Bio


My current interests are in development of design and instrumentation of pre-clinical vision devices, to conduct non-invasive in vivo retinal imaging. I studied Physics with a concentration in optics during my time at University of Hyderabad, India and received a bachelors and masters degree in 2014. I then moved to USA to continue working in the field of optics at University of North Carolina at Charlotte to pursue my PhD, working on nanofabrication of broadband anti-reflective structures. My interest in vision science started with my job at University of Rochester as a research scientist, where I was involved in developing optical imaging tools using adaptive optics to study retinal diseases. My work was focused on development of fluorescence lifetime imaging techniques in humans and two photon fluorescence microscopy in mouse.

Supervisors


Education & Certifications


  • Ph.D., University of North Carolina at Charlotte, Optical Science and Engineering (2018)
  • MS, University of North Carolina at Charlotte, Optical Science and Engineering (2018)
  • MSc, University of Hyderabad, INDIA, Physics (2014)

Work Experience


  • Research Engineer, Stanford University (October 2022 - Present)

    Location

    2370 Watson Ct, Palo Alto, CA 94303, USA

  • Research Scientist, University of Rochester (January 2019 - September 2022)

    Location

    Rochester, NY, USA

All Publications


  • Near Infrared Autofluorescence Lifetime Imaging of Human Retinal Pigment Epithelium Using Adaptive Optics Scanning Light Ophthalmoscopy. Investigative ophthalmology & visual science Kunala, K., Tang, J. A., Bowles Johnson, K. E., Huynh, K. T., Parkins, K., Kim, H. J., Yang, Q., Sparrow, J. R., Hunter, J. J. 2024; 65 (5): 27

    Abstract

    To demonstrate the first near-infrared adaptive optics fluorescence lifetime imaging ophthalmoscopy (NIR-AOFLIO) measurements in vivo of the human retinal pigment epithelial (RPE) cellular mosaic and to visualize lifetime changes at different retinal eccentricities.NIR reflectance and autofluorescence were captured using a custom adaptive optics scanning light ophthalmoscope in 10 healthy subjects (23-64 years old) at seven eccentricities and in two eyes with retinal abnormalities. Repeatability was assessed across two visits up to 8 weeks apart. Endogenous retinal fluorophores and hydrophobic whole retinal extracts of Abca4-/- pigmented and albino mice were imaged to probe the fluorescence origin of NIR-AOFLIO.The RPE mosaic was resolved at all locations in five of seven younger subjects (<35 years old). The mean lifetime across near-peripheral regions (8° and 12°) was longer compared to near-foveal regions (0° and 2°). Repeatability across two visits showed moderate to excellent correlation (intraclass correlation: 0.88 [τm], 0.75 [τ1], 0.65 [τ2], 0.98 [a1]). The mean lifetime across drusen-containing eyes was longer than in age-matched healthy eyes. Fluorescence was observed in only the extracts from pigmented Abca4-/- mouse.NIR-AOFLIO was repeatable and allowed visualization of the RPE cellular mosaic. An observed signal in only the pigmented mouse extract infers the fluorescence signal originates predominantly from melanin. Variations observed across the retina with intermediate age-related macular degeneration suggest NIR-AOFLIO may act as a functional measure of a biomarker for in vivo monitoring of early alterations in retinal health.

    View details for DOI 10.1167/iovs.65.5.27

    View details for PubMedID 38758638

  • Near-infrared adaptive optics fluorescence lifetime ophthalmoscopy of human retinal pigment epithelium reveals variations with eccentricity and disease Kunala, K., Tang, J., Johnson, K., Huynh, K. T., Parkins, K., Yang, Q., Hunter, J. J. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2023
  • Prolonged Fluorescence Lifetimes of the Retinal Pigment Epithelium in Human Subjects with Pentosan Polysulfate Sodium Toxicity Johnson, K., Tang, J., Kunala, K., Parkins, K., Yang, Q., Hunter, J. J. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2023
  • Erratum: Adaptive optics fluorescence lifetime imaging ophthalmoscopy of in vivo human retinal pigment epithelium: erratum. Biomedical optics express Tang, J. A., Granger, C. E., Kunala, K., Parkins, K., Huynh, K. T., Bowles-Johnson, K., Yang, Q., Hunter, J. J. 2023; 14 (4): 1544

    Abstract

    [This corrects the article on p. 1737 in vol. 13, PMID: 35414970.].

