Evaluating reading acuity and speed in children with microstrabismic amblyopia using a standardized reading chart system

Background To examine if standardized reading charts with highly comparable test items can be used for evaluating impairments in the monocular reading performance of children with microstrabismic amblyopia characterized by a small angle of squint with less than 5 degrees. Methods The reading performance of 22 children (mean age: 11.7±1.6 years) with unilateral microstrabismic amblyopia was evaluated monocularly in both eyes, using standardized reading charts for the simultaneous determination of reading acuity and speed. The print sizes of the highly comparable sentence optotypes were logarithmically graded, providing constant geometric proportions for all testing distances in order to control contour interaction. All children were under continuous amblyopia therapy. Results In the amblyopic eyes, reading acuity and maximum reading speed were significantly impaired when compared to the sound fellow eyes (P<0.001). In respect of the maximum reading speed, a mean inter-ocular difference of 33±19 words per minute was found, revealing functionally relevant deficits in monocular reading performance. The amblyopic eyes achieved only a significantly reduced reading acuity (mean inter-ocular difference: LogRAD 0.5±0.24; P<0.001). In eight children, the amblyopic eyes achieved a best-corrected visual acuity of LogMAR 0.0 or better: in respect of the visual acuity, there was no significant inter-ocular difference, but reading acuity and maximum reading speed were significantly impaired when compared to the fellow eyes. Conclusions Microstrabismic amblyopia was associated with significant impairment of reading acuity and speed in treated amblyopes, even in those with no persistent acuity deficit. To improve treatment addressing these functional deficits, reading performance should be monitored over time using standardized reading tests, which provide essential information about functionally relevant reading impairments. Supported by the “Medizinisch-Wissenschaftlicher Fonds des Bürgermeisters der Bundeshauptstadt Wien” and Alcon None of the authors has any commercial interest in any of the materials or methods mentioned     

不同程度弱视儿童双眼视差信息的变化

目的 评估弱视儿童的双眼视差信息改变。设计 前瞻性病例系列。研究对象 眼位正常的轻度、中度、重度弱视儿童,各30例。方法 应用基于计算机平台的视感知觉检查方法对弱视儿童的双眼视差信息进行量化检测。分别测定随机点0阶视差、线条0阶视差、2阶视差、随机点动态1阶视差。主要指标 视差测量值或通过百分比。结果 轻度、中度、重度弱视儿童随机点0阶视差达100＂的比例分别为43.3%、16.7%、0%（χ2=25.550,P=0.000）;线条0阶视差达100＂的比例分别为83.3%、50.0%、13.3%（χ2=30.835,P=0.000）,2阶视差正确率达100＂的比例分别为86.7%、80.0%、40.0%（χ2=22.144,P=0.000）,随机点动态1阶视差低速通过者的比例分别为80.0%、50.0%、13.3%（χ2=27.379,P=0.000）。结论 眼位正位的弱视儿童其双眼视差信息均存在异常,弱视程度越深,异常越严重。     

Monocular symmetry in binocular vision

Human vision is highly sensitive to bilateral symmetry in 2-D images. It is, however, not clear yet whether this visual sensitivity relates to symmetry of 3-D objects or whether it relates to symmetry of the 2-D image itself. We used a stereoscopically presented stimulus and a 3-D bisection task that enable us to dissociate object symmetry from image symmetry. The bisection stimulus consisted of three parallel lines, of which two lines were located in one depth plane and the third line in another. Bisection judgments were different for horizontal and vertical lines, which can be explained by taking into account the distinct viewpoints of the left and right eyes for either of the visible sides of the 3-D object. Image symmetry from a monocular vantage point predicts 3-D bisection better than object symmetry. We conclude that observers use either of the two monocular 2-D images separately but not a single cyclopean view-nicely dovetailing with what they do when they assess both 3-D visual direction and 3-D shape-to assess 3-D symmetry.     

