Recent medical advances have now made it possible to permanently correct myopia (nearsightedness) through laser surgery. What this means is that those who for years have depended on spectacles or contact lenses and find them inconvenient, dislike their appearance or who suffer from spectacles and contact lens wear intolerance, can now consider refractive surgery to reduce or eliminate their dependence on them.
The goal of Lasik is to reduce or eliminate dependence on spectacles and contact lenses permanently by the surgical reduction or elimination of myopic power. Note that in some cases, the doctor may deliberately aim for slight undercorrection. Lasik when successful, will allow you to carry out most of your daily activities without the need to wear spectacles or contact lenses. If spectacles are needed, they are usually worn at night and will be of considerably reduced power and thickness.
You should be 18 years or older with no significant change in your spectacles or contact lens prescription for at least the last two years. There should be no medical history of any active eye diseases such as cataract, glaucoma, retinal detachment or keratoconus.
Your eye doctor (ophthalmologist) will be able to tell you if you are a suitable candidate after a comprehensive eye examination. He will also counsel you on the procedure and you should in turn take this opportunity to address any concerns that you may have about the procedure.
You should not be suffering from any active eye diseases such as cataract, glaucoma, retinal detachment or keratoconus. If you suffer from severe dry eyes or a past ocular herpes infection, you may also not be a good candidate. Also, be sure to tell your doctor if you or anyone in your family has ever had a cornea disorder, diabetes or autoimmune disorder. You should not be taking certain prescription drugs like oral prednisolone. These conditions may increase the risk of serious complications.
Lasik cannot be done if you are pregnant. Persons with an obsessive nature or who have great difficulty finding glasses to suit their eyesight are also advised against treatment.
Lasik stands for Laser Assisted In-Situ Keratomileusis. It is now widely considered as the procedure of choice for the correction of most cases of myopia. In selected cases, it can also be used to correct mild to moderate degrees of astigmatism and farsightedness.
Lasik is sometimes called the “flap and zap” procedure.
It combines an established cutting technique using a cutting device called the microkeratome with the more recently developed excimer laser technique so that sight is improved without the need for glasses or contacts. First, a circular superficial cornea flap is made with the help of the microkeratome. Next, the flap is folded back to allow the excimer laser to reshape the deeper layers of the cornea according to the patient’s spectacles prescription. The flap is then folded back and will adhere itself naturally without the need for stitches.
The entire surgical procedure takes only 10 minutes or less per eye. The actual amount of time the laser is active on the eye is only one minute or less.
The first Lasik was done in 1989. Today it is considered to be an established medical procedure with much research to back its efficacy, stability and safety. Millions of cases have been done so far and over a million cases are done around the world every year. In experienced hands and using good equipment, it has a low major complications rate of less than 2%. Lasik is now widely considered by most refractive surgeons around the world as the overall procedure of choice for permanent surgical correction of myopia. Safety is in fact the main reason for choosing the Lasik procedure over others.
No. Lasik is carried out as an outpatient procedure and you can go home after the procedure on the same day. Altogether, with the pre-operative preparation, post-operative recovery and evaluation, you should expect to stay a couple of hours.
The risk of going blind from Lasik is very rare. To date, there has been no reported cases of blindness from the over ten thousand cases done in Singapore. However, there may occur what is termed as “loss of best corrected visual acuity”. This means seeing worse after the procedure than before despite the best spectacles or contact lens prescription. Fortunately, this complication usually only affects the ability to read the bottom few lines of the standard vision test charts. Other vision attributes may also be affected (see Q 27).
Yes. Research data have shown that bilateral Lasik is safe and convenient. This practice is in fact now routine in many centres around the world. In fact, bilateral surgery is preferred by many patients and surgical centres for the following reasons:
– half the emotional stress of going through the procedure.
– half the amount of time off from work and for the recuperation process.
– no problem with double vision and vision intolerance from anisometropia during the interval between the first and second treatment. Anisometropia describes the condition of imbalance vision resulting from grossly differing refractive powers between the two eyes.
Some surgical centres and patients may elect to have the eyes treated separately for the following reasons:
– fear of having both eyes operated on at the same time.
– concerns about bilateral eye infection. The serious eye infection rate is about one in five thousand eyes.
– reduced risk of bilateral overcorrection.
All contact lens wear must be stopped well before the day of surgery. RGP, semi-hard or hard contact lens users should stop wearing them at least two weeks before the procedure. Soft contacts users should stop one week before. This is because contact lenses are worn on the cornea and will temporarily change the shape of the cornea slightly, but significantly enough to affect the results of the surgery.
