If someone tells you that they have a disorder of the eye called “retinitis pigmentosa”, you might be forgiven for thinking that it can’t be all that bad because there’s nothing obvious about it.
The person probably doesn’t have any signs of anything untoward in or around the eyes, and they seem to get around alright.
So what is it that is so serious that sight can be gradually lost, possibly leading to blindness?
What is “Retinitis Pigmentosa”?
Some understanding of how the eye works is necessary to have some appreciation of what goes so wrong that sight is affected.
Many people think that the retina at the back of the eye is a uniform flat layer that takes the signals from the eye lens and helps in transmitting an image to the brain – not so!
The retina of the eye is in fact made up of millions of very small rods and cones that are able to absorb light in differing but mutually beneficial ways:
• Rods – are VERY sensitive to light and only distinguish black and white, and outnumber the cones by 20 to 1
• Cones – there are around 5 million in an eye retina (compared to 100 million rods); they need direct light and can process colour, which is why colour is difficult to distinguish under dark conditions
They are very concentrated at the centre of retinal vision with hardly any rods present, whilst some are scattered over the remainder of the retina, but of course rods remain predominant there
When retinitis pigmentosa develops, the outer areas of mainly rods and much fewer cones degenerate and cease to function, to the extent that gradually peripheral vision is lost leaving only a “tunnel” of vision.
On occasion it is the central area that first degenerates, in which case central vision is lost and subsequently vision requires movement of the eyes from side to side to see effectively.
The term retinitis infers “inflammation” of the retina, but this is not really what happens; the term “pigmentosa” comes from the effect of the discolouration of the retina when seen in an eye examination by an optometrist.
How do people who suffer from retinitis pigmentosa manage?
The inherited disorder is progressive and there is no treatment or cure.
Sufferers need to constantly adapt to the vision loss. They can do this by using the areas of retina that continue to function and hold an image in line of sight.
A recent long term study that followed many patients with retinitis pigmentosa revealed that most of them maintained some sight.
What are the things that a person should be aware of if there is a family history?
• Slow degeneration of peripheral vision (and in some cases central vision).
• Difficulty in adjusting from different lighting situations – very dark and very light
• Colour differentiation becoming poor
• Glare becoming a problem
What can be done?
With 1 person in 3000 suffering from the disorder, there are national and state societies that can provide education and support.
Those who are involved in the societies have dropped the rather inadequate term “retinitis pigmentosa” and have instead adopted the colloquial RP instead.
Technology has gone a long way in not only improving the lifestyle of patients with retinitis pigmentosa but many other eye diseases which significant degrade vision. Computer software allows efficient interaction with the internet and most movies now are released with audio description which allows people from low vision to blindness to enjoy TV and movies.
What does the future hold?
This is extremely exciting. From genetic intervention to retinal electronic chips (termed the bionic eye) people with low vision have a lot to look forward to.