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Eyesight: Common Disorders of The Eye
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Eye Diseases

The Structure Of The Eye:

The eyes are complex sensory organs. They 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 are the major protective mechanism for the eye. The eye consists of the eyeball, the upper and lower eyelids, and the conjunctivas. The eyeball 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 eyeball 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 inner sides of the eyelids which touch the eyeball, 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.) The tissue between the skin of the eyelid and the palpebral conjunctiva is filled with glands that secrete sebum, an oily substance that provides additional lubrication for the eye. Tears are formed by the lacrimal gland in the upper, outer corner of the eye and are collected and drained by the lacrimal sac in the inner, lower corner of the eye.

Common Disorders Of The Eye:

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), or seborrheic dermatitis (a type of skin inflammation of unknown cause), or a mixture of the two. The most common complaints are itching 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). 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 make-up) 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 ophthalmic irrigant, 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. An injury to the eye, for example, from a welder's arc, warrants the immediate attention of a doctor.
Conjunctivitis: Bacteria, virus, 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 ("blood-shot"). Itchy eyes may or may not accompany the inflammation. The congestion and itchiness can be 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 feeling. Unlike the name implies, dry eye is accompanied by excessive tearing. Abnormalities of the tears or the lubricants of the eye themselves are thought to reduce the effectiveness of the lubrication. The resulting inadequate lubrication stimulates an increase in the production of tears. Other factors thought to contribute to dry eye are aging and some drugs such as antihistamines, antidepressants, or diuretics (water pills). A different type of dry eye can occur when the flow of tears is reduced because of inflammation and destruction of the lacrimal glands (keratoconjunctivitis sicca). Although lubricants are effective for treating 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. 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.

What common eye conditions usually require treatment by a doctor?

Trauma: Blunt trauma to the eye requires immediate evaluation by an ophthalmologist or optometrist. Trauma to the eye can activate bleeding into the eye from ruptured blood vessels or cause detachment of the retina. Both situations can seriously impair vision. Abrasion: An abrasion usually occurs when a fingernail or metallic foreign object rubs across the cornea or conjunctiva. There is a risk of bacterial or fungal contamination and infection following an eye abrasion. Chemical exposure: Exposure of the eye to household cleaning solutions, fumes, or an actual chemical splash requires immediate evaluation by a physician, though initially it may be self- treated with water or an irrigant.
Keratitis: Keratitis is an inflammation of the cornea that may occur alone or simultaneously with conjunctivitis. The symptoms of keratitis include blurred vision, pain, and intolerance to light (photophobia). Corneal swelling: Corneal swelling, or edema, is a condition in which fluid accumulates in the cornea. The edema causes visual disturbances such as halos or starbursts around lights. Reduced vision may or may not occur. Corneal swelling can arise as a complication of contact lenses, surgical damage to the cornea, or an inherited defect. Hyperosmotics are used to treat corneal swelling, but additional treatment by a physician may be necessary.  
Uveitis: Uveitis is an inflammation of the eye structures in the uveal tract (the iris and other structures within the eye to which the iris attaches). Uveitis may occur without an obvious cause or may be due to trauma or an inflammatory disease in other parts of the body. Symptoms and signs of uveitis are similar to those of conjunctivitis and keratitis.
Angle-Closure Glaucoma: This disorder usually is triggered after an eye exam in which the pupils have been dilated. Angle- closure glaucoma is due to an obstruction of the canal system that drains fluid from the inside of the eye. As a result, fluid accumulates and the pressure within the eye increases. Patients may have a tendency to develop angle-closure glaucoma because of an anatomical defect in their eye. Common symptoms include an aching eyebrow or a headache that leads to nausea and vomiting. Angle-closure glaucoma should be suspected if symptoms develop after an agent is used to dilate the pupils for an eye exam.

OTC Eye-Care Products

There are seven types of OTC eye-care products available. Each product contains one or more active and inactive ingredients.

