It is a slowly progressive disease and the earliest signs may be overlooked. As stated above, these diseases are known to be passed from parents to offspring even though the parents may have normal eyes. Therefore, identification of breeding animals with PRD is essential to prevent spread of this condition. To better understand PRD, a basic understanding of the function of the retina is needed. The retina is a highly complicated tissue located in the back of the eye.
Light strikes the retina and starts a series of chemical reactions that causes a nerve impulse.
The impulse passes through the layers of the retina to the optic nerve and from there to the brain where vision takes place. In the retina, cells called rods are involved with black and white or night vision and cells called cones are involved with color or day vision. Progressive retinal degeneration may effect either the rods alone, the cones alone or both the rods and cones together. Progressive retinal degeneration is not a painful condition so your pet will not have a reddened eye or have increased blinking or squinting. For this reason most clients will not notice the early stages of the condition.