Retinitis Pigmentosa: Symptoms, Genetic Causes and Treatment

Retinitis pigmentosa (RP) is a group of inherited retinal dystrophies caused by mutations in over 100 different genes, leading to progressive degeneration of the rod and cone photoreceptors in the retina. It is the most common inherited retinal dystrophy, affecting approximately 25,000 people in the UK and 1.5–2 million people worldwide. The name reflects the characteristic pigment deposits visible in the retina on examination — though these are not the direct cause of vision loss.

Night blindness (nyctalopia) — difficulty seeing in dim light or adapting from bright to dark environments — is usually the first symptom, often beginning in childhood or adolescence. This is followed by gradual loss of peripheral (side) vision, creating characteristic 'tunnel vision' that narrows progressively over years to decades. Central vision, colour vision and visual acuity are usually preserved until later in the disease course, though they can be affected — particularly when associated macular degeneration or cataract develops. Photophobia (sensitivity to bright light) and glare are also common.

RP is caused by mutations in any of over 100 genes involved in photoreceptor function or retinal pigment epithelium biology. These mutations cause rod photoreceptors to degenerate progressively — losing their structure and function — followed by secondary cone degeneration as the interdependence of rod and cone cell health is lost. The underlying biological mechanisms vary by gene: some mutations cause defective phototransduction, some affect the visual cycle, some cause ciliary dysfunction (cilioapathies), and some cause protein trafficking defects in photoreceptors.

Yes. RP is always caused by an inherited gene mutation, though in approximately 30–40% of cases no family history is apparent (simplex RP — often autosomal recessive with unaffected carrier parents). The three main inheritance patterns are: autosomal dominant (adRP) — one mutated gene copy is sufficient to cause disease; autosomal recessive (arRP) — two mutated copies are required, usually from two carrier parents; and X-linked (xlRP) — the gene is on the X chromosome; affected males inherit it from carrier mothers and typically have more severe disease; carrier females may have mild or no symptoms.

RP is diagnosed by: full-field electroretinography (ERG) — a definitive test measuring the electrical response of the retina to light, which is markedly reduced or absent in RP; visual field testing (Goldmann or automated perimetry) documenting peripheral field loss; fundus examination showing bone spicule pigmentation, attenuated vessels and waxy disc pallor; and OCT showing outer retinal layer thinning and photoreceptor loss. Genetic testing (gene panel or whole exome sequencing) identifies the causative mutation and is now routine in specialist retinal dystrophy clinics.

Night blindness (nyctalopia) is the inability to see clearly in low-light or dark conditions, or to adapt quickly when moving from bright to dark environments. It occurs in RP because the rod photoreceptors — which are responsible for vision in dim light — are the first cells to degenerate. Night blindness is the earliest and most characteristic symptom of RP, often beginning in childhood or adolescence. It may manifest as difficulty driving at night, difficulty in dark restaurants or cinemas, or stumbling in dark environments. Night blindness can also be caused by vitamin A deficiency.

Tunnel vision (tubular vision) is a progressive constriction of the peripheral visual field, leaving only a narrow central 'tunnel' of vision, like looking through a tube. In RP, peripheral field loss begins as a ring scotoma (a ring-shaped area of visual loss) in the mid-periphery, which gradually expands inward over years to decades. The rate of progression varies widely. In some patients, visual field constriction progresses to less than 10 degrees (legally blind in the UK), while central visual acuity may remain relatively preserved.

Not always. RP progression is highly variable between individuals and between the different genetic subtypes. Some patients retain useful central vision throughout their lives; others progress to severe visual impairment or legal blindness (less than 3/60 or less than 10 degrees of visual field). The most severe form is typically X-linked RP (caused by RPGR mutations). All patients with RP are at risk of developing posterior subcapsular cataract and macular oedema — both treatable complications that, if not addressed, can accelerate vision loss beyond that caused by the RP itself.

There is currently no established cure for most forms of RP. Voretigene neparvovec (Luxturna) — the first approved gene therapy for an inherited retinal dystrophy — is NICE-approved for RPE65-associated Leber congenital amaurosis and early-onset severe retinal dystrophy (a small subset of RP). Vitamin A palmitate (15,000 IU/day) has shown a modest effect on slowing ERG decline in some RP patients in clinical trials, though this evidence is debated and requires specialist guidance. Treating associated complications (posterior subcapsular cataract, macular oedema with carbonic anhydrase inhibitors or anti-VEGF) can preserve useful vision.

