A simple and accurate method of alignment for toric intraocular lens implantation using anterior segment optical coherence tomography (OCT). Kazuno Negishi, MD1, Kazuhiro Watanabe, MD1, Hidemasa Torii, MD1, Chiyo Kodama,CO1, Murat Dogru, MD2, Kazuo Tsubota, MD1 1. Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan 2. J&J Ocular Surface and Visual Optics Department, Keio University School of Medicine, Tokyo, Japan The authors have no proprietary interest in any of the devices mentioned in the manuscript. Purpose To report a simple method for accurate alignment of the IOL axis for toric intraocular lens implantation using anterior segment OCT. Setting Department of Ophthalmology, Keio University Hospital, Tokyo, Japan. Patients • 9 consecutive eyes of 7 patients who had cataract extraction and implantation of an acrylic toric IOL (SA6AT3, SA6AT4, or SA6AT5, Alcon, FortWorth, TX) • Inclusion criteria – Postoperative visual acuity better than 20/20 • Exclusion criteria – previous or coexisting ocular pathology and intra- or postoperative complications. – Eyes with a corneal astigmatism of less than 0.75 D • All patients provided written informed consent. The study adhered to the tenets of Declaration of Helsinki. • IRB approved this study. METHODS 1. IOL Power calculation and style selection – – – – Biometry using the IOL Master (Carl Zeiss, Germany) SRK/T formula Specific A constant for the toric IOL : 119.0. The online Acrysof Toric IOL Calculator (http://www.acrysoftoric calculator.com). 2. Preoperative acquisition of corneal topography using the anterior segment OCT (corneal map mode). 3. Determination of the steep meridian of corneal astigmatism from corneal topography. Anterior segment OCT (CASIA, Tomey, Japan) METHODS (continued) 4. Eye image acquisition after full pupillary dilatation using the anterior segment OCT (anterior segment mode). 5. Selection of the characteristic iris pattern on the peripheral cornea as a reference axis. (Figure 1 in the following page). – The line of the slice plane direction can be freely rotated around the corneal apex by mouse on the CCD image, thus the rotation degree of any point can be displayed on the rotational view. The rotational degree of reference axis including the reference point was measured using this rotational view . 6. Intraoperative marking of the steep axis (Figure 2 in the following page) and implantation of the toric IOL 7. Evaluation of the rotation error of the implanted toric IOL (Figure 3 in the following page) Figure 1 Preoperative determination of the reference point and the alignment axis using Acrysof Toric Calculator and the anterior segment OCT 90 degrees Reference point 53° Alignment axis 143° Characteristic iris pattern as a reference point CCD image Rotational view Figure 2 Intraoperative marking of the steep axis and implantation of the toric IOL 1. Marking of the reference point At the beginning of the surgery, previously determined reference point was marked by a surgical marker-pen under the operating microscope observing the characteristic iris pattern. 2. Marking of the alignment axis The zero degree of the Wallace Mendez degree gauge was fit to the reference point, and the alignment axis was marked using the DK axis marker according to the difference between the reference and the alignment axes. Figure 3 Postoperative evaluation of the rotation error of the implanted toric IOL Dot marks on the toric IOL Postoperative CCD image (example) Rotational view Results Pre-op Age(yrs) Corneal astigmatism(D) Subjective astigmatism(D) Subjective refraction(D) (Spherical equivalent) UCVA (Log MAR) BCVA(Log MAR) Rotation error in the achieved from the target axis of the toric IOL (Degree) Post-op(1w) Mean (SD) 73.3 ( 7.8) 1.97 ( 0.66) 2.00(0.67) -1.50(1.88) 1.97(0.43) 0.28 ( 0.25) 0.16(0.48) 0.69(0.37) 0.16(0.17) N/A -0.01(0.16) -0.09(0.11) 1.9 ( 2.0) N/A: not applicable Discussion • Advantages of this method – Simple and accurate – Free from the misalignment related to marking the reference point due to the differences in the head position at the time of topography and the time when the reference point is marked, including cyclorotation of the eye during surgery. – Reference and alignment axis can be marked under the surgical microscope (only 2 step for marking) – Not required to take a photo, or to use image analysis software • Limitation of this method – Necessity of an apparatus that can obtain images of iris patterns with the axis scale and the corneal topography at the same time. – Not applicable for an eye without any characteristic iris pattern (rare). Conclusions • The current method enables a simple and accurate marking of reference and alignment axes for toric IOL implantation, and is useful for correct placement of toric IOLs.