Ray-tracing LASIK at one year: every eye at 20/20, and the astigmatism held

Design

Prospective, non-randomised interventional study with Alpins vector analysis, 12-month follow-up

Population

800 eyes of 400 patients with myopia or myopic astigmatism; 300-eye subgroup with cylinder 1.50 D or more

Primary outcome

Uncorrected distance acuity, spherical equivalent accuracy, stability, safety index and astigmatic vector parameters

Effect

100% at 20/20 or better and 68% at 20/16; 96.5% within 0.50 D of target; 0.38% drifted beyond 0.50 D from 1 to 12 months; residual cylinder 0.50 D or less in 91.7% of the high-cylinder subgroup

Eight hundred eyes of 400 patients with myopia or myopic astigmatism underwent femtosecond LASIK with ray-tracing-guided planning, which builds an individualised ablation profile by integrating biometry, tomography and wavefront data and reconciling the wavefront-derived refraction against the cycloplegia-verified manifest refraction. A pre-specified subgroup of 300 eyes had preoperative cylinder of 1.50 dioptres or more. Follow-up was 12 months.

At one year, 100% of eyes had uncorrected distance acuity of 20/20 or better and 68% reached 20/16, with a mean of minus 0.07 logMAR. The efficacy and safety indices were both 1.17, and no eye lost two or more lines of corrected acuity. Refractive accuracy was 96.5% within half a dioptre of target and 100% within one dioptre, with a mean spherical equivalent of minus 0.08 D and a predictability R-squared of 0.99. Stability held: only 0.38% of eyes changed by more than 0.50 D between one month and twelve.

The astigmatic results are the reason to read this. Residual cylinder was 0.50 D or less in 95.2% of eyes overall and 91.7% in the high-cylinder subgroup, with Alpins vector analysis showing mild undercorrection (correction index 0.94), a small difference vector (0.15 D overall, 0.21 D in the subgroup) and 85% of subgroup eyes aligned within 5 degrees of intended axis. Axis accuracy in high astigmatism is where conventional planning most often disappoints.

This is a prospective series without a comparator, so it cannot say the platform is better than wavefront-optimised or topography-guided treatment. It establishes that the outcomes are excellent and durable at a year.

• The distinguishing result is axis accuracy in eyes with 1.50 D or more of cylinder
• No comparison group - these outcomes cannot be ranked against other planning platforms
• Mild systematic undercorrection (correction index 0.94) is worth knowing when nomogram-adjusting
• Stability at one year was near-total; 0.38% of eyes drifted beyond 0.50 D
• Report vector parameters when auditing your own astigmatic outcomes, not just residual cylinder

Why it matters

Axis alignment in high cylinder is the failure mode of conventional planning, and this reports 85% within 5 degrees.

Don't overread it

Non-randomised with no comparison group - excellent outcomes, not demonstrated superiority.

The statistics, in plain English

A 100% rate of 20/20 uncorrected acuity is the sort of figure that should prompt a look at who was selected rather than celebration. This was a prospective non-randomised series at centres using the platform, so the population is people judged good candidates for it. The predictability R-squared of 0.99 describes how tightly achieved refraction followed intended refraction across the cohort, which is a measure of the planning, not of patient satisfaction. Without a comparator arm, none of these numbers can be read as evidence that ray-tracing outperforms wavefront-optimised or topography-guided treatment in the same eyes.

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