Dr Ashley Wood
Research Topics and Related Projects:
My Doctoral Thesis evaluated structural and functional changes in early Age-related Macular Degeneration (AMD) for the purpose of improving detection and diagnosis at the earliest stage of the disease process. As a consequence my current research interests stem from this work, in particular Retinal Imaging and Electrophysiology.
Electrophysiology is the study of the tiny electrical signals produced by the cells that make up our bodies which are recorded using sensitive electrodes (see figure 1). My research involves the use of an electrophysiology technique specialised for studying the retina, called the Electroretinogram (ERG). The ERG waveform (see figure 1) represents the combined electrical responses of cells within the retina when exposed to light. Changes to the shape of the waveform can tell us how the retina is being affected by disease.
Figure 1: Photograph showing patient with electrodes positioned to record an ERG (Left). An example “Focal Cone ERG” waveform recorded from a healthy patient with a-wave, b-wave and PhNR annotated (Right).
My work in this area currently involves looking at new ways of analysing the “Focal Cone ERG”, which uses a small “focal” target that only produced an ERG from the central retina affected by AMD. Traditional analysis has focused on measuring the amplitude and implicit times of the a and b waves (see figure 1). The aim of this work is to identify and evaluate new measurement parameters, for example the gradient that may be more reliable or provide greater sensitivity to early AMD.
Today retinal imaging encompasses a wide range of technologies that are all used to produce images, not just photographs, of the retina. One of the biggest advances in recent years has been Optical Coherence Tomography which produces high resolution 3D images of the back of the eye (see figure 2). This technology has revolutionised the detection, diagnosis and monitoring of retinal disease, not just AMD.
Figure 2: A photograph of a healthy macula (A) with arrow indicating location of corresponding OCT image (B). An OCT image from a patient with exudative or “wet” AMD (C) and corresponding macula photograph (D).
My research in this area currently involves using a prototype long wavelength OCT, which compared to commercially available systems enables 3D imaging of not just the retina but also the layer of blood vessels directly beneath it called the Choroid (see figure 3). Previously I have used a prototype long wavelength OCT to investigate the thickness of the retina and choroid in early AMD (Wood et al 2011). I’m now using this technology to investigate the 3-D structure of the choroidal vasculature and how it is affected by both normal ageing and in Age-related Macular Degeneration. The aim of this research is to provide insight into the role choroidal plays in AMD pathogenesis and to identify potential biomarkers for monitoring disease progression in the future.
Figure 3: A cross-sectional OCT image with equivalent anatomical structures labelled (Left). An enface image showing the sub-macular choroidal vasculature (Right).
Macular Research Group
Clinical and Investigative Vision Sciences
Dr. Alison Binns, City University, London.