Related Experiment Video
Updated: Jul 3, 2026
06:34
Using the Electroretinogram to Assess Function in the Rodent Retina and the Protective Effects of Remote Limb Ischemic Preconditioning
Published on: June 9, 2015
[Two cases of digitalis toxicity with reversible and severe decrease of visual acuity]
1Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
Nippon Ganka Gakkai Zasshi
|February 24, 2001
Summary
Digitalis toxicity can cause severe vision loss, including photophobia and reduced visual acuity. Electrophysiologic tests like the 30 Hz-flicker electroretinogram (ERG) can help detect this toxicity.
Area of Science:
- Ophthalmology
- Clinical Electrophysiology
- Pharmacology
Background:
- Digitalis toxicity can manifest with ocular symptoms such as photophobia and xanthopsia.
- Two male patients presented with symptoms indicative of digitalis toxicity.
Observation:
- Patients experienced significant, reversible reductions in visual acuity and developed binocular central scotomas.
- Electrophysiologic testing, including 30 Hz-flicker electroretinogram (ERG), single flash ERG, photopic ERG, and scotopic ERG, was performed.
Findings:
- Visual acuity improved significantly as digitalis blood levels normalized.
- Reduced amplitudes in 30 Hz-flicker ERG and photopic ERG indicated photoreceptor dysfunction, with cones more affected than rods.
Implications:
- The 30 Hz-flicker ERG is a practical tool for assessing digitalis toxicity, alongside electrocardiograms and digitalis blood levels.
- Severe visual dysfunction in patients undergoing digitalis therapy warrants consideration of toxicity.
Related Concept Videos
01:22Photoreceptors and Visual Pathways
At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category, whereas...
01:26Heart Failure Drugs: Inotropic Agents
Positive inotropic agents are commonly used as the first line of treatment for heart failure. One such agent is digoxin, derived from the genus Digitalis, which has been known for centuries but effectively utilized since 1785. However, these cardiac glycosides can have potentially toxic effects due to their mechanism of action, which involves inhibiting Na+/K+-ATPase and increasing contractility. Digoxin is absorbed orally and distributed in various tissues, including the CNS. It has a long...
01:30Vitamins
Vitamins, derived from the Latin word for life, are essential organic substances required in small quantities for optimal growth and overall well-being. Unlike other organic nutrients, vitamins don't act as sources of energy or building materials but rather facilitate these nutrients' utilization by the body. Vitamins are predominantly coenzymes, assisting enzymes in specific chemical actions, like the oxidation of glucose for energy involving B vitamins. Most vitamins are not produced in our...
01:00Drug Toxicity: Overview
Drug toxicity quantifies the harm a compound causes to an organism, varying by dose and potentially impacting whole systems or specific organs like the liver. Toxic reactions may arise from venomous insect or spider bites, with effects ranging from mild symptoms to severe outcomes such as brain damage or death. Common forms of acute poisoning include ethanol intoxication and overdose of pain or fever medications, with substances like GHB and heroin being particularly lethal at doses close to...
01:24Drug Toxicity: Dose-Dependent Reactions
Drug toxicities can be stratified into pharmacological, pathological, or genotoxic based on their mechanisms. The incidence and severity of these toxicities generally increase with the drug's concentration in the body and exposure time.Pharmacological toxicity is evident when the therapeutic effects of drugs overshoot into adverse reactions in a predictable, dose-dependent manner. Central nervous system (CNS) depression from barbiturates is a classic example, with effects escalating from...
01:30Drug toxicity: Drug–Drug Interaction
Drug–drug interactions can precipitate toxicity through multiple mechanisms. Absorption interactions alter how drugs enter the body, exemplified when ranitidine increases the absorption of basic drugs, while cholestyramine decreases the levels of propranolol. Protein binding interactions occur when drugs share the same binding sites on plasma proteins. Drugs like aspirin and warfarin, when bound in excess, can lead to increased free drug concentrations, enhancing the potential for...