MfERG could be most sensitive test for early detection of CQ/HCQ retinopathy

Researchers prospectively compared various screening methods for the early diagnosis of retinal dysfunction in patients undergoing long-term chloroquine (CQ) and hydroxychloroquine (HCQ) treatment. They found multifocal electroretinography (mfERG) to be the most sensitive test.

Subjects were 20 consecutive patients, all female, who received at least one year of CQ and HCQ treatment for rheumatoid disorders. All subjects underwent the following examinations in a single day at the same institution: case history, visual acuity, ophthalmoscopy, color vision, visual field, fluorescein angiography and mfERG. Tests were not repeated. The daily dosage was lower than 3.0 mg/kg CQ or lower than 6.5 mg/kg HCQ.

MfERG indicated retinal dysfunction in the parafoveal area in 14 patients. Towards the periphery, function was normal or only moderately reduced. Ophthalmoscopy and fluorescein angiography identified pathologic retinal changes in seven of these 14 patients. Six patients had normal mfERG, ophthalmoscopy and fluorescein angiography. Results of color vision and visual field testing were variable even in patients with morphologic alterations.

The results led the authors to suggest that, in the absence of fundus autofluorescence and spectral domain optical coherence tomography (SD-OCT), mfERG may be the best tool for early detection of CQ/HCQ toxicity. It is unknown whether fundus autofluorescence or SD-OCT would have identified abnormalities in these individuals, but the authors still advocate for the use of mfERG as the only objective functional test.