01Purpose and principlesWhat the assessment is for and the core concepts behind it.
Retinal monitoring seeks toxicity before symptomatic visual loss. Hydroxychloroquine is useful for systemic disease, so an effective programme must both detect damage and avoid false diagnoses that remove a beneficial treatment. Routine spectacle checks, an apparently normal fundus and the patient's ability to read a chart do not replace the specified retinal tests. Conversely, an isolated abnormal scan can reflect another macular disorder or technical limitation rather than drug toxicity.
UK testing and interpretation use the Royal College of Ophthalmologists 2020 revision, with the 2025 British Society for Rheumatology guideline defining current referral timing and risk assessment. BSR specifies cumulative treatment exposure and earlier annual monitoring for higher-risk patients. The American Academy of Ophthalmology 2025 revision, published in 2026, advises an early baseline examination; this differs from the UK routine-baseline recommendation, so identify the applicable jurisdiction when planning care.
Key points
- The UK 2020 Royal College pathway uses OCT and fundus autofluorescence as the initial monitoring tests.
- The 2025 BSR guideline recommends annual monitoring after five equivalent continuous years for all hydroxychloroquine users.
- Higher-risk patients need annual monitoring after one year under the current BSR recommendation.
- Risk assessment includes adult dose above 5 mg/kg actual body weight, renal impairment such as eGFR below 60 mL/min/1.73 m², tamoxifen and prior chloroquine exposure.
- Routine baseline retinal testing for every new starter is not recommended by the UK 2020 pathway.
- One suspicious imaging result needs corroboration and should not automatically end treatment.
- Definite toxicity requires corresponding abnormalities on two appropriate tests and discussion with the prescribing clinician.
02Indications, selection and cautionsWhen it is useful, when urgency changes and important limitations.
Record the original start date, substantial interruptions, previous courses and previous chloroquine use. A new GP practice or a new rheumatology referral does not reset the exposure clock. BSR describes five years of equivalent continuous treatment, making a reconstructed prescribing history more useful than the latest prescription date.
Divide the daily prescribed milligrams by actual body weight in kilograms when assessing the adult 5 mg/kg risk threshold. For example, 400 mg daily in someone weighing 60 kg is approximately 6.7 mg/kg daily and merits prescriber review. This calculation identifies risk; it is not an instruction to change an effective prescription independently.
Renal impairment, such as eGFR below 60 mL/min/1.73 m², is a BSR higher-risk feature. Renal function and weight can change after treatment starts. Check tamoxifen and previous chloroquine exposure, reassess monitoring eligibility when risk changes and name the clinician arranging any earlier programme.
Ask about distorted print, gaps near fixation and difficulty with visual tasks, while recognising that early toxicity may be asymptomatic. Symptoms demand diagnostic assessment for toxicity and alternatives. Sudden monocular loss or pain should not be explained away as a typical slow medication effect.
Macular degeneration, inherited retinal disease or other retinal pathology can complicate interpretation. Inform the monitoring service about known disease and previous imaging. If coexisting pathology prevents reliable surveillance, the eye team and prescriber should discuss whether treatment and a meaningful monitoring strategy remain appropriate.
03Method and interpretationA systematic approach to the test and its findings.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Spectral-domain optical coherence tomographyFirst step - Why
- Assess outer retinal structure for a pattern compatible with toxicity.
- Interpretation and limitations
- The patient fixates while non-invasive scans sample retinal layers. Check scan quality and location before interpreting apparent loss. A structural abnormality may precede a reliable field defect; conversely, a single artefactual or unrelated abnormality is insufficient to declare definite drug toxicity.
- 02
Fundus autofluorescence, widefield where available - Why
- Map retinal pigment epithelial stress or loss across an appropriate retinal area.
- Interpretation and limitations
- Autofluorescence provides complementary distributional information rather than a photograph proving a drug cause. Widefield coverage helps assess more peripheral patterns. OCT and FAF findings should be considered together, with attention to whether they show anatomically corresponding abnormalities.
- 03
Automated 10-2 or 30-2 visual fields - Why
- Test functional correspondence when OCT or autofluorescence identifies a suspicious structural pattern.
- Interpretation and limitations
- Select the field strategy according to the abnormality's location, rather than applying 10-2 testing to every distribution. Explain fixation and response requirements, review reliability and repeat an uncertain result. Testing may require a separate visit from dilated imaging and subsequent virtual review.
- 04
Multifocal electroretinography - Why
- Seek objective functional corroboration when suspicious imaging lacks corresponding field evidence.
- Interpretation and limitations
- The UK pathway uses mfERG when confirmed structural abnormalities are not matched by an anatomically consistent defect on repeated visual fields. It is a specialist adjudication test, not routine screening for every patient. Continue medication while this uncertainty is resolved under the possible-toxicity pathway.
- 05
Clinical risk and prescribing review - Why
- Establish eligibility and interpret the retinal findings in the correct exposure context.
