The eye functions similar to a camera. The shutter on the eye i.e. the iris opens and closes in response to light and lets it in accordingly. This eye is then projected onto the film or the retina. The retina creates the image and sends it to the brain. Regardless of the functionality of other elements of the camera, the result of the final picture is going to be faulty if the film is sub-par. Similarly if the retina fails to create an image, the brain will have difficulty in deciphering the image resulting in vision loss or other problems such as blurriness or distortion.
The light sensitive tissue of the retina contains photoreceptive cells and neurons which are connected to the neural network. The photoreceptor cells contain rods and cones. The rods are responsible for facilitating vision in areas with low illumination. The cones on the other hand help the eye recognize colors. These are mainly located in the center of the retina and known as the macula.
Retinitis Pigmentosa (RP):
RP refers to a group of diseases which are primarily hereditary. They affect the retina and occur as a result of the destruction of the rods and cones. The degeneration of the rods occurs first which often lead to loss of night vision and ultimately blindness. Tunnel vision is one of the symptoms of retinal degeneration, Tunnel vision occurs when the viewer has limited vision causing them to view only a limited area usually central to the eye. There is currently no cure for Retinitis Pigmentosa. Diagnosis of these diseases is usually done earlier in childhood or sometimes when its progression is at a lower rate, in adulthood. The rate of progression of the disease varies with each individual.
Macular degeneration is the breakdown of cells present in the macula. This usually results in the loss of central vision. The most common form of macular degeneration is that of AMD (Age-related Macular Degeneration). AMD usually affects those aged above 60. It may either be dry or wet. Dry AMD is the most common form of macular degeneration occurring in more than 90% of the cases. In dry AMD, drusen which are yellow white deposits accumulate within the retinal tissue underneath the macula. Wet AMD on the other hand occurs when abnormal blood vessels grow underneath the macula. The vessels leak fluids and blood in the macula which causes gradual destruction of the photoreceptive cells. In case of wet macular degeneration, early diagnosis is the key factor in its treatment. If caught in time, laser eye surgery may halt its progression or slow it down.
The Usher Syndrome
The Usher syndrome is another form of retinal degeneration which is less common than the above two. It is a hereditary condition which causes loss of hearing as well as vision. It often leads to problems in balance. Sufferers of the Usher syndrome may experience loss of central vision, tunnel vision and night blindness. There is no treatment or complete cure for the Usher disease. Early diagnosis however is important in order to reduce the trauma associated with the loss of vision and hearing. It can help the patient adapt to this drastic change and handle the situation better.