HOW DOES LASER EYE SURGERY WORK?
Laser eye surgery is a marvel of modern technology.
Short sightedness, long sightedness and astigmatism are defects in the focussing power of the eye. The most common way of fixing these problems is to wear glasses or contact lenses. Contact lens technology has advanced in recent years and their price, range and availability has significantly improved. There still remains the underlying sense that these solutions are a temporary fix.
Laser eye surgery is a well established and safe treatment to reduce or remove completely the need for glasses and contacts. It achieves this by changing the power of the cornea - the dome shaped clear window on the front of the eye. As the shape is changed, the focussing power of the eye is adjusted in turn.
HOW DOES THE LASER WORK?
There are two types of laser used for laser eye surgery - an excimer laser and a femtosecond laser. The excimer laser works by using thousands of small spots that each remove a small amount of cornea. This acts to sculpt and changes the shape of the cornea, flattening it centrally for short sightedness or making it steeper for longsightedness.
PRK (PHOTOREFRACTIVE KERATECTOMY)
PRK (also called surface treatment, advanced surface ablation or LASEK) uses only the excimer laser. First, a fine layer of skin is removed from the surface of the cornea using alcohol or the laser itself (transPRK). After this the reshaping treatment is performed (usually 10-40 seconds) and then a medication called mitomycin C is applied for 20-30 seconds. This is washed away and some antibiotic drops and a contact lens are placed. The whole procedure takes around 5 minutes per eye. You will be given topical anaesthetic drops and offered a mild relaxing sedative beforehand - the procedure is painless. The eye is uncomfortable for a few days after surgery as the skin cells regrow over the treated cornea. The vision can fluctuate for a few weeks.
LASIK (LASER IN SITU KERATOMILEUSIS)
LASIK is very similar to PRK, except that a different laser is used to create a flap in the cornea before the excimer laser reshapes the underlying surface. This additional laser is called a femtosecond laser. It works by forming microscopic bubbles between tissue layers which can be used to create incisions and channels. The first step of LASIK involves docking the eye with the femtosecond laser. This is a comfortable process and is not painful. The vision becomes quite dark for a short moment. The laser then forms the flap in a number of seconds. The second part involves lifting the flap and then performing the reshaping treatment with the excimer laser.
What is it like to have LASIK? In this video Dr Gunn explains what to expect.
WHICH IS THE RIGHT TREATMENT FOR ME?
The benefit of performing LASIK is that the treatment is hidden under the flap so there is no surface skin that needs to regrow such as in PRK. The eye is a little uncomfortable overnight but less so than after PRK where the discomfort persists for a few days. Also, vision becomes sharper more quickly with LASIK, though PRK and LASIK give the same visual results at 3 months.
The downsides of LASIK are that the flap can rarely be associated with issues, such as dislocation or epithelial ingrowth. Thankfully these are rare and treatable, though they are avoided in PRK. There is also some additional cost with LASIK as a second laser is needed. Most patients are good candidates for LASIK and PRK and it comes down to preference, while others are poor candidates for LASIK and are better to have PRK. Dr Gunn will make this assessment when you are assessed at QEI Laser. Due to the shorter recovery and faster return of vision, most patients who can have either end up choosing LASIK.
HOW LONG DO I NEED OFF WORK AFTER LASER EYE SURGERY?
This depends on what procedure you have and what your work environment is like. After LASIK you can usually drive the next morning and most return to work after 2-3 days. Dr Gunn performs LASIK on Thursdays and Fridays and most patients take the weekend off.
After PRK, the recovery is longer. Dr Gunn recommends you take one week off. Some people recover faster, but most need the full week. You will attend the clinic 1 week after surgery and at this appointment usually you will be given clearance to drive.
I’M TRAVELLING TO BRISBANE FOR MY SURGERY. HOW DOES THAT WORK?
Many patients travel to Brisbane to have their laser eye surgery with Dr Gunn. You can have your laser assessment on a Tuesday and if you are a good candidate then have your laser procedure performed on the Thursday or Friday that same week. Dr Gunn will review you on the Tuesday or Wednesday after that before you return home, so you can plan to be in Brisbane for 7-8 days. When you book your appointment you can make a tentative booking for surgery following if you wish and that way the option will be open. There is always however the chance that you attend your assessment and you are found to be a poor candidate for laser or would benefit from a different type of procedure which may mean a separate trip. Read more about Travelling to Brisbane for eye surgery.
WHAT HAPPENS IF I MOVE DURING THE TREATMENT?
This is a common question and thankfully has been mostly solved with modern laser platforms. Recent lasers have extremely advanced eye tracking mechanisms that adjust the position of each laser spot to the current position of your eye. For example, the excimer laser at QEI laser takes an exact measurement of your eye position over 1000 times per second. After each check the laser adjusts itself so that the next laser spot goes in the exact place that was planned. It then does a second check to see that the eye hasn’t moved in that tiny moment. If the laser is positioned correctly and the eye hasn’t moved it will place the spot (obtaining a rate of 500 spots per second). This means that the eye position is checked, accounted for and double checked before every single spot is placed. If your eye moves beyond a range that the laser can adjust for, the system pauses the treatment immediately. This is hundreds of milliseconds (or effectively hundreds of laser spots) before the surgeon would realise that you had moved and be able to stop the laser manually. When your eye is returned to a normal position the surgeon can resume the treatment from the exact point at which it was paused. This is only one of many safety measures that make modern laser eye surgery so incredibly safe.
DOES LASER EYE SURGERY WEAR OFF?
No it does not. The treatment should give a stable result. There are two reasons patients may need glasses again after surgery. The first and most common is that they reach the age of presbyopia. This is where the natural lens in the eye begins to lose the ability to change focus from distance to close up. It occurs between the ages of 42 to 47 years in most people and means that reading glasses are needed for close work. This is due to the natural ageing of the eye and is experienced by people whether they have had laser eye surgery or not. There are ways of getting around this with an enhancement procedure. If you are already 40 at the time of laser, the treatment will be modified to help with this problem.
The other reason to need glasses again after laser is that of a changing prescription. Laser eye surgery moves your glasses prescription from its beginning power to zero but it does not stop your eyes from changing if they are already naturally doing so. Most people find their glasses stop changing at some point between the age of 18 and 30 years old. If a patient has an unstable prescription, then although they will see well very soon after laser eye surgery, they may find they need a small prescription again at some point. Thankfully most of the time an enhancement can be performed. To minimise the chance of this, Dr Gunn would recommend your prescription be changing less than 0.5 dioptres per year to consider laser. Your optometrist can often let you know the right time.
I AM PREGNANT OR BREASTFEEDING. CAN I STILL HAVE LASER EYE SURGERY?
The hormonal changes that occur during pregnancy and breastfeeding alter your prescription and the healing response after laser so is not a good idea to consider treatment during that time. You should wait at least 3 months after cessation of breastfeeding to have your assessment.