Methods of visual acuity determination with the spatial frequency sweep visual evoked potential

Purpose The spatial frequency sweep visual evoked potential (sVEP) is used to rapidly determine visual acuity in children or non-responsive patients. Two techniques have been used to separate signal from noise: (1) the 95% confidence interval for the signal amplitude (95% CI) or (2) the amplitude of a Fourier frequency adjacent to 2×the signal frequency (DFT). The purpose of this study is to determine if there is a significant difference in acuity estimates with these techniques.Methods Ten normal subjects (approximately 0.00logMAR acuity) and 11 patients with decreased visual acuity took part in this project. Stimulus production and data analysis were done with an Enfant 4010 (Neuroscientific Corp). Standard VEP recording techniques were employed. The stimulus was a horizontal-oriented, sine wave grating that swept up the spatial frequency spectrum (contrast 80%, temporal reversal rate 7.5Hz). Sweeps were repeated until the confidence intervals for the data were no longer decreasing. The Bailey LovielogMAR chart was used to determine visual acuity. A line was fit to the high spatial frequency data using either the 95% CI or the DFT as the noise estimate. By using these linear equations, acuity estimates were obtained at 0, 1, and 2V signal amplitudes.Results The average logMAR acuity for the subjects with normal acuity was –0.06±0.070 (SD). The sVEP acuity estimates were 0.08±0.098, 0.18±0.092, and 0.33±0.195 (0, 1, and 2V extrapolations) with the 95% CI used as noise and 0.07±0.100, 0.18±0.103, and 0.33±0.202 (0, 1, and 2V extrapolations) with the DFT used as noise. By using the average noise from the Fourier frequency as the extrapolation level, the acuity was 0.10±0.098logMAR. The averagelogMAR acuity for the subjects with decreased visual acuity was 0.67±0.306 (SD). The sVEP acuity estimates were 0.53±0.175, 0.66±0.171, and 0.88±0.295 (0, 1, and 2V extrapolations) with the 95% CI used as noise and 0.53±0.179, 0.65±0.176, and 0.86±0.268 (0, 1, and 2V extrapolations) with the DFT used as noise. By using the average noise from the Fourier frequency as the extrapolation level, the acuity was 0.57±0.186logMAR. No significant difference was found between the two acuity estimate techniques for all of the subjects (repeated measures ANOVA, p=0.16, F₂₀=2.131). The sVEP estimates of acuity to the 0V and noise levels were not significantly different from the logMAR acuity (paired t-test, all p values >0.05).Conclusions The results indicate that the sVEP acuity does not depend on the noise estimation technique. In agreement with prior studies, the sVEP acuity underestimates the logMAR acuity in normally sighted individuals by about an octave.     

Evaluating the visual experience: visual acuity and the visual analogue scale

PURPOSE: To attempt a comparison of the visual experience [assessed using a visual analogue scale (VAS)] with visual acuity in a group of normally-sighted adult optometric patients. METHODS: A single-item 100 mm paper VAS was administered to a sequence of 142 normally-sighted pre-presbyopic patients. Each individual was invited to indicate their recent subjective distance visual experience between the extremes of 'dreadful' (0 mm) and 'perfect' (100 mm). Each patient's binocular visual acuity was then determined at 6 m using a high-contrast logMAR chart under usual consulting room conditions. RESULTS: A weak association was revealed between the subjective indication of recent visual experience and the actual level of binocular acuity recorded in this normally-sighted group of subjects. On the basis of group responses a statistically significant discontinuity in the scores recorded with the VAS was demonstrated between patients who attained a clinical acuity better or worse than 0.10 logMAR units (6/7.5). Patient gender, age, and whether spectacles were habitually worn for distance viewing, were each revealed to be not statistically significant features. CONCLUSIONS: For normally-sighted optometric patients the subjective criterion of visual satisfaction would appear to be only loosely associated with the contemporaneous record of clinical acuity.     

