When you wear contact lens, your vision changes into a purplish tint that can be manipulated to read “invisible” markings. Contact lenses can be marked with a number or dots in the form of a circle. When viewed in the light these markings will glow and can tell you whether your contact lenses are inside out or not.
If your contact lenses are inside out, they will not fit properly on the curvature of your eye and can cause blurry vision. The wrong-way-round lenses can be uncomfortable, and feel like they are lightly scraping the eyeball.
Most soft and some GP and scleral contact lenses have reference markings to aid the lens fitter in inhibiting the rotation of the contact lens on the cornea. These markings can be in the form of circles or lines, and their size, position and shapes can vary. These markings, which are usually placed at 6 and 12 o’clock on the lens correspond to angular locations on the lens. The fitter can then determine the direction in which the lens will rotate based on its position relative to the reference marks. This is known as LARS (Left Subtract Right Add).
Some manufacturers of contact lens put laser markings onto their lenses to help determine if the lens is correctly oriented. These are usually small numbers like ‘123’, and can be seen on both clear and coloured contact lenses. Hold the lens up to the light and you will see the markings. If the numbers are reversed, the lens is the inside out.