Assessment of visual acuity by evoked potential recording: Ambiguity caused by temporal dependence of spatial frequency selectivity

The spatial-frequency selectivity of pattern evoked potentials depends on the stimulus repetition rate: responses to low spatial frequencies are emphasized by stimulating at 16–20 Hz, while responses to high spatial frequencies are emphasized at 5–8 Hz. These findings are consistent with the suggestion that pattern EP's are a mixture of pattern responses and responses to local flicker. To a first approximation the “local flicker” responses resemble EP's produced by flickering a light similar to the patterned stimulis in all respects except for absence of pattern. Any developmental changes in the temporal tuning of pattern responses and/or local flicker responses might distort the results of studies in which pattern EP's have been used as an index of either (a) the development of visual acuity or (b) acuity changes due to visual deprivation. Methods of minimizing this problem are suggested.     

Habitual vs optimal distance visual acuity

PURPOSE: The maintenance of a good level of vision is desirable for developmental and social reasons; it is also a requirement that should not be overlooked in the clinical research environment. This study set out to quantify and analyse any difference between 'habitual' (pre-sight test) and 'optimal' (post-refraction) distance visual acuity in an optometric population. It is intended that the outcome of this work will inform not only clinicians but also those undertaking vision research. METHODS: Binocular logMAR visual acuity was determined at 6 m before and after optometric intervention in patients attending optometric practice for a routine sight test. Cases were recorded seriatim but restricted to the 'core' refraction range representative of typical optometric practice; three further exemption criteria included subject illiteracy, the necessity for a non-standard test distance and contact lens wear. Over a 12-month period, two-thirds of patients examined satisfied the study inclusion criteria; it is the clinical data of these 1288 individuals that are described and analysed here. RESULTS: These data provide a quantitative demonstration that an optometric intervention will most likely improve the habitual distance visual acuity of subjects, irrespective of gender, age group, time interval since last test, refractive status and whether or not the subject is a habitual spectacle wearer. The improvement found was typically within one logMAR chart line (<5 letters), being greatest in spectacle-wearing teenagers and in individuals beyond retirement age (increasing to eight letters in elderly habitual non-spectacle wearers); also in non-wearers who left an interval of 2 years or more between sight tests. CONCLUSIONS: Clinical and laboratory-based investigators are advised that a current and optimal refractive correction should be worn by subjects of all ages enrolled in vision-related studies. Refractive defocus may introduce or exaggerate test outcome variability.     

弱视眼的激光干涉条纹视力测定与研究

测定了４２名（６１眼）斜视性／屈光参差性／屈光不正性弱视少儿的激光干涉条纹视力（Ｌａｓｅｒｉｎｔｅｒ－ｆｅｒｅｎｃｅｆｒｉｎｇｓｖｉｓｕａｌａｃｕｉｔｙＩＶＡ）并与其Ｅ字母视力表视力（ＥＶＡ）作了比较和分析，弱视眼的ＩＶＡ多数高于ＥＶＡ（５９．２６～８６．３６％），相当一部分弱视眼（１３．６４～２２．２２％）的ＩＶＡ低于ＥＶＡ，０．００～１８．５２％的弱视眼ＩＶＡ等于ＥＶＡ。作者从视觉通道的角度讨     

A Review of Strategies for Screening of the Visual Fields

: Some strategies for rapid investigation of the visual fields are reviewed. Those aspects considered are the testing of central and peripheral fields, the pattern and density of sampling the visual field with static stimuli and the most suitable stimulus intensity at which to begin the screening of each subject. Some of the design features of 10 visual field screeners and 3 automated perimeters are tabulated to indicate the importance of control of perimetric variables and how strategies for screening have developed from earlier to later designs.     

