Deoi3 means a pair of something
"ngo5 deoi5 ngaan5 hou2 sai3" is an idiomatic abbreviation. It actually means "(ngo5 ge1) (ni1 deoi5 ngaan5) (hou2 sai3)"
ngo5 ge1 = mine
ni1 deoi5 ngaan5 = this pair of eyes
hou2 sai3 = really small
Agree with Maksim.
In addition, you can say...
ngo5 deoi5 haai4 = my (pair of) shoes
ngo5 deoi5 haai4 hai6 bin1? (我對鞋係邊?)( Where is my shoes? )
ngo5 deoi5 faai3 zi2 = my (pair of) chopticks
ngo5 deoi5 mat6 = my (pair of) socks