Corneal topography

What is it?

What exactly is the corneal topography?

The corneal topography (corneal topography) is a special test by which we can acquire useful information (through a series of coloured maps e.g. axial, elevation, tangential, refractive maps) on the curvature of the cornea (anterior & posterior segments – optical scanning of the anterior and posterior surface of the cornea). The different colours in a topographical map represent the distribution of refractive power on the corneal surface (center and periphery). The different colours in a corneal topography (corneal map) depict areas with higher or lower refractive power. The range of colours also helps to compare different eyes but also changes in the same eye.

topo1   topo2

Information therefore as the curvature and curvature of the cornea (control corneal smoothness), the keratometry, the measurement / display of the anterior and posterior surface of the cornea, the pachymetry, the height map (a colour range), the simulation of visual acuity, measuring pupil size (pupil diameter), the refractive power, even parameters for keratoconus are necessary for ophthalmologist.

When do we perform a topography?

When do we use corneal topography?

topo3   topo4

  • in consideration for keratoconus (conical cornea shape). The coloured topographic maps actually define the position, size and curvature of the cone and the keratoconus indices, the stage (keratoconus stage)
  • in the preoperative control if a patient is to undergo refractive surgery with excimer laser. In refractive surgery, the corneal topography is an important exam of primary importance, not only preoperatively and postoperatively. The topographic changes (e.g. contact lenses), the suspicion indicator for keratoconus, the configuration of the corneal surface, the distribution of refractive power, corneal thickness, the keratometry etc. are taken into account seriously. Many times the decision to refractive technique derives from corneal topography (PRK, conventional LASIK, Z-LASIK with femtosecond laser)

https://www.youtube.com/watch?v=hh76RtF50TE&w=600&h=420