There are many measurements involved with the proper ordering and fitting of your eyeglass prescription. Proper function and fit of your prescription eyewear depends on correct optical measurements in the horizontal, the vertical, the rotational, the tilt, the distance from your eyes to the back of the spectacle lenses as well as your eyes’ explicit prescription.
Be very cautious about ordering your eyeglasses on line. You most likely will not end up with the desired result of comfortable vision and a properly fitted frame.
A skilled optician is necessary to take all your measurements in person, then place your order with the optical laboratory, and finally verify that the order was made correctly to all of your specifications. Without this proper fitting of your prescription, you most likely will not receive what you need for your eyes to see clearly and comfortably. Please do not rely on the “predictive technology” and “proprietary algorithms” that are advertised on the internet as sufficient methods to calculate your eyeglass prescription’s VERY PRECISE requirements and specifications!
A professional is always better to consult with when it comes to something as precious as your vision.