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。     

弱视患者远、近视力差异的临床观察

目的  了解弱视儿童近视力和远视力是否存在差异。设计 回顾性病例系列。研究对象 弱视儿童81例（139眼）。方法 对81例初次就诊的弱视患者进行屈光矫正,分别运用标准对数远视力表和标准对数近视力表进行矫正后远、近视力的测量及分析。对所有接受检查的弱视儿童分别按年龄、屈光度和病因进行分组统计分析。主要指标 近视力,远视力。结果 不同病因弱视患者的远近视力比较：屈光不正性弱视、屈光参差性弱视、斜视性弱视患者的平均近视力分别为0.48±0.27、0.47±0.28、0.45±0.30,平均远视力分别为0.46±0.22、0.40±0.20、0.43±0.30,各组的远近视力差异均无统计学意义（P均＞0.05）。不同年龄弱视患者的远近视力比较：3岁～≤5岁组、＞5岁～≤7岁组、＞7岁～12岁组的平均近视力分别为0.41±0.23、0.56±0.29、0.46±0.31,平均远视力分别为0.39±0.18、0.52±0.22、0.42±0.23,各年龄组患者的远近视力差异均无统计学意义（P均＞0.05）。不同屈光度弱视患者的远近视力比较：≤+4.00 D组和＞+4.00 D组平均近视力分别为0.45±0.26、0.48±0.28,平均远视力为0.40±0.30、0.46±0.21,两组屈光度患者的近视力与远视力平均值差异均无统计学意义（P均＞0.05）。结论 本研究结果显示,不同病因、不同年龄段、不同屈光度的弱视患者其远、近视力无明显差异。 （眼科,2013,22： 266-268）     

Transforming scales of measurement of visual acuity at the group level

Aim: To provide formulae that may be used to transform sample‐based estimates of group‐level mean and standard deviation of visual acuity (VA) across different scales of measurement. Methods: We focused on 3 transformations: (1) ETDRS letters – LogMAR (2) Decimal – LogMAR and (3) Snellen – LogMAR. We assumed that logMAR follows a normal distribution in the underlying population and used the empirical asymptotic normal approximation of the joint distribution of average and standard deviation in order to derive formulae for transformation of group‐level estimates. We considered that the true population parameters are not known and are to be estimated using data from a sample of patients (which is essentially always the case). We compared estimates obtained with the proposed sample‐based approach with those based on a “naïve” approach in which individual‐level formulae are used directly for transformation of means and standard deviations at the group‐level. Results: Applying formulae that are appropriate for transformations of scales of measurement for data at the individual‐ (or patient‐) level, to transform VA at the group level, can lead to biased estimates of means and standard deviations. In particular, it could lead to underestimation of the average logMAR VA in studies that use decimal VA. Such bias will be greater in magnitude when disease strongly affects VA. Conclusions: This paper provides formulae that can be easily implemented in standard spreadsheet software programs, and which allow appropriate transformations of group‐level estimates of mean and standard deviation of VA across different scales of measurement. These transformations are helpful for performing meta‐analyses or for comparisons of results across studies when VA is expressed in different units.     

A new Gujarati language logMAR visual acuity chart: Development and validation

Aims:

Gujarati is the main spoken language of a large proportion of the population of India. The aim of this study was to develop and validate a new Minimum Angle of Resolution (logMAR) visual acuity chart in the Gujarati language.

Materials and Methods:

A new Gujarati visual acuity chart was designed to logMAR specifications using Gujarati optotypes experimentally selected to have similar relative letter legibility under spherical and cylindrical defocus. The chart validation study was carried out using 153 adult subjects in a large clinical setting in India. Subjects who were literate in English and Gujarati participated in the study. Visual acuity was measured with the new Gujarati logMAR chart and a modified Early Treatment of Diabetic Retinopathy Study-(m-ETDRS) logMAR chart. The method of presentation was randomized between the charts. Repeat visual acuity was measured on a subsequent day with a second version of the Gujarati logMAR chart.

