Extraocular muscle function in adult-onset Pompe disease tested by saccadic eye movements

- Histological findings imply extraocular muscle involvement in adult Pompe disease.
- We present accurate eye movement recordings by using infrared oculography.
- Saccadic parameters including peak velocity are comparable to healthy controls.
- We conclude that extraocular muscle function is preserved in Pompe disease.
- Data conform to clinical phenotype demonstrating unimpaired gaze control.

Glycogen storage disease type II (Pompe disease) affects mainly proximal skeletal muscles. Despite older histological evidence of extraocular muscle involvement, ocular motor palsies or other eye movement abnormalities are not considered part of the clinical picture.We investigated the dynamics of saccadic eye movements of five patients suffering from late-onset Pompe disease and compared their performance to that of age matched healthy controls. Horizontal rightward and leftward saccades were recorded binocularly, while subjects looked at LED targets placed at ±5°, 10° and 15° eccentricities.No differences in saccade amplitudes, peak velocities or durations were observed between controls and patients. More specifically, for 5° saccades, patients had a mean peak velocity of 146°/s with duration of 76 ms. For 10° and 15° saccades these values were 258°/s, 86 ms and 324°/s, 101 ms respectively, thereby lying well within one standard deviation of the mean of normal data. Moreover, saccadic amplitude accuracy was also unimpaired.These results indicate that patients with late onset Pompe disease perform fast and accurate horizontal saccades without evidence of muscle paresis or other ocular motor abnormalities. Reported histological abnormalities of extraocular muscles do not appear to have a phenotypic impact.