It sounds like you have a vasovagal reaction when getting a procedure done at the dentist
office. A vasovagal reaction is when there is a strong stimulus such as pain, leading to syncope, which is fainting. You mention that you have blurry vision in the morning and also sometimes you get dizzy when standing. Vision could be blurry when you have orthostatic hypotension which is low blood pressures to the brain when you are getting up from a sitting or laying position. It sounds like you have your blood pressure measured and your glucose checked already. You didn't mention how long you have had this blurry vision for but the initial vasovagal reaction would not cause you to have permanent blurry vision. You should make an appointment with an optometrist
to have your vision checked. They could do more tests that is specific to the eyes that a medical office cannot perform. You should also follow up with your primary care doctor to let them know that your blurry vision is still present and to see if he/she wants to perform more tests or other lab work. In the meantime, you should not drive a car. Again, please speak with an optometrist or ophthalmologist.