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。     

Spatial vision in older adults: perceptual changes and neural bases

Purpose

The number of older adults is rapidly increasing internationally, leading to a significant increase in research on how healthy ageing impacts vision. Most clinical assessments of spatial vision involve simple detection (letter acuity, grating contrast sensitivity, perimetry). However, most natural visual environments are more spatially complicated, requiring contrast discrimination, and the delineation of object boundaries and contours, which are typically present on non‐uniform backgrounds. In this review we discuss recent research that reports on the effects of normal ageing on these more complex visual functions, specifically in the context of recent neurophysiological studies.

Recent findings

Recent research has concentrated on understanding the effects of healthy ageing on neural responses within the visual pathway in animal models. Such neurophysiological research has led to numerous, subsequently tested, hypotheses regarding the likely impact of healthy human ageing on specific aspects of spatial vision.

Summary

Healthy normal ageing impacts significantly on spatial visual information processing from the retina through to visual cortex. Some human data validates that obtained from studies of animal physiology, however some findings indicate that rethinking of presumed neural substrates is required. Notably, not all spatial visual processes are altered by age. Healthy normal ageing impacts significantly on some spatial visual processes (in particular centre‐surround tasks), but leaves contrast discrimination, contrast adaptation, and orientation discrimination relatively intact. The study of older adult vision contributes to knowledge of the brain mechanisms altered by the ageing process, can provide practical information regarding visual environments that older adults may find challenging, and may lead to new methods of assessing visual performance in clinical environments.     

Visual acuity testing. From the laboratory to the clinic

The need for precision in visual acuity assessment for low vision research led to the design of the Bailey–Lovie letter chart. This paper describes the decisions behind the design principles used and how the logarithmic progression of sizes led to the development of the logMAR designation of visual acuity and the improved sensitivity gained from letter-by-letter scoring. While the principles have since been adopted by most major clinical research studies and for use in most low vision clinics, use of charts of this design and application of letter-by-letter scoring are also important for the accurate assessment of visual acuity in any clinical setting. We discuss the test protocols that should be applied to visual acuity testing and the use of other tests for assessing profound low vision when the limits of visual acuity measurement by letter charts are reached.     

Principles of modern low vision rehabilitation

Low vision rehabilitation is a new emerging subspecialty drawing from the traditional fields of ophthalmology, optometry, occupational therapy, and sociology, with an ever-increasing impact on our customary concepts of research, education, and services for the visually impaired patient. A multidisciplinary approach and coordinated effort are necessary to take advantage of new scientific advances and achieve optimal results for the patient. Accordingly, the intent of this paper is to outline the principles and details of a modern low vision rehabilitation service. All rehabilitation attempts must start with a first hand interview (the intake) for assessing functionality and priority tasks for rehabilitation, as well as assessing the patient's all-important cognitive skills. The assessment of residual visual functions follows the intake and offers a unique opportunity to measure, evaluate, and document accurately the extent of functional loss sustained by the patient from disease. An accurate assessment of residual visual functions includes assessment of visual acuity, contrast sensitivity, binocularity, refractive errors, perimetry, oculomotor functions, cortical visual integration, and light characteristics affecting visual functions. Functional vision assessment in low vision rehabilitation measures how well one uses residual visual functions to perform routine tasks, using different items under various conditions, throughout the day. Of the many functional vision skills known, reading skills is an obligatory item for all low vision rehabilitation assessments. Results of assessment guide rehabilitation professionals in developing rehabilitation plans for the individual and recommending appropriate low vision devices. The outcome from assessing residual visual functions is detection of visual functions that can be improved with the use of optical devices. Methods for prescribing devices such as image relocation with prisms to a preferred retinal locus, field displacement to primary gaze position, field expansion, and manipulation of light are practiced today in addition to, or instead of, magnification. Correction of refractive errors, occlusion therapy, enhancement of oculomotor skills, and field restitution are additional methods now available for prescribing devices leading to rehabilitation of visual functions. The outcome from assessing residual functional vision is detection of functional vision that can be improved with the use of vision therapy training. After restoration of optimal residual visual functions is achieved with optical devices, one can follow with training programs for restoration of lost vision-related skills. If an optical dispensary is available where prescribing of low vision devices routinely take place, this will help ensure familiarity and specialization of the dispensary and staff with low vision devices and their special dispensing requirements. The dispensing of low vision devices is an opportunity to introduce the device to the patient, train the patient in the correct use of the device for the task selected, and create a direct and continuous connection with the patient until the next encounter. Following assessment, prescribing, and dispensing of devices, a low vision practitioner, ophthalmologist or optometrist, is responsible for recommending and prescribing vision therapy training to improve residual functional vision. An attempt to present a template for a comprehensive modern low vision rehabilitation practice is made here by summarizing scientific developments in the field and stressing the multidisciplinary involvement required for this kind of practice. It is hoped that this paper and other initiatives from colleagues, the public, and government will promote and raise awareness of modern low vision rehabilitation for the benefit of all.     

