The eyes are complex sensory organs. About 85% of the total sensory input to our brains originates from our sense of sight, while the other 15% comes from the other four senses of hearing, smell, touch, and taste. The eyes are designed to optimize vision under conditions of varying light. Their location, on the outside of the face, makes them susceptible to trauma, environmental chemicals and particles, and infectious agents. The eyelids and the position of the eye within the bony orbital cavity are the major protective mechanism for the eye.
aerogarden
The eye itself has the shape of a sphere measuring about 1 inch in diameter. It consists of a clear, transparent dome at the front (the cornea) that is surrounded by the white of the eyeball (the sclera). The iris of the eye is the circular, colored portion within the eye, and behind the cornea, and the pupil is the central opening within the iris. Behind the iris and pupil is the eye's lens. The space behind the back of the cornea and the front of the lens is called the anterior chamber and is filled with the aqueous fluid. Behind the lens is a large space that is filled by the transparent vitreous gel. The inside of the back of the eye is lined by the retina, the thin, light-sensitive tissue that changes light images to electrical signals via a chemical reaction. These electrical signals generated by the retina are sent to our brain through the optic nerve. Our brain interprets what our eyes see.
The inner sides of the eyelids, which touch the front surface of surface of the eye, are covered by a thin membrane (the palpebral conjunctiva) that produces mucus to lubricate the eye. This thin membrane folds back on itself and covers the visible sclera of the eyeball. (This continuation of the palpebral conjunctiva is called the bulbar conjunctiva.) Natural oil for the tears is produced by tiny glands located at the edges of the eyelids, providing additional lubrication for the eye. The main component of tears are formed by the lacrimal gland located under the upper lid at the outer corner of the eye. The tears are composed of a combination of the substances produced by the lacrimal gland, the oil glands, and the mucus glands. Tears flow toward the nasal side of the eye and drain into the lacrimal sac in the area between the eye and the side of the nose.
Friday, September 26, 2008
WHICH COMMON DISORDERS OF THE EYES CAN (SOMETIMES) BE SELF TREATED?
Blepharitis: Blepharitis is a common condition that is caused by inflammation of the eyelid. It results in red, scaly, and thickened eyelids and typically some loss of the eyelashes. Blepharitis may be due to either Staphylococcus epidermidis or Staphylococcus aureus (types of bacteria), seborrheic dermatitis (a type of skin inflammation of unknown cause), or a mixture of the two. It is sometimes associated with rosacea of the face. The most common complaints are itching, flaking of the lids, and burning. Blepharitis is initially treated by applying hot compresses to the affected eye, followed by an eyelid scrub. If the condition persists, you should see the doctor, who may prescribe antibiotics.
Lice: The eyelids can become infested with one of two different lice, the crab louse (Phthirus pubis) or the head louse (Pediculus humanus capitis). Lice in the eyelids cause symptoms and signs that are similar to those of blepharitis (red, scaly, and thickened eyelids, usually with some loss of the eyelashes). It is common in young school-age children. One can sometimes see movements of the adult lice at the base of the lashes. Petrolatum or a non-medicated ointment is applied to the eyelid and suffocates the lice eggs. RID, NIX, A-2000, or any other preparation that is designed for use in the hair should not be used near the eyes.
Contact dermatitis: Contact dermatitis is an inflammation of the skin that causes swelling, scaling, or redness of the eyelid with intense itching. This condition usually is triggered by the use of a new product (soap or makeup) or exposure to a foreign substance. If both the upper and lower eyelids are affected, the cause of the inflammation is likely to be an allergic reaction. Antihistamines that are taken by mouth can be used to treat contact dermatitis of the eyelid.
Foreign substance: Lint, dust, an eyelash, or other foreign matter can become stuck in the eye. When the substance cannot easily be removed either with your finger, water, or an eye irrigating solution, a doctor should be seen.
Thermal damage: Thermal damage is a burn injury to eye itself. Exposure to the sun's UV radiation during outdoor activities is an example of minor ocular thermal damage. An eye lubricant can be applied to soothe the eye. If there is no relief to the eye after 24 hours, a physician should be seen. A more severe thermal injury to the eye, for example, from a welder's arc or from sunlamp exposure, warrants the immediate attention of a doctor.
Conjunctivitis: Bacteria, viruses, fungi, allergy, or inflammation-promoting agents can cause inflammation of the palpebral and bulbar conjunctiva, also known as conjunctivitis. The inflammation causes enlargement of the blood vessels in the conjunctiva ("congestion") and causes the conjunctiva to become red ("bloodshot"). Itchy eyes may or may not accompany the inflammation. The eyelids may be stuck together in the morning and there may be tearing or discharge from the eye or eyes. The congestion and itchiness can be temporarily treated with ocular decongestants, but the underlying cause may need treatment as well.
