A blood vessel burst in President Reagan's left eye, causing it to partly fill with blood and appear red.
The condition was apparent during Reagan's speech-making appearance Friday before the National Space Club.
White House spokesman Larry Speakes said that Reagan noticed the condition when he awoke Thursday. "There's no pain. It doesn't affect his vision and there's no treatment," Speakes said, noting that the condition has occurred two or three times during Reagan's presidency.
Speakes said that the problem can be caused "by something as simple as a sneeze or exertion."