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What is Corneal Topography?

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A common cornea condition is keratoconus

Whether you’re getting contact lenses, planning on having laser eye surgery, or looking for a treatment for dry eyes, we will assess your cornea using a corneal topographer. Corneal topography is a common technology many optometrists and ophthalmologists use to examine your cornea and its health, helping your optometrist determine the source of your eye issues or even your qualifications for treatments like laser eye surgery or contact lenses.

Today, we’re going to take a detailed look at the cornea, corneal conditions, and the variety of ways corneal topographers can help optometrists detect these issues.

But before we start discussing the uses of a corneal topographer, let’s take a look at the cornea and the issues that could affect it.

The Cornea & Corneal Conditions

If you have heard the saying, “the eyes are the window to the soul,” the cornea would be the window. Covering the outermost area of the front of your eye, including the pupil, iris, and anterior chamber, the cornea is responsible for focusing light in your eye, helping you see clearly.

The cornea is often referred to as the outermost layer of your eye, and has 6 different layers, including the:

  • Epithelium
  • Bowman’s layer
  • Stroma
  • Duas layer
  • Descemet’s membrane
  • Endothelium

When it comes to conditions that could affect the cornea, refractive errors are some of the most common, including nearsightedness, farsightedness, and even astigmatism. However, these aren’t the only conditions that can affect the cornea. Others include:

While there are many conditions corneal topography can help diagnose, not all corneal topographers are the same. Depending on the type of issue you may be experiencing, or the certain goals you may have for your vision, your optometrist may elect to use different corneal topography technology to assess the health of your cornea

Determine your eligibility for contact lenses and laser eye surgery using corneal topography.

Types of Corneal Topography

Corneal topography is a non-invasive imaging technique that typically uses one of 3 different types of technology:

  • Technology based on light reflecting on the cornea (Placido disks).
  • Technology based on optical slits (scanning-slit topography).
  • Technology based on a rotating camera taking cross-sectional scans (Scheimpflug imaging).

Placido disc topography can be used to measure elements of your anterior (epithelium) cornea, including your tear film quality, the curvature of the cornea, and other irregularities that could affect your eye comfort and vision.

Scheimpflug and slit-scanning topography can be used to examine the anterior and posterior (endothelium) surfaces, helping your optometrist detect issues like posterior corneal astigmatism.

Types of Topographic Maps

These corneal topographers can then help create various topographic maps to help your optometrist examine your cornea for potential issues. These maps include:

Axial Display Map

Axial display maps are often used to view the cornea’s central curvature but aren’t very accurate when measuring the curvature of the peripheral cornea.

These maps can help determine the base curve of soft contact lenses, but for a more accurate reading, your optometrist may use a different topographical map.

Tangential Display Map

Optometrists use tangential display maps to help determine the cornea’s power and curvature, making them a fantastic option for fitting patients with contact lenses. This map may also help determine the power of a contact lens over the cornea, allowing optometrists to view the patient’s optical quality better.

Elevation Display Map

If there is an aspect of the cornea considered the “most important” when examining a patient’s eyes with a corneal topographer, it may be the corneal elevation. Corneal elevation is important for determining the fit of contact lenses for irregularly-shaped corneas, specifically corneal or scleral contacts.

Corneal Thickness Display Map

Corneal thickness can be determined by using posterior corneal topographers like scanning-slit topography and Scheimpflug imagery. While examining your corneal thickness can help detect diseases like keratoconus and managing the progress of ortho-k treatments.

Tear Break-Up Display Map

If you have dry eyes, or if you’re interested in contact lenses, tear break-up display maps are necessary for determining the health of your natural tear film. Tear break-up display maps may also be used for future contact lens appointments to ensure your tear film isn’t negatively impacted by contact lens use.

Corneal Topography is Quick & Contact-Free!

If you’re worried about being assessed through corneal topography, don’t be! Corneal topography exams are non-contact and can be completed in minutes! In this short time, our team can find the valuable information we need to help you address any issues you may be experiencing with your cornea, or even move you forward in the contact lens or laser eye surgery process.

Please book an appointment with us today and see the difference quality eye care can make!

Written by Dr. Asim Prasad

Dr. Asim Prasad is a native Calgarian who earned his Bachelorís of Science degree in Vision Science and Doctor of Optometry degree from Nova Southeastern University in Ft. Lauderdale, Florida in 2008. Before becoming an optometrist, Dr. Prasad earned a bachelorís degree in Environmental Science from the University of Alberta. After working in the environmental science industry for a short time, Dr. Prasad decided to pursue his true passion: optometry.
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