Predicting postoperative astigmatism using Scheimpflug keratometry (Pentacam) and automated keratometry (IOLMaster)

Purpose: To compare keratometry measurements obtained using an automated keratometer (AK, IOLMaster) and a Scheimpflug keratometer (Pentacam) in predicting residual astigmatism after cataract surgery. Methods: Preoperative corneal astigmatism was calculated using preoperative refraction, an AK and a Scheimpflug keratometer (anterior corneal power [ACP] and true net power [TNP]) in 155 eyes of 107 Asian subjects. Phacoemulsification cataract removal and nontoric intraocular lens insertion (Akreos^®MI-60 ^™, Bausch & Lomb, Rochester, NY, USA) were performed through a 2.8mm temporal clear corneal incision. Six months later, postoperative astigmatism (postA) was calculated using manifest refraction. Error angle (EA) and error magnitude (EM) of above keratometries (AK, ACP, and TNP) in prediction of postA was calculated. The correlation between preoperative astigmatism and postA was analyzed using power vectors (J0 and J45). Results: AK resulted in the lowest EM and ACP resulted in the lowest EA. Preoperative astigmatism (preA) measured using AK, ACP, and TNP showed significant correlation with postA in both J0 and J45 components. (AK: rJ0 = 0.554, rJ45 = 0.559, ACP: rJ0 = 0.346, rJ45 = 0.281, TNP: rJ0 = 0.409, rJ45 = 0.231). Preoperative refractive astigmatism showed no significant correlation in any components. Conclusions: PreA determined using AK showed superior performance in prediction of postA than ACP and TNP.