I am often asked why it is that some mediums work with their eyes closed. You need to understand how mediums work first to understand why they close their eyes.
If a medium is clairvoyant, they will ’see’ what spirit is showing them. They do not see with their physical eyes though. They see with their psychic sight. What they see is subjective and not objective. Therefore, what they see is in their head. It is a bit like having a TV screen in your forehead.
A medium can learn to work with their eyes open with practice. It is difficult at first but can become second nature. When a medium is a novice they will find it easier to keep their eyes shut, so that nothing distracts them from the spirit communication. A novice is easier to distract as they are generally more nervous.
Usually you will find that when you have a private consultation with a medium, they will tend to close their eyes more often because they are working closely with you and spirit. It helps the concentration.
Clairaudients and clairsentients do not need to keep their eyes closed, as what they are getting is not seen. But, some may do so in order to keep their concentration. It is only like any normal person who is trying to concentrate on something.