Bilateral Optic Neuritis/inflammation and swelling of the left optic disc; severe optic disc swelling with vessel obscuration bilaterally/bilateral disc edema; peripapillary hemorrhages on the left; Visual acuity decreased; no light perception in the left eye; decreased vision in the left eye; left APD; blurring of disc margins in the left eye; bilateral reversible optic neuropathy; mild pallor of both optic discs/mild optic atrophy; This case was reported in a literature article and described the occurrence of bilateral optic neuritis in a 6-year-old female patient who received Flu Seasonal QIV Dresden (Influenza vaccine Quadrivalent unspecified season) for prophylaxis.  On an unknown date, the patient received Influenza vaccine Quadrivalent unspecified season (intramuscular). On an unknown date, 1 week after receiving Influenza vaccine Quadrivalent unspecified season, the patient experienced bilateral optic neuritis (serious criteria hospitalization and GSK medically significant), optic disc engorgement (serious criteria hospitalization and GSK medically significant), peripapillary hemorrhage (serious criteria hospitalization and GSK medically significant), visual acuity decreased (serious criteria hospitalization), no light perception (serious criteria GSK medically significant), vision decreased, marcus gunn pupil, blurred vision, optic neuropathy (serious criteria GSK medically significant) and optic atrophy (serious criteria GSK medically significant). The patient was treated with prednisolone and methylprednisolone. On an unknown date, the outcome of the bilateral optic neuritis, optic disc engorgement, peripapillary hemorrhage, no light perception, vision decreased, marcus gunn pupil, blurred vision, optic neuropathy and optic atrophy were unknown and the outcome of the visual acuity decreased was recovered/resolved.   The reporter considered the bilateral optic neuritis, optic disc engorgement, peripapillary hemorrhage, visual acuity decreased, no light perception, vision decreased, marcus gunn pupil, blurred vision, optic neuropathy and optic atrophy to be related to Influenza vaccine Quadrivalent unspecified season.  Additional details were provided as follows: This case was reported in a literature article and described the occurrence of bilateral optic neuritis and bilateral reversible optic neuropathy in 6-year-old female patient who was vaccinated with unspecified quadrivalent (inactivated) influenza vaccine (manufacturer unknown) for prophylaxis.  Previously, the patient was healthy. There was no family history of autoimmune, ocular, or neurologic disorders. Our patient had no previous medical problems. No information on patient's concomitant condition was provided. On unspecified date, the patient had received intramuscularly unspecified quadrivalent (inactivated) influenza vaccine (administration route and site unspecified, dosage unknown; batch number not provided). The age of vaccination was not provided. However it could be 5 or 6 year at the time of vaccination. [In this case, the patient's identical twin received the same vaccination without subsequent changes in vision and other adverse effects]. On an unspecified date, 1 week after vaccination, the patient presented to the emergency department, her visual acuities were hand motion in the right eye and counting fingers in the left with no afferent pupillary defect (APD). Examination revealed severe optic disc swelling with vessel obscuration bilaterally and peripapillary hemorrhages on the left. There were no anterior chamber cells, vitreous cells, or macular exudates in either eye. Magnetic resonance imaging (MRI) of the brain, orbits, and spinal cord with and without intravenous (IV) contrast showed increased T2/FLAIR signal and abnormal enhancement in the retrobulbar optic nerves bilaterally ( i.e MRI with fat suppression and coronal T1 MRI with fat suppression sequences demonstrating enhancement and thickening of the retrobulbar optic nerves), but no white matter lesions in the brain or spinal cord (Axial T2 sequence showing the absence of white matter lesions white matter lesions). Cerebrospinal fluid analysis revealed 1,000 red blood cells/mL, 5 nucleated cells (WBC)/mL, protein level of 23 mg/dL, and glucose level of 58 mg/dL. There were no oligoclonal bands, positive cultures, Lyme antibodies, aquaporin- 4 antibodies, or evidence of any of the following by polymerase chain reaction in the CSF: Epstein-Barr virus, herpes simplex virus, and varicella-zoster virus. Serologic testing was also negative for culture growth, Lyme