Topographer

How to complete and chart corneal topography

WHAT IS THIS TEST:

Corneal topography is a computer assisted diagnostic tool that creates a three-dimensional map of the surface curvature of the cornea. The cornea (the front window of the eye) is responsible for about 70 percent of the eye’s focusing power. An eye with normal vision has an evenly rounded cornea, but if the cornea is too flat, too steep, or unevenly curved, less than perfect vision results. The greatest advantage of corneal topography is its ability to detect irregular conditions invisible to most conventional testing.

Corneal topography produces a detailed, visual description of the shape and power of the cornea. This type of analysis provides your doctor with very fine details regarding the condition of the corneal surface. These details are used to diagnose, monitor, and treat various eye conditions. They are also used in fitting contact lenses and for planning surgery, including laser vision correction. For laser vision correction the corneal topography map is used in conjunction with other tests to determine exactly how much corneal tissue will be removed to correct vision and with what ablation pattern.

Computerized corneal topography can be beneficial in the evaluation of certain diseases and injuries of the cornea including:

  • Corneal diseases

  • Corneal abrasions

  • Corneal deformities

  • Irregular astigmatism following corneal transplants

  • Postoperative cataract extraction with acquired astigmatism

The corneal topography equipment consists of a computer linked to a lighted bowl that contains a pattern of rings. During a diagnostic test, the patient sits in front of the bowl with his or her head pressed against a bar while a series of data points are generated. Computer software digitizes these data points to produce a printout of the corneal shape, using different colors to identify different elevations, much like a topographic map of the earth displays changes in the land surface. The non-contact testing is painless and brief. Do not do a complete topo on a dilated patient.

HOW TO USE THE TOPO:

  1. To turn the topographer on and off, press the button on the lower right side of the instrument.

  2. For New Patients, enter Last name, First name, DOB, ID and gender then click save. To pull up a current patient, touch the List tab on the screen to bring up a list of current patients in the system, do a quick search by typing the patient’s name in the upper left hand box.. Touch New Exam to begin a new measurement.

  3. Select the preferred test from the bottom middle of the screen (Topo, Pupil, Fluro, Tear).

  4. For Topography, have the patient place their chin on the chinrest and forehead all the way forward, focusing right in the center of the concentric ring target. Align the “+” in the center of the pupil, using the toggle to move up/down and gently move the base side to side and forward/backward getting the image into focus. Push the black button on the top of the toggle handle when clear, following the instructions on when to move closer and farther from the patient.

  5. Repeat on other eye.

Please watch the following videos which illustrate the above process (you will need to select CC w/autotranslate in English)

Also watch this video which illustrates how to perform meibography, blink analysis, and TBUT with the topographer (again, you will have to select CC w/autotranslate to english)