How to contact lenses?

Contact lens positive and negative distinction methods include appearance method, extrusion method, lighting method, etc.

1, appearance method

put the lens on the finger, if the edge of the buckle like a bowl is positive upward, if spread out like a dish is reverse upward.

2, extrusion method

put the lens between the index finger and thumb extrusion, positive inward closure, more elastic, and the reverse outward expansion, no elasticity.

3, lighting method

facing the mirror, the glasses and eyes to maintain a vertical direction. You can clearly see the reflective highlights on the lens when the positive upward, the lens edge rounded oval. In the reverse upward, the lens inner edge sharp and white.