Age-related macular degeneration (AMD)
Age-related macular degeneration (AMD) is a painless eye condition that leads to the gradual loss of central vision and is the most common cause of sight loss in the developed world and the third most common globally. Around 600,000 people in the UK currently have sight loss caused by AMD and around 70,000 new cases are diagnosed every year. Macular degeneration develops when the macula (the part of the eye responsible for central vision) is unable to function as effectively as it used to. Vision becomes increasing blurred and reading and recognising faces becomes more difficult. Colours appear less vibrant. Old age, smoking and a family history of AMD are known to increase the risk of developing the condition.
Dry-form: This develops when the cells of the macula become damaged due to lack of nutrients and there is a build-up of waste products from the biochemical processes responsible for vision called drusen. It is the most common and least serious type of AMD accounting for around 9 out of 10 cases. The loss of vision is gradual, occurring over many years. However, an estimated 1 in 10 people with dry AMD will then go on to develop wet AMD. There is currently no effective treatment available for patients with the dry-form AMD. Loss of retinal cells in and around the macular region is sometimes referred to as geographic atrophy.
Geographic atrophy: This is a chronic progressive condition that tends to occur in the late stage of age-related macular degeneration (AMD). It is characterized by the progressive loss of retinal pigment epithelium (RPE). The RPE is a layer of cells between the retina’s photoreceptor cells and the layer of blood vessels underneath that nourishes the retina. The pigmented retinal cells die, resulting in patches that look different from the rest, hence the name of the condition. Geographic atrophy can affect one or both eyes, and a patient with geographic atrophy in one eye is more likely to develop it in the other. It leads to irreversible vision loss and affects a person’s visual acuity.
Wet-form, or neovascular, AMD develops when abnormal blood vessels form underneath the macula and damage its cells. Vision can deteriorate more rapidly in people with the wet-form of AMD, sometimes, within days. Wet-form AMD is treated with eye injections which neutralise VEGF and is effective in many patients over a few years, after which, they often become unresponsive to further treatment.
Diabetic macular edema (DME)
Diabetic macular edema (DME) is the most common cause of sight loss in diabetics. The longer you have diabetes, the greater your chance of developing sight loss. About 90% of people with type 1 diabetes will have some degree of retinopathy after 10 years. For people with type 2 diabetes, the chance of developing retinopathy after 10 years is between 67% and 80%. DME is caused by blood vessels in the eye becoming leaky and allowing fluid to build up in the macula, at the centre area of the retina. It is a complication of diabetic retinopathy.
Current treatment relies on regular eye injections of proteins which neutralise vascular endothelial-derived factor or VEGF, a protein which is partially responsible for the leaky blood vessels. However, less than half of DME patients respond adequately to the injections. Therefore new more efficacious agents are urgently needed for this eye disease.
Ocular hypertension, is defined as having a raised eye pressure greater than 21 mmHg. Ocular hypertension is a proven major risk factor for developing glaucoma and eye drops are recommended to lower the pressure.
However, many patients find it difficult to apply the eye drops on a regular basis and there is a resultant rebound in eye pressure.