Probing retinal and neural mechanisms of vision by hyperacute optical stimulation of single photoreceptor cells

• Applicant: Dr. Wolf Harmening
• Subject Area: Cognitive, Systems and Behavioural Neurobiology
• Term: from 2010 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 190271452

Visual function is most frequently assessed by measuring the observer’s visual acuity, i.e. the smallest optotypes – usually letters – that are just identifiable. This process is limited by the optical quality of the eye and the neural structures that sample the retinal image. However, another class of visual resolution – hyperacuity – exists that surpass conventional acuity, thereby demonstrating that visual capabilities are strongly influenced by retinal circuitry and the neuronal machinery of the brain. The measurement of hyperacute perception offers a few advantageous over classical tests of visual resolution, since it primarily addresses the neural fraction of the observer’s visual capabilities. Although vernier acuity is well-studied within the neurosciences, the exact retinal and neural mechanisms underlying hyperacute perception are unknown. Recent advances in optical stimulation and retinal imaging makes it now possible to deliver visual stimuli at cone-targeted retinal locations in the living human eye. I here propose to study the mechanisms of hyperacute perception at the level of single retinal photoreceptors to uncover the discrete retinal wiring underlying spatial vision tasks. To distinguish pure retinal from central aspects of hyperacute sensitivity, all experiments will also be carried out with amblyopic subjects, i.e. subjects who suffer from decreased neural visual acuity. Finally, procedures will be engineered that promote the use of a hyperacute measurement in standard ophthalmic examination. Hyperacuity tests may offer the possibility to differentially diagnose early neural vision loss, a feat that is not possible with conventional acuity testing.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Austin Roorda, Ph.D.