Abnormal pupillary responses in myasthenia gravis. A pupillographic study

Area of Science:

• Ophthalmology
• Neurology
• Clinical Physiology

Background:

• Myasthenia gravis (MG) is an autoimmune disorder affecting neuromuscular junctions.
• Ocular muscle involvement is common in MG, but iris sphincter function is less studied.
• Pupillary light reflex is a sensitive indicator of autonomic and neuromuscular function.

Purpose of the Study:

• To investigate pupillary light responses in patients with myasthenia gravis.
• To assess the effect of edrophonium chloride on pupillary responses in MG.
• To determine if iris sphincter dysfunction is a feature of myasthenia gravis.

Main Methods:

• Infrared video pupillography used to record pupillary light response and derivative curves (velocity, acceleration).
• Stimulus: Open-loop, Maxwellian view.
• Measurements taken before and after intravenous edrophonium chloride (5 mg) in 7 MG patients and 3 controls.

Main Results:

• Myasthenia gravis patients exhibited reduced amplitude, maximal velocity, and maximal acceleration of pupillary constriction.
• Pupillary dilatation parameters showed minimal changes in MG patients.
• Edrophonium chloride improved abnormal pupillary values in most MG patients within five minutes.

Conclusions:

• Iris sphincter involvement appears common in myasthenia gravis.
• Analysis of pupillary reaction dynamics and derivative curves can detect this involvement.
• Pupillary response testing may serve as a diagnostic aid for myasthenia gravis.