Results:

The Gujarati chart correlated highly with the m-ETDRS logMAR chart (r² = 0.974). The mean visual acuity difference (Gujarati – m-ETDRS logMAR) was equal to three letters (–0.06 logMAR). The Gujarati logMAR chart also proved to be highly repeatable (r² = 0.994, test-retest) with 95% CI of ± 0.04 logMAR.

Conclusions:

The new Gujarati logMAR visual acuity chart provides a valid and repeatable tool for the measurement of visual acuity in native Gujarati language speakers.     

Habitual visual acuity in a large urban cohort of Western India and factors influencing poor habitual vision

Purpose:The aim of this study was to determine habitual visual acuity (HVA) in a large urban cohort in western India and identify factors associated with poor HVA.Methods:This was a prospective study conducted over 10 days in September 2018 to assess the HVA in individuals attending a 10-day festival in Western India. Participants who volunteered to undergo vision screening and also filled the questionnaire form pertaining to demographic information including their age, gender, address, income, and educational status were included in this study. HVA was recorded with the distance correction that the participants were wearing when they attended the screening. The study evaluated the prevalence of visual acuity 6/6 or <6/6, 6/12, and 6/18 and the factors associated with lower visual acuity.Results:Of the 6300 participants, 1660 (26.3%) were females. Majority of the participants were from urban background (6084, 96.6%) and were of younger age group (18–40 years––3786, 60.1%; 41–60 years––2187, 34.7%; >60 years––327, 5.2%). HVA was recorded as 6/6 both eyes in 4136 (65.6%), at least 6/12 both eyes in 5691 (90.3%), and at least 6/18 both eyes in 5974 (94.8%) individuals. Only 11 patients (0.17%) had VA worse than 6/60 with only 3 patients (0.003%) having bilateral VA <6/60. Older age, female sex, lower education status, and low annual income were significant risk factors for poor HVA.Conclusion:Poor education, lower income, female gender, and old age are significantly associated with poor HVA even in urban Western India despite relatively easy access to affordable eye care facilities.     

灯箱视力表与电脑视力表临床应用对比研究

目的:通过与灯箱视力表的对比研究了解电脑视力表的临床使用价值。方法:选取初三学生63例(126眼)同时用灯箱和电脑视力表进行远用视力检测,对视力检测值进行配对检验。结果:两种视力表检测值的t检验等于1.2671,P>0.20,两种视力表的检测在统计学上无显著性差异。结论:电脑视力表和灯箱视力表在临床上具有相同的应用价值,可以推广和普及。     

灯箱视力表与Freiburg电子视力表应用对比研究

目的 比较灯箱视力表与Freiburg电子视力表结果的一致性与可重复性,评价Freiburg电子视力表的临床应用价值。设计 诊断性技术评价。研究对象 空军杭州航空医学鉴定训练中心的工作人员86例,平均年龄（26.3±2.1）岁。方法 所有入选者均随机由2位固定检查者分别使用灯箱视力表和Freiburg电子视力表进行检查,两种视力表检查的顺序随机决定。所有检查均在同一房间内完成,房间内亮度小于3 lux。检查距离均为3 m。对不同视力表间与检查者间测量重复性采用配对t检验比较结果的差别并计算相关系数r值。主要指标 使用两种视力表获得的logMAR视力。结果 在检查者一,用灯箱视力表查,被检者logMAR视力为0.19±0.23,Freiburg电子视力表0.20±0.15,两者差值为-0.011±0.141,差异无统计学意义（t=-0.741, P=0.461）,但有显著相关性（r=0.808,P=0.000）。在检查者二,用灯箱视力表查,被检者logMAR视力为0.32±0.25,Freiburg电子视力表为0.20±0.15,两者差值为-0.118±0.151,差异有统计学意义（t=7.191, P=0.000）及显著相关性（r=0.810,P=0.000）。均用灯箱视力表,检查者一、二的差异有统计学意义（F=11.872,P=0.001）,两者显著相关（r=0.938,P=0.000）。而均用Freiburg电子视力表,检查者一、二的差异无统计学意义（F=0.019,P=0.890）,两者显著相关（r=0.986,P=0.000）。结论 Freiburg电子视力表受检查者因素的影响小于灯箱视力表,其在不同测量者间的可重复性优于灯箱视力表。（眼科, 2013, 22: 117-120）     