Make-up, perfume or hair-care products must not be worn or used on the day of surgery. The vapours emitted by these may interfere with the sensitive laser. Also, have someone follow you on the day of surgery. You should not drive immediately after the procedure as vision will be slightly blurry.
No. The whole procedure is done under local “eye drops” anaesthesia and is painless. No injections are given. You may experience a sensation of pressure when the lid speculum, used to keep the eye open, is inserted and when the cornea flap is made. For anxious patients, your doctor may prescribe a mild sedative to be taken before the procedure.
After the procedure, some scratchy irritation, light sensitivity and tearing is common. These after-effects usually last for about six hours and can be relieved by instilling lubricating artificial tears eyedrops and wearing sunglasses.
How is the Lasik procedure performed?
The surgery is performed in the recumbent position, with the patient either resting on a bed or in a reclining chair. The eye is first cleaned and draped. Numbing eye drops are instilled and a speculum is inserted to help prop the lids open. A tight pressure sensation may be felt at this stage which is also generally considered to be the most uncomfortable part of the procedure. An instrument is used to mark the cornea surface and the actual Lasik procedure now begins.
A suction ring is placed on the eye to provide a base for the microkeratome which is used to create the cornea flap. Suction is applied to hold the eye steady and to maintain the internal eye pressure while the cornea flap is being made. Do not be alarmed if your vision becomes dim or dark at this stage. You will hear a high pitch mechanical sound for about five to ten seconds. Suction is then released and vision returns. The cornea flap is now folded out of the way to expose the deeper layers of cornea tissue for the laser treatment phase.
For the laser treatment phase, you will be asked to fix your gaze at a blinking red light. The excimer laser is triggered and the high pitch clacking noise of the laser is heard and a slight smell may be detected. The laser is guided by information fed from the computer programme as it precisely sculpts the inner layers of the cornea according to your spectacles prescription. For myopia correction, the laser essentially reshapes the cornea curvature into a flatter curve. This part of the procedure will lasts about 15 to 45 seconds depending on the amount of correction required.
Once the laser stage is completed, the cornea flap is unfolded back into its original position. After a short wait of two minutes, the flap will bond itself back naturally without the need for stitches.
Blinking is not a problem as your eye is propped open throughout the procedure by the lid speculum. When the cornea flap is being created, you will not be able to move your eye as it is held firmly by the strong suction force exerted through the suction ring.
During the laser phase, you are required to keep your gaze fixed at the blinking red light straight ahead.
Do not worry that your eye may inadvertently drift away as the surgeon is closely monitoring the procedure throughout and can halt treatment at any time should drifting occur. In addition, all modern lasers have a sophisticated built-in eye tracking system that will actively follow any small movements of your eye. This will ensure that the laser treatment is applied at the right spot throughout the procedure.
All reliable Lasik systems will come equipped with a UPS (Uninterrupted Power Supply) back-up of at least two hours. This is more than enough for a procedure that takes only about 10 minutes.
The superficial circular cornea flap will self-adhere itself naturally within a few minutes. Within 24 hours, the cornea surface epithelium cells begin to migrate in to seal the edges of the flap. Stitches are therefore not necessary.
No. However, as a precaution against rubbing and accidental trauma, you are required to wear the protective transparent eye shields or eyewear throughout the day and overnight for the first 24 hours. Subsequently, they need to be worn only when sleeping for the first week. Occasionally, your doctor may require you to wear a special contact lens for the first week after the procedure.
It is important to adhere to the antibiotic and anti-inflammatory eye drops regime prescribed by your doctor following the procedure to prevent bacteria infection and to moderate the healing response. Also avoid crowded and dusty places for the first three days. Remember to keep the eyes well lubricated to relieve the temporary dryness of the eyes that occur after treatment.
A protective eye shield should be worn when sleeping for the first week to prevent rubbing and accidental trauma to the eye. You should be careful not to squeeze the eyelids hard and not to drive for the first 24 hours after the procedure.
Most patients will already notice much improved vision without glasses immediately after the procedure. However, the most dramatic improvement is noticed after resting the eye overnight. Most patients will see well enough to drive without glasses the second day after the procedure. Thereafter, a gradual improvement in vision is expected as further healing occurs over the next few weeks. Vision is usually stable in a month’s time. Some patients may have trouble with glare and seeing haloes during the first few weeks. Those with naturally big pupils or with correction done for high myopia are more likely to be affected. In most cases, these complaints will lessen or go away after six months.
Most patients can return to work in two days. You should avoid crowded and dusty places for the first week to reduce the risk of bacterial infection. Swimming, gardening and vigorous exercises should be refrained for at least two weeks.
Generally, most doctors will see their Lasik patients the following day, at one week, one month, three months, six months and then yearly, if there are no complications.
