Some Basics Of PRK Or Eye Surgery

The original form of laser surgery is known as PRK (photo-refractive keratectomy), and established the prototype for using a laser to re-shape the eye by removing fine layers of tissue.

The Excimer laser removes part of the surface of the cornea (the clear front part of the eye), so light can focus properly on the retina, giving near-perfect vision. The PRK operation, which costs about 700 per eye, usually causes some pain and there is a long recovery time. Each eye must be done separately, several months apart.

However PRK has long since been overtaken by a more popular form of treatment known as Lasik (laser assisted in-situ keratomileusis) which combines the use of microsurgery and laser treatment.

With Lasik, microscopic amounts of tissue are removed from deep within the cornea, not from its surface and this leads to a change in the focusing ability of the eye. To achieve this, the top layer of the cornea is cut and pulled back as a hinged flap, so the laser can operate on the inside of the cornea. The flap is then put back.

This treatment, which costs between 800 and 2,000 per eye, is normally used for moderate to severe short sight. A patient should be healthy, over 20 and have eyesight that has not changed significantly in the past few years.

Comparison of LASIK with PRK

In a fellow eye-controlled comparative trial, both LASIK and PRK produced similar patterns of refractive change over time, but LASIK was associated with less pain, quicker visual rehabilitation, and fewer visual complications.

Comparison of preoperative features showed no statistically significant differences between the two treatment groups. Spherical equivalent (S.E.) for the study eyes ranged from -2.3 to -8.1 D with mean S.E.s of -4.7 D in the PRK eyes and -4.8 D in the LASIK eyes. Uncorrected visual acuity was 20/100 or worse in 80% of the eyes in each group at baseline while approximately 80% of the eyes in each group had preoperative best corrected visual acuity of 20/20 or better. Visual acuity with the Brightness Acuity Tester (BAT) showed 20/20 or better vision in 62% of the LASIK eyes and 68% of PRK eyes.

Evaluation of serial postoperative mean S.E. showed similar patterns of refractive change in both groups, characterized initially by overcorrection and then regression to near emmetropia at 3 months. From 6 months on, S.E. remained relatively stable in each group although the PRK eyes were slightly undercorrected and the LASIK eyes slightly overcorrected. The difference in mean S.E. between groups was about 0.25 D.