The NFL has made an exception to rules limiting the use of tinted helmet shields, the crux of a new sponsorship agreement with Oakley's football division.

The four-year deal, announced Tuesday morning, allows NFL players to wear Oakley's "Prizm Clear" shield beginning this season. The equipment "has a slight color tint engineered to help optimize detail recognition in the football environment," according to the company.

The NFL's 2019 rulebook remains unchanged on the issue from previous years. It states that clear shields are "optional" equipment but that "tinted eye shields may be worn only after the league office is supplied with appropriate medical documentation and approval is subsequently granted."

The Prizm Clear will be an approved exception.