- Ophthalmic Surgery, Lasers and Imaging
- January/February 2011 - Volume 42 · Issue 1: 45-52
Background and Objective:
The purpose of this study was to examine the hypothesis that retinal nerve fiber layer (RNFL) birefringence increases following surgical reduction of intraocular pressure (IOP).
Patients and Methods:
Twenty-six glaucomatous eyes requiring trabeculectomy or drainage implant were enrolled. Optical coherence tomography (OCT), scanning laser polarimetry (SLP), and IOP measurements were performed preoperatively and 3 months postoperatively. The OCT and SLP images were aligned using a new algorithm that aligns the vessels in an OCT image to those in the corresponding SLP reflectance image. The SLP retardance values at the location of the OCT scan circle were then extracted using the OCT scan circle position inferred by the algorithm. Sixty-four corresponding RNFL segments were extracted from SLP and OCT to calculate RNFL birefringence. A significant birefringence change was defined as 1.96 times the weighted test–retest standard deviation in four contiguous segments.
Preoperative IOP (19.3 ± 6.1 mm Hg) was significantly (P < .001) lower than postoperative IOP (10.4 ± 3.7 mm Hg). Average birefringence magnitude did not change (P = .19) postoperatively. Localized birefringence magnitude increased significantly in 6 (23%) eyes and decreased significantly in 7 (27%) eyes.
In this cohort, variable changes in localized birefringence were observed following surgical reduction of IOP.
From Bascom Palmer Eye Institute (MS, DSG, WJF, DSG), Department of Ophthalmology, University of Miami Miller School of Medicine, Palm Beach Gardens, Florida; and the Department of Optometry and Visual Science (HZ), City University London, London, United Kingdom.
Presented in part at the annual meetings of the American Glaucoma Society, March 6, 2009, San Diego, California, and the Association for Research in Vision and Ophthalmology, May 6, 2009, Fort Lauderdale, Florida.
Supported in part by the Maltz Family Endowment for Glaucoma Research, Cleveland, Ohio; a grant from Mr. Barney Donnelley, Palm Beach, Florida; The Kessel Foundation, Bergenfield, New Jersey; and unrestricted grants from Research to Prevent Blindness (P30-EY14801), National Institutes of Health (R01-EY013516), and Allergan Inc.
Dr. Greenfield has received research support from Carl Zeiss Meditec and has acted as a consultant for Allergan Inc. The other authors have no financial or proprietary interest in the materials presented herein.
Address correspondence to Mitra Sehi, PhD, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, 7101 Fairway Drive, Palm Beach Gardens, FL 33418. E-mail: firstname.lastname@example.org