Retinitis pigmentosa

It is the most common cause of hereditary degeneration of the retina. It is estimated that 25,000 people are affected by it in Spain. Numerous genes may cause it (12 have been identified), 50% of which are hereditary (dominant autosomal, recessive autosomal and linked to the X chromosone). 

However, there are environmental factors that can either stop or, on the other hand, contribute to its development. Over recent decades, particular progress has been made in the understanding of the diverse factors that play a role in its development, but there is still a lot of ground left to cover. 

Its origin causes degeneration and apoptosis (cellular death) of the photoreceptors (retina cells), the rods (responsible for peripheral field vision) and in the final stages, of the cones (central vision) causing blindness. 

Retinitis pigmentosa has a silent and slow onset, so much so that patients normally do not visit the ophthalmologist until 15 years after their night blindness starts. The age of onset is very varied, developing preemptively between the age of 25 to 40. There are cases in people under 20 and, less frequently, cases where the patient does not start to show symptoms until they are well into their 50s. 

The first sympoms that should alarm us are night blindness or, similarly, a slowness to adapt to the dark, the progressive loss of the visual field, which ends in tunnel vision. In addition, there may be colour vision issues and a loss of central vision, which does not affect everyone equally, even in the same family, there being elderly people who have normal visual acuity for their age. 

The prognosis for retinitis pigmentosa depends on the form of inheritance and the age of onset. The later the disease appears, the better.

Neuroprotective therapies, treatments with stem cells or gene therapy represent a significant future for the treatment of this pathology, although its current therapeutic options are limited. 

Second Sight (USA) developed an electronic retinal prothesis system providing artificial vision in 2007 using the ARGUS I and in 2009 the ARGUS II. Their results earned approval from the FDA (Food and Drug Administration) in the USA in February 2013 for it to be used on patients with retinitis pigmentaria. It was implanted in Spain for the first time at the Barraquer Ophthalmology Centre by Dr. Jeroni Nadal.  

The ARGUS system is based on placing an intraocular implant that acts as an electronic epirretinal stimulus, that is to say, it is put on the surface of retina. The systeme uses glasses to hold a High Definition camera which is placed on the end of the nose. This camera captures images that will be processed and they reach the brain's ocicptal cortex via a stimulation system.  

The large majority of patients regain their perception of shapes, objects and the movement around them, which means they can regain a certain degree of interrelation with themselves and independent movement.

The characterisation of the mutation of the genes already involved in retinitis pigmentosa and, therefore, the aetiological diagnosis based on DNA analysis, is currently a very expensive and laborious task.

It is hoped that in the very near future we will be able to localise the altered genes in all families in order to select embryos that do not suffer or transmit the disease or generate an effective therapy for each type of route affected. Another option being studied is transplanting stem cells in the retina.