About

Ravi Jonnal is an Associate Professor in Residence at the UC Davis School of Medicine, specializing in vision science and cognitive science. His research focuses on studying retinal neurons and developing methods to observe the anatomy and physiology of these cells in the living human eye. The tools developed in his lab have the potential to dramatically improve diagnosis of retinal disease and accelerate the development of therapeutic interventions. His work involves advanced optical imaging techniques such as adaptive optics, optical coherence tomography, and computational imaging to investigate retinal anatomy and physiology, including photoreceptor function and responses to light stimuli.

Research topics

• Computer Science
• Artificial Intelligence
• Physics
• Optics
• Medicine
• Ophthalmology
• Computer vision
• Telecommunications
• Biology
• Biomedical engineering
• Neuroscience

Selected publications

• High-speed adaptive optics swept-source full-field OCT

  2026-01-16

  article
  PublisherDOI

• Optoretinographic response of human cone photoreceptors during dark adaptation

  2026-03-05

  articleSenior author
  PublisherDOI

• Full-field swept source optical coherence tomography for structural and functional retinal imaging in mice

  2026-03-05

  article

  We report a full-field swept-source optical coherence tomography (FF-SS-OCT) system with a ~ 20 million A-scan/s rate for the in vivo structural and functional imaging of the mouse retina. The FF-SS-OCT, configured as an on-axis Mach-Zehnder interferometer, employs a tunable wavelength source and a high-speed 2D CMOS camera. Optimized coherent illumination and detection strategies are implemented for an efficient full-field imaging of the mouse retina. The light-evoked experiments (Optoretinography-ORG) are performed using a single-flash stimulus to bleach controlled fractions of rhodopsin in individual experiments. Serial OCT volume acquisition facilitates the quantitative assessment of relative shifts in outer retinal layer positions and changes in the backscattering intensity post-stimuli.

  PublisherDOI

• Combined Mouse Retinal Optoretinography/Electroretinography System to Study Light-Evoked Responses in Animal Models of Retinal Degeneration

  Investigative Ophthalmology & Visual Science · 2026-01-20 · 1 citations

  articleOpen access

  Purpose: To study the correlation between optoretinogram (ORG) and the underlying phototransduction-initiated physiology, we irradiated mouse retinas with visible light centered at a 482-nm wavelength to induce bleach-initiated morphologic changes in the outer retinal layers, including photoreceptors and the retinal pigment epithelium (RPE). Methods: A 482-nm light-emitting diode was used for short-pulse irradiation of the retina over a large field of view in the three groups of mice, including disease models, while acquiring optical coherence tomography (OCT) image sequences using a custom-built OCT system combined with a commercial electroretinogram (ERG) system. The visible light exposure was adjusted to vary the total light energy (number of photons) delivered to the retina, enabling observation of the bleach-level dependence of the ORG and ERG signals. Results: Light-driven thickness increments in the outer retinal layers, including the photoreceptors and RPE, were observed in wild-type (WT) albino and pigmented mice. However, the energy of light stimuli did not produce a response in the retina of the rd10 mouse model. The lack of a full-field ERG response in the same animals also confirmed this observation. These suggested that phototransduction in the 3-month-old rd10 mice could not be initiated. Conclusions: The ORG and ERG measurements recorded under various light stimuli reveal the retina's neural function. The ORG and ERG signals from the WT albino and pigmented mice exhibited thickness increments in the ORG and an increase in amplitude of a-waves and b-waves in the ERG, which were linked to phototransduction; however, these signal trends were not observed in the rd10 mice. Therefore, the ORG/ERG system could be an attractive instrument that provides both localized structural and global functional information about the investigated retina, allowing for detailed studies of neural function suppression in animal models of retinal degeneration.