    View details for DOI 10.1364/BOE.485995

    View details for PubMedID 37078038

  • Mapping the origin of two-photon excited fluorescence in macaque retinal layers with adaptive optics fluorescence lifetime ophthalmoscopy Huynh, K. T., Chadderdon, A. B., Kunala, K., Parkins, K., Yang, Q., Hunter, J. J. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2022
  • Calcium responses to optogenetic stimulation decay faster in primate retinal ganglion cells after photoreceptor ablation Xu, Z., Kunala, K., Murphy, P., Koo, E., Puthussery, T., McGregor, J. E. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2022
  • In vivo measurement of light steering by single retinal cells optimizes phase-contrast AOSLO Feng, G., Yang, Q., Kunala, K., Schallek, J. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2022
  • Optogenetic therapy restores retinal activity in primate for at least a year following photoreceptor ablation MOLECULAR THERAPY McGregor, J. E., Kunala, K., Xu, Z., Murphy, P. J., Godat, T., Strazzeri, J. M., Bateman, B. A., Fischer, W. S., Parkins, K., Chu, C. J., Puthussery, T., Williams, D. R., Merigan, W. H. 2022; 30 (3): 1315-1328

    Abstract

    All retina-based vision restoration approaches rely on the assumption that photoreceptor loss does not preclude reactivation of the remaining retinal architecture. Whether extended periods of vision loss limit the efficacy of restorative therapies at the retinal level is unknown. We examined long-term changes in optogenetic responsivity of foveal retinal ganglion cells (RGCs) in non-human primates following localized photoreceptor ablation by high-intensity laser exposure. By performing fluorescence adaptive optics scanning light ophthalmoscopy (AOSLO) of RGCs expressing both the calcium indicator GCaMP6s and the optogenetic actuator ChrimsonR, it was possible to track optogenetic-mediated calcium responses in deafferented RGCs over time. Fluorescence fundus photography revealed a 40% reduction in ChrimsonR fluorescence from RGCs lacking photoreceptor input over the 3 weeks following photoreceptor ablation. Despite this, in vivo imaging revealed good cellular preservation of RGCs 3 months after the loss of photoreceptor input, and histology confirmed good structural preservation at 2 years. Optogenetic responses of RGCs in primate persisted for at least 1 year after the loss of photoreceptor input, with a sensitivity index similar to optogenetic responses recorded in intact retina. These results are promising for all potential therapeutic approaches to vision restoration that rely on preservation and reactivation of RGCs.

    View details for DOI 10.1016/j.ymthe.2021.09.014

    View details for Web of Science ID 000765833300013

    View details for PubMedID 34547460

    View details for PubMedCentralID PMC8899524

  • Adaptive optics fluorescence lifetime imaging ophthalmoscopy of in vivo human retinal pigment epithelium BIOMEDICAL OPTICS EXPRESS Tang, J. H., Granger, C. E., Kunala, K., Parkins, K., Huynh, K. T., Bowles-Johnson, K., Yang, Q., Hunter, J. J. 2022; 13 (3): 1737-1754

    Abstract

    The intrinsic fluorescence properties of lipofuscin - naturally occurring granules that accumulate in the retinal pigment epithelium - are a potential biomarker for the health of the eye. A new modality is described here which combines adaptive optics technology with fluorescence lifetime detection, allowing for the investigation of functional and compositional differences within the eye and between subjects. This new adaptive optics fluorescence lifetime imaging ophthalmoscope was demonstrated in 6 subjects. Repeated measurements between visits had a minimum intraclass correlation coefficient of 0.59 Although the light levels were well below maximum permissible exposures, the safety of the imaging paradigm was tested using clinical measures; no concerns were raised. This new technology allows for in vivo adaptive optics fluorescence lifetime imaging of the human RPE mosaic.

