Effect of digoxin on the sensitivity to flickering light

Area of Science:

• Ophthalmology
• Pharmacology
• Neuroscience

Background:

• Digoxin is a widely used cardiac glycoside for treating heart conditions.
• Visual disturbances are a known, though often underreported, side effect of digoxin toxicity.
• Quantifying visual system changes related to digoxin levels is crucial for patient safety.

Purpose of the Study:

• To investigate the relationship between plasma digoxin levels and visual sensitivity to flickering light.
• To evaluate the utility of the DeLange curve in assessing digoxin-induced visual toxicity.

Main Methods:

• Assessed flicker sensitivity across various light frequencies (DeLange curve) in 20 controls and 45 patients on maintenance digoxin.
• Measured flicker thresholds (percentage of maximal light modulation at 30 Hz).
• Correlated flicker thresholds with plasma digoxin concentrations (optimal, subtoxic, and toxic levels).

Main Results:

• Flicker thresholds were significantly elevated in patients with subtoxic and toxic digoxin levels compared to controls.
• A clear inverse correlation was observed between flicker sensitivity and plasma digoxin levels.
• Visual sensitivity returned to baseline upon discontinuation of digoxin therapy.

Conclusions:

• The DeLange curve is a sensitive indicator of visual system impairment due to digoxin.
• This method can help monitor for and quantify digitalis toxicity affecting vision.
• Early detection of visual side effects may improve patient management and outcomes.