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Retinitis Pigmentosa

Evidence-based assessment and management of retinitis pigmentosa. Comprehensive guide covering genetics, pathogenesis, classification, diagnosis, and treatment protocols for optometry practice.

Waxy paleoptic discBone-spiculepigmentationAttenuatedvesselsMacula(relatively preserved)Mid-peripheralpigment ringPerivascularpigment migration

Retinitis pigmentosa fundus: waxy pallor of the optic disc, markedly attenuated retinal vessels, and mid-peripheral bone-spicule pigmentation (perivascular pigment migration) — the classic triad. The central macula is relatively preserved in early-to-moderate disease.

Retinitis pigmentosa (RP) is the most common inherited retinal dystrophy, affecting approximately 1 in 4,000 people worldwide (over 1.5 million individuals globally). It is characterised by progressive degeneration of photoreceptors — predominantly rods first, then cones — leading to progressive peripheral visual field loss, night blindness, and eventually central visual impairment.

RP is caused by mutations in over 90 identified genes, encoding proteins essential for phototransduction, the visual cycle, retinal structure, or RNA splicing. It is inherited as autosomal dominant (AD), autosomal recessive (AR), X-linked (XL), or in rare cases digenic or mitochondrial patterns.

The classic fundus triad — waxy pallor of the optic disc, arteriolar attenuation, and mid-peripheral bone-spicule pigmentation — is pathognomonic. RP may occur in isolation (non-syndromic) or as part of a systemic syndrome (syndromic), the most common being Usher syndrome (RP + sensorineural hearing loss).

RP is a genetically heterogeneous disorder — over 90 causative genes have been identified, encoding proteins across multiple functional categories:

By Inheritance Pattern

  • Autosomal dominant (AD-RP) — ~15–25%: Key genes include RHO (rhodopsin; most common AD-RP gene, ~25% of AD cases), PRPF31, PRPF8, RP1, IMPDH1; generally milder and later onset
  • Autosomal recessive (AR-RP) — ~20–25%: Key genes include USH2A (also causes Usher syndrome type 2), CNGB1, CNGA1, PDE6A, PDE6B, TULP1, EYS; generally more severe, earlier onset
  • X-linked (XL-RP) — ~10–15%: RPGR (X-linked RP GTPase Regulator; accounts for ~70% of XL-RP) and RP2; most severe form; affects males predominantly; female carriers may show tapetal-like reflex
  • Simplex RP — ~40–50%: No family history; may be AD with reduced penetrance, AR, XL in a female carrier, or truly de novo mutation
  • Digenic RP (rare): Mutations in two genes required simultaneously — e.g., ROM1 + RDS/Peripherin
  • Mitochondrial (rare): RP associated with mitochondrial DNA mutations — e.g., Kearns-Sayre syndrome

By Encoded Protein Function

  • Phototransduction proteins: Rhodopsin (RHO), cGMP phosphodiesterase subunits (PDE6A, PDE6B), cyclic nucleotide-gated channels (CNGA1, CNGB1)
  • Visual cycle proteins: RPE65, CRALBP (RLBP1) — involved in retinoid recycling between RPE and photoreceptors
  • Structural / ciliary proteins: RPGR, RP1 — essential for photoreceptor outer segment structure and renewal
  • RNA splicing factors: PRPF31, PRPF8, PRPF3 — mutations cause AD-RP; explain why ubiquitous proteins can cause tissue-specific disease
  1. Gene mutation → dysfunctional protein in rod photoreceptors; most mutations cause misfolded protein (e.g., rhodopsin P23H), failed protein trafficking to outer segments, defective outer segment renewal, or impaired phototransduction — all leading to photoreceptor stress.
  2. Rod photoreceptor apoptosis — the primary degenerative event; rods die via multiple pathways including unfolded protein response (UPR), caspase-dependent apoptosis, oxidative stress, and calcium overload. Peripheral rods (where density is highest) are affected earliest → ring scotoma and night blindness.
  3. Secondary cone degeneration — rods produce trophic factors (including RdCVF — rod-derived cone viability factor) that support cones; as rods degenerate, cones are deprived of trophic support; additionally, elevated retinal oxygen tension (due to loss of oxygen-consuming rods) generates reactive oxygen species → cone oxidative damage → progressive central vision loss.
  4. RPE dysfunction and pigment migration — RPE cells attempt to phagocytose photoreceptor debris but are overwhelmed; RPE cells migrate along retinal vessels into the inner retina → characteristic bone-spicule pigmentation (perivascular pigment deposits; mid-peripheral distribution reflects the zone of maximal rod density and degeneration).
  5. Vascular attenuation — reduced metabolic demand from degenerating photoreceptors → retinal arteriolar constriction; vessels become markedly thin and thread-like over time.
  6. Optic disc changes — reactive gliosis and axonal loss → waxy yellow pallor of optic disc; distinguishable from other causes of disc pallor by the associated fundus findings.

