Whenever a powered spectacle lens or a contact lens is prescribed, vertex distance is calculated.
It is the distance between the anterior surface of the cornea and the posterior surface of the spectacle lens or contact lens. This forms bridge to a clear and focused vision.
The average is between 12-14mm in spectacle lens.
In case of contact lens the vertex distance is ‘’0’’. This is because the lens directly sits on the corneal surface.
Why Vertex Distance Correction is Important?
Gives accurate refraction
Useful in high powered lenses.
Improves patient comfort
Prevents over-correction or under-correction
Essential when converting spectacle power to contact lens power.
Did you heard about this measurement during your eye checkup?
MBH/PS