Diseases of the eyes

Diseases of the Eyes

Night Blindness

Inability to see well at night or in poor light. It is not a disorder in itself, but rather a symptom of an underlying disorder or problem, especially untreated myopia (nearsightedness).

Night blindness may exist from birth, or be caused by injury or malnutrition. It can be described as insufficient adaptation to darkness.

Causes

• Myopia• Glaucoma medications that

work by constricting the pupil• Cataracts• Retinitis pigmentosa• Vitamin A deficiency

Treatment

Depends upon its cause. Treatment may be as simple as getting a new eyeglass prescription or switching glaucoma medications, or it may require surgery if the night blindness is caused by cataracts

Cataracts

Is the clouding of the lens of the eye, which impedes the passage of light.

Although most cases of cataract are related to the aging process, occasionally children can be born with the condition, or a cataract may develop after eye injuries, inflammation, and some other eye diseases

Impaired Vision due to Cataract

Cataract Surgery

Causes vision to become hazy and distorted.

Causes

oDiabetes Mellitus oFrequent exposure to sunlightoHeavy smoking

Treatment

Surgical removal of the lens and replacement with a lens implant or special cataract glasses.

Glaucomaa term describing a group of ocular disorders

with multi-factorial etiology united by a clinically characteristic intraocular pressure-associated optic neuropathy.]This can permanently damage vision in the affected eye(s) and lead to blindness if left untreated. It is normally associated with increased fluid pressure in the eye .

Stills sight slowly and painlessly until damage is done.

Tonometer- used to measure the intraocular pressure.

The front part of the eye is filled with a watery fluid, known as the aqueous humor. This fluid helps the eye maintain its shape and delivers oxygen and nutrients to the cornea and the lens, the eye structure that refracts light to form images. The aqueous humor is produced by the ciliary body, a small gland located just behind the lens. The fluid percolates through the pupil and circulates through the front chamber of the eye. It then drains away through a network of tiny channels, called the trabecular meshwork, located at the front of the eye where the cornea and iris

CauseWhen the aqueous humor does not drain

properly, the fluid backs up, causing the pressure inside the eye to increase, and glaucoma develops. The increased pressure inside the eye compresses and damages the optic nerve, the bundle of nerve cells that transmit visual information from the eye to the brain. This damage to the optic nerve results in vision loss. In chronic simple glaucoma, the aqueous humor drains through the trabecular meshwork more slowly than normal, much as a sink empties more slowly when the drain is clogged.

Vision Loss due to Glaucoma

Signs and SymptomsThe gradual increase of pressure inside

the eye does not cause any pain or discomfort. As the disease progresses, however, vision begins to deteriorate. The deterioration usually begins with the peripheral vision—sight at the outer edges of the visual field. If glaucoma is left untreated, the field of vision continues to shrink until a person becomes blind.

TreatmentEyedrops- increases the rate of aqueous

humor drainage. Laser or Surgical enlargement of the drainage

of channels can be used. Opthalmoscope- instrument that illuminates

the inferior of the eyeball allowing the retina, optic disc, and internal blood vessels at the fundus, or posterior wall of the eye to be viewed and examined. Certain pathological conditions, such as diabetes, arteriosclerosis, and degeneration of the optic nerve and retina can be detected by such examination.

Emmetropia- Literally means harmonious vision. The condition of the eye in which vision is

accurate.

Myopia- Short vision. Nearsightedness, common name for impaired vision in which a person sees near objects clearly while distant objects appear blurred.

• It occurs when the parallel rays from distant objects fail to reach the retina and instead focus in front of it. Distant objects appear blurry to myopic people. Results from an eyeball that is too long, a lens to strong, or a cornea that is too curved.

Treatment for Myopia:

Requires concave corrective lenses that diverge the light rays before they enter the eye, so that they converge farther back.

Hyperopia- Far Vision. Farsightedness, common name for a defect in vision in which a person sees near objects with blurred vision, while distant objects appear in sharp focus.

• Occurs when parallel light rays from distant objects are focused behind the retina at least in the resting eye in which the lens is flat and the ciliary muscle is relaxed. Results from an eyeball that is too short or a lazy lens. See distant objects clearly because their ciliary muscles contract continuously to increase the light-bending power of the lens, which moves the focal point forward onto the retina. Near by objects are blurry. Hyperopic people are subject to eye strains as their endlessly contracting ciliary muscles tire from overwork.

Treatment for Hyperopia: Correction requires convex corrective

lenses that converge the light rays before they enter the eye.

AstigmatismUnequal curvatures in different parts of

the cornea or lens. Blurry images occur because points on the retina but as lines. Eyes that are myopic or hyperopic and astigmatic require a more complex correction.

In a patient with an astigmatism, the cornea or sometimes the lens of the eye is curved abnormally. This causes light rays to refract unevenly inside the eye. While some light rays focus on the retina, other light rays focus in front of or behind the retina, resulting in blurred vision.

Astigmatism

Color Blindness• This condition is congenital and

extremely rare• Defect of vision affecting the ability to

distinguish colors.• The genes regulating color vision are

on the X (female) sex chromosome, color blindness is a

sex-linked condition. It occurs exclusively in males.

Cause

• caused by a defect in the retina or in other nerve portions of the eye.• Lack of red or green receptors.

Strabismus

• An abnormal condition.• Sometimes called cross-eye, in

which the muscles of the eye prevent normal binocular vision. The cause of the defect may be paralysis or weakness of one or more of the six muscles that control eye movements, or faulty coordination of the brain and eye, or infection of nerves connecting the eye muscles. Some forms of strabismus may be corrected by the use of glasses. Surgery is sometimes employed to shorten part of the affected muscles and to reposition the eye for an improved appearance.

Presbyopia• A progressive form of farsightedness that

affects most people by their early 60s.• Presbyopia occurs with age as the lens of the

eye gradually loses its elasticity (ability to spring back into shape). This reduces the ability of the lens to focus for near vision. The first indication of presbyopia usually is difficulty with reading. Large print appears clearly, but small print is difficult to read except at arm’s length. Eventually the lenses of the eyes have little or no focusing ability.

Treatment•Simple reading eyeglasses with convex lenses . Eyeglass prescriptions may need adjusting over the course of 10 to 20 years to correct the progressive nature of the disorder.

Opthalmia Neonatorum

A baby’s eyelids become red and swollen, and pus is produced. All states legally require that all new born babies’ eyes be routinely treated with silver nitrate or antibiotics shortly after birth.