Lasik is most effective when treating myopia from -1.00 dioptres to -8.00 dioptres (i.e. 100 to 800 degrees). Treatment above this power is associated with less predictable results and higher complication rates. This is because beyond -8.00 dioptres of correction, a greater amount of cornea tissue must be sculpted and this will begin to thin the cornea to its safety limits. Current treatment guidelines require that at least 250 microns or a quarter of a millimetre thickness of cornea must be preserved beneath the flap if cornea complications are to be avoided. For this reason, your doctor will measure your cornea thickness prior to the surgery to determine the safe limits of myopia correction.
A power of -12.00 dioptres (1,200 degrees) is usually taken as the upper limit of safe Lasik treatment by most doctors. Above this power, many eye surgeons will instead advise intra-ocular lens implantation as the procedure of choice. Here, a small wound is made at the side of the cornea and an artificial lens, made of plastic, silicone or acrylic material, implanted permanently inside the eye.
The artificial lens is placed either in front of the natural crystalline lens or in its place. Visual recovery is rapid and painless with the eye seeing well the next day.
Up to moderate levels of astigmatism (3.00 dioptres) can be effectively treated at the same time. For more severe astigmatism, the results are less predictable. In the near future, customised ablation incorporating wavefront technology may improve the results (see Q43). Keratoconus, a cornea disorder characterised by localised thinning of the cornea has to be excluded before treatment of any astigmatism.
Lasik can effectively correct up to +4.00 dioptres (400 degrees) of farsightedness. Farsightedness is the optical opposite of myopia (nearsightedness). It is caused by a shorter than normal eyeball length or flatter than normal cornea curvature.
However, it is important not to confuse normal farsightedness with an aging condition called presbyopia or middle-age farsightedness. This is a different condition that afflicts those past the age of 35 years. Presbyopia is caused by the reduced ability of the eye to focus for near as a person grows older. Lasik will NOT do away with the need to wear reading glasses for this condition. In fact, those 35 years and above may find that after Lasik, while they can now see perfectly well for distance, reading glasses may be required for reading.
-Under or over-correction:
Under or over-correction of refractive power can occur despite the surgeon’s best effort. This is due to individual variation in the healing process and in tissue density. Over- correction is less well accepted than under-correction. While an under-corrected eye can still see well for near without lenses, a significantly over-corrected eye will need glasses to see well for both near and distance. For this reason, most doctors will deliberately aim for a slight under-correction, especially when correcting patients with high myopia.
If significant under- or over-correction has occurred, a second “enhancement” treatment can be considered in some cases. However, this treatment is usually advised to be done only after the refractive status has stabilised. This could be anytime from three weeks to three months after the initial procedure.
– Glare, Haloes and Starbursts:
Some patients may experience bothersome light sensitivity and glare or they may complain that they see halos, starbursts and “ghost images” next to the real image. These effects are usually most noticeable at night, especially when looking at light sources such as the headlights of oncoming cars. Patients with naturally large pupils or who had correction done for high myopia are at greater risk.
These after-effects can limit one’s ability to drive, work or operate certain equipments. In most cases, the symptoms lessen significantly or go away within six months. However, in some cases, they may persist indefinitely.
-Cornea flap complications:
The Lasik procedure may be aborted because of problems encountered when creating the cornea flap. These include an incompletely cut flap, a completely sheared off flap or a flap with a button-hole defect. Post-operatively, wrinkles may develop within the flap or the flap may become dislodged. All these flap complications can cause optical aberrations that are difficult to correct with glasses.
There is also a category of post-op flap interface disorders. This includes Diffuse Lamellar Keratitis which is caused by trapped foreign body debris or toxins and an epithelial ingrowth syndrome caused by migration of surface epithelial cells into the undersurface of the flap. In the severe case, the flap needs to be re-lifted, cleaned and repositioned. While severe cornea flap complications are rather uncommon, they can lead to loss of best corrected visual acuity.
– Loss of Best Corrected Visual Acuity:
This means seeing worse after the operation than before despite the best spectacles or contact lens correction. A common cause would be irregular astigmatism arising from de-centred or uneven ablation. The uneven bumps on the surface of the cornea that result from uneven ablation is also known as “central islands”.
Loss of best corrected visual acuity can also occur from excessive cornea scarring, cornea haze and flap related complications. Usually, vision improves with time as further healing occurs. Severely affected patients may suffer a permanent drop in their best corrected visual acuity. Fortunately in most cases, vision loss is limited only to difficulty in reading the bottom few lines of the visual acuity chart.
– Equipment malfunction:
Both the microkeratome and the excimer laser are manufactured and maintained according to the manufacturers’ exacting specifications. However, it is still possible that the machines may malfunction, requiring the procedure to be stopped before completion. In some instances, this could result in loss of best corrected vision.
