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Pupillary fatigue in myasthenia gravis
Transactions of the Ophthalmological Societies of the United Kingdom
|January 1, 1982
Summary
Patients with myasthenia gravis show a significant decrease in pupillary light reflex oscillation frequency. This suggests the pupillary reaction fatigues rapidly in myasthenia gravis, indicating potential neurological pathway involvement.
Area of Science:
- Ophthalmology
- Neuroscience
- Neurology
Background:
- Pupillary hippus, an oscillation in pupil size, is influenced by neuronal conduction rates.
- Myasthenia gravis is a neuromuscular disorder affecting voluntary muscle function.
Purpose of the Study:
- To investigate the pupillary light reflex and hippus frequency in patients with myasthenia gravis.
- To determine if the pupillary reaction fatigues differently in myasthenia gravis compared to healthy individuals.
Main Methods:
- Inducing sustained pupillary oscillation (hippus) by shining a narrow light beam on the pupillary margin.
- Measuring the frequency of hippus in twelve patients with myasthenia gravis and twelve control subjects.
- Analyzing the change in oscillation frequency (gradient) over time for both groups.
Main Results:
- Eleven out of twelve myasthenia gravis patients showed a gradual decrease in hippus frequency.
- Only one control subject exhibited a significant decline in oscillation rate.
- The mean gradient for controls was 0.0 +/- 0.4 cycles/min, versus -2.4 +/- 0.4 cycles/min for myasthenia gravis patients (p < 0.0001).
Conclusions:
- The pupillary light reflex fatigues significantly faster in patients with myasthenia gravis.
- This finding suggests impaired neuronal function or conduction pathways involved in pupillary control in myasthenia gravis.
- The pupillary hippus test may serve as a sensitive indicator for neuromuscular fatigue in myasthenia gravis.