David S. Greenfield, MD
Associate Professor of Ophthalmology
Applying Imaging Technologies for Glaucoma Diagnostics

View published articles in the National Library of Medicine.

Research Summary

My primary area of original research is based on the hypothesis that glaucoma is a progressive optic neuropathy, and therefore early diagnosis and effective monitoring of response to therapy requires quantitative assessment of the integrity of nerve fiber layer. This approach challenges the time-honored concept that glaucoma simply represents a syndrome defined by the presence of elevated intraocular pressure (IOP), visual field loss and typical glaucomatous optic nerve cupping. Advances in ocular imaging technology provide a means for measuring loss of nerve fiber layer prior to the onset of detectable visual field loss with standard automated perimetry.

NEI-Funded Imaging Research. The specific aims of my NEI-funded project are 1) to identify sources of ocular imaging artifact and devise appropriate methods for correction, 2) to establish long term limits of reproducibility of structural measurements for glaucoma as a foundation for identifying glaucomatous progression, and 3) to investigate novel structural endpoints for glaucoma diagnosis and detection of progression.

I am using three different but complementary imaging technologies for my studies, scanning laser polarimetry, optical coherence tomography, and scanning laser ophthalmoscopy. In previous reports, I have established that such technologies provides objective, reproducible measurements that correlate with known parameters of optic nerve structure and visual function. Recent collaborative work with Dr. Robert Knighton has resulted in development of an instrument capable of improving the diagnostic precision of scanning laser polarimetry. This research, funded by a National Institutes of Health RO1 grant, has spurned international interest and serves as a model for collaborative investigative efforts at the University of California , San Diego with Dr. Robert Weinreb. Finally, as the primary pathologic event in glaucoma represents the death of ganglion cells and their axons, technology enabling one to measure the thickness of the retinal nerve fiber layer represents a means for more accurate monitoring of disease progression than perimetry. Future studies will be directed toward substantiating this hypothesis, and will attempt to improve the sensitivity and specificity of these technologies.

Pharmaceutial Trials. I am also active in pharmaceutical research, studying the safety and efficacy of various antiglaucomatous medications. I am currently the principal investigator for a 48-month, multicentered, randomized, double-masked, placebo-controlled clinical study designed to evaluate the effectiveness and safety of oral memantine (192944-OAG) in patients with chronic open-angle glaucoma, funded by Allergan, Inc. I am also the principal investigator for a multicenter, double-masked, 2-arm parallel group study comparing the effect of brimonidine 0.2% versus timolol 0.5% on visual field stability in patients with normal-tension glaucoma. Among other topics, I have a clinical research interest in complications of glaucoma filtering bleb infections and have published eight original reports detailing the clinical characteristics, management, and prognosis of this disorder. I was the first to characterize a staging system for bleb-related infection designed to help guide therapy. I lecture nationally and internationally on this topic and I have recently been asked to prepare a clinical module for the American Academy of Ophthalmology's Focal Points.