– Contact Lens Wear Intolerance:
There is the risk that should you need to wear contact lenses after the procedure, they may not fit comfortably. This is due to changes in the cornea shape after the procedure that affect the way the contact lens sits on it.
– Dry Eyes:
Dryness of the eyes and recurrent cornea surface epithelial cell erosions are other common but non-sight-threatening problems that can occur after Lasik surgery. Nonetheless, they can be a source of frequent irritation.Therefore, frequent instillations of lubricating eye drops are recommended during the first few weeks post-operatively.
– Eye Infection:
Severe infection that cannot be controlled by antibiotics is one of the most feared complication of any eye surgery. Fortunately the incidence is rare. It is estimated to occur in less than 1 in 5,000 eyes. When it occurs, it can cause severe cornea scarring, vision loss and even loss of the eye. Therefore, it is important to keep the eye clean, avoid going to crowded, dirty places and to apply the prescribed antibiotic eye drops diligently in the immediate post-op period.
In some eyes, the long term use of the anti-inflammatory steroid eye drops commonly prescribed to control scarring can cause glaucoma.
– Retinal Detachment:
Retinal detachment may occur if predisposing lesions, such as retinal tears and areas of retinal thinning, are not detected and treated.
Yes. This complication is also known as loss of best corrected visual acuity. It means that you are not able to see as well after surgery as you did before surgery, even with the best spectacles or contact lens correction given. It most commonly arise from cornea related problems such as corneal haze or scarring, decentred or uneven laser ablation and cornea flap complications. Fortunately, the likelihood of this happening is less than two per cent and there is a fair chance of further vision improvement with time. Loss of best corrected vision occurs is usually limited to difficulty in seeing clearly the bottom few lines of the visual acuity chart.
Other attributes of vision may become affected. Foremost of these is a decrease in contrast sensitivity. This means that even though you may have normal 6/6 vision, you have decreased ability to discriminate between shades of grey, especially under dim lighting. This may cause objects to appear fuzzy or greyish. There may also be complaints of excessive light sensitivity, glare, haloes or ghosting. Haloes are “rings”around lights. Ghosting is the phenomenon of seeing a second false image next to the real one. Most of these vision complaints will alleviate with time but in some cases, they may persist indefinitely and affect the overall quality of vision.
No. Lasik may not give you perfect vision everytime. The American Academy of Ophthalmology (AAO) reports that seven out of ten patients achieve 6/6 or better vision. About 95% will achieve 6/12 or better vision. 6/12 is the minimum visual requirement for obtaining a driving licence in most countries. It also means reduced dependence on glasses or contact lenses for most daily and sporting activities.
Under or over-correction may occur despite the surgeon’s best effort due to individual variation in the healing response. When significant, a second “enhancement” procedure may be recommended by your doctor. Sometimes, a mild under-correction in one eye is deliberately aimed for in older patients likely or already suffering from presbyopia (middle-age farsightedness). This concept is termed “mono-vision” (see Q34).
Enhancement is done in about five to fifteen per cent of cases. It is simply done by re-lifting the cornea flap and using the excimer laser to fine-tune the desired refraction. However, there should be a waiting period of between three weeks to three months, with the refractive status stable, before proceeding. During this interim period, if clear distance vision is desired, low-power spectacles or contact lens can be prescribed and worn when required.
For severely over-corrected eyes, re-treatment maybe difficult. Therefore, to reduce this risk, most doctors deliberately aim for a slight under-correction when treating high to moderate myopia.
Yes. The first Lasik procedure was done in 1989. To date, several millions of cases have been done worldwide, mostly with good results. Research studies have shown the results to be stable as long as established treatment protocols are followed. It is also the general consensus of eye surgeons and researchers worldwide that these results are likely to remain stable in the future.
Unstable results have occurred when the amount of cornea tissue sculpted exceeded recommended treatment guidelines. Occasionally, unstable results have occurred because of treatment of eyes with undiagnosed keratoconus. Keratoconus is a condition characterised by cone-shaped thinning of the cornea. Its presentation is often subtle in the early stages and can only be diagnosed with specialised instruments.
This is a legitimate concern especially since radial keratotomy (RK), the predecessor of laser refractive surgery, has been implicated to cause structural weakening of the eye. However, there is no medical evidence to date that Lasik causes long-term structural weakening of the eyes as long as the established treatment protocols are observed.
This is unlikely to happen as Lasik candidates should be past the age of 18 years with stable myopia. However, patients should still take good care of their eyes, especially in limiting excessive near vision work. Should further myopia progression occur, they are likely to be of small magnitudes. Low power spectacles or contact lenses can still be prescribed if required. Alternatively, a second “enhancement” Lasik may be considered but your doctor’s advice on this should be sought first.
