Keratoconus
We can identify uneven bulging and unusual thickness patterns and compare them over time.
Three-dimensional measurement of shape, curvature and thickness
Keratography and corneal tomography
The cornea provides much of the eye’s focusing power. Keratography and tomography map its shape in colour, allowing us to measure irregular curvature and structural changes.
Understanding the procedure
Topography shows the surface; tomography shows the three-dimensional structure.
A keratograph analyses light reflected from the cornea to map curvature and focusing power. Tomography also records cross-sections, the front and back surfaces and thickness distribution.
Together, the tests help distinguish regular astigmatism from irregular changes and identify early signs of keratoconus or other ectasias.
- Measurement
- Curvature, shape and thickness
- Contact
- Non-contact
- Presentation
- Colour maps and a 3D model
- When it is used
- cornea, contact lenses, surgical planning
Used where needed
When is a corneal map useful?
The clinical question determines which maps and measurements are needed.
Contact lenses
Corneal geometry helps us fit rigid, scleral and other specialist lenses more precisely.
Refractive procedures
The measurement helps assess whether corneal shape and thickness are suitable for laser correction or suggest risks.
Cataract planning
Irregular astigmatism and corneal surface changes may affect lens calculations.
Step by step
This is how the cornea card is created.
A stable eye surface and the correct break from contact lenses are important.
Checking the break from contact lenses
Rigid and soft contact lenses can temporarily change corneal shape. We advise individually how long to leave them out.
Centre the surface
You focus on a target while rings or slits of light are projected onto the cornea.
Comparing medical images
We check alignment, eyelid shadows, tear film and repeatability of measurements.
Bringing the maps together
We assess curvature, elevation, both surfaces and thickness alongside vision tests and slit-lamp findings.
Understanding the results
Colour maps need clinical interpretation.
Highlighted colours do not necessarily indicate disease. Devices use different scales and reference values. We look at patterns, symmetry, measurement quality and changes over time.
A dry or unstable tear film can make the surface appear irregular. Before a final surgical decision, we may repeat measurements after treating the eye’s surface.
Well prepared
How to prepare for your visit
- Follow the agreed break from contact lenses
- do not reinsert contact lenses before testing without advice
- Use eye drops as discussed
- Bring previous topography or tomography results
Frequently asked questions
Clear, concise answers.
Is keratography the same as pachymetry?
No. Keratography mainly maps surface curvature; pachymetry measures thickness. Tomography can combine both in a three-dimensional analysis.
Why do I need to stop wearing contact lenses temporarily?
Contact lenses can temporarily alter corneal shape. Without enough time for it to settle, diagnosis and surgical planning may be inaccurate.
Can the measurement safely exclude a keratoconus?
It provides valuable information. A reliable assessment combines several maps, image quality, follow-up, vision tests and clinical examination.
Medical note
This page cannot replace an eye examination. Your symptoms, history and findings determine which tests are useful and how their results should be interpreted.
Medical basics
Sources and further information.
Related topics
All non-surgical eye care services