At age 40–45, if you find you have to hold a book further away to read it, you may have developed presbyopia: an ageing-related condition in which the eye’s ability to focus on near objects is reduced as its lens progressively stiffens. At this point in life, some people visit an optometrist for the first time. Suddenly they need glasses – and will for the rest of their lives.
If Dr Paul Erickson has his way, however, future generations may be heading straight to an ophthalmic surgeon to have a revolutionary ‘accommodating gel’ injected into their eyes.
Originally from Pennsylvania, USA, Erickson has led the accommodating gel project since 2010 with significant funding from the Vision CRC. He is the CEO of Brien Holden Vision Pty Ltd and Adventus Technology Inc – companies through which Vision CRC participant the Brien Holden Vision Institute develops and commercialises its technologies.
DEFINING THE PROBLEM
The crystalline lenses in our eyes can adjust their focal length (or ‘accommodate’) by changing shape – bulging or flattening according to the tension in fibres that connect the lens to the circular muscle surrounding the lens capsule. It’s a very flexible lens, but it evolved for a species that lives to around 40 years old, Erickson explains.
“During a person’s life, the lens material loses its softness and flexibility, and at around age 40 the loss begins to accelerate,” he adds. “It reaches a point where it’s very difficult for the stiffer lens to change its shape in order to see at a normal reading distance.”
The accommodating gel project aims to replace the stiff natural lens with a new lens made from a siloxane gel – a compound of silicone. First, the non-functioning natural lens would be extracted through a procedure similar to surgery for cataracts (lenses which have become opaque). Then, the gel would be injected into the transparent lens capsule.
Finding a suitable material to replace the lens has been a 20-year search, says Erickson. The requirements are stringent: it must be a moderately viscous liquid that can be injected, and it must polymerise into a soft, flexible gel. It also has to be biocompatible and, of course, transparent. Developed in Australia, the gel is being trialled in rabbits.
“We’re fine-tuning the properties,” says Erickson. “Over the next two to three years, we hope to move into animal models that more closely resemble humans, and then on to human subjects.”
Erickson’s team works with the prestigious Bascom Palmer Eye Institute in Florida, USA. The partnership has already led to improved medical microscopic imaging technology for use during the procedure, which could immediately benefit eye surgeons conducting cataract operations, Erickson says.