Background: Progressive outer retinal necrosis (PORN) is a necrotizing chorioretinopathy caused by herpes simplex virus, varicella-zoster virus, or cytomegalovirus. Objective: To describe the clinical morphology of PORN presenting with asymmetrical isolated bilateral retrobulbar optic neuropathy. Method:The medical records of a 45-year-old human immunodeficiency virus infected patient presenting with bilateral visual loss at King Chulalongkorn Memorial Hospital were reviewed with respect for the privacy of patient. Result: Gradual visual loss progressed to no light perception in the right eye and 20/200 in the left eye within 1 month. The patient was initially diagnosed with retrobulbar optic neuritis in both eyes. The investigations included MRI, vitreous tapping, lumbar puncture, and serological testing. MRI elicited enhancement around both optic nerves, which suggested optic neuritis. Thereafter, multifocal areas of retinal necrosis developed with rapid progression and additional cutaneous zoster lesions were established. These findings led to a diagnosis of PORN. The patient was promptly treated with intravenous ganciclovir, anti-retroviral therapy, and vitrectomy with endophotocoagulation and silicone injection. Unfortunately, his visual prognosis in the left eye was still poor. Conclusion: PORN was uncommonly present with bilateral isolated optic neuropathy before retinal lesions developed. Retrobulbar optic neuropathy from herpetic infection in immunocompromised patients should be considered despite a normal fundus at initial presentation. Early diagnosis and prompt intervention may preserve vision. This case demonstrates the importance of careful physical examination and follow up of retinal lesions.