Background:
The American Academy of Ophthalmology recommendations for
screening of chloroquine (CQ) and hydroxychloroquine (HCQ) retinopathy were
published in 2002, but improved screening tools and new knowledge about the
prevalence of toxicity have appeared in the ensuing years. No treatment exists
as yet for this disorder, so it is imperative that patients and their physicians
be aware of the best practices for minimizing toxic damage.
Risk of Toxicity:
New data have shown that the risk of toxicity increases
sharply toward 1% after 5 to 7 years of use, or a cumulative dose of 1000 g, of
HCQ. The risk increases further with continued use of the drug.
Dosage:
The prior
recommendation emphasized dosing by weight. However, most patients are
routinely given 400 mg of HCQ daily (or 250 mg CQ). This dose is now considered
acceptable, except for individuals of short stature, for whom the dose should be determined on the
basis of ideal body weight to avoid overdosage.
Screening Schedule:
A baseline examination is advised for patients starting
these drugs to serve as a reference point and to rule out maculopathy, which
might be a contraindication to their use. Annual screening should begin after 5
years (or sooner if there are unusual risk factors).
Screening Tests: Newer objective tests, such as multifocal electroretinogram (mfERG), spectral domain optical coherence tomography (SD-OCT), and fundus autofluorescence (FAF), can be more sensitive than visual fields. It is now recommended that along with 10-2 automated fields, at least one of these procedures be used for routine screening where available. When fields are performed independently, even the most subtle 10-2 field changes should be taken seriously and are an indication for evaluation by objective testing. Because mfERG testing is an objective test that evaluates function, it may be used in place of visual fields. Amsler grid testing is no longer recommended. Fundus examinations are advised for documentation, but visible bull’s-eye maculopathy is a late change, and the goal of screening is to recognize toxicity at an earlier stage.
Counseling:
Patients should be aware of the risk of toxicity and the
rationale for screening (to detect early changes and minimize visual loss, not
necessarily to prevent it). The drugs should be stopped if possible when toxicity
is recognized or strongly suspected, but this is a decision to be made in
conjunction with patients and their physicians.
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