Post Refractive Ectasia
1. Clinical Analogy & Conceptual Framework
Analogy: The Overworked Bridge Cable
Imagine the cornea as a suspension bridge. • Its collagen lamellae are the steel cables holding the structure under tension. • When you perform Laser-assisted in situ keratomileusis (LASIK), you cut through cables (microkeratome flap) and then ablate tissue (laser removes more cables). • As long as enough cables remain, the bridge holds its shape. • But if too many cables are severed - especially in an already-weak bridge (subclinical keratoconus) - the remaining structure cannot bear the intraocular pressure load. • The bridge sags, buckles forward, and ectasia results. This analogy captures three key truths: • The cornea's shape is maintained by tensile integrity of stroma • Any procedure that removes or weakens stroma risks biomechanical failure • Pre-existing weaknesses (forme fruste keratoconus) dramatically lower the threshold
2. Definition & Historical Context
Definition
- Post-refractive surgery ectasia (PRE) is a progressive, non-inflammatory corneal ectatic disorder characterized by progressive stromal thinning, anterior protrusion, and irregular astigmatism developing after refractive surgery (laser-assisted in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), laser-assisted subepithelial keratectomy (LASEK), small incision lenticule extraction (SMILE), or radial keratotomy (RK)), in the absence of infection or trauma.
Historical Milestones
| Year | Event |
|---|---|
| 1998 | • First reported case of post-laser in situ keratomileusis (LASIK) ectasia • Seiler, Koufala & Richter |
| 1999 | • Rabinowitz and Rasheed introduced the keratoconus percentage (KISA%) index • Quantitative keratoconus screening |
| 2003 | • Risk factors and prognosis for corneal ectasia after laser in situ keratomileusis (LASIK) published • Randleman et al. |
| 2003 | • Wollensak, Spoerl & Seiler reported the original clinical riboflavin/ultraviolet-A corneal collagen cross-linking (CXL) protocol • Commonly associated with the Dresden Protocol |
| 2004 | • Intacs received United States Food and Drug Administration (FDA) humanitarian device exemption (HDE) for keratoconus |
| 2008 | • Randleman Ectasia Risk Score System (ERSS) published |
| 2016 | • KXL System included in the United States Food and Drug Administration (FDA)-reviewed conventional corneal collagen cross-linking (CXL) protocol • Progressive keratoconus and corneal ectasia following refractive surgery |
| 2010s | • Small-incision lenticule extraction (SMILE) ectasia cases documented • Topography-guided corneal collagen cross-linking (CXL) emerging |
| Year | Event |
|---|---|
| 1998 | • First reported case of post-laser in situ keratomileusis (LASIK) ectasia • Seiler, Koufala & Richter |
| 1999 | • Rabinowitz and Rasheed introduced the keratoconus percentage (KISA%) index • Quantitative keratoconus screening |
| 2003 | • Risk factors and prognosis for corneal ectasia after laser in situ keratomileusis (LASIK) published • Randleman et al. |
| 2003 | • Wollensak, Spoerl & Seiler reported the original clinical riboflavin/ultraviolet-A corneal collagen cross-linking (CXL) protocol • Commonly associated with the Dresden Protocol |
| 2004 | • Intacs received United States Food and Drug Administration (FDA) humanitarian device exemption (HDE) for keratoconus |
| 2008 | • Randleman Ectasia Risk Score System (ERSS) published |
| 2016 | • KXL System included in the United States Food and Drug Administration (FDA)-reviewed conventional corneal collagen cross-linking (CXL) protocol • Progressive keratoconus and corneal ectasia following refractive surgery |
| 2010s | • Small-incision lenticule extraction (SMILE) ectasia cases documented • Topography-guided corneal collagen cross-linking (CXL) emerging |
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Keep reading Post Refractive Ectasia
23 more sections are included with the Clinical plan.
- Epidemiology & Incidence
- Key Fact
- Pathophysiology - Biomechanical Basis
- BIOMECHANICAL THEORY: Stress-Strain Hypothesis
- Risk Factors & Pre-Operative Screening
- Key Individual Risk Factors