Early retinal electrophysiology changes in quinine overdose

Area of Science:

• Ophthalmology
• Toxicology
• Neuroscience

Background:

• Quinine overdose can lead to significant visual disturbances.
• Electrophysiological assessments are crucial for understanding retinal toxicity.

Purpose of the Study:

• To document the serial electrophysiological and imaging findings in two patients after quinine overdose.
• To elucidate the early and subsequent retinal changes following quinine toxicity.

Main Methods:

• Serial assessments including visual acuity, fundus autofluorescence, spectral-domain optical coherence tomography (OCT), and full-field electroretinogram (ffERG).
• Evaluations were conducted between 2 and 47 days post-ingestion in two patients.

Main Results:

• Patients experienced initial vision loss followed by rapid improvement. Early OCT showed macular hyperautofluorescence and inner retinal hyperreflectivity.
• Initial ffERG indicated cone system dysfunction affecting ON- and OFF-bipolar cells, while rod bipolar cells were spared.
• Retinal arteriolar narrowing and attenuated rod system ffERG function were observed between days 10-40.

Conclusions:

• Early quinine toxicity impacts the presynaptic cone bipolar cell junction.
• Subsequent findings include retinal arteriolar attenuation and the characteristic electronegative scotopic ffERG response.