Prescribing near magnification for low vision patients

Most patients with low vision request help with reading. Despite improvements in the assessment of visual functions, determining the appropriate magnification for reading still often involves a trial and error approach. Recent research has shown that with accurate and systematic assessments of vision, the required magnification can be predicted but this magnification needs to be much higher than has been previously recommended. This paper presents a systematic approach to enable practitioners to determine the power of a near addition or simple magnifier needed to assist patients with mild or moderate low vision who may present seeking help for reading. Guidelines for appropriate referral to low vision services are also provided.     

A survey of low vision patients in Hong Kong

This report provides some statistical information based on clinical data gathered on low vision patients who attended the low vision clinic of the Hong Kong Society for the Blind in the first three years of its operation. In this period, low vision devices were prescribed for 393 patients (46.5 per cent of the sample). The most commonly prescribed aids were simple magnifiers and distance telescopes. Cataract was the major cause of low vision.     

Stand magnifiers for low vision: description,prescription, assessment

Stand magnifiers are still one of the most commonly prescribed classes of low vision devices. Their performance can be difficult to understand because stand magnifiers usually do not give an image at infinity. This review summarises the methods of describing image enlargement for stand magnifiers, emphasising their relationship to equivalent viewing distance (EVD). This is done in terms of the underlying optical equations, and measurement methods, and methods of prescribing. In the past, methods of determining EVD have been somewhat indirect, requiring accurate measurement of lens power, and image position. The use of digital photography provides an alternative, more direct, simpler method of determining EVD, which can be accomplished in-office. This method is described and it is demonstrated how it gives comparable results to older methods with small, clinically non-meaningful differences, that may be due to differences in image distance reference planes. Describing the performance of stand magnifiers in terms of their dioptric power, or in terms of ‘nominal magnification’ or ‘trade magnification’, is imprecise and misleading. It is better to use indices such as equivalent viewing power and EVD, which take into account the magnifier dioptric power, the image position of the magnifier and the distance a patient is from the magnifier. While EVD is a useful index for prescribing stand magnifiers, manufacturers do not always provide sufficient technical details to determine EVD for their stand magnifiers, and available tables of EVDs are more than a decade old and are likely to need updating. Photographic comparison provides a method for determining EVD, and this method can also be applied to other low vision devices.     

New stand magnifiers do not meet rated levels of performance

A new range of stand magnifiers has been released by the COIL company in the United Kingdom. Examination of these magnifiers reveals that they fail to deliver the rated magnifications labelled prominently on the appliances, as a result of the manufacturer's conformance with the requirements of the German DIN standard and the use of back vertex power (F'_v) rather than equivalent dioptric power (F_m) of the magnifier. In this study we provide information on the optometric parameters of these new stand magnifiers that will assist the more accurate specification of improvements in vision expected from their use.     

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.     

助视器在低视力儿童中的应用

目的探讨自行来院就诊低视力儿童的病因及低视力康复疗效,方法对门诊筛查视力低常儿童进行散瞳验光、眼底等检查,诊断为低视力者,应用远用、近用助视器进行视力康复训练;结果在25例低视力儿童中,(1)病因以先天性眼球震颤合并屈光不正多见,占76.00%;(2)20例选择康复远视力,最佳矫正远视力在0.1～<0.3,用4X、6X单筒近距远距观察镜康复远视力达到≥1.0,脱残率100%;(3)5例选择康复近视力,最佳矫正近视力<0.3~0.1,经过使用2.5X、3X、4X直柄放大镜和2.5X木马放大镜康复近视力≥0.5,近视力康复有效率100%。结论应用助视器能有效提高低视力儿童的远、近视力和视觉质量,让患儿有机会具备接受正常教育的用眼条件,因此,早发现、早诊断、早矫正、早康复,对低视力儿童的身心健康、拓宽知识领域、升学、就业具有积极地意义。     

原发性视网膜色素变性的低视力患者配戴琥珀色滤光镜前后视觉功能变化

目的:对比观察原发性视网膜色素变性(RP)的低视力患者在配戴琥珀色滤光镜前后的视觉功能变化。方法:自身前后对照研究。收集2021-08/2022-03就诊于西安市第一医院眼科门诊诊断为原发性RP的低视力患者30例60眼。记录配戴琥珀色滤光镜前后裸眼远视力(UCDVA)、最佳矫正远视力(BCDVA)、裸眼近视力(UCNVA)、最佳矫正近视力(BCNVA)、视野和FM-100色觉,并分别在明室环境、暗室环境和暗室伴眩光环境进行对比敏感度检查并记录,分析配戴前后上述视功能参数的变化。结果:配戴琥珀色滤光镜后UCDVA和BCDVA均优于配戴前(t=-2.32,P<0.001;t=-6.77,P<0.001),而UCNVA和BCNVA在戴镜前后差异无统计学意义。戴镜后的视野指数(VFI)低于配戴前(t=8.62,P<0.001)、视野平均缺损值(MD)大于配戴前(t=7.73,P<0.001),FM100色棋检查显示TES和多个分区PES均高于戴镜前(P<0.001)。配戴后明室环境、暗室伴眩光环境下各频段CS值较配戴前提高(P<0.001),暗室不伴眩光环境...     

