Playing computer games too much does ________ to your eyes.(

do harm to 对.有伤害,do 的第三人陈单数形式 does
Playing computer games too much does （harm to ） your eyes.
玩电脑游戏太多对你的眼睛有害.
告诉你另外一种：
be harmful to 是有害的
Playing computer games too much are harmful to your eyes.‍
玩电脑游戏太多对你的眼睛有害.
玩电脑游戏太多对你的眼睛有害.

harm 填原型 does表示强调

do harm to 是个短语，意思是对.........有伤害，harm在此短语是个名词。题中应该填harm。
另有be harmfu to.....意思与上相同。