Saving space: Comparing mini - logMAR with standard logMAR visual acuity

Purpose:Assessing visual acuity (VA) is the cornerstone of an ophthalmic workup and needs VA charts in a four or six meters space. The objective of this study was to compare the performance of distant VA (DVA) on one meter mini-logMAR (MLM) with a standard six meter logMAR (SLM) chart.Methods:We developed a MLM chart to be used at 1 m with +1.0 D spectacles, by reducing the SLM chart designed for 6 meters, to 1/6^th its size, using AutoCAD version 2014. On an initial cohort, we obtained DVA on the two charts by optometrist trainees, masked to the outcomes on the different tests. We performed regression and checked agreement between the two measurements. Subsequently, on a new cohort, we validated the performance of the MLM.Results:Of the 56 initial subjects, mean DVA with SLM was 0.44 ± 0.13 and with MLM was 0.45 ± 0.13; mean difference of -0.01 ± 0.02, 95%CI: 0.007 to 0.018; P < 0.0001 on paired t-test. There was a significant correlation: r = 0.99; r² = 0.98, P < 0.0001. On an average, DVA with MLM was less than a letter worse than with SLM. The regression formula obtained: SLM DVA = -0.1312 + 1.0014 x (MLM DVA). The validation study revealed no significant difference (P = 0.29) between the predicted standard DVA calculated by the regression formula and the actual standard.Conclusion:We suggest that we can deduce distance logMAR VA from a mini-logMAR chart as devised and used by us. This will take less space, be portable and allow congenial interaction with patients.     

近视性离焦对静态视力和动态视力的影响

背景光学离焦对静态视力能产生明显的影响,但是对动态视力的影响尚未见报道。目的研究近视性离焦对静态视力和动态视力影响的差异及其机制。方法研究纳入40名志愿者,包括20名平均年龄（27．40±1．64）岁的成人和20名平均年龄（11．70±1．49）岁的儿童。受检眼排除眼科疾患,最佳矫正视力≥1．0D,散光≤0．75D,双眼屈光参差〈1．50D。受检眼在远用屈光全部矫正的基础上分别加戴＋1．00、＋1．50、＋2．00、＋2．50D的正透镜进行离焦,使用自制的DVA-I动态视力测试仪和静态视力表测试受试者的动态视力和静态视力。结果成人组和儿童组的静态视力和动态视力均随着离焦度的增加而下降,4种离焦度的总体差异均有统计学意义（F=506．907,P=0．000）;成人组和儿童组在各离焦度的动态视力与静态视力间的比较差异均无统计学意义（P〉0．05）;线性回归分析表明,静态视力或动态视力与离焦度间均呈阳性相关（R2=0．819,t=26．720,P=0．000;R2=0．826,t=27．420,P=0．000）;离焦度与静态视力的斜率和截距均明显陡于离焦度与动态视力的斜度和截距（F=34．180,P=0．000;F=1005．560,P=0．001）。结论等量离焦对静态视力和动态视力的影响不同,推测动态视力不仅与屈光系统有关,还可能与其他影响因素有关。     

Development of Pocket Vision Screener and its effectiveness at screening visual acuity deficits

Aim:The aim was to construct a visual acuity chart and find its effectiveness at screening visual acuity deficits.Results:The mean age of the subjects was 43 ± 17 years. Subjects were classified as normal or deficient based on the logMAR visual acuity measurement. The screener was found to have 81% sensitivity, 94% specificity. The positive and negative predictive values were found to be 91% and 87%, respectively. A significant difference (P < 0.001) was found in the time taken to record visual acuity using both the charts.Conclusion:The Pocket Vision Screener can be used as a quick and accurate tool to screen subjects for visual acuity deficits, being highly sensitive, specific, and cost-effective.     

