Diagnosis

Tests and procedures that may be used to determine the cause of your dry eyes include:

• A comprehensive eye exam. An eye exam that includes a complete history of your overall health and your eye health can help your doctor diagnose the cause of your dry eyes.

• A test to measure the volume of your tears. Your doctor may measure your tear production using the Schirmer test. In this test, blotting strips of paper are placed under your lower eyelids. After five minutes your doctor measures the amount of strip soaked by your tears.

  Another option for measuring tear volume is the phenol red thread test. In this test, a thread filled with pH-sensitive dye (tears change the dye color) is placed over the lower eyelid, wetted with tears for 15 seconds and then measured for tear volume.

• A test to determine the quality of your tears. Other tests use special dyes in eyedrops to determine the surface condition of your eyes. Your doctor looks for staining patterns on the corneas and measures how long it takes before your tears evaporate.
• A tear osmolarity test. This type of test measures the composition of particles and water in your tears. With dry eye disease, there will be less water in your eyes.
• Tear samples to look for markers of dry eye disease, including elevated matrix metalloproteinase-9 or decreased lactoferrin.