Okay, drawing eyes can be a real pain to get right, and when you get it wrong it can really ruin your day and your artwork. The key for me is the lighting and not over detailing.
My artwork is actually pretty messy and rough, how I get away with this is to sharpen areas of focus, so places the eye is naturally drawn to, and then blocking and filling the rest of the image with shapes and light. Take a look at this recent drawing of Star Trek Voyager's Seven of Nine that I posted to Instagram. Looks pretty cool, right? (even if I say so myself).
Taking a closer look, the artwork is actually pretty scratchy and scribbly.
So, like I said, the key to getting an eye right, for me, is the low blobby detail and the good blobby lighting. Looking at the above image what makes the eye 'pop' and seem real-ish (or your brain is telling you it's an eye for sure) is the way the shadows and lights reflect of the surface. When I draw eyes, genuinely, they look pants until I add that blob of white reflection in there. I got this technique from drawing comic books. If you look at an eye from a comic book character you need to create an image that can be quickly and easily identified by drawing the minimum amount of detail.
If you look at the above drawing of Dr McCoy that I did recently you can see the eye is a simple couple of black and white blobs. The principle is the same for when I draw more detailed artwork as with this drawing of Seven of Nine.
So, eyes come in pairs, and that's when things can get tricky. Get one eye perfect, get the other a bit wobbly, you end up with a GLARING mess. This is due to the eyes being a real focal point of an image.
One of the key things to note is the lighting and how the eye reacts to light. If you take a look at my Seven of Nine drawing you will notice that the left pupil (Seven of Nine point of view) is larger than the right pupil. This is not a mistake, that's how eyes work and it's an important fact to take this into account with eyes when drawing them.
When I plan a drawing one of the first things I will plan out is the lighting, for this I use the rules and girds from Photoshop. In the above image, I planned the lighting to start in the top right hand (your prospective) of the image. The grid really helps me stay on track and get the shadows and lights in the right place, and once I'm about halfway through the image I switch off the grids and go a freestyle.
Artwork ©Simon Breeze 2016