Determining Whether A Soft Contact Lens is Inside Out
Due to the flexible nature of soft contact lenses, it is possible to invert them and put them in your eyes inside out. While this generally does not cause damage to the eye, it usually reduces the effectiveness of the contact lens and causes the lens to be very uncomfortable while in your eye. Therefore, before inserting soft contact lenses, it is important to be sure that they are turned the correct way.
In general, there are three methods to determine whether a lens is inside out or not.
The Wetting Method
Place the contact lens in the palm of your hand and allow it to air dry for several seconds. Then carefully place one or two drops of contact lens solution in the middle of each lens. If the lens is correctly inverted, the edges of the lens should fold inward.
The Taco Method
Allow the lens to air dry for several seconds after being placed on a fingertip. With your other hand, pinch the edges of the contact lens inwards. A correctly oriented lens's edges will bend inwards, like a taco. The edges of an inside-out lens will resist folding.
The Inspection Method
Place the lens on the end of a fingertip and hold it up so that you are looking at it directly from the side. Observe how the edges bend. An inside-out lens's edges will flare out slightly, whereas the edges of a correctly inverted lens will point straight upwards, like a bowl. Supposedly, the edges of an inside out lens will also look sharper, but I've never been able to see enough difference between states to notice this.