The role of contrast sensitivity charts and contrast letter charts in clinical practice

Practitioners frequently make clinical decisions based on changes in visual acuity. However, acuity is recognised to be only one aspect of visual performance. In recent years, a number of clinical chart-based tests which measure different aspects of vision based on contrast sensitivity have become available. These tests allow a more subtle investigation of visual problems. In this review of currently available contrast sensitivity charts and contrast letter charts, we examine their clinical application and some of the problems which may be encountered in the use of these tests in practice. This should permit a better understanding of some patients' visual problems, better clinical decision making and a better understanding of studies which report visual performance measurements. Information on currently available equipment and a list of suppliers in Australia is included. (Clin Exp Optom 1995; 78: 2: 43–57)     

Detection and identification of crowded mirror-image letters in normal peripheral vision

Performance for discriminating single mirror-image letters in peripheral vision can be as good as that in central vision, provided that letter size is scaled appropriately [Higgins, K. E., Arditi, A., & Knoblauch, K. (1996). Detection and identification of mirror-image letter pairs in central and peripheral vision. Vision Research, 36, 331-337]. In this study, we asked whether or not there is a reduction in performance for discriminating mirror-image letters when the letters are flanked closely by other letters, compared with unflanked (single) letters; and if so, whether or not this effect is greater in peripheral than in central vision. We compared contrast thresholds for detecting and identifying mirror-image letters “b” and “d” for a range of letter separations, at the fovea and 10° eccentricity, for letters that were scaled in size. For comparison, thresholds were also determined for a pair of non-mirror-image letters “o” and “x”. Our principal finding is that there is an additional loss in sensitivity for identifying mirror-image letters (“bd”), compared with non-mirror-image letters (“ox”), when the letters are flanked closely by other letters. The effect is greater in peripheral than central vision. An auxiliary experiment comparing thresholds for letters “d” and “q” vs. “b” and “d” shows that the additional loss in sensitivity for identifying crowded mirror-image letters cannot be attributed to the similarity in letter features between the two letters, but instead, is specific to the axis of symmetry. Our results suggest that in the presence of proximal objects, there is a specific loss in sensitivity for processing broad-band left-right mirror images in peripheral vision.     

The effect of relative distance enlargement on visual acuity in the visually impaired

Background : Prescribing magnification is typically based on distance or near visual acuity. This presumes a constant minimum angle of visual resolution with working distance and therefore enlargement of an object moved to a shorter working distance (relative distance enlargement). This study examines this premise in a visually impaired population. Methods : Distance letter visual acuity was measured prospectively for 380 low vision patients (distance visual acuity between 0.3 and 2.1 logMAR) over the age of 57 years, along with near word visual acuity at an appropriate distance for near lens additions from +4 D to +20 D. Demographic information, the disease causing low vision, contrast sensitivity, visual field and psychological status were also recorded. Results : Distance letter acuity was significantly related to (r = 0.84) but on average 0.1 ' 0.2 logMAR better (1 ' 2 lines on a logMAR chart) than near word acuity at 25 cm with a +4 D lens addition. In 39.8 per cent of patients, near word acuity was more than 0.1 logMAR worse than distance letter acuity. In 11.0 per cent of subjects, near visual acuity was more than 0.1 logMAR better than distance letter acuity. The group with near word acuity worse than distance letter acuity also had lower contrast sensitivity. The group with near word acuity better than distance letter aculty was less likely to have age‐related macular degeneration. Smaller print size could be read by reducing working distance (achieved by using higher near lens additions) in 86.1 per cent, although not by as much as predicted by geometric progression in 14.5 per cent. Discussion : Although distance letter and near word acuity are highly related, they are on average 1 logMAR line different and this varies significantly between individuals. Near word acuity did not increase linearly with relative distance enlargement in approximately one in seven visually impaired, suggesting that the measurement of visual resolution over a range of working distances will assist appropriate prescribing of magnification aids.     

