Simulated Experiments on IOL Power Calculation Using Anterior Segment OCT Dong Hyun Jo, M.D., 1,2 Mee Kum Kim, M.D., 1,2 Won Ryang Wee, M.D. 1,2 1 Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea, 2 Seoul Artificial Eye Center, Seoul National University Hospital Clinical Research Institute, Seoul, Korea Financial disclosure: All authors have no proprietary interest in methods described in this article.

Purpose To compare the method of calculating intraocular lens (IOL) power by anterior segment optical coherence tomography (AS-OCT) with the clinical history (Single-K) and Double-K methods

Methods Patients  who had undergone LASEK from July 1, 2009 to June 30, 2010 Preoperative and postoperative examinations  Best spectacle-corrected visual acuity  Intraocular pressure  Anterior and posterior segment examinations Slitlamp biomicroscopy Funduscopy Automated keratometry Anterior segement optical coherence tomography (AS-OCT) LASEK was performed using Visx Star S4 (VISX Inc., Santa Clara, CA).

Methods Methods of IOL power calculation: SRK/T formula  Double-K method: devised by Aramberri Preoperative keratometric value → anterior chamber depth (ACD) Postoperative keratometric value → the power of IOL  Single-K method: “Clinical history” method  AS-OCT method we utilized corneal height (C h ) as measured by AS-OCT in the IOL power calculation

Methods: AS-OCT method 1. A horizontal line was drawn to connect both ends of the anterior chamber angles 2. A vertical line was drawn from the posterior surface of the corneal vertex to fall on the horizontal line. 3. The length of the vertical line was designated as C h. 1 2, 3 ChCh

Methods Comparison of Ch according to myopic status before and after the refractive surgery  Low myopia (>-3 D)  Moderate myopia (≤-3 D, >-6 D)  High myopia (≤-6 D) Comparison of the results among 3 methods with each other

Results Demographic, Refractive, and Keratometric Data : 73 eyes of 37 patients

Results Comparison Between Preoperative and Posoperative C h According to the Preoperative Myopic Status Ch pre = preoperative corneal height; Ch post = postoperative corneal height; Δ Ch = difference between preoperative and postoperative cornealheight *P < 0.05

Results Corneal Height Estimated Using the Different Methods The differences between values obtained with AS-OCT method and those obtained with the other 2 methods were statistically significant (P < in both analyses).

Results Intraocular Lens Power Calculated Using the Different Methods P emme : IOL power to get emmetropia P emme obtained using AS-OCT method was higher than that obtained using the Single-K method lower than that obtained using the Double-K method. (P < in both analyses)

Conclusions We demonstrated that C h as measured by AS-OCT could be utilized in IOL power calculation after corneal refractive surgery.