By Dr Ananya Mandal, MD
Retinitis pigmentosa is a group of related conditions associated with progressive degeneration of the light sensitive retina that lies at the back of the eye ball. This layer of photo sensitive cells with photoreceptors called rods and cones is normally associated with vision.
The rod photoreceptors normally provide black and white vision whole the cone photo receptors are associated with color vision. Rods are mostly affected but sometimes the genetic disorder affects the cones as well.
With the course of the disease there is degeneration of the retina and its capability to transmit images of meaningful vision reduces leading to complete loss of vision. Cells from the pigmented layer of the retina enter the layer containing nerve cells leading to typical pattern of black or brown star shape pigmentations in the retina that gives the diseases their name.
Symptoms of retinitis pigmentosa include:-
Symptoms of vision loss become apparent between the ages of ten and 30. Earlier onset is seen with more severe forms of the condition while those with milder conditions (e.g. those with autosomal dominant forms) may develop the condition in their fifth or sixth decades of life.
Loss of vision may be slow or rapid. Again those with a milder disease have a slow progression of the disorder compared to those with a more aggressive form of the disorder.
Often the first symptom is night blindness. This is termed nyctalopia. Some people notice that they take progressively longer to adapt to differences of light when they move from a well lit area into a darker area.
A typical form of vision loss narrowing of peripheral vision that leads to tunnel vision. This ring pattern of vision loss is called ring scotoma. This may be missed in initial stages but is noticed when the individual trips over objects and misses objects within the range of his or her vision. This defect may be identified after the individual has a road traffic accident at times or tries to take a test for a Driving licence.
In a type of retinitis pigmentosa loss of vision begins in the central area. This is called macular dystrophy. Patients notice that they have difficulty with reading and detailed work that requires focussing on a single object.
Many patients complain of seeing flashes of light, often described as small shimmering blinking lights.
In around 10 to 30 percent of all patients with retinitis pigmentosa there may be associated hearing loss. This is termed Usher syndrome.
In one type of Retinitis pigmentosa called Leber's amaurosis children may become blind, or almost so, within the first six months of life.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)
Last Updated: Jan 20, 2013