Shop.The iris is a contractile structure, consisting mainly of smooth muscle, surrounding the pupil.Light enters the eye through the pupil, and the iris regulates the amount of light by controlling the size of the pupil. If you make the liner too long, it will weigh the eye down when what we want is to open and lift it.' Tarte Double Take Liquid & Gel Vegan Eyeliner $25.00. Stop the liner just after your lashes do. Start applying the liquid liner at the highest point of your eye's curve, and drag outwards.