SAMADI

SAponins for MAcular DIsease: an exploratory randomised controlled trial (RCT).

The aim of the SAMADI trial [SAponins for MAcular DIsease: an exploratory randomised controlled trial (RCT)] is to establish whether treatment of age-related macular degeneration (AMD) with oral glycoside supplements is feasible and acceptable to patients.

AMD is the most common cause of visual impairment in developed countries, the condition affects the central region of the light sensitive retina at the back of the eye which is known as the macular, the region responsible for seeing detail and colour. One of the factors that contributes to the disease, is a build-up of waste material around the membrane between the retina and the underlying layer of blood vessels. These blood vessels supply the retina with oxygen and nutrients as well as taking away waste. If this waste is allowed to build up it can reduce the nutrients reaching the retina, stopping it working properly leading to vision loss.

Oral glycoside supplements have been shown to breakdown some of this waste material and allow it to be taken away by the blood in the blood vessels.

A difficulty in testing a treatment for early to intermediate AMD is that detailed vision (acuity) is not usually affected until later in the disease. The study will use additional vision tests, dark adaptation and imaging retinal densitometry and use images of the retina at the back of the eye (retinal photography, optical coherence tomography and scanning laser ophthalmoscopy). These will show the changes due to AMD.

60 participants with early or intermediate AMD in at least one eye will be recruited. Baseline health and vision information will be obtained at two initial visits. Participants will be randomly assigned by a computer programme into two equal groups (n=30), one receiving the oral glycoside tablets and the other placebo tablets, both to be taken daily for 4 months. Two follow up visits will be carried out at 4 months and two visits will be carried out at 12 months, where the tests performed at the baseline visits will be repeated. The data collected will be used to determine the potential effectiveness of the treatment, how well participants complied with taking the tablets and the overall feasibility of the trial design.

A secondary aim of the project is to evaluate a new retinal imaging device called an ‘imaging retinal densitometer’. By looking at how the reflectance of the retina changes over time after it is exposed to light, the device can measure the regeneration of the light sensitive visual  pigments that are found in rod and cone photoreceptors. The device may be a useful outcome measure to include in future oral glycoside studies because oral glucoside supplementation is believed to speed up visual pigment regenerates rates.