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Refractive Errors

By : on : July 16, 2019 comments : (Comments Off on Refractive Errors)

Refractive Errors

As we grow older, our bodies undergo changes and eyes are no exception. Diminishing vision is one of the major handicap as we age. Many people don’t seek medical attention because of negligence and ignorance. Some take it as a part of aging and resign themselves to fate. This is unfortunate since most of the eye problems can be prevented or corrected if detected in time. Periodic eye examinations are an important part of good preventive eye care.

When we look at any object, light rays pass from the object through the transparent cornea and the clear lens to strike the retina and form an image. The retina then relays the image to the brain through a set of wires called as optic nerve.


When light rays from a distant object do not come to a focus on the retina, the image of the object appears blurred and the condition is called ammetropia.

When the size of the eyeball is longer than normal, these light rays are focused in front of the retina. This is myopia or short sightedness. This can be corrected by concave lenses as spectacles or contact lenses.
When the size of the eyeball is shorter than normal, these light rays are focused behind the retina. This is hypermetropia or long sightedness. This can be corrected by convex lenses as spectacle or contact lenses.
a normal eye has spherical cornea in all its meridians. When the cornea is steeper or flatter in any of its axii, it gives rise to Astigmatism, This is corrected by cylindrical lenses as spectacles or toric contact lenses
The normal eye works like an autofocus camera which can focus for distance and near. This is achieved by change of shape of the lens in the eye directing the light rays onto the retina (back of the eye).But with age, the lens hardens and cannot change its shape as easily making it difficult to focus on small and close objects. Presbyopia often starts around the age of 40 years and slowly worsens until the age of 60 years. This is easily treated with bifocal or multi-focal (progressive) glasses, mono-focal & bifocal contact lense conductive keratoplasty. Several new procedures are being tried the world over but results are unpredictable.


If you’re looking into LASIK vision correction, it’s probably because you don’t want to wear glasses or contact lenses any more.

Sure, glasses can be a fashion statement, but they can also get in the way. They’re a hassle during your favorite activities, and they block your beautiful eyes from the world. If they’re not

getting smudged, they’re getting knocked off.

Contacts too have got their own set of problems. All the supplies you have to buy, the constant cleaning procedures and checkups, lost lenses, allergies and injections.

Now, imagine life without contacts and glasses – the simplicity, the freedom to do what you want without worry. That’s what LASIK surgery can give you.


Changing the way you see the world.

You’ve had vision problems for most, maybe all of your life? So, you’ve paid your dues, It’s time for a brand new outlook! But, before you dive in, you need to know the basics about your

eyes, the condition that affects them, and how laser vision correction gets the job done.


Laser assisted in situ keratomileusis or LASIK is an outpatient surgical procedure used to treat myopia, hyperopia and astigmatism. With micro surgical equipments and laser, LASIK reduces your dependence on glasses and contact lenses.

The ideal candidate for LASIK is over 18 years of age, not pregnant or nursing and free of any eye disease and a stable refractive error of 1 year.

Perfect refraction, retinal evaluation, corneal topography, and pachymetry are done to determine the suitability and safety of the procedure in a candidate.

HOW IS LASIK (Conventional Procedure) DONE?

It is an outpatient surgical procedure. The eye is numbed with topical anesthetic eye drops. An eye lid holder is placed between the eyelids to keep them open and prevent the patient from blinking, light disappears for some time. An automated micro keratome attached to the suction ring moves across the cornea to make horizontal cut, creating a hinged flap. The micro keratome and the suction ring is now removed and the corneal flap is lifted and folded back. The laser customized to the eye is focused and delivered. The laser sculpts the exposed corneal tissue and thus reshapes the cornea. The flap is now placed back and it sticks back on its own to reshaped cornea in a few minutes. This entire procedure takes about 7-8 minutes per eye.

The patient is sent back home with a pair of protective glasses


It is normal to have irritation, redness, watering and burning in the eyes. It is best to rest the eyes by taking a short nap. Eye drops are prescribed to make the patient comfortable.


LASIK (Laser Assisted in Situ Keratomileusis) is a surgical procedure which involves reshaping your cornea with laser to help improve eye sight. By creating a “door” on the surface of your eye, your surgeon can easily correct vision problems; this “door” is then closed, and your eyes quickly heal on their own. Although LASIK can provide great benefits, it’s still a surgical procedure and also carries some risks. The procedure is called “Blade-less LASIK” or Femto-LASIK.


Femto-LASIK is a ‘bladeless procedure’ where only laser systems are used to cut the flap. It is thus a much more precise, predictable and safe method for creating the corneal flap as compared to the conventional microkeratome (‘blade’) flaps. In addition to the increased safely during surgery, Femto-LASIK flaps have vertical edges which ensure quicker and stronger healing as compared to microkeratome flaps which have sloping edges. This translates into a much less risk of displacement of the flaps in case of inadvertent injury to the eye. Quality of vision (i.e crispness, contrast etc) is also superior with Femko-LASIK because of the uniformly thick flaps and the smooth corneal bed.


It is important to have realistic expectations. Over 90% of people achieve 6/6 to 6/9 vision without glasses or contact lenses. If refractive error is under corrected the result can be fine tuned by a second surgery called enhancement. People beyond 40 years of age can also undergo LASIK for distance vision but will need glasses for reading after surgery.

LASIK is the most popular form of refractive surgery called enhancement. People beyond 40 years of age can also undergo LASIK for distance vision but will need glasses for reading after surgery.

LASIK is the most popular form of refractive surgery for decreasing dependence on glasses or contact lenses.



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