From the Guidelines
Before starting Plaquenil, a comprehensive eye examination, including visual acuity testing, visual fields, and retinal examination, should be performed to establish a baseline and rule out any pre-existing conditions that may be exacerbated by the medication. This recommendation is based on the most recent guidelines from the American College of Rheumatology, American Academy of Dermatology, Rheumatologic Dermatology Society, and American Academy of Ophthalmology, as outlined in their 2020 joint statement on hydroxychloroquine use with respect to retinal toxicity 1. The examination should include a dilated fundus exam and may also incorporate more specialized tests such as spectral domain optical coherence tomography (SD-OCT) to detect early signs of retinopathy.
Some key points to consider when performing the baseline examination include:
- The risk of retinal toxicity from hydroxychloroquine is <2% for usage up to 10 years at a daily dosage of ≤5 mg/kg/day actual body weight 1
- Annual screening with sensitive tests should begin no more than 5 years after treatment initiation, or sooner if there are major risk factors present 1
- The examination should be performed by an eye care provider who is familiar with the potential retinal toxicity associated with hydroxychloroquine therapy
In addition to the eye examination, patients should also have baseline kidney and liver function tests, as impaired function of these organs can increase the risk of toxicity. A complete blood count is also recommended to establish baseline values, as Plaquenil can rarely cause blood disorders. For patients with cardiac issues, an ECG may be appropriate to check for conduction abnormalities, as hydroxychloroquine can prolong the QT interval. These tests help establish baseline values for monitoring during treatment and identify any contraindications to therapy before medication initiation.
From the FDA Drug Label
Within the first year of starting hydroxychloroquine sulfate, a baseline ocular examination is recommended including best corrected distance visual acuity (BCVA), an automated threshold visual field (VF) of the central 10 degrees (with retesting if an abnormality is noted), and spectral domain ocular coherence tomography (SD-OCT)
The test that should be run before starting Plaquenil (hydroxychloroquine) includes a baseline ocular examination with:
- Best corrected distance visual acuity (BCVA)
- Automated threshold visual field (VF) of the central 10 degrees
- Spectral domain ocular coherence tomography (SD-OCT) 2
From the Research
Screening Tests for Hydroxychloroquine Toxicity
Before starting Plaquenil (hydroxychloroquine), it is essential to conduct screening tests to detect potential retinal toxicity. The following tests are recommended:
- Visual fields (10-2 white Swedish Interactive Threshold Algorithm pattern deviation plots) 3
- Spectral-domain optical coherence tomography (SD-OCT) 3, 4, 5, 6
- Multifocal electroretinography (mfERG) 3, 6
- Fundus autofluorescence (FAF) imaging 4, 7, 6
- Contrast sensitivity tests 7
Rationale for Screening Tests
These tests are necessary to detect early signs of hydroxychloroquine retinopathy, which can lead to severe and irreversible vision loss if left untreated. Studies have shown that SD-OCT and visual fields can detect abnormalities in patients with hydroxychloroquine toxicity, even in the absence of symptoms 3, 4, 5. Additionally, mfERG has been used as a reference test to divide patients into affected and unaffected groups 6.
Combination of Screening Tests
Using a combination of structural and functional tests, such as SD-OCT, visual fields, and contrast sensitivity tests, can provide useful information in detecting early retinal changes in patients using hydroxychloroquine 7. The combined use of these tests can help identify patients at risk of retinal toxicity and allow for early intervention to prevent vision loss.