Take into account, material shaders make or break the 'realism' in eye textures.  If you see a tremendous amount of variability between characters, look into the advanced Material Room and compare nodes.  Older characters might not render correctly under the latest Poser versions; vendors use different node techniques.

IMO, find a shader node arrangement that works well and apply it to your characters.  Don't hardwire yourselves to vendor shader nodes if they don't work your particular Poser version.  Although I use the DAZ Elite Eyelight textures, I always apply Snarley's EZSkin to improve the renders.