Chapter 3 of 4

Dispensing and Fitting

Frame Selection and Fitting

A proper fit balances the frame on the nose, brow, and ears without pressure marks. Nose pads control frame height; temples control retention behind the ears; endpieces control temple spread.

Move nose pads closer together to raise the frame; farther apart to lower it.

Adjust the temple bend to follow the ear contour and avoid pressure pain.

Spread the endpieces to relieve a frame that grips the sides of the head.

Key Measurements

Accurate PD, OC height, seg height, pantoscopic tilt, and wrap ensure the optics line up with the eyes. Misplaced measurements force awkward head postures or induce unwanted prism.

A too-wide PD induces base-out prism and eyestrain.

Pantoscopic tilt places the lower rim closer to the cheeks for downward gaze.

Excess wrap on strong Rx induces unwanted cylinder and prism unless compensated.

Lens and Frame Compatibility

Lens material, thickness, and mounting must match the frame and Rx. High-plus lenses suit smaller frames; high-minus benefit from high index; heavy or thick lenses are poor in large rimless mounts.

Smaller, well-centered frames reduce edge thickness (minus) and center thickness (plus).

High-index and aspheric designs reduce thickness, weight, and magnification.

Avoid very high-plus lenses in large rimless drill mounts.

Special Lens Types

Progressives give seamless multifocal power but have peripheral blur; bifocals show a visible line. High-index, polycarbonate, photochromic, AR, and polarized lenses each serve specific needs.

Progressive corridors need adequate frame depth or the reading zone is cut off.

Polycarbonate needs a scratch-resistant coating because its surface is soft.

Photochromics may not darken in a car because windshields block UV.

Troubleshooting Complaints

Patient complaints map to fitting or optical causes. Sliding frames, temple pain, tilted floors, and narrow reading zones each have a specific diagnostic adjustment or remake.

Seg line seen at distance means the segment is too high; lower it.

Tilted or sloping perception often reflects new cylinder power/axis and adapts over time.

Behind-the-ear pain calls for adjusting temple bend length and position.

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Last updated: November 2026

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