RESIDUAL STROMAL BED & RCT CALCULATOR

Enter refraction, optical zone, pachymetry and flap thickness. The tool derives central ablation depth from measured ablation-per-diopter tables, then applies the floors that belong to the selected procedure family.

THE FLOORS ARE PROCEDURE-SPECIFIC

• LASIK / iLASIK / Q-LASIK — residual stromal bed ≥ 300 µm, residual corneal thickness ≥ 400 µm
• SMILE / SILK — bed ≥ 280 µm with a 470 µm pre-operative pachymetry minimum; the 280 µm figure is only reachable with a 120 µm cap, because the 400 µm RCT floor becomes binding with thinner caps
• PRK / T-PRK — a 50 µm epithelium is counted; the bed floor is graded, 300 µm only when biomechanical indices are measured and normal, otherwise 330–350 µm

In the published case-control series of post-LASIK ectasia, 70% of affected eyes had a residual bed below 250 µm, and the mean bed in ectasia cases was 223 µm against 294 µm in controls.^[1] Residual bed thickness is one of the weighted variables in the ectasia risk score.^[2]

WHERE THE ABLATION DEPTH COMES FROM

Depth is not taken from Munnerlyn alone. RLES AI uses measured ablation-per-diopter values — 12.0 µm/D at a 6.0 mm optical zone, 15.0 at 6.5 and 17.8 at 7.0 — interpolating between them and falling back to Munnerlyn below 6.0 mm, where the two agree exactly.^[3] Central depth also depends on the refractive mode: in hyperopic treatment central ablation is zero because tissue is removed in the periphery, and in mixed astigmatism only the cylindrical component is ablated centrally.

THIS IS THE GEOMETRY, NOT THE DECISION

Two floors holding does not make an eye a candidate. The same case still needs ectasia screening, the post-operative keratometry window, the device's own nomogram, tear-film and warpage checks, and a medication and chronic-disease history. See the full data set behind a single case.

FREQUENTLY ASKED QUESTIONS