Prevention and Treatment of Iatrogenic Keratectasia.

Iatrogenic keratectasia can occur as a postoperative complication following refractive laser surgery. Biomechanical weakening and the resulting steepening of the remaining corneal tissue lead to progressive myopia and irregular astigmatism, associated with a significant loss of visual acuity. The incidence of iatrogenic keratectasia is reported in the literature to range from 0.04% to 0.6%, with the risk being higher after KLEx and LASIK than after PRK. However, due to advances in preoperative diagnostic techniques and surgical procedures, incidence estimates from older studies may be only partially applicable to current clinical practice. Risk factors include a thinner cornea prior to surgery, higher myopia, genetic predisposition or undetected keratoconus. A detailed preoperative medical history and thorough clinical diagnosis are therefore very important for the prevention of iatrogenic ectasia. Precise measurement methods are available that enable a differentiated assessment of corneal topography, tomography and biomechanics. Scores such as the Ectasia Risk Score System (ERSS) and Percentage of Tissue Alteration (PTA) are used to estimate the postoperative risk of ectasia based on this information. Conservative measures such as the fitting of glasses or contact lenses are initially available for the visual rehabilitation of iatrogenic keratectasia. Corneal cross-linking is indicated particularly in cases of progressive ectasia. This procedure does not aim to improve vision immediately, but it can halt further progression. The safety and effectiveness of the procedure have been proven in various studies. Alternatives include the implantation of plastic corneal ring segments (ICRS), donor corneas (CAIRS) or, as a last resort, keratoplasty. The latest surgical method involves the implantation of stromal lenticles obtained from KLEx procedures. Overall, this is a complex disease, which is why, in addition to accurate preoperative diagnostics, regular postoperative check-ups after refractive laser surgery are recommended in order to detect and treat ectasia at an early stage.