A fixed fluence (100 J/cm
2) and irradiance (0.25 W/cm
2) were used to test variables that might affect the IOP
L. A higher RB concentration might increase bond strength because of greater light absorption (
Fig. 2) and more photocrosslinking sites. As shown in
Figure 4A, the IOP
L using 0.10% or 0.05% RB did not differ (
P > 0.05). The amnion surface in contact with the cornea might also have affected the IOP
L. RB was applied to the stromal surface of deepithelialized amnion, and either the stromal or the basement membrane surface was in contact with the deepithelialized cornea. The IOP
L did not differ (
Fig. 4B, second and third bars), indicating that RB applied to the stromal surface penetrates the basement membrane surface. When the epithelial layer was not removed, applying RB to the epithelial face and placing the epithelial face in contact with the cornea during irradiation produced an IOP
L that did not differ from the control (
Fig. 4B, fourth bar). Finally, RB-stained amnion was washed for 1 hour to remove loosely associated RB before irradiation. The IOP
L did not differ from the control IOP
L (
Fig. 4B, fifth bar), indicating that photoactivation of the tightly associated RB in the amnion was not sufficient to produce strong bonding. Further studies are required to assess the effect on photobonding of the known variation in amnion thickness and transparency.
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