The rod monochromat has even lower acuity than the blue cone monochromat for high contrast gratings but has much greater contrast sensitivity for gratings of low spatial frequency.     

BOLD fMRI response of early visual areas to perceived contrast in human amblyopia

In this study, we used a temporal two-alternative forced choice psychophysical procedure to measure the observer's perception of a 22% physical contrast grating for each eye as a function of spatial frequency in four subjects with unilateral amblyopia and in six subjects with normal vision. Contrast thresholds were also measured using a standard staircase method. Additionally, blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) was used to measure the neuronal response within early visual cortical areas to monocular presentations of the same 22% physical contrast gratings as a function of spatial frequency. For all six subjects with normal vision and for three subjects with amblyopia, the psychophysically measured perception of 22% contrast as a function of spatial frequency was the same for both eyes. Threshold contrast, however, was elevated for the amblyopic eye for all subjects, as expected. The magnitude of the fMRI response to 22% physical contrast within "activated" voxels was the same for each eye as a function of spatial frequency, regardless of the presence of amblyopia. However, there were always fewer "activated" fMRI voxels during amblyopic stimulation than during normal eye stimulation. These results are consistent with the hypotheses that contrast thresholds are elevated in amblyopia because fewer neurons are responsive during amblyopic stimulation, and that the average firing rate of the responsive neurons, which reflects the perception of contrast, is unaffected in amblyopia.     

Abnormal orientation selectivity in both eyes of strabismic amblyopes

Summary In normal observers preadaptation to a parallel grating increases the contrast threshold for a line whereas a perpendicular grating has no effect. Such orientation selectivity was not found in the amblyopic eye of two out of five squinters. Only a weak after-effect produced with a grating parallel to the line was obtained in the good eye of four of the amblyopes while all of them show an abnormal threshold reduction following adaptation to a perpendicular grating. This suggests a relationship between abnormal binocular interaction during visual development and the organization of orientational mechanisms but does not explain the loss of visual acuity in amblyopia.     

Acute effect of alcohol intake on sine-wave Cartesian and polar contrast sensitivity functions

The aim of this study was to assess contrast sensitivity for angular frequency stimuli as well as for sine-wave gratings in adults under the effect of acute ingestion of alcohol. We measured the contrast sensitivity function (CSF) for gratings of 0.25, 1.25, 2.5, 4, 10, and 20 cycles per degree of visual angle (cpd) as well as for angular frequency stimuli of 1, 2, 4, 24, 48, and 96 cycles/360°. Twenty adults free of ocular diseases, with normal or corrected-to-normal visual acuity, and no history of alcoholism were enrolled in two experimental groups: 1) no alcohol intake (control group) and 2) alcohol ingestion (experimental group). The average concentration of alcohol in the experimental group was set to about 0.08%. We used a paradigm involving a forced-choice method. Maximum sensitivity to contrast for sine-wave gratings in the two groups occurred at 4 cpd sine-wave gratings and at 24 and 48 cycles/360° for angular frequency stimuli. Significant changes in contrast sensitivity were observed after alcohol intake compared with the control condition at spatial frequency of 4 cpd and 1, 24, and 48 cycles/360° for angular frequency stimuli. Alcohol intake seems to affect the processing of sine-wave gratings at maximum sensitivity and at the low and high frequency ends for angular frequency stimuli, both under photopic luminance conditions.     

Unmasking the dichoptic mask by sound: spatial congruency matters

People tend to look toward where a sound occurs; however, the role of spatial congruency between sound and sight in the effect of sound facilitation on visual detection remains controversial. We propose that the role of spatial congruency depends on the reliability of the information provided by the facilitator; if it is relatively unreliable, adding spatially congruent information can help to unify different sensory inputs to compensate for this unreliability. To test this, we examine the influence of sound location on visual detection with a non-temporal task, presumably unfavorable for sound since it is better for temporal resolution, and predict that spatial congruency should matter in this situation. We used the continuous flash suppression paradigm that makes the visual stimuli invisible to keep the relationship of sound and sight opaque. The sound is on the same depth plane as the visual stimulus (the congruent condition) or on a different plane (the incongruent condition). The target was presented to one eye with luminance contrast gradually increased and continuously masked by flashed Mondrian masks presented to the other eye until the target was released from suppression. We found that sound facilitated visual detection (measured by released-from-suppression time) in the spatially congruent condition but not in the spatially incongruent condition. Together with previous findings in the literature, it is suggested that both task type and modality determine the reliability of the information for multisensory integration and thus determine whether spatial congruency is critical.     

