Background In recent years there has been increasing concerns about the long-term ocular toxicity of hydroxychloroquine which has resulted in increased vigilance of the use of a maximum of 5 mg/kg/day. The aim of this study was to determine the long-term ocular safety of the use of hydroxychloroquine in patients with cSLE.

Methods The SLE Clinic database at SickKids hospital was searched for all patients followed since its inception in 1985 diagnosed and followed who were treated with hydroxychloroquine. Follow-up data was obtained into adulthood by reviewing the records of patients following transfer to care at an adult SLE clinic. While treated at SickKids all patients were treated with hydroxychloroquine at a dose 5.5-6 mg/kg/day (maximum 400 mg/day).

However, following the recent recommendations for lower dosing of hydroxychloroquine, some of the patients had their dose lowered while followed in adulthood. All patients had regular hydroxychloroquine ophthalmologic follow-up at recommended intervals of 6-12 months. Exclusion criteria were: cSLE not diagnosed at SickKids Hospital, <2 follow visits, no documentation of ophthalmology follow-up or no documentation of hydroxychloroquine dose. This study was approved at local ethics boards at all participating centers.

Results A total of 718 patients with cSLE diagnosed until the end of 2019 were found in the SickKids Clinic database. 15 were not diagnosed with cSLE at SickKids or had <2 follow-up visits; 4 were eliminated as the hydroxychloroquine was stopped within one month for systemic side-effects. The study cohort there consisted of 699 patients who were followed for a total of 5815.5 person years. The mean follow-up time was 8.33 years (SD 6.15 years) (minimum 0.2 years and maximum of 35.9 years). 456/699 (65%) had ≥ 5year follow-up, 218 (31%) ≥ 10 years; and 41(6%) ≥ 20 years. During the follow-up time one patient stopped hydroxychloroquine for deposition in the retina without visual changes. A second patient had hydroxychloroquine stopped based on an optometrist’s examination but when reviewed by an ophthalmologist, no retinal changes were noted.

Conclusions In this long-term follow-up study of patients with cSLE treated hydroxychloroquine at a dose of 5.5-6.0 mg/kg/day (maximum 400 mg/day) there was no evidence of visual changes after long-term follow-up of 5815.5 person years (patients followed for up to 35.9 years). We suggest that, unlike the potential for ocular toxicity of hydroxychloroquine found it studies of adult at doses > 5mg/kg/day, patients with cSLE can be treated with 6 mg/kg/day prior to transfer to adult care.