I have an older friend that lives up in northern Illinois.  She was having
eye issues--always red, always 'leaking'.  The eye doctor would give her
something and it would go away, but after the medicine ran out it would come
right back.  This went on for months.  Finally one day he said to her--"have
you ever had your duct work cleaned?".  She said no.  He told her to get it
done.

She called someone in to clean the duct work (from a regular natural gas
heater furnace, and shared duct work with an air conditioner).  The company
cleaned the ducts and so long as she has them come in twice a year to clean
them, she has never been bothered by eye problems again!

Samala,
Renee