Abstract
Purpose
To study whether the ERG and other clinical findings help to distinguish between advanced hydroxychloroquine (HCQ) retinopathy and pericentral or diffuse retinitis pigmentosa (RP) with similar fundus appearance.
Methods
We conducted a retrospective analysis of patients with advanced HCQ retinopathy (n = 11), pericentral RP (n = 8) and diffuse RP (n = 8). Pericentral RP was defined as having limited fundus damage and relatively normal flicker ERG time-to-peak. Diffuse RP had typical loss of the rod ERG and flicker timing delay. All patients showed reduced amplitude of the ISCEV responses in the full-field electroretinogram (ERG). Aspects of history, visual field results, fundus appearance, fundus autofluorescence and ocular coherence tomography were also compared.
Results
Relative to pericentral RP, patients with HCQ toxicity showed delayed flicker ERG time-to-peak and lower ERG amplitudes, particularly combined rod–cone responses. Relative to diffuse RP, most HCQ toxicity patients had some preserved rod ERG response, and there was no obvious predilection for rod over cone damage. In addition, patients with HCQ toxicity usually lacked markers of long-standing degeneration such as bone spicule figures or severe loss of peripheral field. History of familial disease and long-standing night blindness were specific to RP.
Conclusions
While the early signs of HCQ damage are typically regional in the posterior pole, advanced disease is characteristically diffuse (unlike pericentral RP). This is appropriate for a systemic toxin, as is the finding that rods and cones were both affected in the ERG to a similar degree (unlike genetic rod–cone dystrophies). For patients with severe HCQ exposure and some of our discriminatory findings, and no family history or prior night blindness, HCQ toxicity is a sufficient diagnosis without invoking a second rare disease (Occam’s razor).
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All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership or other equity interest; and expert testimony or patent-licensing arrangements) or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.
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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. The article does not contain any studies with animals performed by any of the authors.
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Informed consent was waived by the Institutional Review Board of the Stanford University School of Medicine, as the study is a retrospective chart review.
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Nair, A.A., Marmor, M.F. ERG and other discriminators between advanced hydroxychloroquine retinopathy and retinitis pigmentosa. Doc Ophthalmol 134, 175–183 (2017). https://doi.org/10.1007/s10633-017-9588-8
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DOI: https://doi.org/10.1007/s10633-017-9588-8