According to my knowledge in the field of optometry, my opinion is to use lenses with anti-fogging coat, which eliminate traces of fogg resulting from water vapor or patient's breath within few seconds

Air conditioner settings helps it . Still there is fogging, one may use DE-humidifier in OT.

Use the Miniature AVI Indirect lenses the 68º and the 130º the lens is sealed never get's foggy . It is a much clearer and safer view during vitrectomy.

If it takes two good surgeons to fix a sick eye don't try to do it alone , for your patient's sake.

Here are some tips:

• Ask assistant to press the drape over patient's nose to stop passage of air from patient to operating field. 
• Move the lens a bt away from the surface of the cornea (be aware that this reduces the field of view).
• anti-fogging coat doesn't help much and probably is not suited for repeated  sterilisation process

To stop passage of air, it can be put a mask over the patient's nose and fixed it on skin by sterile transdermal patch.

Nice fix, if this is the only cause, but temperature differences will always exist and condensation will fog non coated surfaces of PMMA.

Have a tight seal of drape around eye. Cut open drape near nostril and put hood over it. Keep lens slightly away from cornea 

lens away distorts the globe.

non contact is good for observation not for complex surgical maneuvers.

Try contact and compare for your own eyes.