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Retinal Degenerations and Dystrophies

RETINITIS PIGMENTOSA

Tomas S. Aleman, MD

• Molecularly heterogeneous group of inherited outer retinal degenerations that causes a bilateral, slowly progressive, pigmentary retinopathy
  
• Prevalence: Approximately 1:3500 and inherited in an autosomal recessive, dominant, or X-linked recessive pattern. Mitochondrial inheritance may exist in rare cases.
  
• Symptomatic onset typically in early adulthood although presentation can range from preschool years (early-onset retinal degenerations [EORDs]) to late adulthood (late-onset retinal degenerations [L-ORD])
  
• Syndromic retinitis pigmentosa (RP) distinguishes patients with confirmed or suspected systemic abnormalities (eg, sensorineural hearing loss, neurologic, and metabolic defects) from patients with only retinal disease [non-syndromic RP])

Initial grayish appearance of retinal pigment epithelium (RPE) with or without white spotted lesions; mid-peripheral, annular-like, pigmentary retinopathy later develops that expands both centripetally and centrifugally with age; waxy appearance to optic nerve and arteriolar attenuation with progression; vitreous cells may be present; end-stage disease characterized by diffuse pigmentary retinopathy with a depigmented or atrophic macula and total vision loss; posterior subcapsular cataracts in > 50%; cystoid macular edema (CME) may develop and epiretinal membranes are common (Figure 5-1A)

Testing

• Kinetic perimetry (Goldmann): mid-peripheral scotomas, generalized constriction with variable peripheral remnants of vision
  
• Color vision: preserved early on, tritan defects and multiple axis of confusion later in disease
  
• Short-wavelength fundus autofluorescence (AF) imaging: central islands of normal AF separated from peripheral regions of hypoautofluorescence by narrow hyperautofluorescence rings (Figure 5-1B)
  
• Optical coherence tomography (OCT): localized or diffuse photoreceptor outer segment loss and outer nuclear layer (ONL) thinning; total retinal thinning may be masked by a thickened inner retina due to remodeling (Figure 5-1C)
  
• Fluorescein angiography (FA): window defects from RPE loss; non-leaking CME; infrequently, choroidal neovascularization (CNV)
  
• Electroretinography (ERG): abnormally reduced amplitudes with a rod > cone dysfunction

Cone dysfunctions and cone-rod dystrophies; congenital stationary night blindness, fundus albipunctatus, retinitis punctata albescens, severe Stargardt disease; choroidal dystrophies (choroideremia, gyrate atrophy, Bietti’s crystalline dystrophy, central areolar and dystrophies, helicoidal); carrier state of inherited retinal degenerations (IRD; X-linked RP, choroideremia); hereditary vitreoretinopathies (familial exudative vitreoretinopathy, Wagner and Stickler syndromes); autoimmune retinopathies; acute zonal occult outer retinopathy (AZOOR); post-infectious or post-inflammatory pigmentary retinopathies (pars planitis, birdshot chorioretinopathy, serpiginous retinopathy, multifocal placoid pigment epitheliopathy, sarcoidosis, rubella, syphilis, toxocara); vitamin A deficiency and abetalipoproteinemia; toxic retinopathies (thioridazine, chloroquine); neuro-ophthalmic diseases with inner retinal and visual field loss

CONE DYSTROPHIES

Tomas S. Aleman, MD

• Autosomal recessive and X-linked recessive patterns
  
• Stereotypical disease for this group of disorders is achromatopsia or total color blindness
  
• Incomplete forms: variable degree of residual cone function
  
  
  
  • Blue cone monochromatism or rod monochromatism are X-linked subtype with preserved blue cone function
  
  
• Prevalence varies depending on molecular cause but is ~1:30,000 to 50,000

Fundus exam normal or blunted foveal reflex; may have small areas of depigmentation in and around foveal center; foveal atrophy occurs rarely (Figure 5-2A)

Testing

• Kinetic perimetry (Goldmann): fields mostly full or show mild generalized constriction
  
• Color vision: severely abnormal
  
• Full-field sensitivity testing (FST): normal rod-mediated sensitivities, severely abnormal cone vision
  
• Short-wavelength fundus AF imaging: preserved although may have central hypoautofluorescence in forms with more severe central disease (Figure 5-2B)
  
• OCT: foveal hypoplasia in some; foveal thinning with shortening and loss of the cone photoreceptor outer segment mainly at fovea (Figure 5-2C)
  
• ERG: normal rod function, cone ERGs are extremely reduced in amplitude to undetectable

• Referral to comprehensive pediatric ophthalmologist for optimal correction of refractive errors, assessment of ocular alignment and amblyopia
  
• Referral to child development and educational specialists for early intervention and low vision rehabilitation
  
• Several promising gene therapy approaches are being tested (https://clinicaltrials.gov)

STARGARDT DISEASE

Tomas S. Aleman, MD

• Most frequent juvenile macular dystrophy with a prevalence of ~1:10,000 and onset typically in adolescence
  
• Typically autosomal recessive and associated with ABCA4 gene mutations
  
• Onset and severity variable with milder forms showing adult onset and relative foveal preservation without atrophy termed fundus flavimaculatus (FFM)

Signs and Symptoms

Vision loss, impaired color vision

Exam Findings

Normal or blunted foveal reflex in early stages; variable central depigmentation and atrophy with a tapetal or beaten bronze sheen; pisciform whitish-yellow flecks distributed as an annulus around center and into mid-periphery which expand centripetally while most central lesions fade into central RPE atrophy (Figure 5-3A)

Testing

• Kinetic perimetry (Goldmann): fields are full peripherally with variable central scotomas depending on stage
  
• Static perimetry: central scotomas
  
• Color vision: normal in early disease, abnormal in later stages

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