Visual mechanisms governing the perception of auto-stereograms

Background: Single image random dot stereograms (SIRDS) have been used to study diverse visual parameters and skills. The aim of the present study was to identify the main optometric factors involved in the perception of SIRDS and to obtain a discriminant model to categorise our participants in terms of their skill in perceiving SIRDS. Methods: Response time was determined to assess the ability of 69 participants to perceive the hidden three‐dimensional shape in an auto‐stereogram presented under controlled conditions, whereupon three skill level groups were defined. The same participants were administered a battery of optometric tests to evaluate various aspects of accommodation and convergence, as well as stereopsis and phoria. Linear discriminant analysis, which served to examine the relationship between response times and the evaluated visual parameters and skills, provided a set of discriminant functions (or model), thus allowing for the categorisation of participants according to their skill to perceive SIRDS. Results: Two discriminant functions were obtained, which allowed for an overall predictive accuracy of 66.67 per cent (p = 0.024), with a higher predictive accuracy for groups 1 (minimum time less than 10 seconds, 78.26 per cent) and 2 (minimum time greater than 10 seconds, 75.86 per cent) than for group 3 (SIRDS not perceived, 35.29 per cent). Stereoacuity, negative relative convergence, phoria at near and, to a lesser extent, the accommodative convergence and accommodation ratio were found to be the most relevant discriminant variables, although between‐group statistically significant differences were only disclosed for stereoacuity (p = 0.001) and negative relative convergence (p = 0.003). Conclusion: The ability to perceive SIRDS was related to many visual parameters and skills, including, but not limited to, stereoacuity and negative relative convergence. It is uncertain whether SIRDS might be considered a useful tool in clinical practice.     

Strabismus and Binocular Functions in a Sample of Swedish Children Aged 4–15 Years

Purpose: To investigate strabismus, head posture, nystagmus, stereoacuity, ocular motility, near point of convergence (NPC) and accommodative convergence to accommodation ratio (AC/A) in a sample of Swedish children. Methods: A prospective cross-sectional study was carried out on 143 children, 4–15 years of age. Results: Heterotropia was found in five children (3.5%), four with esotropia and one with exotropia. One child with esotropia had a slight overaction of both inferior oblique muscles. Heterophoria was found in 37 children (26%) at near and/or distance fixation and it was four times more common at near than at distance. In 29 children, heterophoria was found at one distance only and orthophoria at the other. Orthophoria at both near and distance fixation was noted in 101 children (70.5%). The near point of convergence was ≤6 cm in 97% of the children and 97% had stereoacuity of 60″ or better. In the whole group, the median AC/A ratio calculated with the heterophoria method was 5.6/1 prism diopters/diopters (PD/D) and with the gradient method, 1.3/1 PD/D. No anomalous head postures or nystagmus were observed and all children had normal versions. Conclusion: In this study, 143 well-defined children were investigated with a battery of accurately described tests, commonly used in clinical practice. These results are in agreement with those of other studies examining one or few variables in larger populations and the authors therefore conclude that their results may be used for comparisons with different patient groups.     

立体视正常值变化观察

目的:比较Frisby、Randot、Howard-Dolman三种立体视检查方法的可重复性,确定此三种临床用立体视检查方法的正常值变化的95%可信区间.方法:选择26位无斜视、弱视和眼手术史的健康个体,平均年龄为24.42±4.26岁(14～32岁),所有的受检者具有正常的双眼视且双眼视力为6/6.测量视远瞳距和习惯视力后,以随机的顺序用Frisby、Randot、Howard-Dolman三种检查方法测量立体视,测量时保持光照度为670lx.约1周后在相同的测量条件下同样用三种检查方法测量立体视,平均间隔时间为7.8±2.4天.结果:三种临床立体视检查方法的可重复性系数分别为±2.7"(Frisby)、±8.0"(Randot)和±9.3"(Howard-Dolman),再次试验的平均值低于首次试验的平均值,t检验提示这改变差异无显著性意义(P>0.05).重复试验的相关系数分别为0.91(Frisby)、0.56(Randot)、0.60(Howard-Dolman).三种检查方法之间的相关系数分别为0.31、0.31、0.33.结论:三种临床立体视检查方法的相关性较差.Frisby检查法有最好的重复性和正常值有较小的范围.用该法测得成年人立体视改变的95%可信区间为±2.7".如果用Frisby法测得年轻成年人的立体视的变化超过这个范围,可认为是有显著意义的临床改变.     

中心性浆液性脉络膜视网膜病变患者远近立体视功能

目的 :比较“中浆”患者远近立体视功能损害的临床特点。方法 :对 48例 (5 1眼 )中浆患者按常规方法检查视力、屈光、Amsler方格卡、双眼影像、眼底FFA或OCT ;用同视机检查患者双眼同时知觉、融合范围及定性立体视 ;采用同视机随机点画片及《立体视觉检查图》检测患者的远近立体视功能及抑制性暗点。结果 :48例患者除中心视力下降、视物变形和有中心暗点等单眼视功能受损外 ,还有双眼影像不等及双眼视功能不同程度的损害。双眼视功能受损中 ,双眼同时视障碍为 2 .1% ,双眼融合视缺失为 4.3% ,而双眼定性立体视丢失为 16 .7%。采用随机点画片定量检测发现 ,远距离交叉视差锐度和非交叉视差锐度及近距离立体视锐度达到正常者分别为 2 8例 (占 5 8.3% )、2 4例 (占 5 0 .0 % )和 14例(占 2 9.2 % )。显示近立体视损害较远立体视更明显 ,差异有显著性 (P <0 .0 5 )。病愈后三项功能恢复中心立体视者分别为 47例 (占 97.9% )、46例 (占 95 .8% )和 45例 (占 93.8% )。病愈前后远近距离三项立体视锐度达到正常者的比例以及平均视锐度值 ,差异有显著性 (P <0 .0 1)。影响立体视功能的主要原因是两眼视力相差大 ,双眼同时视像差大及有抑制性中心暗点。结论 :中浆患者视功能受损表现是多方面的。双眼视功能受损特     

