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.
Colour change on contact with tears to assess the volume of tears
Uses a pH meter for measurement and interpretation
Measures ocular surface mucin deficiency if thread colour changes to blue
Requires instillation of topical anesthesia before the procedure
Errors of Refraction