Anterior segment optical coherence tomography

Anterior segment optical coherence tomography (AS-OCT) is a useful adjunct to preoperative planning for cataract surgery, helping to delineate anterior chamber structures and reduce biometry errors leading to inaccurate intraocular lens (IOL) power calculations, according to a study. “Our study showed that a combination of axial length (AL), lens meridian parameter (LMP) and posterior lens thickness (PLT) measurements obtained using AS-OCT (CATALYS® Precision Laser System, AMO) showed the best predictability in both effective lens position (ELP) and refractive outcomes,” said Choun-Ki Joo MD, PhD. He added that a new IOL formula which takes account of LMP and PLT should prove helpful for enhancing predictive accuracy of IOL power calculations in cataract surgery. While various parameters such as anterior chamber depth (ACD), crystalline lens rise and anterior chamber angle are typically used in IOL power calculations, the CATALYS® AS-OCT system enables even more sophisticated criteria to be taken into consideration, said Dr Joo. “We know that the prediction of effective lens position (ELP) is one of the most important processes in IOL power calculation. With this device, we can measure and predict the exact ELP, drawing on parameters such as LMP and LT for more precise power calculations,” said Dr Joo, The Catholic University of Korea, Seoul, South Korea. He added that more recent IOL formulas such as Holladay 2, Hoffer-5, Olsen and New Shammas all include lens thickness measurements as a parameter for ELP. Dr Joo’s study included 92 eyes with a mean patient age of 67.1 (+-9.7 years) scheduled for cataract surgery and single-piece IOL implantation. Refractive outcomes were measured by manifest refraction at 3 months postoperatively with calculation of the difference between expected refractive error (RE) and real RE. The ELP was back-calculated using vergence formulas. Preoperative AL was measured by the partial coherence interferometry (IOLMaster), while aqueous depth (AD), ACD, LT and LMP were all measured by the CATALYS® AS-OCT. Dr Joo’s analysis compared the prediction errors from the various combinations of biometric data in order to establish the optimal approach to IOL power calculations. “From all the various combinations we found that the combination of AL, LMP and posterior LT showed the best predictability both in terms of ELP and refractive outcomes,” he concluded. Summing up, Dr Joo said that 3D measurements obtained by AS-OCT http://www.eurotimes.org/remote-oct-novel-probe/ will enable improved biometric pre-operative evaluations for cataract surgery, with more accurate ELP measurements leading to better IOL power selection for patients.   Choun-Ki Joo: ckjoo@catholic.ac.kr