By Shahzad I. Mian, MD
The results of this study suggest that femtosecond laser-assisted penetrating keratoplasty (PK) may improve wound integrity, thereby decreasing the need for sutures and facilitating earlier suture removal and faster recovery of vision. The authors assessed wound integrity by testing 22 human cadaver corneoscleral rims mounted on an artificial anterior chamber that had undergone full-thickness keratoplasty with the femtosecond laser. They experimented with multiple wound shapes and found that the femtosecond laser-assisted top hat wound configuration was the most mechanically stable compared with the traditional method and the so-called mushroom, zigzag, and Christmas tree configurations.
The use of lasers for trephination in keratoplasty was proposed more than 15 years ago. The theoretical advantages of automated trephination include elimination of axial and tangential contact forces, reduction of donor-host disparity and subsequent corneal curvature irregularity, and minimization of trauma to intraocular tissue. A focusable infrared laser that uses ultrafast pulses in the femtosecond (10-15 second) duration range, the femtosecond laser is currently used in the United States during LASIK surgery for creating anterior corneal flaps and during lamellar dissection for anterior lamellar keratoplasty. With its energy release and firing pattern controlled by computer, the femtosecond laser is capable of cutting tissue at various depths and patterns, producing minimal inflammation or collateral tissue damage. It uses low energy coupled with higher power pulses to rapidly perform trephination. Unlike lasers employing visible wavelengths, the ability of the femtosecond laser to cut cornea is less hampered by optical haze, making it more useful in treating edematous corneas.
The laser-control software is customizable, enabling the cutting of grafts in different geometric configurations and potentially allowing for sutureless self-adhesive keratoplasty. The femtosecond laser-assisted PK application allows a posterior side cut, lamellar cut, and anterior side cut in both the host and donor corneas. These cut types can also be combined to create patterns for shaped keratoplasty, including a top hat pattern (which has a larger diameter cut posteriorly), mushroom pattern (with a larger diameter cut anteriorly), zigzag pattern, and Christmas tree pattern (which has a tongue and groove).
The authors of the current study assigned five samples to each of the traditional PK, top hat, and mushroom wound configurations and four samples to the zigzag and Christmas tree configurations. Wound bursting pressure was evaluated after placement of four, eight, and 16 sutures. In the traditional PK group, leakage occurred at 0 ± 0, 21.6 ± 2.5, and 49 ± 6.6 mm Hg after placement of four, eight, and 16 sutures, respectively. No statistically significant difference was noticed in burst pressure with the zigzag and Christmas tree wound configurations compared with the traditional PK group. In the top hat and mushroom groups, burst pressure was significantly higher, measured at 102 ± 16.8 mm Hg and 65.8 ± 5.3 mm Hg, respectively, after placement of 16 sutures.
Financial Disclosures
Dr. Mian has no financial interests to disclose.