Page 70 - The Book Pi in eye

Rajesh Khanna, MD

As the PERK or Prospective Evaluation of Radial Keratotomy
study had found that the cornea continues to become weaker and
flatter over the years after RK. The eye therefore continues to move
from nearsightedness to farsightedness. The amount of diurnal
fluctuation and progression towards hyperopia is proportional to the
number of incisions made on the cornea and the thickness of cornea.
Consequently the cornea, which has suffered 16 incisions, would be
worse off than that which underwent only 4. Believe it or not some
crazy barber surgeons made 32 or even more incisions on cornea.
These corneas end up becoming weak and irregular in shape.
If we have to be successful with Prelex in such patients we have
stabilize the fluctuations in vision and the drift towards progressive
hyperopia. This can simply be achieved by aiming to make the eye a
little nearsighted and let it progressively improve with passage of
times. One eye may be made more nearsighted so as to achieve
immediate functionality. The eye which is made which is aimed more
towards zero can be made more spherical in future by laser.
There are many techniques available to decrease the fluctuation of
post RK cornea. The incisions can be freshened and sutured. The
gaps may also be filled with biological glue to increase the adhesion.
A newer technique of crosslinking uses riboflavin activated by UV
radiation to stiffen the cornea.
One or a combination of these techniques may be utilized to
achieve the desired result. These procedures can be used in
conjugation with pi in eye.

What is AK?

Astigmatic Keratectomy is a transverse incision made in the mid-
periphery of cornea to treat astigmatism. The incision is made in the
steeper axis to relax the fibers and change the shape from oval to
spherical.

What is LRI?

Limbal Relaxing Incisions- when AK is performed along the
cornea margin. These incisions are longer and more stable; less
effective but there are fewer side effects.

64