The pupils typically remain dilated for about two to three hours, extending beyond the time of a diabetic eye exam. Dilation impairs eyesight by preventing the eyes from adjusting to bright light and a patient should decide whether to drive based on the effects experienced from pupil dilation and the driving conditions present after an exam. Clarkson Eyecare optometrists recommend that patients arrange for someone to drive them home or bring a pair of sunglasses to their appointment.