Retina and macula
The retina is the light-sensitive tissue of the eye. It is a thin membrane covering most of the inner surface of the ocular globe. This neurosensitive tissue contains highly specialized cells called photoreceptors, which capture rays of light. The visual information is then transmitted to the nervous system.
The macula, still sometimes called the macula lutea, or “yellow spot”, is located in the centre of the retina. It contains the fovea centralis, the place where visual acuity is highest.
Macular degeneration involves gradual loss of central vision, which becomes increasingly blurry. Also, objects are perceived with distortions: straight lines are curved.
This disease mainly affects people after the age of 55. It is then called age-related macular degeneration, or ARMD.
Two types of ARMD exist, “wet” and “dry”. Dry, or atrophic ARMD, is the least serious and more common form. It develops gradually, over several years. All age-related macular degeneration starts with the dry form. 10 to 15% of patients then develop the wet form. Wet ARMD, also called exudative or neovascular ARMD, is an aggravation of the dry form. It is characterized by the formation of new blood vessels in the capillary lamina of the choroid, beneath the retina. The accumulation of fluid leads to more rapid vision loss than the dry form. The wet form can lead to a complete loss of central vision.
No one is entirely safe from age-related macular degeneration, but it has been shown that certain factors increase the risk. Some of them are controllable, and others are not. The uncontrollable risk factors are age, a family history of the disease, and white skin. Conversely, lifestyle also plays an important role. Smoking has been identified as one of the major risk factors. Adopting a healthy diet rich in omega-3 oils (nuts, cold-water fish, and linseed and colza oils), as well as exercising regularly and keeping your weight down, reduce the risk. It is also important to monitor your blood pressure and protect your eyes from the sun’s ultraviolet rays.
To date, there is no cure for dry ARMD.
There is some controversy as to whether the AREDS vitamin supplements, high in zinc and anti-oxidants and marketed by a vision company, can attenuate the risk of vision loss.
Treatment of wet ARMD is currently based on medication that inhibits the growth of new blood cells. The brand names of the most commonly used “anti-VEGF” drugs are Lucentis® (ranibizumab) and Eylea® (aflibercept). These drugs make it possible to stabilize eyesight and even improve visual acuity. When the drugs are administered directly in the eye, they are more effective, locally, and undesirable systemic side effects are avoided. This intravitreal injection is an outpatient procedure, performed by the ophthalmologist after the eye is numbed with drops. It only takes seconds. The medication is injected through the sclera (the white of the eye) with an extremely thin needle. The injection is harmless to nearby ocular structures.
However, although the injections can stabilize the disease or even make it regress, they do not constitute a definitive cure. As a result, they must be administered repeatedly.
A detached retina is a potentially dangerous condition. Usually individuals are affected in mid-life or later; near-sighted people (myopics) are more subject to the condition. In most cases, retinal detachment is caused by a break in the membrane, but it may also occur after an injury to the eye, or due to a rarer cause. If it is not treated rapidly, retinal detachment can lead to reduced eyesight or even blindness.
The sudden appearance of dark spots moving through the field of vision (“floaters” that look like flies), flashes of light that are not caused by an outer source, or a dark shadow on the edge of the field of vision can all herald a detachment of the retina. Lower visual acuity is a later sign. Retinal detachment cannot be detected with the naked eye, and the patient’s eye is not red or painful.
If you experience one of the above symptoms, you should see an ophthalmologist as soon as possible.
If the retina is torn, but still attached, a quick laser treatment can prevent detachment. This treatment is an outpatient procedure done under topical local anaesthesia with eye drops.
However, if the retina is detached, a surgical procedure is necessary.