Corneal topography provides the most detailed information possible about the curvature of the cornea. Using a very sophisticated computer and software, thousands of measurement scans are taken and analyzed in just seconds. Then, the topographer generates a color map from the data.
The map is interpreted just like any other topography map. The cool shades of blue and green represent flatter areas of the cornea, while the warmer shades of orange and red represent steeper areas. This corneal map allows the physician to formulate a “3-D” perspective of the cornea’s shape. In the following “normal” topography, you can see that the color gradient is very gradual over the whole surface of the cornea. This patient’s eye is very round, like a basketball, and has very little astigmatism.
Why is topography important?
It helps your optometrist formulate a complete assessment of your astigmatism. This is important in the fitting of contact lenses. At Clearview Eye Care, we perform topography on every one of our contact lens patients. It can aid in the selection of the appropriate contact lenses.
Patients with astigmatism may not be good candidates for certain contact lenses, and they may achieve better vision with special contacts based on the shape indicated in the topography readings. The following patient has significant astigmatism. Compare this picture to the “normal” topography above and you’ll see that there is a difference in the curvature of the eye, especially in the 12 o’clock to 6 o’clock meridian:
Corneal topography is also important because it can detetct irregularities in the cornea due to a disease called keratoconus. This condition is a progressive thinning of the cornea which causes a cone-like steeping on the surface of the eye. Corneal topography is the best way to help diagnose and map out the severity of keratoconus. It’s also the best way to monitor progression or worsening of the condition. Look at the following topography of a patient with keratoconus:
Keratoconus is a whole topic in itself that we’ll get to soon in another blog post, but you can see there is a big difference between this topography map and the “normal” one above. As always, if you have any questions or comments, feel free to post them or email them our way.