Reduction of Congenital Nystagmus in a Patient after Smoking Cannabis

Abstract

Introduction: Smoking cannabis has been described to reduce acquired pendular nystagmus in MS, but its effect on congenital nystagmus is not known. Purpose: To report the effect of smoking cannabis in a case of congenital nystagmus. Methods: A 19-year-old male with congenital horizontal nystagmus presented to the clinic after smoking 10 mg of cannabis. He claimed that the main reason for smoking cannabis was to improve his vision. At the next clinic appointment, he had not smoked cannabis for 3weeks. Full ophthalmologic examination and eye movement recordings were performed at each visit. Results: Visual acuity improved by 3 logMar lines in the left eye and by 2 logMar lines in the right eye after smoking cannabis. The nystagmus intensities were reduced by 30% in primary position and 44%, 11%, 10% and 40% at 20-degree eccentricity to the right, left, elevation and depression, respectively, after smoking cannabis. Conclusion: Cannabis may be beneficial in the treatment of congenital idiopathic nystagmus (CIN). Further research to clarify the safety and efficacy of cannabis in patients with CIN, administered for example by capsules or spray, would be important.