    View details for DOI 10.1364/BOE.451628

    View details for Web of Science ID 000764563900001

    View details for PubMedID 35414970

    View details for PubMedCentralID PMC8973160

  • Adaptive optics fluorescence lifetime ophthalmoscopy of iGlucoSnFR-TS suggests increased glucose in RPE of rho(-/-) compared to healthy mice Kunala, K., Xue, Y., Huynh, K., Yang, Q., Parkins, K., Steven, S., Dubra, A., Cepko, C., Hunter, J. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2021
  • Adaptive optics fluorescence lifetime imaging ophthalmoscopy of the human RPE mosaic Tang, J., Granger, C. E., Parkins, K., Kunala, K., Huynh, K., Bowles-Johnson, K., Yang, Q., Hunter, J. J. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2021
  • Optogenetic activation of retinal ganglion cells persists for at least a year in primate fovea following photoreceptor loss McGregor, J. E., Kunala, K., Xu, Z., Parkins, K., Godat, T., Strazzeri, J. M., Bateman, B. A., Williams, D. R., Merigan, W. H. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2020
  • Optical scattering measurements of random anti-reflection subwavelength surface structures on binary gratings Gadamsetti, P., Kunala, K., Poutous, M. K., Jiang, S., Digonnet, M. J. SPIE-INT SOC OPTICAL ENGINEERING. 2020

    View details for DOI 10.1117/12.2544368

    View details for Web of Science ID 000568488700026

  • Optical Scattering of Deterministic Diffractive Elements with Antireflective Structured Surfaces Gadamsetti, P., Kunala, K., Poutous, M. K., IEEE IEEE. 2019: 223-225
  • Random antireflective nanostructuring on binary near-wavelength period gratings OPTICAL ENGINEERING Kunala, K., Poutous, M. K. 2018; 57 (8)
  • Diffraction efficiency performance of random anti-reflecting subwavelength surface structures on prefabricated fused silica binary gratings APPLIED OPTICS Kunala, K., Poutous, M. K. 2018; 57 (16): 4421-4427

    Abstract

    Random anti-reflecting subwavelength surface structures have been reported to enhance transmission of optical windows and lenses. Specifically, for fused silica substrates, 99.9% specular transmission has been verified by various groups. Diffractive optical elements, such as gratings, also experience net Fresnel losses on both their planar and structured surfaces. We investigated the performance of prefabricated 50% duty-cycle, binary, fused silica linear gratings, with a period of 1.6 μm, before and after application of random anti-reflecting subwavelength surface structures, in order to reduce their initial Fresnel reflectivity. We compared the diffraction order directions and their efficiencies at three test wavelengths: 594, 612, and 633 nm, for both TE(s) and TM(p) incident light polarization states, under three different mountings: normal, first Bragg, and second Bragg incidence. We report transmission enhancement of the sum of all propagating grating orders for all cases tested by factors between 2% and 10%, with reduction of the respective reflected orders by similar ratios. Transmission enhancement of the -2 diffraction order at Bragg incidence suggests that the random etch has different rates between the raised and lowered linear grating topography.

    View details for DOI 10.1364/AO.57.004421

    View details for Web of Science ID 000433959100011

    View details for PubMedID 29877388

  • Optical characterization of random anti-reflecting subwavelength surface structures on binary gratings Kunala, K., Sapkota, G., Poutous, M. K., Jiang, S., Digonnet, M. J. SPIE-INT SOC OPTICAL ENGINEERING. 2018

    View details for DOI 10.1117/12.2284523

    View details for Web of Science ID 000449778300015