Hydroxychloroquine retinopathy tied to choroidal thinning
Eyes with hydroxychloroquine (HCQ) retinopathy show a significant decrease in total choroidal and choriocapillaris-equivalent thickness, suggesting that choroid may be a possible site for HCQ toxicity, according to a study.
“These findings will broaden our understanding on ocular toxicity of HCQ and clinical evaluation for the toxicity,” said a team of investigators from the Hanyang University College of Medicine in Seoul, Korea.
The investigators conducted a retrospective case series including 124 patients with systemic lupus erythematosus (79.8 percent) or rheumatoid arthritis (20.2 percent) who received treatment with HCQ (mean age 42.4 years; 91.9 percent female; mean refractive error, -2.15 dioptres; mean duration of HCQ use, 8 years). Twenty patients (16.1 percent) had HCQ retinopathy. [Am J Ophthal 2017;183:56–64]
Swept-source optical coherence tomography measurement data revealed that compared with eyes of controls, those of patients with HCQ retinopathy had significantly decreased choroidal thickness (p<0.05), except at the temporal choroid 1.5 mm from the fovea.
Likewise, choriocapillaris-equivalent thickness was significantly decreased in all choroidal locations in the HCQ retinopathy vs control group. The medium-to-large vessel layer thickness, on the other hand, was only significantly different between the two groups at the following locations: subfovea, and 0.5 and 3 mm nasal from the centre of the fovea.
Cumulative HCQ dose/body weight notably correlated with subfoveal choroidal and choriocapillaris-equivalent thicknesses (p=0.001 for both). The association between the presence of HCQ retinopathy and choroidal thicknesses remained significant (p=0.001 for subfoveal choroidal thickness; p=0.003 for choriocapillaris-equivalent thickness) even after adjusting for age, diagnosis for and duration of HCQ use, and refractive errors.
Noting that there might be two explanations for the choroidal thinning in patients with HCQ retinopathy—HCQ retinopathy itself and duration of HCQ use (longer duration in patients with retinopathy)—the authors performed an additional analysis on choroidal thickness in the cohort of patients with a similar duration of HCQ use.
“Most of the measured points showed statistically significant differences in choroidal and choriocapillaris-equivalent thicknesses between the two groups. This result indicates that HCQ retinopathy, rather than the duration of HCQ use, might be associated with the choroidal thinning observed in our patients,” the authors said.
“[I]t is plausible to suspect choroidal involvement in the development of HCQ retinopathy… As melanin may play a contributory role in the development of HCQ retinopathy by concentrating the drug and thus prolonging toxic effects, the choroid, which is rich in melanin pigment, may be vulnerable to HCQ toxicity,” they added.
Given that HCQ retinopathy is irreversible, the authors underscored proper screening for retinal toxicity in patients with rheumatic or inflammatory diseases who are receiving the said medication.
The American Academy of Ophthalmology cited in its recommendations that the goal of screening for HCQ retinopathy is not to discontinue the valuable drug in the presence of borderline abnormalities, but to recognize definitive signs of toxicity at an early enough stage to prevent vision loss. [Ophthalmology 2016;123:1386-1394]
“Despite our results regarding the association between HCQ retinopathy and choroidal thinning, the clinical application of choroidal evaluation for the detection of HCQ retinopathy is questionable; therefore, further studies are required to confirm its usefulness,” the authors pointed out, adding that interpretations of choroidal thinning should take into consideration factors affecting choroidal thickness, such as topographical variation of the thickness, refractive error, diurnal variation and age.