What is Refractive Error?

Normally, the rays of light entering the eye are brought to a precise focus on the retina – the light sensitive layer lining the back of the eye. When such a focus is not achieved, a refractive error results and vision is not clear. These imperfections in the focusing power of the eye are called refractive errors.

Fig 1: Normal eye

The common refractive errors are:

  • Myopia, or Nearsightedness
  • Hyperopia, or Farsightedness
  • Astigmatism
What are the options to correct Refractive Error?

There are several alternatives to correct your vision. Spectacles or contact lenses are the most common methods of correcting refractive errors. Refractive surgery is also an option to correct or improve your vision. These surgical procedures are used to adjust your eye’s focusing ability by reshaping the cornea, or front surface of your eye.

What is Laser vision correction surgery?

Refractive surgery is a procedure intended to reduce a person’s dependence on glasses or contact lenses by reshaping the cornea to enable light entering the eye to be properly focused onto the retina for clearer vision.

What is the type of Laser vision correction surgery available?

The most common refractive surgical procedures performed today are:

1) LASIK (Laser In-Situ Keratomileusis): It is a surgical procedure intended to reduce a person’s dependence on spectacles or contact lenses. In this procedure a thin hinged flap of cornea (the cornea is the transparent, dome-shaped window covering the front of the eye) is created and lifted to one side to access the underlying cornea (called the stroma) and remove some corneal tissue using an excimer laser. The flap is then repositioned in its original position.

2) Femto LASIK

The primary advantage for the use of femtosecond lasers in corneal refractive surgery is the improved safety over microkeratomes in the creation of the lamellar flap. Additional advantages include

  • Increased precision
  • Customization
  • Ease of surgery

Femtosecond lasers allow for customization of the flap for each patient. In addition to producing reliable flap thicknesses, the flap diameter can be selected to one-tenth of a millimetre. Femtosecond lasers are (state-of-the-art) instruments that offer more surgical precision than current manual techniques.

3) PRK (Photorefractive Keratectomy)

It was the original kind and is still sometimes used. It involves gently scraping the surface layer of the cornea and then using a laser beam to re-shape it.

Who are eligible candidates for corneal refractive surgery?
  • Be at least 18 years of age, with stable refraction for the past 1 year
  • Have healthy eyes that are free from any eye diseases or corneal abnormalities (Eg: scar, infection etc.)
  • All other Parameters in the eye being reasonably normal
  • Normal pre-operative refractive surgery safety tests
  • Should not have any connective tissue diseases (rheumatoid arthritis), autoimmune (SLE) and immunodeficiency diseases (AIDS)
  • Should not be pregnant or a nursing mother
What is the procedure and follow up?


  • Please remember that if you are a contact lens wearer you have to discontinue the use of the same at least 2 weeks before your Lasik consultation (As the contact lens can alter the shape of the cornea). During this period you can wear spectacles
  • As a part of Comprehensive Eye examination for Lasik, we dilate your pupils for retinal evaluation, since we dilate the pupils, we request you to have someone accompanying you to drive you back as you will not be able to self-drive. This is because the vision is slightly fuzzy for an hour or two. Hence avoid going back to office work after the evaluation is completed
  • The primary objective of this consultation is to determine whether you are a suitable candidate for laser vision correction (LASIK), and if so, which procedure is most appropriate for you
  • The treatments we apply are customized for the person’s needs, age and glass power of the eye to give a precise result
  • Lasik information brochure giving details of our treatment procedures is available at the LASIK reception desk
  • Your eyes will be dilated with eye drops. You will be asked to keep your eyes closed for a brief period to aid the dilation
  • During the consultation with your Refractive Surgeon, the pros and cons of different types of the refractive procedure will be discussed and the choice of procedure will be decided based on the tests
  • You should plan on being at the LASIK Wing approximately 1 to 2 hours prior on the day of your procedure. Please be accompanied by an attendant. Do not drive by yourself after your treatment
  • When you arrive at our LASIK Center, on the day of your procedure, you will complete a brief check-in process and if required tests may be repeated. You will be asked to sign your consent forms before the procedure. We want you to be as comfortable and relaxed as possible. Our attentive staff will be on hand to cater to your needs and to keep you informed and comfortable through every step of the process. You will also meet with our refractive surgeon before your procedure
What to expect during the procedure?
  • Before the procedure begins, numbing eye drops will be applied to prevent any discomfort during the procedure
  • Your eyes will be positioned under the laser and an instrument called the lid speculum will be used to keep the eyelids open
  • Based on the type of refractive procedure the surgeon will create the flap or the bed for the laser. After creating the flap, the surgeon will then adjust the eyes to align with the laser
  • You will be asked to look at a green target light for a short while as the laser sends pulses of light to your cornea
  • You will also hear a sound while the laser is operating
  • Lasik will be performed on each eye separately starting with the right eye followed by the left eye in the same sitting
Immediately after the procedure:
  • Once the procedure is done, the surgeon will take a look at your eyes on the slit lamp
  • Post LASIK instructions will be given by our LASIK OT staff
  • After resting for a short period you will be able to go home
Follow up:

Post LASIK. the patient will be reviewed on the day following the procedure. We would ideally prefer to review the candidate after the 1st, 3rd and 6th month of the procedure.

Post-Refractive surgery instruction:
  • Mild / Moderate tearing is expected after the procedure
  • A sense of foreign body presence and irritation are common
  • Small red spots on the white surface of the eye – occasionally appear
  • Sensitivity to bright light / corneal Haze – on the day of the procedure
  • Instillation of eye drops as per the prescriptions.
  • Cleaning of the lid margin gently with sterile tissue from the following day
  • Have normal food / no restrictions.
  • Can have below neck bath from the following day
  • Blink your eyes gently & frequently on the day of treatment
  • Can read, watch TV and use a computer, a couple of days after the treatment
  • Use sunglasses when you go out and plastic shield while sleeping for 2 weeks
  • Do not expose your eyes to dust/pollution
  • Do not touch or rub your eyes
  • Do not take a head bath or splash water into the eye and face for 2 weeks
  • Do not keep your eyes open for a long duration
  • Do not clean the eye on the day of your treatment
  • Do not swim for one month
  • Do not use eye cosmetic /eyeliner for 2 months
  • Avoid exercises for 1 week
  • Avoid self-driving for 1 week
What are the Side effects?
  • There is a possibility that you may still need spectacles or contact lenses to attain good vision following the treatment.
  • Patients may have light sensitivity, halos, dryness and glare after the refractive surgery.
  • Very rarely severe complications during or after corneal refractive surgeries (eg. flap problems, infections, etc.)
What are the Alternatives?

There are some alternatives to correct your vision. Spectacles or contact lenses are the most common methods of correcting refractive errors. The other option to correct your vision is called ICL (implantable contact Lens), When laser refractive surgery is contraindicated, ICL is a kind of lens which is implanted into the eye and does not require frequent removal like a normal contact lens.