Fixation patterns evaluation by means of MP-1 microperimeter in microstrabismic children treated for unilateral amblyopia

PURPOSE: The aim of the study was to evaluate the fixation patterns of microstrabismic children previously treated for unilateral amblyopia. METHODS: Thirty-three children (mean age 7.3+/-1.5 years) were included in the study. Visual acuity (VA) was measured using the Early Treatment of Diabetic Retinopathy Study charts. Fixationwas assessed by MP-1 microperimeter. Differences in position and stability of fixation between the fellow and the microstrabismic eyes were calculated by using the percentage of the preferred fixation points within central fixation and the percentage of the fixation points within target fixation, respectively. For statistical analysis Mann-Whitney test was used. To evaluate the influence of age and duration of anti-amblyopic treatment on microstrabismic eyes fixation, linear regression analysis was performed. RESULTS: In the microstrabismic eyes VA was significantly reduced when compared to the fellow eyes (0.1236+/-0.0204 vs 0.0042+/-0.0032 logMAR; p<0.001). Position and stability of fixation were significantly better in the fellow eyes (93.21+/-0.65% vs 70.91+/-4.80%; p=0.002, and 89.88+/-0.94% vs 71.73+/-2.94%; p<0.001, respectively). A significant correlation was found between fixation stability and both the duration of anti-amblyopic treatment and pretreatment VA (p=0.024 and p=0.009, respectively) and between fixation centrality and pretreatment VA (p<0.001). CONCLUSIONS: VA, centrality, and stability of fixation were significantly impaired in the microstrabismic eyes. Pretreatment VA was a risk factor for fixation impairment. The severity of fixation stability impairment was linked to the duration of anti-amblyopic treatment.     

屈光参差性弱视儿童的双眼视功能

目的观察屈光参差性弱视儿童的双眼视功能以及屈光参差中立体视和融像之间的关系。方法选择隐性斜视小于4△的5～12岁屈光参差儿童46例。对以上所选病例．测定最佳矫正视力、屈光状态及矫正后TNO立体视及Worth四点、Bagolini线状镜、4D三棱镜检查。并对测量数据进行统计学分析。结果Bagolini线状镜检查中所有患者均有融像功能：Worth四点检查中近距39例有融像．远距22例患者有融像：TNO立体视检查中37例视锐度值下降．其中19例无立体视。4D三棱镜检查中34例有中心抑制暗点．融像功能减弱与立体视锐度下降、屈光参差程度及弱视程度有关，弱视与立体视的相关性大于屈光参差与立体视的相关性。立体视锐度与融像能力的强弱有关。结论双眼视功能随着屈光参差程度和弱视程度的增加而下降。融像功能检查中．Bagolini线状镜提示融合状态，Worth四点提示融合强度。中心抑制暗点可能是导致立体视和双眼视功能下降的原因。     

屈光参差性弱视患儿遮盖调节对双眼视功能的影响

目的：探讨屈光参差性弱视患儿遮盖调节对双眼视功能的影响。方法：选取2014－07／2015－04在我院医治的屈光参差性弱视患儿45例作为研究组,应用遮盖治疗,同期选取40例志愿健康者作为空白对照组,观察受试者的双眼视功能情况。结果：遮盖治疗前、治疗1、3 mo双眼融合正常率分别为62％、76％和87％,治疗3 mo显著高于治疗前（ P＜0．05）,治疗1mo同治疗前差异不明显（ P＞0．05）;遮盖治疗前、治疗1、3mo后立体视3000＂～801＂的患儿分别有26、13和2例;800＂～401＂的患儿分别有12、13和6例;400＂～101＂的患儿分别有7、15和25例;≤100＂者分别为0、4和12例;研究组远距散开破裂点和辐辏功能治疗后均明显提升且高于对照组（ P均＜0．05）;近距散开和辐辏功能破裂点、模糊点均较治疗前明显上升（均P＜0．05）,散开功能破裂点、模糊点均高于对照组,辐辏功能中则低于对照组（均P＜0．05）;治疗后研究组双眼调节幅度、灵敏度均较治疗前显著提高（均P＜0．01）;双眼调节幅度显著低于对照组（均 P＜0．01）,调节灵敏度与对照组无差异（P＞0．05）;遮盖治疗后双眼调节滞后量较治疗前明显下降（ P＜0．05）,但同对照组相比无明显差异（P＞0．05）;研究组45例90眼治愈52眼;进步24眼,无效14眼;治疗总有效率为84％。结论：屈光参差性弱视患儿遮盖调节对双眼视功能有一定改善。     

Detection of amblyopia and development of binocular vision in infants and children

Studies of visual development indicate that rapid changes occur in the first months of life and that it is during this period that the visual system is prone to aberrant development. The call for visual screening of children younger than 3 years of age is sensible in light of recent research findings. For children with visual problems, some recovery of visual function can occur if treatment is begun early. New tests of stereoacuity and vernier acuity may aid in the diagnosis of amblyopia, which is underestimated by grating acuity measures. Electrophysiologic testing, using visual evoked potentials and electroretinograms, is helpful in diagnosing visual problems at an early age.     

