Night-vision aid using see-through display for patients with retinitis pigmentosa.

PURPOSE: From an early stage, retinitis pigmentosa (RP) patients suffer from night blindness which causes nocturnal mobility difficulties. We created a wearable visual aid that uses a high-performance see-through display, and added a high-sensitivity camera with a complementary metal-oxide-semiconductor sensor. Here, we evaluate the device's efficacy for helping night-blindness sufferers walk in the dark. STUDY DESIGN: Prospective clinical study. METHODS: Twenty-eight subjects underwent binocular visual acuity testing in the dark without (power off) and with (power on) the device. The test was carried out in a darkened room. We recorded the number of trial errors and the time it took each subject to arrive at the goal both with and without the aid of our device. RESULTS: Our device effectively assists walking in RP patients with mobility problems in the dark. CONCLUSION: Binocular visual acuity in the dark was significantly improved with the aid of our device. In the walking test, the number of errors decreased greatly with the device, and the travel time was significantly shortened.

Development and evaluation of a visual aid using see-through display for patients with retinitis pigmentosa.

PURPOSE: Patients in the early stage of retinitis pigmentosa (RP) suffer from night blindness and, therefore, have mobility problems at night. To assist such patients with walking in the dark, we developed a wearable visual aid utilizing a see-through display upon which assistive images from a high-sensitivity video camera are superimposed. We evaluated the efficacy of our new visual aid for RP patients. METHODS: The device is equipped with a camera with a minimum illuminance of 0.08 lux and a view angle of 53° × 40°. The experiment was conducted in a room with dimmed light (illuminance level 0.2-1.2 lux). Eight subjects with RP were instructed to arrive at a goal 16 m away from the starting point, both with and without the device, passing through four 1.5-m-wide gates consisting of pairs of black square carpet pieces, white poles, red and white traffic cones and cardboard boxes with and without the device in a darkened room. Three gates, except for the boxes, which were nearest the goal, were randomly arranged along the x-axis at each trial. The number of trial failures and the time required to walk the course were assessed as outcomes. RESULTS: Seven of the 8 subjects could walk with the aid of the device without any failure. With the device, the number of trial failures significantly decreased in number (p < 0.05) in all subjects. CONCLUSIONS: This device enabled the subjects to see objects that could not be recognized by the unaided eye. Our visual aid effectively assisted RP patients with night blindness.

Night-vision goggles for night-blind subjects: subjective evaluation after 2 years of use.

PURPOSE: To evaluate the usefulness of night-vision goggles (NVG) for night-blind subjects after 1 and 2 years of use. METHODS: Eleven night-blind subjects with retinitis pigmentosa used NVG for a 2-year period. At the end of each year, they were requested to fill-in two questionnaires regarding their use of the instrument. RESULTS: At both the 1- and 2-year evaluations, the subjects reported fewer problems with mobility in the dark when they used the goggles. At the 2-year evaluation, two individuals stated that they had stopped using the instrument, while seven used it at least twice a week. The nine subjects still using the instrument after 2 years reported an increase in their sense of independence and an increase in their potential for activities. The instrument was used most often during the dark winter season and for purposes such as visiting friends and family, travelling to work or sports, attending meetings and strolling. CONCLUSION: At the 2-year follow-up, NVG were still being used by most of the night-blind subjects. Moreover, the device had a positive effect on the subjects' experienced opportunities and sense of independence. The instrument was considered useful in the daily lives of our subjects.

Improving nighttime mobility in persons with night blindness caused by retinitis pigmentosa: A comparison of two low-vision mobility devices.

This study compared the effectiveness of the ITT Night Vision Viewer with the Wide Angle Mobility Lamp (WAML) as low-vision mobility devices for people experiencing night blindness due to retinitis pigmentosa (RP). Both engineering bench testing and functional evaluations were used in the assessments. Engineering evaluations were conducted for (1) consistency of the manufacturer's specifications, (2) ergonomic characteristics, (3) modifications of devices, and (4) pedestrian safety issues. Twenty-seven patients with RP conducted rehabilitation evaluations with each device that included both clinical and functional tests. Both devices improved nighttime travel for people with night blindness as compared with nighttime travel with no device. Overall, the WAML provided better travel efficiency-equivalent to that measured in daytime. Recommendations have been developed on ergonomic factors for both devices. Although some participants preferred the ITT Night Vision Viewer, overall most participants performed better with the WAML.

Improved mobility and independence of night-blind people using night-vision goggles.

PURPOSE: To investigate whether the use of night-vision goggles (NVGs) by night-blind people improves their mobility and sense of independence under dark circumstances. METHODS: Twenty night-blind subjects with retinitis pigmentosa were requested to walk predetermined routes at night with and without NVGs. The number of unintended contacts with obstacles (hits) and the percentage of preferred walking speed (PPWS) en route were assessed in three different situations: a darkened indoor corridor; a moderately lit outdoor residential area; and a well-lit outdoor shopping area. Assessments were performed before and after a 5-week training period, during which the subjects practiced using NVGs in their own surroundings, registered their experiences in a journal, and filled out questionnaires. RESULTS: The mean number of hits in the darkened corridor declined from eight to two when NVGs were used. Mean PPWS (34%) did not improve. In the residential area, mean hits declined from eight to practically zero and mean PPWS increased from 60% to 72% (after training to 78%). In the shopping area, subjects walked at 93% PPWS without any hits and showed no improvement with NVGs. Subjective scores revealed a good sense of orientation, feelings of safety and tranquility and an increase in independent mobility when NVGs were used. CONCLUSIONS: Using NVGs seems to improve nighttime mobility in dark outdoor conditions by decreasing unintended contacts with obstacles and increasing walking speed. Use of NVGs increased independent activities in these subjects and was generally positively evaluated for everyday outdoor use.

