Dispensing Procedures
Frame fitting, verification, troubleshooting, and patient communication.
Frame Selection and Fitting
Frame Selection by Face Shape:
- Oval Face — Most versatile; most frame shapes work well.
- Round Face — Angular or rectangular frames add definition and contrast.
- Square Face — Round or oval frames soften angular features.
- Heart-Shaped Face — Frames wider at the bottom balance a broader forehead. Rimless or light frames work well.
- Oblong Face — Deep frames or decorative temples add width and break up length.
General Frame Selection Guidelines:
- The frame should not extend beyond the widest part of the face.
- The top of the frame should follow the brow line.
- Eyes should be centered in the lens openings.
- The frame should be proportional to the face size.
Frame Fit Criteria:
- Bridge: Should sit comfortably on the nose without sliding or pinching.
- Temples: Should follow the contour of the head and curve behind the ear at the mastoid bone.
- Vertex Distance: Approximately 12-14mm from the back of the lens to the cornea.
- Pantoscopic Tilt: Standard 8-12 degrees (bottom of lens closer to face).
- Weight: Distributed evenly between nose and ears.
Considerations for High Prescriptions:
- High Minus: Choose smaller frames to reduce edge thickness. High-index materials recommended.
- High Plus: Choose smaller frames to reduce center thickness and weight. Consider aspheric designs.
- The frame PD should be as close to the patient PD as possible to minimize decentration.
Taking Measurements
Pupillary Distance (PD):
- Measure distance PD for distance lenses.
- Near PD = Distance PD minus 3mm (due to convergence).
- Monocular PDs are more accurate than binocular.
- Use a pupillometer for best accuracy.
Segment Height (for Multifocals):
- Bifocal: Measure from the lowest point of the lens in the frame to the patient's lower lid margin.
- Progressive (PAL): Measure from the lowest point of the lens to the center of the pupil (fitting cross position).
- Always measure with the frame properly adjusted on the patient's face.
- Patient should be looking straight ahead at a distance target.
Fitting Cross (Progressives):
- The fitting cross should align with the center of the pupil.
- Each progressive design has a minimum fitting height (typically 14-18mm).
- The frame B measurement must accommodate this minimum.
Pantoscopic Tilt Adjustment:
- For every 2 degrees of pantoscopic tilt, add 1mm to the seg height.
- This compensates for the lens position relative to the eye.
OC Height (Single Vision):
- For dress eyewear: Typically at pupil center.
- For safety eyewear: May be specified differently per ANSI Z87.1.
Vertex Distance:
- Measure with a distometer or estimate.
- Critical for prescriptions over ±4.00 D.
- Record on the order if different from standard (12-14mm).
Verifying Finished Eyewear
Verification Checklist:
1. Confirm the order — Check patient name and prescription.
2. Lens power — Verify sphere, cylinder, and axis on the lensometer.
3. Add power — Verify through the bifocal segment or progressive near zone.
4. Prism — Check for prescribed prism or unwanted prism at the PRP.
5. Optical center position — Mark and verify OC placement matches ordered PD.
6. Segment position — Check seg height and horizontal placement.
7. Lens material and treatments — Verify correct material, coatings (AR, scratch-resistant, UV).
8. Cosmetic inspection — Check for scratches, waves, bubbles, coating defects in the central 30mm zone.
9. Frame alignment — Ensure frame sits level, temples touch evenly.
ANSI Z80.1 Tolerances (Key Values):
| Parameter | Tolerance |
|---|---|
| Sphere power (0 to ±6.50 D) | ±0.13 D |
| Sphere power (above ±6.50 D) | ±0.15 D |
| Cylinder axis (above 1.50 D) | ±2° |
| Cylinder axis (0.75 to 1.50 D) | ±3° |
| Add power (up to +4.00 D) | ±0.12 D |
| Seg height | ±1.0mm |
| Horizontal prism | ±0.33Δ |
Impact Resistance:
- All dress lenses must pass the FDA drop-ball test.
- 5/8-inch steel ball dropped from 50 inches.
- Safety lenses (Z87.1) have stricter requirements.
Troubleshooting Common Complaints
Headaches:
- Check PD and OC placement (most common cause).
- Verify prescription accuracy on the lensometer.
- Check vertex distance (especially for high Rx).
- Assess frame fit and pantoscopic tilt.
Dizziness or Swim (especially with Progressives):
- Normal adaptation period is 1-2 weeks.
- Verify fitting height, PD, and pantoscopic tilt.
- Check that the progressive corridor is not tilted (axis alignment).
- Consider a different progressive design with a wider corridor.
Blurry Vision at Distance:
- Verify distance power on lensometer.
- Check vertex distance (especially for high Rx).
- Ensure patient is looking through the distance zone (not the near zone).
Blurry Vision at Near:
- Verify add power.
- Check seg height — may be too low (patient can't find the reading zone).
- For progressives, ensure the near zone is accessible.
Objects Appear Tilted or Slanted:
- Check cylinder axis accuracy on the lensometer.
- Even small axis errors on higher cylinders cause significant distortion.
Frame Sliding Down:
- Tighten temples behind ears.
- Adjust nosepads inward (adjustable pad frames).
- Consider a frame with a different bridge style.
One Lens Closer to Eye Than the Other:
- Adjust face form or temple alignment.
- Check for uneven pantoscopic tilt.
Image Jump (Bifocals):
- Normal with flat-top bifocals when eyes cross the seg line.
- Progressive lenses eliminate image jump.
- Round seg bifocals have more image jump than flat-top.
Patient Communication and Education
Explaining Prescriptions:
- Use simple language: "nearsighted" instead of "myopic."
- Explain what each part of the Rx means for their daily vision.
- Relate lens recommendations to the patient's specific activities and needs.
Recommending Lens Options:
- Ask about lifestyle: computer use, driving, sports, reading habits.
- Explain benefits in practical terms: "AR coating reduces glare for night driving."
- Present options at different price points without pressuring.
- Always explain why certain materials are recommended (e.g., polycarbonate for safety).
Setting Expectations:
- First-time progressive wearers need adaptation time (1-2 weeks).
- Explain how to use progressives: point your nose at what you want to see.
- High prescription changes may require adaptation.
- Photochromic lenses won't darken fully in a car.
Care Instructions:
- Rinse lenses with water before wiping to remove debris.
- Use lens-safe cleaning solution and microfiber cloth.
- Store in a case when not wearing.
- Never clean lenses dry — this causes scratches.
- Don't leave glasses in a hot car (can damage coatings and warp plastic frames).
Professional Ethics:
- Never diagnose or suggest medical conditions.
- Refer patients to their eye doctor for any medical concerns.
- Maintain patient privacy (HIPAA compliance).
- Be honest about lens limitations and options.
- Document all measurements and dispensing decisions.