Creating a true, realistic 3D eye is a difficult task. In this tutorial I'll share with you the results of my investigation into creating a perfect 3D eye. I've tried to keep it simple and easy to follow. Please have patience and pay attention to all of details. Let's begin.
The geometry you use for eye will be strongly effective. A 3D eyeball should consist of two or three parts: cornea, iris, and sclera (you can combine iris and sclera together in one piece). The geometry you need to consider isn't only for the eyeball, but it's all shapes and forms in and out around the eye as well, such as the inner corner, eyelids, eyelashes, wet layer, outer corner and even the eyebrow. So I recommend you start by taking care of the geometry. Below is a sample of the parts of the eye you'll have to create (Fig.01).
For the eyeball itself, I recommend you don't use a sphere primitive, because if you add either the
MeshSmooth or TurboSmooth modifier, then a bad deformation will appear and we don't want
Instead we want to use a Capsule primitive. So go to Create > Geometry > Extended primitives > Capsule and drag into the viewport to create a capsule like this (Fig.03 & Fig.04).