特发性黄斑视网膜前膜患眼的对比敏感度功能

目的:探讨对比敏感度对特发性黄斑视网膜前膜(idiopathic macular epiretinal membranes,IMEM)的视功能评价。方法:常规检测71例患者96只视网膜前膜(IMEM)患眼的视力,采用对比敏感度检测卡(FACT)检测患眼和健眼的对比敏感度。采用SPSS11.0软件统计分析资料。结果:患眼的视力为0.15～1.2,健眼视力为0.25～1.5。采用最小角度对数视力统计患眼的平均LogMAR视力为(0.15±0.21),较健眼的平均LogMAR视力(0.03±0.09)低,差异有显著性(P<0.01)。对比敏感度检查显示IMEM患眼各频区的平均对比度值较健眼显著低下(P<0.01)。视力的良莠直接影响到对比度值的高低,并且部分IMEM患眼视力虽然与健眼相等,甚至达到1.0,但其对比敏感度值却已显示出了差异。主要表现在高频区的损害。结论:特发性黄斑视网膜前膜的视功能损害不仅会有视力下降,还会出现对比敏感度值下降。对比敏感度检查是反映视功能的重要、敏感指标之一。     

客观对比敏感度检查在弱视患者中的应用研究

目的:本文通过利用稳态图形VEP,对正常人及弱视患者行对比敏感度检查,初步探讨客观对比敏感度检查的可行性、优越性。方法:所有检查对象,在正常光线下,采用自然瞳孔测试,按常规图形VEP检查方法贴放电极,先检查患者视力较好的眼,后检查视力较差的眼,每一对比度条件下,空间频率自0.5,1.0,2.0,4.0,6.0,8.0,12.0,24.0cpd自动翻转,每只眼依次按照对比度从低到高检查10次,采集,分析不同空间频率的对比度值,输入计算机后,得到空间频率和对比度之间的函数曲线。每一组病例分别计算不同空间频率对比敏感度阈值的样本均数,各组之间采用组间t检验。结果:(1)正常对照组:对比敏感度曲线为钟形,曲线最高点对比度为1.97±0.03,对应空间频率为2.0~4.0cpd。(2)轻度弱视组:在高空间频率与正常组比较差异有统计学意义(P<0.05)。(3)中、重度弱视组:在中、高空间频率,与正常组比较,差异有统计学意义(P<0.05)。(4)不同类型弱视组的对比敏感度曲线仅在中、高空间频率差异有统计学意义(P<0.05),三者之间对比敏感度阈值差异无统计学意义。结论:利用稳态图形VEP作对比敏感度检查是一个较为客观、简单、易行的方法,检查结果与对比敏感度仪检查结果有一致性。     

明暗不同环境下近视及散光眼视觉质量与高阶像差Zernike系数间的关系

目的 探讨在明、暗环境下近视及散光眼视觉质量与高阶像差Zernike系数间的关系. 方法 对123例受试者单眼进行研究.利用Itracy波前像差仪测量像差;分别在明、暗环境下测量对比敏感度及100％、25%、10%、5％四种对比度视力,同时用puillometer测量相应瞳孔大小.分析所有受试者相应瞳孔大小下的高阶波前像差的Zernike系数和对比敏感度函数曲线下的面积(AULCSF)、不同对比度视力(MFVA)间的关系. 结果 在明、暗环境下,AULCSF与C12相关(P＜0.05);25％、10％、5％对比度视力均与C12相关(P＜0.05),100％对比度视力与C12无关(P＞0.05) 结论 在明、暗环境下,影响视觉质量的主要是球差.     