Visual resolution,contrast sensitivity,and the cortical magnification factor

Summary This study shows that photopic contrast sensitivity and resolution can be predicted by means of simple functions derived by using the cortical magnification factor M as a scale factor of mapping from the visual field into the striate cortex. We measured the minimum contrast required for discriminating the direction of movement or orientation of sinusoidal gratings, or for detecting them in central and peripheral vision. No qualitative differences were found between central and peripheral vision, and almost all quantitative differences observed could be removed by means of a size compensation derived from M.The results indicated specificly that (1) visual patterns can be made equally visible if they are scaled so that their calculated cortical representations become equivalent; (2) contrast sensitivity follows the same power function of the cortical area stimulated by a grating at any eccentricity; (3) area and squared spatial frequency are reciprocally related as determinants of contrast sensitivity; and (4) acuity and resolution are directly proportional to M, and the minimum angle of resolution is directly proportional to M^-1.The power law of spatial summation expressed in (2) and (3) suggests the existence of a central integrator that pools the activity of cortical neurons. This summation mechanism makes the number of potentially activated visual cells the most important determinant of visibility and contrast sensitivity. The functional homogeneity of image processing across the visual field observed here agrees with the assumed anatomical and physiological uniformity of the visual cortex.     

雷珠单抗治疗湿性年龄相关性黄斑变性的视力改善与黄斑形态学变化相关性分析

目的 分析雷珠单抗治疗湿性年龄相关性黄斑变性的视力改善和黄斑形态学变化之间的相关性。方法 选取2014年1月~2016年2月在西安交通大学第一附属医院行雷珠单抗治疗的湿性年龄相关性黄斑变性患者43例（1眼/例）。观察治疗前后最佳矫正视力（BCVA）、黄斑中心凹厚度（CMT）及黄斑病变面积。分析视力改善与黄斑形态学变化之间的相关性。结果 治疗3个月后,BCVA升高字母数（8.93±5.70）个,CMT下降（115.35±56.24）μm,黄斑病变面积减少（2.04±0.65）mm2。治疗3个月后,BCVA变化与CMT变化之间无相关性（r=-0.170,P＞0.05）;BCVA变化与黄斑病变面积改变之间无相关性（r=-0.101,P＞0.05）。结论 雷珠单抗治疗湿性AMD具有较好疗效,提高患者视力,改善黄斑形态学,视力改善与黄斑形态学变化之间无相关性。     

Amblyopia occurs in retinal ganglion cells in cats reared with convergent squint without alternating fixation

Summary The spatial resolving power, contrast sensitivity, and receptive field properties of retinal ganglion cells were studied in cats reared with either convergent or divergent squint in one eye. Sustained-X cells in the area centralis of the squinting eye of the cats with esotropia without alternating fixation showed significantly poorer spatial resolution, and reduced contrast sensitivity compared with cells in the area centralis of the normal eye. These amblyopic sustained-X cells in the area centralis of the squinting eye had receptive field characteristics similar to those found in immature cells of young kittens. They had a shallow sensitivity gradient within a relatively widespread centre zone and a weak and widespread inhibitory surround. In contrast, the sustained cells in the area centralis of the normal eye revealed a typical, well defined, small centre zone with its sensitivity gradient extremely steep and its inhibitory surround strong and confined. A minor degree of amblyopia was also found in transient Y-cells in the area centralis of the squinting eye of these cats.However, no loss of resolving power was found in the cells in the area centralis of the squinting eye of the cats with esotropia or exotropia which showed alternating fixation. Thus, amblyopia occurs in those eyes which have lost the use of the area centralis as the normal visual axis during early postnatal development, and its organic lesion is already apparent in the retinal ganglion cells — the third order neurone in the afferent visual system. It is suggested that the loss of the ability to fixate results in inadequate stimulation of the central retinal ganglion cells due to the habitual presence of blurred images at the area centralis which prevents their full development during the critical period.This work was supported by grants from MRC and St. Thomas's Hospital to H. Ikeda     

Edge sensitive mechanisms in humans with abnormal visual experience

Summary Detection of broadband, aperiodic stimuli (edges) was investigated in normal observers, and in observers with abnormal visual experience which resulted in amblyopia. The spatial properties of the mechanisms used to detect an edge were investigated by a method of subthreshold addition. The method involved the determination of the threshold contrast for detecting an edge in the presence of a subthreshold line at various distances from the edge. In normal eyes, the one dimensional sensitivity profile of the edge detecting mechanism was: (1) approximately antisymmetric, (2) very localized, with sensitivity changes restricted to ±6'–8' on either side of the edge, and (3) phase dependent, showing an abrupt change in sign between ±1.5'. The sensitivity profiles of the amblyopic eyes were also approximately antisymmetric and showed the same steep rate of change from plus to minus as the fellow (nonamblyopic) eyes. However, in every case, the spatial extent of the profile was much broader than that of the nonamblyopic eyes. In normal eyes, the narrowest edge sensitivity profile was associated with the fovea; however, in two amblyopes with eccentric fixation, the narrowest edge sensitivity profile coincided with the locus of eccentric fixation. Moreover, the grating sensitivity function of the edge detecting mechanism of the amblyopic eye was similar to that of the non-amblyopic eye, but was shifted toward lower spatial frequencies. Control experiments show that these results are not accounted for on the basis of optics, eccentric fixation, or abnormal eye movements. The findings are discussed in terms of current models for the detection of aperiodic stimuli, and in the context of animal models of amblyopia.This work was supported by Research Grants from the National Eye Institute (Bethesda, Md.) R01EY01278 and R01EY01139     

