In the following sentence, should I mention article 'the' in front of distribution?
Evidence shows that there is a huge difference in the distribution of these problems between high and low-middle income countries
Here it is talking about specific distribution i.e. visual impairment and blindness. Is it correct?
In this particular case, you would want to use the article "the" because you're talking about on specific distribution that you've calculated. If you were referring to any of the possible distributions without specifying which one, you might say "a distribution", but that's not the case here.
Omitting the article entirely in this case would be non-grammatical.
It means that there is a huge difference between how common these problems are in high-income countries, and how common they are in low-income countries. They aren't distributed equally.
You can't omit "the" before "distribution". That would mean the same thing, but would sound strange.
You haven't given us enough context to say what the problems are.
