Answer:
Deep, deep, do they go. Spreading out as they go. Never needing any air. They are sometimes as fine as hair
You'll have to consult an optometrist if you want to improve this.
If you can get this professional's attention you can get where you need to go for a price.
They keep secrets locked away. And you pass through them each day. For each one there is a key, They respond to sesame.
What is filled with air and sometimes a gas, tied to a string and often seen on your birthday?
What is always coming but never arrives?