Deficits of spatial localization in children with strabismic amblyopia

Background Besides loss of visual acuity and binocularity, spatial localization deficits (comprising both increased spatial uncertainty and spatial distortions) are an important feature of strabismic amblyopia. Although they have been extensively investigated in adult amblyopes, there are still many open questions concerning their substrate and relationship to clinical parameters. Our aim was to develop a procedure for assessing vertical alignment, which enabled us to find out whether children with strabismic amblyopia had similar spatial localization deficits, and their relation to the childrens clinical condition.Methods Vertical alignment was assessed in children by comparing the visual direction in space of three loci along the vertical meridian, separated by 5 deg of visual angle. We tested alignment in the amblyopic and dominant eyes of 32 strabismic and in both eyes of 35 control children from 4.5 to 10 years, together with a careful orthoptic examination.Results In the amblyopic eyes, increased uncertainty and systematic distortions outside the normal range occurred. Large angles of deviation and pathological fixation patterns were necessary, but not sufficient conditions for gross spatial deficits to occur. The fellow dominant eyes showed spatial localization similar to normal eyes.Conclusions Children with strabismic amblyopia exhibited localization deficits and relationship to clinical data similar to those in adult amblyopes. These data are important for further investigations about the substrate, plasticity and the clinical relevance of perceptual distortions.     

Errors of monocular localization in strabismic amblyopia. Two-dimensional distortion]

Spatial distortions, i.e. spatial localization errors, and precision of localization were measured monocularly in the central visual field of 7 normal observers, 17 strabismic amblyopes and 2 anisometropic amblyopes. The task of the subjects was to construct circles of 2 degrees, 4 degrees and 6 degrees radius around a fixation point, using the dominant and the amblyopic eye in turn. Normal observers set distances on the vertical meridian smaller than distances on the horizontal meridian. Anisometropic amblyopes showed localization errors and variances similar to those of normal observers. The amblyopic eyes of strabismic observers with a large angle strabismus and deep amblyopia showed significant, individually different localization errors correlating with the depth of amblyopia. Strabismics with microstrabismus exhibited parallels between monocular localization and dichoptic retinal correspondence.     

Two-dimensional spatial distortions in human strabismic amblyopia

Two-dimensional space perception was measured in the central visual field of amblyopic subjects under special consideration of spatial distortions and spatial uncertainty. The subjects had to construct circles with different radii around a given fixation point. Subjects with deep strabismic amblyopia were showed to exhibit considerable distortion in the amblyopic eye. Each subject exhibited an individual distortion pattern. The dominant eye showed distortions similar to those seen in normal observers. Subjects with mild strabismic amblyopia, strabismic alternators and anisometropic amblyopes did not exhibit any significant spatial distortions. Data from dichoptic localization experiments indicate that anomalous retinal correspondence might contribute to monocular spatial distortions.     

屈光手术治疗儿童单眼高度近视性弱视的初步报告

目的探讨应用PRK治疗儿童单眼高度近视屈光参差性弱视的可行性、有效性。方法回顾性分析12例5-10岁的儿童单眼高度近视屈光参差性弱视的患儿,对近视度数较高的12眼进行PRK手术治疗,术后再进行系统的脑力影像网络弱视治疗,随访6-12个月。观察手术前后双眼屈光参差差距变化、术眼视力、屈光度、对比敏感度和立体视改善情况。结果手术眼屈光度从术前平均等效球镜-9．77±3．64D降至术后-2．79±2．33D,手术前后屈光度降幅平均为6．98±3．09D。术前双跟屈光参差差距平均为8．65±4．06D,术后双眼屈光参差平均降幅8．25±4．23D。矫正视力从术前0．36±0．24提高到术后的0．45±0．28,术后视力改善的占96．6％,其中提高1行的占36％,提高2行或以上者占62％,未见视力减退病例。在所有术前屈光参差性弱视眼中,2眼术后1个月矫正视力即达到1．0,其他10眼矫正视力均较术前持平或有不同程度改善（提高1-3行）。术后戴镜条件下的对比敏感度和立体视功能与术前持平或有不同程度的改善,其中具有立体视功能的比例从术前的15．3％提高至术后的55．4％。所有病例未见有别于成人PRK的并发症。结论对于单眼高度近视屈光参差性弱视的低龄儿童患者施行PRK手术治疗是一种可选择的安全有效的治疗手段,不仅可以迅速有效地矫正屈光不正,提高视力,而且更为后期弱视治疗提供有利的条件。     

屈光不正性、屈光参差性及斜视性弱视的位置辨别比较

目的比较屈光不正性、屈光参差性及斜视性弱视患者的位置辨别功能差异以及单眼弱视双眼间位置辨别差异。方法选取在广西视光中心就诊的139例(237眼)弱视患者,按弱视类型分为屈光不正性弱视组40例(80眼)、屈光参差性弱视组61例(82眼)、斜视性弱视组38例(75眼),检测3组弱视位置辨别功能并进行比较分析。结果 3组弱视位置辨别功能检测结果均集中在2～4级之间,中位数均为3级,3组位置辨别功能结果比较,差异无统计学意义(Hc=0.530,P>0.05)。单眼弱视双眼位置辨别功能比较,差异无统计学意义(MH=1.837,P>0.05)。单眼弱视眼与双眼弱视眼位置辨别功能比较,差异无统计学意义(Z=-0.588,P>0.05)。结论屈光不正性、屈光参差性及斜视性弱视儿童位置辨别功能不存在差异,单眼弱视双眼位置辨别功能无差异,单眼弱视眼与双眼弱视眼位置辨别功能相似。     

