Tiny cup attached to eye improves drug delivery for retinal diseases

A drug delivery system that uses a tiny silicone cup filled with any drug and sealed to the outer surface (episclera) of the eyeball may offer an effective method for the sustained delivery of medicines for retinal and vitreous diseases, according to US researchers.

Dr A Linn Murphree, director of the retinoblastoma programme in The Vision Center at the Children's Hospital Los Angeles, US, said in a presentation to the Association for Research in Vision and Ophthalmology (ARVO) that the device, called an episcleral drug reservoir, has the potential to change fundamentally how we deliver medications to the eye for diseases such as macular degeneration, diabetic retinopathy, uveitis, endophthalmitis and retinoblastoma. Working much like an organ-specific transdermal skin patch, the tiny cup isolates the medication targeted to the eye from being absorbed into the blood stream.

This new delivery system is a safe and non-invasive way to deliver effective doses of medications to the interior of the eye over long periods of time (weeks to months). Currently drops, periocular injections and intraocular injections are used to deliver medications to the eye but generally for short periods of time.

Dr Murphree, who is a recipient of a National Institutes of Health RAID grant which provides funding for the development of procedures leading to clinical trials, believes the development of this type of delivery device represents a major shift in the way physicians will deliver drugs to all organ systems in the future.

"The implantation of this kind of device on any organ and the ability to deliver medication to the affected organ, could be a huge advance in how we currently treat cancer," Dr Murphree said. The research was carried out with Dr Ricardo Carvalho and 3T Ophthalmics, the developer of the drug delivery system.

The episcleral drug reservoir is inserted under the covering of the eyeball to the sclera (fibrous, protective outer layer of the eye). The tiny cup administers the drug slowly by passive diffusion through the sclera, where it reaches the retina and vitreous. The device is so small the patient should feel little or no discomfort and it does not hinder normal vision, the company says.

Drugs for most retinal diseases are currently delivered either through an IV drip or by an injection into the eyeball, both of which pose risks for the patient.

"When we administer chemotherapy to an infant for retinoblastoma at The Vision Center, it is expensive and puts a great strain on the family, especially if they are from another state. Our preliminary research shows that once the cup is fitted, the child should be able go home for several weeks. Because the drug is being administered directly into the eye and not systemically, chemotherapy dosage levels will be much lower and the debilitating side effects will be reduced," said Dr Murphree.

With preliminary testing complete, Dr Murphree is currently developing a protocol for Phase I/II clinical trials in humans to take place over the coming year.