Guides & References
Plain-language explainers to go alongside the ODAtlas lookup tables and tools
ODAtlas is built for speed at the chair, but the numbers in our tables (Dk, base curve, cylinder, replacement schedule) all carry clinical meaning. These short guides explain what those parameters are, how to apply them, and where the common pitfalls hide. They are written for optometrists, opticians, contact lens technicians, and students who want the reasoning behind the reference data.
How to Read a Contact Lens Specification
Every column in the ODAtlas tables explained: base curve, diameter, power, cylinder, axis, Dk, wear and replacement.
Understanding Dk, Dk/t & Oxygen Transmissibility
What oxygen permeability really measures, why thickness matters, and the transmissibility thresholds behind healthy wear.
Vertex Distance Conversion
Why spectacle and contact lens powers differ, when the correction matters, and how to apply it accurately.
Contact Lens Replacement Schedules Compared
Daily, two-week, and monthly modalities: the trade-offs in compliance, cost, comfort, and ocular health.
Toric Lenses & Astigmatism Basics
Cylinder, axis, and stabilisation explained, plus how to read a toric parameter grid and troubleshoot rotation.
Multifocal & Presbyopia Fitting Basics
Add powers, optical designs, and dominance: a practical primer on getting presbyopic contact lens fits right.
How to use these guides
Each guide pairs with the reference pages you already use. Reading a toric grid? Open the Toric lenses table alongside the astigmatism basics guide. Converting a high myope's spectacle prescription? Keep the vertex conversion tool open next to the vertex distance guide. The goal is to make the data usable, not just visible.
These guides are educational references and general in nature. They do not replace manufacturer package inserts, professional clinical guidelines, or your own clinical judgement. Always verify parameters against official manufacturer documentation before fitting or prescribing. See our full disclaimer.