Idiopathic hypertrophic pachymeningitis is a rare fibrosing inflammatory disorder that causes thickening of the dura matter of the base of skull. We report a case of a 27 year-old man presented with this pathological form causing a visual decrease. The diagnosing is a dural matter biopsy and the main treatment is steroid and immunosuppressive therapy. Idiopathic hypertrophic pachymeningitis is a differential diagnosis of optic neuropathy.