Macular sensitivities measured by microperimetry in patients on hydroxychloroquine treatment

To examine retinal sensitivity in patients on hydroxychloroquine (HCQ) with no evidence of retinopathy.

Seventy patients on HCQ and 30 healthy control subjects were included prospectively. All subjects underwent complete ophthalmic examination including best corrected visual acuity, tonometry, colour vision testing, biomicroscopy of anterior segment, dilated fundoscopy, 10-2 visual field testing, and spectral domain optical coherence tomography. The patients and control subjects who met the inclusion criteria and had normal tests underwent microperimetry (MP) testing. First, all patients were compared with the control group. Secondly, patients were divided into three sets of groups based on (1) duration of use ≤5 years (DOU≤5) and >5 years (DOU>5), (2) daily dose ≤5 mg/kg/day (DD≤ 5) and >5 mg/kg/day (DD>5), and (3) a cumulative dose ≤1000 gr (CD≤ 1000) and >1000 gr (CD>1000), and these groups were compared to each other and to the control group. A correlation analysis was also performed between MP sensitivity and DOU, DD, and CD.

Seven patients on HCQ showing visual field abnormality were excluded which yielded 63 patients and 30 control subjects for the final analysis. We observed significant differences only in the central region but not in the paracentral or peripheral regions on MP in HCQ users. The median MP sensitivities in the central region were significantly lower in all the patients [84 (63-100) dB], and in subgroups of DOU >5 [84 (63-99) dB], DD >5 [82 (63-97) dB] and CD >1000 [82 (63-92) dB] when compared to controls [89.7 (83-98) dB]. A statistically significant correlation was found only between DD and MP sensitivity in the central region (r = -0.263; p = 0.02).

MP sensitivities in the central macula were significantly lower in patients taking HCQ for more than 5 years, at a daily dose more than 5 mg per day, and with a cumulative dose over 1000 gr. Further research investigating long-term follow-up changes in MP sensitivities is needed to determine cutoff values for early retinal toxicity.