WHAT CAN BE CORRECTED ?

If you are under 45 years of age and you wear correction for myopia (short sightedness), hyperopia (long sightedness) or astigmatism then you can most likely you can have a correction to eliminate your glasses or contact lenses. The strength of your glasses will govern which modality is best

If your problems is none of the above but instead you are just presbyopic (older than 45 and can’t read anymore) then read the sections on presbyopia and monovision as your problem is different and needs a different approach 

BASIC PRINCIPLES OF VISION CORRECTION

There are essential two ways to correct the vision problems mentioned above.

1. Change the surface of the cornea using a laser technique such as Lasik or PRK
2. Change the lens in the eye (Clear lens exchange)
3. Implant a new lens in the eye, in front of your existing lens (Implantable Collamer Lens)

As a general principle, corneal procedures are generally performed in younger patients and lens procedures in older patients.Implantable Collamer lenses are generally used in people requiring high corrections or where the corneal surface is abnormal

LASIK vs PRK vs LENS EXCHANGE vs PHAKIC LENS IMPLANT (ICL)

In LASIK, a corneal flap is created. Traditionally with a microkeratome (knife) but nowadays with a femtosecond laser.

In PRK, the surface epithelium is removed and a laser applied directly to the corneal stroma. Therefore there is no flap creation and therefore it leaves behind a thicker base.
LASIK has largely replaced PRK because it is much more comfortable with virtually no discomfort whatsoever and visual recovery is a matter of days versus weeks. The end results however are really no different and in fact there has been a resurgence of PRK in recent years in certain individuals.
LASIK would be the procedure of choice for younger people with shortsightedness up to about 9 diopters and longsightedness up to about 3 diopters. Astigmatism can be corrected up to about 4 diopters.

For people whose refractive error is out of the range of LASIK, a lens can instead be implanted within the eye. This lens is called an implantable Collamer Lens or sometimes also called, a phakic intraocular lens. It sits behind the iris. It is in a sense, a contact lens within the eye. The Visian implantable Collamer lens (ICL) is an example of one that sits behind the iris and in front of the natural lens.

We offer the Visian ICL for patients out of range of Lasik.
In older patients, usually late forties or beyond, refractive lens exchange is usually a better option. In this procedure, the eye’s natural lens is removed and replaced by an artificial one. This is usually done because firstly accommodation (ability to focus) is largely gone by this age and secondly because the age for cataract is arriving so it avoids a second operation for cataract later on. Also, at an older age, LASIK is less predictable.

This video below is a good overview of the various options.

By reading this section you will gain an understanding of what LASIK is

WHAT IS LASIK ?

LASIK stands for Laser In Situ Keratomileusis. It is a method of correcting vision using a laser. It can correct short & long sightedness as well as astigmatism.

LASIK HAS TWO PARTS

A LASIK procedure has essentially two parts. 1. Creating a flap 2.Vision correction

FIRST PART – CREATING THE FLAP

The first is creating a corneal flap, usually 100-120 microns thick. This is usually done using a femtosecond laser called an “Intralase” Prior to Intralase, flaps were created using a microkeratome. Some surgeons still use a microkeratome, which is a motorized blade that shaves the surface of the cornea. Microkeratomes suffer from the fact that they are mechanical and thus can jam or fail. The blades can become blunt and produce uneven cuts. Corneal flaps created by microkeratomes behave differently to those produced by femtosecond lasers. Firstly they are easer to lift but they are also easier to loose. Precise alignment at the end of the procedure is more difficult and usually requires that alignment marks be placed on the cornea. Free flaps are more likely to occur with mechanical keratomes than with laser ones. This is where the flap is completely cut for 360 degrees. Normally a flap is hinged at one end either vertically or horizontally. Further, an incomplete flap can occur if the patient has a deep set eye and the microkeratome isn’t quite placed correctly or there is poor suction. Femtosecond created flaps rarely have these problems.

SECOND PART – VISION CORRECTION

The second part is the actual correction itself in which a second laser is used to sculpt the cornea into a new shape to correct vision.

Once the flap has been created using either a microkeratome or Intralase, the vision correction part of the procedure takes place.

The patient  is moved under the second laser for the vision correction part of the procedure.

In this part the flap is lifted, the excimer laser is applied to the corneal base which corrects the refractive error and then the flap is put back.

At the end of the procedure, the flap is given some minutes to ‘adhere’ to the corneal stroma. The endothelial cells on the inner surface of the corneal pump fluid out of the cornea and help the flap to stick. Usually the person will then sit outside for a short period before being examined under a microscope to ensure that the flaps are well aligned and without problem. An clear eyeshield is then applied, essentially to prevent eye rubbing during sleep. Antibiotic and anti-inflammatory drops are commenced later that evening and the person is reviewed the next day