Refractive correction

Spectacle numbers are usually one out of the following four types-

a. Myopia, minus number - The eye is longer than its normal length of 24 mm. The image of an object therefore forms little ahead of the retina instead of being formed on the retina. The object, as a result is not seen clearly. This is adjusted by using a concave lens, i.e. spectacles with minus number.

b. Hypermetropia, plus number - the length of the eye in this case is shorter than the normal, and hence the object is not seen clearly. This is corrected by using convex lenses, i.e. spectacles with positive number.

c. Astigmatism - This requires use of cylindrical numbered glasses, with either plus or minus number

d. Presbiopia - After the age of 35 - 40 years, the ability to see objects close by diminishes due to the reduction of the refractive index of the natural lens. This is corrected by adding a plus number (convex lens) glass (or a smaller minus number if the patient is already myopic).

The symptoms that may require the patient needing use of spectacles are - reduction of vision, not able to see properly, headache, redness of eyes, aching of eyes, watering of eyes, the letters getting mixed while reading, tiredness while reading etc. In case of children, they may not be able to read the board in the class, they may develop problems in studies and lag behind the class, and may squint a little.

In case of presbiopia, the patient may have to read a book by holding it a longer distance. If such patient is myopic and using minus numbered specs, they will probably see nearer objects better without their glasses. In all such cases it is necessary to contact your eye surgeon immediately and follow the advice.

Sometimes, some elderly people suddenly feel that their near vision has improved and the spectacle number may have reduced. This may be the beginning of cataract, and it is necessary to check the eyes immediately. Continuous reading, or studying will not damage the eyes or cause the person to require spectacles. The reading, however, has to be done in good light, with the book at the correct distance. Many illiterate people also develop high numbers for that matter, without reading anything.

It is a false belief that continuous wearing of spectacles help to reduce the number. Spectacles is an aid and not the treatment. If the number is low plus or minus , the eye may not develop any other major problem. But if the power is high plus , the patient may develop glaucoma of a specific type. If the number is high on the minus side, the retina becomes delicate and can lead to its detachment which is a serious problem. Such patients therefore should get their eyes regularly check ed, so that if there is a problem, it can be diagnosed and treated early. Contact lenses can be used in most cases that require spectacles. Please follow instructions meticulously given by your eye surgeon. While contact lenses offer a good solution, LASIK is a great option to relieve oneself from the burden of spectacles.

Conjunctivitis

Sometimes, either due to reduced resistance or in an epidemic, the conjunctiva of the eye is infected, and the disease is called conjunctivitis. The eyes typically get red, swell, and some discharge comes through the eyes. Patient feels like scratching or rubbing the eyes.

This infection can be bacterial or viral and patient should consult an eye surgeon. If treatment is delayed, or if wrong treatment is administered, the cornea can get infected, thus the vision gets affected. Many times, people try to use drops on the basis of their own belief or on the basis of an advice from a person who is not an expert in this field. Many instances people use steroid eye drops. The steroids typically suppress the symptoms and give a quick but temporary relief. This may result in reduction in resistance and prolong the illness compounding its ill effects. When there is an epidemic, avoid crowded places, swimming pools, and avoid contact of people with infection, as this is a contagious disease. The patients should use goggles and avoid crowded and the above place for the same reasons. Avoid sharing towels, soaps during the epidemic, and apply ice if infected.

Amblyopia (Lazy Eye)

Amblyopia is a condition in which the vision gets blunted in one eye or both eyes. It is commonly seen in young children who have the inability to use the eye during the early age, up to 6 years.

Common cause of this is uncorrected spectacle number, and is commonly unilateral. The child does not realise that he has defective vision in one eye as the other eye has relatively good vision. The good eye competes and dominates with the weak eye. The weaker eye, as a result, gives up the function of seeing and becomes dull. The vision centre in the brain for that eye becomes less active. This problem occurs only if the unilateral number is too high and it remains uncorrected for a very long time. Thus the lazy eye, even after putting in proper number glasses, or after removing any other treatable cause of lower vision, is unable to see. This needs special treatment by periodical occlusion of better eye under supervision. The treatment is difficult, but if started early enough and done meticulously gives good results.

This condition can be prevented by periodical check up of eyes of the children even if there is no apparent complaint, as they may not realise the problem, and only early treatment can give better improvement in vision.

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