Aspects of low vision care in Hong Kong

In this paper, low vision care facilities in Hong Kong are described. In addition, some low vision case reports from Hong Kong are presented.     

Improving interactive facility with vision training

The measurement of accommodative facility has gained acceptance in optometric examinations because it can provide valuable information on the dynamics of accommodation. Accommodative infacility is usually treated by prescribing various orthoptic exercises. This study arose from a need to investigate the effects of specific vision training procedures on binocular accommodative facility (interactive facility). The results indicate that even relatively short periods of accommodative rock training can improve the level of interactive facility.     

Changes in fixation in the presence of prism monitored with a confocal scanning laser ophthalmoscope

Background: The main optical effect of an ophthalmic prism is to deviate uniformly the entire field of view seen through the prism, resulting in an equal eye movement, if fixation on the same object is to be maintained. Conversely, it has been suggested that, in the case of low vision due to central scotoma, the eye changes its eccentric viewing behaviour when a prism is introduced, that is, the eye remains stationary with a change of retinal image location. Method: A new method is described in which retinal image position was recorded with a confocal scanning laser ophthalmoscope in four experimental conditions. Results: Results showed that the normally‐sighted eye rotates rapidly to compensate for the introduction of a prism. Conclusion: Future studies are required involving subjects with central scotoma but it is likely that many subjects with low vision will also refixate behind a prism and that the prescribing and wearing of bilateral prism in cases of central vision loss will have limited effectiveness in the demonstration or training of eccentric viewing.     

A holistic model of low vision care for improving vision-related quality of life

Vision impairment can have a significant impact on the wellbeing and quality of life of an individual. Vision rehabilitation has the potential to improve these areas; however, four in five patients with vision impairment are not being referred to the appropriate services. Barriers to on-referral include, but are not limited to: (1) misunderstandings by both practitioners and patients alike regarding which individuals with vision impairment might benefit or qualify for low vision services; (2) lack of awareness of available services; (3) unfamiliarity with practice guidelines; (4) miscommunication between practitioners and patients; (5) required patient travel or limitations in access; and (6) the perceived costs of goods and services. Further, current referral patterns do not represent a holistic patient-centric approach. Vision-related quality of life questionnaires are tools which can assist health professionals in providing optimal individualised care. This review explores current evidence regarding low vision service delivery within Australia and globally, the impact of vision impairment on activities of daily living, the instruments used for the assessment of vision-related quality of life (VRQOL), competing priorities of individual needs in low vision services and rehabilitation, and provides recommendations for a more patient-centred model of care.     

156例老年低视力病因分析

目的分析我院低视力门诊中老年低视力的主要致病原因,为老年低视力患者的视觉康复及预防奠定基础。方法采用WHO1996的低视力标准,随机序列选取低视力门诊156例(310眼)老年低视力患者,对其进行常规的眼科检查,记录最佳矫正视力和所患眼病,统计分析所患眼病的种类和分布情况。结果引起老年低视力的主要眼病有高度近视眼病71例(占45.51%),黄斑病变29例(占18.59%),糖尿病性视网膜病变和青光眼各17例(占10.90%),视网膜脱离16例(占10.26%)等。结论高度近视眼病、黄斑病变应成为老年低视力的防治重点,农村老年低视力患者是重点防治对象。     

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。     

Critical issues in implementing low vision care in the Asia-Pacific region

Two-thirds of the world's population with low vision resides in the Asia-Pacific region. Provision of comprehensive low vision services is important to improve vision-related quality of life (QoL) for people with this condition. This review outlines the critical issues and challenges facing the provision of low vision services in the Asia-Pacific region. The review offers possible strategies to tackle these issues and challenges facing service providers and policy makers in lieu of Vision 2020 strategies in this area. Pertinent findings from the global survey of low vision services and extensive ground work conducted in the region are used; in addition, a discussion on the availability of services, human resources and training, and funding and the future sustainability of low vision care will be covered. In summary, current issues and challenges facing the region are the lack of specific evidence-based data, access, appropriate equipment and facilities, human resources, funding, and sustainability. These issues are inextricably interlinked and thus cannot be addressed in isolation. The solutions proposed cover all areas of the VISION 2020 strategy that include service delivery, human resources, infrastructure and equipment, advocacy and partnership; and include provision of comprehensive care via vertical and horizontal integration; strengthening primary level care in the community; providing formal and informal training to enable task shifting and capacity building; and promoting strong government and private sector partnership to achieve long-term service financial sustainability.     

