In the Southern and Northern Dynasties Period (420-589), there was a painter called Zhang Sengyou. Once he visited a temple and painted on the wall four dragons, but gave none of them eyes. The onlookers felt that this was odd, and asked why he hadn't painted the eyes. He answered, 'Eyes are crucial for dragons. With the eyes painted on, the dragons would fly away.' Nobody believed this, so Zhang Sengyou took up his brush and added eyes to two of the dragons. No sooner had he finished than the two dragons flew into the sky amid a thunderstorm. The two without eyes stayed painted on the wall.
南北朝(公元420-589)时期，有个画家叫张僧繇。有一次，他到一个寺庙去游玩，在墙壁上面画了四条龙，可是都没有画出眼睛。看画的人觉得很奇怪，问他为什么不画出眼睛。他说：“眼睛是龙的关键，画上眼睛，龙就会飞走了。”大家不相信他说的话。张僧繇拿起笔来，刚给两条龙点上眼睛，立刻电闪雷鸣，两条龙飞向天空，墙上只剩下两条没有画眼睛的龙。
This idiom is used to describe how, when writing or speaking, one or two key sentences will enhance the contents.
“画龙点睛”这个成语用来比喻讲话或写文章时，在关键地方加一两句重要的话，使内容更加生动有力。