By Inheritance / Genetics

TypePrevalenceKey GenesSeverity
AD-RP15–25%RHO, PRPF31, RP1Milder; later onset
AR-RP20–25%USH2A, EYS, PDE6A, PDE6BModerate-severe; earlier onset
XL-RP10–15%RPGR (~70% of XL-RP), RP2Severe; males affected; carriers show tapetal reflex
Simplex RP~40–50%VariousVariable; often AR or de novo
Digenic / MitochondrialRareROM1+RDS, mtDNAVariable

By Systemic Association

  • Non-syndromic RP: Isolated retinal disease; no systemic features; majority of cases
  • Syndromic RP: RP as part of a defined systemic syndrome (see Systemic Relations section); most common: Usher syndrome (>50% of syndromic RP)

By Photoreceptor Affected

  • Typical RP (rod-cone dystrophy): Rods affected first → night blindness and peripheral field loss; cones degenerate later → central vision loss; by far the most common pattern
  • Cone-rod dystrophy (CORD): Cones affected first → central vision and colour vision loss early; rods follow; classified separately but genetically related; distinct ERG pattern
  • Sector RP: Pigmentary changes confined to one or two quadrants (often inferior); milder prognosis; stable over many years
  • Pericentral RP: Rare; degeneration centred around the macula rather than mid-periphery; early central involvement
  • Family history: Most important risk factor; first-degree relatives of affected individuals should be offered genetic counselling and screening
  • Consanguinity: Significantly increases risk of AR-RP; relevant in populations where consanguineous marriages are common (Middle East, South Asia)
  • X-linked carrier status (female): Female carriers of XL-RP mutations (RPGR, RP2) may show a tapetal-like sheen, sector pigmentation, or mild ERG changes; small risk of manifesting carriers
  • Specific gene mutations: Certain mutations are more severe (e.g., rhodopsin P23H → AD-RP with highly variable severity; null mutations in RPGR → severe XL-RP)
  • Associated systemic syndromes: Usher syndrome, Bardet-Biedl, Refsum disease — RP is a component; systemic diagnosis increases probability of RP
  • Environmental modifiers (minor): Chronic light exposure may accelerate rod degeneration; UV protection potentially beneficial; vitamin A deficiency may worsen RP but is not a primary cause
  • Immune-mediated (rare): Cancer-associated retinopathy (CAR) and autoimmune retinopathy can mimic RP; not hereditary but share phenotype

Classic Fundus Triad (pathognomonic of RP)

  • Waxy pallor of the optic disc: Pale yellow-white disc; gliosis and axonal loss; less cup-to-disc ratio change than glaucoma; hallmark of advanced RP
  • Arteriolar attenuation: Markedly thin, thread-like retinal arterioles; reduced metabolic demand from degenerating photoreceptors; may be the first fundus sign in early disease
  • Mid-peripheral bone-spicule pigmentation: Perivascular pigment deposits in mid-peripheral retina; branching, stellate shape resembling bone spicules; caused by RPE cell migration along vessel walls

Additional Fundus Signs

  • Posterior subcapsular cataract (PSC): Present in up to 50–70% of patients; often bilateral; exacerbates visual loss; treatable surgically
  • Cystoid macular oedema (CMO): Perifoveal fluid accumulation; present in ~20–30% of RP patients; partially treatable; contributes to central vision loss
  • Epiretinal membrane (ERM): Cellophane-like membrane on inner macular surface; causes distortion; may require surgical peeling
  • Macular hole: Full-thickness break at fovea; rare complication; surgical management
  • Vitreous cells / pigment: Scattered pigment cells and inflammatory cells in vitreous; visible with slit-lamp in dilated eye
  • Tapetal-like reflex: Golden-metallic sheen seen in female XL-RP carriers; caused by abnormal ILM reflectance
  • Fundus albipunctatus (related): White dots at level of RPE; distinguished from RP by stable visual fields and ERG normalisation after extended dark adaptation

