Individual's recollections of their experiences in eye clinics and understanding of their eye condition:results from a survey of visually impaired people in Britain

Background/aims: Network 1000 is a UK-based panel survey of a representative sample of adults with registered visual impairment, with the aim of gathering information about people’s opinions and circumstances. Method: Participants were interviewed (Survey 1, n = 1007: 2005; Survey 2, n = 922: 2006/07) on a range of topics including the nature of their eye condition, details of other health issues, use of low vision aids (LVAs) and their experiences in eye clinics. Results: Eleven percent of individuals did not know the name of their eye condition. Seventy percent of participants reported having long-term health problems or disabilities in addition to visual impairment and 43% reported having hearing difficulties. Seventy one percent reported using LVAs for reading tasks. Participants who had become registered as visually impaired in the previous 8 years (n = 395) were asked questions about non-medical information received in the eye clinic around that time. Reported information received included advice about ‘registration’ (48%), low vision aids (45%) and social care routes (43%); 17% reported receiving no information. While 70% of people were satisfied with the information received, this was lower for those of working age (56%) compared with retirement age (72%). Those who recalled receiving additional non-medical information and advice at the time of registration also recalled their experiences more positively. Conclusions: Whilst caution should be applied to the accuracy of recall of past events, the data provide a valuable insight into the types of information and support that visually impaired people feel they would benefit from in the eye clinic.

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.

Normative data for two visually evoked magnetic components

The practicality or recording normative data for two components of the visually evoked magnetic response (VEMR) (P100M and P2M) using a single channel dc-SQUID second order gradiometer in an unshielded environment was investigated. Latency norms of the P100M and P2M were more variable than the corresponding electrical P100 and P2 visual evoked potentials. Methods of improving the normative data for clinical use were discussed.

Further studies of the visually evoked subcortical potential in man

The Visually Evoked Subcortical Potential, a far-field signal, was originally defined to flash stimulation as a triphasic positive-negative-positive complex with mean latencies of P21 N26.2 P33.6 (Harding and Rubinstein 1980). Inconsistent with its subcortical source however, the signal was found to be tightly localised to the mastoid. This thesis re-examines the earlier protocols using flash stimulation and with auditory masking establishes by topographic studies that the VESP has a widespread scalp distribution, consistent with a far-field source of the signal, and is not a volume-conducted electroretinogram (ERG). Furthermore, mastoid localisation indicates auditory contamination from the click, on discharge of the photostimulator. The use of flash stimulation could not precisely identify the origin of the response. Possible sources of the VESP are the lateral geniculate body (LGB) and the superior colliculus. The LGB received 80% of the nerve fibres from the retina, and responds to high contrast achromatic stimulation in the form of drifting gratings of high spatial frequencies. At low spatial frequencies, it is more sensitive to colour. The superior colliculus is insensitive to colour and suppressed by contrast and responds to transitory rapid movements, and receives about 20% of the optic nerve fibres. A pattern VESP was obtained to black and white checks as a P23.5 N29.2 P34 complex in 93% of normal subjects at an optimal check size of 12'. It was also present as a P23.0 N28.29 P32.23 complex to red and green luminance balanced checks at 2o check size in 73% of subjects. These results were not volume-conducted pattern electroretinogram responses. These findings are consistent with the spatial frequency properties of the lateral geniculate body which is the considered source of the signal. With further work, the VESP may supplement electrodiagnosis of post-chiasmal lesions.

The visually evoked magnetic response (VEMR) to a pattern onset/offset stimulus

This study characterizes the visually evoked magnetic response (VEMR) to pattern onset/offset stimuli, using a single channel BTi magnetometer. The influence of stimulus parameters and recording protocols on the VEMR is studied with inferences drawn about the nature of cortical processing, its origins and optimal recording strategies. Fundamental characteristics are examined, such as the behaviour of successive averaged and unaveraged responses; the effects of environmental shielding; averaging; inter- and intrasubject variability and equipment specificity. The effects of varying check size, field size, contrast and refractive error on latency, amplitude and topographic distribution are also presented. Latency and amplitude trends are consistent with previous VEP findings and known anatomical properties of the visual system. Topographic results are consistent with the activity of sources organised according to the cruciform model of striate cortex. A striate origin for the VEMR is also suggested by the results to quarter, octant and annulus field stimuli. Similarities in the behaviour and origins of the sources contributing to the CIIm and CIIIm onset peaks are presented for a number of stimulus conditions. This would be consistent with differing processing event in the same, or similar neuronal populations. Focal field stimuli produce less predictable responses than full or half fields, attributable to a reduced signal to noise ratio and an increased sensitivity to variations in cortical morphology. Problems with waveform peak identification are encountered for full field stimuli that can only be resolved by the careful choice of stimulus parameters, comparisons with half field responses or with reference to the topographic distribution of each waveform peak. An anatomical study of occipital lobe morphology revealed large inter- and intrasubject variation in calcarine fissure shape and striate cortex distribution. An appreciation of such variability is important for VEMR interpretation, due to the technique's sensitivity to source depth and orientation, and it is used to explain the experimental results obtained.