Visual function and visual perception in cerebral palsied children

PURPOSE: To investigate visual function and perception in cerebral palsied (CP) children. METHODS: A total of 105 congenitally CP children (aged 6-15 years), without severe mental retardation, were classified into three groups: those with spastic quadriplegia, spastic diplegia and spastic hemiplegia. Data collected included patient history, IQ, refraction, far and near visual acuity, position of the eyes and eye movements, visual fields, colour perception, stereoacuity, slit lamp and fundoscopic examinations, and evaluation of visual perception. The results were compared with a control group from the general paediatric population. RESULTS: The IQ of the CP children ranged between 70 and 100. A total of 59% of them had best corrected distance visual acuity <6/6, with 25.5% <6/9. Near visual acuity was also reduced (70.1% scored <6/6 and 38.4% scored <6/9). Incidence of refractive errors was higher than in the control group (hypermetropia in 43.8% of the eyes, myopia 16.19% and astigmatism 40.9%) as was the incidence of strabismus (26.7% esotropic and 27.6% exotropic). In visual field testing, 80.95% of CP children were normal. A total of 94.28% had normal colour perception and 89.52% were free of ocular pathology. Stereopsis was abnormal or absent in 85.71% of the cases. Visual perception was markedly reduced: in 57.14% of the cases it was less than or equal to that of 6-year-old children; in 26.66% equal to that of 6- to 7.5-year-old children, and in 16.2% of the cases greater than or equal to that of 7.5-year-old children. CONCLUSIONS: In the absence of severe mental retardation, CP children have deficient visual skills. It is suggested that the poor visual skills of CP children are a separate, identifiable factor compounding the adverse effects of mental retardation.     

原发性青光眼早期诊断方法的对比研究

目的　比较图形视网膜电图(P-ERG),图形视觉诱发电位(P-VEP),中央视野视网膜光敏感度和眼部动脉血流速度在早期原发性青光眼诊断中诊断价值的大小。方法　对128例230只眼早期原发性开角型和慢性闭角型青光眼以及48例96只眼正常对照组进行上述4种诊断。方法　的检测,计算各方法的敏感度特异度和诊断指数,并对其进行相应的统计学检验.结果　各方法诊断指数间差异均有显著性(P<0.01),并得出这4种检测方法在原发性青光眼早期诊断中的价值为P-ERG>P-VEP>中央视野视网膜光敏感度>眼部动脉血流速度测量。结论　P-ERG,P-VEP和中央视野视网膜光敏感度较眼部动脉血流速度检测在早期原发性青光眼诊断上更有价值     

扫描翻转图像视觉诱发电位视力与对数视力表视力的比较

目的 对扫描图像视觉诱发电位视力(SPVER视力)与对数视力表视力进行比较。方法比较50例受试者的视力表和SPVER视力。在SPVER视力的测定中用了8个不同空间频率的光栅条纹连续扫描,所得数据经离散傅立叶分析后,获得振幅一空间频率曲线,并由外推法估计其视力。结果SPVER视力与视力表视力的总体相关系数r=0．699,在视力表视力大于0．5时,SPVER视力有低估现象,而在视力表视力小于0．5时SPVER视力有高估现象。结论SPVER视力与视力表视力有良好的相关性。由于视力表视力和SPVER视力所用于评估视力的指标不同,使两者结果不完全相同。     

Visual behaviours of neurologically impaired children with cerebral visual impairment: an ethological study

BACKGROUND/AIMS—Visual functions of neurologically impaired children with permanent cerebral visual impairment (CVI) can be difficult to determine. This study investigated the behavioural profile of CVI children by means of ethological observations in order to gain a better understanding of their visual functions.
METHODS—Video registrations of nine subjects who were unable to undergo more orthodox methods of visual function testing were observed and analysed by an ethologist.
RESULTS—A series of behaviours (direct signs) and supportive or confirming behavioural elements (indirect signs) indicating some visual perception in the children were found.
CONCLUSION—Detailed ethological observations of visual behaviour were shown to be useful for analysing visual functions of children with permanent CVI.

