GLAUCOMA sufferers can now heave a sigh of relief as medical scientists at the Feinberg School of Medicine, Northwestern University, Chicago, USA, have discovered a new cause for the disease and could, therefore, develop a cure for the hitherto incurable condition.
Glaucoma occurs as a result of increased pressure within the eyeball (intraocular pressure, IOP). When this pressure which is due to poor drainage of fluid from the anterior chamber of the eye (which can be likened to a clogged pipe), exceeds its healthy pressure level, it damages the optic nerve, leading to gradual irreversible loss of sight.
It is estimated that about 50 per cent of people in the developed world do not know that they have glaucoma while the figure is about 90 per cent in developing world, including Nigeria.
The pipe, known as Schlemm’s canal or scleral venous sinus, is a circular channel in the eye that collects aqueous humor from the anterior chamber and delivers it into the bloodstream through the anterior ciliary veins.
According to the study published in The Journal of Clinical Investigation, the researchers led by Susan Quaggin, MD, Director, Feinberg Cardiovascular Research Institute and Chief, Division of Medicine-Nephrology, the new study identified “the molecular building blocks needed to make the drainage vessels, providing the necessary chemical tools to repair the eye’s plumbing and restore normal drainage.
Up until now, the molecular basis of the disease caused by an absent or defective canal was unknown.”
The discovery:“The study identified an important chemical- signalling pathway for the healthy functioning of Schlemm’s canal and the substances necessary for its growth and development.
“That pathway requires the chemical equivalent of a lock and key to open. The lock is a substance called Tie2 and the key is a growth factor called angiopoietin.”
According to the study, “if either the key (angiopoeitin) or the lock (Tie2) is missing in mice, they cannot make Schlemm’s canals and will develop glaucoma.”
The findings are based on a new mouse model of glaucoma developed by Quaggin and graduate student, Ben Thomson.
“This is a big step forward in understanding the cause of the disease that steals the eyesight from 60 million people worldwide and this gives us a foothold to develop new treatments. Our goal now is to grow new ‘pipes’ or vessels to cure the glaucoma,” said Quaggin who is working in collaboration with Amani Fawzi, MD (associate professor of ophthalmology) and Xiaorong Liu, (assistant professor of ophthalmology), both at Feinberg, and Northwestern scientist, Samuel Stupp to develop a nanofiber eye drop that activates re-growth of the clogged vessel.
“We are developing a highly potent peptide nanostructure that has the capacity to interact with many receptors at the same time,” Stupp said. “This will amplify the required signalling pathway for an effective therapy. The nanostructure is also being designed to have the necessary half-life to optimize efficacy.”
Quaggin said the team hopes to grow a bigger Schlemm’s canal in people with glaucoma to lower the pressure in the eye. “That’s what we’re hoping for with this new eye drop.
“We really nailed that pathway as being critical. Now we know these two substances are key factors in the development of glaucoma, which wasn’t known before. The mouse model is so similar to what we see in patients with glaucoma,” she said, adding: “Now we can understand how raised pressure leads to the damage of the neurons in the optic nerve.”
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