1 Journal of Refractive Surgery • Vol. xx, No. x, 2012 ORIGINAL ARTICLE iometry is a basic and necessary examination that must be performed prior to cataract surgery. Ongoing improvement of intraocular lens (IOL) design (ac- commodating, multifocal, aspheric, astigmatic, etc) requires high precision biometry calculations. 1 Therefore, increased precision and accuracy of biometry measurements is essen- tial in any preoperative measurement. Biometry determines the refractive power of the IOL as well as its effective lens position and helps achieve the tar- geted postoperative refraction. To this aim, several preopera- tive data have to be collected to be included in formulae such as the Olsen, 2 Haigis-L, 1,3 Holladay 2, 4,5 and Hoffer Q. 6 These data include corneal refractive power (by measuring steep and flat meridian keratometry [K]) and ocular axial length. In addition, central corneal thickness (CCT, defined as the dis- tance between the anterior corneal surface and posterior cor- neal surface) and aqueous or anterior chamber depth (ACD, defined as the distance between the anterior corneal surface and anterior crystalline lens surface) are also measured by biometry devices. Central corneal thickness measurement is important for ensuring proper intraocular pressure correction in individu- als with increased glaucoma risk, and ACD measurement is important for its correlation with axial length and its associa- tion with increased risk for angle closure if the anterior angle is shallow, particularly for hyperopic individuals. BIOMETRY DEVICES The IOLMaster (Carl Zeiss Meditec, Jena, Germany) was the first US Food and Drug Administration–approved non- contact, optical biometry device to use partial coherence in- B ABSTRACT PURPOSE: To compare and correlate central corneal thickness (CCT), anterior chamber depth (ACD), and keratometric (flat and steep K) measurements using two anterior segment imaging methods, a Scheimpflug camera system (Oculyzer II [Oculus Optikgeräte GmbH]), and a partial coherence biometry system (WaveLight OB820 [Alcon Laboratories Inc]) in eyes undergoing cataract surgery. METHODS: Ninety patients (mean age: 6613 years [range: 32 to 88 years]) underwent preoperative mea- surement of central corneal thickness, anterior chamber depth, and keratometric measurements by Scheimpflug tomography (Oculyzer II) and optical low coherence re- flectometry (WaveLight OB820). Interdevice agreement and correlation between the two techniques were as- sessed. RESULTS: All measurements were highly correlated, and showed no clinically significant difference between methods. Mean CCT was 554.2139.07 μm and 546.5937.75 μm for the Oculyzer II and WaveLight OB820, respectively (R 2 =0.9268). Mean ACD was 2.630.44 mm and 2.630.43 mm for the Oculyzer II and WaveLight OB820, respectively (R 2 =0.9488). The principal meridian keratometric values were also highly correlated. Mean flat K was 42.881. 50 diopters (D) and 42.961.40 D for the Oculyzer II and WaveLight OB820, respectively (R 2 =0.8741). Mean steep K was 44.081.79 D and 44.261.95 D for the Oculyzer II and WaveLight OB820, respectively (R 2 =0.9159). CONCLUSIONS: Our data show that the Oculyzer II and WaveLight OB820 provide measurements that are in agreement with published values for CCT and ACD in patients. Excellent agreement for CCT and ACD was found between the two devices, as demonstrated by a high degree of correlation and linearity, in addition to minimal bias. Thus, CCT, ACD, and K measurements by these instruments can both be used in clinical prepara- tion, and their agreement is an ensuring precision fac- tor for cataract and refractive surgeons. [J Refract Surg. 2012;xx(x):xxx-xxx.] doi:10.3928/1081597X From Laservision Eye Institute, Athens, Greece (Kanellopoulos, Asimellis); and New York University School of Medicine, New York, New York (Kanellopoulos). Dr Kanellopoulos is a consultant to Alcon Wavelight. Mr Asimellis has no financial interest in the materials presented herein. Correspondence: A. John Kanellopoulos, MD, 17 A. Tsocha St, Athens, Greece 11521. Tel: 30 210 747 2777; Fax: 30 210 747 2789; E-mail ajk@brilliantvision.com Received: July 17, 2012; Accepted: August 30, 2012 Posted online: Correlation Between Central Corneal Thickness, Anterior Chamber Depth, and Corneal Keratometry as Measured by Oculyzer II and WaveLight OB820 in Preoperative Cataract Surgery Patients A. John Kanellopoulos, MD; George Asimellis, PhD