Actually, retinitis pigmentosa (also called TRD = Tapeto Retinal Dystrophy) is not one single disease, but a collective name for a group of diseases characterised by poor eyesight in the dark (night-blindness) and a very gradually narrowing down of the field of vision, which will eventually lead to tunnel vision. The seriousness and the development may widely vary per person. The first symptoms can show already during childhood, but sometimes the disease is diagnosed only in middle life.
In case of retinitis pigmentosa (RP) the photoreceptors (the rods and the cones) in the retina are affected. The eye disease starts with the dying of the rods, mainly located in the outer edge of the retina. Dropping out of the rods leads to night-blindness (nyctalopia) and narrowing down of the field of vision (tunnel vision). At a later stage, the cones may be affected as well, as a result of which the sharpness of vision and the vision of colours and contrast are reduced.
Actually, the name retinitis pigmentosa is incorrect, as the ending -itis would suggest the presence of an infection, which is not the case. In case of the type of retinitis pigmentosa that goes together with Usher Syndrome there probably is a problem in the metabolism of the pigment cells. The rods cannot get rid of their waste products and as a result they perish in their own waste. The pigment epithelium will spread to the part of the retina containing the rods and cones.
- that you only can see at night with light;
- that when entering a dark room, your eyes will only slowly adapt to the weak light;
- that you need the proper light intensity for reading;
- that your eyes have trouble to adapt to the changing light intensity when going from light to dark (and from sun to shadow). This also applies to going from a dark to a light room;
- that you want to go to the light like a moth, but that you cannot see the obstacles that are in your way;
The field of vision slowly decreases to tunnel vision. It is like looking at the world through a straw that is gradually narrowing down. Everything that is outside this tunnel disappears and this is not black, white or unclear. It is just not there, just like a person who can see well does not see anything that is outside the field of vision. Limited field of vision (or tunnel vision) means:
- that you can only see a part of your surroundings;
- that you can compose a total picture by turning your head and moving your eyes;
- that you sometimes have to stand at a distance to get an overall picture;
- that you read slowly, because you can only see a few letters at a time;
- that you do not see an outstretched hand or a glass that is standing on the table;
- that you trip over obstacles that are outside your tunnel of vision;
- that you can ‘easily’ see a ladybird, but run into a big oak tree;
- that you do not have an overview of the space around you;
- that you sometimes have trouble recognising people;
- that you can only see contours when there is much light;
- that you very often wear sunglasses or a cap/hat;
- that you cannot or with difficulty read texts on glossy paper or with little contrast;
- that you prefer to sit with your back to the window because of the unpleasant backlight.