5/4/2023 0 Comments Wiki vitamin rThe potentially causative medication may be discontinued and the patient should seek medical attention for a detailed evaluation. 8 All-trans retinoic acid used for acute promyelocytic anemia has also been linked to the presentation of IIH. In various reports, PTC, although rare, is attributed to the use of retinoids for acne (e.g., isotretinoin), psoriasis, and in leukemia 6, excessive dietary 7 (e.g., liver ingestion) and supplement intake. Several case reports over the past few decades have reported a correlation between secondary pseudotumor cerebri (PTC) and hypervitaminosis A or chronic lower doses of retinoid. 5 If oral supplements are inefficient, then IV or intramuscular injections may be considered. Women of reproductive age who are deficient may also need supplementation. High-dose of oral vitamin A supplements are recommended for children to treat xerophthalmia and lower prophylactic dosing can be given for prevention of vitamin A deficiency. Serum vitamin A concentrations are used to determine deficiency defined as less than 0.7 μmol/L in children, and less than 1.05 μmol/L in adults. Vitamin A deficiency also may cause squamous metaplasia of the conjunctiva and the formation of a Bitot’s spot (a well-demarcated area of keratinizing squamous metaplasia on the nasal bulbar or temporal conjunctiva). In severe stages of Vitamin A deficiency, keratomalacia may develop and this ulceration of the cornea can lead to blindness. In the early stages of Vitamin A deficiency, nyctanopia, also known as night blindness, may develop. Vitamin A deficiency can cause a spectrum of eye diseases including xerophthalmia (dryness of the conjunctiva and cornea). 4 Other causes of vitamin A deficiency include inadequate liver stores, liver disease, and the acute phase response. 3 In developing countries, Vitamin A deficiency is because of malnutrition meanwhile in developed countries, although rare, is due to malabsorption following intestinal and bariatric surgery. Over 250 million preschool children are deficient across the globe. Worldwide, vitamin A deficiency is the leading cause of preventable blindness in children, mainly affecting countries in Southeast Asia and Africa. Meta-rhodopsin II production leads to a sequence of events resulting in a change in neurotransmitter release that is communicated to other retinal neurons and ultimately the brain. Photo isomerization of 11-cis-retinal to all-trans-retinal causes conformational alterations in the receptor, consequently producing meta-rhodopsin II. 11-cis-retinal binds opsin and holds the photoreceptor in its stable, inactive form. Other forms of retinol are found in retinal pigment epithelium cells, such as 11-cis-retinal and all-trans-retinal, who both hold an essential role in the visual system. 1 Preformed vitamin A sourced from animal foods (e.g., liver, egg yolks) and provitamin A carotenoids sourced from plant foods (e.g., dark green leafy vegetables, carrots, papaya) or supplements undergo metabolism in the intestine resulting in conversion into retinol. Vitamin A is essential for various life processes such as reproduction, embryo development, growth, cell differentiation, immune function, and vision. This chapter reviews the major vitamins and their various clinical presentations. Deficiencies (or in some cases excess) of these vital amines can produce neuro-ophthalmic disease. Vitamins are essential for biochemical metabolic function. Vitamins in Neuro-ophthalmology Contents: 1.7.2 Albetalipoproteinemia (ABL) and Vitamin E.1.6.4 Thyroid Eye Disease and Vitamin D.
0 Comments
Leave a Reply. |