Postkeratoplasty Astigmatism

Abstract

The success of penetrating keratoplasty in terms of graft survival is excellent but visual rehabilitation continues to be a significant issue primarily due to astigmatism. Factors contributing to postoperative astigmatism can be related to preoperative etiology, suturing techniques and the postoperative healing process and timing of surgery. The large number of options available to address postoperative astigmatism only serves to highlight the complex nature of the problem. This review offers an up-to-date account of the various options available to manage postkeratoplasty astigmatism. Spectacles and rigid gas-permeable (RGP) contact lenses offer the earliest and easiest forms of visual rehabilitation. Spectacle correction may be limited by astigmatic anisometropia. Rigid gas-permeable contact lenses are an effective alternative to spectacles but limited by fitting and handling issues. Suture adjustment and suture removal are the initial options for reducing postoperative astigmatism. Careful attention to suture techniques intraoperatively and timely removal of appropriate sutures in the postoperative period can decrease astigmatism to tolerable levels. For the management of residual astigmatism after suture removal, a plethora of choices exist. Relaxing incisions, astigmatic keratotomy, compression sutures and wedge resections are well explored techniques offering effective but unpredictable results. Photorefractive keratectomy and laser in situ keratomileusis are newer options available to correct both spherical and astigmatic errors, but outcomes are variably affected by the healing process. The current availability of phakic and toric intraocular lenses has also been explored for the correction of postkeratoplasty astigmatism with promising results. Intra-corneal ring segments used for the management of astigmatism in keratoconus finds a new application in postkeratoplasty astigmatism. The femtosecond laser has opened up ways to perform procedures such as astigmatic keratotomy, the placement of intra-corneal ring segments, and creation of flaps for laser in situ keratomileusis, with very good precision and accuracy.