Correlation between Depth Perception by Three-Rods Test and Stereoacuity by Distance Randot Stereotest

Background: The examination of depth perception with three-rods test, in addition to visual acuity testing, is required to obtain motor vehicle license to drive taxies and trucks, according to the Road Traffic Act in Japan. The aim of this study was to examine whether the results of the three-rods test would correlate with the results of static stereopsis tests, used in ophthalmic practice.

Methods: This study involved 54 normal subjects, 9 women and 45 men, with ages ranging from 18 to 25 (mean, 20.8) years. All had visual acuity of 0.8 or better with or without glasses or contact lenses correction and had no strabismus at the distant (5?m) or near (0.3?m) fixation. TNO Stereotest and Titmus Stereotest were examined at 40?cm while Distance Randot Stereotest was at 3?m. At three-rods test, a central rod was moved at the speed of 50?mm/sec forward and backward automatically against two laterally located fixed rods, placed inside the illuminated box. An examinee at the distance of 2.5?m observed the rods inside the box from a small viewing window and pushed a button to stop the central rod in alignment with the fixed rods. Erred distance (mm) of the central rod from the fixed rods as a mean of 4 measurements was correlated with stereoacuity in second of arc, measured by three kinds of the stereopsis tests.

Results: The erred distance of three-rods test was positively correlated with static stereoacuity at distance measured with Distance Randot Stereotest (ρ?=?0.418, p?=?0.0023, Spearman rank correlation test) and also with the other stereopsis tests at near fixation. The stereoacuity at near fixation, measured by TNO Stereotest and Titmus Stereotest, was positively correlated with each other (ρ?=?0.431, p?=?0.0017).

Conclusion: Three-rods test, examining depth perception, together with the response by eye-hand coordination, gave consistent results with distant static stereoacuity when measured with Distance Randot Stereotest.     

间歇性外斜视的控制力评估及其立体视觉

间歇性外斜视在我国发病率高,病因不明.本文着重从间歇性外斜视控制力的评估及立体视的研究进展进行综述.以神经可塑性原理和知觉训练为切入点,依据背流、腹流通路的相关原理进行干预,有助于改善间歇性外斜视患者的双眼视功能和生活质量,使间歇性外斜视患者达到功能治愈.     

立体视锐度与发样十五种元素关系初探

本文采用X－射线荧光分析法测定抚州市区152名健康中小学生（其中立体视锐度异常29人）的头发中Ca、Cr、Mn、Fe、Co、Ni、Cu、Zn、As、Mg、Pb、Cd、Mo、Se和Ge等15种元素的含量。结果表明立体视锐度异常儿童头发中Se元素含量较正常组低（P＜0．05），而Zn／Cu比值则明显高于正常组（P＜0．05），提示给予富含硒元素的食物，提高体内硒含量，调整Zn／Cu比值．对防治立体视税度导常发生具有重要作用。     

数显补色照片体视仪的初步临床应用

介绍一种新设计的近距离立体视检测工具－－数显补色照片体视仪。同时应用该仪器对１１３名学生进行近距离立体视锐度测定。结果表明：该仪器具有极高的精密度、正确度和精鸪。该仪器用红－绿蓝颜色互补原理形成双眼视觉分离效果，从零点开始作逐渐增大的立体视镜度测定。其主要特点为：①可测的最小立体视锐度为１０秒。②可测的最大立体视锐度在１０００秒以上。③可连续性测量。④便于临床医师携带应用。     

Effects of practice and the separation of test targets on foveal and peripheral stereoacuity

The improvement in stereoacuity of two inexperienced, normal subjects was compared at foveal and at 2.5 degrees and 5 degrees peripheral target locations as a function of practice. Outlines of two squares differing only in binocular disparity were used as test stimuli and estimates of stereoacuity were obtained by application of the method of constant stimuli with feedback. The peripheral thresholds of both subjects improved 60-80% over the course of the first 3000-4000 responses at each stimulus location. Foveal improvement followed an identical time-course with a 73% improvement in one subject and only 23% in the other. This difference was reflected in the peripheral/foveal threshold ratios of the two subjects and underlines the necessity of ensuring the stability of thresholds. Stereoacuity measurements were also obtained using several different square separations at the fovea and at 2.5 degrees, 5 degrees and 10 degrees peripheral locations along the horizontal and vertical retinal meridians of two other normal subjects. Practice-stabilized disparity thresholds using optimal target separations revealed a steeper deterioration between the fovea and 2.5-5 degrees eccentricities than did measurements of the same subjects' minimum angles of resolution (MAR). The decrease of optimal stereoacuity at the more peripheral test locations was more gradual than has been previously reported but was not clearly related to that of the MAR.