Implants versus eye drops
A NEW glaucoma injection with slow-release medication that lasts for a few months is being researched in clinical trials here and worldwide.
Many people with glaucoma find it a hassle to use eye drops daily, and as a result, sometimes forget to apply them. If this happens too often, they risk worsening their vision or even irreversible blindness.
To address this and other problems with the long-term use of conventional eye drops, some slow-release formulations are being tested in Singapore and around the world.
One of them is a sustainedrelease, biodegradable implant, or pellet, injected into the eye. It contains bimatoprost, a drug which is commonly used to treat glaucoma. It is inserted into the anterior chamber of the eye between the cornea and the iris, where it slowly releases its medication over three to six months.
In Singapore, the Phase 3 clinical trials of this injection are being carried out at the Singapore National Eye Centre ( SNEC), the Singapore Eye Research Institute ( SERI), the National University
Hospital, Khoo Teck Puat Hospital, and Changi General Hospital.
In Singapore, 3- 4 per cent of people over 50, almost 10 per cent over 70, and more than 10 per cent over 80 have glaucoma, said Professor Aung Tin, Senior Consultant and Head, Glaucoma Department, SNEC, and Executive Director, SERI.
Worldwide and here, it is the leading cause of irreversible blindness. It occurs when the optic nerve is damaged by high fluid pressure in the eye.
The use of topical eye drops can curb this increase in pressure and slow the progression of the disease, but it’s not a cure.
“The majority of people are treated with eye drops. Some need to use two or three different ones, so after a while it becomes difficult. Five to six out of 10 glaucoma patients here and worldwide fail to stick to the daily eye drop regimen,” said Prof Aung.
“Eye drops work but there are two problems,” said Dr Rahat Husain, Senior Consultant, Glaucoma Service, SNEC, and also an Adjunct Associate Professor, Duke-NUS Medical School: “People forget or get lazy to use them. And eye drops can irritate the eye’s surface, causing red or itchy eyes. Potentially, this intraocular implant will solve both these issues.”
The pellets treat open angle glaucoma, the most common form of the illness, but they are unsuitable for closed angle glaucoma. The injection is simple, painless and done in seconds. After applying anaesthetic drops to numb the eye, doctors use a hand-held device to inject the less-than1mm implant into the eye. No stitches are needed because the area the needle enters is selfsealing.
“One injection lasts at least three to four months. Over time, the pellet slowly biodegrades and disappears,” said Prof Aung.
No infections have occurred so far in the trials, said Dr Shamira Perera, Senior Consultant, Glaucoma Service, SNEC, and Co-Head of Bioengineering and Devices, SERI.
Local trial patients have taken easily to the new treatment. A 60year- old senior customer service officer, who’s had glaucoma for more than a decade, favours the implant over daily eye drops and has no issues with it.
“The procedure is fast and painless. Before the trial, I had to put eye drops in every night. I found it troublesome and would occasionally forget to use them,” she said.
The bimatoprost implant is one of several methods being studied. These include other implants with slow release drugs for glaucoma, laser therapy, a punctual plug placed into the tear duct, and injecting a solution of the prescribed drug under the surface layer (sclera) of the eyeball.
Dr Perera, who is also an Adjunct Associate Professor with Duke-NUS Medical School, said that all these open up exciting possibilities to help glaucoma patients in future.
“It would be interesting to see if the different implants can work together. Perhaps eye drops could be used together with an implant in some cases, or two implants could be deployed in different parts of the eye.”
Prof Aung said that in 10 to 15 years there may come a day when glaucoma patients can choose their preferred method of treatment – eye drops, a punctal plug in the tear duct, or an implant injected into the eye. “This could happen in the future. Maybe all the different technologies will be used.”
• This story was first published in Singapore Health, Mar-Apr 2017 issue.