Posting this to clarify an earlier post http://wp.me/p86PWf-bV about wet macular degeneration. Fell into the trap of thinking other people automatically understand what one means.
The grid shown in the earlier post is an example.
For the real thing download this http://www.mdfoundation.com.au/resources/1/amsler_grid.pdf
Print it out and put in on your fridge door.