Dr Leonard Ang
Senior Consultant Ophthalmologist
Lang Eye Centre
Refractive errors, such myopia and presbyopia (‘lao hua’) are common causes of poor vision. Refractive surgery allows all forms of refractive errors to be corrected and individuals can achieve clear vision without the need for spectacles with a high level of precision and safety.
REFRACTIVE SURGERY FOR CORRECTING REFRACTIVE ERRORS
Refractive surgery refers to the surgical correction of the refractive errors of the eye. All forms of refractive errors can be corrected including myopia (short-sightedness), hyperopia (far-sightedness), astigmatism and presbyopia (‘lao hua’).
Millions of people around the world have undergone refractive surgery to reduce or eliminate their need to use spectacles or contact lenses.
The most common refractive surgical procedures performed in the world today are LASIK surgery, implantable contact lens surgery and cataract surgery.
1 / LASIK
LASIK, which stands for Laser In Situ Keratomileusis, is a laser procedure that corrects the refractive errors of the eye by reshaping the cornea. It has gained tremendous popularity and is currently the most commonly performed refractive surgery because it is low risk, has a high success rate and rapid visual recovery.
It consists of 2 stages. The first stage is the creation of a corneal flap. This can be done with a motorised blade system, called a microkeratome, or the use of a laser called the femtosecond (FS) laser. The FS laser allows the corneal flap to be created without the use of a blade (bladeles).
The second stage involves partially lifting the corneal flap and using an excimer laser to reshape the cornea tissue underneath the flap. The flap is returned to its original position and the entire surgery is completed in approximately 4 minutes per eye. The whole procedure is essentially painless. The vision recovery is fast and most people can return to work 1 to 2 days after surgery.
Modern LASIK machines can achieve good results. iLASIK is a laser treatment that combines precision, customisation and safety. iLASIK is a completely customised, blade-free, all-laser combination of the IntraLase bladeless flap creation and the VISX Advanced CustomVue Wavefront-guided laser treatment. It is approved for use in NASA astronauts and US top-gun fighter pilots.
Safe and proven bladeless LASIK surgery
The IntraLase FS laser has demonstrated safety, effectiveness and precision in the corneal flap creation. The 5th generation iFS 150Hz Advanced FS Laser, is faster and more precise, enabling LASIK surgeons to attain a high degree of surgical control and customisation. The laser beam is focused just beneath the corneal surface and creates a uniform layer of microscopic bubbles that interconnect to create a corneal flap.
The recovery is faster and there are fewer LASIK flap-related complications compared to the blade method. The flap diameter, depth, edge angle and morphology can all be programmed and customised to suit each person’s cornea aiming to achieve a good visual outcome.
Wavefront-guided LASIK – Customised laser eye treatment
Standard LASIK corrects a person’s basic refractive errors such as myopia and astigmatism while Wavefront-guided LASIK is a customised laser treatment that not only corrects refractive errors, but also unique imperfections of the eye (higher order aberrations) that cannot be corrected with glasses, contact lenses or Standard LASIK.
The Wavefront-guided treatment uses the iDesign Wavefront analyser, which is a diagnostic machine that can measure all the refractive errors of the eye and higher order aberrations. The information captured by the iDesign is then transferred to the excimer laser to create an individualised treatment aiming to give a better quality of vision and lowers the incidence of seeing haloes and starburst at night post-surgery.
2 / IMPLANTABLE CONTACT LENS OR PHAKIC INTRAOCULAR LENS
Another safe and effective method of correcting vision is the implantation of a phakic intraocular lens. The surgery involves inserting an artificial lens into the eye. The most widely used phakic intraocular lens is the Visian implantable collamer lens, or more commonly known as the implantable contact lens (ICL). The lens is completely biocompatible as it is made from collamer, which is a polymer with collagen. Once implanted, the lens is invisible to the naked eye and most people can resume their normal activities pretty quickly.
