Retinitis Pigmentosa (RP) is a very rare condition that affects 1.5 million people worldwide. Some cases run in families and are genetically transmitted.
It occurs due to a dysfunction of the photoreceptor cells of the retina. There are 2 types of photoreceptor cells, rods and cones. The rods that deal with night vision are primarily affected in retinitis pigmentosa.
Poor night vision is a key symptom
In the early stages the only symptoms may be poor vision in a dark room or at night. One may find difficulty in simple tasks like finding your seat in a darkened theatre or cinema. As the disease progresses, you may bump into things easily and miss objects in the peripheral field of vision. These symptoms usually present in adolescence or early adulthood. The genetically transmitted retinitis pigmentosa may be associated with deafness and other neurological abnormalities.
Disease progression is slow
The disease progresses very slowly and in the late stages by the age of 60 vision may be severely affected and the patient may need training and rehabilitation to assist in their daily activities.
Tests to diagnose RP
The disease is confirmed by a test called the electroretinogram (ERG) that assesses the function of the rods and cones. This test may take approximately one and a half hours and requires specialised equipment. It is an important test as some cases may appear normal or have very subtle changes on the retinal examination. The other reason why this test is of importance is because nutritional substances may benefit the group where the rod cells are affected. Supplements with nutritional substances may cause further deterioration if it is the cone cells that are predominatly involved. The ERG will be able to tell whether the rod or cone is affected.
Treatment of RP
Researchers found that people with rod dysfunction in retinitis pigmentosa condition experienced a slowing of the disease process if they took vitamin A supplements and ate a diet high in omega-3 fatty acids. Experimental treatments involving stem cell treatment and gene therapy have shown promise in mouse models. However its role as a form of treatment in humans is still in the research stage. Some forms of RP (RPE65) have been treated with gene therapy in the UK and USA. Patients have to undergo vitreoretinal surgery and the gene vector is injected under the retina. The new gene will then correct the defective genes causing the specific type of RP and there has been slight improvement in vision found. Some researchers are also looking at “neuro-modulation” by using electrode stimulation of the retina.
If diagnosed in childhood, the individual may have to make choices in terms of careers and courses undertaken. We advise patients with RP not to undertake jobs that require good vision like pilots, surgeons, or , lorry drivers. There are many softwares and aids that are able to assist individuals with low vision to function and achieve great milestones in their careers. We always encourage patients to remain positive when informed of this diagnosis .