Residual stromal bed (RSB) refers to the thickness of untouched corneal tissue remaining after laser ablation.
Maintaining sufficient RSB is critical to preserving corneal biomechanical stability and preventing post-laser ectasia.
Multiple landmark studies analysing ectasia risk identify reduced RSB as a major risk factor¹. While minimum safe values vary slightly across publications, many surgeons adopt a conservative threshold of ≥300 microns to maintain structural stability.
Biomechanical modelling demonstrates that anterior stromal tissue contributes disproportionately to corneal tensile strength². Therefore, preservation of adequate stromal integrity during primary surgery protects enhancement options later.
Enhancement must always respect remaining tissue limits. Removing additional tissue in a borderline cornea is contraindicated.
Modern screening tools including tomography and corneal thickness mapping further reduce risk. Long-term outcome reviews show that careful screening markedly lowers incidence of post-LASIK ectasia³.
Enhancement safety depends less on whether a second procedure is performed and more on whether conservative biomechanical thresholds were preserved at the first procedure.
Long-term refractive strategy must always prioritise structural integrity over optical perfection.
References
- Randleman JB, Woodward M, Lynn MJ, Stulting RD. Risk assessment for ectasia after LASIK. Ophthalmology. 2008;115(1):37-50.
- Santhiago MR, Smadja D, Gomes BF, et al. Association between anterior residual stromal bed and ectasia risk. J Cataract Refract Surg. 2014;40(6):918-928.
- Binder PS. Analysis of ectasia after LASIK. J Cataract Refract Surg. 2007;33(9):1530-1538.
Related Topics
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- Why Are Higher Prescriptions More Likely to Require Enhancement?
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- How Is LASIK Enhancement Performed?
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- Can Enhancement Affect Night Vision or Optical Quality?
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- Why Does Astigmatism Sometimes Remain After Laser Eye Surgery?
- What Is Epithelial Remodelling and Why Does It Matter?
- Is Enhancement Safer Than Intraocular Lens Exchange?
- What Is the Risk of Ectasia After Enhancement?
- Does Enhancement Affect Long-Term Vision Quality?
- What Does an Enhancement Cost?
