Fig. 2.

Schematic of custom diffractometer used to measure RI change attained with blue-IRIS. A He-Ne laser beam was incident upon the blue-IRIS phase gratings, causing the beam to diffract. A power detector was mounted to a swing-arm, and measured the diffraction pattern over a hemisphere ranging from $-20\mathrm{deg}$ to $+20\mathrm{deg}$, taking measurements at 0.125 deg intervals. Higher diffraction orders were seen, but RI change was calculated by assessing the first-order diffraction efficiency. The diffraction pattern was measured at three separate locations in each phase grating to account for small variations in intrinsic corneal background scatter.