视觉性助视器在低视力阅读康复中的作用

目前关于不同类型助视器在低视力阅读康复效能方面的研究结果不尽一致,本文通过文献复习,综述了当前各种视觉性助视器在低视力患者阅读康复方面的作用,包括大字印刷和放大镜的作用,使用不同光学助视器的阅读比较,使用不同电子助视器的阅读比较,使用光学助视器与电子助视器阅读的比较,非光学助视器影响阅读的相关因素如对比敏感度、阅读材料的印刷参数(行间距、字间距、字母间距、字体大小及长度、每行字数等).     

土耳其低视力患者的病因及特征

目的：探讨土耳其配戴助视器的低视力患者的病因和特点,及其与父母近亲结婚是否有关系。 方法：回顾性研究了2009/2013年间伊斯坦布尔诊所接受236例低视力患者。分析年龄、性别分布、低视力原因、近亲结婚、低视力辅助类型规定及视力变化。在回顾性研究中,根据世界卫生组织定义基于最佳矫正视力将视力分为（失明,视力〈20/400;视力严重受损,视力〈20/200～20/400;视力轻度到中度受损,视力〈20/60～20/200）。基于双眼主要病因,根据国际疾病分类第十版可以确定失明和低视力的病因。根据视力和患者需求规定了视力辅助,并使用平均值依标准差和频率对数据进行了描述。 结果：研究包括236例患者,65%为男性,平均年龄为38.5依24.2岁（年龄范围6～95岁）,男性多于女性。年龄在15～30岁（35.6%）之间是最大的年龄群体。轻度至中度视力受损患者为122例,严重视力受损患者为84例,失明患者为30例,他们分别占总人数的51.6%、35.6%和12.7%。脉络膜疾病和视网膜疾病（62.7%）是导致视力低下的主要原因。老年低视力患者黄斑变性逐渐成为视力低下的首要原因（61.3%）。造成视力低下的原因有视网膜和脉络膜疾病（62.7%）,眼球震颤（23.7%）,视神经和视神经束疾病（11%）,先天性白内障（0.8%）及青光眼（1.7%）。88例患者（37.3%）为伽利略类型,116例患者（49.2%）为开普勒类型。18例患者（7.6%）在接受LVA后视力无明显改善。14例患者被准许使用放大镜矫正视力。在大多数患者中,使用LVA的近视和远视患者视力均得到改善。62例近亲结婚患者占总人数的26.3%。 结论：14岁以上患者视力受损主要原因是视网膜和脉络膜疾病,15岁以下的患者常见原因为眼球震颤。在近亲结婚群体中黄斑营养不良和色素性视网膜炎患者显著增高。研究疾病病因学的遗传非常有效,因此,近亲结婚在土耳其仍是一大问题。     

新型近用连续变焦电子助视器在低视力和盲康复中的应用

目的比较新型近用连续变焦电子助视器和近用光学助视器在低视力和盲康复中的有效性。方法前瞻性病例对照研究。19例低视力患者和14例盲患者分别使用近用光学助视器和近用连续变焦电子助视器阅读报纸里的新闻文章,记录使用2种仪器后的近视力、阅读速度和阅读持续时间,采用配对t检验对检查结果进行统计学分析。结果所有患者使用近用光学助视器和近用连续变焦电子助视器后近视力相比,差异有统计学意义（t=-2.392,P＜0.05）;盲患者和低视力患者分别使用2种助视器后近视力比较,差异有显著统计学意义（t=-7.433、-8.721,P＜0.01）。所有患者和盲患者使用近用光学助视器和近用连续变焦电子助视器后阅读速度相比,差异有显著的统计学意义（t=-4.290、-6.728,P＜0.01）;低视力患者分别使用2种助视器后阅读速度比较,差异无统计学意义（t=-1.534,P＞0.05）。所有患者、盲患者以及低视力患者分别使用近用光学助视器和近用连续变焦电子助视器后阅读持续时间相比,差异有显著统计学意义（t=-8.211、-6.137、-6.007,P＜0.01）。结论新型近用连续变焦电子助视器与传统的近用光学助视器相比,更能提高患者的近视力和改善阅读能力。