pathophysiology

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CHEMICAL EYE INJURIES
G. PAPANIKOLAOU
EPIDEMIOLOGY
2/3 at work, young, males
Alkali:acid=2:1
Alkali: NH3, NaOH, Ca(OH)2, KOH, MgOH2
Acid: H2SO4, HF, Acetic, HCl
Damage depends on:
• pH
• area
•Volume/duration
•Inherent toxicity
PATHOPHYSIOLOGY
ACID
ALKALI
Denaturation+ precipitation
of proteins on contact/
‘ground glass appearance’
Barrier to penetration
Damage to stromal matrix
secondary to inflammation
Saponification of fatty
acids in cell
membranes
Rapid penetration
Damage to deeper
structures
• Direct effect
• Indirect effect (inflammation)
PATHOPHYSIOLOGY II
POINTS IN CORNEAL HEALING:
• Epithelium regulates keratocytes, prevents sterile ulceration
• TGF-beta 2: inhibits collagenase synthesis by keratocytes
• Limbal vessels: provide collagenase inhibitors
• Stem cells: centripetal healing
• ‘Transdifferentiation’/ ‘conjuctivalization’
• Stroma: type I collagen (keratocytes)
• Steroids intervene with keratocyte migration/ synthesis
• Ascorbate co- factor in collagen synthesis
• MMPs: increase after 10th day
• PMN: 12-24h and 14-21days
PATHOPHYSIOLOGY III
PHASES:
1. Immediate
2. Acute (0-7)
3. Early repair (7-21)
4. Late repair (>21)
GRADING
• Corneal clarity
• Limbal ischaemia
Grade
Signs
Prognosis
1
Clear/no
excellent
2
Visible iris
details/ <1/3
Hazy iris view/
1/3<x<1/2
Opaque/ >1/2
good
3
4
guarded
poor
ACUTE MANAGEMENT
EMERGENCY !!!
AIMS
• Remove offending agent/ stop further damage
• Reduce inflammation
• Control IOP
• Reduce matrix degradation
• Promote reepithelization
MANAGEMENT I
• Irrigation
• Eversion of lids
• Debridement
• A/C Paracentesis
Grade I and II: steroid, antibiotic, cycloplegia for 1/52.
TIPS
• Recheck pH 5-10 min after irrigation
• White eye worse than red
• Complete epith defects or if only Bowman’s delay in
taking up FLN: Repeat
• Avoid PHNL
MANAGEMENT II
• Steroids/ up to10/7, NSAIDS
• Antibiotics
• Vit-C/ early
• Citric acid/ Ca chelation/ early
• Tetracyclines/ chelate zinc
• Acetylcysteine/ MMP
• Artificial tears
• BCL
• Tarsoraphy
• IOP control
MANAGEMENT III
• Tenoplasty/ early in grade IV (limb. Vascularity)
• Stem cell transplant (auto/allo)/ early or late
• Amniotic membrane graft
• Conjuctival/ mucosal grafts
• Correct lid malposition
• Fornix reconstruction
• Dry eye
• Glaucoma, Cataract
• Cyanoacrylate glue, tectonic PTK
• PTK (large), Keratoprosthesis
COMPLICATIONS
• Non-healing epith defect/ conjuctivalization/ melting (stem)
• Corneal opacities
• Cataract
• Glaucoma/ phthisis
• Dry eye
• Lid malposition/ symblepharon/ trichiasis: more scarring
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