The myopic eye tends to lose its power of accommodation or focusing ability for near vision at an earlier age than the normal eye. This aging eye phenomenon is called presbyopia or middle-age farsightedness. It is caused by the progressive hardening of the crystalline lens in the eye and weakening of the focusing ciliary muscles. It usually starts to occur past the age of 35 years in myopic eyes. Indeed, those in this age group who have had successful Lasik surgery may find that reading glasses may now become necessary for near vision work even though they can now see clearly for distance.
It is also for this reason that many Lasik surgeons will counsel patients who are over 35 years on the benefits of mono-vision correction.
Mono-vision correction is recommended by many Lasik surgeons for their patients aged 35 years and above who are presbyopic or who are likely to become so in the near future. The aim of mono-vision correction is to enable the patient to have a close to full range of vision with much reduced dependence on glasses for both distance and near vision. This is achieved by aiming at full or close to full correction in the master eye and mild under-correction in the other, non-master eye.
To tell which is your master eye, cut a coin-sized opening in a piece of paper and hold it at arm’s length in front of you. Next, with both eyes open, look at a distant object, such as a clock on the wall, through the opening. Now, without moving the paper, alternately shut your left and your right eye. Your master eye is the eye that sees the object.
Most eye doctors worldwide now consider Lasik as the overall surgical procedure of choice for permanent surgical correction of myopia. However, there are other alternative surgical methods available that may be more appropriate in certain circumstances. These techniques, and the benefits and risks of each, are discussed in greater details here.
In Radial Keratotomy, or RK as it is more popularly known, four to eight fine incisions are made in the cornea with a diamond knife. These cuts, made in a radial or spoke-like pattern, will allow the normal pressure inside the eye to steepen the sides of the cornea while the centre optical zone curvature flattens. This results in an effective reduction of myopia power.
RK is considered the forefather of modern popular refractive surgery. The procedure has its beginnings 40 years ago when it was first introduced by Sato and associates in Japan. However, the early technique was fraught with complications until the Russian eye surgeon Fyodorov improved upon it and made it safer and thus more popular in the mid-seventies. Today, the RK technique has been further refined and has incorporated astigmatic correction into its protocol. Notwithstanding, the results are still less predictable and stable as compared to Lasik and the healing process is slow and painful. In addition, the cuts made have been shown to weaken the cornea, causing late onset hyperopia (farsightedness) and susceptibility to disastrous eyeball rupture should the eye suffer a strong knock. Die-hard proponents of the procedure tout the fact that RK will never cause scarring of the central optical zone of the eye and that it is much more cost effective. Presently, a modification of RK is commonly used by refractive surgeons during cataract and lens implantation surgery to correct astigmatism.
Photorefractive Keratectomy or PRK, is the predecessor laser refractive surgical technique before Lasik became popular. It uses the high energy ultra-violet rays of the excimer laser to directly sculpt the surface layers of the cornea, essentially flattening the curvature, to correct myopia.
The excimer laser is not a new invention, being developed way back in the seventies by the computer industry for the precise etching of computer chips. It is a so-called cool laser, meaning that it can cut through various materials with minimal heat damage. That was just the kind of delicate tool that eye surgeons were looking for to improve the accuracy and predictability of refractive surgery.
The first application of the excimer laser on the human eye was in 1983. However, it was only in the early nineties when PRK treatment protocols were established that the procedure became widely available to the general public. PRK is technically a simpler procedure compared to Lasik. There is no need to create a cornea flap thereby eliminating the risk of cornea flap related complications. Statistics show that 95% or more of patients with mild to low moderate myopia saw 6/12 or better without glasses after the surgery. However, the post-operative recovery period is longer and more painful then the Lasik procedure. The eye requires at least three days for the treated cornea surface to heal. The refractive power is also unstable for the first three months. Most importantly, the final refractive outcome is less predictable than with Lasik surgery, especially when treating more than – 5.00 dioptres of myopia. This is due to the marked individual variation in healing response when the superficial layers of cornea are treated. There is also an increased risk of severe cornea scarring of the central optical zone. As such, PRK soon became supplanted by Lasik. PRK if done, if best reserved for treatment of low myopia only.
Intra-ocular lens implantation
This technique involves making a small wound at the side of the cornea and implanting an artificial lens made of a biologically inert material such as acrylic, PMMA (plastic) or silicone permanently into the eye. The artificial lens may be implanted in front of the natural crystalline lens or in its place following lens extraction. The major advantage of lens implantation surgery over laser refractive surgery is its effectiveness in treating severe to extreme levels of myopia of over -12.00 dioptres (over 1,200 degrees).
