Distance telescopes: a survey of user success

Impacts of impaired face perception on social interactions and quality of life in age-related macular degeneration: A qualitative study and new community resources

Aims

Previous studies and community information about everyday difficulties in age-related macular degeneration (AMD) have focussed on domains such as reading and driving. Here, we provide the first in-depth examination of how impaired face perception impacts social interactions and quality of life in AMD. We also develop a Faces and Social Life in AMD brochure and information sheet, plus accompanying conversation starter, aimed at AMD patients and those who interact with them (family, friends, nursing home staff).

Method

Semi-structured face-to-face interviews were conducted with 21 AMD patients covering the full range from mild vision loss to legally blind. Thematic analysis was used to explore the range of patient experiences.

Results

Patients reported faces appeared blurred and/or distorted. They described recurrent failures to recognise others' identity, facial expressions and emotional states, plus failures of alternative non-face strategies (e.g., hairstyle, voice). They reported failures to follow social nuances (e.g., to pick up that someone was joking), and feelings of missing out ('I can't join in'). Concern about offending others (e.g., by unintentionally ignoring them) was common, as were concerns of appearing fraudulent ('Other people don't understand'). Many reported social disengagement. Many reported specifically face-perception-related reductions in social life, confidence, and quality of life. All effects were observed even with only mild vision loss. Patients endorsed the value of our Faces and Social Life in AMD Information Sheet, developed from the interview results, and supported future technological assistance (digital image enhancement).

Conclusion

Poor face perception in AMD is an important domain contributing to impaired social interactions and quality of life. This domain should be directly assessed in quantitative quality of life measures, and in resources designed to improve community understanding. The identity-related social difficulties mirror those in prosopagnosia, of cortical rather than retinal origin, implying findings may generalise to all low-vision disorders.

Television, computer and portable display device use by people with central vision impairment

PURPOSE

To survey the viewing experience (e.g. hours watched, difficulty) and viewing metrics (e.g. distance viewed, display size) for television (TV), computers and portable visual display devices for normally-sighted (NS) and visually impaired participants. This information may guide visual rehabilitation.

METHODS

Survey was administered either in person or in a telephone interview on 223 participants of whom 104 had low vision (LV, worse than 6/18, age 22-90 years, 54 males), and 94 were NS (visual acuity 6/9 or better, age 20-86 years, 50 males). Depending on their situation, NS participants answered up to 38 questions and LV participants answered up to a further 10 questions.

RESULTS

Many LV participants reported at least 'some' difficulty watching TV (71/103), reported at least 'often' having difficulty with computer displays (40/76) and extreme difficulty watching videos on handheld devices (11/16). The average daily TV viewing was slightly, but not significantly, higher for the LV participants (3.6 h) than the NS (3.0 h). Only 18% of LV participants used visual aids (all optical) to watch TV. Most LV participants obtained effective magnification from a reduced viewing distance for both TV and computer display. Younger LV participants also used a larger display when compared to older LV participants to obtain increased magnification. About half of the TV viewing time occurred in the absence of a companion for both the LV and the NS participants. The mean number of TVs at home reported by LV participants (2.2) was slightly but not significantly (p = 0.09) higher than NS participants (2.0). LV participants were equally likely to have a computer but were significantly (p = 0.004) less likely to access the internet (73/104) compared to NS participants (82/94). Most LV participants expressed an interest in image enhancing technology for TV viewing (67/104) and for computer use (50/74), if they used a computer.

CONCLUSIONS

In this study, both NS and LV participants had comparable video viewing habits. Most LV participants in our sample reported difficulty watching TV, and indicated an interest in assistive technology, such as image enhancement. As our participants reported that at least half their video viewing hours are spent alone and that there is usually more than one TV per household, this suggests that there are opportunities to use image enhancement on the TVs of LV viewers without interfering with the viewing experience of NS viewers.

Clinical and laboratory evaluation of peripheral prism glasses for hemianopia

PURPOSE

Homonymous hemianopia (the loss of vision on the same side in each eye) impairs the ability to navigate and walk safely. We evaluated peripheral prism glasses as a low vision optical device for hemianopia in an extended wearing trial.

METHODS

Twenty-three patients with complete hemianopia (13 right) with neither visual neglect nor cognitive deficit enrolled in the 5-visit study. To expand the horizontal visual field, patients' spectacles were fitted with both upper and lower Press-On Fresnel prism segments (each 40 prism diopters) across the upper and lower portions of the lens on the hemianopic ("blind") side. Patients were asked to wear these spectacles as much as possible for the duration of the study, which averaged 9 (range: 5 to 13) weeks. Clinical success (continued wear, indicating perceived overall benefit), visual field expansion, perceived direction, and perceived quality of life were measured.