- Interpretation and limitations
- Current weight, actual dose, renal function, treatment duration, tamoxifen and prior chloroquine belong on the referral. Normal blood monitoring does not demonstrate retinal safety, and absence of a medication-related blood-test abnormality must not cancel retinal surveillance.
04Clinical next stepsHow the result changes management or prompts escalation.
01Entry to monitoringRefer at the appropriate exposure pointFirst stepHydroxychloroquine is being continued and eligibility for retinal surveillance is reviewed.+
- 1Reconstruct total treatment exposure and obtain the current actual weight, dose, renal function and relevant concurrent medicines.
- 2Arrange annual monitoring after five equivalent continuous years for patients without higher-risk features.
- 3Use the BSR recommendation for annual monitoring after one year when higher-risk features are present, including prior chloroquine use.
- 4Name the prescribing clinician responsible for referral and provide the patient with written information and a route for new symptoms.
02Possible toxicityResolve uncertainty before withdrawing treatmentOne structural test is suspicious without a second anatomically corresponding abnormal test; concordant OCT and autofluorescence abnormalities instead meet the definite-toxicity definition.+
- 1Ask the eye service to check whether findings are typical, reproducible and explained by another retinal disorder.
- 2Obtain the appropriate automated field test, repeating unreliable or inconclusive results as necessary.
- 3Arrange mfERG when one confirmed structural abnormality remains unsupported by repeated anatomically appropriate visual fields and the other imaging modality.
- 4Continue hydroxychloroquine during this possible-toxicity assessment, while communicating clearly with the prescriber and patient.
03Definite toxicityConnect a retinal diagnosis to a systemic treatment decisionTwo tests show corresponding abnormalities that fulfil the UK definition of definite retinopathy.+
- 1Communicate the diagnosis and severity to the patient, GP and clinician treating the systemic disease.
- 2Send a recommendation to stop hydroxychloroquine to the prescriber for discussion of risk, benefit and treatment alternatives.
- 3Document the agreed prescribing action; the monitoring ophthalmologist should not independently terminate systemic treatment.
- 4Address visual function, driving advice and low-vision support, distinguishing future clinical care from routine drug-monitoring invitations.
05Risks, monitoring and follow-upComplications, safety checks and further assessment.
- Confirm that the referral generated an appointment and that the result was returned; a sent referral alone does not establish that monitoring occurred.
- Review actual weight, dose and renal risk when the treatment plan changes and during systemic follow-up, communicating changes to the eye service.
- Ensure each report states no toxicity, possible toxicity or definite toxicity and gives a clear next test or action where needed.
- Transfer start dates and cumulative treatment history between services so eligibility is not postponed through administrative resets.
- When hydroxychloroquine is stopped, close routine drug monitoring in accordance with the UK pathway, while retaining ophthalmic care required for established retinopathy or other disease.
06Special situationsVariants, exceptions and circumstances that change the usual approach.
Baseline assessment is not a universal package
The UK recommendation against routine baseline retinal monitoring does not prohibit assessment of existing visual symptoms or known eye disease. A clinician may need an eye opinion for a specific problem before treatment. Explain that distinction when a patient encounters American advice recommending baseline OCT and FAF.
Correspondence matters more than counting
Two unrelated abnormalities do not automatically prove toxicity. The definite category requires a compatible pattern: OCT and FAF may correspond, or a structural test may match the field or mfERG abnormality. This protects against combining an incidental macular change with an unrelated unreliable field result.
Retinopathy is not reliably reversible
Monitoring aims to prevent avoidable exposure after toxicity is recognised, not to promise recovery after stopping treatment. Established severe disease can continue to progress. Give an individual prognosis and rehabilitation plan rather than implying that a prescription change instantly removes the patient's visual difficulties.
The risk threshold is not a cliff
An adult dose below 5 mg/kg does not guarantee absence of toxicity, particularly after prolonged exposure. A value above it does not prove retinal damage. Use the threshold to review prescribing and monitoring intensity while allowing retinal tests to answer the separate diagnostic question.
Chloroquine has its own timetable
The Royal College recommends annual monitoring after one year for chloroquine users. Do not apply the usual five-year hydroxychloroquine entry point to chloroquine, and do not omit previous chloroquine exposure when someone has subsequently changed treatment.
07Common pitfallsFrequent interpretation and management errors.
- 01
Waiting for a symptomatic bull's-eye maculopathy before arranging appropriate monitoring.
- 02
Using ideal body weight when applying the current adult BSR hydroxychloroquine dose-risk criterion.
- 03
Treating a normal visual acuity or ordinary optometry visit as equivalent to OCT and autofluorescence monitoring.
- 04
Stopping treatment because one unreliable field plot contains a defect without checking imaging and correspondence.
- 05
Repeating the entire monitoring clock after a service transfer or a new brand of the same medicine.