Eye strain is neither a medical term nor a diagnosis. In contrast to widespread belief, you cannot damage or strain your eyes by using them under difficult conditions, such as reading small print in poor light or wearing glasses of the wrong. Although aching and discomfort are commonly attributed to eye strain, they are often headaches that are caused by tension or fatigue of the muscles around the eye as a result of frowing or squinting.
The symptoms normally attributed to eye strain do not require treatement and normally disappear on their own, but, if the problem worses or persists, you should consult your doctor.
Colour blindness is the reduced ability to tell certain colours apart. It is due to a defect in the cones, the specialized cells in the Light-sensitive retina at the back of the eye. There are three types of cone cells, each of which is sensitive to blue, green, or red light. If one or more type of cell is faulty, colour blindness results. Colour blindness is usually inherited.
WHAT ARE THE TYPES?
The most common type of colour blindness, red-green colour blindness, affects far more males than females, and may take one of two forms. In one form, people cannot distinguish between pale reds, greens, oranges, and browns. The other form makes shades of red appear dull and indistinct. Red-green colour blindness is caused by an abnormal gene carried on the X chromosome. It mainly affects men because women have a second X chromosome that usually masks the effect of the abnormal gene. However, the abnormal gene may be passed on by women to their children.
Another, much rarer type of colour blindness makes it difficult to distinguish between blues and yellows. This form of the condition can be inherited, but because it is not linked to the X chromosome, it affects both females and males in equal numbers. Macular degeneration and other eye disorders may cause colour blindness. The toxic effects of various drugs, including chloroquine may also cause colour blindness.
WHAT MIGHT BE DONE?
Colourblindness is usually noticed during routine vision testing in childhood. It may also be detected during medical tests for jobs requiring normal colour vision, such as flying airplanes. The test is done by checking your ability to see , numbers in patterns of coloured dots.
Colour blindness rarely causes serious problems. Inherited forms are untreatable, but, if the condition is caused by eye disorders or drugs, the underlying cause can sometimes be treated.
Complete or almost complete loss of sight, usually termed blindness, affects at least 40 million people worldwide. Although most of those affected are in developing countries, about million Americans are legally blind, and many more are visually handicapped. The risk of blindness increases with age, but the condition can be present.
WHAT ARE THE CAUSES?
Blindness may be caused by disorders of the eyes, the nerves that connect the eyes to the brain, or the areas of the brain that process visual information.
In developed countries, blindness most often results from damage to the light-sensitive retina due to diabetic retinopathy or macular degeneration, elevated fluid pressure in the eye due to glaucoma, or clouding of the lens due to cataracts. In developing countries, the most common causes are the eye infection trachoma and vitamin A deficiency.
WHAT MIGHT BE DONE?
Early diagnosis can help some underlying disorders that cause blindness to be treated to preserve vision. For example, if you have glaucoma, you will be given drugs to reduce the pressure in the eye.
If you are legally blind or visually handicapped, you should check if you are eligible for certain benefits and services. You may also find that visual aids, such as magnifying glasses, are helpful when carrying out some daily tasks.
Conjunctivitis, also called pink eye, is a common condition in which the conjunctiva, the clear membrane covering the white of the eye and lining the eyelids, becomes inflamed. The affected eye becomes red and sore and may look alarming, but the condition is rarely serious. One or both of the eyes may be affected, and in some cases it begins in one eye then spreads to the other.
WHAT ARE THE CAUSES?
Conjunctivitis may be caused by a bacterial or viral infection, or it may result from an allergic reaction or irritation of the conjunctiva. For example, by smoke, pollution, or ultraviolet light.
Bacterial conjunctivitis, which is common, may be caused by any of several types of bacteria. Viral conjunctivitis can occur in epidemics caused by one of the viruses responsible for the common cold. It may also be due to the herpes simplex virus that causes cold sores. Conjunctivitis due to abacterial or viral infection can be spread by hand-by-eye contact and is usually highly contagious.
Newborn babies sometimes develop conjunctivitis. This can happen if an infection is transmitted to the baby’s eyes from the mother’s vagina during the birth. This form of conjunctivitis is usually caused by the microorganisms responsible for certain sexually transmitted diseases, including chlamydial cervicitis, gonorrhea, and genital herpes.
Allergic conjunctivitis is a common feature of hay fever and of allergy to dust, pollen, and other airborne substances. The condition may also be triggered by chemicr.ls found in eyedrops, cosmetics, or contact lens solutions. Allergic conjunctivitis often runs in families.
WHAT ARE THE SYMPTOMS?
The symptoms of conjunctivitis usually develop over a few hours and are often first experienced on waking. The symptoms generally include:
□ Redness of the white of the eye.
□ Gritty and uncomfortable sensation in the eye.
□ Swelling and itching of the eyelids.
□ Discharge that may be yellowish and thick or clear and watery.
The discharge may dry out during sleep and form crusts on the eyelashes and eyelid margins. As a result, the eyelids sometimes stick together on waking.
WHAT CAN I DO?
The symptoms of conjunctivitis can be relieved by bathing the eye with artificial tears. To avoid spreading infection, wash your hands after touching the eye and do not share towels or cloths. Once the conjunctivitis has cleared up, vision is rarely affected.
If you are susceptible to allergic conjunctivitis, avoid exposure to triggering substances. Antiallergy eyedrops can be used to ease the symptoms. If an eye becomes painful and red, you should consult your doctor to rule out the possibility of a more serious condition.
WHAT MIGHT THE DOCTOR DO?
Your doctor probably make a diagnosis from your sysmptoms. If infection is suspected, he or she may take a sample of the discharge to identify the cause.
Bacterial conjunctivitis is treated by applying antibiotic drops or ointment. In such cases, the symptoms usually clear up within 48 hours. However, the treatment should be continued for 2 to 10 days, even if the symptoms improve, to ensure the infection is eradicated. Viral conjunctivitis that occurs because of a herpes infection may be treated with eyedrops containing an antiviral drug. Although other types of viral conjunctivitis cannot be treated, their symptoms usually clear up within 2-3 weeks. Your doctor may prescribe eye-drops or oral antiallergy drugs if you have allergic conjunctivitis.