I visited Karl McDonagh's exhibition of old photos during Carlow Arts Festival recently, and was struck by the eyes.In every one of the hundreds of pictures the eyes were sharp and looking straight at the camera. Now, those photos were photo-journalism, and mostly posed, and looking at them you can almost hear the photographer asking the people to look at the camera, and so you would expect eyes to be sharp and looking. But this is the point. Instinctively, if there are eyes in an image, whether human or animal, that is the first place we focus on, so that we can tell if they are going to attack us, or we should be attacking them, or whether we or they should be suitably submissive to avoid getting trounced. Because of our instinctive focus on the eyes, we should ensure that they are sharp, and for greater effect have them on one of the thirds of the image.
If your picture has eyes, they should be sharp.