Ok, I think I need some advice on this one...

I'm about to be offered a new job but before it is offered I've been asked to fill out an online health questionnaire.
Now, one of the questions is "how many days off have you had the past 2 years?" and there reference to self certified or medically certified or a box for additional notes.
Right, well, I've had numerous operations in the past two years (3 months off for 2 retinal detachment ops and 5 weeks of for a serious eye infection which I was admitted over) which, without context, would make my sick leave days look REALLY bad. Plus some odd flu bouts here and there (nothing unusual really).
Ok. So I guess what I'm looking for here is whether I should be stating either only self certified, medically certified or both? Obviously medical certs are trackable via my GP (which they ask details for) but what about self certs with my current employer?
I don't want to lie AT ALL but I don't want to shot myself in the foot at the same time. Is sick leave something that is asked within reference requests to an employer?
Ugh, awesome job about to be offered and I've now got a sinking feeling this is going to bite me in the arse.
Damned eye is a curse!