antibodies, aquaporin-4 antibodies; white blood cell count, erythrocyte sedimentation rate, C-reactive protein, and angiotensin-converting enzyme levels were normal. After 5 days of IV methylprednisolone, visual acuities improved to 20/20, and she recognized 10/10 Ishihara color plates with each eye. The patient was discharged to home without a steroid taper. Six days after her last dose of IV steroids, the patient experienced decreased vision in the left eye. Examination showed visual acuities of 20/25 in the right eye and no light perception in the left eye. There was a left APD. Ophthalmoscopy showed mild atrophy of the right optic disc from her initial inflammation and swelling of the left optic disc (Color fundus photograph of the right optic disc and left optic disc at time of recurrence of visual loss and presentation to the neuro-ophthalmology clinic. The photos show mild optic atrophy in the right eye and mild swelling with blurring of disc margins in the left eye). Optical coherence tomography (OCT) of the peripapillary retinal nerve fiber layer showed average thicknesses of 144 mm in the right eye and 203 mm in the left eye, consistent bilateral disc edema. Thus, the patient was diagnosed with bilateral reversible optic neuropathy. The patient started oral prednisolone 2 mg/kg/day; 2 weeks later, her visual acuities returned to 20/20 with normal color vision (14/14 Ishihara plates) in each eye. Optic disc swelling in the left eye had resolved, leaving mild pallor of both optic discs. The oral steroid dose was tapered over the subsequent 4 weeks without recurrence of vision loss. At her last follow-up evaluation (11 weeks after the influenza vaccination and 10 weeks after initial vision loss), neuro-ophthalmic examination was stable. To the best of our knowledge, she has remained without recurrence off steroids over the past 2 years. This case has been considered as serious due to hospitalization. The author commented, "Optic neuritis after influenza vaccination is a rare condition that results in severe vision loss typically reversible with prompt initiation of steroid therapy. The association and pathophysiology remain controversial. Although some authors have concluded that there is insufficient evidence to support a causal relationship between the influenza vaccine and optic neuritis, others have found the time course of symptom onset in the setting of a negative work-up for known causes of optic neuritis to be convincing support for an association. The aberrant immune response leading to postinfluenza vaccination optic neuritis may be facilitated by genetic susceptibility. The divergent reactions to the influenza vaccine in our patient and her identical twin suggest that the interplay between environmental exposures and genetic predisposition in postinfluenza vaccination optic neuritis may be more complicated and warrants further research".      Lab Comments: Lab test done on an unknown date . Magnetic resonance imaging (MRI) of the brain, orbits, and spinal cord with  and without intravenous (IV) contrast showed increased T2/FLAIR signal and abnormal enhancement in the retrobulbar optic nerves bilaterally ( i.e MRI with fat suppression and coronal T1 MRI with fat suppression sequences demonstrating enhancement and thickening of the retrobulbar optic nerves), but no white matter lesions in the brain or spinal cord (Axial T2 sequence showing the absence of white matter lesions white matter lesions). There were no oligoclonal bands, positive cultures, Lyme antibodies, aquaporin- 4 antibodies, or evidence of any of the following by polymerase chain reaction in the CSF: EpsteinBarr virus, herpes simplex virus, and varicella-zoster virus. Serologic testing was also negative for culture growth, Lyme antibodies, aquaporin-4 antibodies; white blood cell count, erythrocyte sedimentation rate, C-reactive protein, and angiotensin-converting enzyme levels were normal. Ophthalmoscopy showed mild atrophy of the right optic disc from her initial inflammation and swelling of the left optic disc (Color fundus photograph of the right optic disc and left optic disc at time of recurrence of visual loss and presentation to the neuro-ophthalmology clinic. The photos show mild optic atrophy in the right eye and mild swelling with blurring of disc margins in the left eye). Optical coherence tomography (OCT) of the peripapillary retinal nerve fiber layer showed average thicknesses of 144 mm in the right eye and 203 mm in the left eye, consistent bilateral disc edema. neuro-ophthalmic examination was stable.