Sum of magnitudes (conservative) vs. tissue-optimized, platform-specific estimate for hyperopic/mixed astigmatism.
µm, central corneal thickness
D, signed
D, minus-cylinder convention
Femto-LASIK
PRK / TransPRK
KLEx (lenticule)
Astigmatism Ablation Model
In compound myopic astigmatism, the sum of magnitudes already equals the steeper principal meridian – no difference.
Conservative · Sum of magnitudes
Tissue-optimized · bitoric
–
Residual Stromal Bed
Treatment amount (model)–D
Principal meridians M₁ / M₂–D
Ablation depth–µm
PTA–%
Conservative
–
µm ablation
Tissue-optimized
–
µm ablation
Hyperopic astigmatism is only treatable to a limited extent by lenticule extraction (hyperopic mode currently VisuMax 800, limited range). For this case, LASIK/PRK or a toric phakic IOL is realistically the better option.
Approximate model for screening and teaching, not a substitute for the platform's own treatment planning. Constants: LASIK/PRK 14 µm/D, KLEx 16 µm/D; flap 110 µm, cap 125 µm, epithelium 50 µm; minimum RSB 280 µm. Tissue-optimized = steeper principal meridian max(|M₁|,|M₂|); the platform factors represent peripheral overhead and are illustrative, not validated.