The main cause of dry eyes are inadequate tear production or quality due to such factors as aging, an injury or disorder, eye surgery, and exposure to dry air, smoke, or sunlight.
Certain medication, including some antihistamines, antidepressants, and blood-pressure drugs, may also cause dry eyes. Making an effort to blink more frequently and improving air moisture by using a humidifier can help reduce or reverse dryness. Other helpful steps including limiting exposure to air conditioning and smoke and using over-the-counter artificial tears. There’s some evidence that increasing the intake of omega-3 fatty acids might also help.
In rare cases, dry eyes can be caused by systemic diseases such as hyperthyroidism, sarcoidosis, and Sjogren’s syndrome. So it’s worth mentioning your symptoms to an eye doctor.
Source: ConsumerReports on Health August 2012