Some students who have a visual impairment will have a sensitivity to light. If this is the case they may wish to wear a hat that will help with reducing the glare of the light. It is also ideal to seat the child away from windows where bright light is likely to come through. If the reflection off the desk is an issue, try using a small cloth to cover the desk to keep the glare down. On the other hand some students may need more light to be able to see better. Having a table lamp is ideal to help them see better.
With either type of visually impaired student, it is ideal to use a blackboard with white or light colored chalk to make seeing the information easier. A whiteboard will have a glare that may make seeing the information difficult for your visually impaired student.