Contact Lens & Vertex Distance Blog

Vertex distance is the gap between your spectacle lens and the cornea, and it changes the power needed for contact lenses. Here's why it matters.

Converting spectacle power to contact lens power isn't as simple as copying the Rx. Here's the step-by-step process with real examples.

For prescriptions above ±6.00 D, ignoring vertex distance can mean a half-dioptre error in your contact lens fitting. Here's what you need to know.

From skipping vertex distance conversion to ignoring tear film quality, these are the most common contact lens fitting errors and how to avoid them.

Myopic contact lenses always carry less negative power than the spectacle prescription. Here's the optics behind it, with real numbers.

Hyperopic contact lenses need more positive power than the spectacle prescription, often by 0.50D or more. Here's the reason and the numbers.

Most practitioners default to 12mm, but measuring the actual vertex distance matters for high prescriptions. Here's how to do it right.

Astigmatic prescriptions need vertex distance conversion for both sphere and cylinder. Here's how to approach toric lens fitting with accurate converted powers.

Presbyopic patients can wear contact lenses successfully, but multifocal fitting takes more than copying the near addition. Here's the clinical approach.

If your glasses say −7.00D but your contact lenses say −6.50D, that's not a mistake. Vertex distance explains the difference, and it's intentional.