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Refractive Errors
Overview:
In normal vision, light rays from an object focus on the retina (emmetropia). Alternatively, in the presence of a refractive error, the light rays get focused in front or behind the retina causing blurred vision. Under normal conditions, as the eyeball grows in size from infancy to adulthood, there will be a corresponding change in curvature of cornea and the lens enabling the eye to remain emmetropic, at all ages. When one of these fails to happen, refractive error occurs.
Types:
- Myopia (Nearsightedness)
- Hypermetropia (Farsightedness)
- Astigmatism
- Presbyopia
Symptoms:
- Trouble work on computer
- Tired Eyes
- Double vision
- Hazy vision
- Squinting
- Glares
- Halow in bright lights
- Headaches
- Trouble in reading
- Eye strain
- Sore
Causes:
- Problems with the shape of the cornea (the clear external layer of the eye)
- Eyeball length (when the eyeball develops as well long or as well short)
- Aging of the focal point (an internal portion of the eye that's regularly clear and makes a difference in the eye center)
Diagnosis:
What is myopia (Nearsightedness):
If you have myopia you can clearly see close objects, but distant objects are blurry. Myopia is caused by the eyeball being too long. Myopia occurs in different degrees from minimal to extreme. The more myopic you are the blurrier your vision is at a distance and objects will have to be closer to you so you can see them clearly. Myopes squeeze their eyes while trying to see distant objects, hold books close to their face while reading.
What is hyperopia (farsightedness):
Hyperopia occurs when the eyeball is too short for the light rays to focus clearly on the retina. Hyperopes find difficulty in reading, writing and looking at both near and distant objects. They have eye strain while trying to read for long hours; may even have squint (strabismus).
What is astigmatism:
If you have an astigmatism, the surface of the eye (cornea) is not perfectly round, rather it is more oval and doesn’t allow the eye to focus clearly. The cornea is very important in helping the eye focus light rays on the retina. Astigmatism rarely occurs alone. It usually accompanies myopia or hyperopia. Children with these conditions may also have pain, watering or burning sensation in eyes, rub their eyes or blink frequently, because of eye strain which they experience all the time, headache intensified in evening, recurrent swellings in the eye lids.
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What is presbyopia:
If you have presbyopia, you have the loss of the ability to focus up close that occurs as you age. Most people are between 40 and 50 years old when they realize for the first time that they can’t read objects close to them. The letters of the phonebook are “too small” or you have to hold the newspaper farther away from your eye to see it clearly. At the same time your ability to focus on objects that are far away remains normal.
What is the Treatment:
Corrective spectacle is the best option available. Though children may initially refuse to accept glasses, they will become fond of them once they realize they can see better with them on. The power of the glasses may change depending on the growth of the eyeball. An eye check-up and change of glasses if necessary, has to be done once in 6 months for children under 5 years of age and once a year thereafter. Making a child wear glasses regularly is the duty and responsibility of the parents. Failure to wear glasses in childhood when needed will retard the development of vision in that eye. Children older than 10 years can use contact lenses if they don’t want spectacles. Those over 20 years of age with stable power also have the option of LASIK, a laser refractive surgery apart from contact lenses. Failure to correct the refractive errors and eventual low vision may hamper the academic activities of the child. So an ophthalmic consultation is essential in children, especially with symptoms of refractive errors. Finally, there is no relationship between nutritional deficiency and the occurrence of refractive error. So loading these children with Vitamin A will not help them. Sometimes this may lead to other complications.
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