This is how you can vector an eye in Adobe Illustrator. You will first want to upload your photo to PhotoShop and then increase the contrast to highlight your picture better. Increasing the highlights is not a necessary step however. This is an intermediate process but the end result with be a cartoon looking eye on a real person. If you used this effect for the whole picture it would look very neat like your own cartoon character! If you only subtly vector the eye then you still have an edited look but not as cartoonish.