Hi
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Please do not use any steroid drops if there is corneal ulcer. This will worsen the ulcer. No antibiotic drop too should be added without a swab culture. Please consult an eye specialist.
Hope this helps. Please let me know if there is any thing else and do keep me posted. Take care!
DO NOT use the dexamethasone until you have the "ulcer" diagnosed. Steroids in the eyes can cause further damage unless used for a specific purpose.