Hi there. Extremely high temperature exposure such as that of a furnace for extended periods are proven to cause cataracts
at an early age. Complications such as dry eye
do happen in many individuals after prolonged exposure for a few years. Any particulate matter in the air emanating from the furnace and you are prone to foreign body injury
in the eye. It is recommended that you wear heat protective goggles that are generally provided in your line of work. Use lubricating eye drops as often as is possible to keep out particulate matter and to keep dry eye at bay.