Management of Post-Penetrating Keratoplasty Astigmatism

Penetrating keratoplasty (PK) has emerged as a relatively safe means of restoring vision in corneal opacities and irregularities. Astigmatism is the most common cause of suboptimal vision after corneal transplantation despite a clear corneal graft.1,2 Based on several studies,3615%–31% of patients undergoing PK may develop postoperative astigmatism greater than 5 diopters (D). The astigmatism can be irregular with associated higher-order aberrations that can ultimately limit the vision obtained and add to patient’s inability to wear standard optical correction.7 This explains why visual acuity in 10%–20% of PK cases cannot be corrected satisfactorily by spectacles or contact lenses.8-10 Factors influencing the amount of astigmatism after PK include the severity of the underlying disorder (e.g. keratoconus), oval or eccentric trephination,11 graft size and donor–recipient disparity,12 corneal thickness mismatch between the donor and recipient,13 a poor suturing technique,13, 14-17 and time of suture removal or adjustment14-17. Commonly practiced techniques to reduce post-PK astigmatism consist of postoperative suture manipulation including running suture tension adjustment and selective interrupted suture removal,14,18-21 optical correction consisting of spectacles and contact lenses,22 relaxing incisions,2,10 compression sutures,2,23 a combination of relaxing incisions and compression sutures (augmented relaxing incisions),24-26 laser refractive surgery,27-33 insertion of intrastromal corneal ring segments,34 wedge resection,9,35-39 toric phakic intraocular lenses,4042 and finally regrafting.43