An unusual presentation of convergence insufficiency in a patient with Parkinson's disease stimulated by deep brain stimulation.

Purpose: To report convergence insufficiency in a patient with Parkinson's' disease stimulated by turning on the deep brain stimulator. Observations: 72-year-old male with Parkinson's disease and hypertension presenting for the evaluation of blurry vision at near and mid distance that started after activation of an implanted Deep brain stimulator.Baseline ophthalmologic evaluation prior to deep brain stimulator implantation surgery and with the deep brain stimulator turned off demonstrated a full motility, centered eyes for distance and near and a best corrected visual acuity of 20/20, normal pupil exam, confrontational visual fields and dilated fundus exam. Following this examination, the Deep brain stimulator was turned on and re-evaluation few minutes later demonstrated the same findings except for a 6-prism diopter exotropia at near consistent with convergence insufficiency.Following our evaluation a set of +3 diopters base-in prisms were added to near glasses with total relief of symptoms. The patient did not require surgical adjustment of the deep brain stimulator leads. Conclusions and importance: Given the therapeutic effects of deep brain stimulation on convergence insufficiency reported in several studies, in addition to the influence of deep brain stimulation as Parkinson's Disease treatment in areas possibly associated with vergence control, convergence insufficiency secondary to deep brain stimulation does not seem very unlikely, although not often reported. Further studies are needed to optimize deep brain stimulation surgery to maximize benefits and limit adverse events, as well as being aware of convergence insufficiency as a possible cause for visual disturbance.