Comparison of screening procedures in hydroxychloroquine toxicity

Area of Science:

• Ophthalmology
• Pharmacology
• Medical Imaging

Background:

• Hydroxychloroquine sulfate (Plaquenil) is widely prescribed for autoimmune conditions.
• Long-term use can lead to retinal toxicity, necessitating effective screening methods.
• Early detection of toxicity is crucial to prevent irreversible vision loss.

Purpose of the Study:

• To compare the efficacy of various screening procedures for hydroxychloroquine sulfate toxicity.
• To identify the earliest detectable signs of retinal damage at different stages.

Main Methods:

• Ten patients on long-term hydroxychloroquine therapy were evaluated.
• Methods included automated visual fields (10-2), multifocal electroretinography, spectral domain optical coherence tomography (SD-OCT), and fundus autofluorescence.

Main Results:

• All patients exhibited parafoveal visual field loss, sometimes subtle.
• Multifocal electroretinography showed parafoveal weakness in milder cases.
• SD-OCT revealed parafoveal thinning and loss of outer segment lines, progressing to outer nuclear layer thinning and RPE damage. Autofluorescence showed a parafoveal ring.

Conclusions:

• Overdosage appears to be a significant risk factor for hydroxychloroquine toxicity.
• SD-OCT detects early parafoveal outer segment line loss, often in the inferotemporal quadrant.
• Combined screening with multiple tests, including SD-OCT and visual fields with a low threshold, can identify toxicity before significant outer nuclear layer damage.