We report a case of bilateral complete dislocation of lenses into the vitreous cavities due to elder abuse in a patient with senile dementia. According to the patient's son, bilateral complete lens dislocation occurred after he hit his father in the head with socks in order to control his violent behavior. Although the patient was taken to our ophthalmological ward for a planned vitrectomy, restlessness and inability to remain in his room during the night led to his leaving the hospital. The patient has not returned but did receive a vitrectomy at another clinic. While the number of patients with senile dementia has dramatically increased, no specific remedy is currently available. When treating medical concerns of seniors with unknown backgrounds, elder abuse needs to be considered as a potential cause of such injuries.