Retinitis Pigmentosa
 

Retinitis pigmentosa showing the typical bone spicules pigmentary changes.

There are multiple bone-spicules hyperpigmentation in the peripheral retina. In advanced cases,  the posterior pole is also involved. The retinal vessels are attenuated and the optic disc is pale.  The macula may show cellophane, atrophic or cystoid maculopathy. The condition is bilateral. Other features to look for: drusen in the optic disc cells in the vitreous cataract typically posterior subcapsular cataract keratoconus  trabeculectomy (3% of  RP develop glaucoma) Look for associated features which may provide clue to diagnosis: hearing aids (Usher's syndrome but beware that patients with syphilis or congenital rubella  may also have deafness and pigmentary changes in the retina)

Questions:

1. Which conditions may simulate retinitis pigmentosa?

AnswerInfections: syphilis, congenital rubella, resolving herpes retinitis, treated cytomegalovirus retinitis

Drug toxicities such as mellaril, chloroquine and chlopromazine

Resolved exudative retinal detachment such as seen in malignant hypertension

Blunt trauma

 

2. Is retinitis pigmentosa treatable?

Answer
Progression of retinitis pigmentosa can be slowed in some cases when the associated condition is treated. This include Refsum's disease and abetalipoproteinaemia.
Although the retinal changes cannot be reversed, the development of associated ocular conditions such as glaucoma, keratoconus, cataract and maculopathy should be recognized and treated to reduce their impact on the already poor vision.
 

3. Which forms of retinitis pigmentosa have the worse visual prognosis?

Answer
There are may systemic conditions which can be associated with retinitis pigmentosa but the majority of retinitis pigmentosa has no associated systemic conditions.
The inheritance can be autosomal dominant, recessive and X-linked. Of these, recessive and X-linked have the worse visual prognosis ( about 50% of them have vision of 6/60 or worse by the age of 50)

4. What is the feature of ERG in retinitis pigmentosa?

Answer
The amplitude of ERG is reduced early in the course of the disease. This abnormality usually precede retinal changes. As the disease progresses, the ERG diminished until it is extinguished in severe cases without detectable rod or cone responses to white light.
 

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