单眼斜视性弱视患者黄斑神经节细胞复合体厚度分析

目的：通过检测单眼斜视性弱视患者双眼黄斑区视网膜神经节细胞复合体厚度,探讨弱视的程度与视网膜神经节细胞厚度的相关性,以及斜视性弱视患者黄斑区神经节细胞复合体结构是否存在异常。
　　方法：选取临床单眼斜视性弱视患者26例52眼。采用美国傅立叶域光学相干断层扫描仪( fourier-domain optical coherence tomography,FD-OCT) iVue同时检测双眼黄斑区神经节细胞复合体厚度,并比较黄斑区神经节细胞复合体厚度与患者最佳矫正视力的相关性。
　　结果：黄斑区神经节细胞复合体厚度( macular ganglion cell complex, mGCC )分为三个区域测量：中心区、内圈(3mm )区、外圈(6mm )区。在斜视性弱视的眼(strabismic amblyopia eye,SAE)测量结果分别是50.74±21.51,101.4±8.51,114.2±9.455μm;在对侧对照眼(contralateral sound eyes,CSE)测量结果分别是43.79±11.92,92.47±25.01,113.3±12.88μm。斜视性弱视眼的黄斑区视神经节细胞复合体厚度与对侧眼相比无显著差异(P>0.05)。最佳矫正视力与黄斑区神经节细胞复合体厚度有相关性,视力矫正越好弱视程度越低的黄斑区神经节细胞复合体厚度相对增厚,黄斑区下方区域的神经节细胞复合体厚度与视力矫正的相关性优于上方。
　　结论：黄斑中心区神经节细胞复合体厚度与弱视矫正视力之间有相关性,虽然mGCC厚度在SAE和CSE无显著差异,但测量mGCC厚度对了解弱视程度有临床意义。     

The electroretinogram in strabismic amblyopia

Summary Neither the studies reported in the literature nor the studies presented in this paper have given evidence of significant or reliable differences in electrical response between the amblyopic and the normal fellow eye. There either are, in fact, no differences, or our technical means are inadequate to uncover them. However, only electrophysiologic studies would seem to be capable of deciding the question whether the retina is or is not involved in the mechanism under-lying amblyopia. It would seem, therefore, worthwhile to attempt further refinements in technique to seek a definitive answer.

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Zusammenfassung Ein zuverl?ssiger Unterschied zwischen dem normalen und dem amblyopischen Auge in Hinsicht auf ihre elektrische Reizbeantwortung konnte in der hier berichteten Untersuchung nicht gefunden werden, noch ergibt sich ein solcher Unterschied aus der diesbezüglichen Literatur. Dies bedeutet entweder, da? Unterschiede tats?chlich nicht bestehen, oder da? wir nicht im Stande sind, sie mit den uns zur Verfügung stehenden Methoden aufzudecken. Die Frage der Mitbeteiligung der Retina an den der Amblyopie zu Grunde liegenden Prozessen kann aber im Prinzip nur durch objektive, elektrophysiologische Methoden gel?st werden. Es ist daher angezeigt, weitere Verfeinerungen der Untersuchungstechnik anzustreben, um die referierten Resultate zu sichern.

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Résumé Ni les travaux rapportés dans la littérature, ni les travaux présentés ici ne mettent en évidence des différences significatives ou valables dans la réponse électrique entre l'oeil amblyope et son congénère normal. Ou bien il n'y a vraiment pas de différences, ou bien nos moyens techniques sont inadéquats à les découvrir. Cependant, seuls des examens électrophysiologiques semblent susceptibles de trancher la question: la rétine est-elle impliquée ou non dans le mécanisme qui est à la base de l'amblyopie? Il semble donc qu'il vaille la peine de rechercher des perfectionnements plus poussés dans la technique pour obtenir une réponse décisive.

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From the ERG laboratory of the Department of Ophthalmology and the Neurosensory Center (Paper No. 78) of the College of Medicine of the University of Iowa. The work of the ERG laboratory is supported by Grant No. B-349; the Neurosensory Center, by Program Project Grant B-3354 of the National Institute of Neurologic Diseases and Blindness, National Institutes of Health, Bethesda, Maryland.     

