Optical Doppler tomography (ODT) is a branch of optical coherence tomography (OCT) that can measure the speed of a
blood flow by measuring the Doppler shift impinged on the probing sample light by the moving blood cells. However,
the measured speed of blood flow is a function of the Doppler angle, which needs to be determined in order to calculate
the absolute velocity of the blood flow inside a vessel. We developed a technique that can extract the Doppler angle from
the 3D data measured with spectral-domain OCT, which needs to extract the lateral and depth coordinates of a vessel in
each measured ODT and OCT image. The lateral coordinates and the diameter of a blood vessel were first extracted in
each OCT structural image by using the technique of blood vessel shadowgram, a technique first developed by us for
enhancing the retinal blood vessel contrast in the en face view of the 3D OCT. The depth coordinate of a vessel was then
determined by using a circular averaging filter moving in the depth direction along the axis passing through the vessel
center in the ODT image. The Doppler angle was then calculated from the extracted coordinates of the blood vessel. The
technique was applied in blood flow measurements in retinal blood vessels, which has potential impact on the study and
diagnosis of blinding diseases like glaucoma and diabetic retinopathy.
Among birds, raptors are well known for their exceptional eyesight, which is partly due to the unique structure of
their retina. Because the raptor retina is the most advanced of any animal species, in vivo examination of its structure
would be remarkable. Furthermore, a noticeable percentage of traumatic ocular injuries are identified in birds of
prey presented to rehabilitation facilities. Injuries affecting the posterior segment have been considered as a major
impact on raptor vision. Hence, in vivo examination of the structure of the posterior segment of the raptors would be
helpful for the diagnosis of traumatized birds. The purpose of this study is to demonstrate the application of
ultrahigh-resolution Spectral Domain Optical Coherence Tomography (SD-OCT) for non contact in vivo imaging of
the retina of birds of prey, which to the best of our knowledge has never been attempted. For the first time we
present high quality OCT images of the retina of two species of bird of prey, one diurnal hawk and one nocturnal
owl.
The integrity of the tear film on the surface of contact lenses is essential to maintaining visual clarity and the overall
health of the superficial structures of the eye (cornea and conjunctiva) for contact lens wearers. It is very critical to
evaluate pre- and post-lens tear films in contact lens practice to make sure the lens is properly fitted. Improper lens
fitting may cause ocular discomfort, visual distortion and ocular infection. It is very often for soft contact lens wearers to
experience dry eye, especially in the afternoon after wearing the lens for a period of time. Dry eye has been a common
cause of contact lens drop-off. There is currently no method available to directly visualize the tears on and underneath
the contact lens in situ on human eye, mainly due to the extremely difficulty in imaging the micrometer-thin tear layer.
An ultra-high resolution spectral domain optical coherence tomography has been developed with a telecentric light
delivery system mounted with a slit-lamp. The system has a 3 micrometer depth resolution with a scan width up to 15
mm. The system was used to image soft contact lenses on the human eye. For the first time to our knowledge, tear films
on the center and edge of the soft contact lens were directly visualized in vivo.
Noninvasive in vivo examination of the rodent retina without sacrificing the animal is the key to being able to perform
longitudinal studies. This allows the monitoring of disease progression and the response to therapies through its entire
course in individual animal. A high-speed high resolution three-dimensional spectral-domain OCT is built for non-contact in vivo imaging of rodent retina. The system is able to acquire high quality 3D images of the rodent retina in 2.7
seconds (total imaging time is ~5 minutes). The system was tested on mice with normal retina (B6/SJLF2), mouse model
for photoreceptor degeneration (Rho-/-), and mouse model for retinoblastoma (LHBETATAG). For the first time to our
knowledge, 3D image of the tumor in retinoblastoma mouse model was successfully imaged in vivo. By segmenting the
tumor boundaries in each frame of the OCT image the volume of the tumor was successfully calculated.
Measurement of retinal blood vessel parameters like the blood blow in the vessels may have significant impact on the
study and diagnosis of glaucoma, a leading blinding disease worldwide. Optical coherence tomography (OCT) is a noninvasive
imaging technique that can provide not only microscopic structural imaging of the retina but also functional
information like the blood flow velocity in the retina. The aim of this study is to automatically extract the parameters of
retinal blood vessels like the 3D orientation, the vessel diameters, as well as the corresponding absolute blood flow
velocity in the vessel. The parameters were extracted from circular OCT scans around the optic disc. By removing the
surface reflection through simple segmentation of the circular OCT scans a blood vessel shadowgram can be generated.
The lateral coordinates and the diameter of each blood vessel are extracted from the shadowgram through a series of
signal processing. Upon determination of the lateral position and the vessel diameter, the coordinate in the depth
direction of each blood vessel is calculated in combination with the Doppler information for the vessel. The extraction of
the vessel coordinates and diameter makes it possible to calculate the orientation of the vessel in reference to the
direction of the incident sample light, which in turn can be used to calculate the absolute blood flow velocity and the
flow rate.
The purpose of this study is to demonstrate the application of ultrahigh-resolution Spectral Domain Optical Coherence Tomography (SD-OCT) for non contact in vivo imaging of the retina of small animals and quantitative retinal information extraction using 3D segmentation of the OCT images. An ultrahigh-resolution SD-OCT system was specifically designed for in vivo retinal imaging of small animal. En face fundus image was constructed from the measured OCT data, which enables precise registration of the OCT images on the fundus. 3D segmentation algorithms were developed for the calculation of retinal thickness map. High quality OCT images of the retina of mice (B6/SJLF2 for normal retina, Rho-/- for photoreceptor degeneration and LHBETATAG for retinoblastoma) and rats (Wistar for normal retina) were acquired, where all the retinal layers can be clearly recognized. The calculated retinal thickness map makes successful quantitative comparison of the retinal thickness distribution between normal and degenerative mouse retina. The capabilities of the OCT system provide a valuable tool for longitudinal studies of small animal models of ocular diseases.
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