Dr Moïse Tourabaly · Key points
The retina has two kinds of light-sensitive cells: the rods, in the periphery, for vision in low light and to the sides; the cones, in the centre, for fine vision and colours. In retinitis pigmentosa, the rods degenerate first, the cones later. This order explains all the symptoms.
The retina, front view
What the patient perceives
The rods, numerous in the periphery, take over when light fades; the cones, concentrated in the centre (the macula), provide the vision of detail and colour.
Rods first. First sign, almost always: difficulty seeing in the dark, put down to tiredness or age. Then the visual field narrows concentrically, with no black spot perceived: the brain fills in, and you bump into things. All this time, distance acuity can remain excellent, the macula being spared.
Cones later. Later, central vision and colours decline in turn. The speed depends on the gene involved and varies from one person to another, even within the same family: no age can be predicted.
“Retinitis pigmentosa” refers to a group of genetic diseases, not a single one. No treatment stops the degeneration today, but two common complications can be treated and often restore useful vision: macular oedema and cataract. Hence the value of regular follow-up.
Educational diagram · Dr Moïse Tourabaly, ophthalmologist. It does not replace a consultation.