对比度视力检查在视感知觉学习治疗前后的临床应用研究

目的：评估屈光不正患儿视感知觉学习治疗前后的对比度视力变化,探讨视觉质量及视功能的临床意义。方法对视感知觉学习治疗的屈光不正患者50名（100眼）,随机分为两组采用电子视力测量仪检查对比度视力,评估视功能。结果所有患者视感知觉学习训练后对比度视力较国际标准视力改善明显,其中低屈光度数患者改善更明显;治疗后国际标准视力无改善的患者,对比度视力的低亮、标低仍有改善,P〈0.05。结论对比度视力能全面的反应明视力及暗视力,同时视感知觉学习训练对提高屈光不正患者对比敏感度及视力有效,值得推广。     

中心性浆液性视网膜病变患者对比敏感度的改变

用Snellen 视力表所测视力是一个比较粗糙的视功能指标,它所测得的分辨力仅仅是高对比度的目标,但在生活中物体是有不同对比度及不同空间频率的。近年来用对比敏感度作临床检查已广泛引起人们的兴趣。目前已有一些检查对比敏感度的设备问     

飞行员招生体检中亮背景下不同对比度视力和反应时间的研究

目的研究飞行员招生（招飞）体检中正常视力人员在亮背景下不同对比度的视力和反应时间,评估特殊职业选拔时不同对比度视力测量的重要性。方法2007年9月至2007年10月在陕西、甘肃两省参加兰州军区空军招飞体检初检视力达标人员1062例（2124眼）,用多功能电子视力测量仪（MFVA-100）在暗室中先后测试亮背景下对比度为100％、25％、10％、5％时的logMAR视力和反应时间．检测值按对比度进行分组。应用SPSS11．5统计软件进行计量资料组间配对t检验及相关分析。结果随对比度的下降．各组视力呈下降趋势,低对比度组视力明显低于高对比度组（P〈0．01）。100％对比度组视力与25％、10％、5％对比度组视力呈正线性相关（P〈0．01）。随着对比度的降低．各组视力的波动幅度增加,对比度5％时组内波动最大。反应时间随对比度的下降而延长。结论在招飞体检中结合使用视敏度检查和对比度视力检查是有价值的。招飞体检中正常视力人员的对比度视力具有一定特点,能够为军、警等特殊职业的选拔提供依据。     

蓝光滤过人工晶状体植入后对比敏感度评价

目的 评估白内障术后植入蓝光滤过人工晶状体与透明人工晶状体对比敏感度的变化.方法 28例(56只眼)双眼老年性白内障患者行超声乳化手术,一只眼植入蓝光滤过折叠人工晶状体,对侧眼植入透明折叠人工晶状体.观察患者术后的对比度视力、矫正视力、对比敏感度、手术中及术后并发症.结果 术后3个月,在不同的对比度情况下,两组人工晶状体植入眼的不同对比度视力差异无统计学意义(P＞0.05);两组间矫正远视力、矫正近视力差异无统计学意义(P＞0.05);两种人工晶状体植入眼的对比敏感度在任何空间频率上阈值差异无统计学意义(P＞0.05).结论 白内障术后植入蓝光滤过人工晶状体是安全有效的,对患者的对比度视力、对比敏感度没有明显的影响.     

