Eyes And Ears
The most common eye and ear disorders are infection and inflammation (sometimes caused by allergy). Many parts of the eye may be affected, notably the conjunctiva (membrane that covers the front of the eye and lines the eyelids) and the iris. The middle and outer ear are more commonly affected by infection than the inner ear.
The eye is subject to a disorder known as glaucoma, in which pressure of fluid within the eye builds up and may eventually threaten vision. An eye disorder such as retinopathy (disease of the retina) may occur as a result of diabetes or hypertension and is controlled by treatment of the primary problem.
Other disorders affecting the ear include buildup of wax (cerumen) in the outer ear canal and disturbances to the balance mechanism.
Medicaments for glaucoma
Glaucoma is the name given to a group of conditions in which the pressure in the eye builds up to an abnormally high level. This compresses the blood vessels supplying the nerve that connects the eye to the brain (optic nerve) and may lead to irreversible nerve damage and permanent loss of vision.
In the most common type of glaucoma known as chronic (or open-angle) glaucoma, reduced drainage of fluid from the eye causes pressure inside the eye to build up slowly. Progressive reduction in the peripheral field of vision may take months or years to be noticed. Acute (or closed-angle) glaucoma occurs when drainage of fluid is suddenly blocked by the iris. Fluid pressure builds up quite suddenly, blurring vision in the affected eye. The eye becomes red and painful, accompanied by a headache and sometimes vomiting. The main attack is often preceded by milder warning attacks such as seeing halos around lights in the previous weeks or months. Elderly, farsighted people are particularly at risk of developing acute glaucoma. The angle may also narrow suddenly following injury or after taking certain medicaments, for example, anticholinergic medicaments.
Medicaments are used in the treatment of both types of glaucoma. These include miotics, beta blockers, and certain diuretics (carbonic anhydrase inhibitors and osmotics).
The medicaments used to treat glaucoma act in various ways to reduce the pressure of fluid in the eye. Miotics improve the drainage of the fluid out of the eye. In chronic glaucoma this is achieved by increasing the outflow of aqueous humor through the drainage channel called the trabecular meshwork. In acute glaucoma the pupil-constricting effect of miotics pulls the iris away from the drainage channel, allowing the aqueous humor to flow out normally. Beta blockers and carbonic anhydrase inhibitors act on the fluid-producing cells inside the eye to reduce the output of aqueous humor.
Medicaments for acute glaucoma act quickly, relieving pain and other symptoms within a few hours. The benefits of medicament treatment in chronic glaucoma may not be immediately apparent since treatment only halts a further deterioration of vision.
People receiving miotic eye drops are likely to notice darkening of vision and difficulty seeing in the dark. Increased shortsightedness may be noticeable. Some miotics also cause irritation and redness of the eyes.
Beta blocker eye drops have few day-to-day side effects but carry risks for a few people. Acetazolamide usually causes an increase in frequency of urination and thirst. Nausea and general malaise are also common.
Miotics are generally risk-free. If beta blockers are absorbed into the body they can affect the lungs, heart, and circulation. For this reason, they are prescribed with caution to people with asthma or certain circulatory disorders and in some cases they are withheld altogether. The amount of the medicament absorbed into the body can be reduced by applying the eye drops carefully. Acetazolamide is not normally prescribed for prolonged treatment because of its troublesome adverse effects, including painful tingling of the hands and feet. It may encourage the formation of kidney stones and may in rare cases cause kidney damage. People with existing kidney problems are not usually given this medicament.
Medicaments affecting the pupil
The pupil of the eye is the circular opening in the center of the iris (the colored part of the eye) through which light enters. It continually changes in size to adjust to variations in the intensity of light; in bright light it becomes quite small (constricts), but in dim light the pupil enlarges (dilates).
Eye drops containing medicaments that act on the pupil are widely used by specialist eye physicians. They are of two types: those that dilate the pupil, known as mydriatics; and those that constrict the pupil, known as miotics.
The size of the pupil of the eye is controlled by two separate sets of muscles in the iris, the circular muscle and the radial muscle. Each set of muscles is governed by a separate branch of the autonomic nervous system: the sympathetic nervous system controls the radial muscle, and the parasympathetic nervous system controls the circular muscle.
Individual mydriatic and miotic medicaments act on different branches of the autonomic nervous system, and cause the pupil of the eye either to dilate or to contract, depending on the type of medicament being used.
Mydriatic medicaments -especially the long acting types -impair the ability to focus the eye(s) for several hours after use. This interferes particularly with close activities such as reading. Bright light may cause discomfort. Miotics often interfere with night vision and may cause temporary short sight (myopia).
Normally, eye drops produce few serious adverse effects. Sympathomimetic mydriatics may raise blood pressure and are used with caution in people with heart disease or hypertension. Miotics may irritate the eye, but rarely cause generalized effects.
Medicaments for ear disorders
Inflammation and infection of the outer and the middle ear are the most common disorders affecting the ear that are treated with medicaments. The type of medicament treatment given for ear inflammation depends on the cause of the trouble and the site affected.
Inflammation of the outer ear
Infection of the middle ear