Anterior Segment Signs

  • Posterior subcapsular cataract: Snowflake opacities on posterior lens capsule; earlier and more prevalent than age-matched controls
  • Keratoconus: Slightly increased prevalence in RP; may affect refraction and visual acuity disproportionately
  • Night blindness (nyctalopia): Earliest and most characteristic symptom; impaired vision in dim light; rod function lost before cones; often present in childhood in XL and AR forms; may be the presenting complaint in young adults
  • Progressive peripheral visual field loss: “Tunnel vision” — concentric constriction of visual field; often unnoticed until severely constricted; ring scotoma at 30–50° is the characteristic early field defect
  • Photophobia: Light sensitivity; particularly in cone-rod dystrophy forms; glare from bright lights
  • Slow dark adaptation: Prolonged time to adapt when moving from bright to dim environments; patients notice difficulty in cinemas, at dusk, or when entering dim rooms
  • Blurred central vision: Late symptom in typical (rod-cone) RP; onset coincides with macular involvement; may be worsened by CMO (which is partially treatable)
  • Colour vision disturbance: Late symptom as cones degenerate; predominantly blue-yellow colour axis affected initially
  • Visual fatigue: Difficulty with sustained visual tasks; reported even with reasonable central acuity
  • Flashing lights / photopsies: Some patients report photopsies or flickering; may be related to abnormal photoreceptor signalling

Macular

  • Cystoid macular oedema (CMO): Most important treatable complication; present in 20–30%; causes disproportionate central VA loss; responds to carbonic anhydrase inhibitors; OCT monitoring essential
  • Epiretinal membrane (ERM): Traction and distortion; surgical peeling possible but risk-benefit must be considered given the underlying dystrophy
  • Macular hole: Full-thickness foveal break; rare; vitreoretinal surgery required
  • Macular atrophy: End-stage degeneration of central photoreceptors; irreversible central blindness

Lens

  • Posterior subcapsular cataract (PSC): Occurs in up to 50–70%; causes glare and reduced contrast; phacoemulsification improves VA in eyes with residual macular function; important to assess macular function pre-operatively (ERG, OCT)

Visual Disability

  • Legal blindness: Defined as VA <6/60 or visual field <10° in the better eye; reached by ~25% of patients by age 50 in XL-RP and AR-RP
  • Complete blindness: End-stage; more common in XL and severe AR forms; AD-RP patients often retain some residual vision into older age
  • Driving inability: Visual field constriction renders driving unsafe well before central VA falls; optometrists play a key role in driving fitness assessment

Psychological / Quality of Life

  • Depression and anxiety: common in patients with RP given progressive and incurable nature; psychosocial support and low vision rehabilitation are essential

RP occurring as part of a systemic syndrome (syndromic RP) accounts for ~20–30% of all RP cases. Usher syndrome is the most common.

SyndromeKey Systemic FeaturesGenetics
Usher Syndrome (Types 1–3)Sensorineural hearing loss (congenital profound in type 1; moderate in type 2; progressive in type 3) ± vestibular dysfunctionAR; USH2A (type 2), MYO7A (type 1), CLRN1 (type 3)
Bardet-Biedl Syndrome (BBS)Obesity, polydactyly, renal anomalies, cognitive impairment, hypogonadism, cardiac defectsAR; BBS1–21 genes (ciliopathy)
Refsum DiseasePeripheral neuropathy, cerebellar ataxia, sensorineural deafness, elevated serum phytanic acid; treatable with phytanic acid-restricted dietAR; PHYH, PEX7
Kearns-Sayre SyndromeProgressive external ophthalmoplegia (PEO), ptosis, cardiac conduction defects (complete heart block — life-threatening), myopathy; onset <20 yearsMitochondrial DNA deletion
Laurence-Moon SyndromeSpastic paraplegia, cognitive impairment, hypogonadism; rarer; historically confused with BBSAR
Joubert SyndromeCerebellar vermis hypoplasia ("molar tooth" sign on MRI), hypotonia, ataxia, oculomotor apraxia, renal diseaseAR; ciliopathy (INPP5E, CEP290)
Senior-Løken SyndromeNephronophthisis (juvenile renal failure) + RP/Leber congenital amaurosisAR; NPHP1, SDCCAG8

Clinical implication: All RP patients should be screened for hearing loss (audiometry), renal function (urinalysis, eGFR), and systemic features of BBS. Referral to genetics and relevant specialty teams is essential in syndromic cases.