蓝光滤过型非球面人工晶状体植入术后视觉质量的临床研究

目的观察行超声乳化白内障吸除联合植入蓝光滤过型非球面人工晶状体（HOYA PY-60AD）眼的术后视觉质量。设计前瞻性临床研究。研究对象57例（57眼）年龄相关性白内障患者。方法接受超声乳化白内障吸除术的年龄相关性白内障患者57例（57眼）按就诊顺序登记及随机表法将患者分为2组,术中分别植入非球面人工晶状体HOYAPY-60AD（29眼）和球面人工晶状体HOYA AF-1（UY）（28眼）。术后随访3个月。随访时进行一般眼科检查,包括视力、眼压、眼前节及眼底,并记录术后3个月时的裸眼视力（UCVA）、最佳矫正视力（BCVA）、低对比度视力（ETDRS低对比度视力表）、对比敏感度（OPTEC6500,明视、明视眩光、间视和间视眩光）并填写调查问卷（Catquest-9SF）。主要指标UCVA,BCVA,低对比度视力,对比敏感度和调查问卷分值。结果术后3个月,非球面组患者明视（400Lux）条件下5％对比度视力（0．35±0．13）及间视（30Lux）条件下5％（0．49±0．13）和25％（0．25±0．12）对比度视力均好于球面组,分别为（0．43±0．15）、（0．61±0．12）、（0．32±0．14）,差异有统计学意义（P均≤0．05）,间视及间视＋眩光条件下低中频（1．5c／d、3c/d、6c／d、12c/d）的对比敏感度非球面组均好于球面组,差异有统计学意义（P均40．05）。两组患者UCVA、BCVA及调查问卷分值均无统计学差异（P均≥0．05）。结论非球面人工晶状体能够提供较好的低对比度视力和暗环境下的对比敏感度,提示非球面人工晶状体能够提供较好的视觉质量。（眼科,2010,19：89-92）     

低视力患者视功能与表情识别的相关关系

目的：了解低视力患者视功能与表情识别的相关关系，指导患者进行视力康复。方法：分别检查低视力患者视力、对比敏感度及表情识别水平。结果：低空间频率对比敏感度水平与表情识别的相关关系非常显著，视力与表情识别之间存在相关关系，无法得出中、高空间频率对比敏感度与表情识别之间存在相关关系。结论：低空间频率对比敏感度水平能够比视力水平更好地推断低视力患者识别表情的能力。     

视觉评估领域的SLCT和锥细胞对比敏感度测试的临床应用分析

目的：描述新的对比敏感度及色觉检查的原理及其临床应用。方法：对比敏感度用SLCR来评估。SLCT是由几行大小不变(20／25)，但对比度逐渐降低的字母组成的对比敏感度表。色觉以锥细胞的对比敏感度来评估，这是一种视屏测试方法，每一个字母都代表三种视锥细胞中的一种类型(红、绿或蓝)，对比度逐渐降低，分别确定分辨的阈值。测试对象分别为正常受试者以及有眼部疾病的患者。结果：SLCT在检查微小的离焦量以及早期眼部疾病方面比传统的检查具有更大的优势。锥细胞对比敏感度测试比传统的色觉检查敏感性高，不仅可以揭示遗传性色觉异常的类型及其严重程度，而且可以发现不同疾病造成的敏感度的下降。结论：这些新的方法拓展了视觉评估领域，揭示了人眼分辨力的微小变化，提示了遗传性、获得色觉异常眼病的类型和严重程度。     

Reading performance in children with low vision

Purpose: While educators and optometrists are concerned with reading efficiency in children with low vision, in most low vision assessments, children's reading performance is assessed only by a brief evaluation of reading fluency. We examined the relationships between clinical vision measures and reading performance in children with low vision. Methods: Subjects were 71 students with low vision, aged seven to 18 years. The vision and reading performance measures were: high contrast distance visual acuity, contrast sensitivity using both the Pelli‐Robson and LH symbol charts, near text visual acuity and reading rates on a range of print sizes. Results: Most children achieved maximum reading rate at print sizes between 2.5 and seven times larger than threshold print size. Maximum reading rate increased significantly with age and near visual acuity. There was no significant relationship between reading rate and contrast sensitivity. Conclusions: The majority of children with low vision can achieve near normal reading rates with magnification. Age is the strongest predictor of reading rate in children with low vision. They need print sizes well above threshold to achieve maximum reading rate. Routine contrast sensitivity testing of visually impaired students is not indicated for reading assessment.     