[Utilization of a new night vision enhancement device (DAVIS)]. / Einsatz einer neuen Nachtsichtbrille (DAVIS).

PATIENTS AND METHODS: Following complete ophthalmologic examination 37 patients with night blindness due to Retinitis Pigmentosa (sometimes Usher-Syndrome) and Choroideremia (n = 3) performed several tests with DAVIS during darkness. We evaluated the improvement of visual function on a special outside course in the city of Heidelberg (duration 1.5 to 4 hours). RESULTS: Twenty six of the patients were able to better recognize obstacles, 28 could see objects which were not seen without DAVIS. Twenty two of the 37 patients would use the DAVIS. Patients needed a visual acuity of more than 0.1 and more than 6 degree of central visual field to experience improvement with DAVIS. However, in patients with only minimal changes of the visual field, the restriction due to the presence of the device was a drawback. Sudden occurrence of light sources leads to blinding and limits the indoor use. CONCLUSION: DAVIS enhances contrast acuity especially during night and twilight. This leads to improvement of orientation due to better recognition of obstacles and allows rehabilitation of patients with night blindness for outdoor mobility. Individual test and adjustment of DAVIS is necessary to allow exact and adequate prescription.

[An electronic visual aid using a luminance amplifier in night vision disorders]. / Aide visuelle électronique par amplificateur de luminance dans les altérations de la vision nocturne.

The efficiency of a light amplifier system for the improvement of night vision has been tested on 30 normal subjects and on subjects suffering from night blindness including 36 patients with pigmentary retinopathy, 18 myopic patients with night blindness and 12 patients with senile cataracts. In all cases, the scotopic vision presented a great improvement and it reached up to half of photopic vision. The use of the light amplifier would certainly provide a considerable improvement for subjects suffering from night blindness and mostly for those suffering from pigmentary retinopathy. But two conditions are necessary for this: miniaturization of the device and absence of major macular lesions in the patient.

An evaluation of night vision mobility aids.

Two night vision aids are commercially available to help individuals who have diseases that cause night blindness. The ITT Night Vision Aid (NVA) is a light amplification device; the Wide Angle Mobility Light (WAML) is a wide beam flashlight. The effectiveness of both instruments in helping night-blind, field-restricted subjects to walk a course of residential streets at night was tested. WAML users were also surveyed to determine the usage, applications, and reliability of the device. We found that the WAML significantly reduced error rates and was preferred by most subjects; it was reported to be used regularly by individuals who owned it. The NVA did not significantly improve error scores, and was not effective as an ambulatory night mobility aid for most patients.

Visual acuity with the ITT Night Vision Aid for patients with night blindness.

The Night Vision Aid is a photomultiplier device developed by International Telephone and Telegraph Co. (ITT) and the Retinitis Pigmentosa Foundation as a mobility aid for those with night blindness. The purpose of this study was to measure visual acuity with and without the Night Vision Aid at a variety of light levels to determine how much visual assistance it provided over a wide range of illuminations. Ten normal subjects and five patients with retinitis pigmentosa (RP) used the aid at nine luminance levels ranging from 10(-6) to 10(2) ml. With the device, visual acuity improved at light levels below 0.1 ml and target visibility was extended about 3 log units further into low luminance. At light levels above 0.1 mL, unassisted visual acuity was better in all normal and most RP subjects. The best visual acuity attained with the Night Vision Aid was 6/15 (20/50). Graphs and dark adaptation curves illustrate our findings.

Wide-field high-intensity lantern. An affordable night mobility aid.

Individuals with disorders such as retinitis pigmentosa or severe glaucoma often have difficulty ambulating at night, not only because they have lost rod vision, but because flashlights do not help. The problem is that ordinary flashlights produce a very narrow beam of light (only about 3 degrees) which is hard to follow with tunnel vision. To eliminate this problem, we have designed a relatively inexpensive lantern which produces a bright wide beam of light. It can greatly enhance the night mobility of patients with severe field constriction or night blindness.

An image intensifier aid for chronic night blindness.

Working with the Retinitis Pigmentosa Foundation, ITT has designed an image intensifier monocular specifically for application as a prosthetic aid for persons suffering from chronic night blindness as a result of retinal degenerations. A description of the instrument along with the rationale for its major design points is given and its applications illustrated. The first few of these instruments were delivered earlier this year and limited production has been started.

The development of the Generation II as an aid for patients with retinitis pigmentosa and night blindness.

The Generation II is a modification of the Army's night photography/observation instrumentaton. Low levels of light are intensified approximately 700 times to stimulate cone function. The individual with no rod function is able to see at night under these intensified amounts of illumination. The device can be used for night "spotting and mobility" purposes, much like a telescope is used during the day by the partially-sighted with intact rod function and poor cone function. This paper is presented to inform the optometrist of the availability and usefullness of this device for his patients.