Research | Our Research Faculty

Dr. Jan P.G. Bergmanson received his optometric training and PhD at the City University, London. In addition, he obtained a Doctor of Optometry degree from Pennsylvania College of Optometry. Currently, Dr. Bergmanson is Professor of Optometry at the University of Houston College of Optometry (UHCO), where he is the founding Director of the Texas Eye Research and Technology Center (TERTC). He has extensively researched and lectured internationally on subjects of corneal morphological response to contact lens wear, tear and ophthalmic solution effects on the ocular surface, histopathology of ocular tissues damaged by ultraviolet radiation, and the effects of the Excimer Laser on the cornea. In addition to private optometric practice, Dr. Bergmanson, certified in Texas as a Therapeutic Optometrist and as an Optometric Glaucoma Specialist, has provided patient care in several hospital and university clinics. Dr. Bergmanson is a Foundation Fellow of the College of Optometry in United Kingdom, where he remains licensed to practice, and a Fellow of the American Academy of Optometry, where he is a Diplomate in the Cornea and Contact Lens Section. He is a member of the Texas Optometric Association (TOA), American Optometric Association (AOA), Association of Contact Lens Educators, and International Association of Contact Lens Educators. He is a council member of the International Society for Contact Lens Research and a lifetime honorary member of the Swedish and Dutch Optometric Associations, to which he also serves as a consultant. Dr. Bergmanson is the recipient of the 1998 British Contact Lens Association Gold Medal Award, the 2002 Texas Optometric Association's Educator of the Year Award, the University of Houston College of Optometry 2003 Cora and J. Davis Armistead Faculty Teaching Award and the 2005 Swedish Optometric Association's Mark of Honor Award.

David A. Berntsen, OD, PhD, FAAO completed his Doctor of Optometry degree in 2002 at the University of Houston College of Optometry in Houston, TX. He then completed a Cornea and Contact Lens Advanced Practice Fellowship at The Ohio State University College of Optometry in Columbus, OH. The fellowship program combined a two-year residency with a Master of Science degree in Vision Science, which Dr. Berntsen completed in 2004. He then completed a PhD in Vision Science at Ohio State in 2009.

Dr. Cheng earned both her PhD and OD degrees from the University of Houston, College of Optometry. After graduation, she became an associate in a private practice at Sugarland, Texas. She joined the MacGregor Medical Association in 1999 and practiced optometry there until she became a faculty member at the UH College of Optometry in 2002.

Dr. Coates received his PhD in Vision Science from the University of California, Berkeley in 2015, where he studied letter recognition, peripheral visual perception, and crowding, using psychophysics and computational modeling. After postdoctoral appointments in Belgium and Switzerland studying the relationships between crowding, attention, and appearance, he joined the faculty of UHCO in 2017.

His research and teaching interests include spatial vision, color vision, reading, and statistical and psychophysical methods. He is passionate about the use of open source tools for experimentation, analysis, and learning.

I received my undergraduate degree from the Birla Institute of Technology and Science, Pilani, India in 1992 majoring in Electronics Engineering. I then moved to the United States for graduate studies and completed a M.S and Ph.D. degree in 1998 in Biomedical Engineering from Case Western Reserve University, Cleveland, Ohio. My work, carried out under the mentorship of Dr. John Leigh, primarily examined the interactions between visual-oculomotor and vestibular systems. I did post-doctoral work at the Yerkes National Primate Research Center, Emory University with Dr. Michael Mustari from 1999 to 2002. During this time I learnt the technique of single cell extracellular recording in the awake-behaving monkey and also became interested in examining visual-oculomotor mechanisms in the strabismic primate. I was appointed to the faculty at Emory University in 2002 and received an independent investigator award from the National Institutes of Health in 2004 to study neural circuits mediating binocular coordination of eye movements in the strabismic monkey. I have since maintained continued NIH funding. I joined the faculty of the College of Optometry, University of Houston in 2009. The goal of research in my laboratory is to continue to uncover the disruption of neural processing in various brain areas in the strabismic monkeys. A better understanding of neural mechanisms that are affected in the different forms of strabismus will help develop rationally based therapy.

Dr. Frishman received her undergraduate degree from Vassar College in Poughkeepsie N.Y. and her MS and PhD in psychology from the University of Pittsburgh. She did postdoctoral training in visual neuroscience at Northwestern University and the University of California San Francisco where she also was a research faculty member. She joined the Optometry faculty in the College of Optometry in 1990, and she has taught in both the professional and graduate programs. Her research has focused on refining noninvasive electrophysiological approaches for evaluating retinal and anterior visual pathway function in normal subjects and subjects with inherited or acquired diseases that affect visual function.