Task Complexity and Visual Acuity in Senile Macular Degeneration

ABSTRACT The effects of choice of test object and inter-symbol spacing (contour interaction) on the measurement of low visual acuities was investigated. Visual acuities of sixteen subjects with senile macular degeneration and five age-matched normal subjects were measured using different test targets of varying complexities. Visual acuity of both groups of subjects decreased with increasing task complexity but the trend was more marked for the low vision subjects. However, within the low vision group, the complexity effect was not dependent on the level of visual acuity. This study showed that visual acuity of persons with senile macular degeneration can be measured equally well with single letters, constant contour interaction Landolt rings, or the Bailey-Lovie letter chart but the test used should be specified. Grating targets and word charts measure different visual functions from standard visual acuity tests.     

Visual outcomes following vitrectomy and peeling of epiretinal membrane

BACKGROUND: Visual outcomes of patients following vitrectomy and peeling of visually significant epiretinal membranes were assessed to determine the influence of specific perioperative factors and surgical complications on final visual acuity and functional vision. METHODS: In an unmatched, consecutive surgical series, vitrectomy and membrane peeling were performed on 125 eyes of 123 patients with visually significant macular epiretinal membranes. Patients were followed for 6-36 months. Visual outcome measures included postoperative logMAR visual acuity, change in visual acuity and functional vision tasks evaluated by questionnaire. Perioperative factors including duration of symptoms, preoperative visual acuity, aetiology, membrane type and leakage on fundal fluorescein angiogram were correlated with final visual outcomes. RESULTS: Visual acuity improved by a mean of 0.31 A+/- 0.21 units (three lines of vision). In 104 cases (83%), visual acuity improved in patients by two lines or more, with 20 cases (16%) having unchanged acuity and one case (1%) having worse acuity. Ninety-three per cent of interviewed cases reported improvement in functional vision, especially reduction of distortion. Cataract was observed in 52 cases (52% of phakic eyes) postoperatively compared with 19 cases (19%) preoperatively. Postoperative visual acuity correlated with preoperative visual acuity. Patients with worse preoperative vision recorded greater visual improvement following surgery. No other perioperative factors were found to have a prognostic value in this study. CONCLUSION: Epiretinal membrane peeling improves vision in the majority of patients with significant symptoms, even if preoperative visual acuity is not substantially reduced. Surgery improves functional vision including metamorphopsia not measurable by visual acuity, and thus assessment of functional vision should be included in surgical case planning.     

助视器在视残患儿中的应用

目的 观察远用和近用眼镜器在视残患儿中的应用效果。方法 对１３９例视残患儿分别配戴２．５倍国产望画视器及＋８．００～＋４０．００Ｄ近用眼镜助视器进行观察。结果 ３１例（２２．３％）配载远用眼镜助视器的视残患儿,远视力≥０．５;７４例（５３．２％）配戴近用镜助视器的视残患儿,近视力≥０．５。结论 眼镜助视器在低力门诊是必备的且有效的,可提高患儿视力,改善视功能,可推动视觉康复工作,从而促进特教事业的     

不同程度视力残疾患者应用助视器的康复效果

目的探讨不同程度视力残疾患者在应用光学和电子助视器后远、近视力的康复效果。方法对天津医科大学眼科中心低视力康复中心283例(9～79岁)视力残疾患者按视力残疾程度分为盲(110例)和低视力(173例)两组。分别比较两组应用Keplerian及Galilean望远镜前后远视力及脱残率的差异,以及应用带光源手持放大镜、近用眼镜式助视器及电子助视器后阅读成功率的差异。应用助视器前后的远视力差异采用配对t检验,脱残率及阅读成功率的差异采用χ2检验。结果两组应用两种远用助视器后远视力均有所提高,差异均有统计学意义(均为P<0.01);盲目组应用Keplerian及Galilean望远镜后脱残率分别为10.9%和9.1%,低视力组分别为76.3%和77.5%,差异均无统计学意义(P=0.823、P=0.899)。两组应用电子助视器阅读成功率(26.4%、86.1%)均高于带光源手持放大镜(13.6%、71.1%)及近用眼镜式助视器(15.5%、68.2%),差异均有统计学意义(P=0.031、P<0.01)。结论助视器能帮助视力残疾患者有效利用其残余视力,改善视功能及提高生活质量,是视力残疾患者康复的有效手段,应加强宣传及推广普及。     

