Because of the slower spread in eyes with ATD, the resultant lipid film was found to be thicker on the inferior cornea than the superior cornea. This uneven distribution was clearly demonstrated when four different spots along the vertical meridian (i.e., 12 o’clock to 6 o’clock) were compared in each eye. As shown in
Table 2 , the thicknesses at spots A, B, C, and D were 74.1 ± 50.0, 84.7 ± 60.8, 105 ± 85.0, and 150 ± 83.6 nm, respectively, in all eyes. These thicknesses reflected an uneven distribution of the lipid film along this axis (
P = 0.01; the significance of the difference between spots A and D was
P < 0.01). Such an uneven distribution of the lipid film thickness was noted in 12 eyes with ATD with MGD as well as in 5 eyes with ATD without MGD
(Tables 1 3) . Nevertheless, the distribution of the lipid film became more uniform after PO, because the thicknesses at spots A, B, C, and D became 80.0 ± 17.3, 77.8 ± 19.9, 62.2 ± 17.2, and 87.8 ± 35.3 nm, respectively (
Table 4 ;
P = 0.2; compare
Fig. 3A with
Fig. 3B ). To illustrate these dramatic changes further, we measured the RGB color spectra in superior and inferior corneas and compared these spectra before and after PO. As shown in
Figure 4 , the distribution of RGB spectra was wide before PO (
Fig. 4 , left column), but became narrower after PO (
Fig. 4 , right column). Furthermore, there was a difference in the spectra distribution between superior and inferior corneas before PO (
Fig. 4 , left), whereas such a difference was not present after PO (
Fig. 4 , right).