Two people were standing right in front of the screen that some writing was projected onto. Some of the projected writing was on their back. With such close proximity they wouldn't be able to read it. It would be better if they were behind the projector.
Wolfe's eyesight issues vary widely. At one point he misses a small mark where a wedding band was on a ring. At another point he missed seeing a pen lying on the floor. Yet he spotted the specific style of burn marks on a suspect's arm and could read computer screens seemingly with ease.