A Review of Hydroxychloroquine Ocular Toxicity Save

Know-it-now

• HCQ retinopathy is common, with a prevalence reachin ~7.5% after 5 years and 20–50% after 20 years of use
• Most guidelines suggest limiting HCQ dosing at ≤5 mg/kg/day of actual body weight (AAO 2016; ACR/AAO 2020 Joint Statement). Exceeding this threshold is the leading modifiable risk factor for toxicity.
• HCQ retinopathy is irreversible and may continue to progress for years, even after HCQ is discontinued.
• Baseline ophthalmological assessment should occur within 12 months of HCQ initiation. Annual screening is recommended after 5 years, or from the outset in high-risk patients.
• High-risk patients require earlier and more frequent ophthalmological Exams - this includes those with: duration >5 years, cumulative dose >1,000 g, renal impairment (eGFR <60), concurrent tamoxifen use, and pre-existing macular or retinal disease.
• HCQ blood levels (therapeutic range 200–1,000 ng/mL) may be useful in dosing, detect non-adherence, and patients at highest retinal toxicity risk.
• Modern multimodal screening — combining 10-2 Humphrey visual fields, SD-OCT, fundus autofluorescence (FAF), and mfERG — detects early pre-symptomatic retinopathy. Older methods (fundoscopy, Amsler grid, and full-field ERG are insufficient)
• Asian patients show a distinctive pericentral (rather than parafoveal) pattern of retinal toxicity — the 10-2 visual field test will miss this; the 24-2 protocol (or wide-field OCT) must be added to the screening protocol for this population.
• Rheumatologists should document HCQ dose in mg/kg at every clinical encounter
• If ocular toxicity is detected, HCQ should be discontinued promptly. 

While hydroxychloroquine (HCQ) is thought to be a very safe drug, its ocular risk profile is probably more serious than appreciated.  A comprehensive review published in the Journal of Rheumatology discusses HCQ pharmacokinetics, mechanisms of retinal toxicity, risk stratification, and evidence-based screening protocols and how the drug can be used and monitored. 

Pharmacokinetics and Ocular Toxicity - HCQ is a weak base with high tissue affinity and extremely slow elimination kinetics — whole-body half-life is estimated at 40–50 days. A depot effect means that toxic retinal concentrations can accumulate silently over years and, critically, persist long after the drug is stopped. Drug exposure in the eye is therefore governed not by daily dose alone but by cumulative dose and duration of use.

HCQ retinopathy involves binding of HCQ to RPE melanin granules, leading to progressive RPE dysfunction and outer photoreceptor degeneration — particularly the parafoveal cone photoreceptors. By the time fundoscopic changes are apparent, significant irreversible functional loss has already occurred.

Monitoring HCQ blood concentrations has been proposed with a therapeutic window of 200–1,000 ng/mL. Levels above his are associated with elevated retinal toxicity risk. 

Prevalence -  Population-based analyses demonstrate a prevalence of approximately 7.5% in patients with more than 5 years of HCQ exposure, rising to 20–50% after 20 years. The marked discrepancy between historical and contemporary figures reflects different ascertainment methods (fundoscopy vs newer techniques).

Risk stratification is a prerequisite for tailoring screening intensity. The following factors independently and substantially increase retinopathy risk:

• Daily dose >5 mg/kg actual body weight: The dominant modifiable risk factor. Doses above this threshold — particularly at 6–7+ mg/kg — confer sharply elevated risk.
• Duration of use >5 years / cumulative dose >1,000 g: Risk increases steeply after the 5-year mark. At a standard 400 mg/day, a cumulative dose of 1,000 g is reached in approximately 7 years.
• Renal impairment (eGFR <60 mL/min): HCQ and its active metabolite desethylchloroquine undergo renal excretion; impaired clearance elevates plasma and tissue concentrations above expected levels for a given dose.
• Concurrent tamoxifen use: Tamoxifen is independently retinotoxic and exhibits synergistic toxicity with HCQ.
• Pre-existing macular or retinal disease: Underlying pathology impairs baseline imaging interpretation and may mask early toxicity changes; many authorities regard this as a relative contraindication to long-term HCQ.
• Older age and Asian ethnicity: Older patients have reduced retinal reserve; Asian patients exhibit a pericentral rather than parafoveal pattern of damage (discussed below) that requires modified screening protocols.

Screening: Current Recommendations

• Withing 12 mos of initiating HCQ - A baseline ophthalmological assessment — including visual acuity, visual field testing, and retinal imaging.
• Annual screening is recommended from the 5 year onward (or from the outset in any patient with high-risk features).
• Ophthalmologic examinations should be multimodal. No single test is sufficient in isolation:
  • 10-2 Humphrey Visual Field (HVF): Paracentral scotomas are often the earliest functional manifestation. The 10-2 protocol (testing the central 10 degrees) is mandatory; the 24-2 protocol should be added in Asian patients given the pericentral distribution of toxicity.
  • Spectral-Domain OCT (SD-OCT): The highest-yield structural test for pre-symptomatic disease. Parafoveal thinning and EZ disruption precede symptoms and fundoscopic change. Wide-field OCT adds sensitivity for pericentral patterns in Asian patients.
  • Fundus Autofluorescence (FAF): Detects areas of RPE metabolic dysfunction as hyper- or hypoautofluorescence; sensitive for active degeneration beyond the foveal region.
  • Multifocal Electroretinogram (mfERG): Provides objective, topographic mapping of macular cone function; particularly valuable in confirming equivocal findings on structural and perimetric testing.
  • Fundoscopy, Amsler grid, full-field ERG, and time-domain OCT are all insufficiently sensitive for early detection and should not be the primary screening tools.

**Asian patients - consistently show a pericentral (rather than parafoveal) distribution of retinopathy — changes cluster around the superior and inferior arcades, outside the central 10 degrees tested by the standard 10-2 protocol. Failure to employ 24-2 visual fields and wide-field OCT in this population results in systematically missed early toxicity. 

HCQ Retinopathy

When retinopathy is confirmed, HCQ must be discontinued. There is no pharmacological treatment. Progression can continue for months to years after cessation due to the drug's depot kinetics in RPE melanin — as illustrated in case reports documenting toxicity progression for up to 9 years post-discontinuation. The implications for long-standing lupus patients, in whom HCQ discontinuation carries documented risks of disease flare, renal relapse, and elevated cardiovascular mortality, underscore the importance of prevention over post-hoc management.

High-risk patients should be identified and flagged proactively, and co-management with ophthalmology — ideally via a dedicated HCQ monitoring pathway — should be established rather than left to ad hoc referral.

HCQ remains one of rheumatology's most valuable drugs — a safe and effective backbone therapy for lupus, RA, Sjogren's syndrome, and inflammatory arthritis. The ocular risk it carries is real, dose-dependent, cumulative, and irreversible once established — but it is largely preventable through strict adherence to weight-based dosing, accurate risk stratification, and consistent application of multimodal screening protocols. The paradigm has shifted: ocular toxicity monitoring is no longer an ophthalmologist's responsibility alone. It is a shared clinical obligation, initiated at the point of prescription.