Keywords: cerebral visual impairment; visual function; visual behaviour; ethological analysis     

Perceptual visual dysfunction in children - An Indian perspective

Perceptual visual dysfunction (PVD) comprises a group of vision disorders resulting from dysfunction of the posterior parietal and/or temporal lobes. Often, affected children have normal/near normal visual acuities and/or visual fields, but have difficulties in activities of daily living involving the use of vision. PVDs are known to be common among children with risk factors such as a history of prematurity and/or neurodevelopmental disorders. The inferior temporal lobes and ventral stream transform visual signals into perception, while the posterior parietal lobes and dorsal stream transform visual signals to non-consciously map the scene to guide action and facilitate attention. Dysfunction of these can lead to specific visual impairments that need to be identified during history taking, triggering ascertainment of further details by a structured inventory approach. Clinical tests to elicit dorsal and ventral stream visual dysfunctions have good specificity but low sensitivity. Neuropsychologists are rarely available in the developing world to perform detailed assessments, but there are a few tests that can be used by eye care professionals with some training. Optical coherence tomography (OCT) showing thinning of the ganglion cell layer and retinal nerve fiber layer is being explored as a potential tool for rapid assessment in the clinic. The behavioral outcomes of PVD can mimic psychological conditions including autism spectrum disorder, attention deficit hyperactivity disorder, specific learning disability, and intellectual impairment, and one needs to be aware of overlap among these differential diagnoses. A practical functional approach providing working solutions for each child''s set of difficulties in day-to-day activities is needed.     

Fourth nerve palsy as an initial sign of internal carotid-posterior communicating artery aneurysm

A 54-year-old female complained of vertical diplopia on downward gaze with a slight headache lasting two days. When she gazed in a nasal lower direction, right hypertropia became obvious and the Bielschowsky head-tilt test was positive. A trochlear nerve palsy of right eye was diagnosed. Several examinations were performed, including blood chemical and serological examinations, plain CT examination, and cerebrospinal fluid examination. Three days after appearance of the trochlear nerve palsy, oculomotor nerve palsy of right eye occurred with severe ocular and head pain, and a four-vessel study disclosed a large aneurysm at the IC-PC portion and two more aneurysms at the distal portion of the middle cerebral artery. This is a very rare case of trochlear nerve palsy as the initial sign of IC-PC aneurysm and the pathogenesis of trochlear nerve palsy was discussed.     

Properties of visual evoked potentials to onset of movement on a television screen

In 80 subjects the dependence of movement-onset visual evoked potentials on some measures of stimulation was examined, and these responses were compared with pattern-reversal visual evoked potentials to verify the effectiveness of pattern movement application for visual evoked potential acquisition. Horizontally moving vertical gratings were generated on a television screen. The typical movement-onset reactions were characterized by one marked negative peak only, with a peak time between 140 and 200ms. In all subjects the sufficient stimulus duration for acquisition of movement-onset-related visual evoked potentials was 100ms; in some cases it was only 20ms. Higher velocity (5.6°/s) produced higher amplitudes of movement-onset visual evoked potentials than did the lower velocity (2.8°/s). In 80% of subjects, the more distinct reactions were found in the leads from lateral occipital areas (in 60% from the right hemisphere), with no correlation to handedness of subjects. Unlike pattern-reversal visual evoked potentials, the movement-onset responses tended to be larger to extramacular stimulation (annular target of 5°–9°) than to macular stimulation (circular target of 5° diameter).Abbreviation PREP pattern-reversal visual evoked potentials     

Clinical and physiological aspects of the cortical visual prosthesis

Physiological concepts and experimental evidence indicate the feasibility of developing an effective artificial visual system through direct stimulation of the visual cortex. The technical, medical and physiological aspects are reviewed.     