In young patients, the artificial lens is implanted in front of the natural crystalline lens, thereby preserving accommodation or focusing ability for near. A drawback here is that the implanted artificial lens may rub on the internal structures of the eye causing inflammation of the iris (iritis), cataract and possible long term damage to the delicate inner endothelial layer of the cornea.
In older patients, where accommodation (focusing ability) is absent and where there is evidence of lens opacity, intra-ocular lens implantation following extraction of the natural crystalline lens is usually the preferred method. This procedure is in fact akin to modern cataract operation. Cataract operation is one of the most common and safest operations in medicine. It is done as a twenty minutes outpatient procedure without stitches and under local anaesthesia. Post-operative recovery is quick and painless. Visual recovery following lens implantation is almost immediate. The results are also stable and predictable from early on. However, a major concern is the possibility of incurring an intra-ocular infection which cannot be controlled by antibiotics. The incidence is low at about 1 in 1,000 eyes but when it occurs, vision loss is usually severe.
Cornea Ring Implants (INTACS)
Here a small cut is made at the side of the cornea and two halves of a clear plastic ring are implanted into the cornea tissue at its periphery to induce flattening of its central curvature. The thicker the ring, the more the cornea is flattened and the greater the myopia correction. The proponents of this technique tout its relative simplicity and lack of use of expensive, sophisticated laser machines.
There is also no risk of scarring the central optical zone of the eye. Another attractive advantage is its easy reversibility. The rings can be removed if the patient is not satisfied or replaced to accommodate prescription changes. Unfortunately, ring implants are only effective for low levels of myopia with low or no astigmatism. It cannot correct above – 5.00 dioptres of myopia. Glare, haloes, double vision, difficulty with night vision and fluctuating distance vision are some of the visual side-effects reported.The post-op recovery and after care is also somewhat more tedious than that with Lasik surgery.
Lasik is suitable for those 18 years and above who have had stable myopia for at least two years. Below 18 years of age, myopia is frequently unstable and the eye is likely to heal with excessive scarring. Notwithstanding, some eye surgeons have performed Lasik selectively for teenagers who suffer from severe anisometropia. This is a condition caused by a gross imbalance of refractive powers between the eyes such that spectacles cannot be satisfactorily prescribed.
Lasik is frequently contemplated by those aged 35 and above who have been wearing contact lenses for many years and who have developed problems of dry eyes, allergic eyelid disorders, cornea inflammation or contact lens wear intolerance. It is important that candidates considering surgery in this age group be forewarned that presbyopia (middle-age farsightedness) may become unmasked after the surgery. Dry eye condition if pre-existing, may also be aggravated.
Those aged 60 and above are in the high risk group for cataract and should therefore be carefully examined for evidence of any developing lens opacity. If this is present, artificial intra-ocular lens implantation following crystalline lens extraction is the procedure of choice.
Lasik is almost always an elective surgical procedure with no pressing medical need to have it done. It also means that you can choose where and when to go for it. The alternatives of wearing spectacles or contact lenses should always be considered first before surgery.
You will need to sign an informed consent form. This means that you understand the nature, benefits and risks of undergoing the procedure. Lasik surgery cannot be reversed and there is no guarantee of achieving perfect vision. People who are very fussy about their vision or who have great difficulty finding a suitable prescription for their glasses are advised against going for Lasik. Note that in some cases, your eye surgeon may advise on deliberate under-correction of one eye for mono-vision correction (see Q. 34 What is mono-vision correction?). You should also be aware that additional “enhancement” surgery may be needed to get the best possible vision after Lasik.
Those with high myopia should be aware that the complication rate is higher. Lasik does not interfere with the normal aging eye disorders such as presbyopia and cataract. In fact, those over the age of 35 years often find that while Lasik surgery has been successful in restoring clear distance vision, it may unmask the need to wear reading glasses.
The decision to go for Lasik surgery is a very personal one. Think carefully through all factors influencing your decision. Consider your lifestyle, vision needs, satisfaction or dis-satisfaction with spectacles and contact lens wear in making your decision. Anyone contemplating Lasik surgery must weigh the benefits against their own risk tolerance for potential complications. Understand your expectations from the surgery. Are they realistic?
