Ophthalmology Phenol red test/ Methyl red thread test for dry eye, true is A Need instillation of anesthesia before doing the test B Need a ph meter to interpret C Color changes if there is mucin deficiency D Color changes from white to red on contact with tear film and is used to measure the dryness status of eye 💡 Explanation Phenol red test/ Methyl red thread test for dry eye, true is ✓ Correct Answer: D. Color changes from white to red on contact with tear film and is used to measure the dryness status of eye