CT&WHing_Part2b_Corneal Wound Healing_2020BB PDF

WOUND HEALING IN THE EYE  Cornea – PKP, LASIK  Lens – post cataract surgery  Glaucoma filtration surgery  Proliferative vitreoretinopathy  Laser photocoagulation etc etc  CORNEAL WOUND HEALING  INFECTION  RAPID HEALING RESPONSE  TRAUMA...

WOUND HEALING IN THE EYE  Cornea – PKP, LASIK  Lens – post cataract surgery  Glaucoma filtration surgery  Proliferative vitreoretinopathy  Laser photocoagulation etc etc  CORNEAL WOUND HEALING  INFECTION  RAPID HEALING RESPONSE  TRAUMA  TRANSPARENCY  KERATOPLASTY  STRENGTH  REFRACTIVE SURGERY  STABILITY Nature and extent of the wound healing response is dependent on: Cause Type  chemical  superficial  mechanical  penetrating  Refractive & Transplant surgery  Photorefractive keratectomy (PRK)  Laser-assisted in situ keratomileusis (LASIK)  Laser-assisted sub-epithelial keratectomy (LASEK)  Penetrating keratoplasty (PKP)  Anterior lamellar keratoplasty (ALK) Photorefractive Laser assisted in situ Laser-assisted sub-epithelial keratometry (PRK) keratomileusis (LASIK) keratectomy (LASEK) (Cursoenarm.net n.d.)  Degrees of Haze Trace Mild Moderate Penetrating keratoplasty (PKP) /Corneal transplantation  Full thickness transplant  Replaces diseased cornea www.allaboutvision.com  Especially in cases of endothelial cell dysfunction www.msdmanuals.com  Anterior lamellar keratoplasty (ALK)  Partial thickness graft (epithelium and stroma)  Stromal pathologies without endothelial dysfunction Epithelial Wound Healing  Rounding off of wound edge, epithelial differentiation disappears  Stem cells & TACs proliferate (includes cells next to wound edge)  Loss of cell attachments: hemidesmosomes  Migration as a sheet (c.16 mm/hr), along temporary matrix  Re-epithelialisation & contact inhibition; hemidesmosomes reformed  Epithelial differentiation/stratification  3-7 days Stromal Wound Healing  keratocyte apoptosis at wound site  activation & proliferation of fibroblasts  migration to wound site  differentiation‘myofibroblast’  ECM remodelling: New synthesis of GAGs & collagen and degradation  fibrosis and ‘haze’  loss of vision  Return to normal (1-3 years!?)  Endothelial Healing  Required if damaged human corneal endothelial cells are unable to regenerate  Migrate across Descemet’s membrane to compensate regions of loss  Enlarge to fill in gaps => polymegathism & pleomorphism occurs  Density of 500 endothelial cells per mm2 required for cornea to remain transparent https:// webeye.ophth.uiowa.edu Regulators of Corneal Wound Healing  tear fluid  growth factors  adhesion molecules  proteolytic enzymes  Epithelial-stromal interactions are important in corneal wound healing Myofibroblasts Basement membrane defect (Spadea et al. 2016)