Making a spectacle

It is not enough if one gets a prescription from an ophthalmologist. One needs to know more about frames and their sizes, says M. VEERASAMY.

TODAY, people do not hesitate to wear spectacles. But there are basic things about the lens power, the frame and the lens that one should know.

Children are not aware of the symptoms of defective vision. About 250,000 school children suffer from defective vision. This affects the child's participation in classroom activities. Routine screening in schools will help detect the problem at an early stage.

Once the child is prescribed spectacles, he or she must wear it constantly. Parents and teachers should encourage them to do so because irregular use may cause increase in lens power.

Children often break the lens while at play. So, they should be given CR 39 lens (plastic lens) which is unbreakable and weightless.

If glass lenses are used, it is advisable to go in for ultra- violet protection which reduces the reflection of UV rays in the eye, which is an important cause for development of cataract.

A High Index Lens is a boon for patients who have severe myopia since it is not as thick as the normal one.

Adults too need to undergo regular tests to detect problems early. If a person around 40 years has difficulty in reading small letters, it is called presbyopia. In Greek, presbyopia means old man eye. As one ages, the lens in the eye, loses elasticity resulting in difficulty in reading.

Presbyopia can be corrected. A bifocal lens is the best choice for such patients. A bifocal has two separate portions - the upper for distant vision and the lower for reading.

Presbyopia cannot be changed if one can read without spectacles initially. The patient may feel uncomfortable and suffer from headache. A 40-year-old person who can read without glass may be myopic. Myopia needs concave lens while Presbyopia needs convex lens. So both can be neutralised without resorting to reading glass.

Initially the patient should wear the spectacles without tinted lenses, unless recommended otherwise. The tint may may cause dullness of vision which may be ascribed to optical problem.

When selecting a frame, importance should be given not only to the cosmetic aspects but also to the lens power and reason for wearing spectacles.

The frame should be strong, lightweight and must be suitable to the face. It should sit properly in the nose as well as behind the ears without causing any pressure. In most cases, the frame side does not rest properly. This is due to improper length. It should be properly blended according to the distance from the eye to the ear.

When selecting a frame, the optician should recommend a suitable one. For children large frames are better since they would not be tempted to look over it. If the patient has cylindrical vision, an oval frame is better because then the cylindrical axis cannot be turned if the lens is loose.

For distant vision, the frame should sit vertically whereas, in a bifocal, it should be slightly tilted for convenient reading. Also in the latter case, the size of the frame should not be too big or small. Since the lens is divided into two, either portion may intrude into the other.

Tips for maintenance of spectacles

* Use both hands when you wear or remove the spectacles.

* When not in use, keep it in a case.

* Wipe the lens with a soft cloth daily.

* If the screw from frame falls, do not put a pin or string. Ensure that it is replaced immediately.

* In case of a scratched lens, loose frame or broken joint, check your vision before changing according to the old prescription.

Blinking the eyes frequently helps the cornea stay wet and moist. Those who work on the computer for a long time do not blink as much as necessary. So they suffer burning sensations in the eye. Constant exposure also leads to problems like over strain, headache, disturbance in vision.

To overcome these, blink the eyes in regular intervals. Wear UV protection glass with Anti-Reflection Coating to protect the eyes from radiation.

The writer is an Ophthalmic Assistant, Primary Health Centre, T. Kallupatti.

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