Understanding the IT-related attitudes and needs of persons with age-related macular degeneration : a case study

In the UK, 20 per cent of people aged 75 years and over are living with sight loss; this percentage is expected to increase as the population ages (RNIB, 2011). Age-Related Macular Degeneration (AMD) is the UK’s leading cause of severe visual impairment amongst the elderly. It accounts for 16,000 blind/partial sight registrations per year and is the leading cause of blindness among people aged 55 years and older in western countries (Bressler, 2004). Our ultimate goal is to develop an assistive mobile application to support accurate and convenient diet data collection on which basis to then provide customised dietary advice and recommendations in order to help support individuals with AMD to mitigate their ongoing risk and retard the progression of the disease. In this paper, we focus on our knowledge elicitation activities conducted to help us achieve a deep and relevant understanding of our target user group. We report on qualitative findings from focus groups and observational studies with persons with AMD and interviews with domain experts which enable us to fully appreciate the impact that technology may have on our intended users as well as to inform the design and structure of our proposed mobile assistive application.

Evaluation of Melbourne Edge Test contrast sensitivity measures in the visually impaired

Aim: Contrast sensitivity (CS) provides important information on visual function. This study aimed to assess differences in clinical expediency of the CS increment-matched new back-lit and original paper versions of the Melbourne Edge Test (MET) to determine the CS of the visually impaired. Methods: The back-lit and paper MET were administered to 75 visually impaired subjects (28-97 years). Two versions of the back-lit MET acetates were used to match the CS increments with the paper-based MET. Measures of CS were repeated after 30 min and again in the presence of a focal light source directed onto the MET. Visual acuity was measured with a Bailey-Lovie chart and subjects rated how much difficulty they had with face and vehicle recognition. Results: The back-lit MET gave a significantly higher CS than the paper-based version (14.2 ± 4.1 dB vs 11.3 ± 4.3 dB, p < 0.001). A significantly higher reading resulted with repetition of the paper-based MET (by 1.0 ± 1.7 dB, p < 0.001), but this was not evident with the back-lit MET (by 0.1 ± 1.4 dB, p = 0.53). The MET readings were increased by a focal light source, in both the back-lit (by 0.3 ± 0.81, p < 0.01) and paper-based (1.2 ± 1.7, p < 0.001) versions. CS as measured by the back-lit and paper-based versions of the MET was significantly correlated to patients' perceived ability to recognise faces (r = 0.71, r = 0.85 respectively; p < 0.001) and vehicles (r = 0.67, r = 0.82 respectively; p < 0.001), and with distance visual acuity (both r =-0.64; p < 0.001). Conclusions: The CS increment-matched back-lit MET gives higher CS values than the old paper-based test by approximately 3 dB and is more repeatable and less affected by external light sources. Clinically, the MET score provides information on patient difficulties with visual tasks, such as recognising faces. © 2005 The College of Optometrists.

Image enhancement of real-time television to benefit the visually impaired

Purpose: To examine the use of real-time, generic edge detection, image processing techniques to enhance the television viewing of the visually impaired. Design: Prospective, clinical experimental study. Method: One hundred and two sequential visually impaired (average age 73.8 ± 14.8 years; 59% female) in a single center optimized a dynamic television image with respect to edge detection filter (Prewitt, Sobel, or the two combined), color (red, green, blue, or white), and intensity (one to 15 times) of the overlaid edges. They then rated the original television footage compared with a black-and-white image displaying the edges detected and the original television image with the detected edges overlaid in the chosen color and at the intensity selected. Footage of news, an advertisement, and the end of program credits were subjectively assessed in a random order. Results: A Prewitt filter was preferred (44%) compared with the Sobel filter (27%) or a combination of the two (28%). Green and white were equally popular for displaying the detected edges (32%), with blue (22%) and red (14%) less so. The average preferred edge intensity was 3.5 ± 1.7 times. The image-enhanced television was significantly preferred to the original (P < .001), which in turn was preferred to viewing the detected edges alone (P < .001) for each of the footage clips. Preference was not dependent on the condition causing visual impairment. Seventy percent were definitely willing to buy a set-top box that could achieve these effects for a reasonable price. Conclusions: Simple generic edge detection image enhancement options can be performed on television in real-time and significantly enhance the viewing of the visually impaired. © 2007 Elsevier Inc. All rights reserved.

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 acuity 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.

