Symptoms of Sight Loss
Eye Conditions & Care | Symptoms of Sight Loss
Night Blindness
The outer area of the retina is made up of more rods than cones. The rod cells enable us to see in poor illumination. This is the reason why loss of side (or peripheral) vision often results in night blindness. Individuals suffering from night blindness not only see poorly at night, but also require some time for their eyes to adjust from brightly lit areas to dim ones. Contrast vision may also be greatly reduced.
Glare Sensitivity
Problems with glare are associated with retinal degenerative diseases. Disappearing contours and contrast make it difficult to recognise surroundings. Light objects in the foreground and background can blend together to form a light, milky expanse. In extreme cases problems with glare can make it feel like walking into a white wall. Individuals suffering from glare problems can often find relief with filters for eyewear, side blinders and hats with wide brims that help shade the eyes.
Loss of Central Vision
This is when the light-sensitive nerve cells located in the macula, at the very centre of the retina, begin to degenerate with the progression of the disease. Our tiny macula (approximately 5% of the retinal area) allows us to see clearly and is essential to our vision. Individuals with Macular Degeneration have extreme difficulty reading and recognising faces. Shapes or contours of objects may seem distorted, yet enough peripheral vision is retained for good orientation and mobility. Macular Degeneration is one of the most common causes of low vision in the elderly population. It can however affect younger people in the form of Stargardt's, Best's Disease or Inverse RP.
Loss of Peripheral Vision
The photoreceptor cells cease to function from the outer edges of the retina. This causes a progressive loss of peripheral vision (side, upper and lower vision). It is as if the affected individual is viewing the world through a narrowing tunnel. However, the central vision of the person with RP may remain largely unaffected for a considerable number of years, enabling the individual to continue to read, watch television and perform other visually detailed tasks.
In some cases, small patches of retinal activity on the periphery are preserved, making it possible to detect movement and objects that assist with one's orientation.
With conditions such as RP there is no uniform age of onset of symptoms and no uniform rate and extent of vision loss. These can vary markedly from individual to individual and are not usually able to be predicted.