Dr. Frishman is on the editorial board of Translational Vision Science and Technology (TVST) an academic editor for Plos One, and she was Editor-in-Chief of the journal, Visual Neuroscience (2001-2007), and Documenta Ophthalmologica (2006-2013). She has served on federal grant review panels, the NIH/NEI National Advisory Eye Council, and she is a fellow of the Association for Research in Vision and Ophthalmology (FARVO), American Academy of Optometry (FAAO) and a board member of the International Society for the Clinical Electrophysiology of Vision (ISCEV). 

Li-Fang Hung, B.Med.., Ph.D., O.D. Research Scientist E-MAIL: Lhung2@uh.edu PHONE: (713)743-2038 Bio Dr. Hung received his B.Medicine degree from Chung-Shan Medical and Dental College in Taiwan. In addition, Dr. Hung received his PhD and OD degree from the University of Houston, College of Optometry. Before he came to Houston, he had two years OBGYN clinical experience in military service, four years residency training in ophthalmology at National Taiwan University Hospital in Taiwan, and two years post-doctoral training in infectious diseases in the Department of Medicine at Stanford University, CA. He is currently working with Dr. Earl Smith OD, PhD as a research scientist on experiments that investigate visual/environmental influences on the development of refractive errors in monkeys. Research Interests Emmetropization and myopia Clinical Interests All eye diseases and vision problems Publications Please see C. V. 

Dr. Nange Jin received his M.D. in Clinical Medicine from Yanbian University College of Medicine in China. He earned his Ph.D. in Medical Science with a major in physiology & biophysics at the Seoul National University in South Korea. Afterwards, he received post-doctoral training in the Department of Physiology & Cell Biology at the University of Nevada School of Medicine, Reno. His research now includes the effects of rod-cone coupling plasticity on downstream retinal circuits that control both the image-forming and the non-image-forming visual pathways. Dr. Jin conducted some of this research within Christophe Ribelayga’s laboratory at the University of Texas Health Science Center. Dr. Jin will be joining the department of Vision Sciences as a Research Assistant Professor.

Dr. Manny received her OD and PhD from the University of Houston, College of Optometry. She has been teaching in the clinic and classroom since 1981. Prior to earning her PhD she worked part-time in a private practice. Her clinical expertise is pediatric eye care with an emphasis on children under the age of 6 years and those with special needs. As a clinician scientist she has served as the principal investigator for a variety of multi-center clinical studies funded by the National Eye Institute as well as industry. These studies included clinical trials looking at the development, progression and treatment strategies for nearsightedness (myopia) (COMET, COMET2, ACHIEVE, CLIP), large collaborative observational studies of myopia (CLEERE, COSMICC), and collaborations with the Pediatric Eye Disease Investigator network (PEDIG) studying different treatment options for amblyopia and strabismus. Other research interests include improving screening methods used to identify infants and preschool children with vision problems or at risk for vision problems. She is a fellow of the American Academy of Optometry, and serving as a Vice chair of PEDIG (2014-2016).

Cherlyn Ng was born and raised in Singapore, where she went on to earn her BSc in neuroscience and PhD in x-ray crystallography from the National University of Singapore. Drawing upon her earlier experiences with audio/visual production, she received postdoctoral training in computational modeling, psychophysics and developed a deep interest in visual perception. Her current interests focuses on how the brain processes and represents sensory information, with particular emphasis on binocular vision. However, traditional psychophysics does not distinguish between percepts that arise from neural mechanisms and visual limitations that are caused by the imperfect optics of the eyes. She addresses this conundrum by coupling psychophysics with adaptive optics technology. This method removes optical limitations by correcting for the optical aberrations in the eyes so that percepts brought about by the neural mechanisms can be measured in isolation. These measurements serve the eventual purpose of building a unified model that explains how the brain chooses between selecting and balancing information from the two eyes.

I am an assistant professor of vision science at the University of Houston College of Optometry. I received a Master’s Degree in Experimental Psychology from the University of Helsinki, and Ph.D. in Neuroscience advised by Dr. Simo Vanni jointly from the University of Helsinki and the Low Temperature Laboratory of Helsinki University of Technology, Finland. I completed postdoctoral training at the Moran Eye Center of the University of Utah under the guidance of Dr. Alessandra Angelucci. My postdoctoral work with Dr. Angelucci elucidated the neural circuit basis of receptive fields of primary visual cortex neurons in non-human primates. Part of my NIH K99 training was completed under the guidance of Dr. John Reynolds at the Salk Institute for Biological Studies where I worked with awake, behaving marmoset monkeys. My laboratory utilizes electrophysiology, optogenetics, and behavioral techniques in awake and behaving marmosets to elucidate the roles of recurrent connections between cortical areas in visual computation and perception.

