Corneal topography: what to expect

• Corneal topography provides a detailed map of the shape and curvature of the cornea – the clear, dome-shaped surface at the front of the eye.
• It is commonly used to detect eye conditions involving the cornea, assess astigmatism, guide contact lens fitting, and evaluate a person’s suitability for LASIK and other eye surgeries.
• The test procedure is quick and safe, and does not require any eye drops or instruments touching the eye.

The cornea is the clear, outermost layer at the front of the eye and plays a key role in focusing light so that we can see clearly. For good vision, the cornea needs to be smooth, evenly shaped, and transparent. Corneal topography is a non-invasive test that creates detailed maps of cornea, including the shape of the front and back surfaces, as well as its thickness.

Mapping the cornea is similar in many ways to making a three-dimensional (3D) map of the Earth. Though the surface appears round and smooth from afar, up close, there can be raised or irregular features – like mountains and valleys. A routine eye examination provides limited information about the shape of the cornea, especially in eyes with early or subtle abnormalities.

During corneal topography, and instrument called a corneal topographer works by shining a series of black and white rings onto the front surface of the eye. The instrument’s camera scans how these rings reflect off the thin layer of tears that cover the cornea. By studying the reflection of the rings, the corneal topographer can create a precise map of the cornea’s shape and curvature.

Corneal topography is one of the main tests used to screen potential candidates for vision correction procedures such as LASIK, and plan other surgeries involving the cornea. Before surgery, it is important to establish whether the cornea has a normal shape and sufficient thickness. This information helps the surgeon determine whether it is safe to proceed with the procedure and choose the optimal surgical techniques for the most successful outcomes. After surgery, corneal topography is used to evaluate healing and surgical outcomes, ensuring that the cornea is stable and that vision is improving as expected.

Another important use of corneal topography maps is to detect, diagnose, and monitor corneal conditions, including keratoconus, corneal dystrophy, and growths such as pterygium. These conditions may distort the shape of the cornea, leading to changes in astigmatism and vision as a result. Because many corneal conditions can progressively worsen, corneal topography is an essential tool for tracking changes in the corneal surface over time.

Corneal topography is also an essential tool in contact lens fitting, particularly for specialized contact lenses such as rigid gas-permeable (RGP) lenses, orthokeratology (OK) lenses, and other custom or diagnostic lenses. The maps help guide the initial lens design, assess how well the lens fits on the eye, and make adjustments to improve comfort and vision.

In addition to mapping the cornea, corneal topography can be useful in identifying the presence of dry eye. The quality of a corneal topography scan is highly dependent on how well the tears protect and lubricate the eye. Dry eyes can affect the topography scan, by producing patchy, missing, or misleading data.

Corneal topography is a quick, safe, and comfortable for patients of all ages. Because corneal topography does not involve any physical contact or require any eye drops, there are no effects on vision.

During the examination, you will be seated in front of a bowl-shaped device (the corneal topographer) containing a pattern of concentric rings. Some concentration is needed, as you will be asked to look at a fixed point (e.g. the centre of the rings) while the device captures detailed images of the surface of your eyes. The scan itself takes only a few seconds and may be repeated to ensure accurate and reliable results. The device will then convert the images into colour-coded maps of your cornea.

Once the test is complete, the optometrist or eye doctor will carefully analyze the corneal maps to assess the shape, curvature, and thickness of your cornea. They will discuss the findings with you, explaining whether your cornea is healthy, and inform you of the next steps such as whether any follow-up tests or monitoring are required.

A modern corneal topography map uses a coloured scale to represent the shape of the front surface of the eye, and how the shape or curvature may change from one area to another.

In the example below, cooler tones (blue-purple areas) suggest flatter regions, while warmer tones (orange-red) areas indicate steeply curved regions. Areas that are coloured green-yellow represent a normal curvature.

Corneal topography is needed in several situations where detailed information about the cornea is important. For example:

• Planning to wear contact lenses, especially rigid gas-permeable (RGP) or orthokeratology (OK) lenses
• Diagnosing and monitoring corneal conditions such as keratoconus
• Screening for LASIK and other vision correction surgeries
• Before and after corneal surgery, such as a corneal transplant

1. Sridhar, U. and Tripathy, K., 2022. Corneal topography.
2. Maria-Silvia DI, Marinescu MC, Corbu CG, Constantin MM, Tataru CI, Tataru CP. Corneal Topography–a Review of Available Investigation Methods and Impact in the Diagnosis and Follow-Up of Keratoconus. Mædica. 2025 Jun;20(2):374