Absolutely, you can do it yourself. At first, you need a mirror and a metri ruller. Relatively, with the help of your families, what you need to do is just to stand still there. The distance between the centers of your pupils is called pupillary distance and its typical range is between 57 and 65 mm. Second, look straight ahead and keep your shoulder relaxed. Now, one of your families can hold the ruler in front of your eyes, parallel to the floor, estimating the figure. Keep it in mind that your pupilary distance changes as the movement of your pupils. I mean, when you look close to read, your eyes will converge an average of three millimeters. So, it is important to ensure your eye level and focus on one point stably.