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Introduction to Corneal

TransplantStephen Lau

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Outline

Anatomy Histology

Indications Techniques

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Anatomy

Avascular = Transparency Nutrients Via Diffusion Air Tear Aqueous Fluid

Unmyelinated Nerve Endings = Sensitivity

[V1] Refractive Power

2/3 of Total Refraction Fixed (1/3 at Lens Fine Tunes Focus)

Dimensions Diameter

11.5mm Thickness Thinner at Center than Periphery

0.5-0.6 mm vs. 0.6-0.8 mm

Source: wikipedia.com

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Histology Epithelium

Regenerative Capacity Bowmans Membrane I/V Collagen Stroma I/V Collagen

Keratocytes Repair/Maintenance Duas Layer Descemets Membrane IV Collagen Endothelium

No Regenerative Capacity Hypertrophy Function Dehydrates Cornea (Na +/K+-ATPase) = Transparency Damage = Oedema/Clouding

Source: Sci-News.com

Source: naturephotography.info

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Indications Optical Impaired Vision

Ectasias (Bulging) Keratoconus (Bowmans Layer )

Dystrophies Fuchs Endothelial Dystrophy (Endothelium/DM )

Degenerations Salzmanns Nodular Degeneration (Bowmans Layer )

Infection/Trauma Scarring Tectonic Severe Structural Change

Thinning Prevent Perforation Therapeutic

Chronic Corneal Infection Refractory to Abx Cosmetic

Source: emedicine.medscape.com

Source: wikipedia.com

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Techniques

Full Thickness Penetrating Keratoplasty (PK) 1905

Partial Thickness (Lamellar) Anterior

Deep Anterior Lamellar Keratoplasty (DALK) 1970s/80s Posterior (Endothelial)

Deep Lamellar Endothelial Keratoplasty (DLEK) 1998 Descemet-Stripping EK (DSEK) 2005 Descemets Membrane EK (DMEK) 2008

Source: eyesite.org

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Techniques

DLEK vs. DSEK vs. DMEK DLEK

Endothelium + DM + Stroma DSEK

Endothelium + DM Stripped Endothelium + DM + Stroma Transplanted

DMEK Endothelium + DM

Source: Fernandez MM and Afshari NA. Endothelial Keratoplasty: From DLEK to DMEK. Middle

East Afr J Ophthalmology. 2010; 17(1): 5-8.

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Comparison

Penetrating Lamellar

Indications Any Layer Affected One Layer AffectedE.g.) Keratoconus, Fuchs EndothelialDystrophy

Healing Time Up to 2 Years Days-Months

Risk ofRejection

Higher Lower (Less Foreign Antigen)

Risk ofDehiscence

Higher Lower

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DALK

Corneal Trephination Corneal Tunnel

Inject Air Anterior to DM Remove Cornea Anterior to Bubble Inject Viscoelastic to Bubble Incise into Bubble Transplant Cornea Remove DM

Source: youtube.com

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DLEK Corneal Tunnel Stromal Dissection Remove Posterior Cornea

Scissors (Blades in Stroma + AC) Donor Tissue Stromal Dissection Donor Tissue Insertion Temporary Air Bubble Tamponade AC Irrigation + Spontaneous Unfolding

Endothelium Fluid Pump = Suction Pull Down Edges Posterior to Transplant Remove Air Bubble + Suture Incisions

Source: youtube.com