Age related Macular Degeneration
The macula is responsible for our detail vision
The macula is located in the centre of the retina. The retina is located at the rear of the eye and acts as its ‘film screen’, containing the cells of vision. These cells are called rods and cones and the cone cells are mostly confined to the macula and are responsible for detail vision and colour perception in good lighting or sunlight. The macular area is only somewhat larger than one square millimetre.
The rods are found in the retina outside the macula, and are used in poor light conditions, giving rise to the saying ‘when candles be out all cats be grey’, since the rods have no colour perception.
The reaction to light stimulation of the retinal cells involves a highly complicated series of chemical and physical events. Nerve signals from these cells are sent via the optic nerve to the optic chiasm in the midbrain, and through the optic tracts to the visual centre of the cerebral cortex in the back of the brain. Here the images are formed and sent on to other parts of the brain for interpretation. It is at this point that we can understand what we see. To see well, all of the visual system needs to function properly. The most important parts is the retina and the macula.
With a functioning optic system the image in the eye is focused in the macula. Normal refractive errors can be corrected with glasses or contact lenses. Various diseases can lead to damages in the macula. The most frequent reason is Age related Macular Degeneration.
Age related Macular Degeneration is the most common cause of visual impairment in people over 60 throughout the western world. The older we get the more common it is. Around 10% of people between 65-74 and 30% between 75-84 experience changes in the macula due to age.
Two forms of Age related Macular Degeneration are diagnosed. The dry form is most common and affects around 85% of those suffering from macular degeneration, and the wet form is affecting 10 - 15 %.
Symptoms often appear suddenly
In the wet form, symptoms usually appear relatively suddenly. Straight lines appear wavy, the image is distorted, reading difficulty becomes pronounced and a shadowy spot might appear in the central visual field. It's important to see an eye care professional when experience these symptoms. The wet form of Macular Degeneration often leads to explicit visual impairment.
The changes in vision associated with the wet form are due to new blood vessels growing beneath the macula. These new vessels are fragile. They leak blood quite easily, and cause a swelling on the macular area which later results in a large scars and loss of many retinal cells.