I was bitten by a tick 2 weeks ago and had head and facial swelling, i went onto antibiotics and since then my eyesight has improved daily. why is this?

Blepharitis: It is possible that you nay have had some concurrent eyelid disease (ie blepharitis). Oral antibiotics can improve the lid disease and secondarily the vision.

See below: I am assume that you contracted lyme disease. If so, early disseminated disease can present with cranial nerve palsies. These can include the abducens nerve that controls part of the movement of the eye. If this was affected, it could affect your vision. Also, many other ocular manifestations have been reported like: conjunctivitis, keratitis, iridocyclitis, and optic neuropathy. So, tx helps.