RESULTS

Clinical success: 14 of 21 (67%) patients chose to continue to wear the peripheral prism glasses at the end of the study (two patients did not complete the study for non-vision reasons). At long-term follow-up (8 to 51 months), 5 of 12 (42%) patients reported still wearing the device. Visual field expansion: expansion of about 22 degrees in both the upper and lower quadrants was demonstrated for all patients (binocular perimetry, Goldmann V4e). Perceived direction: two patients demonstrated a transient adaptation to the change in visual direction produced by the peripheral prism glasses. Quality of life: at study end, reduced difficulty noticing obstacles on the hemianopic side was reported.

CONCLUSIONS

The peripheral prism glasses provided reported benefits (usually in obstacle avoidance) to 2/3 of the patients completing the study, a very good success rate for a vision rehabilitation device. Possible reasons for long-term discontinuation and limited adaptation of perceived direction are discussed.

Assessment and management of children with visual impairment

PURPOSE

The aim of this work was to evaluate the role of low vision aids in improving visual performance and response in children with low vision.

STUDY DESIGN

Prospective clinical case series.

MATERIALS AND METHODS

This study was conducted on 50 patients that met the international criteria for a diagnosis of low vision. Their ages ranged from 5 to 15 years. Assessment of low vision included distance and near visual acuity assessment, color vision and contrast sensitivity function. Low vision aids were prescribed based on initial evaluation and the patient's visual needs. Patients were followed up for 1 year using the tests done at the initial examination and a visual function assessment questionnaire.

RESULTS

The duration of visual impairment ranged from 1 to 10 years, with mean duration +/- SD being 4.6+/- 2.3299. The near visual acuities ranged from A10 to A20, with mean near acuity +/- SD being A13.632 +/- 3.17171. Far visual acuities ranged from 6/60 (0.06) to 6/24 (0.25), with mean far visual acuity +/- SD being 0.122 +/- 0.1191. All patients had impaired contrast sensitivity function as tested using the vision contrast testing system (VCTS) chart for all spatial frequencies. Distance and near vision aids were prescribed according to the visual acuity and the visual needs of every patient. All patients in the age group 5-7 years could be integrated in mainstream schools. The remaining patients that were already integrated in schools demonstrated greater independency regarding reading books and copying from blackboards.

CONCLUSION

Our study confirmed that low vision aids could play an effective role in minimizing the impact of low vision and improving the visual performance of children with low vision, leading to maximizing their social and educational integration.

Low vision rehabilitation for a target-shooting marksman with visual field loss and diplopia

BACKGROUND

In the United States in 2006, there were 17.8 million hunters and 17.1 million target shooters. When these sportsmen suffer significant visual loss, it can have a devastating effect on their participation in the shooting sports. According to the National Rifle Association, there are no reliable data sources on the number of target shooters with visual impairment. This case report describes a retired, nationally ranked, competitive target shooter who suffered bilateral visual field loss secondary to nonarteritic anterior ischemic optic neuropathy and diplopia secondary to cerebral vascular accident.

CASE REPORT

A retired 67-year-old white man was referred by a local optometrist to a neuro-ophthalmologist with a suspicious finding of disc pallor and a restriction of the visual field. Examination revealed right hypertropia and visual field defects: binocular superior altitudinal losses and inferior arcuate loss in his dominant, right eye. He had best-corrected distance acuity of 20/20 - 2 in the right eye and 20/25 - 2 in the left eye. Because of this, he received several adaptive rehabilitation devices to help him regain his shooting performance. These included a single-vision add for the pistol sight, yellow tint, low-power telescope, and patching. In this report, the fundamentals of eye care for competitive shooting are described with an emphasis on providing the best acuity for presbyopic patient prescriptions at nonstandard distances and the avoidance of diplopia.

CONCLUSION

A visually impaired sportsman who participated in shooting sports at a high level was attempting to return to his previous shooting performance. This case report shows how sports vision and low vision rehabilitation techniques can improve the visual function of a competitive shooter.

Spatial compression produced by a stationary low-vision telescope

PURPOSE

Geometrical analysis of the monocular information for visual space perception predicts that the magnification produced by a low-vision telescope will compress the depth dimension of space. To test this prediction we measured the compression in depth of perceived shape while looking through a stationary telescope. To control for the other aspects of telescopic viewing, apart from magnification, we also measured perception while looking through a plain tube having the same field of view.

METHODS

A 2.75x Keplarian telescope was mounted 40 cm above a tabletop patterned with receding stripes. The 11.6 degrees field of view was centered on a series of rectangular stimulus cards lying flat on the table at a distance of 100 cm. Participants monocularly viewed each card through the telescope, or through a tube having the same field of view, and verbally judged the card's perceived length (in depth) relative to its width (in the frontal plane).

RESULTS

Perceptual compression of shape was calculated by dividing the perceived proportion (length/width) by the actual proportion. The telescope and the tube both produced significant perceptual compression, but perception was significantly more compressed through the telescope (0.43) than through the tube (0.52).

CONCLUSIONS

The magnification produced by a stationary low-vision telescope can result in a compression of perceived depth. In addition, other aspects of telescopic viewing, such as monocular vision, restricted head movements, and a restricted field of view, can together contribute substantially to such compression. Further research is needed to assess the clinical implications of these results.

