The Toronto experience with the Argus II retinal prosthesis: new technology,new hope for patients

Surgical restoration of vision with retinal prostheses is a new and developing technology currently available in a select group of countries, Canada among them. The Argus II retinal prosthesis is the first commercially available device for restoration of vision in patients with Retinitis Pigmentosa or with similar retinal pathology who still have minimal residual native vision. The surgery is complex and requires training however it is within the abilities of any experienced retina surgeon. Surgical experience builds up with each case and in our patients length of surgery constantly went down. Complications occurred however we experienced no catastrophic events. Most notable is that in our implanted cases the Argus II technology proved to be beneficial to most patients. In order to obtain optimal results with this surgical intervention it is absolutely required that the surgical work is complemented simultaneously with the work of a specialized rehabilitation team. A review of the technology, of our experience, comments and concerns is presented in this paper.     

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.     

Safety,effectiveness,and cost-effectiveness of ArgusⅡin patients with retinitis pigmentosa:a systematic review

AIM:To assess the effectiveness,safety,and costeffectiveness of the Argus II in treatment of the retinitis pigmentosa(RP)patients.METHODS:The Pro Quest,Web of Science,EMBASE,MEDLINE(via Pub Med)were searched using combinations of the keywords of Argus,safety,effectiveness,bionic eye,retinal prosthesis,and RP through March 2018.The retrieved records were screened and then assessed for eligibility.RESULTS:Totally 926 records were retrieved from the searched databases and finally 12 studies included.The RP patients showed improvements in visual function after receiving the prosthesis,compared to the time before the prosthesis or the time it was off.This was measured by square localization,direction of motion,and grating visual acuity tests.No major adverse effect was reported for the Argus II prosthesis itself and/or the surgery to implement it,but the most frequently reported items were hypotony,and conjunctival dehiscence.The incremental cost-effectiveness ratio(ICER)was calculated to be€14603 per qualityadjusted life year(QALY)in UK and$207616 per QALY in Canada.CONCLUSION:The available evidence shows that the Argus II prosthesis in RP patients is effective in improvement of their visual function.Some minor adverse effects are reported for the prosthesis.The cost-effectiveness studies show that the technology is cost-effective only at high levels of willingness-to-pay.     

Use of the Argus II Retinal Prosthesis to Improve Visual Guidance of Fine Hand Movements

Purpose. We studied the capabilities of the Argus II retinal prosthesis for guiding fine hand movement, and demonstrated and quantified guidance improvement when using the device over when not using the device for progressively less predictable trajectories. Methods. A total of 21 patients with retinitis pigmentosa (RP), remaining vision no more than bare light perception, and an implanted Argus II epiretinal prostheses used a touchscreen to trace white paths on black backgrounds. Sets of paths were divided into three categories: right-angle/single-turn, mixed-angle/single-turn, and mixed-angle/two-turn. Subjects trained on paths by using prosthetic vision and auditory feedback, and then were tested without auditory feedback, with and without prosthetic vision. Custom software recorded position and timing information for any contact that subjects made with the screen. The area between the correct path and the trace, and the elapsed time to trace a path were used to evaluate subject performance. Results. For right-angle/single-turn sets, average tracing error was reduced by 63% and tracing time increased by 156% when using the prosthesis, relative to residual vision. With mixed-angle/single-turn sets, error was reduced by 53% and time to complete tracing increased by 184%. Prosthesis use decreased error by 38% and increased tracing time by 252% for paths that incorporated two turns. Conclusions. Use of an epiretinal visual prosthesis can allow RP patients with no more than bare light perception to guide fine hand movement visually. Further, prosthetic input tends to make subjects slower when performing tracing tasks, presumably reflecting greater effort. (ClinicalTrials.gov number, NCT00407602.).     

The Argus™ II retinal prosthesis: Factors affecting patient selection for implantation

The Argus II epiretinal prosthesis has been developed to provide partial restoration of vision to subjects blinded from outer retinal degenerative disease. To date, the device has been implanted in multiple subjects with profound retinitis pigmentosa as part of a worldwide clinical feasibility study (clinicaltrials.gov ID: NCT00407602). The Argus II is intended to provide partial restoration of functional vision. Most subjects showed an improvement in tasks assessing orientation & mobility, spatial-motor localization, and ability of discerning the direction of motion of moving stimuli. Roughly one third of subjects experienced measurable improvement in visual acuity with the implant. Some subjects identified words with high accuracy, a result that has also been reported by the leading subretinal implant group. Perceptual threshold was correlated with electrode-retina distance, electrode-fovea distance, and light sensitivity, either as single variables or in bivariate linear regression. Taken together these three variables may be used to inform patient selection and develop algorithms for the fitting of higher-electrode count systems. Visual acuity for future generations of the Argus implant may not hit theoretical limitations until arrays hold an excess of several hundreds of electrodes. Nevertheless, preliminary safety and efficacy data are supportive of the development of higher-resolution systems that target macular placement from implant design and surgical perspectives.     

