There are many avenues available to ophthalmologists to treat intraocular pressure (IOP). Numerous medications, surgical treatments like trabeculectomy, laser therapy like MicroPulse transscleral cyclophotocoagulation, or even good old fashioned cannabis can be effective in lowering IOP.
However, South Africa’s Dr. Daemon McClunan and his company Liquid Medical have devised new surgical implants that show great promise in lowering IOP. These devices are called the OptiShunt and iPortVR, and they may lead to a paradigm shift in IOP treatment. Dr. McClunan won an award for the OptiShunt in 2019 from South Africa’s SAB Foundation Social Innovation and Disability Empowerment Awards.
IOP treatment is crucial in preventing blindness, as glaucoma is the leading cause of irreversible blindness worldwide. Patients with blindness suffered higher IOP, wider variation in IOP, and poor control of IOP than glaucoma patients who did not develop blindness.
Translaminar Pressure
If there’s no wind, the tree won’t blow over.
Speaking at the World Ophthalmology Congress (WOC2020 VirtualⓇ) conference, Dr. McClunan identified translaminar pressure as the root cause of glaucoma. As he put it, “There is a growing body of evidence in the literature that supports our hypothesis that translaminar pressure is actually the root cause of glaucoma. Other factors such as age, genetics, biomechanics and vascular factors merely determine how resilient the optic nerve head is to withstanding the force applied to it by translaminar pressure. If the stress outweighs the resilience, then deformation in the form of glaucoma occurs.” A study referenced in his discussion illustrated that no patient who was absent translaminar pressure developed visual field defects.
He compared an eye to a tree, and translaminar pressure to wind. Some trees are stronger and better rooted than others, so they can survive stronger winds. Age, genetics and numerous other factors affect an eye’s resilience to the effects of translaminar pressure. Other “trees” have weaker roots and trunks, so are more easily damaged. But why worry about the tree when you can simply eliminate the wind?
Oculosubarachnoid shunting is the solution proposed by Liquid Medical. Rather than draining excess fluid to an artificial blister on the eye — which can lead to bleb-related complications and recurring pressure — this method drains fluid through the natural fluid reserve in the retrolaminar subarachnoid space.
OptiShunt and iPort VR
By making excess ocular fluid take a detour, IOP is reduced.
One of the main benefits of utilizing the subarachnoid space is that it’s self-regulating and presents no possibility of developing a bleb. Both the OptiShunt and the iPort VR tap into the subarachnoid space to achieve long-lasting and controllable pressure reductions in IOP.
The OptiShunt creates an open shunt communication between the anterior chamber and the retrolaminar subarachnoid space. The iPort VR, on the other hand, creates a microshunt between the posterior chamber and the retrolaminar subarachnoid space.
The Glaucoma treatment by OculoSubarachnoid Shunt Insertion Pilot (GOSSIP) study, an early feasibility study for the OptiShunt, demonstrated significant reduction in IOP and very low complication rates. How much, you ask? There was a 74% reduction in mean IOP, from 41mmHg to 11mmHg, with 100% success in lowering IOP and an 80% reduction in medication usage.
The GOSSIP study further showed no severe adverse events, no intraoperative adverse events and no unexpected adverse events at three months.
The OptiShunt relies on a novel Orbital Retractor that allows safe access to the optic nerve. According to Liquid Medical, a single surgeon can use the Orbital Retractor to access the optic nerve in as little as eight minutes.
The iPort VR is undergoing preclinical testing, with clinical trials set to begin in 2021.
A Paradigm Shift?
If these devices do indeed fulfill the promise they show, they could lead to new, safe, and potentially permanent solutions to managing IOP. Dr. McClunan noted these techniques are valuable for treating severe glaucoma, which many minimally-invasive surgeries cannot quite tackle. We’ll wait with bated breath for the next round of trials to commence. If the data is good, there could well be a welcome revolution in glaucoma treatment.