  1. Artificial tears: Lubricants--also called artificial tears--are synthetic (man-made), water-based solutions that are used to lubricate the eye and thicken tears. Artificial tears are formulated as solutions or drops. The components in artificial tears that provide the lubrication include cellulose ethers (hydroxymethylcellulose or HPMC), polyvinyl alcohol or PVA, povidone or PVP and retinol solutions (containing vitamin A). Examples of artificial tears include Akwa Tears (drops), Tears Naturale, and Refresh Tears. Artificial tears usually are administered three times daily. 
  2. Ointments or Emollients: Ointments also are useful lubricants. These products are not water-based and contain lubricating ingredients similar to petroleum jelly. Examples of ointments include DuraTears Naturale, Lacri-Lube, and Refresh PM. Their advantage over a water-based solution containing HPMC, PVA or PVP is that they remain in the eye longer. Emollients usually are used twice a day.
  3. Eye washes: Eye washes--also known as ocular irrigants--are used to cleanse and/or rinse debris from the eye. These products are balanced to the proper acidity and electrolyte concentration so as to be non-irritating to the eye. Washes are available as liquids, solutions or drops. These products may contain boric acid with sodium borate, sodium phosphate, or sodium hydroxide to maintain the proper acidity. Examples of washes include AK Rinse, Dacriose, and Eye-Stream.
  4. Hyperosmotics: Hyperosmotics are used to treat corneal swelling. Hyperosmotics draw water out of the cornea and thus reduce corneal swelling. Most OTC hyperosmotics contain sodium chloride in various concentrations as either a solution or an ointment. The 2% solution tends to cause less stinging and burning than the 5% solution. An example of a hyperosmotic for corneal swelling is Adsorbon a C. 
  5. Scrubs: Eyelid scrubs are useful for removing oils, debris, or loose skin that can be associated with eyelid inflammation. Soap agents PEG-200 glycerol tallowate or PEG-80 glycerol cocoate provide the foaming action. An example of this type of product is Eye-Scrub. OTC products may contain lubricants alone or lubricants combined with medications usually as medicated eye drops. The medicated eye drops may contain decongestants or antihistamines.
  6. Decongestants: Decongestants are used to shrink swollen blood vessels in the congested (red) eye, for example, in conjunctivitis. Phenylephrine is the most common decongestant for this purpose. Patients with angle-closure glaucoma should cautiously use phenylephrine because it can cause an increase in pressure within the eye. Rebound congestion, in which blood vessels become dilated even with continued use of decongestants, is a common side effect of phenylephrine. Therefore, if no improvement in redness or symptoms occurs within 72 hours of use, phenylephrine should be discontinued. A frequent side effect of phenylephrine is dilation of the pupils. If phenylephrine is absorbed from the eye into the body, an increase in blood pressure may occur, although this is rare. Nevertheless, patients with high blood pressure should be cautious in using phenylephrine. Additionally, if phenylephrine is absorbed, side effects may occur due to interactions with atropine, tricyclic antidepressants (Imipramine) and monoamine oxidase inhibitors such as phenelzine sulfate (Nardil) or tranylcypromine sulfate (Parnate), reserpine (Hydropres), guanethidine (Ismelin), or methyldopa (Aldomet). A second group of chemical decongestants are the imidazoles (naphazoline, tetrahydrozoline, and oxymetazoline). Imidazoles are longer acting than phenylephrine and have fewer side effects, including rebound congestion. Caution still is recommended with imidazoles because of the potential for an increase in blood pressure. Of the three imidazoles, oxymetazoline generally appears to exhibit the least side effects. Naphazoline may dilate pupils more in persons with lightly pigmented (blue or green) eye. Examples of medicated eye drops containing decongestants are Naphcon, Prefrin, and Opcon A.  
  7. Antihistamines: Ocular antihistamines are available OTC. These antihistamines are combined with ocular decongestants for the treatment of congestion (conjunctivitis), particularly when caused by allergy. Pheniramine maleate and antazoline both block histamine receptors in the eye, and thus provide relief from the symptoms of itchy, watery eyes. Antazoline may increase pressure slightly in the eye (of concern to patients with glaucoma) whereas pheniramine maleate has little effect on pressure. Common side effects of antihistamines include burning, stinging, and discomfort in the eye. Important side effects that may be associated with oral antihistamines have not been reported with ocular antihistamines. Antihistamines should not be used in patients at risk for developing angle-closure glaucoma. Examples of products that combine an antihistamine and decongestant are Naphcon A and Ocuhist.
What Inactive Ingredients Are Contained In OTC Eye Care Products?

Most eye care products contain ingredients that have no therapeutic value. If an individual has a known sensitivity to one or more of these ingredients, then products containing them should be avoided: Vehicles: An ophthalmic vehicle is added to a product to enhance drug action by increasing the viscosity (thickness) of the product. Examples of ophthalmic vehicles are Dextran 70, gelatin, glycerin, poloxamer 407, and propylene glycol. Preservatives: Preservatives are included to destroy or limit growth of bacteria that may be introduced into the product during repeated use. Examples of ophthalmic preservatives are benzalkonium chloride (BAK), cetylpyridinium chloride, chlorobutanol, methylparaben, sodium benzoate, and sorbic acid. To avoid allergies, many ophthalmic products are preservative free. Excipients: An excipient is a substance that is added to provide physical form to the product, make it less irritating to the eye, or to preserve the ingredients within the product. Useful ophthalmic excipients are antioxidants, wetting agents, buffers, and tonicity adjusters.

Source: http://www.medicinenet.com
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