Automated determination of distance visual acuity: towards teleophthalmology services

Purpose: The aim of this study was to evaluate the visual acuity scores of a computer‐based visual function testing (CVFT) system. The automated chart uses logMAR notation (logarithm of the minimum angle of resolution) and randomised tilting E as optotype. The test was conducted using a laptop computer. Methods: This prospective, clinic‐based, test validation study was based on a model of repeatability in two observations. The right eyes of a total of 104 participants were randomly tested with both CVFT and the manual, gold standard Early Treatment of Diabetic Retinopathy Study (ETDRS) chart. Results: The mean difference between CVFT and ETDRS was ‐0.01 ± 0.11 (SD) logMAR units. The Spearman Rank correlation coefficient (r) between the absolute difference and the average was 0.35. The average time for testing one eye was 54.7 ± 11.89 seconds. The mean difference between two consecutive, repeated CVFT tests in the same eye was 0.02 ± 0.07 logMAR units (paired t‐test p = 0.046). Conclusions: A novel, automated visual acuity testing application is reported. This automated system should be a useful tool for mass screening of visual impairment in rural and remote regions with its ease of use and shorter testing time.     

A comparison of visual acuity measured by ETDRS chart and Standard Logarithmic Visual Acuity chart among outpatients

AIM:To compare the results of visual acuity(VA)measured by Early Treatment Diabetic Retinopathy Study(ETDRS)chart,5 m Standard Logarithm Visual Acuity(5 SL)chart,and 2.5 m Standard Logarithm Visual Acuity(2.5 SL)chart in outpatients of age 12-80 y.METHODS:Each patient(totally 2000 outpatients)had both eyes tested with ETDRS chart at 4 m,5 SL chart at 5 m,and 2.5 SL chart at 2.5 m in random order.The VA values of outpatients were categorized by ages.VA values were expressed by log MAR recording method.RESULTS:The mean VA results of ETDRS charts,5 SL,and 2.5 SL chart were 0.52±0.28,0.50±0.30,and 0.46±0.28 log MAR,respectively.There was a statistically significant difference in the three eye charts in the whole group(P<0.001).For all subjects,the correlation of VA tested with three charts was statistically significant(Spearman correlation coefficient=0.944,0.937,0.946,all P<0.001).Bland–Altman analysis shows the 95%limits of agreement between the 5 SL and 2.5 SL chart were-0.182 to 0.210,-0.139 to 0.251,and-0.151 to 0.235 log MAR,respectively.CONCLUSION:The agreement between the three eye charts is not high.The VA measured by 5 SL chart is slightly better than that by ETDRS chart and 5 SL chart would be a suitable alternative when ETDRS chart are not available in the clinical situation.The VA measured by 2.5 SL chart is about 0.5 line better than VA tested with ETDRS chart,which may overestimate VA.     

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。     

Chart memory and visual acuity measurement

BACKGROUND: A small, but statistically significant, improvement has previously been demonstrated when retesting visual acuity within 24 hours. Because letter chart testing procedures are familiar to most adult patients, this improvement may be due to memory of the chart letter subset, rather than increased familiarity with the test procedure. Chart letter subset memory does not appear to have previously been measured directly. METHODS: A letter recognition task was used to measure chart letter subset memory for groups of routine clinical patients. Comparisons were made between assessments after a single acuity measurement and assessments at increasing intervals after a routine examination involving several references to the same letter chart for both eyes. RESULTS: The recognition score for the 'one-minute-after a single acuity measurement group' was an average of 2.5 letters (range 0.7 to 4.7). Low levels of chart letter subset memory were found to persist for 10 days. CONCLUSION: The chart letter subset memory found is consistent with enhanced acuity scores that occur on retesting. Scores appear likely to have a greater chance of enhancement for a second eye measurement when it follows immediately after the first. Similarly, scores at the end of a full examination may be enhanced by memory that is accumulated during multiple measurements for both eyes using the same chart. Chart memory may be acquired when acuity is measured frequently in monitoring the progress of disease. Chart memory, or its loss over time, may contribute to measurement imprecision and associated expansion of the confidence limits for significant change in acuity.     

