Spectacle Non-Tolerance: A Step-by-Step Troubleshooting Guide for Optometrists

Last updated: November 2026

RPC Rounds for Optometrists · B.Optom study guide

"I can't see with my new glasses" is the most common complaint in any optical practice. Most cases are solved by working through the same order every time: check the glasses, check the fit, check what changed from the old pair, and only then repeat the refraction.

Step 1: listen to the exact complaint

Step 2: check the glasses against the order

• Read both lenses on the lensometer: sphere, cylinder, axis, add, prism, and compare with the written prescription and tolerance standards.
• Check the material and design: was a different index, base curve or progressive design used compared with the old pair?
• Check the lens is not reversed (right in left) and that segment heights match.

Step 3: check the fitting

• Mark the optical centres and compare with the patient's pupils: horizontal (PD) and vertical (heights). Calculate the resulting prism with Prentice's rule and compare with tolerance (about 0.5–1Δ horizontal, less vertically).
• Check vertex distance (critical over ±4.00 D), pantoscopic tilt and face form; for progressives, check the fitting cross is at the pupil centre.
• Adjust the frame and re-check vision before changing anything else.

Step 4: compare with the old glasses

• Large changes in cylinder power or axis, a change from minus to plus cylinder grinding, or a change in base curve are the classic causes of distortion.
• Adults adapt slowly to new or larger cylinders: consider a partial cylinder, keep the old axis if the vision difference is small, or prescribe in steps.
• Keep the same base curve and lens form as the old pair when the patient was happy with it, especially in high powers.

Step 5: repeat the refraction

• Recheck with a fogging technique, the duochrome and binocular balance; look for overminus (the commonest error), unbalanced eyes and a wrong add.
• Trial-frame any change and let the patient walk around before reordering.
• Unexplained poor vision with correct glasses needs an eye examination for cataract, macular or optic nerve disease.

Adaptation

Some symptoms settle within about 1–2 weeks of full-time wear (new progressives, increased cylinder, first high-index pair). Tell the patient this at dispensing. Symptoms that persist beyond about 2 weeks, or double vision at any time, should be reviewed.

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Related: Lensometer (Focimeter) Step by Step: Single Vision, Prism, Bifocals and Progressive Lenses, Frame Selection and Spectacle Fitting: Boxing System, PD, Fitting Height, Tilt and Wrap, Spectacle Lens Designs: Aspheric, Bifocals and Progressive Lenses (Fitting and Troubleshooting), Subjective Refraction Step by Step: Fogging, Best Sphere, Cross-Cylinder, Binocular Balance and Near Add, Prentice's Rule: Induced Prism With Worked Examples. Back to the optometry curriculum.

Key sources

• Brooks CW, Borish IM. System for Ophthalmic Dispensing. 3rd ed. Butterworth-Heinemann; 2007
• Jalie M. Ophthalmic Lenses and Dispensing. 3rd ed. Butterworth-Heinemann; 2008
• Elliott DB. Clinical Procedures in Primary Eye Care. 5th ed. Elsevier; 2020