​Lens index determines the thickness and weight of the lenses. Materials like CR-39, polycarbonate, and high-index plastics serve different vision needs. Choosing the right combination ensures both comfort and clarity.

​Accurate specs measurements are essential for ordering glasses online. Common measurements include pupillary distance (PD), frame width, and temple length. Most sites offer tools or guides to help you measure at home with ease.

​Progressive lenses have invisible zones for distance, intermediate, and near vision. Marking and charting help opticians align these zones accurately to your eyes. Proper alignment is key for seamless, distortion-free vision at all ranges.