Related articles: Retinitis pigmentosa
Definition
Retinitis pigmentosa is a progressive degeneration of the retina and retinal pigment epithelium; the disease is bilateral (affects both eyes) and is caused by various genetic alterations.
The retina is the thin layer of light-sensitive tissue that internally covers the back of the eye. Its function is to acquire images from the visual field and to convert light signals into nerve stimuli, which are sent via the optic nerve to the brain. In the retina there are millions of photoreceptors (cones and rods), which contribute to determining the normal visual perception.
Retinitis pigmentosa involves the gradual loss of photoreceptors and dysfunction of the pigment epithelium (outermost layer of the retina).
Retinitis pigmentosa is an inherited disease; it is then transmitted by one or both parents to the children. The mode of transmission can be autosomal recessive, autosomal dominant or, rarely, heterosomal recessive (linked to the X chromosome). To date, more than 50 different genetic alterations implicated in the appearance of retinitis pigmentosa have been identified.
Most common symptoms and signs *
- Halo around the light
- Altered color vision
- Night Blindness
- Fotofobia
- Nyctalopia
- Narrowing of the visual field
- Reduced vision
- scotomas
- Blurred vision
Further indications
Patients with retinitis pigmentosa, initially, have vision problems especially in low light conditions; in particular, they have difficulty seeing at night (night blindness). In the early stages, the symptoms also include a reduction in the peripheral visual field (tunnel vision). The central vision is instead spared until the later stages of the disease.
Other early symptoms of retinitis pigmentosa may include slow adaptation from darkness to light, and vice versa, hyper-sensitivity to light and glare. Many patients report seeing bright flashes, often described as small flashing and shimmering lights. Moreover, it is possible to find the loss of color perception.
When vision loss involves the central area of the retina, patients experience difficulty with reading and detailed work, which requires concentration on a single object (eg, threading a thread in the eye of a needle). As the retinitis pigmentosa progresses, a thinning of the blood vessels that supply the retina occurs, which undergo atrophy.
The visual function decreases with the progressive involvement of the macula (central area of the retina in charge of the distinct vision and perception of details) and can evolve up to blindness.
The rate of progression of the disease and the degree of visual loss vary from person to person: some maintain a limited view for life, while others will completely lose their sight.
The diagnosis is based on the examination of the ocular fundus, which demonstrates the presence of characteristic retinal pigment deposits (hence the name of the disease). Patients with retinitis pigmentosa often develop retinal swelling (macular edema) or cataract at an early age. The electroretinogram is useful to confirm the diagnosis.
To date, there is no definitive cure and no treatment can repair the damage caused by retinitis pigmentosa. In some patients, vitamin A (eg in the form of retinyl palmitate) may be useful to slow the progression of the disease.
