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Neutralization is a method used by opticians to determine the power of an unknown lens by placing a neutralizing lens of known, opposite power against it. When the resulting combination of the two lenses shows no movement, or neutralization, the power of the unknown lens is confirmed to be equal and opposite to the known lens.
read more about neutralization in optometry ...The process relies on a visual effect called "motion." When an unknown lens is moved, the image seen through it appears to move in a specific direction. The neutralizing lens is placed against it until the image movement stops. For example, a +2.00 diopter lens is neutralized by a -2.00 diopter lens.
Neutralization is used to verify the power of an existing pair of glasses. This is needed when a patient does not have their prescription details, or when an optician needs to confirm the accuracy of a newly cut lens before dispensing it to the patient.
The direction of image movement seen during this test indicates the type of lens:
While neutralization is a manual method, modern optical labs use a focimeter (lensmeter) to measure lens power digitally. Neutralization remains a simple, accurate back-up test that requires minimal equipment.
It is accurate, but digital focimetry is typically faster and easier for very strong powers.
No, the technique is designed for rigid eyeglass lenses.
The apparent image movement is referred to as "motion."
If you've lost your written prescription, an optician can "neutralize" your current glasses using a manual lensmeter to find your power. Always have this verified by a doctor if you plan to order new glasses, as your actual vision needs may have changed.
College of Optometrists. Verifying a Prescription (college-optometrists.org). 2024.
ABDO. Manual Focimetry (abdo.org.uk). 2023.
Review of Optometry. Lab Standards (reviewofoptometry.com). 2024.
The Vision Council. Ophthalmic Dispensing Standards (thevisioncouncil.org). 2024.