Phenol red thread test dry eye, true is

Ans. (a) Colour change on contact with tears to assess the volume of tearsRef: Yanoff 4/e, p. 277Phenol red thread test was developed by Hamano et al to obviate the disadvantages of Schirmer's test by eliminating the need for anesthesia.3 mm. of fine dye-impregnated 75mm cotton thread is placed in the lateral one-fifth of the inferior palpebral lid margin for 15 seconds, alkalinity changes its color bright orange to red from tear contact.