UPDATE: Despite earlier reports from Guest Relations Cast Members stating that guests requesting alternative accommodations would be able to wear face shields in lieu of face masks (with some restrictions), Walt Disney World has issued clarification stating that all guests will still be required to wear standard face masks. You can find the full details here.
In a post earlier today, we were informed that guests who could not wear face masks who requested an alternative accommodation would be provided a face shield. While initially it was believed Disney would provide the face shields, guests must now bring their own if opting in. The face shield policy will go into effect tomorrow, July 14.
Walt Disney World is currently requiring face masks for all guests visiting the theme parks, but like Universal Orlando, Disney will soon allow guests to wear face shields if they are unable to wear the mask all day and request accommodation.

Guests with disabilities who are unable to wear a mask may wear a face shield. Further details, like whether they will need to visit Guest Relations for additional clearance (Universal uses a wristband system for guests who opt for face shields) is still unknown. Either a face mask or a face shield is required to be worn at all times in the park. Many Cast Members are already required to wear face masks and face shields.
Certain attractions will require guests to remove the face shield and put on a mask, but the guest may wear the face shield in the queue before boarding. Guests utilizing this accommodation should ask Guest Relations which attractions require a mask instead of a shield.
For more information about wearing a face mask at Disney, check out these articles: