OSC Colloquium: Alfredo Dubra

    Thursday, February 4, 2021 - 3:30pm - 4:00pm
    Virtual Via Zoom

    Open to campus and public.


    Public Video Unavailable


    Speaker: Alfredo Dubra

    Topic: Adaptive optics ophthalmoscopy: a trove of optical design challenges

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    Imaging the living retina at the microscopic scale presents a number of interesting optical design and wavefront correction challenges. High resolution retinal imaging requires considering not only the performance of ophthalmoscopes, but also that of the eye, which is a complex optical system in its own right. Each eye is unique, with optical surfaces and components that change over time periods as short as a few milliseconds and as long as years, its surfaces are tilted, decentered and lack rotational symmetry. Eyes are constantly rotating in unpredictable ways, have moving surfaces, suffer from large chromatic and monochromatic aberrations, and typically have a GRIN lens. Moreover, the retina is a phase object, with mild scattering and waveguiding properties, that test the validity of linear imaging theories used in microscopy.

    In my presentation, I will describe design considerations for Adaptive optics ophthalmoscopes used to reveal the structure and function of individual retinal cells in human subjects. This will include the use of nodal aberration theory for correcting both static and dynamic aberrations throughout a range of image conjugates (not zoom), accounting for spectacle correction and pupil aberrations. I will also present a novel multi-element lens with freeform surfaces for achieving individualized correction of longitudinal chromatic aberration. Finally, I will also discuss the use of the Shack-Hartmann wavefront sensor for ophthalmic imaging, and correction of its focal shift.

    Speaker Bio(s): 

    Alfredo Dubra is an Associate Professor of Ophthalmology at Stanford University, where he leads a research group focused on the development, translation and dissemination of optical imaging technologies for monitoring disease progression, improving early diagnosis, and understanding of diseases that cause irreversible vision loss.

    Dr. Dubra started his training in optics in the Applied Optics Group of the Universidad de la República in Uruguay, while pursuing a BSc and MSc degrees. He then pursued his PhD and first postdoctoral position at the Photonics Group in Imperial College London. This was followed by a second postdoctoral and first faculty positions at the University of Rochester. Before moving to Stanford, he worked at the Medical College of Wisconsin, where he developed an international network of collaborators to deploy custom ophthalmic adaptive optics instruments worldwide.


    Colloquium will start at 3:30pm, following will be a meet and greet.