We can describe our eyes as 'mince pies'.

What is the meaning of fthe sentece:

[color=red]we can describe our eyes as ‘mince pies.’

How is related to Christmas?

In’cockney rhyming slang’ ( a slang which developed around a particular area of London’, certain phrases are substituted for the usual words in a sort of ‘code’.
apples and pears = stairs
trouble and strife = wife
dog and bone = phone
So, for example, it would be possible to hear:
I was sitting on the apples and pears speaking to the trouble and strife on the dog and bone. (I was sitting on the stairs speaking to the wife on the phone)
This is a very simplistic form though. It becomes more complicated with substitutions of other slang terms (for example, ‘speaking’ could become ‘having a natter’), with the shortening of some of the rhyming slang phrases so that you cannot hear the rhyme and with the substitution of other popular (non rhyming slang) phrases for some of the rhyming slang. So as an example the sentence above could become something like this::
I rested my bum on the apples and pears having a natter with 'er indoors on the dog.

In rhyming slang
mince pies= eyes. (sometimes further shortened to ‘mincers’)

The rhyme is what was important in the evolution of the term, it was not specifically related to Christmas in that sense. The only thing that links the phrase to Christmas is that ‘mince pies’ are traditionally Christmas food in the UK.

Languages are each time more complicated, I hope this way of speaking will no create a new language.

The question is how popular Cockney rhymes are on a global scale.