I feel like you may be conflating two terms here. Probably. :-) I could be wrong, but it sounds like you're discussing the size of the eyes in the input imag

I feel like you may be conflating two terms here. Probably. :-) I could be wrong, but it sounds like you're discussing the size of the eyes in the input image. I believe I am. I assume that increased pixel count in the eye region corresponds directly with increased accuracy. This could be accomplished by either moving the camera closer to the eye, or by using a higher resolution camera.