Luxturna (voretigene neparvovec) is a gene therapy approved by NICE (and EMA) for RPE65-associated retinal dystrophy — caused by mutations in the RPE65 gene, which is responsible for a critical step in the visual cycle. Luxturna delivers a functional copy of the RPE65 gene directly into retinal pigment epithelium cells via a single subretinal injection of an adeno-associated viral (AAV) vector. It is the first approved ocular gene therapy in the UK and EU. In clinical trials, it significantly improved light sensitivity, visual field and navigational vision in patients with RPE65-associated disease.

Electroretinography (ERG) is an electrophysiological test that measures the electrical responses of the retina's photoreceptor cells (rods and cones) to light stimuli. An electrode (embedded in a soft contact lens or placed on the lower eyelid) records the retinal response to flashing lights of varying intensities and wavelengths. Full-field ERG evaluates both rod and cone function across the entire retina. In RP, ERG responses are characteristically reduced or extinguished — even before significant visual field loss is apparent — making it the gold-standard objective test for confirming the diagnosis.

Posterior subcapsular cataract (lens opacity at the back of the crystalline lens) occurs in approximately 50% of patients with RP and can significantly reduce visual acuity — it is treatable with cataract surgery, often with worthwhile visual improvement. Macular oedema (swelling of the central retina) occurs in approximately 30% of patients and can be treated with oral carbonic anhydrase inhibitors (acetazolamide) or topical dorzolamide. Usher syndrome — the combination of RP and sensorineural hearing loss — is the most common cause of combined deafness and blindness; Usher syndrome type II is the most common subtype.

Usher syndrome is the most common cause of combined vision and hearing loss in the UK, caused by mutations in genes (USH2A, MYO7A, CDH23 and others) that affect both the inner ear and retinal photoreceptors. It is autosomal recessive. There are three types: Usher type I (profound congenital deafness, absent vestibular function, RP from childhood); Usher type II (moderate-severe hearing loss, normal balance, RP in adolescence — the most common type, usually caused by USH2A mutations); and Usher type III (progressive hearing loss, variable RP). Gene therapy trials targeting USH2A and MYO7A are under way.

A clinical trial by Berson and colleagues (1993) found that adults with typical RP taking 15,000 IU/day of vitamin A palmitate had a slower rate of ERG amplitude decline than those on placebo — approximately 20% slower per year. However, the clinical significance of this ERG finding (whether it translates to slower visual field loss) has been debated. Some UK retinal specialists recommend it for adults with typical RP, with regular liver function monitoring. It should not be taken during pregnancy (teratogenic at high doses). Vitamin E supplements should be avoided alongside high-dose vitamin A as they may counteract the benefit.

People with RP can access a range of low vision aids and rehabilitation support: magnifiers (optical and digital) for reading; high-contrast materials; lighting optimisation (RP patients often benefit from increased lighting); dark glasses and brimmed hats to reduce glare and photophobia; screen magnification software; text-to-speech and audio description technology; cane or guide dog mobility support; and GPS navigation aids. NHS low vision clinics and the Royal National Institute of Blind People (RNIB) provide assessment and access to assistive technology. Retina UK provides peer support and information.

The key support organisations are: Retina UK (formerly British Retinitis Pigmentosa Society) — the UK's leading patient charity for RP and allied conditions, offering information, helpline, peer support groups, financial grants and research funding; RNIB (Royal National Institute of Blind People) — equipment, benefits advice, talking books, emotional support; NHS low vision services; Certificate of Visual Impairment (CVI) for those meeting sight impairment criteria, which unlocks benefits and social care; and Access to Work grants for people of working age with RP who require workplace adaptations.

In low-income countries, RP is frequently misdiagnosed or entirely undiagnosed because electroretinography and specialist retinal services are unavailable. Genetic testing — essential for accurate prognosis and family planning — is absent from most public health systems. Treatable complications such as posterior subcapsular cataract and macular oedema go unmanaged, accelerating vision loss unnecessarily. World Aid Network funds eye care through locally-licensed ophthalmologists, supporting access to ophthalmic services for the poorest communities in the regions where we operate.