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The Night Vision Threshold Test (NVTT): a simple instrument for testing dark adaptation in young children
B Duncan1, L Canfield, B Barber
1Department of Pediatrics, College of Medicine, University of Arizona, Tucson 85724, USA. bduncan@peds.arizona.edu
Insights
A new, low-cost instrument effectively assesses vitamin A deficiency in young children by measuring their dark adaptation. This simple test shows promise for identifying at-risk children, helping to prevent severe deficiency and vision loss globally.
Area of Science:
- Public Health
- Nutrition Science
- Ophthalmology
Background:
- Vitamin A deficiency affects 41% of children under 5 in developing nations, causing significant morbidity, mortality, and blindness.
- Half a million children annually experience blindness, and 13.5 million suffer from night blindness due to vitamin A deficiency.
- Current methods for identifying marginal vitamin A levels in young children are not simple, sensitive, or inexpensive.
Purpose of the Study:
- To evaluate a novel, low-cost instrument designed to assess dark adaptation in young children.
- To determine if the instrument can identify children with marginal vitamin A status.
Main Methods:
- A simple, easy-to-use instrument measuring dark adaptation was tested.
- The study involved children admitted to the Mwanamugimu Nutrition Unit in Kampala, Uganda.
- Night Vision Threshold Test results were correlated with serum retinol levels.
Main Results:
- The Night Vision Threshold Test results showed a significant correlation with serum retinol levels (r = 0.41, p < 0.05) in malnourished children.
- Despite severe malnutrition, the instrument demonstrated a relationship with a key indicator of vitamin A status.
- The findings suggest the instrument's potential utility in identifying vitamin A deficiency.
Conclusions:
- The developed instrument shows promise as a simple and inexpensive tool for assessing vitamin A status in young children.
- Further efficacy trials are planned in community settings in Nepal to validate these findings.
- This tool could aid in the early identification and prevention of severe vitamin A deficiency and its consequences, such as blindness.
Abstract:
It is estimated that 41 per cent of the population aged under 5 in the developing world has an inadequate vitamin A dietary intake resulting in increased morbidity and mortality. Half a million children go blind each year as a result of vitamin A deficiency. Thirteen and a half million have night blindness, the first sign of vitamin A deficiency. Unfortunately, there is no simple, sensitive and inexpensive means to identify the child who has marginal levels of vitamin A and thus institute means to prevent their development of severe deficiency. A low cost, simple, easy-to-use instrument designed to detect a young child's ability to adapt to darkness was tested in children admitted to the Mwanamugimu Nutrition Unit at Makerere Medical School in Kampala, Uganda. Despite the severe degree of malnutrition found in these children, Night Vision Threshold Test results and serum retinol levels were related (r = 0.41, p < 0.05). Further efficacy trials for this instrument are planned at community sites in Nepal.