微视野生物反馈训练在黄斑疾病低视力康复中的研究进展

临床工作中,很多黄斑疾病如年龄相关性黄斑变性(ARMD)、Stargardt病在晚期因新生血管纤维瘢痕化或光感受器、视网膜色素上皮细胞受损形成中心暗点,从而出现视力下降、固视不稳定甚至旁中心注视,给患者的生活工作及心理带来很大困扰。长期以来,我们对该类患者的康复治疗手段有限,但近年来有不少文献指出,基于微视野计的生物反馈训练有望通过实现大脑皮层可塑性增强神经感觉适应能力,较大程度的利用残余视网膜功能来帮助那些伴中心暗点的低视力人群巩固或建立稳定的中心或旁中心注视,进而提高视力、阅读速度等视功能。为增进对该康复治疗手段的认识,本文将主要从微视野生物反馈训练(microperimetric biofeedback training, MBFT)机制及方案、优选视网膜位点的选择、在黄斑疾病中的临床应用及前景展开概述。     

低视力门诊患者的特征及视觉康复需求

目的探讨低视力患者的视觉康复需求以及拒绝视觉康复的原因,为推广低视力视觉康复模式提供参考。方法回顾性病例研究。收集2013年7月至2014年7月来温州医科大学附属眼视光医院就诊的低视力患者361例,年龄（44.2±23.0）岁,男193例,女168例,主要来自院内转诊（68.5%）。对视力损伤的病因、患者对视觉康复的需求、视觉康复的有效性进行统计和分析。结果20岁以下低视力患者的病因主要是先天性白内障（30.7%）和眼球震颤（28.0%）;20岁及以上主要是病理性近视（25.5%）和其他视网膜疾病（25.2%）。88.2%的患者有视觉康复需求,远视力康复的首要、次要需求是娱乐休闲活动;近视力康复的首要需求是娱乐休闲活动,次要需求是阅读。患者助视器接受率为59.4%,93.6%患者拒绝的原因是仍希望能通过手术、药物等治疗方式改善视功能。结论娱乐休闲活动是温州医科大学附属眼视光医院低视力门诊患者视觉康复的首要需求,制定融合娱乐休闲活动的低视力康复策略可能是一种有效的康复方法。     

Strategy for developing an evidence-based transdisciplinary vision rehabilitation team approach to treating vision impairment.

BACKGROUND: Many individuals with vision impairment experience significant loss of the ability to perform daily living activities, which often results in a further decline and loss of quality of life. Appropriate rehabilitation of the population with vision impairment has the potential to both improve individual abilities for health and personal management as well as maximize utilization of available health care resources. METHODS: The case for an evidence-based model for the vision rehabilitation health care team as a medical rehabilitation program is presented. The recommended strategy has 3 main components: development of a consensus team clinical practice guideline leading to a future evidence-based team guideline for vision rehabilitation; evaluation and measurement of the knowledge, attitudes, and practices of the involved vision rehabilitation professionals before and after implementation of the new paradigm; and measurement of outcomes that estimate the effects of the proposed paradigm on patient care by measuring both the improvement in visual ability of the patient and the economic impact of the model on optometric practice. CONCLUSIONS: Development of a state-of-the-art evidence-based transdisciplinary team model guideline will facilitate improvement in the quality of life of individuals with diseases that result in chronic vision impairment.     

Rehabilitation of reading skills in patients with age-related macular degeneration

Reading is the most frequent clinical complaint and the primary goal for patients with macular degeneration seeking vision rehabilitation. The current prevalent methods for reading skills training across the globe are still magnification and basic scotoma awareness training. More recent studies showed that specific eccentric training, comprehension ability training, and specific oculomotor training are all beneficial to reading skills rehabilitation. In clinical practice, ophthalmologists should strive to implement reading skills methods that include assessment of cognitive skills, optimal eyewear, optimal reading material, PRL assessment, training of better oculomotor control, and efficient perceptual training.     

