Advances in Understanding the Structure and Function of the Retina

Time/Room: Friday, May 8, 2009, 1:00 – 3:00 pm, Royal Ballroom 4-5
Organizer: Donald Hood, Columbia University
Presenters: Dennis Dacey, Paul R Martin, Austin Roorda, Donald C Hood

This symposium was designed in conjunction with Steve Shevell to bring the latest advances presented at ARVO to the VSS audience. There will be four talks covering the following topics. I will moderate it and speak last on. “Advances in structural imaging of the human retina.” Before me the speakers and topics will be: D. Darcy (Advances in retinal anatomy); P. Martin (Advances in retinal physiology); and A. Roorda (Advances in optical imaging of the human retina). The speakers are all experienced researchers and lectures use to speaking to diverse audiences. Thus  the level should be appropriate for all attendees at VSS from students to experts in vision or cognition.

Advances and challenges in understanding the normal retina

Speaker: Dennis Dacey, University of Washington

The vertebrate retina is one of the most accessible parts of the central nervous system for clarifying the links between neural circuits and visual coding. Advanced imaging methods are already revealing fundamental features of retinal organization and function previously inaccessible to study. As a background for considering future directions I will review our current understanding of the cellular architecture of the primate retina. On the one hand, the retina is an elegantly simple structure at the periphery of the visual system where mosaics of receptor cells transmit signals to interneurons and ganglion cells whose axons project a representation of the visual world to the brain. However, the retina is also an amazingly complex neural machine that contains at least 80 anatomically and physiologically distinct cell populations. The interactions among most of these cell types are precisely arranged in a microlaminated sheet that provides the scaffold for ~ 20 separate visual pathways. In the primate, much attention has been focused in the so-called ‘midget pathway’, yet these cells, despite their numerosity, only account for two anatomically distinct visual pathways. By contrast, the great majority of visual pathways exists at relatively low density and subserves diverse functions ranging from color vision and motion detection to the pupil reflex and setting biological rhythms. Microdissecting the structure and function of each of these diverse low-density pathways remains a key challenge for retinal neurobiology.

Advances in understanding circuits serving colour vision.

Speaker: Paul R Martin, National Vision Research Institute of Australia & Department of Optometry and Vision Sciences & University of Melbourne, Australia

The theory of trichromatic human colour vision was proposed over 200 years ago and the existence of three types of cone photoreceptors was confirmed in the 1980s. I will summarise current views of how the signals from cone photoreceptors are organised into “blue-yellow” and “red-green” pathways in the subcortical visual system. These pathways can be distinguished at the first synapse in the visual pathway, between cone photoreceptors and cone-contacting bipolar cells, and remain segregated in the subcortical afferent visual pathway.  I will review evidence from molecular biology, anatomy, and physiology showing that the blue-yellow pathway likely forms a primordial colour vision system common to most diurnal mammals, whereas the red-green pathway is unique to primates and evolved together with high-acuity spatial vision.

Advances in optical imaging of the human retina.

Speaker: Austin Roorda PhD, University of California, Berkeley

Adaptive optics (AO) is a technique to correct for the aberrations in the eye’s optics, and offers non-invasive, optical access to the retina in living eyes on an unprecedented scale. The technology is very useful for ophthalmic imaging and is being used for basic and clinical imaging, but the scope of applications goes well beyond. By coupling scanning laser technology with adaptive optics, we are able to track and deliver light to the retina with the precision and accuracy of single cones and can simultaneously record either perceptual (human) or electrical responses (monkey). These measurements are helping to reveal basic properties of the human visual system.

Advances in structural imaging of the human retina.

Speaker: Donald C Hood, Columbia University

With recent advances in the structural imaging, it is now possible to visualize individual retinal layers of the human retina in vivo. After a short summary of the technique of optical coherence tomography (OCT), its application to understanding the structure and function of the normal and diseased eye will be considered. First, measurements of the thickness of the normal human receptor, inner nuclear, and ganglion cell layers will be presented and the possibilities of using this technique to study normal human vision discussed. Next, data from patients with diseases that affect the receptors (e.g. retinitis pigmentosa) and retinal ganglion cells (e.g. glaucoma) will be presented and discussed in terms of tests of hypotheses about the relationship between behavior (i.e. visual loss) and structural (i.e. anatomical) changes in these layers.