Pupil dilatation does affect some aspects of daytime driving performance

AIMS: To examine the effects of pupil dilatation on driving performance and determine whether this was related to changes in standard measures of visual function. METHODS: The driving and vision performance of 16 young, visually normal participants was measured with both normal and dilated pupils. Pupils were dilated with 1% tropicamide. Driving performance was measured under daytime conditions on a closed road circuit that was free of other vehicles and has been used in previous studies of driving performance. Measures included road sign detection and recognition, hazard detection and avoidance, gap perception and negotiation, driving reaction times and time to complete the circuit. Visual performance measures included high contrast visual acuity, Pelli-Robson letter contrast sensitivity, and glare sensitivity. RESULTS: Pupil dilatation significantly (p<0.05) decreased the ability of participants to recognise low contrast hazards and avoid them, decreased their visual acuity and contrast sensitivity and increased glare sensitivity. The decreases in vision performance were not, however, significantly related to the decrement in driving performance. CONCLUSION: Pupil dilatation can impair selected aspects of driving and vision performance and patients should be cautioned about these possible effects.     

Visual–tactile shape perception in the visually restored with artificial vision

Retinal prostheses partially restore vision to late blind patients with retinitis pigmentosa through electrical stimulation of still-viable retinal ganglion cells. We investigated whether the late blind can perform visual–tactile shape matching following the partial restoration of vision via retinal prostheses after decades of blindness.We tested for visual–visual, tactile–tactile, and visual–tactile two-dimensional shape matching with six Argus II retinal prosthesis patients, ten sighted controls, and eight sighted controls with simulated ultra-low vision. In the Argus II patients, the visual–visual shape matching performance was significantly greater than chance. Although the visual–tactile shape matching performance of the Argus II patients was not significantly greater than chance, it was significantly higher with longer duration of prosthesis use. The sighted controls using natural vision and the sighted controls with simulated ultra-low vision both performed the visual–visual and visual–tactile shape matching tasks significantly more accurately than the Argus II patients. The tactile–tactile matching was not significantly different between the Argus II patients and sighted controls with or without simulated ultra-low vision.These results show that experienced retinal prosthesis patients can match shapes across the senses and integrate artificial vision with somatosensation. The correlation of retinal prosthesis patients’ crossmodal shape matching performance with the duration of device use supports the value of experience to crossmodal shape learning. These crossmodal shape matching results in Argus II patients are the first step toward understanding crossmodal perception after artificial visual restoration.     

Training to improve temporal processing of letters benefits reading speed for people with central vision loss

Reading is slow and difficult for many people with central vision loss. A previous study showed that the temporal threshold for letter recognition is a major factor limiting reading speed for people with central vision loss. Here, we asked whether the temporal threshold for letter recognition for people with central vision loss could be improved through training and, if so, whether that would benefit reading. Training consisted of six sessions (3000 trials) of recognizing letter trigrams presented at fixation. Trigrams were initially presented at a baseline temporal threshold that was decreased by 0.1 log step when observers’ letter recognition accuracies reached 80% or higher for four consecutive blocks. Before and after training, we measured observers’ visual acuity, preferred retinal locus for fixation, fixation stability, reading speeds using the rapid serial visual presentation (RSVP) paradigm, the MNREAD Acuity Chart and 100-word passages, the baseline temporal threshold for letter recognition at 80% accuracy, and a visual-span profile. After training, the temporal threshold was decreased by 68%. This improvement was accompanied by a higher RSVP maximum reading speed (but no change in MNREAD and passage reading speeds) and a larger visual span. A mediation analysis showed that the relationship between the temporal threshold and RSVP maximum reading speed was mainly mediated by the information transfer rate (size of visual span/temporal duration). Our results showed that the temporal threshold for letter recognition is amenable to training and can improve RSVP reading speeds, offering a practical means to improve reading speed for people with central vision loss.     

行鱿性及遗传性眼病所致视力残疾患者的视觉康复

目的 分析低视力门诊常见的3种先天及遗传性眼病患者配用助视器后的视功能改善及视觉康复情况。方法 对6-68a的113例（222眼）视力残疾患者,包括视网膜色素变性56例,先天性小眼球小角膜31例,白化病26例,其中盲37眼,低视力178眼,全部采用国产助视器为2.5倍的单筒或双筒望远镜助视器,近用为 6- 32契镜助视器。结果 配用远用助视器后的脱盲率为78.4%脱残率为70.2%,远视力≥0.5共51眼,占23.0%,8只眼为1.0;配用近用助视器后130眼视力≥0.5,占75.1%。结论 远用视功能,使视觉康复,从而提高工作学习能力,提高生活质量。     