  • Full-field electroretinogram (ERG) — gold standard: Severely reduced or extinguished scotopic (dark-adapted, rod-driven) responses; early; photopic (cone) responses reduced later; ISCEV standards required; ERG may be extinguished before overt fundus signs appear in young patients
  • Visual field testing: Goldmann perimetry (manual) for full-field mapping; automated perimetry (HVF 30-2 or 60-4) for monitoring; characteristic ring scotoma at 30–50°; concentric constriction in advanced disease; measure annually
  • OCT (optical coherence tomography): Quantify ellipsoid zone (EZ) width and integrity — correlates directly with visual acuity and photoreceptor survival; detect CMO, ERM, macular hole; monitor progression
  • Fundus photography / wide-field imaging: Document bone-spicule pigmentation, disc pallor, vascular attenuation; baseline and serial photography for progression monitoring
  • Dark adaptometry: Prolonged dark adaptation curve; elevated final rod threshold; quantifies rod dysfunction and correlates with night blindness severity; useful for early/presymptomatic diagnosis
  • Colour vision testing: D-15, Farnsworth-Munsell 100-hue; predominantly blue-yellow axis in early cone involvement; confirms cone dysfunction stage
  • Genetic testing (panel sequencing): Multi-gene retinal dystrophy panel (90+ genes); essential for: (1) confirming diagnosis, (2) determining inheritance pattern, (3) family counselling, (4) eligibility for gene therapy trials; identifies causative mutation in ~60–70% of cases
  • Slit-lamp examination: PSC, vitreous cells, pigment; keratoconus
  • Systemic screening: Audiometry (Usher syndrome); renal function and urinalysis (BBS, Senior-Løken); serum phytanic acid (Refsum disease); cardiac evaluation (Kearns-Sayre: ECG essential)

1. Disease-Modifying / Neuroprotective Therapies

  • Vitamin A palmitate (15,000 IU/day): Randomised controlled trial (Berson et al., 1993) showed modest slowing of ERG amplitude decline (~2%/year); widely recommended for most adult RP patients; avoid in pregnancy (teratogenic); monitor liver function; avoid excess vitamin E (may offset benefit); not beneficial in XL-RP patients taking vitamin A
  • Docosahexaenoic acid (DHA) supplementation: May have additional benefit when combined with vitamin A in certain subgroups (Berson et al. follow-up); evidence less robust; omega-3 supplementation reasonable adjunct
  • UV protection: Sunglasses with UV-blocking lenses; reduces phototoxic stress to degenerating photoreceptors; strongly recommended
  • Avoid excess vitamin E (>400 IU/day): Berson trial showed vitamin E accelerated ERG decline; advise patients to avoid high-dose vitamin E supplements

2. Gene Therapy (precision medicine)

  • Voretigene neparvovec (Luxturna): AAV2 vector delivering functional RPE65 gene; FDA-approved (2017) and EMA-approved; indicated for RPE65-mediated inherited retinal dystrophy (Leber congenital amaurosis type 2 / RPE65-RP); subretinal injection; significant VA and mobility course improvement; landmark gene therapy approval for an ocular disease
  • Other gene therapy programmes (clinical trials): RPGR (XL-RP; multiple trials), CNGB3 (achromatopsia), CNGA3, MYO7A (Usher 1B) — not yet approved; refer to specialist genetics/retinal centre

3. Treatment of Complications

  • CMO — carbonic anhydrase inhibitors (CAIs): Oral acetazolamide 250–500 mg/day (Fishman et al., 1989) or topical dorzolamide 2% BD — reduces CMO in ~50% of patients; monitor renal function; long-term use common
  • PSC cataract: Phacoemulsification when VA is significantly impaired; essential to assess residual macular function pre-operatively with ERG and OCT (surgery improves acuity only if macula is functional)
  • ERM: Pars plana vitrectomy with membrane peeling for significant distortion; consult vitreoretinal surgeon

4. Visual Rehabilitation

  • Low vision aids: magnifiers, telescopic lenses, electronic magnification systems (tablets, CCTV)
  • Night vision aids: image-intensifying (NVG-style) monoculars for low-light mobility
  • Mobility training and orientation services (Guide Dogs, cane training)
  • Tinted lenses (amber/yellow) to reduce glare and photophobia
  • Assistive technology: screen readers, voice-activated devices, large-print materials

5. Genetic Counselling

  • Refer all patients and families for genetic counselling once a molecular diagnosis is established
  • Discuss inheritance, recurrence risk, family screening, reproductive options (preimplantation genetic testing)
  • Enrol in registries and trial databases for future gene therapy eligibility