视力表的标准化

回顾了我国多年来视力表在设计、制作和使用中存在的问题,着重分析了目前使用最普遍的两种视力表《国际标准视力表》和《标准对数视力表》存在的问题。认为视力表视力检查是评价人眼主觉视力简便而实用的方法,它只对视觉功能做粗略的评估,简便和实用是其最大的特点。因此今后在设计和使用视力表时应考虑:①设计合理、简便实用、兼顾习惯、国际接轨、全国统一;②除有通用表外,另设计出供3岁左右儿童使用的视力表。建议国家标准局在业务主管部门(卫生部及中华医学会)协助下,组织视力表问题研究专题组,广泛征求意见与建议,提出规范统一的方案。     

儿童图形视力表与Teller视敏锐度卡在婴幼儿视力检测中应用分析

目的 探讨儿童图形视力表、Teller视敏锐度卡在婴幼儿视力检测中的可行性和可靠性.方法 对2010年1～12月在北京同仁医院眼科斜弱视门诊就诊的185例患儿,分别使用儿童图形视力表检测2～3岁患儿59例118只眼,用Teller视敏锐度卡检测5个月至2岁患儿126例252只眼.每2个月龄为一组,共分为10组进行视力检测,并对其检测结果进行分析评估.结果 应用儿童图形视力表检测视力结果:0.1～0.2者为14.41％ (17/118),0.3～0.5者为64.41％ (76/118),0.6者为21.19％ (25/118);应用Teller视敏锐度卡检测视力结果:13 cy/cm为21.43％ (54/252),4.8～9.8 cy/cm为20.63％(52/252),1.3～3.2 cy/cm为42.86％ (108/252),0.86 cy/cm为10.71％ (27/252),0.43 cy/cm为4.37％(11/252).结论 儿童图形视力表、Teller视敏锐度卡是一种安全、快速、经济、有效地婴幼儿视力评估检测系统,较常规检查能更早地发现低于该年龄段视力发育水平的低常视力,同时可以对眼部先天性疾患的婴幼儿低视力进行早期干预并制定跟踪治疗方案.     

红色视力表远距离视功能训练在近视性弱视治疗中的疗效分析

目的：对比观察分析红色视力表远距离视功能训练在近视性弱视治疗中的疗效。方法近视性弱视患儿甲、乙两组共112例212眼,甲组62例117眼,年龄4-12岁（5.71±1.78岁）,乙组50例95眼,年龄3-12岁（5.96±1.83岁）;其中甲组轻度、中度、高度近视眼分别为21眼（17.95%）、67眼（57.26%）、29眼（24.79%）,乙组为18眼（18.95%）、55眼（57.89%）、22眼（23.16%）（χ2＝0.09,P〉0.05）;甲组轻度、中度、重度弱视眼分别为30眼（23.15%）、64眼（54.70%）、23眼（19.66%）;乙组为24眼（25.26%）、54眼（56.84%）、17眼（17.89%）（χ2＝0.133,P〉0.05）;甲组病例采用短小遮盖＋近距离视功能训练;乙组病例采用短小遮盖＋红色视力表远距离视功能训练,所有病例治疗随访时间17个月,对比分析两种治疗方法在近视性弱视治疗中的疗效。结果甲组基本治愈率为39.32%,有效率为43.59%,无效率为17.09%;乙组基本治愈率为47.37%,有效率为36.84%,无效率为15.79%,统计学检验差异无显著性（χ2＝1.434,P〉0.05）;甲乙两组治疗后轻、中、高度近视眼数分别为：4眼（3.42%）、65眼（55.56%）、48眼（41.03%）和5眼（5.26%）、67眼（70.53%）、23眼（24.21%）统计学检验差异有显著性（χ2＝6.734,P〈0.05）。结论红色视力表远距离视功能训练治疗近视性弱视疗效好,同时能更好的减少治疗后弱视眼近视度数的发展。