Phaco after RK poses various challenges

February 15, 2006

As the early adopters of the older keratorefractive procedure radial keratotomy (RK) are aging and developing progressive hyperopia and cataracts, it is increasingly important to master safe and effective ways to treat these patients.

Linear RK incisions were typically made in a spoke-like pattern extending from a 3- to 4-mm central optical zone peripherally to within 1 to 2 mm of the limbus. The incisions were made to 90% to 95% corneal stromal depth and numbered from two up to 32 or higher in some extreme cases. Most spherical myopic RK treatments involved four to 16 radial incisions arranged in a symmetric wagon-wheel-spoke pattern over the cornea. Various incisions for the treatment of astigmatism were often added as T-cuts or other small concentrically arranged incisions placed between and perpendicular to the radial cuts.

Key to success

The key to surgical success in these post-RK patients is to minimize crossing of phaco incisions and RK incisions. If a clear corneal phaco incision is made through an RK incision, there is a high likelihood that the roof of the phaco incision will split open along the RK incision due to manipulation during the course of the procedure. The split roof of the clear corneal incision will prevent a good seal at the incision and allow excessive outflow of fluid and consequent chamber instability during phacoemulsification. An unstable chamber can lead to multiple complications, including iris damage, endothelial damage, and vitreous loss. A split incision roof can also lead to difficulty in closing the corneal incision at the end of the case. Often multiple sutures are required to achieve a watertight closure. The added sutures can create astigmatism and patient discomfort. A poorly sealing corneal incision may also increase the risk of endophthalmitis.