Laser vision correction: the latest

An important concept when recommending laser vision correction to patients is that all options to correct future changes to the patient’s refractive status must remain available. In other words, the future errors must be able to be corrected by glasses and/or contact lenses and even by additional laser.

Another relatively important principle is that patients must have realistic expectations of what laser vision correction can deliver. They should be careful of the 100% or 20\20 vision guarantee. Patients who benefit the most from the procedure are the most informed ones and those who look forward to a lifestyle improvement rather than 'eagle vision'.

Finally, it is impossible to tell patients how long their laser procedure will last. Stability of refractive errors depends largely on two concepts:

• Genetics – the level of myopia (nearsightedness) depends on the length of the eyeball, which in turn is determined by one's genes.
• Gravity – astigmatism (oval-shaped cornea) increases with time as ageing tissue succumbs to the effects of gravity.

As a result, patients can be told that if refractions have been stable for two or more years, it can be assumed but not guaranteed, that the laser result should last at least 10 years.

New developments
Aspheric corneas and wavefront technology:
All expensive professional cameras have aspheric optics in their lenses, which result in superior quality pictures.

Wavefront optics and consequent wavefront analysis of normal corneas have revealed the fact that Mother Nature has created aspheric corneas in binocular predators. The result is excellent contrast sensitivity in most light conditions.

Wavefront-generated aspheric treatments not only result in excellent vision in good light, but also excellent vision in poor light with a marked reduction in glare and haloes (a common complaint following the older non-wavefront lasers).

Screening:
Pre-operative screening by refractive specialists using wavefront and ORBSCAN analysis achieves the following goals:

• Patient suitability.
• An indication of post-operative outcome, i.e. whether patients’ expectations can be met.

Automatic tracking device:
Modern laser treatments are performed by a scanning laser system, under automatic tracking device control.

The gentle laser sculpturing of the corneal surface is not only safely achieved (the tracker follows small involuntary eye movements), but creates optically perfect profiles accurate to 0,25 microns.

Safety limits:
Experience gained over the past 15 years has determined safety limits for laser vision correction.

The maximal myopia (nearsightedness) treatment is -10.0 diopters, maximal astigmatism (oval-shaped cornea) treatment is -7.0 diopters and the maximal hyperopic (farsightedness) treatment is +4.5 diopters.

Lasik technique:

• Laser ablations are customised (wavefront generated) and/or aspheric in design and are performed in the stromal bed beneath the flap.
• New generation keratomes (machines which create corneal flaps) have advanced safety features, which result in reduced complications during the flap creation.

PRK technique:

• This technique has been modernised by the following advancements: gentle removal of the epithelium (brushing or epilasik), modern anti-inflammatory medication, bandage contact lenses and wavefront-guided treatments.
• The above modifications have resulted in a markedly improved recovery period, both in terms of discomfort levels and return to functional vision.

- (Dr Mark Deist, ophthalmic surgeon, Sandhurst Eye Centre, September 2006)

For more information, contact Dr Mark Deist on (011) 217 7520 or visit www.drdeist.co.za.

Read more:
LASIK: What to ask your surgeon
Can I have laser eye surgery?

Useful resources:
South African Optometric Association
Tel: 011 805 4517
South African National Council for the Blind
Tel: 012 452 3811
Retina South Africa
Tel: 011 622 4904
Ophthalmological Society of South Africa