The conjunctiva is the thin, transparent tissue that lines the eyelids and surface of the eye. The swelling of conjunctiva is termed as chemosis. The swelling is due to accumulation of fluid. Due to the swelling, the eyes cannot close properly and affects visual acuity. Chemosis is alternatively referred to as fluid-filled conjunctiva, swollen eye or conjunctiva.
The most common symptom associated with chemosis is swelling of the eye and the eye appearing red in color. In most of the cases, chemosis is caused by an allergic reaction, viral infection as well as by rubbing of the eye. Exophthalmos, a sign of hyperthyroidism, which results in abnormal bulging of one or both eyes, may also be associated with Chemosis.
Treatment of chemosis depends on its cause. Home care treatment options of chemosis due to angioedema or allergies includes using over-the-counter antihistmine medications and placing cool clothes on the eyes. It is best to contact health care provider in case the symptoms continue. The health care provider may diagnose by conducting a physical examination of the eye. Certain questions to understand the history of swelling of the eye and discomfort it causes will be asked. The health care provider will then prescribe an eye cream to reduce the swelling and antibiotics medications.
The conjunctiva is a clear membrane covering the white of the eyes. Conjunctivitis, also known as pinkeye occurs when the conjunctiva in the eye gets inflamed. This common eye infection is not serious but is highly contagious and causes discomfort. Conjunctivitis can occur due to an infection, allergy or chemical reaction. Commonly infectious conjunctivitis happens due to viral or bacterial infection such as Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus. Allergic conjunctivitis occurs as a result of allergy to pollen, animal dander, dust mites or cosmetics or even hay fever. Chemical reaction can lead to conjunctivitis due to irritation. This happens due to chlorine in swimming pools or smoke and fumes.
Children suffering from conjunctivitis may have ear infection or sore throat. The infection can pass through coughing, sneezing and direct contact with tissues, clothes or towels used by an infected person. Conjunctivitis caused by allergy or chemicals however are not contagious. Typical symptoms of conjunctivitis range from redness and discomfort in the eyes to swelling and tearing. There is itchiness and sensitivity to bright light. Eyes affected by conjunctivitis tend to water and exude sticky discharge, especially on waking up. There might be pink or reddish blots on the eye due to inflammation.
Broad spectrum antibiotic ointment or solution is prescribed for bacterial infection. antihistamines are used for allergic conjunctivitis. Corticosteroid drops are prescribed in cases of severe allergic conjunctivitis. It is essential to identify the allergen and take precautions against exposure to it. Do not share tissues, makeup, towels or eye drops. Wash your hands after touching your eyes.
Vitamin A is a fat soluble vitamin which is derived from beta carotene which plays a significant role in the process of vision and other important metabolic pathways pertaining to cell division and genetic expression. The significant forms of vitamin A include retinol, retinal, retinoic acid and retinyl esters. There are approximately six hundred derivatives of beta carotenes and the most important form is retinol.
Functions of Vitamin A
Vitamin A is essential for many metabolic pathways in the body. It is the chief requirement for the function of the rhodopsin protein located in the retina to absorb light and to differentiate functions of the cornea and the conjunctival membranes. Vitamin A is essential for normal functioning of the retina. Apart from this, vitamin A plays a significant role in immune system functions, cell signaling and cellular communication and reproduction. The functions and pathways associated with vitamin A are directly related to the functionality of vital organs such as heart, brain, lungs, liver and kidneys. Hence vitamin A is also known as an important antioxidant. Besides it is required for the growth and differentiation of epithelial tissue, normal growth of bone and embryonic development. Most of our body's Vitamin A is stored in the liver in the form of retinyl esters.
Vitamin A Deficiency: Poor adaptation of vision to darkness or what is known as night blindness is an early symptom that may be followed by degenerative changes in the retina. Degenerative changes in eyes and skin are commonly observed in vitamin A deficiency. The predominant form of vitamin A deficiency is Nyctalopia or night blindness. This occurs as result of retinol imbalance which is the chief derivative of vitamin A. In third-world, vitamin A deficiency is the primary cause of blindness. Pregnant and lactating women, premature children, children living in rural areas of developing countries and patients who have a history of liver diseases such cirrhosis and cystic fibrosis are most susceptible to Vitamin A deficiency. Severe or prolonged deficiency may lead to dry eye or Xerophthalmia (dryness in conjunctiva and cornea of the eye) that can result in corneal ulcers, inflammation, ridge formation, scarring and eventually blindness. Xerophthalmia is due to lacrimal gland dysfunction. Other associated conditions include keratomalacia and follicular hyperkeratosis. Another important consequence of Vitamin A deficiency is acquired immunodeficiency disease, with an increased incidence of death related to infectious diseases. Vitamin A deficiency is associated with increased disease progression and mortality in HIV patients.
World Health Organization (WHO) Recommendations for Vitamin A:
Supplementation may be required in cases where the blood Vitamin A level falls below 20 µg/dL.
Severe deficiency is < 10 µg/dL
Food sources and recommended dietary allowance
Vitamin A is naturally available in dairy products such as milk, cheese, curd, cream. Meat products like liver and fish oil and leafy vegetables are excellent sources of vitamin A. Other sources include pumpkin, potatoes, broccoli, cereals, beans and cow peas. Studies indicate that the intensity of the fruit or vegetable color is directly proportional to the amount of vitamin A present in it. The recommended intake of vitamin A per day for children 500 micrograms, males 1000 micrograms and females 800 micrograms respectively.
RDAs (recommended dietary allowance) for vitamin A are given as mcg of retinol activity equivalents (RAE) to account for the different bioactivities of retinol and provitamin A carotenoids. FDA may introduce new labeling regulations in the near future which may result in listing Vitamin A with RAE values rather than in IU.
The following table shows conversion rates of mcg of RAE (retinol activity equivalents):
Essentially all dietary sources of vitamin A are converted into retinol by the body: 1 mcg of physiologically available retinol is equivalent to the following amounts from dietary sources:
Hypervitaminosis A: Vitamin A in excess can be toxic. According to WHO, values in excess of 120 µg/dL is Hypervitaminosis A. Chronic vitamin A over dosage may be a serious issue in normal adults who take more than 15 mg per day and in children who take more than 6 mg per day of vitamin A over a period of several months. Symptoms can include :
Other than that some symptoms such as pain, vomiting, alopecia and bone demineralization may result due to excessive intake of Vitamin A. In pregnant women, an over dose of Vitamin A over a period of time may result in spontaneous abortions or Congenital malformations, craniofacial abnormalities and valvular heart disease in the baby.
However, unlike preformed Vitamin A, beta-carotene is not known to be teratogenic (reproductive toxicity). Even a relatively large supplemental doses of beta carotene or eating carotenoid rich food for long duration need not result in toxicity always. Rarely a reversible condition known as carotenodermia - where the skin turns yellow/orange might be the result of long term over dosage of beta carotene.
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Bibliography / Reference
Collection of Pages - Last revised Date: January 26, 2020