The following are reasons often given by patients for deciding on surgery:
– To achieve freedom from glasses and contact lenses; that is to be able to wake up and see the alarm clock, put on make-up, shave, etc, without having to reach for the glasses. Also, no more foggy or lost glasses. No more sore and red eyes from wearing contact lenses. – To save time and money – it is estimated that a typical contact lens wearer would spend 20 minutes a day wearing, removing, cleaning and maintaining them. This translates to 7,300 minutes per year in contact lens care alone, not including time spent on fittings, buying replacement lenses and check-ups. – Occupational reasons – spectacles and contact lens wear may not be appropriate or allowed in certain jobs. – To be able to enjoy many sports such as swimming, scuba diving, skiing, football, etc, better without the hassle and inconvenience of wearing glasses and contacts. – To feel more confident and increase self-esteem. This is especially relevant for those with high myopia who may often feel “visually handicapped”. – To alleviate spectacles wear intolerance. – Unable to wear contacts due to contact lens wear intolerance or medical complications such as allergic conjunctivitis, GPC, corneal ulcers, cornea inflammation and dry eyes. – For personal security reasons – to be able to see clearly during emergencies such as fire, floods, accidents or while travelling.
Lasik is almost always an elective procedure in that there is no medical necessity to have the procedure done. Thus it is perfectly fine not to go for Lasik surgery, especially if you are presently happy or satisfied with your spectacles or contact lens wear. You should never feel pressured to go for the procedure. Those who perform fine detailed work such as artists, architects, draftsman and surgeons must especially weigh the benefits they hope to achieve against the risks of incurring complications such as the loss of best corrected visual acuity. Those who suffer from high myopia should also be similarly cautioned.
Today, Lasik is considered an established surgical procedure with much research to back its efficacy, stability and safety. It has undergone many refinements since it was first introduced in 1989. It has supplanted RK and PRK as the refractive procedure of choice for correction of most cases of myopia.
Indeed, the recent years have seen a dramatic growth in the number of cases performed, thanks in no small part to patients’ satisfaction with the visual results and “word-of mouth” advertising. It has been estimated that presently, over a million cases are done worldwide yearly.
All these could explain why Lasik continues to gain in popularity and why more and more people including high profile sports and media personalities, have elected or are electing to have it done today.
In Singapore, the cost for Lasik surgery is around $2,000 to $3,000 per eye. Initial consultation and examination charges are usually charged separately and will add $150 to $300 to the total bill. Medisave cannot be used except in cases where the patient suffers from severe (over -10.00 dioptres) myopia or imbalanced vision of more than -3.00 dioptres (300 degrees). In this case, you can use your Medisave to pay up to $1,200 of the cost.
You should arrange for a doctor’s consultation and eye evaluation to see if you are suitable for Lasik. The pre-Lasik eye examination will include the following:
– vision testing to check visual acuity
– testing of the eye power (objective refraction)
– subjective refraction to fine-tune the objective refraction
– eye pressure checks for glaucoma (tonometry)
– microscopic examination of the eye using the slit lamp bio-microscope, paying special attention to the cornea and pupil size
– instillation of dilating eye drops for dilated pupil examination of the eye, paying special attention to the clarity of the crystalline lens and health of the retina
– computerised testing of the eye power following relaxatin of the focusing muscles with eye drops (cycloplegic refraction) to diagnose any spurious (pseudo)myopia component
– measurement of cornea thickness (pachymetry)
– computerisd mapping of the cornea surface to screen for irregular astigmatism and keratoconus.
The Orbscan is an advanced multi-function machine that captures complete cornea surface topography data for front and back sufraces of the cornea, cornea dioptric power (keratometry), cornea thickness (pachymetry), pupil size and cornea diameters.
The Orbscan reproduces these captured data as two-dimensional color diagnostic maps for fast and easy interpretation. The data can also be combined with information from wavefront analysis and imported into the excimer laser computer system for customised ablation for the cornea (see Q43).
Your doctor will also take this opportunity to counsel you on the procedure and evaluate your expectations of what refractive surgery will do for you. You should in turn take this time to discuss with your doctor any concerns that you may have regarding the procedure. If you wear RGP or hard contact lenses, you will need to stop wearing them for two weeks before the visit. For soft contact lens wearers, one week’s abstinence is enough. As dilation of pupils using eye drops will be carried out, your eyes will be light sensitive and vision slightly blurry. Therefore, you should not drive and bring along a pair of sunglasses.
The microkeratome is the cutting device used to create the cornea flap in Lasik surgery. Its invention dates back over 40 years to 1958 when Barraquer from Spain conducted the first experiment on creating a circular cornea flap using a prototype of the modern day microkeratome. The next milestone was in 1989 when Buratto did the first Lasik on the human eye with a free cornea cap. Two years later, Pallikaris improved upon the procedure with the introduction of the “hinge” technique where a small amount of cornea is left uncut nasally to form a cornea hinge. The surgeon could then lift the cornea flap, perform the laser sculpting and reposition the flap onto its original site without the need for stitches.
