The mechanics of tear production and what can go wrong

There are several main contributors to dry eyes:

• Dysfunction of your meibomian glands (MGD) so that your tears have too little of the oily component that stops tear moisture from evaporating
• MGD is the most common reason for dry eyes. It accounts for 60 to 80% of dry eye conditions, depending on the age group surveyed
• Dysfunction of your lacrimal glands so that they produce too little of your aqueous tear moisture as is the case with sjogren's syndrome
• poor blink frequency, which affects the distribution of tears across your eyes.
• Often a problem when using computer screens but also can be caused by facial palsy stopping your eye(s) from blinking
• evaporative dry eye caused by environmental factors such as central heating or hot weather
• insufficient drainage through blocked ducts

You may have a combination of these factors though by far the most common is MGD (meibomian gland dysfunction).