不同程度视力残疾儿童应用助视器康复的研究

目的对有残余视力的视力残疾儿童在给予光学和电子助视器康复后进行远、近视力的分析和效果评估,探讨不同程度视力残疾患儿有效的康复手段及其对低视力康复对象范围界定的影响。方法对盲校及低视力门诊共206名4～14周岁（含14岁）视力残疾儿童按视力残疾的程度进行分组,比较应用国产4倍、6倍望远镜前后远视力和应用国产眼镜式助视器、国产简易电子助视器后两种助视器间阅读成功率的差异。远视力康复结果采用秩和检验,近视力康复结果采用卡方检验进行统计学分析。结果视力0．05以下至眼前指数的盲童组和0．3以下至0．05的低视力组应用远用助视器前后远视力差异均有统计学意义（P〈0．05）;视力0．05以下至光感的肓童和低视力儿童分别使用眼镜式近用助视器与简易电子助视器后,两种助视器间阅读成功率的差异均有统计学意义,使用简易电子助视器的阅读成功率均明显高于使用眼镜式近用助视器。结论助视器康复的对象可以从低视力范围扩展到0．01甚至以下的盲童。低视力助视器是视力残疾儿童视觉康复有效和必要的手段,早期视觉康复特别是使用简易电子助视器进行近视力阅读的康复,对视力残疾儿童提高学习认知能力、促进身心健康成长和回归社会具有重要意义。     

助视器对年龄相关性黄斑变性患者视功能恢复和阅读速度的影响

目的:评估助视器对年龄相关性黄斑变性(AMD)患者视功能恢复和阅读速度的影响。方法:对低视力门诊44名AMD患者进行评估。收集并分析使用助视器前和使用助视器时裸眼视力、最佳矫正视力、屈光状态、助视器类型(LVAs)以及阅读速度的相关数据。结果:共44例AMD患者,平均年龄为73±10.8岁,男性36例(82%)。其中,29例(67%)受试者视力较好的眼远视力(DVA)为1.0~1.6 LogMAR,而36例(82%)受试者近视力(NVA)小于3.2 m。使用助视器时平均DVA提高0.67±0.27 LogMAR(P=0.000)。使用LVAs时,42例患者NVA达到1 m甚至更佳,仅有2例(4.5%)没有使用LVAs的患者NVA为1 m。在使用一定时间的助视器后,有阅读能力的患者平均阅读速度从每分钟2.9±4.78字提高到每分钟71.31±29.96字(P<0.001)。15名受试者远距离视觉使用单目望远镜,而戴高倍单目镜片眼镜作为最常用的阅读辅助工具。结论:LVAs对AMD患者的视功能恢复和阅读能力的提高有一定的作用。对于AMD患者而言,接受低视力护理服务是有必要的。     

盲及低视力的先天性白内障患儿术后的视觉康复

目的 :探讨远用和近用助视器在先天性白内障术后视残儿童中的应用效果。方法 :对 31例 (5 4只眼 )患儿分别配戴了单筒或双筒远用望远镜助视器和近用眼镜助视器。结果 :配戴远用助视器后 ,9只盲眼中有 8只眼远视力≥ 0 0 5 ,脱盲率为 88 9%。原 4 5只眼低视力中有 36只眼远视力提高到≥ 0 3,其中 17只眼可达 0 5或以上 ,脱残率为 80 0 %。 2 4例 (45只眼 )选用了近用眼镜助视器 ,15例近视力提高后达≥ 0 5。结论 :助视器在低视力门诊是必备的且有效的 ,可提高患儿视力 ,提高学习生活能力。积极推进视残儿童视觉康复工作是眼科工作者义不容辞的责任。     

Simulated prosthetic visual fixation, saccade, and smooth pursuit

A visual tracking task was administered to 20 subjects afforded simulated prosthetic vision (a phosphene array); a total of 3h data was taken from each subject over the course of 10 visits. The experiment assessed prosthetic visual fixation, saccade and smooth pursuit and the effect of practice. Further, we demonstrated an image analysis technique that assisted fixation and pursuit (but not saccade) accuracy, and required less vigorous movement of the phosphene array in pursuing the target. As measured by mean deviation from the target, fixation and pursuit accuracies were improved by 8.3 and 3.3 min of visual arc, respectively (35.8% and 6.8%), for inter-phosphene spacing of 1.9 degrees . The analysis technique, involving overlapping Gaussian kernels, was an heuristic design; this is the first step of an iterative, experimental approach to devising effective image analysis to be contained in an electronic vision prosthesis. The approach should ultimately afford implanted patients improved prosthetic visual function.