Convergence spasm is defined by a triad of clinical signs: intermittent sustained convergence, accommodative spasm and miosis. To the unwary examiner this can mimic a range of ophthalmoplegic syndromes, most commonly abducens palsy or myasthenia gravis. Whilst it can be associated with organic disease (in brainstem and diencephalic lesions or metabolic encephalopathies), more often it is an expression of functional disease. Thus accurate diagnosis of this disorder may obviate the necessity for expensive and inappropriate investigations. Crucial to diagnosis is observation of pupillary constriction on attempted eye abduction. This can be difficult to appreciate under normal circumstances when pupillary constriction to light can complicate the clinical picture.
We would like to present three cases of convergence spasm for which diagnosis was confirmed using a novel diagnostic tool: infrared video goggles. These goggles, usually utilised in nystagmography, permit close-up recordings of eye movements, which may be played back to allow more accurate analysis. The infrared recording technique permits examination in low light conditions, thus removing the potentially misleading pupillary response to light. We suggest that the use of this technique will allow confident diagnosis of convergence spasm to be made earlier, thus avoiding unnecessary investigations and permitting earlier treatment.