Thanks for replies - Yes the Rescue Centre informed my son that the Centre Vet had confirmed Herpes. Poor 'Obi' was in the Centre for over 8 months - nobody would take him because of the Herpes Eye - but my son always goes for the 'under-cat'!! He also took his sister 'Callie' who iwas very nervous and attached to Obi. She meticulously grooms him frequently - including his sore eye - so she probably has it too but it doesn't show in any way.

Thanks for the article link Selk67U2 - looked up the Omega Inteferon mentioned and it costs £279 - WOW!!!

The chloramphenicol looks interesting - I have always used that for eye infections in children - will look it up for cats and report back.
Thanks again all.