EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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18 EW NEWS & OPINION October 2013 2013 ASCRS•ASOA Symposium & Congress Best Papers of Session The ASCRS•ASOA Symposium & Congress provides a stage for glaucoma experts to share strategies for optimizing glaucoma surgeries and diagnostic techniques. While the research topics cover a range of interesting technological developments in the field of glaucoma, the common thread is a focus on safe and effective techniques to evaluate and treat glaucoma. Murray A. Johnstone, MD, describes a phase OCT system that can measure pulse-induced trabecular meshwork movement in living humans and may eventually allow us to determine which patients might best benefit from trabecular bypass surgery. Julie Schallhorn, MD, presented data on more than 90,000 refractive surgery patients and demonstrated that myopic and hyperopic laser vision correction with both PRK and LASIK does indeed change IOP measurements and that each procedure has its own distinct influence. Sayoko E. Moroi, MD, reviewed canaloplasty procedure outcomes to determine whether a postoperative hyphema, often thought to be a good sign indicating surgical success, had any predictive value. –Nathan M. Radcliffe, MD, glaucoma editorial board member Pulse-induced trabecular meshwork movement in humans characterized by phase-sensitive OCT Murray A. Johnstone, MD, Peng Li, PhD, Ruikang Wang, PhD Aqueous flows from Schlemm's canal to the aqueous veins by cyclic pulsatile mechanisms that depend on trabecular meshwork (TM) move- ment. Pulsatile excursions of the TM into Schlemm's canal displace sufficient aqueous volume to account for all of aqueous outflow.1 Movement of the TM becomes abnormal in glaucoma. Phase OCT (PhS-OCT), a new technology pioneered by Ruikang Wang at the University of Washington, Seattle, detects nanometer scale motion. We report detection and measurement of pulse-induced TM movement in 20 eyes of 10 human subjects.2 A digital pulsimeter signal was synchronized with a PhS-OCT TM motion signal. PhS-OCT imaging detected and measured TM movement that was highly correlated with the cardiac pulse. TM motion strength, harmonics and velocity were characterized. PhS-OCT may provide a sensitive new clinical tool for monitoring development and progression of aqueous outflow system biomechanical abnormalities that lead to IOP elevation in glaucoma. 1. Peng, L. Reif, R. Zhi, Z. Martin, E. Shen, T. Johnstone, M. Wang, R. Phase-sensitive optical coherence tomography characterization of pulse-induced trabecular meshwork displacement in ex-vivo non-human primate eyes. Journal of Biomedical Optics 17:076026-1 076026-10, 2012. 2. Li P, Shen T, Johnstone M, Wang R. Pulsatile motion of the trabecular meshwork in healthy human subjects quantified by phase-sensitive optical coherence tomography. Biomedical Optics Express. 2013;4:2051-2065. Changes in intraocular pressure after refractive surgery Julie Schallhorn, MD, Steve C. Schallhorn, MD, Yvonne Ou, MD We performed a retrospective chart review of 91,024 patients undergoing hyperopic and myopic laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) as a primary refractive procedure. The average preoperative central corneal thickness (CCT) was 546±33 μm, the average preoperative intraocular pressure (IOP) was 15.2±9 mm Hg. The relationship between preoperative IOP and preoperative pachymetry was linear; IOP increased 0.3 mm Hg for every 10 µm increase in CCT (p<1x10–6). For patients undergoing myopic procedures, every 10 µm of ablated tissue resulted in an IOP decrease of 0.3 mm Hg. When controlling for refractive error, patients undergoing LASIK had an IOP decrease of 0.9 mm Hg greater than patients undergoing PRK (p<1x10–6), indicating that the cutting of the lamellar flap in LASIK lowers IOP by an average of 0.9 mm Hg. From this, we can conclude that preoperative IOP has a strong, linear relationship with CCT, and patients undergoing myopic refractive surgery have a decrease in IOP by 0.3 mm Hg for every 10 µm of ablated tissue. The cutting of the lamellar flap lowers IOP by 0.9 mm Hg, independent of preoperative refractive error. Association of aqueous humor dynamic markers in glaucoma with canaloplasty surgery Sayoko E. Moroi, MD, PhD, Samir Shah, BS, Jesse Gilbert, BS, David Reed, PhD Canaloplasty is a newer surgical alternative to trabeculectomy for lowering intraocular pressure (IOP). In a retrospective, single surgeon consecutive case series of 32 canaloplasty procedures in complex forms of open-angle glaucoma, we sought to determine whether or not the presence of hyphema on postoperative day one was associated with outcome. The average age was 60.4 ± 18.9 years (range of 15–88 years). There were a total of 60 prior laser and/or incisional surgeries. The average preoperative IOP was 21.8 mm Hg and average postoperative IOP at six months was 13.4 mm Hg. The average vertical cup-to-disc ratio was 0.87 + 0.12 with two eyes having "moderate" glaucoma and 29 eyes having "severe" glaucoma. In this small case series, we concluded the following: 1) canaloplasty is possible in complex open-angle forms of glaucoma after prior glaucoma surgeries; and 2) the presence of hyphema on postoperative day one was not associated with improved postoperative IOP-lowering outcomes. Future studies to analyze the fluorescein canalograms of these patients at the time of canaloplasty are in progress to determine the role of downstream episcleral and intrascleral venous pathways for angle surgery outcomes. EW New continued from page 17 the heads of visitors. This glass animates the lobby through its interaction with natural and artificial light with different colors, angles, and intensity throughout the day. The sculpture is titled "Shine the Light," which is the theme of the whole institute, and was developed by artist Ed Carpenter, from Portland, Ore. Dichroic glass was chosen for its special optical properties, which produce light reflections that are complementary in color to the light projections. Colors shift as the angle of the light changes. So the glass may appear one color from one angle and another from a different angle. This is intended to reinforce the institute's mission to enhance eyesight and performance. Another unique application of art is the choice of what to feature on the institute's interior clinic walls. Several scientific posters presented at prior Association for Research in Vision and Ophthalmology conferences by the faculty, with unique ophthalmic visuals, are displayed throughout the Eye Institute, giving patients an insight into the science involved with the institute as well as a unique perspective on their treatments. More information on the institute and the UC Irvine Health's Department of Ophthalmology can be found at www.eye.uci.edu. EW