*4.3.3 Ferning test*

Tear ferning test is a simple test for tear film quality. This test requires capillary tubes, spatula, or glass rods to collect tear from the lower tear meniscus (about 5–20 μl). The collected tear is applied to a glass slide and evaluated under light or digital microscope with various magnifications (40-100x). In DED, the delicate fronded pattern becomes fragmented or broken up and irregular and the appearances can be graded into type I and II (healthy tear film) and type III and IV (increasing degrees of dry eye) [14, 60].
