LaserSoft – Treatment Modalities
The laser system LaserSoft is intended for use in ophthalmic surgery, specifically for corneal refractive correction and ablation of the corneal surface. It can be used for Photo-therapeutic Keratectomy (PTK) and Photo-refractive Keratonomy (PRK) as well as for Laser-Assisted In Situ Keratomileusis (LASIK), LASEK (Laser Epithelial Keratomileusis) and epi-Lasik.
Standard Visual Acuity Correction (VAC) Treatments
Standard treatment is planned by taking into account the patient’s refractive error (sphere, cylinder and axis), curvature values on both steep and flat axis, pupilometry, desired optical and transition zone for the treatment and pachymetry data. The ablation profile for VAC is calculated by taking the difference of the corneal shape before the operation and the desired post-operative shape of the cornea. The cornea is described as a biconic surface which is a convenient representation of surface with axial astigmatism.
Wavefront guided treatments
This treatment option allows calculating the ablation profile specific to the eye by taking the ocular or corneal aberrations measured by the topographer or by the aberrometer. The data delivered by the wavefront diagnostic devices consists of Zernike polynomials and the diameter of the Zernike pupil size.
• Treatment for ocular wavefront aberrations
For the data acquired from the wavefront aberrometer, the diameter of the Zernike pupil is the diameter of the patient pupil during the examination.
• Treatment for the corneal wavefront aberrations
For the data acquired from the topographer, the diameter of the Zernike pupil is the diameter of the maximal corneal area the device was able to measure and fit to Zernike polynomials for the measurement of the patient.
The doctor can choose a different value of the optical zone than the Zernike pupil to be corrected. For the calculation of the ablation profile, first the standard sphero-cylindrical profile is calculated using the given refraction (sphere, cylinder and axis) of the desired correction. As an addition to this profile, the profile for the higher order aberrations delivered by the Zernike terms of the third order and higher is calculated and added to the desired ablation profile.
Katana LaserSoft’s small treatment laser beam profile of 0.2 mm diameter, allows achieving real customized laser treatments. The desired ocular and corneal wavefront data for the customized treatments can be acquired from the Sirius/Modi topographers of C.S.O., irx3 aberrometer of Imagine Eyes and from the combined topographer and aberrometer Keratron ONDA of Optikon.
Q-value guided treatment
This treatment modality is enabled in the system in order to modify the asphericity of the eye to achieve the ideal focusing in addition to standard VAC treatments. When this type of treatment is chosen, the pre-operative Q-value and the target Q-value of the eye are required for the treatment calculation besides the input data required for the standard VAC treatment. The ablation profile is calculated together with the pre-operative Q-value and the target post-operative Q-value to accomplish the desired asphericity of the eye.
Treatment of presbyopia
Katana LaserSoft system enables a bifocal treatment modality for the correction of the presbyopia. The tissue ablation profile is constructed by combining two standard VAC treatment calculations for a peripheral zone and for a central zone. The ablation profile for the peripheral zone is calculated by taking sphere, cylinder, axis and the pre-operative sim-K values into account. After calculating the ablation profile for the peripheral zone, the ablation profile for the central zone is calculated for the decided diameter of this central zone and for the additional spherical refraction to be achieved in the central part of the cornea. These two ablation profiles and a transition zone outside the peripheral zone are merged to accomplish one ablation profile.