Frames & Materials
Frame styles, materials, measurements, and standards.
Frame Measurements (Boxing System)
The Boxing System is the standard method for measuring frames.
Key Measurements:
- A (Eye Size) — Horizontal width of the lens opening.
- B (Vertical Size) — Vertical height of the lens opening.
- DBL (Bridge Size) — Distance between the two lenses at the narrowest point.
- ED (Effective Diameter) — Longest diagonal measurement of the lens opening.
- Temple Length — Length of the temple piece from hinge to tip.
Frame PD = A + DBL (also called Geometric Center Distance)
Minimum Blank Size (MBS) = ED + 2(decentration)
Decentration = (Frame PD - Patient PD) / 2
Frame Types and Materials
Full-Rim — Frame completely surrounds the lens. Most durable.
Semi-Rimless — Rim on top, nylon cord on bottom. Lightweight.
Rimless (Drill-Mount) — No frame around lenses. Requires polycarbonate or Trivex.
Metal Frames:
- Monel — Affordable, may cause nickel allergies
- Titanium — Lightweight, hypoallergenic, corrosion-resistant
- Beta Titanium — More flexible than pure titanium
- Memory Metal (Flexon) — Returns to original shape
Plastic Frames:
- Zyl (Cellulose Acetate) — Most common, easy to adjust with heat
- Propionate — Lightweight, hypoallergenic
- TR-90 (Grilamid) — Very flexible, popular for sports
Frame Adjustments and Fitting
Standard Fitting:
- Frame should sit level on the face
- Temples touch the ear at the mastoid bone
- Nosepads distribute weight evenly
- Vertex distance ~12-14mm
Common Adjustments:
- Pantoscopic Tilt — Bottom of lens closer to face. Standard: 8-12 degrees.
- Retroscopic Tilt — Top of lens closer to face. Rarely desired.
- Face Form (Wrap) — Curvature of the frame front.
Important: Heat plastic frames before adjusting. Never apply heat directly to lenses.