Dry eye: Dry eye is characterized by a white or mildly reddened eye combined with a sandy, gritty, dry feeling. Paradoxically, dry eye can sometimes be accompanied by excessive reflex tearing. The dryness itself can stimulate an increase in the production of tears. Dry eye, also known as KCS or keratoconjunctivitis sicca, is very common and is increasing in frequency due to an aging population and increased pollution in the air. Dry eye is more common in females. It is sometimes associated with dry mouth (Sjogren's syndrome) or autoimmune diseases. Other factors thought to contribute to dry eye are some drugs such as antihistamines, antidepressants, or diuretics (water pills). There are many OTC eye drops available for the self-medication of dry eyes. These vary in their formulations, consistency, and preservatives used. Although these lubricants are effective for treating many cases of dry eye, a physician also should be consulted.
Hordeolum: Commonly referred to as a sty, a hordeolum is an inflammation of the glands within the eyelid. The primary sign of a hordeolum is a tender, raised nodule on the eyelid. Sometimes, the eyelid is so swollen that the eye appears to be completely shut. A hordeolum is usually caused by the same bacteria that are linked to blepharitis. Recurrent hordeolum can be associated with rosacea. Treatment usually is with hot compresses several times per day, but if the problem worsens or does not clear within a week, a physician should be seen. Antibiotics may be necessary.
Chalazion: A chalazion looks similar to a hordeolum. A chalazion is a raised nodule without the tenderness of a hordeolum. Like a hordeolum, it is treated with hot compresses. If the chalazion persists, a physician should be consulted.
Lice: The eyelids can become infested with one of two different lice, the crab louse (Phthirus pubis) or the head louse (Pediculus humanus capitis). Lice in the eyelids cause symptoms and signs that are similar to those of blepharitis (red, scaly, and thickened eyelids, usually with some loss of the eyelashes). It is common in young school-age children. One can sometimes see movements of the adult lice at the base of the lashes. Petrolatum or a non-medicated ointment is applied to the eyelid and suffocates the lice eggs. RID, NIX, A-2000, or any other preparation that is designed for use in the hair should not be used near the eyes.
Contact dermatitis: Contact dermatitis is an inflammation of the skin that causes swelling, scaling, or redness of the eyelid with intense itching. This condition usually is triggered by the use of a new product (soap or makeup) or exposure to a foreign substance. If both the upper and lower eyelids are affected, the cause of the inflammation is likely to be an allergic reaction. Antihistamines that are taken by mouth can be used to treat contact dermatitis of the eyelid.
Foreign substance: Lint, dust, an eyelash, or other foreign matter can become stuck in the eye. When the substance cannot easily be removed either with your finger, water, or an eye irrigating solution, a doctor should be seen.
Thermal damage: Thermal damage is a burn injury to eye itself. Exposure to the sun's UV radiation during outdoor activities is an example of minor ocular thermal damage. An eye lubricant can be applied to soothe the eye. If there is no relief to the eye after 24 hours, a physician should be seen. A more severe thermal injury to the eye, for example, from a welder's arc or from sunlamp exposure, warrants the immediate attention of a doctor.
Conjunctivitis: Bacteria, viruses, fungi, allergy, or inflammation-promoting agents can cause inflammation of the palpebral and bulbar conjunctiva, also known as conjunctivitis. The inflammation causes enlargement of the blood vessels in the conjunctiva ("congestion") and causes the conjunctiva to become red ("bloodshot"). Itchy eyes may or may not accompany the inflammation. The eyelids may be stuck together in the morning and there may be tearing or discharge from the eye or eyes. The congestion and itchiness can be temporarily treated with ocular decongestants, but the underlying cause may need treatment as well.
Dry eye: Dry eye is characterized by a white or mildly reddened eye combined with a sandy, gritty, dry feeling. Paradoxically, dry eye can sometimes be accompanied by excessive reflex tearing. The dryness itself can stimulate an increase in the production of tears. Dry eye, also known as KCS or keratoconjunctivitis sicca, is very common and is increasing in frequency due to an aging population and increased pollution in the air. Dry eye is more common in females. It is sometimes associated with dry mouth (Sjogren's syndrome) or autoimmune diseases. Other factors thought to contribute to dry eye are some drugs such as antihistamines, antidepressants, or diuretics (water pills). There are many OTC eye drops available for the self-medication of dry eyes. These vary in their formulations, consistency, and preservatives used. Although these lubricants are effective for treating many cases of dry eye, a physician also should be consulted.
Hordeolum: Commonly referred to as a sty, a hordeolum is an inflammation of the glands within the eyelid. The primary sign of a hordeolum is a tender, raised nodule on the eyelid. Sometimes, the eyelid is so swollen that the eye appears to be completely shut. A hordeolum is usually caused by the same bacteria that are linked to blepharitis. Recurrent hordeolum can be associated with rosacea. Treatment usually is with hot compresses several times per day, but if the problem worsens or does not clear within a week, a physician should be seen. Antibiotics may be necessary.
Chalazion: A chalazion looks similar to a hordeolum. A chalazion is a raised nodule without the tenderness of a hordeolum. Like a hordeolum, it is treated with hot compresses. If the chalazion persists, a physician should be consulted.
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