In 1996, Buratto modified the technique further with a down-up vertical cut that places the resulting hinge superiorly beneath the upper eyelid. This was thought to be more physiologic as it follows the dynamic movements of the eyelid with reduced possibility of the flap becoming decentred or developing wrinkles in the immediate post operative period.
Today’s modern microkeratomes are automated and refined, offering better suction, more efficient cutting mechanisms and more ergonomic handling. As a result, the serious complications rate from this stage of the procedure is now down to less than 1% in the hands of the experienced surgeon. Future developments in the pipeline include using water-jets or laser keratomes to cut the cornea flap instead of the present steel blade in the hope of achieving an even smoother and complication free cut.
The microkeratome is the surgical cutting tool used to create the cornea flap.
The Excimer Laser
Laser refractive surgery was developed with the hope of replacing the variability of the surgeon’s microsurgical skills with the consistency of the laser. The dream became reality with the advent and application of the excimer laser to the human cornea in 1983. For the first time, there became available a precise and delicate way to directly and very accurately sculpt the refractive power of the eye onto the cornea, very much the same way a skilled lensman would grind a spectacles lens.
The excimer laser is often described as a “cool” cutting laser that uses high energy ultra-violet light to vapourise the cornea tissue without generating too much tissue heat. The early generation lasers delivered the laser energy via a fixed broad beam aimed at the cornea through a progressively widening aperture. The sculpting effect of these broad beam lasers were not completely smooth with rings, ridges and irregular surface protrusions. These protrusions, also known as “central islands” are areas of uneven ablation resulting from blockage of the incident laser beams by tissue fumes. Presently, most of the modern lasers in use utilise small scanning beams of 1 to 2 mm spot size rather than a fixed broad beam.
Modern excimer lasers utilise advanced
flying spot technology and eye tracking systems when sculpting the cornea.
The laser pulses are programmed by software to move (“fly”) rapidly in a randomised pattern with slight overlap to accurately sculpt the cornea with an extremely smooth surface. All modern lasers also come with an eye tracking system with feedback mechanisms to ensure well-centred laser ablations. Future developments will revolve around improving the laser ablation software for even smoother and precise ablation and integration of “wavefront technology”(see below). Also, eye tracking systems are being further refined to be fast enough to measure and compensate for even the small rapid (saccadic) movements of the eye, thus further improving the accuracy of the cornea sculpting.
Future developments will centre around the laser ablation software, intergration of wavefront technology and refinements to eye-tracking hardware.
Light travels in a process of flat sheets, known as wavefronts. In a perfect optical system, these flat sheets would look like a piece of paper standing on end.
The eye is not a perfect system. Irregularities in the system will cause the flat sheets or wavefronts to be deformed into variations that look like anything from a potato chip to a sombrero hat. Every eye has its own unique wavefront map.
Customised Ablation Incorporating Wavefront Technology
This is billed as the next step in the evolution of refractive surgery. Today’s laser and the computers that run them all assume the cornea as regular sphero-cylindrical refracting surfaces. However, we know that there exists in every person’s eye, unique optical aberrations that cannot be corrected by simple sphero-cylindrical optical systems such as spectacles and contact lenses. Previously, there was no way these so-called higher order aberrations could be measured, represented and treated. Now, using wavefront technology adapted from astronomical science, wavefront analysers have been developed that are able to map out point by point, aberrations that occur across the entire surface of the cornea. The information is translated into a three-dimensional (3-D) color coded cornea map. This information is then fed into the excimer laser’s computer together with data from the pre-Lasik evaluation and a reciprocal point by point customised laser ablation computed and delivered. The effect hoped to achieve is an effective neutralisation of the eye’s optical aberrations.
Such careful customised reshaping of the cornea should in theory enable consistent and astounding improvement in visual clarity. Clinical trials are presently underway. Already, hopes for routinely correcting vision to better than 6/6 or “eagle vision” are being touted.
With wavefront technology, it is now possible to capture and represent these irregular wavefronts as a three-dimensional colour map. By feeding this information and that obtained from the pre-Lasik evaluation into the excimer laser’s computer, a customised ablation profile can be computed and delivered. This could in theory, make perfect vision correciton routinely attainable.
As soon as the numbing effect of the eyedrops wears off, the eyes may begin to feel slightly sore and gritty. It may also be teary and light sensitive, but there should be no pain. There may also be some swelling of the conjunctiva and occasionally, some redness may occur. These complaints are most noticeable during the first six to eight hours when the surface cells of the cornea are healing.
Dry eye is now recognised to be a common problem during the early post-op period. Therefore, it is important to keep the eyes well lubricated with frequent instillation of the preservative free lubricating eye drops prescribed.