Retinal Structure & Function Laboratory
Research Team
- Dr Michael Pianta
- Ms Richa Verma
- Ms Carla Abbott
- Ms Laura Downie
- Ms Monica Jong
National & International Collaborators
- Professor Samuel Jacobson, Associate Professor Artur Cideciyan - Scheie Eye Institute, USA
- Professor Barbara Gillam - Psychology, University of New South Wales, Australia
- Dr Colin Clifford - Psychology, University of Sydney, Australia
- Dr Erica Fletcher - Anatomy and Cell Biology, University of Melbourne, Australia
Retinal Structure & Function
The increasing hope of treatment for hereditary retinal degenerations highlights the need to develop objective methods for evaluating therapeutic potential and efficiency. Optical coherence tomography (OCT), a non-invasive imaging technique that provides high-resolution cross-sectional images of the retina in vivo, holds promise in this regard. Likewise, functional measures based on psychophysics and electrophysiology can be used to pinpoint deficits and guide the development of treatment strategies.
Non-invasive Assessment of Retinal Structure & Function
Some information about the relationship between OCT scans and retinal histology has been gained from patients with retinal diseases of known pathology and demonstrations of qualitative resemblance of scans to retinal histologic features. However, quantitative comparisons between OCT scans and histology are rare. Our laboratory is using animal models of retinal disease to develop OCT as a non-invasive technique for making quantitative measurements of retinal structure. We are also developing advanced image processing techniques to remove noise and improve the quality of OCT scans. Psychophysical (light and dark adaptation) and electrophysiological (ERG) techniques allow us to probe retinal function and to relate retinal function to retinal structure. Using these techniques we are able to investigate how photoreceptors and post-receptoral retinal elements respond to light stimulation. Thus, we can determine the relationship between measures of retinal structure and function. This will not only aid in the early detection of retinal disease, but also enable assessment of therapeutic potential, and evaluation of the effectiveness of treatment strategies.
Visual & Perceptual Adaptation
Human Cone Type-specific Adaptation
For the effective operation of the photopic visual system, sensitivity must be maintained over a six-log-unit range of light levels. To do this, the system must adjust its response based on the ambient light level - the system must adapt. We use paired-flash ERGs to isolate cone responses to coloured flashes after various levels of adaptation to coloured fields. Analysis of the results in cone-contrast space will allow us to identify the range of light levels over which cone type-specific adaptation occurs, and to isolate the site of cone type-specific adaptation.
Mechanisms of 3-D Adaptation & After-Effects
When patients have a change in their glasses they often experience distortions in the apparent 3-D layout of the environment; the distortions become less apparent over a period of several weeks. This is one example of the ability of the human visual system to adapt to 3-D distortions. We are investigating the many types of adaptation and after effects that occur with 3-D stimuli. By independently manipulating depth cues in stereoscopic stimuli we are able to determine the contributions of individual cues to the different types of 3-D adaptation.
Selected Recent Publications
- Pianta, M.J. & Kalloniatis, M. (2000). Characterization of dark adaptation in human cone pathways: an application of the equivalent background hypothesis. Journal of Physiology, 528, 591-608.
- Pianta, M.J., Aleman, T.S., Cideciyan, A.V., Sunness, J.S., Li, Y., Campochiaro, B.A., Campochiaro, P.A., Zack, D.J., Stone, E.M. & Jacobson, S.G. (2003). In vivo micropathology of Best macular dystrophy with optical coherence tomography, Experimental Eye Research, 76 (2), 203-211.
- Pianta, M.J. & Gillam, B.J. (2003). Paired and unpaired features can be equally effective in human depth perception. Vision Research, 43 (1), 1-6.
- Gillam, B.J., & Pianta, M.J. (2005). The effect of surface placement and surface overlap on stereo slant contrast and enhancement. Vision Res, 45 (25-26), 3083-3095.