Q. I am a 48-year-old man who had a cataract operation for my left eye 10 years ago.
My cataract operation did not correct my astigmatism.
Can I can have Lasik after cataract surgery to correct my astigmatism?
A. Yes, it is possible to perform Lasik on the cornea after cataract surgery in order to correct residual astigmatism.
Cataract surgery involves creating a small cut on the cornea and removing the cataractous (opaque) lens using an ultrasound probe.
An artificial intraocular lens is then inserted into the eye to replace the diseased lens. Otherwise the patient would not be able to see.
Lasik surgery and cataract surgery are two different operations with different aims.
Lasik aims to correct refractive error - myopia, hyperopia (far-sightedness) and astigmatism.
If a patient still has residual refractive error after cataract surgery, we can perform Lasik to correct the refractive error.
However, we have to assess whether your cornea is suitable for Lasik surgery.
Some of the conditions which would make it possible for you to have Lasik include having a normal cornea with no cornea disease and sufficient cornea thickness.
Lasik changes the shape or curvature of the cornea to correct astigmatism with use of an excimer laser.
An excimer laser removes tissue from the centre of the cornea to reshape it, correcting the patient's refractive error.
Another option would be to insert a second intraocular lens - in what is known as a piggy-back intraocular lens - to correct residual astigmatism. You will need to insert a special intraocular lens as part of the surgery.
There are several types of lens available. For correcting astigmatism, a toric intraocular lens is used. Ten years ago, toric lenses were new and in most cases still being evaluated for effectiveness and safety.
Normal intraocular lenses correct only cataracts and myopia or hyperopia.
Both procedures - Lasik and piggy-back intraocular lens - have their pros and cons.
Lasik is less invasive and cheaper. But it requires a cornea which is suitable for Lasik surgery.
If the patient's cornea is not suitable, then we will consider a piggy-back lens. This is a more invasive surgery as we have to insert a second lens in the eye.
Whether you can have a piggy-back lens or not depends on the state of your eye.
In general, there must be sufficient space in the eye to implant a second lens.
You should also not have other eye conditions, including glaucoma, which is a condition that causes damage to your eye's optic nerve, and low cornea endothelial cell counts.
A minimum cell density is required before we can implant an intraocular lens.
Assistant Professor Mohamad Rosman
Head and senior consultant in the refractive surgery department and Laser Vision Centre at the Singapore National Eye Centre