One of the problems often encountered by Parkinson's patients is that the brain doesn't translate visual information correctly. In other words, one can see a visual barrier, that isn't really there, often met when attempting to pass through a door way, or a narrow corridor. The message received by the brain is that there is an obstruction in the way, and not possible to pass through a doorway. As odd as this may sound, it is a common phenomena, and one that can be worked on and resolved.
The brain views the wall, and seeing this is a larger expanse than a door, confuses the two and sees the door as an obstacle, instead of realising it's a door and that one can walk straight through. By perseverance and walking through this "bogus" barrier, repetition being the key to success, one can re-train the brain and be able to pass through the doorway without problem. Looking through the door at an item and focusing on that, distracts the brain and one can move forward easier.
The brain can also play tricks when looking at different floor surfaces, such as a change from tiles to wooden floor or carpet. Again the brain can see this as an obstacle, but there are simple repetitive exercises that one can do at home to improve the situation.If you would like to learn about the various tricks and techniques to overcome this problem, take a look at Sherryl Klingelhofer's site who has vast experience in Parkinson's resources. Thank you Sherryl for sharing your very helpful advice and information.