# Optical knowledge

Concepts, examples and references for optical dispensing. Explore 12 topics and three educational calculations.

- [Pupillary distance: which measurements should you record?](https://lensas.com.br/en/knowledge/pupillary-distance/)
- [Optical centration: from measurement to fitting](https://lensas.com.br/en/knowledge/optical-centration/)
- [How to calculate horizontal decentration](https://lensas.com.br/en/knowledge/horizontal-decentration/)
- [Frame geometry: A, B and bridge](https://lensas.com.br/en/knowledge/frame-geometry/)
- [Refractive index: why prescription power alone is not enough](https://lensas.com.br/en/knowledge/refractive-index/)
- [Lens materials: compare more than index](https://lensas.com.br/en/knowledge/lens-materials/)
- [Lens thickness: inputs needed for an estimate](https://lensas.com.br/en/knowledge/lens-thickness/)
- [Vertex distance: record the wearing position](https://lensas.com.br/en/knowledge/vertex-distance/)
- [Pantoscopic tilt: measurement and convention](https://lensas.com.br/en/knowledge/pantoscopic-tilt/)
- [Transposition: another notation for the same prescription](https://lensas.com.br/en/knowledge/prescription-transposition/)
- [Prentice’s rule: approximate prism magnitude](https://lensas.com.br/en/knowledge/prentice-rule/)
- [Remote edging: what must travel with a shape](https://lensas.com.br/en/knowledge/remote-edging/)