Hannah Levin, BS and Jason Hsu, MD
Crystalline deposits in retina of variable distribution depending on associated condition (Figure 8-1 and Table 8-1)
Signs and Symptoms
Vision loss varies by associated condition and ranges from asymptomatic to mild decrease in visual acuity or color vision to severe vision loss
Exam Findings
Varies based on etiology (see Table 8-1)
Figure 8-1. Canthaxanthin crystalline retinopathy. (A) Fundus photographs indicate bilateral crystals in a ring surrounding the fovea. (B) OCT shows crystals in the inner retina (arrows). Patient had history of oral canthaxanthin use for tanning.
Testing
- Optical coherence tomography (OCT): depicts depth of crystals within retina and associated retinal pigment epithelial (RPE) atrophy, vitreous hemorrhage, retinal thinning, cystic foveal cavitation, ellipsoid zone (EZ) disruption (Figure 8-1B)
- Fluorescein angiography (FA): determine concurrent findings such as edema, non-perfusion, atrophy, leakage, enlarged foveal avascular zone
- Electroretinogram: reduced amplitudes in select associated conditions (eg, tamoxifen- and cystinosis-related crystals)
- Color vision: may be compromised in select associated conditions
Differential Diagnosis
Intraretinal crystals—drug associated: tamoxifen, canthaxanthin, methoxyflurane, nitrofurantoin, talc; systemic: cystinosis, Sjögren-Larsson syndrome, embolic disease; primary ocular: idiopathic, macular telangiectasia, chronic retinal detachment; idiopathic: West African crystalline maculopathy, white dot fovea; iatrogenic: history of retina surgery with Tano scraper
Subretinal crystals—Bietti’s crystalline dystrophy, calcified drusen, oxalosis
Management
Prevention, monitoring, and treatment of any associated conditions (see Table 8-1)
CHLOROQUINE/HYDROXYCHLOROQUINE RETINAL TOXICITY
David Xu, MD and James F. Vander, MD
- Risk increases with dosage, duration of use, lower body weight, concurrent renal disease and retinal disease
- Daily dosage of hydroxychloroquine > 5 mg/kg or chloroquine > 3 mg/kg are associated with increased risk
Signs and Symptoms
Early and moderate disease may be asymptomatic; advanced toxicity associated with bilateral blurry vision, poor night vision, decreased peripheral vision, and color vision deficits
Exam Findings
Usually bilateral and symmetric; early toxicity can have a normal appearing fundus or show granular hypopigmentary parafoveal changes and a blunted foveal light reflex; advanced toxicity leads to Bull’s eye maculopathy (parafoveal RPE atrophy)
Testing
- Perimetry: paracentral scotoma
- OCT: mild EZ discontinuity early and parafoveal EZ loss and outer retinal atrophy (“flying saucer sign”) later (Figure 8-2A)
- Multifocal electroretinography: paracentral amplitude loss
- Fundus autofluorescence: parafoveal hyperautofluorescence early and hypoautofluorescence late (Figure 8-2B)
Differential Diagnosis
Stargardt disease, age-related macular degeneration, cone or cone-rod dystrophy, Bardet-Biedl syndrome
Management
- Screening: patients should undergo a baseline retinal evaluation with spectral domain-OCT and automated perimetry (central 10 degrees with white test stimulus except East Asian patients who should have 24 degree visual field test since toxicity may arise outside the macula) and receive annual screening after 5 years of therapy
- Discontinue at first signs of toxicity as further progression may occur even after cessation of medication
Figure 8-2. Hydroxychloroquine toxicity. (A) OCT demonstrates thinning and attenuation of the parafoveal and macular EZ (outside of arrows). (B) Fundus autofluorescence of a different patient demonstrates parafoveal hyperautofluorescence in a Bull’s eye pattern in relatively early toxicity.
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