Dr. John O’Brien is a native of Maryland growing up just outside the nation’s capital in a thriving community of naturalists, scientists, and government servants. He earned his B.A. in Biochemistry at Bowdoin liberal arts college in Brunswick, Maine and his Ph.D. in Biochemistry at the University of California San Diego. He also completed post-doctoral work at the University of Illinois at Chicago in vision research. There he cloned connexins that form electrical synapses in retinal neurons, setting the stage for a large fraction of the research he has performed since then. In 1998, Dr. O’Brien joined the faculty of University of Texas Health Science Center at Houston in which his lab conducted research on retinal electrical synapses. Dr. O’Brien has published extensively on the topic of retinal neuroscience and continues to receives funding to further research in this area from National Institutes, such as the National Eye Institute. We are happy to welcome Dr. O’Brien as a Professor for the Department of Vision Sciences.

Lisa Ostrin received a Bachelor of Arts degree in Fine Arts at the University of Texas at Austin. She then completed the combined OD/PhD program at the University of Houston College of Optometry in 2006. Following graduate work focused in accommodative physiology, she went to John Hopkins University for post-doctoral research in low vision and retinal prosthetics. From there, she worked as a Clinician Researcher at the University of California Berkeley School of Optometry, with a focus on myopia and associations with glaucoma. She has returned to the University of Houston as an Assistant Research Professor to continue her work in myopia and glaucoma. Dr. Ostrin is a fellow of the American Academy of Optometry and a recipient of the American Optometric Foundation Ezell Fellowship.

Dr. Patel graduated from the Southern College of Optometry, Memphis Tennessee in 2002, after which he completed a residency in Family Practice at Northeastern State University Oklahoma College of Optometry. He completed his graduate work at the University of Houston, earning a PhD in 2012, and has been on the faculty since. His current research is on improving structural measures of the optic nerve head, retinal nerve fiber layer and macula regions using optical coherence tomography, and investigating the relationship between these structural measures and visual function. He also teaches students in the classroom, laboratory and clinical settings.

Visual quality is limited by a host of factors, including imperfections (or aberrations) in the optics of the eye and the health of various cell types in the retina used to detect light and process this information for subsequent delivery to the brain. Using psychophysical, optical and functional imaging techniques, my primary goal is to better understand how the eye's optics and structure of the retina and optic nerve head affect vision in normal and diseased eyes. After completing my BS degree in Optics from the University of Rochester in 1997, I continued my graduate work in Optics at the University of Rochester's Institute of Optics under the advisement of David Williams. My graduate research focused on constructing a clinical wavefront sensor to measure the optical quality of a large population of normal and postoperative laser refractive surgery eyes, and on investigating the sources of aberrations induced in conventional and customized LASIK (laser in-situ keratomileusis) procedures. In collaboration with Ian Cox (Bausch & Lomb) and Scott MacRae (University of Rochester), I examined changes in the eye’s optical quality after cutting a corneal flap and after performing a laser ablation, how aberrations were induced due to static shifts of the pupil (such as changes in pupil center location with dilation), and characterized dynamic eye movements that occur during surgery. I also assisted in the design of the Rochester Adaptive Optics Ophthalmoscope, an instrument capable of both imaging individual photoreceptors and of conducting visual psychophysics in living human eyes.

Upon receiving my PhD in Optics in 2004, I conducted my postdoctoral work with David Williams at the Center for Visual Science (University of Rochester) in the area of high-resolution retinal imaging using adaptive optics. Adaptive optics is a relatively new technology that can measure and correct for the eye’s aberrations, leading to substantial improvements in image quality when a subject looks through an adaptive optics system. Conversely, the same instrument can provide an extremely sharp view of a subject’s retina with the capability of imaging individual cells in a living eye. As a postdoc, I contributed to the construction of a fluorescence adaptive optics scanning laser ophthalmoscope (AOSLO) that can noninvasively acquire in vivo reflectance and fluorescence images of individual photoreceptors, ganglion cells and retinal pigment epithelium cells. In September 2006, I joined the faculty at the University of Houston’s College of Optometry.

Rachel Redfern received her bachelor's degree in biology from Texas A&M University and then her OD/PhD from the University of Houston, College of Optometry. In 2006, Dr. Redfern received the Institutional Ruth Kirschstein National Research Post-doctorate Award and the ARVO/Alcon Early Career Clinician-Scientist Research Award. Dr. Redfern is a member of the Association for Research in Vision and Ophthalmology, the American Academy of Optometry and the Tear Film and Ocular Surface Society. She is also a past William C. Ezell Fellow.

Her laboratory is interested in ocular surface inflammation/infection, the impact of contact lenses (e.g. scleral gas permeable lenses) on normal and diseased eyes and the functional and anatomical changes that occurs in the meibomian glands with age and disease. They perform human subject, animal and in vitro studies. Dr. Redfern’s laboratory is NIH funded to examine the impact of toll-like receptors on the production of damaging cytokines and matrix metalloproteases and beneficial antimicrobial peptides on the ocular surface.

