June 7, 2013 | POSTED BY | Articles, Clinical Optometry, Healthcare
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Nutrition encompasses the way the body uses food to maintain the necessary functions to sustain life. When you eat a healthy meal your body breaks it down and uses it as energy. Vitamin A is an essential nutrient the eye depends on for certain functions crucial to the tissue of the eye. Vitamin A Deficiency (VAD) is a condition where a person is depleted of vitamin A and this can lead to several visual problems. It is an essential nutrient during crucial developmental stages of the eye, and the problems can range from night blindness, to corneal ulcers, to total blindness. The condition can have lasting effects, specifically on a child’s eyes as they develop. Understanding the eye and the way it utilizes vitamin A can help those who are suffering from this major epidemic that leads to blindness in the world today.

The body uses vitamin A to carry out a variety of important metabolisms for maintenance and repair. In the eye a form of vitamin A called Retinol directly affects the rod cells in the retina. The photosensitive pigment of the rod cell called
Rhodopsin uses the Retinol to change shape and allow for adaptation to low levels of light. This metabolism allows for our ability to see in the dark, and to navigate in low light settings. For those who are suffering from VAD, the rod cells of the eye cannot undergo their transformation fast enough to accommodate any new levels of light. This condition is known as Nyctalopia, or night blindness, which is a physiological disorder that indicates some of the first signs of VAD. When night falls those affected by night blindness tend to avert their eyes to any change of light or illumination because they are bothered by the light becoming too bright. Early signs of this condition are usually not found in young children which makes it hard to detect before the conditions of onset VAD worsen.

Having a deficiency of vitamin A can cause severe dry eye, medically known as xerophthalmia, or the inability to produce tears. The eye relies on a source of vitamin A to carry out and maintain a variety of functions to keep the eye healthy. The signs indicating VAD include [1]:

  • Dryness: The lacrimal gland fails to produce tears which causes an insufficent tear film covering the cornea. A poor tear film means pain, poor vision and puts the eye at risk for corneal ulcers and infections. The eye lacks luster and smoothness of the bulbar conjunctiva which begins to resemble dry paint.
  • Unwettability: Due to the absence of tears to the eye; can be a tell-tale sign of VAD and it is described as resembling “sandbanks of receding tide.”
  • Thickening, wrinkling, and pigmentation of the conjunctiva: Begins to change the appearance and translucency of the cornea.
  • Bitot’s Spot and corneal xerosis: These Bitot’s spots are caused by clumps of keratin debris that build up inside the conjunctiva. Both are classically evident at the onset of Vitamin A Deficiency.

Serious problems of VAD begin with the lack of transparency of the cornea, leading to loss of visibility. Clinical signs are indicated under slit lamp examinations, showing evidence in forms of Bitot’s spots which resemble plaque on the conjunctiva and have a foamy surface. Corneal xerosis is the drying of the eye, which loses it’s luster, and the cornea begins to cloud and resemble pebbles on the surface of the eye. Serious cases of VAD will be the development of corneal ulcers, which cannot heal,  or the deformation of the cornea leading to the destruction of the eye entirely.

The body stores a large amount of vitamin A in the liver. Depleting these reserves of vitamin A are usually signs of malnutrition over a long period of time, which leads to the signs of VAD in the eye. A good diet consisting of foods with a large amount of vitamin A is the key to replenishing this reserve. Sources of vitamin A can be found in foods such as dairy products including grass-fed milk, grass-fed butter, and cage free egg yolks, as well as animal livers. Other forms of vitamin A called beta-carotene are found in green leafy vegetables and carrots, which are also a great sources of nutrition.

Those suffering from VAD can reverse the signs with an oral medication. Routine treatment to reverse the effects of VAD to the eye include taking vitamin A capsules totaling 25000 IU (8mg of Retinol) daily until the condition is improved, after which the dosage is lessened in moderation. Many recommend that to offset the drastic changes of the eye by VAD would be to follow a daily regimen of vitamin A as follows [2]:

  • Children 3 years or younger: 600 mcg (2000 IU)
  • Children 4 to 8 years: 900 mcg (3000 IU)
  • Children 9 to 13 years: 1700 mcg (5665 IU)
  • Children 14 to 18 years: 2800 mcg (9335 IU)
  • Adult: 3000 mcg ( 10000 IU)

Vitamin A Deficiency is the leading cause of preventable blindness in children. It is a public health problem around the world, more so in countries where a person’s basic dietary needs are not met. The direction that can be taken in preventing blindness from VAD is to improve intake of vitamin A in young children. If their dietary needs cannot be fulfilled, especially during early development, their future health will be negatively impacted in many ways.

Refrences:

[1]: World Health Organization, Technical Report Series No. 590 (1976),Vitamin A Deficiency and Xerophthalmia, WHO

[2]: Medscape References, Vitamin A Deficiency Treatment and Management, George Ansstas MD., http://emedicine.medscape.com/article/126004-treatment