Aims: To characterise the ocular motility features of chronic progressive external opthalmoplegia by quantitative and semiquantitative means. To assess the prevalence of diplopia and the binocular adaptations to nonaligned visual axes.
Method: We studied 25 patients with chronic progressive external ophthalmoplegia. In each case muscle biopsies were consistent with mitochondrial myopathy. All patients underwent cover test in the primary position, assessment of binocular status, and measurement of uniocular fields of fixation using the Goldmann perimeter.
Results: A total of 23 (92%) patients had an exo-deviation, with six (26%) of those having an associated vertical deviation: 12 patients were binocular. Of the 13 patients with a manifest deviation seven had diplopia and six had suppression. Of all paired extra-ocular muscles (EOM), 68% had symmetry of movement within 5 degrees of each other.
Conclusion: Almost all patients had an exo-deviation. Diplopia was more common than expected. The majority of patients had symmetry of EOM limitation.