视觉假体及神经微电极的研究进展

借助视觉假体有望使某些难治的视网膜病变，如年龄相关性黄斑变性（AMD）和原发性视网膜色素变性（RP）患者恢复部分视力。神经微电极是视觉假体系统中的重要部件，具有对神经进行电刺激并记录神经信号的重要作用。随着微电子技术、医疗技术、生物技术及材料加工技术的不断发展，许多新型材料和微加工工艺被逐渐应用于神经微电极的研制，从而为视觉假体提供更好的脑-机接口组件。对近年来视觉假体和神经微电极的研究现状和发展趋势进行综述，以更好地理解视觉恢复的机制，不断优化视觉假体系统的功能。     

视神经假体的研究进展

人工视觉的研究是指用人工的方法在视路的不同部位植入不同的视觉假体,以帮助失明患者获得部分有用视力.其中视神经假体有其独特的优越性,尤其对视网膜不复存在的患者提供了重见光明的可能.视神经假体以视神经的解剖特点为生理学基础,利用电流替代光使患者产生视觉感受的原理,通过外部装置获取图像后将其处理成可以被大脑识别的电信号,并向内部装置传送,与人体神经系统进行通信.视神经假体突破了视网膜假体植入方法的局限,可直接刺激视神经,适合于视网膜的内、外层和神经节细胞层均受到损伤的患者,但同时也存在一些局限性.     

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.     

Okuläre elektrische Stimulation

Background

Electrical stimulation has a long history in ophthalmology. Subthreshold electrical stimulation can have beneficial therapeutic effects on hereditary degenerative retinal diseases. Suprathreshold stimulation is able to elicit visual perceptions and, if multielectrode fields are arranged as an array, usable pictures can be perceived by blind patients.

Objectives

This is a review article on the current situation and studies on therapeutic transcorneal electrical stimulation. Moreover, the challenges, surgical concepts and visual results of active retinal implants are discussed.

Material and methods

This article gives an overview on transcorneal electrical stimulation and active retinal implants based on published results, with special emphasis on the clinical application.

Results

The results of initial controlled studies on therapeutic transcorneal electrical stimulation in hereditary retinal diseases were very promising. The largest controlled study so far in patients with retinitis pigmentosa (RP) has yielded many positive trends and some significant improvements in electrophysiological data. Currently, two retinal implants have regulatory approval, the Argus II retinal prosthesis system® (SecondSight®) and the Alpha-IMS© (Retina Implant AG). Both systems can be used to improve visual perception and under test conditions can achieve visual acuities of 0.02 and 0.04, respectively.

Conclusion

In-depth analyses and follow-up studies in larger patient groups are currently planned to definitively clarify the potential of therapeutic transcorneal electrical stimulation in RP patients. The challenges of currently available active retinal implants are the technical biostability and the limited spatial resolution.

     

The provision of ophthalmic services for a rehabilitation day care centre population with multiple physical handicaps

The provision of the wide variety of support services necessary for patients with multiple handicaps is often poorly coordinated. In this study a group of 108 adults, aged from 19 to 90 years, who suffered from multiple physical handicaps and attended a rehabilitation day care centre, had their visual functions and requirements assessed by a multidisciplinary team. The programme consisted of five stages. Each patient was initially screened and subsequently referred for more detailed optometric, ophthalmological, low vision or rehabilitation assessments, where appropriate. Results indicated that many of the patients had not been receiving regular ocular assessments and would benefit from the provision of an optical appliance or ophthalmological treatment. The survey provided staff at the rehabilitation centre with information on the visual status of individual patients and enhanced general eye-care awareness.     

人工视网膜的研究现状

对于年龄相关性黄斑变性和视网膜色素变性等疾病导致的神经性盲,目前尚无有效治疗手段.人工视网膜是所有视觉假体中研究最广泛、最成熟的一种,通过医学、工程等多领域专家的共同推进,人工视网膜可能会发展成为神经性盲的临床修复技术     

SOLITARY SILENT VENOUS PAPILLARY LOOPS AND OCULAR HYPERTENSION

A series of 24 eyes in 23 patients is described showing solitary silent venous papillary loops. These loops are usually associated with a considerable degree of ocular hypertension, presenting when this hypertension is being investigated. They are silent, usually with no previous ocular history, single with a large diameter, affecting veins at the optic disc and not extending into the vitreous. The optic disc is cupped, but usually not more than 0.6 disc diameter, there is good central vision and either a full visual field or only early field loss. Fluorescein angiography shows the loops to be competent with no evidence of any other retinal vascular abnormality. Rarely loss of central vision may occur due to progression to advanced glaucoma. The condition is distinct from prepapillary vascular arterial papillary loops, neovascularization at the optic disc and optociliary shunt vessels. It is also distinct from the venous collateral vessels which develop at the optic disc after acute central or branch retinal vein occlusion. These collaterals are usually multiple, the accompanying ocular hypertension is of lesser degree, cupping of the disc and field loss are usually much more advanced and, while visual acuity may be normal, it is often grossly reduced. On fluorescein angiography all these cases of venous collaterals after retinal vein occlusion showed evidence of other retinal vascular dysfunction. Solitary silent venous papillary loops appear to develop from venules on the optic disc as a bypass to a low grade venous occlusion which is seldom clinically manifest. They form a distinct entity with a good prognosis if the accompanying ocular hypertension is carefully controlled.     

