Retinitis Pigmentosa: Signs, Causes and New Treatments

Retinitis pigmentosa, also known as rod-cone dystrophy, is a rare eye disease affecting approximately 1 in 4,000 people in the United States. The condition damages the retina, which is the light-sensitive membrane at the back of the eye. Rods (cells which detect dim light) and cones (cells which detect light and colour) in the retina slowly degenerate, resulting in loss of vision. Retinitis pigmentosa may eventually cause complete blindness, but this is uncommon.

Signs of Retinitis Pigmentosa

Signs of retinitis pigmentosa are usually first seen in childhood, adolescence and young adulthood and may be observed in children as young as ten. Retinitis pigmentosa symptoms progress over time, but serious visual difficulties do not usually appear until early adulthood. It is difficult to determine how great a person’s vision loss will be or how quickly his or her vision loss will progress.

Signs of retinitis pigmentosa include:

  • difficulty adjusting to dim light and poor night vision due to deterioration of rod cells in the retina. It may be necessary to avoid driving at night
  • problems with colour perception caused by damage to cone cells
  • loss of peripheral vision
  • narrowed central vision, known as “tunnel vision
  • loss of central vision in advanced cases of retinitis pigmentosa

Causes of Retinitis Pigmentosa

Retinitis pigmentosa is not caused by injury or infection – it is an inherited condition caused by gene mutations which lead to the degeneration of the retina. Retinitis pigmentosa is most often caused by a recessive gene, in which case the affected person inherits the defective gene from both parents. Recessive genes for retinitis pigmentosa can be passed to family members for many generations before somebody shows signs of the condition.

Genes associated with retinitis pigmentosa can also be dominant – only one parent has to pass the faulty gene to a child in order for the child to develop the condition. In some cases a new gene mutation causes retinitis pigmentosa in a person who has no family history of the disease. Retinitis pigmentosa can also occur in the presence of other conditions such as Bassen-Kornzweig disease (the inability to absorb dietary fats) or Kearns-Sayre syndrome (a neuromuscular disorder).

New Treatments for Retinitis Pigmentosa

There is currently no widely-accepted, safe, effective treatment for retinitis pigmentosa, although several new treatments have been suggested or are under investigation in clinical trials. These include:

  • sunglasses: wearing sunglasses may protect the retina from ultraviolet light, slowing the progression of retinitis pigmentosa and maintaining vision
  • vitamin A: high doses of vitamin A may slow the progression of retinitis pigmentosa, but evidence is weak. High doses of vitamin A can be toxic and may cause liver damage
  • retinal implants: a man-made prosthesis replaces a damaged retina and electrically stimulates the remaining healthy retinal cells
  • transplants: healthy retinal cells are transplanted into unhealthy retinas
  • gene therapy: healthy genes are inserted into the retina

There has so far been little help available for people affected by retinitis pigmentosa. However, current investigations offer hope of new treatments and partial sight restoration for people in the future. It is important to see an eye specialist regularly to detect vision changes and monitor eye health.

Sources

  • All About Vision. “Retinitis Pigmentosa” (Accessed 28th February 2011).
  • MedlinePlus. “Retinitis Pigmentosa” (Accessed 28th February 2011).
  • National Human Genome Research Institute. “Learning About Retinitis Pigmentosa” (Accessed 28th February 2011).
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