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.

Spatial Compression and Adaptation with the Low Vision Telescope

PURPOSE

Geometrical analysis of monocular visual information specifying distance shows that a low vision telescope compresses optically specified distances by a factor about equal to its magnification. Using a group of eight visually healthy adults, we investigated the initial perceptual effect of putting on a 2x Galilean telescope and the adaptation produced by wearing the telescope.

METHODS

Viewing was monocular, and the environment was only visible through the telescope. Because the telescope reduced the field of view to 13 degrees , we also tested a different group of eight visually normal adults who wore a simple monocular tube that restricted the field of view to 13 degrees . We measured perceived distance in a corridor using a visually directed open-loop walking task with distances ranging from 4 to 8 m. For both groups, monocular distance perception was measured before putting on the viewing device (baseline), immediately after putting on the viewing device (preadaptation), after wearing the viewing device during a 30-minute period of visual-motor activities (postadaptation), and immediately after taking off the viewing device (aftereffect).

RESULTS

Comparing preadaptation with baseline measurements, the viewing devices produced a 15.4% initial compression of perceived distance on average. Comparing aftereffect with baseline measurements, the adaptation period produced a negative aftereffect that was 56.5% of the initial compression, thus showing substantial adaptation. The initial compression and the adaptation were highly significant effects, but neither effect was significantly different for the telescope group and the tube group.

CONCLUSION

We conclude that free head movements in a structured environment can largely overcome the optically specified compression of distance produced by the 2x magnification of a low vision telescope, but there remains a significant initial compression of perceived distance that is produced by the restricted field of view. This compression can be substantially reduced by a short period of interaction with the environment.

Face recognition in age related macular degeneration: perceived disability, measured disability, and performance with a bioptic device

AIMS

(1) To explore the relation between performance on tasks of familiar face recognition (FFR) and face expression difference discrimination (FED) with both perceived disability in face recognition and clinical measures of visual function in subjects with age related macular degeneration (AMD). (2) To quantify the gain in performance for face recognition tasks when subjects use a bioptic telescopic low vision device.

METHODS

30 subjects with AMD (age range 66-90 years; visual acuity 0.4-1.4 logMAR) were recruited for the study. Perceived (self rated) disability in face recognition was assessed by an eight item questionnaire covering a range of issues relating to face recognition. Visual functions measured were distance visual acuity (ETDRS logMAR charts), continuous text reading acuity (MNRead charts), contrast sensitivity (Pelli-Robson chart), and colour vision (large panel D-15). In the FFR task, images of famous people had to be identified. FED was assessed by a forced choice test where subjects had to decide which one of four images showed a different facial expression. These tasks were repeated with subjects using a bioptic device.

RESULTS

Overall perceived disability in face recognition did not correlate with performance on either task, although a specific item on difficulty recognising familiar faces did correlate with FFR (r = 0.49, p<0.05). FFR performance was most closely related to distance acuity (r = -0.69, p<0.001), while FED performance was most closely related to continuous text reading acuity (r = -0.79, p<0.001). In multiple regression, neither contrast sensitivity nor colour vision significantly increased the explained variance. When using a bioptic telescope, FFR performance improved in 86% of subjects (median gain = 49%; p<0.001), while FED performance increased in 79% of subjects (median gain = 50%; p<0.01).

CONCLUSION

Distance and reading visual acuity are closely associated with measured task performance in FFR and FED. A bioptic low vision device can offer a significant improvement in performance for face recognition tasks, and may be useful in reducing the handicap associated with this disability. There is, however, little evidence for a correlation between self rated difficulty in face recognition and measured performance for either task. Further work is needed to explore the complex relation between the perception of disability and measured performance.

Vision multiplexing: an engineering approach to vision rehabilitation device development

Multiplexing is the transmission of two or more messages simultaneously over the same communication channel in a way that enables them to be separated and used at the receiving end. The normal visual system provides us with a very wide field of view at an apparent high resolution. The wide field of view is continuously monitored at a low resolution, providing information for navigation and detection of objects of interest. These objects of interest are sampled over time using the high-resolution fovea. Most disabling visual conditions impact only one of the components, the peripheral low-resolution wide field or the central high-resolution fovea. The loss of one of these components prevents the interplay of central and peripheral vision needed for normal function and causes disability. Traditionally low-vision aids replace or supplement the missing function, but usually at a cost of a significant loss in the surviving function. For example, magnifying devices increase resolution but reduce the field of view, whereas minifying devices increase the field of view but reduce resolution. A proposal to resolve many of the problems of current visual aids by exploring a general engineering approach--vision multiplexing--that takes advantage of the dynamic nature of human vision is presented. Vision multiplexing seeks to provide both the wide field of view and the high-resolution information in ways that could be accessed and interpreted by the visual system. This paper describes the use of optical methods and computer technologies in the development of a number of new visual aids, all of which apply vision multiplexing to restore the interplay of central and peripheral vision using eye movements in a natural way.