Monocular and binocular optokinetic nystagmus in humans with defective stereopsis

In order to investigate the previously suggested relation between cortical binocular function and deficits in monocular optokinetic nystagmus (OKN), monocular and binocular OKN was examined in normal, stereodeficient, and stereoblind observers, using a variety of stimulation velocities and stimulus field sizes. Most stereodeficient and stereoblind observers showed monocular OKN deficits in one or both eyes, which took the form of either a directional asymmetry or a reduction of the response in both directions. The deficits were often more pronounced at higher stimulation velocities and with smaller stimulus field sizes. The severity of the OKN deficit was related to the degree of residual foveal stereopsis, while the type of the deficit seemed to be influenced by the presence and depth of amblyopia. Binocular OKN resembled the best monocular response in subjects with a directional or ocular asymmetry. The results fit well with current animal models of the neural control of OKN.     

间断遮盖治疗儿童弱视对视功能发育影响

目的 观察间断遮盖治疗对弱视患儿双眼视功能发育的影响.方法 对70例经治疗后双眼矫正视力均达0.9以上的弱视患儿行双眼视功能检查.测量同时视、融合范围及远近立体视.根据治疗过程中是否有遮盖史将患儿分为A(遮盖组)、B(不遮组)两组.统计A、B两组同时视、融合和立体视差异.结果 遮盖组中存在同时视的42人(91.3％),集合融合范围正常的2人(4.3％),分开融合范围正常的36人(78.3％),有正常远立体视的15人(32.6％),有正常近立体视的6人(13.0％).不遮组中存在同时视的23人(95.8％),集合融合范围正常的1人(4.2％),分开融合范围正常的17人(70.8％),有正常远立体视的10人(41.7％),有正常近立体视的3人(12.5％).70例患儿中存在正常远近立体视的各为25人(35.7％)、7人(10.0％).同时视在两组患儿之间的差异无统计学意义(x2=0.041,P=O.839);集合性融合和分开性融合在两组患儿之间的差异也无统计学意义(x2=0.156,P=0.693; x2=0.473,P=0.492);远近立体视两组患儿差异也均无统计学意义(x2=0.564,P=0.453;x2=0.004,P=0.949); 70例患儿正常远、近立体视获得率之间的差异具有统计学意义(x2=13.125,P=0.000).结论 弱视治疗后矫正视力正常的患儿短期内双眼视功能仍未完全恢复正常.间断遮盖优势眼治疗弱视不会对患儿双眼视功能发育造成显著的影响.     

常规戴镜和遮盖治疗对单、双眼弱视儿童屈光状态的影响

目的 探讨单眼及双眼弱视患儿通过常规戴镜和遮盖治疗,弱视达基本治愈后屈光状态的变化规律,以探讨弱视眼的正视化特征.方法 回顾性连续观察远视性屈光不正性弱视治愈病例1～10 a共56例(112眼)患者,初诊年龄(5.71±1.67)岁,观察终点年龄(8.77±2.28)岁,平均观察(3.07±1.79)a.选择等效球镜≥+3.00 D的弱视患儿.单眼弱视组弱视眼(38眼)给予所谓健眼遮盖、戴镜联合精细目力训练治疗;双眼弱视组(36眼)给予戴镜及精细目力训练治疗,所谓健眼组38眼未做任何处理.随访观察各组病例屈光度(球镜、柱镜)变化及初诊年龄、治愈年龄、治疗周期分布特点等.结果 单眼弱视组:基本治愈年龄(8.34±2.15)岁,球镜度数平均每年减少(0.46±0.42)DS,柱镜度数减少(0.016±0.143)DC;所谓健眼组每年球镜度数减少(0.28±0.62)DS,柱镜度数减少(0.003±0.067)DC.双眼弱视组:基本治愈年龄(9.67±2.34)岁,球镜度数平均每年减少(0.40±0.32)DS,柱镜度数减少(-0.056±0.237)DC.3组球镜度数及柱镜度数平均每年变化值组间比较,差异均无统计学意义(P＞0.05);所谓健眼组等效球镜数平均每年减少度数与其他2组比较,差异均有统计学意义(均为P＜0.05).单眼弱视组的球镜度数与疗程呈负相关(r=0.428,P＜0.01).结论 常规戴镜和遮盖治疗可减慢单眼弱视所谓健眼的正视化进程,但对弱视眼无显著影响;常规戴镜治疗对双眼弱视眼正视化进程也无明显影响.     

