About
Your eye usually works like a perfectly focused camera, where the focusing mechanism of the cornea (the clear window at the front of the eye) and lens brings light to a focus on the retina (the camera film at the back of your eye).
Sometimes light may not be focused properly due to problems with the structure of your eye. These include short sightedness, far sightedness and astigmatism. These are collectively known as refractive errors.
The branch of ophthalmology dealing with surgery to correct refractive errors is known as “refractive surgery”.
Laser vision correction is a type of surgery that improves the focusing power of the eye where an excimer laser (cool temperature laser) is used to improve the focusing power of your eye. This is done by using the laser to change the curvature of the cornea (the clear window at the front of your eye).
Conditions associated:
- Myopia (shortsightedness, or rather poor vision for distance and good vision for close up)
- Hyperopia (farsightedness – poor vision for both distance and near)
- Astigmatism (doubling of vision – poor vision due to ghosting or doubling of images)
- Presbyopia (poor near vision due to the body’s natural aging process)
Symptoms:
Vision which becomes clear upon using spectacle or contact lenses is a refractive error.
Examination / diagnosis:
An error of refraction is usually diagnosed after testing by an optometrist or an Ophthalmologist.
Investigations needed:
Tests which are needed to determine if you are a good candidate for vision correction surgery include:
- Slit lamp biomicrosopy: Corneal examination at the slit lamp by an Ophthalmologist.
- Refraction:Measurement of the refractive state of the eye by an Optometrist or an Ophthalmologist.
- Corneal topography: A map of the cornea is taken to look for astigmatism and to rule out conditions like keratoconus which may stop you having vision correction surgery.
- Dilated retinal exam: Drops are put into your eyes to dilate your pupils and allow your Ophthalmologist to look at your retina in greater detail. Depending on your retinal status, you may require treatment prior to having vision correction surgery, or less commonly, you may not be able to have surgery.
Treatment:
Laser vision correction surgery can be divided into two general types (i) surface laser treatment and (ii) LASIK.
1. Surface laser treatment is a form of laser surgery that does not involve any cutting. In this, an excimer laser is applied directly to the cornea to change its shape. The main advantage of surface treatments is its excellent safety profile due to it being a no-cutting technique. The main disadvantage is that of a delayed (1 week) recovery period and stinging and watering after surgery. there are several techniques used for surface laser:
- PRK (photorefractive keratectomy): PRK is mainly used for correcting low prescriptions with a healing process lasting several months. The surgeon needs to remove the outer layer of the cornea (called the epithelial layers) mechanically or Alcohol-assisted.
- LASEK (laser epithelial keratomileusis): LASEK is similar to PRK using the machine to remove the outer layer of the cornea.
- TransPRK: This technique is an all laser, no touch and non-invasive vision correction procedure which does not require the eye surgeon to cut a corneal flap.
2. LASIK is a technique where a thin flap is cut on the surface of the cornea. This flap is then lifted up and the excimer laser is applied underneath the flap. The flap is then put back in place. The main advantages of LASIK are a rapid recovery along with increased levels of comfort. The LASIK flap can be created with either:
- A mechanical blade (microkeratome LASIK)
- A femtosecond laser (intraLASE). Flap creation with a femtosecond laser is now the standard of care and offers enhanced levels of predictability, surgical precision and patient safety.