ICL can correct a wide range of refractive errors of up to 2,000 degrees of short-sightedness and 600 degrees of astigmatism. It is particularly suitable for those with high refractive errors (i.e. those above 900 degrees) or those who are not suitable for LASIK due to very thin corneas. For those with very high degrees, ICL surgery can provide high-definition vision in the day and night, with less night vision phenomena (e.g. haloes and starbursts) compared to LASIK.
The surgery is simple, painless and takes about 10 minutes. The lens is inserted through a small incision at the edge of the cornea and is placed behind the iris and in front of the natural crystalline lens. The wound heals on its own without stitches. Recovery after ICL surgery is relatively fast with minimal discomfort. Most people are able to return to work or school within a few days post-surgery.
This procedure does not cause any alteration to the shape and structure of your cornea, thus providing an advantage for those with high myopia and thin corneas. The surgery does not cause dry eye. It is reversible and the lens can be removed if necessary.
3 / REFRACTIVE CATARACT SURGERY
The other common method of correcting one’s vision is in the form of cataract surgery. Cataract is a condition in which the natural clear lens of the eye becomes cloudy and reduces the amount of light entering the eye. This results in a gradual progressive deterioration of vision.
Cataract is the commonest cause of blindness in the world. Annually, at least 25 million eyes go blind due to cataract. In Singapore, more than 30% of people above 45 years of age and more than 80% of people about 60 years of age have some degree of cataract.
Refractive cataract surgery and its benefits
Cataract surgery is no longer just about curing blindness, it is also a refractive surgical procedure that can correct all forms of refractive error including myopia (short-sightedness), astigmatism, and presbyopia. The surgery helps individuals to reduce or eliminate their need to use spectacles. In fact, because of how prevalent cataracts are, it is one of the commonest ways to correct refractive errors.
Modern cataract surgery is performed safely and effectively these days. In the hands of an experienced surgeon, it is one of the safest and most successful surgeries in the world.
Cataract surgery can be performed when the blurry vision is affecting or impairing one’s vision and affecting one’s daily activities. With modern cataract surgery, it is no longer necessary to wait for cataracts to ‘ripen’ or for the vision to be poor before one can consider surgery.
Modern cataract surgery is known as phacoemulsification. It is a painless procedure that takes less than 30 minutes to complete. The cataract is softened and removed through a small 2mm incision at the edge of the cornea. An artificial intraocular lens is implanted immediately following the cataract removal and the wound often seals on its own without the need for stitches.
Wide range of intraocular lenses
There is now a wide range of intraocular lenses for people to choose from depending on eye condition, lifestyle and occupation, and they include toric lenses to correct astigmatism and multifocal lenses to correct both distant vision as well as presbyopia. This allows more people to enjoy better vision and greater convenience without spectacles post-surgery.
The current intraocular lens technology is able to provide better vision after cataract surgery. There are now diagnostic machines which give greater accuracy in the lens power measurement which in turn improves accuracy in correcting one’s refractive errors resulting in sharper vision post-surgery.
4 / TREATMENT OF PRESBYOPIA (‘LAO HUA’)
Presbyopia can be effectively corrected with refractive surgery to reduce one’s need for reading spectacles.
In the presence of cataract, one can undergo refractive cataract surgery to have their cataract removed and at the same time have their myopia, astigmatism and presbyopia corrected with the appropriate intraocular lens.
For those who do not have cataracts, refractive surgery can correct one’s pre-existing refractive error (eg myopia) as well as presbyopia. The commonest option is to do a LASIK monovision correction. The master/dominant eye will be corrected to allow one to see far. The non-dominant/non-master eye will be corrected for reading, so that one can see far and read at the same time post-LASIK. Because the brain automatically chooses clearer eye to see, most will naturally feel comfortable with monovision and go about their normal routines without the need for spectacles to see both far and near.
With advances in refractive surgery which improve success rates, safety and effectiveness, people can achieve better vision and greater convenience without the need for spectacles and contact lenses.
In the hands of an experienced surgeon, complication rates are negligible. A surgeon who has experience in performing the various types of refractive surgery will be able to advise the best possible surgical option to achieve an optimal visual outcome.