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Table of Contents
Retinitis pigmentosa (RP) encompasses a clinically and genetically diverse group of inherited retinal disorders that cause retinal degeneration. RP is the most common hereditary retinal dystrophy which causes progressive vision loss. In the UK, the prevalence of RP is approximately 1 in 4,000.1
Causes and Risk Factors
RP is caused by mutations in genes encoding proteins important for photoreceptor and retinal pigment epithelium (RPE) function and survival. Most cases result from mutations of the rhodopsin gene.
Genetic predisposition is the principal risk factor for RP. It may be sporadic or inherited in an autosomal dominant, autosomal recessive or X-linked pattern (Table 1).2 The prognosis is related to the mode of inheritance.
While RP is a disease usually limited to the eye, it can be associated with rare systemic syndromes (syndromic RP) with the most common being Usher syndrome (US) and Bardet-Biedl syndrome (BBS). US is the most common inherited cause of combined deafness and blindness while BBS is characterised by rod-cone dystrophy, obesity, polydactyly, learning disabilities and hypogonadism.
Table 1. Estimated percentage and prognosis of RP types.2
Type of RP
Dependent on the type of underlying syndrome
History and Examination
RP typically presents as complaints of visual disturbances, beginning in childhood or in the early teenage years. However, patients may present in their 40s as this is usually when severe visual impairment occurs. Either way, patients are first assessed by primary care physicians who then make an ophthalmology referral.
Patient with suspected RP will primarily complain about not being able to see well in low-light environments or will have difficulty adapting when moving from a well-lit area to a dark area. Patients tend not to notice they have reduced peripheral vision unless the symptoms have been occurring over a prolonged period of time.
History of Presenting Complaint
Be sure to ask about the age of onset to differentiate between genetic causes of RP. If the patient is young, a collateral history might be the main source of information (i.e. parents).
Most common symptoms:
Reduced peripheral vision or “tunnel vision”
Nyctalopia (night blindness)
Impaired dark adaptation
Less common symptoms:
Photopsia (flashing lights)
Reduced central vision
*Rod photoreceptors are affected earlier and more severely than cone photoreceptors in most forms of RP, thus giving rise to the above symptoms.
Past Medical History
Exposure to infectious diseases such as syphilis, rubella and diffuse unilateral subacute neuroretinitis, as they can mimic the symptoms of RP.
Previous ocular injuries
Medications and Allergies
It is important to ask about chloroquine and thioridazine hydrochloride as they can cause ocular signs similar to RP.
It is critical to determine the type of inheritance pattern by drawing a genetic pedigree for the patient’s family, as genetic inheritance is related to the prognosis of RP.
History of smoking
Illicit drug use
Effect on driving
Effect on occupation
It is important to do a systems review to identify syndromic RP. Topics to ask about include hearing, weight, sexual history and learning disabilities.
A thorough eye and fundoscopy examination should be performed in patients with suspected retinitis pigmentosa. Please see the Geeky Medics guide here for a description of the exam.
Most common findings:
Typically symmetrical bilateral presentation
Classic triad (Figure 1):
Bone-spicule retinal pigmentation
‘Waxy’ optic disc pallor
Retinal pigment epithelium (RPE) atrophy
Less common findings:
Cataract (posterior subcapsular subtype)
Optic disc drusen
Cystoid macular oedema (CMO)
The clinical presentation of RP is similar to several other conditions that cause pigmentary retinopathy.
Leber congenital amaurosis
Diffuse unilateral subacute neuroretinitis
Snellen chart (assesses visual acuity) – normal or may have myopia
Confrontational visual field (screens for visual field defect) – reduced peripheral vision
Electroretinogram (abnormal result is essential for diagnosis) – reduction in ‘a’ and ‘b’ wave amplitudes and implicit time may be prolonged in early disease. Patients with advanced disease may have a non-detectable ERG.
Perimetry (formally assesses any visual field defect) – characteristic ring scotoma in the mid-periphery of the visual field
Genetic testing – rhodopsin gene mutation, or other mutations
Optical coherence tomography – may detect CMO
Conservative management involves supportive measures to optimise vision:
Low vision aid (e.g. glasses, magnifiers)
Sunglasses (limits UV exposure)
An annual follow-up to detect treatable vision-threatening complications and provide support.
Medical management involves treating RP associated complications:
Carbonic anhydrase inhibitors for CMO.4
Topical dorzolamide or brinzolamide initially.
Oral acetazolamide if no improvement.
Surgical management involves treating RP associated complications:
Complications of RP include:
RP is not curable at the moment
Treatments are only modestly effective in slowing down retinal degeneration
Patients tend to lose 50% of their remaining visual field every 5 years4
Complete visual loss is rare
RP is the most common hereditary retinal dystrophy, resulting in retinal degeneration and progressive vision loss.
Most cases result from sporadic mutations of the rhodopsin gene.
The most common symptoms include reduced peripheral and night vision.
The most common clinical findings include the classic clinical triad of bone-spicule retinal pigmentary changes, arteriolar attenuation and ‘waxy’ disc pallor.
Conservative management involves the use of low vision aid, visual rehabilitation and sunglasses.
Medical management involves the administration of oral or topical carbonic anhydrase inhibitors for secondary CMO.
Surgical management involves cataract surgery for secondary cataract.
Complications of non-managed RP can include cataract and CMO.
Fight for Sight. Retinitis pigmentosa. Published in 2019. [LINK]
Ferrari et al. Retinitis pigmentosa: genes and disease mechanisms. Published in 2011. [LINK]
Denniston AKO, Murray PI. Oxford Handbook of Ophthalmology. Published in 2018.
Grover S, Fishman GA, Anderson RJ et al. Rate of visual field loss in retinitis pigmentosa. Published in 1997. [LINK]
Image kindly provided by Dr Peng Yong Sim, Ophthalmology Registrar.