Our eyes are designed to receive light & convert it into signals that are sent to the brain, which makes us see. Any change in the length of the eyeball causes refractive errors like shortsightedness (myopia), long-sightedness (hypermetropia) and astigmatism.
- Myopia is by far the most common refractive error we see where people cannot see distant things clearly. It is commonly called short-sightedness.
- Hypermetropia is the next most common error & is known as longsightedness.
- Astigmatism can be myopic or hypermetropic.
- At around 40 years of age, the majority of us face difficulty in reading small print. This is called presbyopia.
All the above refractive errors can occur alone or in combinations. Refractive errors, especially myopia, are on the rise in the last two decades in our country. Nearly 20 per cent of our children have refractive errors nowadays, compared to five per cent two decades earlier. The steep rise is attributed to lack 48 of physical activity, decreased exposure to sunlight and marked increase in exposure to TV, computer games, video games and mobile games. Excessive near work puts strain on the eyeballs and on the eye muscles, which elongates the eyeballs, leading to myopia. Regular eye check-ups detect refractive errors early. Children should be taken for an eye check-up as soon as they learn alphabets and numbers. Whenever parents notice that the child is unable to see distant things, squeezes the eyes to see, keeps books or toys very close to the eyes or watches television from close quarters, it is time for the child to undergo an eye check-up. Nowadays technology is available to detect defects in the eyesight even in a one year old child or less. Refractive errors in children should be corrected as soon as detected, otherwise they might lead to lazy eye syndrome or squint.
Refractive errors are usually corrected with lenses – concave (negative) lenses for myopes, convex (positive) for hypermetropes, and cylindrical lenses for astigmatism. Presbyopia is corrected with plus lenses. Those who have error for both distant and near vision, which is common after 40 years of age, need bifocals or progressive lenses. Bifocal lenses give good distant and near vision only, whereas progressive lenses are useful for distant, near and intermediate vision, especially for those who work on computers and laptops. Glass lenses should be avoided in children as they may break during injury and cause injury to the eyeballs. Fibre or plastic lenses are preferred for children. Those who work outdoors should preferably use transitions, i.e., PhotoGray, which work like cooling glasses (shades) in bright sunlight. Those who do not wish to wear glasses can try contact lenses. Bifocal contact lenses for presbyopia are not available. Contact lenses can be worn at any age, provided that children and parents are aware of the dos and don’ts.
Dos and don’ts for contact lenses
Contact lenses can be used daily for about eight to 12 hours. Don’t use contacts when at home and on Sundays.Those who need to use contacts for long hours can opt for disposable contact lenses which are available in various types – daily, weekly, fortnightly or monthly disposable contact lenses. Never sleep with contact lenses on, as it may lead to threatening infections of the eye leading to loss of vision.
Laser refractive surgery
Various types of laser surgeries (PRK, LASIK, E-LASIK) are available to treat myopia, hypermetropia and astigmatism. Refractive laser surgery is done in patients above the age of 18, and refractive error should be stable for one year. Those wearing contact lenses should remove contact lenses for atleast one week before evaluation for laser surgery. For those who are not fit for LASIK and are very high myopes and hypermetropes, there is a procedure called ICL, wherein an Implantable Contact Lens is placed in the eye through a micro incision – a procedure done routinely.