Phenol red test/ Methyl red thread test for dry eye, true is

Phenol Red Thread test is the test to detect dry eye severity. When in contact with tear film it changes its colour from white to yellow to red. Its main advantage over Schirmertest is: a)It is Less time consuming as compared to schirmer test(15 sec) b)Anaesthesia of cornea is not required c)On the contact of tear strip with the tear it turns red d)Can be done in children easily e)Reflex tearing is minimal f)Differentiates between aqueous deficient & non aqueous deficient eyes