You can simply add stickers to or even draw on the back of the chips to bring a personal touch to the expression of the eyes.
Please note that a chip should be placed with the flat side down. If an ordinary sticker is used, pay attention to the direction in which you apply the sticker.
To secure a chip in place, apply glue to the rim of the chip. Avoid damaging the paper with the pupil pattern on it while changing the chip.