Macular degeneration is a progressive blindness caused by forms of age-related damage that disable and destroy cells of the retina, such as the accumulation of persistent forms of metabolic waste. The dry variant of macular degeneration, in which there is no great degree of inappropriate blood vessel growth in the retina, has no effective treatment at the present time – and treatments for the wet form typically only slow progression. The materials noted here discuss progress towards a precision heat therapy that uses a laser to induce mild cell stress and consequently greater cell maintenance activities in retinal tissue. If used in the early stages of the condition, animal studies suggest it can significantly postpone the onset of more severe degeneration.
The new heat treatment involves heating the retinal pigment epithelium at the back of the eye (at the fundus) with near-infrared laser and precise temperature control. The objective is to halt the development of the condition in its early stages and to prevent it from progressing to the dry or wet form. Heat treatment of the fundus is not a new invention, but until now, it has not been possible to monitor the temperature of the retinal pigment epithelium while the treatment is administered. This is essential in order to avoid damage to the tissues being treated.
The causes of macular degeneration include oxidative stress and the resulting protein misfolding and aggregation. A heat treatment for the back of the eye strengthens the defence mechanisms of retinal cells. These mechanisms help proteins refold back into their correct forms, and at the same time stimulate the natural healing process. In the new heat treatment, the temperature elevation of the fundus is determined from the acceleration of electrical signalling of retinal nerve cells in response to light stimuli and the signals can be registered in real-time from the surface of the eye using electroretinography. With this method, the voltage change caused by light flashes is measured using electrodes placed on the surface of the eye and the skin near the eye.
The temperature determination method has been shown to work in tissue research on mice and pigs, and preclinical tests for the heat treatment have begun. The goal of the commercialisation project is to enable the use of heat treatment in humans, and the design and construction of the treatment device is currently under way.
