Laser vision correction has opened up new horizons in the correction of myopia (shortsightedness), hyperopia (far-sightedness) and astigmatism. Advanced procedures now make it possible for majority of people with refractive errors to achieve clear vision without the use of spectacles or contact lenses.
The two current and widely used laser vision correction techniques in Singapore and worldwide are Photorefractive Keratectomy (PRK) and Laser Assisted In-situ Keratomileusis (LASIK). Both techniques utilise the accuracy and precision of the computer-controlled excimer laser to change the shape of the cornea to improve the way light is focused by the eye, correcting myopia, hyperopia and astigmatism.
The excimer laser is a unique type of laser that neither burns nor cuts tissue. Instead, it gently breaks the molecular bonds between cells so that controlled amount of tissue can be vaporized away, one microscopic layer at a time. Each pulse of excimer laser removes 0.25 microns of tissue (a human hair is about 70 microns thick).
Photorefractive Keratectomy (PRK)
In PRK, only the most superficial layer of the cornea, called the epithelium, is removed. The excimer laser is then used to sculpt the shape of the cornea, changing its curvature and therefore correcting the refractive error.
Epi-lasik is an advanced form of surface ablation. A special instrument is used to fashion the epithelium, and the excimer laser is applied to the cornea thereafter. The epithelium is then folded back in place. Epi-lasik is especially useful for patients with thin corneas.
Laser Assisted In-Situ Keratomileusis (LASIK)
LASIK is effective for low to high myopia of up to 1500 degrees and astigmatism of up to 600 degrees. LASIK is also effective for low to moderate hyperopia.
A thin flap of corneal tissue is created with the use of a specialised instrument called microkeratome. The corneal flap is folded to the side, and the excimer laser is applied to reshape the cornea underneath the flap.
The corneal flap is then folded back. After LASIK, patient's vision usually returns within a day, and there is less post-operative discomfort and less risk of scarring compared to PRK.
Customised Wavefront LASIK
Developed more recently than standard LASIK, it customizes the exact laser pattern for each individual's eye. Everyone has unique minor optical imperfections. Wavefront technology detects these imperfections and customises the exact laser pattern to treat them in addition to treating regular myopia or astigmatisem.
Aspheric LASIK is a very new technology. Unlike conventional LASIK, where the centre part of the corneal bed is flattened, at the end of the procedure, the new aspheric method is specially designed to retain the original curved shape of the cornea. This is an improvement over standard LASIK and has been proven to give better success rates, sharper vision and less glare and haloes at night.
INTRALASE® – The All-Laser Blade-Free Approach to LASIK
There are two important steps to LASIK eye surgery. First, your doctor creates a micro-thin corneal flap. Next, your doctor folds open the flap so that an excimer laser can be applied.
Careful execution of the first step is important for faster healing, greater comfort and better vision. The INTRALASE® laser is a more precise and safer method for creating the flap . It makes LASIK surgery better by replacing your doctor's hand-held microkerotome blade with a computer-guided laser that delivers micron-level accuracy. The IntraLase femtosecond laser is the first bladeless laser technology for performing the first step of LASIK and the most accurate technology for corneal flap creation available today. The laser uses an infrared beam of light to precisely separate tissue through a process called photodisruption.
With IntraLase, your doctor can create a corneal flap of exact diameter, depth, hinge location, centration, and overall architecture. This is more accurate and more precise than a hand-held blade.
Are you a good candidate for laser vision correction?
Laser vision correction is intended for people who want to minimise their dependence on glasses or contact lenses. To be a suitable candidate, you need to satisfy the following criteria:
- Be at least 21 years of age;
- Have had stable vision without significant increase in spectacle prescription for the past one year;
- Have eyes free from complicating injuries or certain diseases;
- Must not be pregnant.
Your doctor can determine your suitability for laser vision correction after a comprehensive consultation and examination.
The surgery experience
Before the procedure, each candidate undergoes a comprehensive series of eye examinations and tests which can be done in half a day.
PRK, Epi-lasik or LASIK is performed as an outpatient procedure. No injections are needed. Patients remain awake and the procedure is carried out using anaesthetic eyedrops. The procedure takes about 10 minutes.
Most patients after LASIK report almost normal vision the next day and can resume normal activities within the first few days. Eye drops are necessary for a period of time after the procedure. It is important that patients comply with post-operative instructions and attend all post-surgery appointments.
- 95% of people who have had laser vision correction can pass a standard driver's license examination that requires a visual acuity of at least 6/12 without glasses or contact lenses.
- Additional enhancement laser procedures may be required to achieve your desired results.
- The goal of laser vision correction is to reduce your dependency on spectacles or contact lenses. Each candidate should remember that a specific end result cannot always be guaranteed.
- Laser vision correction does not correct an ageing process called presbyopia. Hence, reading glasses may still be necessary for middle-aged and older adults.