Mustafa A Salih, Mohamed A Salih, Ali A Mustafa, Darren T Oystreck, Kamal M Attia, Sara M El-Sadig, Ahlam A Hamed, Waseem M Hajjar and Thomas M Bosley
Introduction: A variety of tests have been devised for the diagnosis of myasthenia gravis (MG). The best known
of these (Tensilon test, using intravenous edrophonium chloride) may cause serious complications (bradycardia and
syncope) dictating cardiac monitoring during the procedure. Ocular neostigmine drops, a simple procedure, may
significantly reduce the risk of diagnostic testing for possible MG.
Method: To investigate its efficacy, the miotic effect of neostigmine was explored using 30 rabbits. One drop of
sterile neostigmine solution (2.5 mg/ml) was instilled into the right eye (RE) of each rabbit using the left eye (LE), which
received sterile normal saline, as control. Serial assessments of pupillary size were done. One drop of neostimine was
instilled daily for 7 days to investigate its safety. Six patients (aged 4.5–55y, median=42y, mean=36.4y) with MG had
the same test and were observed for increase of the palpebral fissure height (documented by photography).
Results: At baseline there was no significant difference in the mean [SD] pupillary size of the rabbits between the
RE (7 mm [1.07]) and LE (7 mm [1.07]), p=0.63). Significant miotic effect was observed in the RE compared to the LE
at 30, 60 and 90 minutes (respectively, 4.8 mm [1.86] vs 7.0 mm [1.09], p=0.0001; 4.8 mm [1.86] vs 7.0 mm [1.09],
p=0.0001; and 3.2 [0.76] vs 7.0 [0.0], p=0.013). Administration of one drop of neostimine daily for 7 days caused no
ocular inflammation. All six patients with MG had an observable increase of the palpebral fissure height (documented
by photography) of at least 2 mm, 30 minutes after neostigmine instillation. The response was dramatic in the three
patients with no prior treatment for MG.
Conclusion: Ocular neostigmine drops is a safe, simple and efficient diagnostic test for MG.