Pathophysiology of binocular vision and amblyopia

This article focuses on three important issues that have received much attention during the past year. The first is sensitive periods for amblyopia. Recent physiological studies suggest a surprising degree of neural plasticity in the adult visual cortex. A review of the literature suggests that at least some human amblyopes retain cortical plasticity into adulthood. The second issue is new methods of treatment for amblyopia. Certain neurotransmitters have been implicated in neuronal plasticity. Based on this finding, a potentially promising new method for treating amblyopia, levodopa, is being tested in adults and children with amblyopia. Unfortunately the early results provide more questions than answers. The third topic is neural mechanisms of amblyopia. In primates and humans, the weight of evidence suggests that the neural effects of strabismus and anisometropia are expressed primarily in the cortex. These cortical effects are expressed in a loss of cortical neurons and in alterations in the contrast sensitivity and range of preferred spatial frequencies of the neurons dominated by the amblyopic eye. The relationship between these physiological effects and psychophysical performance is reviewed.     

OKN asymmetries and binocular function in amblyopia

Asymmetrical optokinetic nystagmus (OKN) means that OKN has a lower gain (slow-phase eye velocity/stimulus velocity) for monocular temporalward than nasalward visual field motion. OKN tends to be asymmetric in amblyopia, leading to suggestions of a link between OKN asymmetry and binocularity in the literature. The present study measured OKN in 13 amblyopes and five normal subjects. In an attempt to identify those binocular cells used in the OKN response, the degree of OKN asymmetry was compared with binocularity assessed by two different techniques: (1) stereopsis and (2) interocular transfer of threshold elevation (IOT). Horizontal monocular OKN was recorded for three different stimulus velocities in each subject. All the amblyopes were found to be stereoblind, although three amblyopes showed OKN asymmetries close to those found for the normal group. More association was seen between interocular transfer of the threshold elevation and OKN asymmetry; not all amblyopes demonstrated reduced IOT, but those amblyopes with no IOT all had OKN asymmetries more than 125% of the mean of the normal group. However, no association was seen between the amount of OKN asymmetry and the degree of IOT. The results are discussed in terms of the role of different groups of binocular neurones for OKN and the effect of the sensitive periods of development on these binocular neurones.     

Monocular and binocular depth discrimination thresholds.

BACKGROUND: Measurement of stereoacuity at varying distances, by real or simulated depth stereoacuity tests, is helpful in the evaluation of patients with binocular imbalance or strabismus. Although the cue of binocular disparity underpins stereoacuity tests, there may be variable amounts of other binocular and monocular cues inherent in a stereoacuity test. In such circumstances, a combined monocular and binocular threshold of depth discrimination may be measured--stereoacuity conventionally referring to the situation where binocular disparity giving rise to retinal disparity is the only cue present. A child-friendly variable distance stereoacuity test (VDS) was developed, with a method for determining the binocular depth threshold from the combined monocular and binocular threshold of depth of discrimination (CT). METHODS: Subjects with normal binocular function, reduced binocular function, and apparently absent binocularity were included. To measure the threshold of depth discrimination, subjects were required by means of a hand control to align two electronically controlled spheres at viewing distances of 1, 3, and 6m. Stereoacuity was also measured using the TNO, Frisby, and Titmus stereoacuity tests. BTs were calculated according to the function BT= arctan (1/tan alphaC - 1/tan alphaM)(-1), where alphaC and alphaM are the angles subtended at the nodal points by objects situated at the monocular threshold (alphaM) and the combined monocular-binocular threshold (alphaC) of discrimination. RESULTS: In subjects with good binocularity, BTs were similar to their combined thresholds, whereas subjects with reduced and apparently absent binocularity had binocular thresholds 4 and 10 times higher than their combined thresholds (CT). The VDS binocular thresholds showed significantly higher correlation and agreement with the TNO test and the binocular thresholds of the Frisby and Titmus tests, than the corresponding combined thresholds (p = 0.0019). CONCLUSION: The VDS was found to be an easy to use real depth (distance) stereoacuity test. The method described for calculating the BT provides one simple nonlinear solution for determining the respective contributions of binocular and monocular (MT) depth discrimination to the combined depth threshold.