If you have a bifocal lens, the line should sit at the lower eyelid. If you have a trifocal lens, the top line should sit at the bottom of the pupil.
If your eyeglasses appear level on your face but sit crooked when resting on a flat surface, this may mean that one of your ears is higher than the other. The temple arms should be bent to accommodate any differences in ear height. [2] X Research source
For wire frames, gently bend the arms with small pliers until they are straight. Put the glasses on and observe in the mirror to see if they are correct. Do not use wire cutters. You must use padded pliers or the frames will likely be damaged. For plastic frames, the plastic on the lower arm must be heated by a warm air source, such as a hair dryer, to make the plastic pliable. Slowly move the plastic upward with your hands until it is in the desired position. Be careful using the hair dryer as you could melt the plastic. Another way to bend plastic frames is to run them under hot water for 15 to 25 seconds before trying to make adjustments. The arm should become pliable enough to adjust, but be careful. The plastic can snap even when heated. [7] X Research source
For wire frames, this adjustment can be made with pliers, or even your bare hands. For plastic frames, you will need to make the plastic pliable using either heated water or air, before bending the earpiece section of the frames.
Take care not to over tighten the screws, or you risk damaging the plastic or metal that they are holding in place.
On a side note, it is suggested that you get your eyes checked at least on a yearly basis to make sure the prescription in your lenses is still ideal for your vision.
