Well, I stand corrected. There is a vertical adjustment screw. However, it is not labeled at all and does not tell you which direction to turn the screw to move the headlamp upward or downward. You don't need to remove the headlamp or need any special tools to make this adjustment. All you need is a regular #2 phillips screwdriver with a reach/length of about 4 inches. If you look just to the outside of the inner screw that holds the headlamp in place, you will see an opening where you can insert the screwdriver.
Hold the screwdriver in firmly and turn the screwdriver clockwise to move the headlamp downward or counterclockwise to move the headlamp upward.
I've attached a couple pictures below to help illustrate this.