改良深板层角膜移植治疗圆锥角膜屈光状态的改变及相关因素*

背景：传统深板层角膜移植治疗圆锥角膜后弹力层穿孔率较高。 目的：观察改良深板层角膜移植治疗圆锥角膜后屈光状态的长期改变及相关因素分析。 方法：采用改良深板层角膜移植法治疗46例(51眼)圆锥角膜患者,记录移植前后裸眼视力和最佳矫正视力;移植前按平均角膜曲率大小分为两组,平均角膜曲率≥60 m-1组与<60 m-1组,观察移植后24个月的等效球镜、散光、角膜曲率,并分析眼轴与术后屈光状态的相关性。 结果与结论：与移植前比较,移植后1,6,12,18,24个月的裸眼视力及最佳矫正视力均有显著提高(P < 0.01或P < 0.05),移植后6个月内视力是显著提高的,6~18个月视力虽有一定的提高,但基本是处于稳定的趋势,18~24个月视力显著提高,显示随 着移植后时间的延长,视力逐渐提高并趋于稳定,说明改良深板层角膜移植后长期疗效佳。两组移植后的等效球镜、移植后散光、平均角膜曲率均较移植前明显改善,但两组间差异均无显著性意义(P > 0.05),眼轴与移植后的等效球镜、裸眼视力、角膜散光有一定的负相关性。说明改良深板层角膜移植后等效球镜向近视方向移动,角膜散光逐渐减小,平均角膜曲率逐渐增大。移植前角膜曲率差异对改良深板层角膜移植后屈光状态无明显影响。眼轴与术后屈光状态有一定的相关性。     

夜戴型角膜塑形镜对视力、屈光度、眼轴及泪膜影响研究

目的 探讨夜戴型角塑形镜对青少年近视眼视力、屈光度、眼轴、泪膜的影响。方法 随机选取我院佩戴角膜塑形镜患者60例（116眼）,比较戴角膜塑形镜前与戴镜后1周、1个月、3个月、6个月和1年视力、屈光度、眼轴及泪膜变化。结果 戴角膜塑形镜1周裸眼视力较戴镜前提高[（0.45±0.07）vs（0.43±0.07）],差异有统计学意义（P＜0.05）;平均屈光度较戴镜前下降[（180.71±35.99）D vs（182.86±36.65）D],泪膜破裂时间较戴镜前缩短[（7.71±0.74）s vs（7.99±0.65）s],差异有统计学意义（P＜0.05）;眼轴较戴镜前未见明显变化（P＞0.05）;其后戴角膜塑形镜1个月、3个月、6个月和1年分别与戴镜前比较,视力、屈光度、眼轴及泪膜变化均呈稳定趋势。结论 角膜塑形镜可控制近视度数并提高裸眼视力,延缓视轴增长,对青少年近视控制效果明显,泪膜损伤小,安全可靠。     

Chlorogenic Acid Supplementation Improves Multifocal Electroretinography in Patients with Retinitis Pigmentosa

To evaluate the effect of chlorogenic acid supplementation in patients with retinitis pigmentosa, we evaluated objective change in visual function with multifocal electroretinography, along with visual acuity, visual field, standard electroretinography, and contrast sensitivity. Eighteen patients diagnosed with retinitis pigmentosa were enrolled in this prospective, non-comparative, single-arm study. Multifocal electroretinography, best-corrected visual acuity in Early Treatment Diabetic Retinopathy Study letters, total point score on visual field examination with Humphrey Field Analyzer II, electroretinography, and contrast sensitivity were measured and repeated after 3 months supplementation with chlorogenic acid. The amplitude of ring 5 was significantly higher on multifocal electroretinography after 3 months of chlorogenic acid supplementation (7.2 ± 9.5 vs 8.3 ± 10.8 nV/deg², mean ± standard deviation, P = 0.022). There were no significant changes in the best-corrected visual acuity, total point score on Humphrey Field Analyzer, 30 Hz flicker amplitude on standard electroretinography, or contrast sensitivity. Chlorogenic acid may have a beneficial effect on the peripheral area at the margins of retinal degeneration, and should be considered as an anti-oxidant for the management of retinitis pigmentosa.     

A cat's form-experienced but visual-motor deprived eye lacks focal vision

Cats were allowed to move about freely from birth to 18 months with one eye open; the other eye was open during daily 1-hr periods of binocular exposure in a holder, but was deprived of all visual-motor experience. Focal vision failed to develop in the deprived eye (DE): (1) the DE's guidance deficit was especially pronounced for targets in the central field and in the photopic light range (it was much smaller in the periphery and in the mesopic range); (2) conjugate eye control, required for binocular fixation of objects in focal viewing, was disrupted by strabismus (squint); and (3) focal vision's identification function was virtually absent in the DE—it showed only slight recognition of patterns learned by the experienced eye (EE) and little ability to learn to identify them itself.