Dr. Ribelayga received his M.S. (1995) and Ph.D. (2000), both in Neuroscience, from the University Louis Pasteur in Strasbourg, France. He then did post-doctoral work at the University of Alabama at Birmingham (UAB) (1999-2005). During this time, he used techniques of single cell recording in the retina to examine how circadian clocks within the retina control the light responses of retinal cells. He joined The Ohio State University (OSU) School of Medicine in Columbus, OH as a Research Assistant Professor (2005-2009) and subsequently moved to The University of Texas at Houston (UTHealth) McGovern Medical School as an Assistant Professor of Ophthalmology. Dr. Ribelayga was promoted to Associate Professor with tenure in 2016 and awarded the Bernice Weingarten Endowed Chair in Ophthalmology in 2019. Dr. Ribelayga joined the University of Houston College of Optometry (UHCO) in 2021, where he is Professor of Physiological Optics and Vision Science. His work has long focused on two areas of research: 1) the role of circadian clocks in the development, maintenance, and function of retinal cells, and 2) the functional architecture of the network of coupled photoreceptors, its plasticity, and the impact of this plasticity on retinal circuit processing and visual perception. Although Dr. Ribelayga’s research accomplishments are primarily in basic science, his work may have important clinical relevance and has been continuously supported by NIH.

Eric Ritchey, OD, PhD, FAAO is a 2001 graduate of The Ohio State University College of Optometry. After graduation, Eric completed a 2-year Advanced Practice Fellowship in Cornea and Contact Lenses at Ohio State, where his research focused on overnight orthokeratology and extended wear contact lenses. Following fellowship, Eric served as a Clinical Assistant Professor at the University of Missouri-Saint Louis College of Optometry before beginning his PhD training at Ohio State. During his PhD training, Eric’s research in the laboratory of Dr. Andy Fischer focused on the mechanisms behind refractive error development. After completing the PhD, Eric joined Johnson and Johnson Vision Care as a Principal Research Optometrist in the Emerging Technologies Group, where he worked on contact lens technologies to control myopia progression. After 4 years in industry, Eric decided to return to academia and will teach Ophthalmic Optics to 2^nd year optometry students. Eric’s clinical interests are in specialty contact lens fitting, anterior segment disease and ocular prosthetics. His research activities will focus on myopia development and contact lenses.

Dr. Abirami Santhanam received her doctorate degree in Biochemistry at the National Taiwan University, Taiwan. She got the opportunity to work with Dr. Steven Wilson from Cleveland Clinic on corneal wound healing and regeneration during her postdoctoral career and has contributed to the understanding of the role of growth factors and receptors in corneal development that are important to treat the pathophysiological conditions that affect the cornea after surgery, infection, or trauma. She established the Laser capture-based microdissection technique on the cornea to understand the role of stromal proteins. Then she got the opportunity to work with Dr. John O’Brien on retina regeneration. The regenerative power of Zebrafish combined with single-cell transcriptome analysis provided an excellent system to understand the exciting molecular mechanisms of regeneration in the retina. She has established a Retinitis Pigmentosa (RP) model in the zebrafish to understand the regeneration of rod cells that are degenerated in human RP conditions. Currently, her lab is in the process of identifying the key factors that turn on and regulate this regeneration that can be translated into the mammalian system to turn on regeneration successfully. Her long-time research interest is to contribute more towards the understanding of the complex controls and molecular mechanisms in signal transduction pathways involved in vision restoration.

Dr. Kaitlyn A. Sapoznik received her Doctor of Optometry from Illinois College of Optometry in 2013 and then completed a one-year ocular disease residency at Indiana University School of Optometry in Bloomington, IN. Following her residency, she completed her Ph.D. in Vision Science at Indiana University. Her research uses high-resolution retinal imaging techniques like adaptive optics retinal imaging to better understand retinal microvascular remodeling in aging and disease with an emphasis on diabetic retinopathy. Dr. Sapoznik was awarded the Vision Impact Institute Ezell Fellowship for two-consecutive years.

Scott Stevenson received his PhD in Experimental Psychology from Brown University in 1987 for studies of visual suppression during eye blinks. He was an NRSA post-doc at UC Berkeley School of Optometry for three years, and then joined the research faculty there. Dr. Stevenson joined the faculty at UH in 1995.

Dr. Stevenson’s research concentrates on the visual control of eye movements, with emphasis on visually driven eye movement reflexes, such as for the control of eye alignment. Dr Stevenson is also active in the development of eye trackers based on high magnification retinal imaging in a broad collaboration involving researchers at a number of other institutions.

Dr. Stevenson teaches in courses on Vision Science, Perception, Optometry, Eye Movements, and Matlab for Vision Science.

Dr. Stevenson serves on the Editorial Board for Vision Research, and is a member of the Vision Sciences Society.