A topographic map of the cornea imaged with the help of a computer system is a very useful tool in the diagnosis of defects of the cornea.
The device that’s used is able to read and analyze the corneal surface irregularities.
Indications for this procedure:
- Suspected keratoconus
- Corneal Reshaping Therapy – Orthokeratology www.chicagovisioncorrection.com
Corneal topography is a basic examination of the patient that’s qualified for a laser refractive surgery. The test is painless, non-invasive and takes only a few minutes.
A keratoscope is used to measure the corneal surface. With these measurements, we can diagnose the following abnormalities of the cornea:
- Post traumatic or postoperative deformations
- Keratoconus with the assessment of the degree of advancement and possible progression.
Computer keratometry is used in surgical vision correction.
It also helps in the selection of hard contact lenses. The measurement results are presented graphically in the form of a so-called. corneal map (two or three dimensional).
How to perform the test
The test is painless, non-invasive. The patient leans the chin and the forehead and is seated facing an illuminated red “bowl” containing concentric black rings, which are reflected on the cornea. During the examination the patient is to look straight at a white light that’s inside the bowl.
Reflections of the rings on the cornea, their width and distortions are recorded during the study and analyzed by a computer and then translated into radii of curvature of the cornea. Their graphical representation, through the use of color (as in a geographical map), gives a color image, which is known as the map of the cornea. It can also be spatially represented in the form of a 3D map. The camera software allows a very detailed mathematical analysis of the corneal surface, based on the ranks of the Fourier and Zernicke’a polynomials.
The use of these tools are very helpful in the evaluation of keratoconus, in particular in its early detection, before the onset of clinical symptoms, the degree of its progression, changes after refractive surgery, corneal transplantation and after injuries. It’s also helpful and used when selecting the right hard contact lenses. The program allows you to create maps of comparison – to assess the possible progression of a disease. The map of the cornea is also used to calculate the power of the lens that’s being implanted into the eye during a cataract surgery.