Question

sometimes the heart sees something which is invisible to the eyes explain this line

Answer 1

It's natural that eyes can see but heart cannot but still there is something that the heart can feel and see also. "Love" is that pure emotion which heart can see it can see our emotions . It always helps us to take right decision by looking on our emotions. Heart is everything because it never gives you wrong results.

We can see the internal beauty of a person by our heart can see. Internal beauty is the first.

Answer 2

"Sometimes, the heart can see what the eyes cannot."
The literal meaning of this might be- Eyes can see everything, but hearts cannot. 
The meaning of this statement is that the heart can feel things that the eye cannot. Sure, eyes can see and hearts cannot, but hearts are able to feel the things that the eyes can see. For example, when we see a sad sight, sure, we may cry with our eyes, but those cries are from the heart. The heart has feelings. That is why we say, you touched my heart! This is because our heart has felt the emotion of what the person has said or done.