February 2016

What is ASLA?

ASLA stands for Advanced Surface Laser. It is really no different to PRK.

PRK was the original term used to mean a laser vision correction on the surface of the cornea without first creating a LASIK flap. PRK was largely superseded by LASIK due to quicker recovery time and no discomfort.

Over time however, PRK has had a resurgence owing to the fact that it is a better procedure in some people and the procedure of choice if the cornea is thin. It has become more sophisticated, with better software algorithms that use modern ablation profiles. This has led to better visual outcomes. As the algorithms have progressed, it was decided to re-name PRK to ASLA.

Some clever marketing has tried to create the impression that it is a new procedure but it it is still really PRK, although on steroids.


Long term, there is no difference in results between ASLA and LASIK. ASLA is not an inferior procedure and patients having it are not disadvantaged in any way. It is simply as stated, more uncomfortable and visual recovery  takes longer.

In some respects, ASLA is safer as there is no corneal flap to worry about and all its attendant risks such as epithelial ingrowth, striae or dislodgement of the flap.

There is no difference in cost.

How is ASLA performed?

There are numerous ways to perform ASLA. Most commonly, the epithelial surface is removed using a blade, motorised burr or alcohol. Alcohol removal is quicker but there is some suggestion that this may lead to recurrent erosions long term.

The new Schwind Laser that we are using performs transepithelial ASLA, meaning that the epithelium is automatically removed by the laser. This results in a cleaner and more precise result.

Once the epithelial surface is removed, the laser then continuous on to re-shape the surface of the cornea. In the case of someone with myopia (shortsightedness) the laser tends to flatten the central portion of the cornea. In the case of hyperopia (long sightedness), the laser steepens the central cornea instead. The process is similar to a lathe, altering the shape of a piece of wood.

This of course is all done under anaesthetic, which is administered with eyedrops only. That is, there are no injections or needles involved.

At the end of the procedure, a contact lens is placed into the eyes and left there for three days until the new epithelium has grown back.

What happens after the ASLA procedure?

After the procedure, you can go home with antibiotic and anti-inflammatory eye drops.

Review is on the third day after the procedure for removal of the contact lenses. This can be either in our clinic or with your optometrist.

Vision is quite good after a few days but improves over the next few weeks and months.

Eye drops are used for two weeks and lubricants for 6-12 months

How long does ASLA last?

Generally, this correction is permanent. However as we age, our bodies (and eyes) change. This may lead to a change in your need for glasses long term. This can be corrected at a future date with an enhancement using the laser, or if the change is only small, glasses or contact lenses.

Some people do experience regression, which is where some of the original myopia or hyperopia returns. If this occurs, an enhancement can be performed once the regression stabilises.

How do I  decide wether to have LASIK or ASLA?

This decision is not one that you need to make yourself, rather your particular set of circumstances will govern which approach is best for you

Long term safety of ASLA

ASLA is generally safer than LASIK although both are safe.This is because less corneal surface is removed with ASLA. With LASIK, the flap is usually around 120 microns in thickness which does not contribute to the structural integrity of the cornea. Hence, corneas that have had ASLA have a thicker residual base with consequent less long term risk of complications




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The latest technology for laser vision correction

Another day, another upgrade!  We have now upgraded the laser that we use for vision correction to the new Schwind Amaris. Our previously laser was the Bausch & Lomb Zyoptics which served us well for many years.

The Intralase, which  is a femtosecond laser that creates the Lasik flap has also been upgraded to the latest generation machine which means that the flap creation is now much faster.

The new Schwind is the laser that actually performs the refractive correction.

So what is soo good about the new laser? Well amongst other things, it is capable of performing a transepithelial PRK which the B&L machine could not do.

How is PRK different to LASIK?

PRK has had a resurgence in recent years as LASIK surgeons realised that not all patients were suitable for LASIK yet many could still be helped with PRK. PRK of course became unpopular because of its slow visual recovery and postoperative pain. It is no surprise that when LASIK came along with no pain and virtually instant recovery that it quickly became the default leaving PRK behind. PRK however has its advantages in that the absence of the LASIK flap means an instant saving of 120 microns of cornea that does not contribute anything to the structural integrity of the cornea. This means that anyone who has a thin cornea may not be able to have LASIK but may well be able to have PRK. The goal is to leave enough cornea after the vision correction to minimise any future problems such as ectasia. In addition, there are a number of potential flap related complications  that clearly do not apply with PRK.

How does the new laser remove the epithelium? Transepithelial PRK

Traditionally, the epithelium is removed prior to laser either by alcohol of by manually scrapping it of. Some surgeons use a motorised brush.

With the new transepithelial laser however this is no longer required. The epithelium is now automatically removed by the laser.

The way that the laser performs this is by using an algorithm that determines how thick the epithelium is that is required to be removed.

The result is a much neater epithelial removal without the increased risk of recurrent erosions which are associated with alcohol removal.

Curiously, we have observed that the pattern of pain following the procedure is also different. It is not less, but most would complain of discomfort mainly on the second day after the procedure whereas now the peak comes a day earlier. It still however seems to last about 2.5 days.

Visual recovery seems no different.

The new Intralse

The femtosecond laser which is used to create the LASIK flap has also just been upgraded to the latest model. This new laser runs at a higher frequency which means that it is able to complete the flap much faster which in turn means that problems such as loss of suction are less likely to occur.

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