Where This Figure Comes From
White is the authority's word. 43x55mm is not.
Worth being straight about the evidence, because the UAE is a country where photo figures multiply. The ICP — the authority that issues the visa — lists the photo requirement as "a colored personal photo with a white background", and gives no dimensions at all.
For passports it does give one, and states it twice: a personal photo sized 3.5 x 4.5 cm with a white background. So the authority is capable of publishing a measurement; it simply has not published one for visas.
43 x 55mm is the figure in wide use for UAE visa applications and it is what this page produces. It is not traceable to the ICP. We have kept it rather than substituting a different unsourced number, but you should know which parts of this page rest on the authority and which rest on convention — the white background and the ICAO framing are the authority's, the millimetres are not.
If the post or typing centre handling your application publishes its own figure, use theirs.