Hello and welcome to healthcare magic Recurring optic neuritis in a child can be part of two demyelimating condition (which means nerve sheath destruction.The sheath called myelin protects and feeds the nerve).One is multiple sclerosis (MS) and other ADEM-on (acute dissiminated encephalomyelitis-optic neuritis). But MRI has to be abnormal for diagnosis of these conditions. So probably your child is suffering from a condition Recurrent Idiopathic Optic Neuritis as MRI is normal and no other system is involved. The recurrence depends upon previous dose of steroids.High enough dose of IV steroids prevents recurrence. The number one precaution is vigillent watching If other systems like sensation movement hearing and consious level is affected take him immediately to neurophysician to rule out Ms and ADEM-ON.If future attack occurs talk to your neurophysician about high dose IV steroids. Moreover gastrointestinal infections and chest infection can also trigger Recurrent Idiopathic Optic neuritis.So precautions can be practiced to avoid such infections like use of boiled water hand sanitation before eating and preparing meals after using toilet.Yearly influenza vaccination.Keeping Nose and throat moistened during cold and dry weather. Hope you find this answer helpful. Good luck!