A sports frame with clear lenses, its front sweeping round in a deep curve.

Measuring and fitting

Wrap angle

Optical glossaryMeasuring and fitting

How much a frame curves around the face. High-wrap sports frames need designs compensated for it.

Three measurements of how a frame sits: vertex distance, the gap from lens to eye; pantoscopic tilt, how far the lens leans in at the bottom; and wrap, how far the frame curves round your face.

Illustrative · the shape of the principle, not measured data

In more depth

Seen from above, a frame's front may run straight across the face or curve around it. Wrap angle measures that curve. Everyday frames wrap a little; sports and sunglass frames can wrap a great deal, to follow the face and block light from the side.

A lens turned away from the line of sight delivers unwanted cylinder and prism, and the effect grows quickly with both wrap and prescription. Strongly wrapped frames therefore need steeper lenses and designs that compensate for the angle, and some prescriptions are simply too strong to wrap well.

Related terms

Base curveThe curvature of a lens's front surface. Must suit both the prescription and the frame's wrap.Pantoscopic tiltThe forward tilt of a frame relative to the face. Individualized designs account for it; standard designs assume an average.Vertex distanceThe gap between the back of the lens and your eye. At strong powers, a change in this distance changes the effective prescription.

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