Corneal Anatomy, Wound Healing (M) Flashcards
What layer of the epithelial basement membrane has laminin accumulation? 1. Is it more anterior or posterior to the other lamina? 2
- lamina lucida
2. anterior
What are the four phases in wound healing for the corneal epithelium?
- latency
- migration
- proliferation
- attachment
What are the processes that occur during the attachment phase of corneal epithelial wound healing?
- hemidesmosomes to BM
2. may take up to a year
What are the processes that occur during the latent phase of corneal epithelial wound healing?
- Cells transform to prepare for migration
- Apoptosis for damaged cells – shed into tears
- Fibronectin increases on wound bed
- Epithelial cells bind via integrins (surface proteins)
- Basal cells remove hemidesmosomes
What does a lumican deficiency lead to?
early opacification
What happens to keratocytes following insult?
change into myofibroblasts and produce ECM, MMPs, and cytokines
What are thickenings in the central Descemet’s membrane called?
guttata
How do bullae form?
corneal edema, often after cataract surgery
What type of collagen is in the banded zone of Descemets? 1. Non banded zone? 2
- type VIII
2. type IV
What type of collagen is in the Bowman’s membrane?
type I and III
What are the processes that occur during the proliferation phase of corneal epithelial wound healing?
- Cell mitosis initially by transient amplifying cells (TACs) – basal stem cells
- Slow cycling stem cells then proliferate
- Cells then differentiate to wing and surface cells
What are the benefits of the amniotic membrane?
- Serves as a substrate for epithelial growth
- Promotes epithelialization
- Supresses inflammation
- Inhibits angiogenesis
- Antimicrobial
What is fibrin and fibronectin important for?
hemidesmosomes and healing
What is released from injured epithelium?
cytokines
What effect does TGFβ from the epi after insult have on the stroma?
- Stimulates underlying keratocytes to migrate and morph into myofibroblasts
- reduced transparency
What are thickenings in the peripheral Descemet’s membrane called?
Hassall-Henle
When can there be a Descemet’s membrane detachment?
- DMEK
2. DALK
What is the blood component that remains after clotting that can can be used as tears?
autologous tears (serum)
What are the processes that occur during the migration phase of corneal epithelial wound healing?
- Basal cells flatten and spread to a monolayer
- Centripetal
- Contraction of actin filaments = movement
- Fibronectin dissipates
What effect does IL-1 from the epi after insult have on the stroma?
- Stimulates keratocyte synthesis of Fas-ligand
2. Fas-ligand binds to other keratocyte Fas receptors = Apoptosis (minimal collateral damage)
What is the surgical application of Dua’s layer?
helps prevent endothelial transplants from scrolling up and may help prevent haze
What type of drug is needed to penetrate the cornea to the anterior chamber?
amphipathic
Why does LASIK have less post-op haze than PRK?
harm little epi of less release of migrating factors and cytokines
What does epidermal growth factor do in corneal epi wound healing?
- Promotes epithelial cell proliferation and wound closure
2. Encourages fibronectin deposition
What does a keratocan mutation lead to?
cornea plana (abnormal curvature)
What effect does TGFα from the epi after insult have on the stroma?
Triggers stromal infiltration; phagocytosis of debris
What are the types of GAGs in the corneal stroma?
2/3 keratan
1/3 chondroitin
What does transforming growth factor (TGFβ) do in corneal epi wound healing?
- Encourages binding to fibronectin
2. Promotes migration
What are the major two collagen types in the stroma? 1. What are the others? 2
- type I and VI
2. type III and IV
What is the water content of the cornea?
78%
Is the cornea normally prolate or oblate in shape? 1. After LASIK? 2
- prolate
2. oblate
What do autologous tears contain to help the eye?
- Epidermal growth factor
- Fibronectin
- Neurotrophic growth factor
- Vitamin A
What layer of the epithelial basement membrane has type IV accumulation? 1. Is it more anterior or posterior to the other lamina? 2
- lamina densa
2. posterior
What is used after LASIK because it blocks DNA synthesis and therefore mitosis, stops myofibroblast formation?
mitomycin C
