Latest-generation corneal topography machine Tomey TMS-5, which combines placido-based corneal topography and Scheimpflug camera, gives a map of the heights of the front/back corneal surface and details about ​​the pachymetry and anterior chamber depth. It is used in the [Microscan Visum + Corneal topography machine] platform for customized surgeries because combination of two technologies based on Placido rings and Scheimpflug camera yields more accurate and reliable results for the topographic map of the anterior corneal surface.

Kerascan imports data from corneal topography machine Tomey TMS-5, visualizes, diagnoses, computes correction of refractive disorders in severe corneal irregularities. These refractive disorders could be: small optical zone, decentered ablation, strongly elongated or flattened cornea, irregular astigmatism induced by Lasik, PRK, radial keratotomy, conductive keratoplasty, cataract surgery and deep lamellar keratoplasty. High-order aberration correction on the corneal surface is computed based on corneal wavefront data.

Additional input of clinical eye refraction data allows for simultaneous correction of the sphere and cylinder. In computation of low-order aberration correction, aspheric (abberationally neutral) ablation profile is used.

A feature of topogram operations is centering along the visual axis, rather than bythe center of the pupil. Topography-guided ablation has an advantage when it comes to surgeries in normal eyes, in the case of hyperopia and high astigmatism, when you need to correctly center ablation based on the kappa angle.

As a result, during customized operation, a symmetrical surface with a wide optical area that is independent of pupil size is created – with the best approximation to the natural corneal asphericity.

Customized corneal correction that is based on corneal topography data is called topography-guided excimer laser refractive eye correction.

The following are the important features of a topo-guided ablation using the KeraScan program:

• Aberration balance is preserved,
• No prismatic effect when calculating the ablation map
• Accurate exclusion of corneal astigmatism and its replacement with clinical refraction
• Preoperative values ​​of the asphericity Q factor are preserved
• Target change of factor Q, including for creation of multifocal aspherisity for presbyopia patients
• Pre-operative identification of visual axis offset from the center of the pupil (Kappa angle)
• Pre-operative compensation of torsional eye rotation