11/14/24, 10\:46 AM Retinitis Pigmentosa (RP)

Retinitis Pigmentosa (RP)

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Retinitis pigmentosa (RP)\: inherited retinal disorder causing progressive vision loss; most common hereditary retinal
dystrophy; prevalence ~1 in 4,000 in the UK.
Causes\: mutations in genes for photoreceptor and retinal pigment epithelium (RPE) function, commonly the rhodopsin
gene.
Risk factors\: genetic predisposition (autosomal dominant, autosomal recessive, X-linked, sporadic), syndromic RP (e.g.,
Usher syndrome, Bardet-Biedl syndrome).
Symptoms\: reduced peripheral vision (tunnel vision), night blindness (nyctalopia), impaired dark adaptation, photopsia
(
Clinical
‘waxy’ optic disc pallor, RPE
atrophy; other
Di
drug toxicity (chloroquine, thioridazine hydrochloride).
Investigations\:
Bedside\: visual acuity (VA), confrontational visual
Specialist\: electroretinogram (reduced ‘a’ and ‘b’ wave amplitudes), perimetry (ring scotoma), genetic testing, optical
coherence tomography (for CMO).
Management\:
Conservative\: low vision aids, visual rehabilitation, sunglasses.
Medical\: treat CMO with carbonic anhydrase inhibitors (e.g., dorzolamide, acetazolamide).
Surgical\: cataract treatment.
Follow-up\: annual follow-up for detecting treatable complications and providing support.
Complications\: cataracts, cystoid macular oedema (CMO).
Prognosis\: no cure; treatments modestly e
loss is rare.
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Introduction

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.
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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 % Prognosis
Sporadic 30 Good
Autosomal dominant 25 Best
Autosomal recessive 20 Poor
X-linked 15 Poorest

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
assessed by primary care physicians who then make an ophthalmology referral.

History

Patient with suspected RP will primarily complain about not being able to see well in low-light environments or will have
di
vision unless the symptoms have been occurring over a prolonged period of time.
Typical symptoms of RP include\:
Reduced peripheral vision or “tunnel vision”
Nyctalopia (night blindness)
Impaired dark adaptation
Photopsia (
Glare
Reduced central vision
Rod photoreceptors are a
to the above symptoms.
Other important areas of the history include\:
Past medical history\: including previous ocular issues and infections such as syphilis or rubella which can mimic the
symptoms of RP.
Medication history\: chloroquine and thioridazine hydrochloride can cause ocular signs similar to RP.
Family history\: 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.
Occupation and driving\: RP may have implications for the patient's job and their ability to drive.

Clinical examination

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.
Typical clinical
Bone-spicule retinal pigmentation
Arteriolar attenuation
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‘Waxy’ optic disc pallor
Retinal pigment epithelium (RPE) atrophy
Other
Myopia
Cataract (posterior subcapsular subtype)
Optic disc drusen
Cystoid macular oedema (CMO)
Figure 1.Right fundus photography showing the classic triad of mid-peripheral bone-spicule retinal pigmentation, arteriolar
attenuation and ‘waxy’ optic disc pallor in RP.
5

Di

The clinical presentation of RP is similar to several other conditions that cause pigmentary retinopathy.

Genetic

Genetic diseases which can present with similar clinical features to RP include\:
Leber congenital amaurosis
Gyrate atrophy
Choroideremia

Infection

Infections which can present with similar clinical features to RP include\:
Syphilis
Rubella
Di

Drug toxicity

Drugs which can present with similar clinical features to RP include\:
Chloroquine
Thioridazine hydrochloride
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Investigations

Bedside investigations

Relevant bedside investigations include;
Assessment of visual acuity (VA) with a Snellen chart\: patients may have normal VA or myopia.
Confrontational visual
Fundoscopy\: typical
and RPE atrophy.
‘waxy’ optic disc pallor

Specialist investigations

Relevant specialist investigations performed by ophthalmology include\:
Electroretinogram\: typical
in early disease. Patients with advanced disease may have a non-detectable ERG.
Perimetry (formally assesses any visual
is most commonly noted.
Genetic testing\: to assess for rhodopsin gene mutation and other common variants.
Optical coherence tomography\: to con

Management

Conservative

Conservative management involves supportive measures to optimise vision including\:
Low vision aids (e.g. glasses, magni
Visual rehabilitation
Sunglasses (to limit UV exposure)

Medical

Medical management involves treating RP associated complications such as CMO with carbonic anhydrase inhibitors (e.g.
topical dorzolamide initially or oral acetazolamide if no improvement).
4

Surgical

Surgical management involves treating RP associated complications such as cataracts.

Follow-up

support.
Patients with RP typically receive annual follow-up to detect treatable vision-threatening complications and provide

Complications

Complications of RP include\:
Cataracts
Cystoid macular oedema (CMO)

Prognosis

There is no cure for RP and treatments are only modestly e
Patients typically lose 50% of their remaining visual
4
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References

Fight for Sight. R e t i n i t i s p i g m e n t o s a . Published in 2019. Available from\: [LINK]
Ferrari et al. R e t i n i t i s p i g m e n t o s a \: g e n e s a n d d i s e a s e m e c h a n i s m s . Published in 2011. Available from\: [LINK]
Denniston AKO, Murray PI. O x f o r d H a n d b o o k o f O p h t h a l m o l o g y . Published in 2018.
Grover S, Fishman GA, Anderson RJ et al. R a t e o f v i s u a l
[LINK]
Image kindly provided by Dr Peng Yong Sim, Ophthalmology Registrar.

Reviewer

Dr Peng Yong Sim
Ophthalmology Registrar

Related notes

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Anisocoria

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Contents

Introduction
Causes and risk factors
History and examination
Di
Investigations
Management
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