阅读的视觉心理物理学研究方法及影响因素的研究进展

阅读是最重要的视觉工作,许多眼部疾病的首要症状就是阅读困难。临床上通常是通过视力检查来了解阅读情况的。但阅读是一个综合行为,它要求的不仅仅是好的视力,而是受到多种因素的影响。本综述对阅读研究中常用的视觉呈现方式、阔读表现的评估和影响因素等作一简要介绍。     

视雪综合征的研究进展

本文系统介绍了视雪综合征(visual snow syndrome,VSS),这是一种无明确原因,表现为无数闪烁的小点持续存在于整个视野中,并可能伴有后像、内视、畏光、夜盲的视觉现象。目前已经有文献对该疾病进行了临床及病理生理学研究,最新的文献资料中,更倾向于视雪综合征是一种视觉处理功能障碍,需与偏头痛等疾病相鉴别。在治疗方面,目前多是试验性研究,有病例报道显示抗癫痫、抗抑郁药、乙酰唑胺等和有色滤光片对缓解患者症状可能有积极作用。     

噪声视力表在儿童视力检查中的可重复性分析

目的探讨噪声视力表对儿童视力检查的可重复性及其相关影响因素。方法在门诊首诊患儿中,随机选择无理解障碍及除屈光不正外无其他器质性眼病儿童200例,使用噪声视力表进行噪声视力重复检查。采用配对t检验进行统计学分析。结果两次视力测量之间差异的均数为O.03行,（P=0.515）;两次视力测量结果按性别分组无明显差异（P=1.0,P=0.262）;按年龄分组亦无明显差异（P=0.159,P=0.786）;按屈光不正分组,其中近视组两次视力测量结果有明显差异（P=0.010）。近视儿童视力检查一致性较差,而正视及远视儿童的视力检查一致性较好（P=0.133,P=0.083）。结论结果提示噪声视力表适合儿童视力检查,建议推广使用。     

光环境对不同视力者视觉绩效的影响

目的:研究不同模拟光环境下不同视力者视觉绩效的变化,为修订飞行人员视力标准提供试验依据。方法:随机对照研究。招募24名志愿者,根据右眼/左眼视力分为1.0/1.0、0.8/0.8、0.6/0.6和0.4/0.4(小数视力)4组,每组6人,分别在模拟日光、曙暮光和云上光环境下检测双眼静态远视力、动态视力、色觉和深径觉误差及视觉搜索时间,比较不同光环境对不同视力者视觉绩效指标影响的变化。结果:不同光环境下双眼静态远视力、动态视力、色觉误差、深径觉误差和视觉搜索时间存在主效应差异(均P<0.01)。日光下双眼静态远视力、色觉辨别、深径觉和视觉搜索能力均高于曙暮光和云上光。在0.4/0.4视力组,曙暮光、云上光环境下动态视力显著低于日光环境(P<0.01)。不同视力者双眼静态远视力、动态视力、深径觉误差和视觉搜索时间存在主效应差异(均P<0.05)。与1.0/1.0视力组比较,0.6/0.6、0.4/0.4视力组动态视力、深径觉和视觉搜索能力显著下降(均P<0.05)。结论:不同光环境对视力低于正常者视觉绩效存在明显影响,对飞行安全构成潜在的威胁。     

儿童彩色视力表的研制及应用

目的:研制一种儿童彩色视力表,并探讨其应用效果。方法:视力表设计采用视角原理,用彩色图形视标,各行视标间增率以几何级数(10槡10),即1.2589增加。11个彩色图形,共8行,检查距离3m,视力记录为五分记录和小数记录。以标准对数视力表为对照,用新的儿童彩色视力表检查4~6岁儿童100眼。结果:儿童彩色视力表和E字对数视力表检查,两组视力检查结果差异无统计学意义(t=1.2671,P>0.05),两组视力数据存在正相关(r=0.924,P<0.01)。合作率100%,对视标的识别率90%以上。结论:儿童彩色视力表儿童容易接受,具有可靠性,适用于儿童视力的检查。     

