Background/Purpose: Hydroxychloroquine (HCQ) is widely used in the treatment of rheumatic diseases. The use of HCQ is complicated by HCQ-induced retinopathy, which may lead to irreversible visual loss. Current guidelines recommend annual screening for ocular damage with optical coherence tomography (OCT) and visual field (VF) testing beginning after 5 years of treatment with HCQ.

Dark Adaptometry (DA) tests the ability of the retina to recover its sensitivity after exposure to a bright, calibrated flash of light. This test shows high sensitivity and specificity as a biomarker for macular degeneration, a disease of the central retina. We hypothesized that DA might be more sensitive to retinal changes consequent to HCQ treatment than currently recommended tests and thus be useful as a novel screening test for HCQ retinopathy. We performed a pilot study to establish this test’s diagnostic potential.

Methods: Patients aged 20-70 were eligible for participation if they had documentation of current treatment with HCQ and at least one prescription annually for the preceding 3 or more years. Exclusion criteria included diabetes mellitus, treatment with tamoxifen, active ocular disease and patients with high myopia. Patients were also excluded if they had not had an eye examination, including VF or OCT within the prior 18 months.

DA was performed using the Rapid Test protocol on all patients. In this protocol, patient subjects who did not reach a criterion level of sensitivity prior to 6.5 minutes were deemed to have failed the test.

Results: Thirty patients aged were recruited from a large multispecialty group practice and an academic optometry clinic. HCQ daily dosages at the time of the DA study ranged from 1.8 to 6.8 mg/kg with a median of 4.0 mg/kg. Cumulative dosages ranged from 420g to 4700g. with a median of 930g. The median number of years since HCQ was first prescribed was 9. No subjects had symptoms of HCQ retinopathy or positive indications of retinopathy in OCT imaging or VF testing.

Fifty-four eyes were successfully tested in 26 of the 30 study subjects. Of the eyes tested, 36 (67%) passed and 18 (33%) failed the DA test. Of the subjects tested, 40% showed at least one abnormal DA time. Of those eyes passing the test, 5 eyes (9% of the cohort) showed a “late normal” DA time between 6.0 and 6.4 minutes. There was no significant correlation with DA time for daily dosage, cumulative dosage, patient age or duration of HCQ treatment.

Conclusion: The high number of subjects with abnormal DA times was quite unexpected, given the absence of visual symptomology or objective abnormalities on OCT and VF testing. These results suggest that DA may provide a more sensitive biomarker for ocular changes due to HCQ than conventional OCT and VF testing. However, we do not know how specific this test is for retinopathy, i.e., whether those abnormal delays will precede changes on ocular coherence tomography, visual fields, or the onset of visual disturbances in patients with continued exposure to HCQ. This pilot study therefore warrants a larger cohort, longitudinal study to establish the specificity of dark adaptometry prior to its acceptance as a screening test to improve the safety of treatment with HCQ.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/dark-adaptometry-screening-for-hydroxychloroquine-retinopathy-a-pilot-study/