6. Experimental / Emerging Therapies

  • Retinal prosthesis (Argus II / epiretinal implant): For profoundly blind RP patients with residual ganglion cells; limited availability; modest functional improvement in eligible patients
  • Stem cell therapy: RPE cell transplantation; photoreceptor precursor cells; multiple early-phase trials; not yet standard care
  • CRISPR/gene editing, antisense oligonucleotides: Investigational; show promise for specific mutations (e.g., CEP290 intronic mutation in LCA)
  • Neuroprotection (CNTF, BDNF): Clinical trials ongoing; CNTF slow-release implant (NT-501) — mixed results

Singapore Optometry Scope Note: Optometrists in Singapore play an important role in the ongoing monitoring of RP — including visual field testing, OCT imaging, fundus photography, and detection of treatable complications (CMO, PSC, ERM). Optometrists may conduct low vision assessments and facilitate referral to low vision rehabilitation services. Genetic testing, gene therapy, systemic syndrome evaluation, and surgical interventions (cataract, vitrectomy) require ophthalmology and genetics co-management. Counsel all RP patients on UV protection, vitamin A supplementation (after ophthalmology guidance), and the importance of annual review.

  • Variable and inheritance-dependent: XL-RP and severe AR-RP (e.g., EYS mutations) have early onset and rapid progression; AD-RP (RHO-related) is generally milder with slower progression and better long-term VA
  • Visual field: Rate of field constriction averages 4.6% per year (Grover et al.); significant inter-patient variability; Goldmann III4e isopter area halves approximately every 10 years in some studies
  • Visual acuity: Central VA often maintained until 4th–5th decade in typical RP; accelerated loss if CMO or PSC not treated; macular atrophy leads to irreversible central loss in late disease
  • Legal blindness: ~25% of XL-RP and severe AR-RP patients by age 50; AD-RP patients often maintain driving-standard VA into later life
  • CMO treatment effect: Oral acetazolamide reduces macular thickness and improves VA in ~50% of RP-CMO cases; long-term treatment may be needed; CMO recurs on cessation
  • Gene therapy (RPE65): Luxturna shows durable visual improvement at 3–4 years post-treatment; earlier treatment when more retinal cells remain provides better outcomes
  • Vitamin A: Modest protective effect (Berson 1993); ERG decline rate ~2%/year slower; not curative
  • Key poor prognostic factors: XL or severe AR inheritance; early onset; central involvement; RPE65, RPGR null mutations; uncontrolled CMO; absence of gene therapy eligibility
  • Key favourable factors: AD-RP; later onset; sector RP; RHO-related AD-RP (milder alleles); genetic diagnosis enabling trial eligibility; treated CMO
ConditionKey Differentiator from RP
ChoroideremiaXL; peripheral choroidal/RPE atrophy (scalloped, pale periphery); no bone spicules; female carriers show peripheral tapetal-like reflex; CHM gene (Rab escort protein 1)
Gyrate AtrophyAR; PHYH-like circular atrophic areas in periphery coalescing centrally; elevated plasma ornithine (>10×); OAT gene; responsive to arginine-restricted diet + pyridoxine
Cone-Rod Dystrophy (CORD)Cones affected first → central VA and colour vision lost early before peripheral field; ERG shows photopic > scotopic reduction; "bull's eye" maculopathy; AD, AR, XL
Leber Congenital Amaurosis (LCA)Severe visual impairment from birth or early infancy; nystagmus; oculo-digital sign (eye poking); ERG extinguished in first year; RPE65, CEP290, GUCY2D mutations; earlier and more severe than typical RP
Pseudo-RP (Drug-induced)Phenothiazines (thioridazine, chlorpromazine), hydroxychloroquine; pigmentary retinopathy mimicking RP; drug history essential; non-hereditary
Syphilitic RetinopathyAcquired pigmentary retinopathy; "salt-and-pepper" or bone-spicule pattern; history of syphilis; positive VDRL/TPHA; treatable with penicillin
Rubella RetinopathyCongenital infection; "salt-and-pepper" pigmentary changes; maternal rubella history; ERG may be relatively preserved; not progressive in typical cases
Cancer-Associated Retinopathy (CAR)Paraneoplastic; anti-recoverin antibodies; rapid onset visual loss; associated with small-cell lung cancer, gynaecological malignancies; ERG extinguished; serum autoantibody panel positive
Fundus AlbipunctatusWhite dots at RPE level; night blindness but stable visual fields; ERG normalises after extended dark adaptation (distinguishes from RP); RLBP1 gene
Enhanced S-Cone Syndrome (ESCS)AR (NR2E3 gene); nyctalopia but enhanced sensitivity to blue/short-wavelength light; unique ERG pattern (enhanced S-cone response); retinal schisis-like changes on OCT
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