The diameter of the coloured contact lens is the width at the widest posible point of a lens (edge to edge). Many different lens diameters are available but most coloured contact lenses come as 14mm diameters which cover and look the natural size for most peoples iris. Most coloured contact lens manufacturers also make 15mm lenses which are generally sold as ‘Big Eye’, ‘Circle Eye’ or ‘Manga’ style lenses. Even though these lenses are only slightly bigger in diameter they can create a dramatic affect.
Base Curve (BC)
Coloured contact lens Base Curve refers to the inside curvature of a lens and should match your cornea to feel comfortable and allow for proper oxygen transmission. Although the actual number it self does not really mean anything to the wearer most contact lens are between 8 and 10. The larger the base curve the flatter the lens will appear. The smaller the base curve the more curved the lens will appear. The most common base curve produced by coloured contact lens manufacturers is 8.6 as this feels comfortable for most wearers.
If a lens feels loose and slides easily when worn then you should consider a lower base curve. If the lens feels tight when worn then a larger base curve would be advised.