Is it possible to contract hiv or any std from itching your eye?

Unlikely: Hiv is only transmitted by exposure to blood, usually through a break in the skin or in a mucous membrane during sexual contact.

Maybe, mabye not: It is theoretically possible to put enough std organisms of any type on the conjunctiva and create an infection. We occasionally see gonococcal infection, chlamydial infection, ppv infection. It could almost always be prevented by washing hands after any potentially infected/sexual contact before rubbing your eyes. Syphilis and HIV would be very hard to transfer to the eye this way, but might be.