Bascom Palmer Researchers Develop First Slit-Lamp Diagnostic Instrument for Imaging Both Microvascular Networks and Blood Flow
A team of Bascom Palmer Eye Institute researchers has developed a new slit-lamp diagnostic instrument that can capture clear diagnostic images of the complex network of capillaries in the conjunctiva at the front of the eye, and take videos to track the flow of blood through those vessels. The study was led by Hong Jiang, M.D., Ph.D., assistant professor of ophthalmology at Bascom Palmer Eye Institute at the University of Miami Miller School of Medicine
“Our functional slit-lamp biomicroscopy (FSLB) has a huge potential for diagnosing ocular, systemic and cerebral vascular diseases,” said Jiang. “Because of its low cost and ease of use, this non-invasive instrument could allow physicians around the world to better understand their patients’ microvascular networks and blood circulation, helping them treat a wide range of conditions.”
Jiang was the lead author of study, “Functional slit lamp biomicroscopy for imaging bulbar conjunctival microvasculature in contact lens wearers,” published in January in Microvascular Research. Other Miller School authors were Bascom Palmer’s Delia Cabrera DeBuc, Ph.D., research associate professor of ophthalmology; Jianhua (Jay) Wang, M.D., Ph.D., associate professor of ophthalmology; Byron L. Lam, M.D., professor of ophthalmology; Jianguang Zhong, M.D., research associate; Aizhu Tao, M.D., M.Sc., research associate; and Che Liu, M.S., research associate, department of biomedical engineering.
In the study, the Bascom Palmer team attached a Canon digital camera to a traditional slit-lamp microscope – used by ophthalmologists and optometrists worldwide for eye examinations – and took high-definition images of conjunctiva. Using the camera’s “movie crop function,” the researchers also videotaped the blood flow at a rate of 60 frames per second with 210x magnification – much greater than the 40x magnification of traditional slit-lamp microscopes.
“To the best of our knowledge, simultaneous measurement of the blood flow velocity in bulbar conjunctival vessels and their network complexity has not been fully explored due to technical difficulties,” said Jiang, who is also assistant professor of neurology. She noted that the bulbar conjunctiva – which covers the surface of the eye – is similar to the network of small blood vessels in the kidneys, liver and other organs. Therefore, understanding the microvascular structures could provide clinical insights into hypertension, diabetes and other chronic disease conditions.
Six subjects were imaged before and after six hours of wearing contact lenses in order to obtain comparative images of the microvascular network. The researchers found alterations to the subjects’ blood vessels from wearing the contact lenses. “Understanding those microvascular changes may help clinicians address contact lens problems, as well as hard-to-treat conditions like dry eye and conjunctivitis (“pinkeye”),” said Cabrera DeBuc. “It could also help contact lens and solution manufacturers develop better products since clinical results could be measured more accurately.”
The researchers used proprietary software developed at Bascom Palmer to analyze the microvascular network, as well as blood vessel diameter, blood flow velocity and flow rate. Starting with the magnified still images of the conjunctiva, the researchers produced high-resolution, non-invasive microvascular perfusion maps (nMPMs). Fractal analysis has been used in various branches of medicine – including the study of large blood vessels – to show differences in the structural patterns of cells, tissues and organs.
With fractal analysis, it is possible to provide a global and more natural description of complex branching structures, and Bascom Palmer researchers have used a similar approach to analyze the microvasculature network in the retina.
Jiang said fractal analysis of the conjunctiva may be a highly effective way to determine the health of the capillary network, because the blood vessels at the front of the eye are more easily seen than those of the retina. “We can also study the conjunctiva without concerns for retinal problems, such as age-related macular degeneration (AMD), which could affect the microvascular structure,” she said.
Wang said he hopes the high quality of the microvascular images and videos, combined with the relatively low cost of Bascom Palmer’s patent-pending FSLB, will lead to worldwide adoption of this “next generation” diagnostic technology. “Now, we need to conduct clinical trials that will allow us to categorize the microvascular networks and see how they change in response to various diseases. That will be the next big step forward.”
The study was funded by a research supplement to Jiang, part of an NIH R01 grant awarded to Cabrera DeBuc.