Clinical features:
(1) history of current therapy with chloroquine or hydroxychloroquine
(2) occurrence of visual changes - one or more of the following:
(2a) decreased visual acuity
(2b) change in color vision
(2c) visual field defects
(2d) night blindness
(2e) extraocular muscle palsy
(3) changes seen on fundoscopic examination
(3a) irregular macular pigmentation
(3b) zone of depigmentation as a pericentral oval ring
(3c) development of bull's eye atrophy
(3d) narrowing of arterioles
(3e) vascular sheathing
(3f) peripheral pigmentary retinopathy
(4) Fluorescein angiography done early in the clinical shows a ring of hyperfluorescence around the fovea, but this may fade with disease progression.
(5) Discontinuation of the offending drug can be followed by either clinical improvement or continued progression of the retinopathy.
The toxicity is dose-dependent, with hydroxychloroquine safer than chloroquine.
(1) Doses of chloroquine should be kept to < 250 mg per day or < 3.5 mg/kg per day.
(2) Ocular toxicity from chloroquine correlates with the total cumulative doses, with risk significant when > 300 grams.
(3) Doses of hydroxychloroquine should be kept to < 400 mg per day or < 6.5 mg/kg per day.
