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Fitting height is the vertical measurement used when mounting progressive addition lenses (PALs) into a spectacle frame. It is measured from the center of the pupil down to the lowest point of the frame's lens groove. This measurement determines the vertical placement of the intermediate and near vision zones.
read more about fitting height in progressives ...Fitting height is necessary because it controls where the wearer's gaze falls across the lens. Progressive lenses have three zones, distance (top), intermediate (middle), and near (bottom). The height ensures the intermediate and near zones are positioned correctly for comfortable viewing.
The optician measures the fitting height while the patient wears the chosen frame. The optician marks the precise center of the pupil in relation to the frame. This measurement tells the lab where to place the lens's fitting cross (the main reference point for alignment).
An incorrect fitting height makes progressive lenses unusable. If the height is too low, the wearer must tilt their head back to find the reading area. If the height is too high, the reading area is blocked, leading to severe eye strain and distortion.
Accurate fitting height is important for your backup progressive glasses. Progressive lenses are complex, and misalignment causes extreme discomfort. Correct fitting height makes sure you get stable, functional vision the moment you switch from comfortable contacts to complex backup glasses.
No, OC height finds the center of the distance prescription. Fitting height finds the starting point for the progressive corridor.
Yes, the fitting height changes with every frame style because the shape and size of the lens opening are different.
No, the frame must be tall enough to accommodate the full length of the progressive corridor, which is determined by the fitting height.
When choosing frames for progressives, ensure the "B" measurement (vertical height) is at least 28-30mm. If the fitting height is too shallow, the reading portion of the lens will be cut off, making it impossible to see close-up objects clearly.
The Vision Council. Progressive Lens Design Standards (thevisioncouncil.org). 2024.
ABDO. Fitting Progressive Lenses (abdo.org.uk). 2023.
Review of Optometry. Troubleshooting Progressive Failures (reviewofoptometry.com). 2024.
College of Optometrists. Dispensing Multifocal Lenses (college-optometrists.org). 2024.