Description
Chloroquine (Aralen) and hydroxychloroquine (Plaquinel) are used in the prophylaxis and treatment of malaria and a variety of rheumatological diseases (e.g., systemic lupus erythematosus, rheumatoid arthritis). The drugs become concentrated within the melanin-containing structures of the eye such as the retinal pigment epithelium (RPE) and choroid. Established retinopathy is associated with degeneration and atrophy of the RPE and damage to the adjacent neurosensory retina, with reduced visual acuity and visual fields. These changes are often irreversible.
Symptoms
Symptoms include blurred central vision, altered colour vision and difficulty adjusting to darkness.
Signs
Reduced central visual acuity and central or paracentral scotomas are often detectable in patients with early maculopathy. The characteristic ‘bull’s eye’ macula appears as central ring of depigmentation (RPE atrophy) surrounded by a ring of hyperpigmentation. Whorl-like corneal changes may also exist (‘vortex keratopathy’). With progressive toxicity, visual acuity continues to deteriorate. Choroidal vessels become visible beneath areas of RPE atrophy, and RPE clumps appear in the peripheral retina.
Prevalence
Retinopathy is unlikely with a cumulative chloroquine dose below 100 grams, or with treatment for less than one year. Hydroxychloroquine causes retinopathy far less frequently than chloroquine.
Differential Diagnosis
Other causes of a bull’s-eye macula: Cone Cystrophy, Stargardt Disease, Retinitis Pigmentosa, Age-Related Macular Degeneration.
See Also
Phenothiazine Retinopathy.
Management
Additional tests
Automated visual field testing and fluorescein angiography may facilitate diagnosis. Visual field assessment using a central 10 degree test and a red target may enable the earliest detection of retinal toxicity. Areas of hypopigmentation are hyperfluorescent at angiography, due to the RPE window defect.
Oral medications
Since established chloroquine maculopathy is often irreversible, observation of retinopathy may indicate consultation with the rheumatologist regarding the medication.
Advice
Patients are given an Amsler grid, educated on its use, and advised to represent if they note any visual changes.
Review
In general, patients taking chloroquine or hydroxychloroquine should be reviewed at least every 12 to 18 months. More frequent review is recommended for patients with a cumulative chloroquine dose above 200g, and those with renal and/or liver impairment or previously documented retinopathy.
Figure 1
Left eye of a 40 year old female who had been taking chloroquine for systemic lupus erythematosus. “Bulls Eye” degenerative changes were present at the maculae.
Figure 2
Mild bulls eye pattern around the macula.
Figure 3
Same eye, fluorescein angiogram which highlights the circular window defect in the pigment epithelium surrounding the macula.