If you ever get up in front of an audience and say "I know it's an eye chart," your presentation is headed down the wrong course.
If I can't see (or have to strain) to figure out the story you are trying to tell, your message is being clouded out.
Do yourself a favor...when you build your next powerpoint slide, sit in a room, project it up on a screen, and see how it looks from the back of the room.
If you can't see everything clearly, take it out.
For more on effective powerpoint, see here and here and here and here