Outcome measurements
The primary outcome was the mean difference in the fluorescein staining score under a
blue-light filter system in all interesting areas between the two groups. The distribution of fluorescein at each interesting area was graded from the video record independently by two blinded assessors. The degree of fluorescein stain was graded according to a study by Harvey RJ. et al.(9) which grade 0 was defined as no staining of fluorescein on the sinus cavity, grade 1 was partial staining of fluorescein (present on one wall of the sinus cavity), grade 2 was staining of fluorescein on two or more walls of the sinus cavity, and grade 3 was pooling of fluorescein in the sinus cavity.(Figure 1) 
The secondary outcomes included the mean differences in the staining score of
fluorescein under a blue-light filter system in each area and subgroup analysis according to the phenotype features, CRSwNP and CRSsNP, and the severity of the disease by the LM staging system.