Strengthening the link between subjective and objective visual acuity

• Applicants: Professor Dr. Sven Heinrich; Professor Dr. Michael Hoffmann
• Subject Area: Ophthalmology
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 435838478

Visual acuity testing is a fundamental ophthalmological examination with eminent relevance for diagnostics, medico-legal decisions, and research progress in clinical and basic science. Importantly, the standard procedure to determine visual acuity is ‘subjective’ testing, where the validity of the results critically depends on the reliability of the patient’s responses. In certain groups of patients this is, due to inability or lack of willingness, a serious confound with far reaching consequences. While ‘objective’ visual acuity testing based on visual evoked potentials (VEPs) has proven to be of value, it is suffering from severe limitations that compromise the reliability of the VEP-acuity estimates. Our recent research advances indicate that these challenges can be overcome with an acuity-testing approach that is based on the cognitive event-related-potential component ‘P300’. Based on the momentum of this research, the current proposal aims to improve objective acuity testing in order to stimulate the wide-spread use of electrophysiological visual acuity estimation.We will address the challenges and limitations of conventional objective acuity testing with a bicentric approach combining bi-modal neuro-imaging [P300/VEP and magnetic resonance imaging (MRI & fMRI)] and psychophysics with the goal to devise an innovative objective acuity-testing scheme. Specifically, we plan to test 250 patients with visual impairment down to legal blindness. We will assess discrepancies between subjective and P300- and VEP-based acuity caused by (i) disease-type, (ii) spatial stimulus characteristics, (iii) cortical constraints, and (iv) temporal dynamics. We will use these insights to (v) establish an integrated framework for beyond-state-of-the-art electrophysiological acuity assessment in clinical and research applications. The aspects addressed will include effects of the interplay of central visual loss and fixation behavior, distorted vision, inherent differences in self-paced psychophysics vs non-self-paced objective readouts, and the scope of cognitive event related potentials and fMRI-based visual field acuity maps. This will advance both the application and our basic understanding of objective acuity testing.With the overarching goal to substantially improve the robustness, reliability, and specificity of objective visual acuity estimates, the project has a strong focus on practical relevance, aiming at the translation of findings into clinical routine and the identification of biomarkers for therapy-success readout. Simultaneously, the experiments will shed light on important aspects of the structure-function interaction in the healthy and diseased human visual system.

• DFG Programme: Research Grants