Don:I get contact lenses to replace my glasses and it’s like I’m seeing the world through new eyes. It’s miraculous!

 

Yaël: Acutlly, Don, there is nothing miraculous about it.

 

D: Who tell?

 

Y: Well, like glasses, contact lenses work by bending light rays just the right amount to make the object come into focus on the retina at the back of the eye. Sometimes the eye’s natural lens has an imperfection or may not be shaped properly, which can make your vision blurry or distorted. Depending on your vision, the right kind of lens helps your eye focus light properly and project a clear image onto the retina.

 

D: Ok, fine. But why do contact lenses make things seem so clear?

 

Y: Patience, younger princess! Glasses have what’s called an optical center, which means that objects appear clearest when viewed through the center of the lenses. But when you’re wearing glasses and you move your eyes to the side, or up, or down, things can seem slightly distorted or blurry.

 

D: So because contacts are right on the eye and move with the eye, there’s no optical center.

 

Y: Right! To put it another way, the entire contact lens is the optical center. So no matter which way you move your eyes, objects appear in perfect focus.

 

Don:终于摆脱框架眼镜了，从隐形眼镜看世界，感觉是全新的！真是太神奇了！

 

Yaël:Don,事实上，这是你的错觉。

 

D:你怎么知道？

 

Y:和框架眼镜原理一样，隐形眼镜调节适量的光线进入眼睛，在眼睛后的视网膜上聚焦成像。有时候，眼睛晶状体老化或不完善都将造成视力模糊或扭曲。适合你视力的隐形眼镜纠正视力，辅助眼睛屈光，在视网膜上清楚成像。

 

D:好吧，那么你能说说为什么戴隐形眼镜看东西更清楚吗？

 

Y:别急呀，老兄！框架眼镜的镜片上有光心，当视野正好穿过，看到的图像最清楚。但是，当你戴框架眼镜，上下左右转动眼珠，看到的东西就略显模糊或扭曲。

 

D:所以，因为隐形眼镜直接接触眼珠，跟随眼珠转动，就不存在光心了。

 

Y:就是这样，或者你把整个隐形眼镜都看作光心，无论你怎么转动眼珠，视野正好透过光心。