Mr Chi is 76 years old and has requested an emergency appointment as his right eye is red and swollen. Mr Chi explains that four days ago he noticed a small, slightly tender, yellow swelling in his eyelid. He went to his local chemist who advised him it was a stye and to trial warm compresses. Over the last 24 hours, the pain has become more pronounced and the whole eye is red and swollen. Mr Chi wears glasses for reading but has no other significant ophthalmology history. He has Hypertension and pre-diabetes and does not smoke or drink alcohol. His only medication is Ramipril and he is allergic to Penicillin.
On examination, there is marked erythema and swelling of the right eye which is also tender on palpation. There is no proptosis, eye movements are normal and visual acuity is intact. Observations are within normal limits.
Given the likely diagnosis what is the most suitable treatment?