  PublisherDOI

• Photopigment bleaching calculation and simulation notebook

  Open MIND · 2026-03-12 · 1 citations

  otherOpen accessSenior author

  This notebook provides a quantitative framework for simulating retinal cone photopigment bleaching using photometric and radiometric formulations. This release includes minor updates to the photopigment bleaching worksheet notebook. Changes: Updated bleaching calculations Improved table headers Fixed typos and an error in the code for final table generation Updated README and citation information Authors Reddikumar Maddipatla$^{1,2}$, Yao Cai$^{1}$, Robert J. Zawadzki$^{1,2}$, and Ravi S. Jonnal$^{1}$ $^{1}$ Center for Human Ophthalmic Imaging Research (CHOIR), UC Davis Eye Center, Sacramento, CA 95817, USA $^{2}$ EyePOD Imaging Lab, Department of Cell Biology and Human Anatomy, University of California, Davis, CA 95616, USA

  PublisherDOI

• Investigating phase noise in velocity-based optoretinography

  2026-01-16

  article
  PublisherDOI

• Adaptive optics OCT used to measure outer segment length dynamic equilibria in response to constant backgrounds

  2026-03-05

  articleSenior author
  PublisherDOI

• Dark adaptation of cone photoreceptor responses is revealed by optoretinography

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-05-01

  articleOpen accessSenior author

  Dark adaptation is the essential process that restores visual sensitivity following exposure to bright light, yet the underlying mechanisms remain incompletely understood. Here, we propose a method for assessing dark adaptation in cones using optoretinography (ORG) based on adaptive optics optical coherence tomography (AO-OCT). ORG quantifies cone functional response by monitoring nano-scale changes in the cone's outer segment occurring over hundreds of milliseconds after visible stimulation. This method consists of sequential measurements of stimulus-evoked cone responses over the course of minutes of dark adaptation. Each response captures optical path length changes in single photoreceptor outer segments over milliseconds during a multi-minute recovery period following a strong photopigment bleach. We parameterized cone ORG responses and proposed an exponential model linking ORG dynamics to pigment regeneration. Parameters of the ORG response exhibited exponential decay behavior during dark adaptation, and were thus fit with exponential functions and quantified by the resulting decay parameter τ. Parameters capturing the amplitude of the ORG responses recovered more slowly than those capturing temporal dynamics of the responses. This difference is consistent with distinct contributions from photopigment regeneration and downstream phototransduction processes. Recovery speed varied by two- to threefold among three normal subjects, suggesting substantial inter-subject physiological diversity. Processes within the cone, including pigment regeneration, are thought to underlie the gains in photopic visual sensitivity that occur in the dark. These findings highlight ORG as an objective and sensitive assay of those cellular mechanisms. While the ORG itself has shown promise as a biomarker of the health of the photoreceptor response to light, the results of this study show that it may also be useful for probing the health of the intra- and intercellular homeostatic mechanisms that support it.

  PublisherOA PDFDOI

• Photopigment bleaching calculation and simulation notebook

  Zenodo (CERN European Organization for Nuclear Research) · 2026-03-11

  otherOpen accessSenior author

  Initial release of the Photopigment Bleaching Worksheet notebook. Provides a quantitative framework for simulating retinal photopigment bleaching using photometric and radiometric formulations.

  PublisherDOI

• Dark adaptation of cone responses and inter-subject variability measured using adaptive optics OCT optoretinography

  2026-03-05

  articleSenior author
  PublisherDOI

Recent grants

• Investigating fundamental properties and clinical applications of the optoretinogram

  NIH · $2.0M · 2022–2027

• Properties of Photoreceptors and Muller Cells Investigated with AO-OCT

  NIH · $739k · 2016–2021

• Properties of photoreceptors and Muller cells investigated with AO-OCT

  NIH · $196k · 2016–2017

Frequent coauthors

• Robert J. Zawadzki

  University of California, Davis

  78 shared

• Donald T. Miller

  Indiana University Bloomington

  67 shared

• John S. Werner

  University of Lusaka

  51 shared

• Denise Valente

  Universidade de Pernambuco

  39 shared

• Kari V. Vienola

  36 shared

• Omer P. Kocaoglu

  Izmir Kâtip Çelebi University

  33 shared

• Barry Cense

  Yonsei University

  32 shared

• Weihua Gao

  29 shared

Education

• Ph.D., Ophthalmology

  University of California, Davis

  2005

• M.D.

  University of California, Davis

  2001

• B.S., Biology

  University of California, Davis

  1997