Image segregation in strabismic amblyopia

Humans with naturally occurring amblyopia show deficits thought to involve mechanisms downstream of V1. These include excessive crowding, abnormal global image processing, spatial sampling and symmetry detection and undercounting. Several recent studies suggest that humans with naturally occurring amblyopia show deficits in global image segregation. The current experiments were designed to study figure-ground segregation in amblyopic observers with documented deficits in crowding, symmetry detection, spatial sampling and counting, using similar stimuli. Observers had to discriminate the orientation of a figure (an "E"-like pattern made up of 17 horizontal Gabor patches), embedded in a 7x7 array of Gabor patches. When the 32 "background" patches are vertical, the "E" pops-out, due to segregation by orientation and performance is perfect; however, if the background patches are all, or mostly horizontal, the "E" is camouflaged, and performance is random. Using a method of constant stimuli, we varied the number of "background" patches that were vertical and measured the probability of correct discrimination of the global orientation of the E (up/down/left/right). Surprisingly, amblyopes who showed strong crowding and deficits in symmetry detection and counting, perform normally or very nearly so in this segregation task. I therefore conclude that these deficits are not a consequence of abnormal segregation of figure from background.     

Impaired spatial and binocular summation for motion direction discrimination in strabismic amblyopia

Amblyopia is characterised by visual deficits in both spatial vision and motion perception. While the spatial deficits are thought to result from deficient processing at both low and higher level stages of visual processing, the deficits in motion perception appear to result primarily from deficits involving higher level processing. Specifically, it has been argued that the motion deficit in amblyopia occurs when local motion information is pooled spatially and that this process is abnormally susceptible to the presence of noise elements in the stimulus. Here we investigated motion direction discrimination for abruptly presented two-frame Gabor stimuli in a group of five strabismic amblyopes and five control observers. Motion direction discrimination for this stimulus is inherently noisy and relies on the signal/noise processing of motion detectors. We varied viewing condition (monocular vs. binocular), stimulus size (5.3-18.5°) and stimulus contrast (high vs. low) in order to assess the effects of binocular summation, spatial summation and contrast on task performance. No differences were found for the high contrast stimuli; however the low contrast stimuli revealed differences between the control and amblyopic groups and between fellow fixing and amblyopic eyes. Control participants exhibited pronounced binocular summation for this task (on average a factor of 3.7), whereas amblyopes showed no such effect. In addition, the spatial summation that occurred for control eyes and the fellow eye of amblyopes was significantly attenuated for the amblyopic eyes relative to fellow eyes. Our results support the hypothesis that pooling of local motion information from amblyopic eyes is abnormal and highly sensitive to noise.     

The effect of increasing doses of levodopa on children with strabismic amblyopia

PURPOSE: The purpose of this study was to determine the efficacy and tolerance of a levodopa/carbidopa combination and to test its dose-effect response when combined with occlusion therapy for children with amblyopia. METHODS: A 1-week randomized, double-blind, parallel, and placebo-controlled study was performed with 78 children with amblyopia aged between 7 and 17 years. Children who weighed less than 40 kg were randomly assigned to receive 5, 10, or 20 mg of levodopa or placebo (3 times a day), and those who weighed 40 kg or more were randomly assigned to receive 10, 20, or 40 mg of levodopa or placebo. Subjects were instructed to occlude the dominant eye (3 h/d). Snellen visual acuity was measured at baseline and at 2 hours after ingestion of the last capsule. Compliance with occlusion and capsule consumption was verified by a questionnaire and counting capsules. Adverse effects were checked with a physical examination and a questionnaire. RESULTS: From baseline to the follow-up test trial, the improvement in the logarithm of the Snellen fraction was 0.05+/-0.11 in the placebo group, 0.18 +/-0.21 in group 1, 0.08+/-0.11 in group II, and 0.16+/-0.15 in group III (P = .031). Visual acuity improved from 0.59 to 0.45 in the levodopa/carbidopa group and from 0.69 to 0.63 in the control group (P = .023). The compliance with occlusion was similar in all groups. No one complained of adverse side effects. CONCLUSION: Levodopa, at an average dose of 0.51 mg/kg per day, is well tolerated and produces a clinical and statistically significant short-term improvement of visual acuity in children with amblyopia.     

儿童单眼外伤性白内障手术后弱视康复的研究

目的探讨儿童单眼外伤性白内障手术后弱视的治疗方法、弱视治疗的时机和双眼视觉功能的康复的方法。方法单眼外伤性白内障的弱视儿童27例，其中男孩21例，女孩6例。年龄3．4～11．7岁，平均7．8岁。手术前视力为光感～0．05，角膜外伤均为非角膜光学区的穿孔伤和光学区内的角膜薄翳。手术方法：自内障的摘出人工晶状体植入，所有斜视者同时进行斜视矫正，手术中或手术后进行散瞳验光，术后3～4周矫正屈光不正，同时进行同视机脱抑制、光刷、光栅及图形刺激等弱视治疗，旁中心注视进行红光后像治疗。手术后1月开始治疗，共治疗6～12月，平均6．5月。结果远视力0．8以上8例，0．3～0．8者9例，0．3以上占62．96％；0．1～〈0．3者5例，0．1以上占81．48％；0．1以下5例。结论儿童单眼外伤性白内障手术要一次解决白内障和其他导致弱视的因素，如斜视；手术后1月进行屈光矫正并开始系统的弱视训练和视觉康复，则大多数能取得较好的疗效。