Blurring of vision immediately after a change in posture is common. It is because when u stand up suddenly all the blood goes to your legs due to gravity. It takes 5 to 15 seconds for your body to adjust. If it lasts beyond 20 seconds we have to check wether your blood pressure is dropping more than what it should while standing. You can avoid this by sitting in the bed for a minute before standing up. There is no need to worry.