Glaucoma, the leading cause of blindness, affects 67 million people worldwide and is often associated with high pressure levels in the eye related to fluid buildup. Although researchers previously bought into a paradigm that viewed the eye as being anatomically isolated from the body’s lymphatic system, U of T’s Dr. Yeni Yücel, professor and director of ophthalmic pathology in the Department of Ophthalmology and Vision Sciences, sensed that something didn’t add up.
After a critical review of the existing literature, Yücel and his research team of specialists began to question the nature of inflammatory diseases affecting the eye. They knew that lymphatics in the rest of the body drained excessive fluids and proteins, and that processes in the eye were less well understood. To date, studies showed that the eye’s drainage process led directly to the blood, but Yücel wanted to know what, and if, anything from the eye was going into the lymphatic system.
Throughout the year, the Faculty of Medicine department heads showcase different research projects in order to attract private donations. “One day they talked about our research,” said Yücel, “and that funding was critical.”
The project then took off full blast. The team ran a series of experiments assessing various aspects of the eyeball and the lymphatic system via chemical testing and under a microscope. Yücel, the corresponding author for the project, thoroughly describes the details in the groundbreaking study “Identification of lymphatics in the ciliary body of the human eye: A novel ‘uveolymphatic’ outflow pathway” published in the journal Experimental Eye Research.
The results of these controlled experiments ultimately indicated that there are lymphatic channels in the ciliary body of the eye—the thin smooth muscle and blood vessel-filled layer of the eye between the sclera (commonly referred to as the white of the eye) and the retina (the nerve layer lining the back of the eye that senses light and sends signals through the optic nerve to the brain).
The implications of this scientific breakthrough are huge and its relevance to the world of medical research is several-fold.
“First, the fact we were able to find the lymphatics suggests that the eye is not really anatomically isolated from the rest of the body regarding the immune system. Second, pressure in the eye is a major risk factor for glaucoma. Our finding suggests that there is a completely new pathway where fluids can be drained from in the eye to lower the pressure for glaucoma patients. Lastly, there are tumors that can develop in the eye. We think [this research] might be important for regulating the spread of tumors outside of the eye,” said Yücel.
However, the discovery of lymphatic channels left the researchers facing a multitude of open-ended questions. Their next steps will be to try and find the extent to which lymphatics are involved in fluid drainage in the eye.
For Yücel, this is just another integral part of his adventure as a scientist. He attributes much of the project’s success to his collaboration with renowned fellow colleagues, glaucoma specialist and eye surgeon Dr. Neeru Gupta and lymphatic physiologist Dr. Miles Johnston. “Everything started through the contact of teaching. The environment at U of T allowed the best minds to collaborate and work. [Dr. Gupta, myself and our team] showed that technically in the human eye there are lymphatics, and afterwards [Dr. Johnston and his team] were able to show that the lymphatics were functional.”
According to Yücel, one of the most important aspects of this project is that it shows that there are still some wonderful things in the human body to be found. “With new techniques, markers, and fresh ideas, we can make discoveries. We are excited about it.”
