Evaluation of changes in thickness of macular sublayers in patients using Hydroxychloroquine: a cross sectional case-control study and literature review.

Abstract

To assess changes in the thickness of macular sublayers in individuals taking hydroxychloroquine (HCQ) without any evident toxicity and to review the relevant literature. This prospective case-control study examined 47 adults on HCQ without evident toxicity on spectral-domain optical coherence tomography (SD-OCT) and visual field tests, as well as 25 healthy controls. Macular thickness in different sublayers was measured using SD-OCT. The thickness of combination layers and the variability of sublayers were also recorded. Data were compared between the case and control groups, and the correlation between cumulative HCQ use and outcome measures was analysed. The average age of participants in the case and control groups was 45.6 ± 9.3 and 46.8 ± 11.7 years, respectively (p = 0.831). The percentage of female participants was 91.5% in the case group and 84.0% in the control group (p = 0.927). In the case group, the average duration of HCQ use was 5.1 ± 5.2 years, with a mean cumulative dose of 301 ± 365 g. No significant differences were found in the visual field mean deviation or pattern standard deviation between patients with HCQ use of <5-years vs. ≥5-years. Additionally, there were no statistically significant differences in various retinal thickness measurements between the case and control groups. However, a significant association was observed between the cumulative dose of HCQ and the thickness of the outer retinal layer (ORL) in both the outer (r = 0.344; p = 0.032) and inner Early Treatment Diabetic Retinopathy Study (ETDRS) macular rings (r = 0.303; p = 0.061). No significant difference in macular sublayer thickness was found between patients taking HCQ without evident toxicity and the control group. A weak direct association was observed between the cumulative dose of HCQ and the ORL thickness. These findings suggest that analysing macular sublayer thickness may not be useful in detecting the earliest signs of presumed HCQ toxicity in individuals without classical sign of toxicity on qualitative SD-OCT or visual field test.