视皮层背侧、腹侧流视觉通路的研究进展

视皮层是大脑视觉信息的处理整合中心,灵长类动物的视皮层存在背侧和腹侧流2条相对独立而又相互联系的平行视觉信息通路。笔者总结了视皮层背侧通路（即where+how通路）、腹侧通路（即what通路）的发现、定位、功能以及二者的联系,并从视觉通路临床应用角度系统梳理了视觉皮层背侧、腹侧平行通路的研究进展。目前2条通路结构和功能相关性研究资料较少,对视皮层视觉通路的视觉信息分拣处理、相互作用及通路信息传递过程编码和神经整合处理机制尚缺乏深入研究。此外,关于2条通路的临床研究缺乏系统性和完整性,且研究结果分歧较大,今后需改进研究方法,加强深入研究视觉疾病视通路损害的结构和功能。本文通过对视皮层背侧通路、腹侧通路做—综述,以期为视觉信息的传递、加工和相关临床眼病防治研究提供理论基础。     

FVEP和PVEP检查对年龄相关性白内障术后视力预测的意义

目的：比较年龄相关性白内障患者手术前后闪光视觉诱发电位(flash visual evoked potential, FVEP)和图形视觉诱发电位(pattern visual evoked potential, PVEP)的变化及探讨其在评估术后视力中的意义。

方法：选取 2015-06/2016-05期间在我院治疗的年龄相关性白内障患者68例79眼, 分析手术前后FVEP及PVEP检测结果差异情况。对术前FVEP、PVEP 、FVEP 联合 PVEP检测结果与术后最佳矫正视力(BCVA)进行比较。

结果：FVEP检查术前、术后P2波潜时和N2-P2振幅的检测结果差异无统计学意义(t=0.448、-0.492,P>0.05),PVEP检查术前、术后P100波潜时和N75-P100振幅的检测结果差异有统计学意义(t=2.505、-5.462,P<0.05)。术前FVEP的P2潜时及PVEP的P100潜时与术后BCVA呈负相关关系(r=-0.694,-0.402,P<0.05),术前FVEP的N2-P2振幅与术后BCVA呈正相关关系(r=0.607,P<0.01),术前PVEP的N75-P100振幅与术后BCVA无显著相关性(r=0.237,P>0.05)。FVEP检测一致率达到 83.54%, PVEP检测一致率为66.67%,差异有统计学意义(χ²=5.11,P<0.05)。FVEP 联合 PVEP检测一致率达到 90.74%, PVEP检测一致率为66.67%,差异有统计学意义(χ²=9.34,P<0.01)。

结论：FVEP相比于PVEP对年龄相关性白内障患者术后视力评估的稳定性更好,对术眼术前矫正视力≥0.1的患者FVEP 联合 PVEP检查能有效、客观地评估患者术后患眼视力恢复情况。     

两种干涉条纹视力计对白内障患者术后视力预测的对照研究

目的通过国产干涉条纹视力计与Heine干涉条纹视力计在预测白内障患者术后视力中的应用对比,探讨国产干涉条纹视力计预测白内障患者术后视力的准确性、实用性、可行性。方法将71例(92眼)白内障患者平均分成2组,术后的视功能情况分别用国产干涉条纹视力计与Heine干涉条纹视力计2种方法进行预测,结果与患眼术后最佳矫正视力进行相关性分析对比。结果国产干涉条纹视力计预测的准确率为81.0%(预测视力与术后视力相差2行以内者认为准确),平均预测视力(4.695)与平均术后最佳矫正视力(4.771)比相差不到1行。Heine干涉条纹视力计预测的准确率为43·9%,平均预测视力(4.481)与平均术后最佳矫正视力(4.771)比相差约3行。结论比起Heine干涉条纹视力计,国产干涉条纹视力计检查更能合理的反映视觉功能,对白内障术后视力具有较好的预测性。