Some of the most useful tools for diagnosis and understanding of blinding retinal diseases rely on the use of spectral reflectance. Improvements to these tools, especially over the past decade, have greatly advanced our ability to achieve extremely high-resolution images of the human retina. In particular, scanning laser ophthalmoscopy has proven to be an important technique for studies of microperimetry, psychophysics and visual neuroscience by imaging the cone mosaic while simultaneously delivering stimuli to single cones. Due to the unprecedented resolution now achieved during retinal imaging, there is an increasing need for using longer wavelength light that can penetrate deeper into tissue and is invisible or imperceptible to the human eyes. Bounded by human eye response and increased optical absorption, the use of wavelengths between 900 and 1100 nm is the most suitable solution. Unfortunately, while there are several vendors providing decent light sources across this wavelength range there are no suitable photodetectors. Therefore, the goal of this proposed research effort is to develop an avalanche photodiode (APD) module with exceptional response from the visible to 1050 nm that will be compatible with established scanning laser ophthalmoscopes. Our proposed solution uses our APD's high responsivity to near-infrared radiation to develop a receiver module useful for ophthalmoscopy and other health sciences. In Phase I, we successfully demonstrated the feasibility of the approach by assembling a custom near-infrared enhanced receiver APD module including wide amplification electronics providing a high gain bandwidth of >40 Mhz. This receiver was then used in an adaptive optics SLO (AOSLO) at the University of Alabama, Birmingham. Through its use, images of a living retina were recorded with a tunable laser source from 600 to 1070 nm. This was the first time such images were realized with a signal receiver. During Phase II, we will address the reliability, manufacturing, packaging and commercial concerns of the receiver module. In addition, our research collaborators will continue to use the receiver as it evolves to enable a range of important clinical studies on the living human retina. These studies will include important 3D imaging on of photoreceptor cells, multi-channel sampling, and the acquisition of retinal images with illumination wavelengths longer than presently applied. This information will be used in their studies to better understand the pathogenesis of Pathological Myopia.
Radiation Monitoring Devices, Inc. proposes to develop a receiver module with response to near-infrared radiation that is significantly higher than any currently available product. This module will promote new retinal imaging technologies and let specialist utilize established diagnostic imaging instruments in a much more effective manner. As part of the proposed effort, the module will be utilized to help predict the onset of pathological myopia, a common retinal disease affecting millions of people worldwide.