Just log in to your Zenni Optical account and click on Gift Card Status under My Account left navigation. Enter the gift card number and click Check. The amount left on the card will be displayed. NOTE: The gift card number will be encrypted for your security.
If you're new to Zenni and received the card as a gift, simply go to Login at the top of the page and create a new account with the email address that was entered as the recipient on the gift card order. Then go to Gift Card Status to see the balance.