An enhanced functional ability questionnaire (faVIQ) to measure the impact of rehabilitation services on the visually impaired

AIM To develop a short, enhanced functional ability Quality of Vision (faVIQ) instrument based on previous questionnaires employing comprehensive modern statistical techniques to ensure the use of an appropriate response scale, items and scoring of the visual related difficulties experienced by patients with visual impairment. METHODS Items in current quality-of-life questionnaires for the visually impaired were refined by a multi-professional group and visually impaired focus groups. The resulting 76 items were completed by 293 visually impaired patients with stable vision on two occasions separated by a month. The faVIQ scores of 75 patients with no ocular pathology were compared to 75 age and gender matched patients with visual im pairm ent. RESULTS Rasch analysis reduced the faVIQ items to 27. Correlation to standard visual metrics was moderate (r=0.32-0.46) and to the NEI-VFQ was 0.48. The faVIQ was able to clearly discriminate between age and gender matched populations with no ocular pathology and visual impairment with an index of 0.983 and 95% sensitivity and 95% specificity using a cut off of 29. CONCLUSION The faVIQ allows sensitive assessm ent of quality-of-life in the visually im paired and should support studies which evaluate the effectiveness of low vision rehabilitation services. © Copyright International Journal of Ophthalmology Press.

A review of current knowledge on Electronic Vision Enhancement Systems for the visually impaired

Magnification can be provided to assist those with visual impairment to make the best use of remaining vision. Electronic transverse magnification of an object was first conceived for use in low vision in the late 1950s, but has developed slowly and is not extensively prescribed because of its relatively high cost and lack of portability. Electronic devices providing transverse magnification have been termed closed-circuit televisions (CCTVs) because of the direct cable link between the camera imaging system and monitor viewing system, but this description generally refers to surveillance devices and does not indicate the provision of features such as magnification and contrast enhancement. Therefore, the term Electronic Vision Enhancement Systems (EVES) is proposed to better distinguish and describe such devices. This paper reviews current knowledge on EVES for the visually impaired in terms of: classification; hardware and software (development of technology, magnification and field-of-view, contrast and image enhancement); user aspects (users and usage, reading speed and duration, and training); and potential future development of EVES. © 2003 The College of Optometrists.

Benefits of electronic vision enhancement systems (EVES) for the visually impaired

PURPOSE: To examine whether objective performance of near tasks is improved with various electronic vision enhancement systems (EVES) compared with the subject's own optical magnifier. DESIGN: Experimental study, randomized, within-patient design. METHODS: This was a prospective study, conducted in a hospital ophthalmology low-vision clinic. The patient population comprised 70 sequential visually impaired subjects. The magnifying devices examined were: patient's optimum optical magnifier; magnification and field-of-view matched mouse EVES with monitor or head-mounted display (HMD) viewing; and stand EVES with monitor viewing. The tasks performed were: reading speed and acuity; time taken to track from one column of print to the next; follow a route map, and locate a specific feature; and identification of specific information from a medicine label. RESULTS: Mouse EVES with HMD viewing caused lower reading speeds than stand EVES with monitor viewing (F = 38.7, P < .001). Reading with the optical magnifier was slower than with the mouse or stand EVES with monitor viewing at smaller print sizes (P < .05). The column location task was faster with the optical magnifier than with any of the EVES (F = 10.3, P < .001). The map tracking and medicine label identification task was slower with the mouse EVES with HMD viewing than with the other magnifiers (P < .01). Previous EVES experience had no effect on task performance (P > .05), but subjects with previous optical magnifier experience were significantly slower at performing the medicine label identification task with all of the EVES (P < .05). CONCLUSIONS: Although EVES provide objective benefits to the visually impaired in reading speed and acuity, together with some specific near tasks, some can be performed just as fast using optical magnification. © 2003 by Elsevier Inc. All rights reserved.

Mobile assistive technologies for the visually impaired

There are around 285 million visually impaired people worldwide, and around 370,000 people are registered as blind or partially sighted in the UK. Ongoing advances in information technology (IT) are increasing the scope for IT-based mobile assistive technologies to facilitate the independence, safety, and improved quality of life of the visually impaired. Research is being directed at making mobile phones and other handheld devices accessible via our haptic (touch) and audio sensory channels. We review research and innovation within the field of mobile assistive technology for the visually impaired and, in so doing, highlight the need for successful collaboration between clinical expertise, computer science, and domain users to realize fully the potential benefits of such technologies. We initially reflect on research that has been conducted to make mobile phones more accessible to people with vision loss. We then discuss innovative assistive applications designed for the visually impaired that are either delivered via mainstream devices and can be used while in motion (e.g., mobile phones) or are embedded within an environment that may be in motion (e.g., public transport) or within which the user may be in motion (e.g., smart homes). © 2013 Elsevier Inc.

Visually induced syncope:a nonepileptic manifestation of visual sensitivity?

Visual sensitivity, defined as the “susceptibility toward experiencing seizures, which are triggered by the physical characteristics of visual stimuli and not by their perceptual properties,”1 can manifest in the context of various forms of generalized or focal, idiopathic or symptomatic epilepsies.2 We report a patient with no family or personal history of epilepsy who presented episodes of loss of consciousness exclusively triggered by visual stimuli unrelated to their emotional content, in which we have documented EEG-EKG characteristics suggestive of a neurally mediated syncope.