Portraiture demands that your subject looks alive
If the eyes of your subject look dead you stand no chance of drawing your viewer into the picture. When doing portraits you must bring a light into the eyes. A few days ago I looked at ways to enhance the eyes. The use of catchlights is one of the more important of these techniques. Within moments of death the spark of life seems to leave the eyes. This is because the reflections that we call ‘catchlights’ disappear in dry eyes. So, it is important we capture the eyes looking moist and reflective. It is this moisture that brings life, a three dimensional look and a dynamic feel to the picture.
Here is an article about catchlights in more detail…
Definition: Catchlights; Catch Lights; Catch-lights;