Cornea

SCLERATrixie Belle Detros O.D.

LAYERS

Episclera – is a loose, elastic tissue that connects the sclera and the conjunctiva & contains a network of blood vessels› Outermost layer, vascular from anterior

ciliary artery, acts as sinovial membrane› Where the rectus is connected.

Lamina fusca – a thin layer of pigmented connective tissue on the inner surface of the sclera, connecting it w/ the dura and choroid.

Contains melanocytes

Histologya) Consist of many dense bands of parallel

and interlacing fibrous bundles (makes it opaque)

b) Each of which is 10-16 micrometer thick c) 100-140 micrometer wide

Blood Supply – anterior ciliary artery - posterior ciliary artery

Physiology› Less uniform› Almost completely hydrated in its nomal

state

Function :a) Serves as attachement of EOMb) Protective covering of the eyec) Maintain Globular shape of eyeball

CONJUNCTIVA

A transparent membrane that covers the eyeball and anterior eyeball.

Lines the anterior scleraand eyelids

Parts

Palpebral conjunctiva – It lies to the anterior part of the eyelids

Bulbar conjunctiva – covers the scleraFirmly adherent to the limbus.

Fornix – located between your eyelids & sclera

¤ Margin between the eyelids & sclera¤ It starts a plica semilunaris to caruncle

lateral fornix – located at plica semilunaris (14mm) to your caruncle.

Loose retrotarsal fold, doesn’t adhere to tarsal gland For your eyelids to loosely move

1. Superior fornix - measures 10mm from limbus to orbital margin

2. Inferior fornix – measures 8mm palpebral to limbus

More lymphoid and inflamatory cells

Cul de sac - space between the eyelids and sclera

Where tear film is located. Capacity to carry 20-30µl of tears Depth of 2mm

Blood supply Posterior conjunctival artery Anterior ciliary artery

Innervations › Opthalmic division (Frontal and Lacrimal

nerves) and Maxillary division (Infraorbital Nerve) CN5

› Ciliary diviion (sensory part of bulb of conjunctiva) and sympathetic nerves of CN3

Chemosis Swelling of conjunctiva Due to trauma, operations

Palpebral conjunctiva – does ont swell during chemosis

Fornix – first to swell

Aqueous Layer - wetting agent of tear film

CORNEA

Contains no blood vessels Domeshaped transparent media Nourish to protect foreign debris 1/6 of the eye First refractive media of the eye 43d

LAYERS

Epithelium – contains nerve ending makes the cornea very sensitive. 50mmthick

Bowmans layer - a tough layer protein fibersof basement membrane right under the epithelium.› Stray layer of protein fibers (collagen)› It will scar injured

Stroma – (substantia propia) dominates the major part of cornea.› 90% of cornea’s thickness: 78% water

12% collagen› No blood vessels› Collagen – makes the cornea transparent.

Gives strengtht & elasticity› Keratocytes – specialized fibroblast

Produce collagen fibers 85% - 50% of correct thickness

Descemet’s layer – 10 – 12nm› Thin and strong sheet of tissue.Fusch dystrophy – dystrophy of Decemet’s layer

Endothelium – crucial layer› Barrier & pumps the cornea from getting

too wet› Thinnest of all layer› 5nm

Corneal epithelium- consist 5-6 layer cells› Tear film layers:a) Lipid oilb) Aqueous of lusterc) Mucous

3 types of cells

1. Surface cells – it has microvilli (for absorption) & traps fluid to prevent drying of cells.

2. Polyhydral cells – 2 to three lalyerso It has inter-communicating processes.

1. Columnar or Cuboidal or Basal Cell – inner cells w/c secretes and rest on base membrane

› 60 – 65 nm thickContents: a) Water (H2O) – 70 %b) Solids comprise of : DNA & RNA, Phospholipids &

Cholesterol & Proteinsc) ATP & Glycogend) Glutathionee) Ascorbic acid (Vit. C)f) Acetyl Cholinesterase

Bowman’s Membrane – condensation of corneal stroma

12um thick No capacity to regenerate

Corneal Stroma – thickest layer of cornea

− consist of collagen fibrils but loose attachment

Contents :1. Water 75-80%2. Solids (collagen) 20-25%

a) Keratocytes or cell bodies or corneal corpuscles

b) Collagen fibers – for transparency- Give shape, strength & elasticity- Skeleton of corneal stroma

c) Mucopolysaccharide – maintains hydration & transparency

Descemets Membrane – very elastic, resistant membrane prevent corneal perforation cause it make “bulging balloon like” (decemetocele).› Made up of collagen like structure or materials› Contains glycin and hydroproline› Production and secretion of endothelium› Can regenerate› 10 um thick› Common to rupture

Endothelium – bathe by aqueous humor.

o Responsible for deturgescence (transparency)o Controls the influx of aqueous humor

Corneal Barrier1. Lipid Barrier – prevent influx of lipid2. Occulodentes – covers to epithelium

Features of Cornea:› Slightly greater curvature than to rest of the globe› Horizontal Descemets is greater than the vertical

diameter› 11-12mm horizontal diameter › 9mm vertical diameter› At the center, more curve and thinner› At Peripheral, thicker and less curve

Shape of cornea› Anterior-elliptical› Posterior-circular