PRK Laser Types

Current PRK lasers are best classified by laser source (either Argon-Fluoride excimer lasers or solid state) and beam type (broad beam or scanning beam). Laser technology and computer control software has evolved significantly since the first normally sighted eyes were treated in 1987. Initial PRK treatments used 3.5 and 4mm optical zones so as to minimize the depth of ablation. Since many pupils dilate to 5mm it is not surprising that edge glare and light sensitivity were common complications. Ablation diameter increase with edge smoothing has been implemented to solve many edge glare problems. Wide or broad beam machines initially had problems caused by the use of nitrogen flow to disperse vaporized tissue and with the occurrence of unvaporized central islands. Stoppage of nitrogen flow and modification of computer generated treatment regimes has largely eliminated these problems.

The US Food & Drug Administration (FDA) has been cautious, rigid, and slow to approve PRK for widespread use within the USA. There has been speculation that the reason for the current caution is embarrassment over a previous premature approved of the surgical procedure of radial keratotomy (RK). Many observers have feared that the apparent bureaucratic rigidity might impede the implementation of future needed changes to equipment or procedures prior to long and inflexible testing schedules. However, recently the FDA surprised its critics when, with the final approval of the Summit Laser, they insisted upon increasing the size of the optical zone from that tested in the preapproval trials. In the US a number of other laser manufacturers are progressing or almost through FDA trials. In contrast, most other jurisdictions including Europe and Canada, have, without the "benefit" of as vigorous an approval process, had the freedom to amend and improve equipment and treatment regimes as improvements presented themselves. There is now worldwide a large and expanding experience with many varied laser machines and evolving technical improvements.