Dear Christina -
Employers are required by law to accommodate our Migraines. They don't get a choice. Do you have a Human Resources department? If so, I would speak to them first. Bring them a copy of this sharepost about the Americans with Disabilities Act and the accommodations they are required to make. If there isn't an HR department, you may need to bring it straight to your manager. You need to let them know that they have a legal duty to make it possible for you to perform your job, and your sunglasses make it possible to do that. You are not looking for special favors, but just to be able to do your job like anyone else. Find a time to talk when you don't have a migraine and are not upset, and be firm. If your employer is large enough to be covered by ADA (15 employees or more and all governmental entities), and they do not accommodate you, you can file a complaint with the EEOC.
Good luck!
- Megan