Medical retina treatment and care
The retina is the light sensitive tissue at the back of the eye. The centre of the retina is called the macula. The macula has the highest density of light sensitive cells (photoreceptors), and these provide the information we need to see fine detail and read small print.
A visual acuity test – reading down eye chart – is the standard test for central vision and will be reduced if there is significant disease affecting the macula. Visual acuity is also reduced if there is a refractive error such as myopia or longsightedness, but will be normal if the correct glasses are worn. Cataract can also reduce visual acuity as it prevents light from reaching the back of the eye.
Distortion of vision, where straight lines appear bent, is an important symptom of macular disease. This can be tested with an Amsler grid, shown here:
Amsler Grid: A as seen with a healthy eye and B how it can appear if there is macular degeneration
Retinal conditions can be detected by examination and photography of the back of the eye. The structures and layers of the retina can be imaged with Optical Coherence Tomography (OCT) This is an essential investigation for the diagnosis and management of many retinal diseases.
Common retinal conditions
Age-related macular degeneration. Age-related Macular Degeneration (AMD) is an eye disorder in which the central retina, the macula, becomes damaged leading to reduction in central vision. AMD is the most common cause of serious loss of vision in Europe and the USA. It affects the central (detailed) vision, but normally leaves the outer (peripheral) vision unaffected. Age is the most important risk factor for AMD but other risk factors include family history, smoking, long sightedness, and light skin or eye colour.
AMD is classified into two types:
- DRY which is much more common and is present in over 50% of those aged 75 years and over, mostly in very mild degree. It causes gradual deterioration of visual acuity.
- WET which occurs in 10-15% of cases, but is associated with more rapid and more marked visual loss. There is rapid onset of distortion of straight lines (like a kink), and/or blurring of vision.
On the right an eye with a healthy macula, on the left an eye with dry AMD
OCT of a healthy macula on the right and on the left a macula with wet and dry AMD
There is some evidence that a varied diet that includes vegetables, fatty fish and eggs can slow the progression of AMD, and nutritional supplements may also be beneficial. The UK Macular Disease Society is an excellent source of information and you can download a leaflet about nutrition and eye health from here. Low vision assessment and advice on magnifiers and lighting can be extremely helpful in maintaining reading and close work for patients with AMD.
The treatment of wet AMD has been revolutionised by the advent of two new drugs: Avastin and Lucentis. These two drugs are very similar. They are both given by injection into the eye, usually as an initial course of three one-monthly injections, followed by top-up injections later if necessary. Studies comparing these two drugs have consistently shown them to be equally effective, and recent studies have shown that they are both very safe. Newer drugs are being developed to treat wet AMD, and the latest, Eylea (aflibercept) is now available at the Midland Eye. This is as effective as Lucentis, but is longer-acting and therefore requires fewer injections. These treatments are available at Midlands Eye Care.
The treatment is a day-case procedure whereby a fine needle is injected into the eye as you are lying down on a medical coach. Local anaesthetic drops are applied to numb your eye and minimise discomfort. You can expect minimal discomfort and the treatment to be complete within 5 to 10 minutes. As with any medical procedure, there is a small risk of complications following the treatment. Most complications that might occur are from the injection itself, rather than the drug. For most patients, the benefit of the treatment outweighs the small risk of injection injury.
Diabetic eye disease. Diabetic retinopathy is a complication of diabetes that causes damage to the blood vessels in the retina.Fluid can accumulate at the macula (macula oedema) and reduce central vision. New vessels can grow on the retina (proliferative retinopathy) causing severe loss of vision. Diabetic eye disease can ge treated with retinal laser and injections into the eye.
Retinal detachment. Sometimes holes or tears form in the retina, often because of pulling on the retina by the vitreous (the jelly of the eye). Once a hole or tear has formed, fluid from the vitreous can seep behind the retina, and the retina then gradually separates from the eye wall. As this happens there is a corresponding loss of vision, and if it goes untreated many patients lose most or all their sight. Patients with retinal detachment require prompt surgery to prevent further visual loss, and to regain part or all of their lost vision