Retrobulbar optic neuritis is a rare complication of herpes zoster ophthalmicus (HZO). We report a case of a 27-year-old man who presented with a progressive left blurring of vision for one week. A history of vesicular rashes in the left trigeminal nerve area preceded his condition. On examination, we noted that his left eye visual acuity was hand movement, and his optic nerve function was reduced. Findings from examining the anterior segment and intraocular pressure were unremarkable. The fundus examination results were normal. A blood investigation was positive for human immunodeficiency virus (HIV). MRI showed hyperintense features of the intraorbital segment of the optic nerve in the T2-weighted image. An abnormal high signal on a T2 weighted image may be present, which may be a clue for varicella zoster associated complications, such as HZO-related optic neuritis. Therefore, a diagnosis of retrobulbar optic neuritis was made, and antiviral treatment was initiated. He received two weeks of IV acyclovir and switched to the oral route for one month. After the completion of the treatment, his visual acuity remained the same.