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Visual function and rhodopsin levels in humans with vitamin A deficiency
C M Kemp1, S G Jacobson, D J Faulkner
1Department of Visual Science, Institute of Ophthalmology, London, England.
Experimental Eye Research
|February 1, 1988
Summary
Vitamin A deficiency causes night blindness by impairing rod and cone function. Supplementation rapidly restored vision, with cones recovering faster than rods.
Area of Science:
- Ophthalmology
- Nutritional Science
- Biochemistry
Background:
- Vitamin A deficiency is a leading cause of preventable blindness worldwide.
- Night blindness is an early symptom, indicating retinal dysfunction.
- Primary biliary cirrhosis and Crohn's disease can impair nutrient absorption, potentially leading to vitamin A deficiency.
Purpose of the Study:
- To investigate the detailed dysfunction of rod and cone photoreceptors in vitamin A deficiency.
- To monitor the recovery of visual function following vitamin A supplementation.
- To correlate rhodopsin levels with visual function during deficiency and recovery.
Main Methods:
- Two-color adaptometry to assess mid-peripheral retinal function.
- Fundus reflectometry to measure rhodopsin levels.
- Case studies of three patients with vitamin A deficiency.
Main Results:
- Initial state: no measurable rod function, delayed cone adaptation, and elevated cone thresholds in some cases.
- Recovery: Normal visual function restored within 8 days of vitamin A supplementation.
- Rhodopsin regeneration was slow when rod adaptation was delayed and incomplete when rod thresholds were significantly elevated.
Conclusions:
- Vitamin A deficiency severely impacts both rod and cone function, leading to night blindness.
- Vitamin A supplementation effectively restores visual function, with cones showing faster initial recovery.
- Rhodopsin regeneration kinetics are directly linked to rod function recovery in vitamin A deficiency.