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Research activities in the Visual and Biomedical Optics Lab
We are performing interdisciplinary research with a focus on applying optical engineering principles for vision care and biomedicine. The eye is one of the most crucial organs of the human body. More than 80% of the information we obtain is through the eye. Our goal is to improve the quality of life for a large population in the world through personalized vision care. Specifically, our current research includes two directions. One is on the design, fabrication, characterization, and clinical application of active and passive adaptive lenses for individualized vision correction, and the other is on high-speed, high-resolution, three-dimensional, live optical imaging for diagnosis of ocular diseases and for observation of neuronal connections, dynamics and function.
The natural human eye is a perfect adaptive lens imaging system. With accommodation of the crystalline lens, objects at different distances can be imaged sharply onto the retina. However, with aging, the natural lens gradually loses its accommodation ability, resulting in inability to shift focus from distant to near objects, a symptom called presbyopia. Almost everyone on this planet starts to develop presbyopia at 40-45 years of age. Also with aging, a clouding may develop in the crystalline lens, obstructing the passage of light and causing blindness, a symptom called cataract. Recent findings in development of myopia reveal that correction of the peripheral vision may play an important role and this means that an eyeglass with spatially variable and programmable power would be helpful. These are just a few examples of scenarios in vision correction. To care for the vision of such a large population is of great value in terms of socioeconomic cost, academic research and technology commercialization. To address these needs, we are developing adaptive liquid crystal lenses and liquid lenses for vision correction and assessment, and also applying wave front-coding technique for extension of depth of field of the vision system. These techniques can be exploited for spectacle, contact, and intraocular lenses. Ultimately it would be great if autofocus function can be added to the vision correcting elements using optoelectronic controllers.
There are a variety of diseases that are associated with each part of the eye, including the cornea, aqueous humor/anterior segment, crystalline lens, vitreous humor, retina, choroid, sclera, etc., and any disorder or disease may result in significant visual impairment or even blindness. With aging, people may develop vision-threatening diseases such as glaucoma, age-related macular degeneracy, diabetic retinopathy, cataract, etc. Currently a few million of the US populations are suffering from each of these diseases. With the span of life expectancy, the number of people diagnosed with these diseases is increasing rapidly. The structural changes due to many of these diseases are irreversible. Early diagnosis, prevention, and control of eye diseases are extremely important. Optical imaging systems are indispensable tools for early diagnosis of these eye diseases, where both structural and functional changes in the eye tissues can be tracked and monitored. In general, for ophthalmic imaging, high speed is always desirable to avoid the effect of eye movement, so high-performance optical and electronic devices are needed and well integrated into a system; high resolution is also required for cellular and three dimensional imaging of layered retinal structures, and an adaptive optics unit is needed to correct the higher-order aberrations of the eye. The closed-loop adaptive optics unit consists of a wavefront sensor and a wavefront corrector. In three-dimensional biomedical optical imaging, images at different depths are usually obtained by mechanical movement of the optics or the biomedical sample. It would be great if the objective lens has the accommodation like the human eye and this can be achieved using an active lens with dynamic focusing powers.
Large-scale recording and imaging neural activities will provide unprecedented opportunities for exploring how the nervous system encodes, processes, utilizes, stores, and retrieves vast quantities of information. The retina is the most approachable part of the central nervous system and is the only neural tissue that can be imaged non-invasively. A better understanding of this dynamic neural activity will enable researchers to seek new ways to diagnose, treat, and prevent visual disorders such as glaucoma and macular degeneracy. Neural activities occur at millisecond scale. We are investigating optical imaging systems that allow in-vivo imaging at cellular level with the capability of recording millisecond-scale event signals and imaging a 1 mm3-volume in less than 1 second. Combining the neural imaging techniques with optogenetic approach provides exciting potential for the restoration of vision in patients with incurable degenerative retinal diseases such as retinitis pigmentosa and macular degeneration.
There are various biomedical optical imaging modalities. For ophthalmic imaging, full-field imaging with flood illumination, confocal imaging, and optical coherence tomography imaging are based on back scattered light from the tissue. Photoacoustic imaging is an emerging technique that allows three-dimensional map of the absorption properties of the tissue. Many ocular tissues such as cornea, Henle nerve fibers, retinal nerve fiber layer, choroid, and sclera, have birefringent properties. Quantitative measurement of the birefringence and thickness of these tissues are critical for objective diagnosis of diseases and wounds of these regions. The periodic fiber structures in the eye can generate second harmonic signal upon excitation of femtosecond laser pulses in the near infrared and hence changes in these structures can be monitored. Two-photon fluorescence imaging also plays an important role in structural and functional imaging of the retina.
Correspondingly, we are interested in the following research:
Active and passive adaptive lenses for vision correction, including spectacle, contact, and intraocular lenses; accommodation
High-speed confocal ophthalmoscope (microscope); polarimeter
High-speed high-resolution optical coherence tomography (OCT), including Fourier-domain OCT, polarization-sensitive OCT, and optical coherence microscope
High-speed two-photon/second-harmonic-generation imaging of the eye
Wavefront-coded ophthalmoscope (microscope) with extended depth of field and depth extraction
Artificial materials for vision care
Liquid crystals for electro-optic devices and biomedical sensor
Our research has been funded by Wallace H. Coulter Foundation (Career Award) and National Institute of Health (through National Eye Institute, National Institute of Biomedical Imaging and Bioengineering, and National Institute of General Medical Sciences).
Information about the facilities and equipment of the lab can be found under Facilities. Our research activities require extensive collaborations among engineers, life scientists, and clinicians. We offer an active, supportive, and interdisciplinary research environment for the postdoctoral researchers and students.
Highly-motivated and hard-working candidates are always encouraged to apply for Ph. D. or postdoctoral researcher positions.
For postdoctoral researcher positions, the candidates may have skills in one or more of the following fields: (1) optics; (2) microfabrication; (3) system integration/signal processing; (4) liquid crystals/hydrogel; (5) vision science.
Permanent positions are available for outstanding researchers.