Optical ray tracing

Customised excimer LASIK ablations currently rely on corneal topography or whole-eye wavefront technology. However, critics note that these fail to consider the multiple lens structure of the eye and fail to address all optical errors of the eye, resulting in a clinical outcome that may be poorer than expected. A new study suggests that optical ray tracing may be the next step in custom ablation. Researchers conducted a multicentre study of 127 eyes with moderate to high myopic astigmatism that underwent custom LASIK ablation based on a new optical ray-tracing algorithm. Approximately 84 per cent of 111 eyes available for follow-up at three months postoperatively had uncorrected distance acuity of at least 20/20. All were within 1 D of the intended correction, with 96 per cent within 0.5 D. Uncorrected distance visual acuity in eyes treated for high myopic astigmatism was better than in those undergoing wavefront-guided LASIK. The researchers conclude that the new system, which does not require a nomogram, is safe, efficacious and predictable. S Schumacher, JCRS, Optical ray tracing-guided laser in situ keratomileusis for moderate to high myopic astigmatism, Volume 38, Issue 1, pages 28-34.