Imagine hollowing out a toothpick and looking through it. Pretty tiny hole you’re looking out of, right? Now imagine that little tiny bit of vision you do have, is blurry. That’s pretty much what I see. The tunnel vision is caused by Retinitis Pigmentosa and the blurry vision is caused by cataracts.
Retinitis = Disease of the retina
Pigmentosa = Pigments
There are many different diseases under the umbrella of Retinitis Pigmentosa, which causes retinal degeneration. On the back inside wall of the eye is the retina. It has a lot of photoreceptor cells called rods and cones that slowly die off in a person who has this disease. In most forms of RP, including mine, the rods start to die first. The rods are concentrated on the outer portion of the retina and are triggered by dim light. That is why individuals with RP lose their peripheral vision and night vision first usually. The cones later become involved and that is when individuals start losing their central vision. Color perception is also lost when these cones start to die.
“They” say that individuals become legally blind by/around age 40. In most of these cases, legally blind is defined as a peripheral field of vision of 20 degrees or less, whereas normal is around 180 degrees. However, I’ve talked to many people with RP and most are legally blind way before then. The rate of progression of course varies from person to person.
RP is genetic and there are many different genetic forms of RP: autosomal recessive RP, autosomal dominant RP, and X-linked RP. In autosomal recessive RP, both parents carry one of the mutilated genes responsible for RP, but do not have any symptoms themselves. Children have a 25% probability of inheriting RP. In autosomal dominant RP, only one parent is usually affected and is the only parent with the mutilated gene. A child has a 50% chance of inheriting RP in this case. Finally, there is X-linked RP where the mother carries the gene and her sons have a 50% chance of inheriting it but daughters don’t usually inherit it. Daughters are carriers and if they do inherit it, they likely have milder symptoms.
Currently there are no cures for RP. However, genetic testing is available for RP if one is interested in seeing if their children will likely have RP.