Repeatability of the Waterloo Four-Contrast LogMAR Visual Acuity chart and Near Vision Test card on a group of normal young adults

PURPOSES: To investigate the repeatability of logMAR visual acuity (VA) with the Waterloo Four-Contrast LogMAR Visual Acuity (FCLVA) chart and the Near Vision Test (NVT) card. The differences and agreements between near logMAR VA using horizontally- and vertically-presented letters were also determined. METHODS: Visual acuity of one eye (55 subjects) was first assessed by using the FCLVA chart, comprising four charts of varying contrast, and then with the NVT card (comprising four charts of two contrasts and two presentations). Measurements were repeated after 3 or 4 weeks. RESULTS: No significant between-visit differences were observed for any of the charts used. The repeatability coefficient for the distance 90, 60, 30 and 10% charts were 0.07, 0.11, 0.15 and 0.16 log units, respectively. The repeatability coefficients of the near vision charts were 0.06, 0.04 (high contrast), 0.11 and 0.10 (low contrast) log units. The agreements between horizontally- and vertically-presented letters were good. The differences were similar to the repeatability coefficient of each chart. CONCLUSIONS: The repeatability coefficient of the high contrast distance and near chart was about half a line. Repeatability coefficients increase with decreasing contrasts for both distance and near charts, with coefficients of one line or more for low contrast charts. Variabilities in both distance and near VA increase with decrease in contrast. The presentation of the letters does not affect near VA and the agreement between horizontally- and vertically-presented letters (both high and low contrast) was within the repeatability coefficient of each chart.     

Effect of light-emitting diode colour temperature on magnifier reading performance of the visually impaired

Background: As light‐emitting diodes become more common as the light source for low vision aids, the effect of illumination colour temperature on magnifier reading performance was investigated. Methods: Reading ability (maximum reading speed, critical print size, threshold near visual acuity) using Radner charts and subjective preference was assessed for 107 participants with visual impairment using three stand magnifiers with light emitting diode illumination colour temperatures of 2,700 K, 4,500 K and 6,000 K. The results were compared with distance visual acuity, prescribed magnification, age and the primary cause of visual impairment. Results: Reading speed, critical print size and near visual acuity were unaffected by illumination colour temperature (p > 0.05). Reading metrics decreased with worsening acuity and higher levels of prescribed magnification but acuity was unaffected by age. Each colour temperature was preferred and disliked by a similar number of patients and was unrelated to distance visual acuity, prescribed magnification and age (p > 0.05). Patients had better near acuity (p = 0.002), critical print size (p = 0.034) and maximum reading speed (p < 0.001), and the improvement in near from distance acuity was greater (p = 0.004) with their preferred rather than least‐liked colour temperature illumination. Conclusion: A range of colour temperature illuminations should be offered to all visually impaired individuals prescribed with an optical magnifier for near tasks to optimise subjective and objective benefits.     

Optimal reading speed in simulated cataract: development of a potential vision test

Previous studies suggest that optimal reading speed is unaffected by cataract, yet is significantly reduced in age-related macular disease. This raises the question of whether a reading speed test could be developed to assess potential vision after cataract surgery. In this study, 20 young subjects, with and without a simulation of dense cataract, read aloud Bailey-Lovie word charts. From the results, critical print size, optimal reading speed and word acuity were calculated. The simulated cataract reduced word acuity and increased the critical print size, yet optimal reading speed remained unchanged. Measurements were also taken with the charts in reversed contrast polarity. Reversing the contrast polarity of the charts improved the word acuity and optimal reading speed with the cataract simulation. The results suggest that optimal reading speed could be used as a potential vision test. Further investigations using patients with cataract and ARMD are required.     

The practical near acuity chart (PNAC) and prediction of visual ability at near.

