Hemidivisional Vector Planning To Reduce And Regularize Irregular Astigmatism By Laser Treatment

To demonstrate how hemidivisional Vector Planning of refractive laser treatments of astigmatism can be used to directly address idiopathic corneal irregular astigmatism.

Case study, NewVision Clinics, Cheltenham, Australia.

 

The cornea is conceptually divided into two hemidivisions along the flat meridian of the corneal topographic astigmatism (CorT). An astigmatism reduction treatment can then be planned separately for each hemidivision using the Vector Planning technique, based on both its two hemidivisional CorT measures and common manifest refractive cylinder. The remaining irregularity is then regularized, and the junctional zone smoothed across the flat meridian. The final intended treatment thus combines hemidivisional astigmatism reduction and regularization of the corneal astigmatism and spherical refractive error in one treatment application.

A theoretical treatment profile is derived from an actual example of a cornea with idiopathic asymmetric non-orthogonal astigmatism. The three steps of the derivation are: (i) astigmatism reduction through the use of the Vector Planning technique, (ii) regularization and (iii) smoothing across the hemidivisional midline.

Hemidivisional Vector Planning treatments both reduce and regularize asymmetric non-orthogonal astigmatism. These treatments can be systematically customized to account for qualitative and quantitative differences between the two corneal hemidivisions at the same time as correction of coexistent myopia or hyperopia.