I play tennis and I have a very difficult time seeing the ball clearly for
the entire path from where it is struck by the opposing player, to the point
where I should strike it.  The ball (your typical yellowish/greenish tennis
ball) disappears in any white background (e.g. the lines, the tape across
the top of the net, any opposing players white shirts, etc.).

Details:

This doesn't seem to be a focus problem but seems to be a contrast problem.
I've had my eyes checked lately and have corrective lens (-7.0 in both
eyes).

This problem occurs almost exclusively indoors under artificial lighting.
Yet there are occasions when it occurs outdoors: when it is very dark and
overcast or when I'm very fatigued.

I wear progressive lenses during the day and I play tennis in rigid gas
permeable contact lens.

I work in front of a computer all day.

The problem is less pronounced if I take a nap before playing.  Yet it gets
more pronounced as I fatigue though the match.  But don't misunderstand, my
endurance isn't bad -- I can play pretty hard for about 3hrs before my game
drops.  The vision problems occur much sooner than that.

Any ideas on what the problem is or how to deal with it?

Thanks.