OBJECTIVE: To improve on present reading chart designs, providing a quick and accurate method to measure the near acuity threshold, of particular importance with low vision patients. DESIGN: The Practical Near Acuity Chart (PNAC) uses a single paragraph with 3 simple related words on each line (12 lower case letters). The line print size decreases in a logMAR progression (N80-N5). METHODS: The time taken to measure near acuity of 53 subjects aged 9-91 years with the PNAC and Bailey-Lovie near chart was recorded and compared to their distance acuity (Bailey-Lovie chart), contrast sensitivity (Melbourne Edge Test) and ability to read extracts of newsprint. RESULTS: There was no difference in near acuity threshold using related or un-related words. There was a high correlation (r = 0.97) between near acuity measured with the PNAC and Bailey-Lovie charts. However, the time taken to measure near acuity was significantly faster with the PNAC (32 +/- 2 s vs 76 +/- 4 s, p < 0.001). Near acuity measured with either chart was highly correlated (p < 0.001) to distance acuity (r = 0.74), contrast sensitivity (r = 0.62) and ability to read newsprint (r = 0.87). The PNAC was shown to have high test-reliable (r = 0.99). CONCLUSIONS: The PNAC offers a quick but accurate way to measure near acuity and shows a high degree of correlation with distance acuity, contrast sensitivity and the ability to read newsprint.     

The reading speed of adolescent with low vision used electronic visual aids

PURPOSE:To evaluate the reading speed of adolescents with different causes of low vision using electronic visual aids. METHODS:The screening of 10 young students from Quanzhou Blind School could read Chinese N5 print by different optical aids. After their refractive correction and ophthalmic examination, the reading speeds with Chinese N5 print were measured using various optical and electronic visual aids. RESULTS:The reading speed of (34.36±5.06) word / min by electronic visual aids performed faster than that of (18.50±6.54) word / min by optical visual aids in 10 young students with low vision (P<0.05). The reading speed of young people with low vision due to different causes had no direct linear correlation with their near visual acuity（P>0.05）. CONCLUSION:The electronic visual aids more significantly improve the reading speed of young people with low vision than the optical visual aids did. The reading speed of young people with low vision is not relevant to their near visual acuity induced by different causes.     

Reading performance in patients with retinitis pigmentosa: a study using the MNREAD charts

PURPOSE: To evaluate the relationship between reading performance and severity of disease in patients with retinitis pigmentosa (RP), assessed with routine clinical psychophysical visual tests. METHODS: Seventy-six consecutive patients with RP (145 eyes), with reading acuity of at least 1.6 logMAR (logarithm of the minimum angle of resolution) in at least one eye, were examined. Each patient underwent a complete ophthalmic evaluation, including visual acuity (Early Treatment Diabetic Retinopathy Study [ETDRS] charts), contrast sensitivity (Pelli-Robson charts), visual field perimetry (Humphrey central 30-2 full-threshold program; Carl Zeiss Meditec, Dublin, CA), and a test of reading acuity, critical print size, and maximum reading speed (Minnesota Reading charts [MNREAD]). RESULTS: Reading acuity was 1.0 logMAR or more in the better eye of all but six (92%) patients. Maximum reading speed was better than 100 words per minute in the better eye of 59 (78%) subjects. Moderate to severe reading impairment, defined as reading acuity of 0.4 logMAR or worse, was observed in the better eye of 47 (62%) patients. EDTRS visual acuity of 0.3 logMAR (20/40) or worse was 89% sensitive and 66% specific when used as a criterion to define reading impairment. Contrast sensitivity and visual acuity correlated significantly with all three reading components, whereas mean light sensitivity in the central visual field (6 degrees ) demonstrated a higher correlation with maximum reading speed. The number of years elapsed since the diagnosis of RP was a strong negative predictor of reading performance when clinical visual tests were taken into account, whereas a better reading ability characterized the patients with RP who had a higher level of education. A reduced reading speed with larger print size was found in 30 eyes (21%). This correlated with central light sensitivity, as it was more common among eyes with a mean sensitivity of <10 dB. CONCLUSIONS: The reading performance of most patients with RP is only moderately impaired. It correlates with contrast sensitivity, visual acuity, and visual field. It should be assessed in all cases, as disability can ensue, even when visual acuity is preserved. In patients with RP with poor reading performance, there is little potential for high-magnification devices because visual field constriction affects the reading rate.     

