Reasons to consider refractive
- A desire to maintain a lifestyle that
would be hampered somewhat by wearing glasses or contacts.
- Wearing glasses or contacts might be a
handicap in certain occupations- pilot, sportsman, etc.
- Many people who would be satisfied
with contacts have difficulty in wearing them for various reasons.
Advantages of surgery
- After high initial cost there is no
- Greater freedom for sport and leisure.
Disadvantages of surgery
- Irreversible (canít "try it to
- Possible loss of quality of the best
corrected vision, e.g. may be a line or two less good on a letter
chart, or may find a loss of sharpness driving at night.
- Any surgery carries a small degree of
risk- "disasters" have, very rarely, occurred.
Types of surgery
There are now a variety of different
options available to the surgeon- the most common methods are PRK and
PRK (Photorefractive Keratectomy)
The key element is the excimer laser.
The laser focuses a powerful, minute beam
of "cold" energy on a microscopic target without affecting the
The surface of the cornea is treated
after the first few layers of cells have been removed using alcohol.
The purpose of the PRK procedure is to
change the shape of the cornea as required to correct the refractive
It does this by the precise sculpting of
layers of tissue from the central zone (visual axis of the cornea).
These layers are less than the thickness
of a human hair.
The operation of the laser is computer
controlled in accordance with a precise pattern based on extensive
preoperative tests and evaluations.
The results are fed into the computer by
the surgeon or expert technicians.
The computer then determines the extent
and depth of sculpturing or ablation of corneal tissue required to
correct the refractive vision problem.
This information guides the surgeon in
the operation of the laser.
- There are no corneal flap risks.
- Extremely high predictability for low
degrees of myopia
- Risk of infection (1/1000-1/3500).
- Post-surgical pain is greater.
- Scarring/healing haze 1-5%.
- Visual recovery takes 1-2 weeks.
- Steroid drops may be needed for up to
six months with the attendant risks associated with that.
- Bilateral surgery on the same day is
inadvisable as 95% of complications with PRK occur postoperatively.
LASIK (Laser In-Situ Keratomileusis)
In LASIK the eye surgeon uses a
sophisticated, automated surgical instrument known as a microkeratome.
This is used to slice a micro-thin,
disc-shaped flap from the top layer of the central zone of the cornea.
This flap is then held out of the way
whilst the excimer laser is used to sculpt the underlying corneal tissue
to the degree required to flatten its shape and thereby correct the
The flap is then replaced and allowed to
heal without the use of sutures.
- Low risk of infection (1/5000).
- Very little incidence of post-surgical
- The risk of haze is less than 0.2% for
all degrees of correction.
- Visual recovery is quick (1-7 days)
some patients have had it done in their lunch hour!
- Steroid drops may only need to be used
for a week.
- Although it is advisable to correct
one eye, then, a few days later, the other, most clinics now seem to
do both eyes simultaneously.
- A cut is involved which adds to the
risk of a serious complication.
- Although LASIK is generally considered
the best procedure for high myopes (>-6.00D), in some cases not
all the myopia may be corrected.
Pre-requisites for laser surgery
- Aged 21+.
- Stable refractive error.
- Contact lenses must be left out for at
least one month.
- No eye condition or disease present.
- Good sight in both eyes.
- No thin corneas are operable with