tretinoin and Night-Blindness

Vitamin A is essential for multiple functions in mammals. Without vitamin A, mammals cannot grow, reproduce, or fight off disease. Because of its numerous functions in humans, biomarkers of vitamin A status are quite diverse. Assessment of liver reserves of vitamin A is considered the gold standard because the liver is the major storage organ. However, this measure is not feasible in human studies. Alternative biomarkers of status can be classified as biological, functional, histologic, and biochemical. Historically, signs of xerophthalmia were used to determine vitamin A deficiency. Before overt clinical damage to the eye, individuals who suffer from vitamin A deficiency are plagued by night blindness and longer vision-restoration times. These types of assessments require large population-based evaluations. Therefore, surrogate biochemical measures of vitamin A status, as defined by liver reserves, have been developed. Serum retinol concentrations are a common method used to evaluate vitamin A deficiency. Serum retinol concentrations are homeostatically controlled until liver reserves are dangerously low. Therefore, other biochemical methods that respond to liver reserves in the marginal category were developed. These included dose-response tests and isotope dilution assays. Dose-response tests work on the principle that apo-retinol-binding protein builds up in the liver as liver reserves become depleted. A challenge dose of vitamin A binds to this protein, and serum concentrations increase within a few hours if liver vitamin A concentrations are low. Isotope dilution assays use stable isotopes as tracers of total body reserves of vitamin A and evaluate a wide range of liver reserves. Resources available and study objectives often dictate the choice of a biomarker.

Topics: Biomarkers; Biopsy; Humans; Liver; Milk, Human; Night Blindness; Nutritional Status; Tretinoin; Vitamin A; Vitamin A Deficiency

Topics: Animals; Diagnosis, Differential; Hearing Disorders; Humans; Neural Tube Defects; Night Blindness; Prognosis; Retinol-Binding Proteins; Tretinoin; Vitamin A Deficiency

Topics: Electroretinography; Eye; Fenretinide; Humans; Neoplasms; Night Blindness; Tretinoin

Drugs which affect the processing of vitamin A in the retina or pigment epithelium can cause ocular toxicity. It is shown here that the retinoic acids, which are used in the treatment of skin disorders and which cause night blindness, inhibit the ocular retinol dehydrogenases in an in vitro system. This is shown to lead to a decrease in the formation of the visual chromophore 11-cis-retinal, thus explaining why night blindness might occur.

Topics: Alcohol Oxidoreductases; Animals; Diterpenes; Night Blindness; Pigment Epithelium of Eye; Rana pipiens; Retina; Retinaldehyde; Retinyl Esters; Tretinoin; Vitamin A

Isotretinoin (Accutane Capsules) is a synthetic vitamin A compound used for treatment of recalcitrant cystic acne. It has numerous ocular toxic side effects which include anterior segment inflammation, dry eye syndrome, contact lens intolerance, altered refraction, photosensitivity, and reduced night vision. Eye care practitioners should be aware of these potential side effects and be prepared to communicate with the prescribing physician if side effects present.

Topics: Anterior Eye Segment; Epithelium; Eye Diseases; Humans; Isotretinoin; Night Blindness; Papilledema; Photosensitivity Disorders; Refraction, Ocular; Reproduction; Retina; Tretinoin; Vitamin A

Topics: Adult; Aged; Drug Eruptions; Female; Fenretinide; Humans; Male; Night Blindness; Psoriasis; Tretinoin

Topics: Animals; Biology; History, 20th Century; Massachusetts; Night Blindness; Rats; Retina; Tretinoin; United States; Vitamin A; Vitamin A Deficiency