contact lens case reports
Astigmatic Reduction in Penetrating Keratoplasty
BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRÉ, FAAO
High postoperative astigmatism continues to be the number-one complication in penetrating keratoplasty. Postoperative management of this astigmatism has involved selective removal of interrupted sutures or tension adjustment of running sutures, relaxing incisions, wedge resections, and laser-assisted wound modification.
However, the most common wound modification technique is relaxing incisions. In this procedure, deep, arcuate incisions are placed across the steep corneal meridian in the peripheral area of the donor (not the host) cornea. These relaxing incisions flatten the steep corneal meridian based on the wound gape model in which incisions into the paracentral or peripheral cornea create wounds that gape open under the force of the intraocular pressure (IOP) and internal stresses within the corneal tissue.
These unsutured, gaping incisions are first filled with an epithelial plug and finally with scar tissue to flatten the cornea (Figure 1). The amount of wound gape and the subsequent corneal flattening will be influenced by a number of biological and surgical factors that include patient age; number, length and depth of the incisions; preoperative shape factor; IOP; stresses and biochemical properties within the corneal tissue; and individual wound healing response.
Figure 1. The left image shows an epithelial plug formed within the walls of the gaping wound. With time, the plug is pushed out and replaced with scar tissue.
A Successful Outcome
This month's case involves a 32-year-old male who underwent penetrating keratoplasty to his left eye for keratoconus. Postoperatively he had 12.50D of against-the-rule astigmatism (Figure 2). Numerous fitting attempts with a wide range of contact lenses failed to provide the patient with adequate comfort and/or vision. The patient was referred back to his surgeon for an astigmatic reduction procedure and underwent a relaxing incision in 2008, which reduced his astigmatism to 3.00D (Figure 3). Today, he wears a high-Dk GP lens on his left eye with 20/20 acuity and all day comfort.
Figure 2. The patient's left eye pre-corneal topography with 12.50D of against-the-rule astigmatism and post-relaxing incision topography with 3.00D of astigmatism.
Figure 3. Slit lamp view of the patient's relaxing incisions along the steep corneal meridian.
While the results of relaxing incisions can be somewhat unpredictable, this case clearly demonstrates the dramatic reduction in astigmatism that is possible through this relatively simple technique. CLS
Patrick Caroline is an associate professor of optometry at Pacific University. He is also a consultant to Paragon Vision Sciences. Mark André is an associate professor of optometry at Pacific University. He is also a consultant for CooperVision.