Alloplastic refractive keratophakia: A comparison of predictive algorithms

The predictability of alloplastic refractive keratoplasty has been examined using several different optical analyses in the monkey model. Predictions of the power changes provided by the surgery were calculated using: 1) a back vertex power algorithm (“sandwich” algorithm), 2) paraxial ray tracing, and 3) meridional ray tracing. The measured refractive change caused by hydrogel implants within microkeratome and pocket incisions and polymethylmethacrylate and Udel® polysulfone implants within pocket incisions were compared to the results of the various optical analyses. The “sandwich” algorithm proved most effective in predicting the results of both hydrogel techniques, while the paraxial ray trace best predicted the semirigid implant results.