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216

Wide-Field High-lntensi1y Lantern An Affordable Night Mobility Aid

MICHAEL F. MARMOR, MD, CARROLL AULT, RALPH B. SHAMLIAN

Abstract: 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°) 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. [Key words: glau­coma, high-intensity lamp, retinitis pig­mentosa.] Ophthalmology 87:216-217, 1980

The Wide Angle Mobility Light is a diving lantern which has been modified to provide the battery power and high illumination that is needed by individuals with ocular dis­ease. It is provided with shoulder and waist straps that clip to the handle and allow it to be carried with the hands free (Fig 1). The light uses a 20-watt sealed-beam halogen­cycle bulb (H7554) that produces 1400 can­dle power in a 30° x 20° beam (Fig 2). Since the power required by this bulb is too high for conventional batteries, the lantern is fitted with a rechargeable gel pack which provides one hour of use per charge. The

From the Division of Ophthalmology, Stanford Univer­sity School of Medicine and the Ophthalmology Sec­tion, Veterans Administration Medical Center, Palo Alto, CA.

Presented at the Eighty-Fourth Annual Meeting of the American Academy of Ophthalmology, San Fran­cisco, November 5-9, 1979.

Supported in part by National Eye Institute Grant EY01678 and by the Medical Research Section of the Veterans Administration.

Reprint requests to Michael F. Marmor, MD, Ophthal­mology Section (1128 1 ), Veterans Administration Medical Center, 3801 Miranda Avenue, Palo Alto, CA 94304.

unit is manufactured by Farallon Incorpo­rated (Department E), San Leandro, CA.

Any light should be carried low to the ground for ambulation so that irregularities in the surface will be shown in sharpest re­lief (Fig 3). This is easily achieved with the Wide Angle Mobility Light by holding it at arm's length or using the shoulder and waist straps. Visual function is maintained at its maximum level because acuity, color per­ception and binocular vision are unim­paired. Trials with night blind or field­constricted individuals have shown that, using the new light, they can walk almost as freely at night as during the day. Since the hands may be kept free, the light can be used for tasks like taking out the garbage which would not be feasible with a hand­held device. The light may also be set down to search for objects, set up a camp, or even fish at night.

Fig 1. The Wide Angle Mobility Light. The straps may be removed if desired.

0161-6420/80/0300/0216/$00.60 ©American Academy of Ophthalmology

Fig 2. Relationship of the area illuminated by different flashlights to a narrowed central field.

Fig 3. Illumination of the ground by the Wide Angle Mobility Light (left) and an ordinary flashlight (right).

Most night vtswn aids either illuminate the environment or amplify the available light, and there are advantages to each ap­proach. The most publicized light amplifi­cation device is the ITT night vision pock­etscope, 1 a small instrument which is hand-held in front of one eye. It is more discrete than a flashlight, especially for in­door use. However, it is less convenient for ambulation because it must be held up to the eye, the image is monocular and monochromatic, and it causes some degra­dation of acuity. Only a limited number of

night vision pocketscopes are being made and their cost is prohibitive, whereas the Wide Angle Mobility Light was designed specifically to be available and affordable to the average patient.

REFERENCE

1. Berson EL, Mehaffey L Ill, Rabin AR. A night vi­sion pocketscope for patients with retinitis pig­mentosa. Arch Ophthalmol 1974; 91:495-500.

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