Age related macular degeneration (AMD) is a very common cause of vision loss in older Australians.
The macula is the area of the retina that serves the central, detailed part of our vision. It can be thought of as the most ‘high fidelity’ part of the retina – the area that we use for reading, recognising faces and perceiving fine detail.
Macular degeneration therefore results in loss or degradation of the central part of our vision. Common symptoms include distortion of shapes, areas missing when looking at text or objects, or general blurr affecting the centre of our vision.
In general terms, AMD may be divided into dry and wet types, although there is often overlap.
Dry AMD tends to be slowly progressive, but there may be few if any symptoms in its early stages. The diagnosis of dry AMD requires a careful examination of the macula and cross sectional scans using the latest Optical Coherence Tomography (OCT) technology. These scans may demonstrate the deposition of material under the retina as well as examining the outer layers of the retina which may be affected in dry AMD. The later stages of dry AMD may involve macular atrophy – where the supportive pigment layer under the neural retina is lost. The photoreceptors in the outer retina cannot function without this pigment layer. Macular atrophy may result in quite severe loss of central vision. There is currently no available treatment to prevent the progression of dry AMD, although a number of clinical trials are ongoing.
Certain patients may benefit modestly from taking specially formulated supplements containing a number of vitamins, minerals and plant derived substances. Ask your surgeon whether you may benefit from this treatment.
Wet (neovascular) AMD is typically a more sudden onset and rapidly progressive disease. Wet AMD results from an abnormality of the vascular layer under the retina. An abnormal frond of vessels growing into the layers under the retina is the most common lesion. This typically results in bleeding and vascular leakage (hence the term Wet AMD) that causes swelling of the macula and accumulation of fluid and other material underneath and within the retina.
Without treatment, this vascular leakage may quickly result in the formation of scar tissue which may cause permanent loss of the central vision.
Thankfully, most cases of wet AMD are treatable thanks to the advent of medications targeting the underlying chemicals within the body that drive neovascularisation. Vascular Endothelial Growth Factor (VEGF) is the most important of these chemical messengers. It drives the growth of new blood vessels in many parts of the body and has been found to exist at elevated levels in eyes with wet AMD. By blocking forms of this chemical, the abnormal vessels causing wet AMD may become inactive or regress. In most cases this results in resolution of the swelling and bleeding that cause vision loss.
This class of drugs are delivered via injections into the eye itself. Most patients find this thought alarming in the first instance, but our surgeons use techniques that make the procedure quick, precise and painless. Patients quickly become used to this treatment and find that their anxiety disappears.
Provided that the diagnosis is made in a timely manner, this treatment works very well to stabilise the vision and has a good chance of improving the vision over time.
It is important to understand that this treatment controls wet AMD rather than curing it. This means that the treatment is ongoing. Patients will undergo an induction phase of treatment with several injections separated by four weeks, before slow extension of this interval. The regular interval is individualised depending upon each patient’s response to treatment. It may vary from four weeks to twelve weeks, and occasionally longer.