Repair of retinitis-related retinal detachments with silicone oil in patients with acquired immunodeficiency syndrome.

To provide prompt visual rehabilitation and to reduce the need for repeated operations, we performed vitrectomy with silicone oil tamponade in 16 consecutive eyes with retinal detachments related to cytomegalovirus retinitis and acute retinal necrosis in 13 patients with acquired immunodeficiency syndrome. In all 16 eyes (100%), retinas were reattached with one operation. Preservation of ambulatory vision was achieved in six of eight eyes (75%; mean follow-up, 14.6 weeks). No patient with hand motion visual acuity or worse preoperatively recovered ambulatory vision. Visual acuity recovery was limited by optic nerve disease in five eyes (31%). Silicone oil-related side effects did not adversely affect visual outcome in any eye. Six patients (46%) have since died (mean, 4.4 months postoperatively). These data indicated that successful surgical repair of these detachments can be consistently achieved with this approach. The prognosis for ambulatory vision is strongly related to preoperative visual acuity.     

Simulation of artificial vision: IV. Visual information required to achieve simple pointing and manipulation tasks

Retinal prostheses attempt to restore some amount of vision to totally blind patients. Vision evoked this way will be however severely constrained because of several factors (e.g., size of the implanted device, number of stimulating contacts, etc.). We used simulations of artificial vision to study how such restrictions of the amount of visual information provided would affect performance on simple pointing and manipulation tasks. Five normal subjects participated in the study. Two tasks were used: pointing on random targets (LEDs task) and arranging wooden chips according to a given model (CHIPs task). Both tasks had to be completed while the amount of visual information was limited by reducing the resolution (number of pixels) and modifying the size of the effective field of view. All images were projected on a 10 degrees x 7 degrees viewing area, stabilised at a given position on the retina. In central vision, the time required to accomplish the tasks remained systematically slower than with normal vision. Accuracy was close to normal at high image resolutions and decreased at 500 pixels or below, depending on the field of view used. Subjects adapted quite rapidly (in less than 15 sessions) to performing both tasks in eccentric vision (15 degrees in the lower visual field), achieving after adaptation performances close to those observed in central vision. These results demonstrate that, if vision is restricted to a small visual area stabilised on the retina (as would be the case in a retinal prosthesis), the perception of several hundreds of retinotopically arranged phosphenes is still needed to restore accurate but slow performance on pointing and manipulation tasks. Considering that present prototypes afford less than 100 stimulation contacts and that our simulations represent the most favourable visual input conditions that the user might experience, further development is required to achieve optimal rehabilitation prospects.     

五所特殊教育学校视障学生视觉损伤及康复情况

目的：分析国内5所特殊教育学校视障学生的视觉损伤及康复现状,了解这些学校视障学生的眼健康状况,探讨影响视障学生视觉康复相关因素及今后工作重点。方法：横断面调查研究。采用WHO 盲及低视力眼检查记录表,对5所特殊教育学校视障班学生进行病史采集、视力检查、裂隙灯显微镜检查、医学验光及助视器验配。采用2003年世界卫生组织制定的视觉损伤分级诊断标准。采用 Wilcoxon符号秩和检验对数据进行分析。结果：共筛查视障学生330例（660眼）,其中可避免盲及低视力有170例（51.5%）,难避免盲及低视力有115例（34.8%）,因筛查条件受限不能确定45例（13.7%）。 324例视障学生中（除去6例不配合视力检查）,93例（28.7%）学生屈光矫正后视力有所提高,双眼中较好眼的最佳矫正视力（LogMAR）由1.44升至1.19,屈光矫正前后差异有统计学意义（Z=-3.523, P<0.001）。17例（5.2%）屈光矫正后视觉损伤等级有所下降。122例（37.7%）可验配使用中远助视器提高远视力,128例（39.5%）可验配使用近用助视器提高近视力。在1级、2级及3级视觉损伤的视障学生中,远用助视器验配比例分别达到83.7%、83.3%、65.3%,脱盲率达到17.8%,脱残率达到72.2%;近用助视器验配比例分别达到77.6%、81.3%、77.6%,脱盲率达到22.8%,脱残率达到 81.4%。结论：部分特殊教育学校视障学生尚缺乏系统的眼健康筛查及视觉康复服务,部分视障学生通过屈光矫正及助视器的使用即可有效脱盲、脱残。在特殊教育学校中普及眼健康筛查及助视器的康复使用,可作为今后开展视障学生康复工作的重点内容之一。