Reading acuity in children: evaluation and reliability using MNREAD charts

PURPOSE: To study reading acuity in children and assess the reliability of its measurement using the Italian version of the MNREAD reading chart. METHODS: One hundred sixteen children from grades 3 to 8 with normal near vision were tested at a pediatric eye care institution in northeastern Italy. Visual acuity was evaluated with Early Treatment Diabetic Retinopathy Study (ETDRS) charts and reading acuity with MNREAD charts. Examination with charts 1 and 2 by the same examiner in the same visit were used as test-retest measurements. RESULTS: Mean improvement of performance from grades 3 to 8 was approximately 1 line for ETDRS acuity and 1.5 sentences for reading acuity and critical print size. Mean maximum reading speed increased from 96 to 167 words/minute. Regression analysis showed that a stable reading speed was obtained throughout sentences of decreasing size up to the critical print size. Measurement error, expressed as 95% limits of agreement, was +/- 0.136 logarithm of the minimum angle of resolution (logMAR) and +/- 0.142 logMAR for ETDRS acuity and reading acuity, respectively. Critical print size had the lowest reliability (+/- 0.193 logMAR). Maximum reading speed limits of agreement were +/- 0.077 logarithm of words per minute (logWPM), or a 19% change in words per minute. There were no detectable effects of grade and refractive error on measurement errors. CONCLUSIONS: In children, MNREAD charts provide measurements of reading acuity as reliable as ETDRS chart measurements of distance acuity on a logMAR scale. They also provide highly reliable measurements of the maximum reading speed across all grades, independent of its noticeable increase.     

The effect of letter-stroke boldness on reading speed in central and peripheral vision

People with central vision loss often prefer boldface print over normal print for reading. However, little is known about how reading speed is influenced by the letter-stroke boldness of font. In this study, we examined the reliance of reading speed on stroke boldness, and determined whether this reliance differs between the normal central and peripheral vision. Reading speed was measured using the rapid serial visual presentation paradigm, where observers with normal vision read aloud short single sentences presented on a computer monitor, one word at a time. Text was rendered in Courier at six levels of boldness, defined as the stroke-width normalized to that of the standard Courier font: 0.27, 0.72, 1, 1.48, 1.89 and 3.04× the standard. Testings were conducted at the fovea and 10° in the inferior visual field. Print sizes used were 0.8× and 1.4× the critical print size (smallest print size that can be read at the maximum reading speed). At the fovea, reading speed was invariant for the middle four levels of boldness, but dropped by 23.3% for the least and the most bold text. At 10° eccentricity, reading speed was virtually the same for all boldness <1, but showed a poorer tolerance to bolder text, dropping by 21.5% for 1.89× boldness and 51% for the most bold (3.04×) text. These results could not be accounted for by the changes in print size or the RMS contrast of text associated with changes in stroke boldness. Our results suggest that contrary to the popular belief, reading speed does not benefit from bold text in the normal fovea and periphery. Excessive increase in stroke boldness may even impair reading speed, especially in the periphery.     

Visual function: the problem with eccentricity

Age‐related macular degeneration (AMD) is the leading cause of blindness in developed countries. With an ageing population, the prevalence of such a condition has resulted in a large proportion of the population relying on peripheral vision to undertake activities of daily living. Peripheral vision is not a scaled‐down version of the fovea, simply requiring larger print or increased contrast for detection of objects or reading text. Even when print size is scaled and eye movements are minimised, the peripheral retina cannot perform at the level of the foveal region. Understanding how and why reading performance is limited as a function of eccentricity has important implications for how we approach rehabilitation of patients with central visual loss. This brief review of the extensive literature on reading with peripheral vision and the research aimed at better reading rehabilitation for low vision patients focuses on why many of the problems associated with the reduced reading capability of peripheral vision cannot be completely solved with magnification, reducing eye movements or modifying print.