Also note that if eligibility cannot be determined online, you may need to contact Microsoft customer support and provide proof of your PC purchase.

FORBES: Get A Windows 8 Upgrade For $14.99

In most states contact lenses can be sold only with proof of a valid prescription--either a written prescription or oral approval from an ophthalmologist or an optometrist, who make their livings largely from the stuff they sell, contact lenses among them.

FORBES: An Eye For An Eye

Lacking so far is direct scientific proof that wearing ultraviolet-blocking contact lenses will prevent long-term eye issues.

WSJ: Contacts Lenses That Let In Sun, But Block UV Rays