What is the surface area of the vitreous humour in contact with aqueous humour?
Area=πr², d≈2cm (less than maximal d) -> r≈1cm,  thus the area in question is roughly 

3.14*1cm*1cm≈3.14cm²

UPD by request (ref):

The vitreous body base middle is at ora serrata (+-2mm), so we should calculate the area at this level. Here is the reference of the diameter:



from: Basic and Clinical Science Course, Section 02