Lens centering for perfect vision
When fitting glasses, it's not just the thickness of the lenses that counts. The glasses also must fit correctly so that they optimally compensate for the poor eyesight. Everything you need to know about centering your glasses.
• What does lens centering mean?
When it comes to new glasses, more things are decisive than just the shape and color of the frame. To ensure the glasses correct the poor eyesight well, the optician determines the strength and, if necessary, other values, for example axis and cylinder in case of astigmatism or the addition in case of presbyopia. For the glasses to optimally correct the visual impairment, the lenses and frame must sit correctly on the nose. The optician determines certain centering data based on which the lenses are cut so that they are in the correct position in the frame. This is also known as lens centering. It's different for every frame and face. Eye or head movements, posture and the position of the eyes play an important role.
• This is how eyeglass centering works
Previously an optician centered glasses manually, marking directly on the lens in the frame where the pupils are and the distance between the eyes. Nowadays there are special measuring devices available, allowing for much higher precision. At Olympia Optics, we are using the latest technology from Zeiss, the VisuFit 1000.
It is the only device of its kind in Namibia.
• Precise digital 3D centration with 9 cameras for one-shot 180° view.
• Fast and easy measurements
The various values which are determined when the lens is centered are:
• Pupil distance: distance between the center of the pupils
• Wrap angle: How much the frame is bent towards the face
• Height: the point where an eye looks through the lens, measured from the bottom of the frame
• Corneal vertex distance: Distance between the front of the cornea and the back of the spectacle lens
• Inclination of the frame: inclination of the lens forwards
Lens centering is particularly challenging with multifocal lenses.
Blurred vision, headaches, dizziness - even if the prescription is correct, such asthenopic symptoms can occur if the glasses are not correctly centered. The centering of the lenses is precision work and must be carried out by a specialist. Even small deviations can lead to the symptoms mentioned.
Multifocal glasses are particularly tricky in this context. Since they have different areas of focus, the optometrist must adjust the lenses precisely. If the glasses are not optimally centered, the wearer can only see clearly if he balances this with head and body posture. For example, if the far area is centered too deep, he must lift his head to see clearly. This can lead to headaches and neck pain.
With your next visit to your optometrist you will now have more understanding as to why measurements need to be taken with your newly chosen glasses…..in order to perfect your vision.