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Charles Affel, Maria Pefkianaki, Priya Sharma, Allen Ho, Jason Hsu, Joseph Maguire, Carl D Regillo, Elizabeth Affel, Julia A Haller; Effect of Hydroxychloroquine Exposure and Toxicity on Dark Adaptation. Invest. Ophthalmol. Vis. Sci. 2017;58(8):225.
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© ARVO (1962-2015); The Authors (2016-present)
Hydroxychloroquine toxicity causes destruction of macular rods and cones, typically in a parafoveal fashion until late in the disease. Dark adaptometry was evaluated as a potential diagnostic tool for hydroxychloroquine toxicity (HCQ) as rod-mediated light sensitivity may be affected as a result of macular rod impairment.
Participants were recruited from the comprehensive ophthalmology and retina services of Wills Eye Hospital from 08/2015 to 05/2016. In this prospective study, patients were divided into four groups. Patients with known HCQ retinal toxicity based on clinical examination and abnormal screening diagnostic tests were placed into Group 1 while patients without known HCQ toxicity were placed into three groups based on their cumulative HCQ dosage (< 720 g into Group 2, 720-1460 g into Group 3, > 1460 g into Group 4). Spectral-domain optical coherence tomography (SD-OCT), 10-2 Humphrey visual fields (HVF), fundus autofluorescence (FAF) and dilated fundus examination were performed on all study patients. Dark adaptation was measured after pupil dilation using a computerized dark adaptometer (AdaptDx, MacuLogix, Hummelstown, PA, USA) with the Rapid Test algorithm in which rod mediated dark adaptation speed was measured in response to a 76% bleach stimulus located five degrees superior to the fovea. The speed of dark adaptation was expressed as the Rod Intercept (RI) time in minutes.
Thirty-one eyes of eighteen subjects were analyzed. The mean age was 33 years with the majority being female (94%). Twelve were African Americans (67%) and 6 were Caucasian (33%). There were three patients in Group 1, seven in Group 2, four in Group 3, and four in Group 4. Three out of 5 eyes with known HCQ retinal toxicity exhibited abnormal dark adaptation >6.5 min with mean time of the RI time at the first group 6.3 min (SD:0.3). There was non-significant difference, p = 0.09 between the HCQ dosage and RI time but this may be a Type II error, as we didn’t find significance because of a small sample size. No relationship was found between years of HCQ usage and the RI time (p=0.24).
HCQ retinal toxicity may lead to abnormal dark adaptation in some patients. Increased cumulative dosage may also impact dark adaptation time. Future larger studies will be necessary to validate whether dark adaptation speed could serve as another method to screen patients for HCQ toxicity.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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