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Vitamin slows advancing blindness from RP.



It starts as an inability to distinguish features at night. Before long, retinitis pigmentosa Retinitis Pigmentosa Definition

Retinitis pigmentosa (RP) refers to a group of inherited disorders that slowly lead to blindness due to abnormalities of the photoreceptors (primarily the rods) in the retina.
 (RP) leaves its victims with tunnel vision tunnel vision
n.
Vision in which the visual field is severely constricted.


tunnel vision,
n a defect in sight in which a great reduction occurs in the peripheral field of vision, as if one is looking through
 or no sight at all. Though a cure for this inherited disease remains elusive, Boston-area researchers reported this week what appears to be the first successful treatment. Large daily supplements of a particularly stable form of vitamin A slowed the inexorable degeneration of retinal function that characterizes RP.

"This is exciting news;' says Carl Kupfer, director of the National Eye Institute in Bethesda, Md. Worldwide, roughly one in every 4,000 persons suffers from the disease.

Adds Alan M. Laties, chairman of the RP Foundation's scientific advisory board, "Although not a cure, [vitamin A supplementation] will improve the quality of life, potentially adding many years of useful vision."

While monitoring RP patients in the early 1980s, ophthalmologist ophthalmologist /oph·thal·mol·o·gist/ (of?thal-mol´ah-jist) a physician who specializes in ophthalmology.

oph·thal·mol·o·gist
n.
A physician who specializes in ophthalmology.
 Eliot L. Berson and his co-workers identified a small group who had been supplementing their diet with large amounts of vitamin A, vitamin E, or both. And compared to patients taking ordinary multivitamin mul·ti·vi·ta·min
adj.
Containing many vitamins.

n.
A preparation containing many vitamins.


multivitamin 
 supplements or no supplements at all, those taking high doses of A or E sustained far less retinal degeneration over a two-year span, as measured by an electroretinogram e·lec·tro·ret·i·no·gram
n.
Abbr. ERG A graphic record of the electrical activity of the retina.



electroretinogram

the record obtained by electroretinography; abbreviated ERG.
 (ERG). This test determines the health of photoreceptors Photoreceptors
Specialized nerve cells (rods and cones) in the retina that are responsible for vision.

Mentioned in: Macular Degeneration
 by measuring electrical activity o! the eye's photoreceptor cells, known as rods and cones (Anat.) the elongated cells or elements of the sensory layer of the retina, some of which are cylindrical, others somewhat conical.

See also: Rod
.

The finding intrigued Berson, of the Berman-Gund Laboratory for the Study of Retinal Degenerations at Harvard Medical School Harvard Medical School (HMS) is one of the graduate schools of Harvard University. It is a prestigious American medical school located in the Longwood Medical Area of the Mission Hill neighborhood of Boston, Massachusetts.  in Boston, because high ERG values correlate with healthy photoreceptors. However, since most of the megavitamin megavitamin /mega·vi·ta·min/ (meg´ah-vi?tah-min) a dose of vitamin(s) vastly exceeding the amount recommended for nutritional balance.

meg·a·vi·ta·min
n.
 users took both A and E, Berson's team couldn't determine the relative value of the vitamins.

So they initiated a six-year study of 601 RP patients between age 18 and 49. The researchers randomly assigned each patient to one of four daily supplements: 15,000 international units (IU) of vitamin A in the form of retinyI palmitate palmitate

ester of palmitic acid, a common dietary fatty acid.
; 15,000 IU of A plus 400 IU of vitamin E; 400 IU of vitamin E; or trace amounts of both vitamins. Annually, the Harvard researchers assessed ERG values, visual field (peripheral vision), and visual acuity in each patient. Neither patients nor doctors knew which treatment any individual had received.

In the June ARCHIVES OF OPHTHALMOLOGY This article is about the journal published by the American Medical Association. For other journals and uses, see Ophthalmology (disambiguation).

The Archives of Ophthalmology
, Berson's team reports finding a slower drop-off in ERG values among patients receiving 15,000 IU of vitamin A. Those getting large amounts of both vitamins did less well, but better than patients receiving just trace amounts of each.

The big surprise, Berson says, was that retinal degeneration proceeded most quickly in patients given vitamin E supplements. Although the data weren't powerful enough to prove that E posed a risk to patients with the most advanced retinal degeneration at the start of the study, Berson says that "anybody reading this paper would conclude that RP patients shouldn't take high doses of E:'

Overall, the new data suggest, the average RP patient in this study beginning vitamin A therapy at age 32 will retain some useful vision until age 70 -- seven years longer than one taking no supplements and 12 years longer than a patient taking 400 lU of vitamin E daily, Though the Harvard researchers now recommend vitamin A therapy for most RP patients, they caution against taking any form but the palmirate - and then only under an ophthalmologist's supervision.

Vitamin A plays a functional role in sight by latching on to a protein in the rods and cones. When exposed to light, the vitamin changes shape -- the initial step in relaying light-detection signals t0 the brain. "But the mechanism by which vitamin A helps the retina in this disease remains unknown." Berson notes. Vitamin E's role also remains unknown, although Berson's group observed that patients taking vitamin E had lower concentrations of A in their blood, suggesting that E may inhibit the body's absorption or transport of A.

In an accompanying editorial, Robert M. Massof and Daniel Finkelstein of Johns Hopkins University Johns Hopkins University, mainly at Baltimore, Md. Johns Hopkins in 1867 had a group of his associates incorporated as the trustees of a university and a hospital, endowing each with $3.5 million. Daniel C.  in Baltimore describe the new study as "a tour de force in experimental design, execution, and statistical analysis." However, they advise caution in prescribing vitamin A, arguing that the slower declines in ERG readings of A-supplemented patients may not necessarily translate into a slowing o! their loss of visual function.

Berson disagrees. "The editorial implies that visual field is the last word on how people are doing," he told ScIENcE NEws. "But electrical recording should be the last word -- because it's much more sensitive." Indeed, he argues, ERG data are so sensitive they can detect changes that may take 10 or 15 years to confirm through visual-field tests.
COPYRIGHT 1993 Science Service, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1993, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

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Title Annotation:Vitamin A, retinitis pigmentosa
Author:Raloff, Janet
Publication:Science News
Date:Jun 19, 1993
Words:759
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