conjunctiva

Conjunctiva and sclera

Outline

• Conjunctiva

• sclera

Conjunctiva

• Introduction

• Surface anatomy

• Conjunctival layers

• Blood supply and drainage and nerve supply

What is conjunctiva?

• Vascularized mucous membrane that covers the anterior surface of the globe (bulbar and forniceal conjunctiva) and the posterior surface of the upper and lower eyelids (palpebral conjunctiva).

Combats infection

1. Highly vascular2. The different cell types can initiate and

participate in defensive inflammatory reaction

3. Immunocompetent cells that contribute a rich supply of immunoglobulins

4. The surface anatomy (microvilli) and biochemistry (enzymatic activity) enable that tissue to engulf and neutralize foreign particles, such as viruses

Surface anatomy

• The conjunctiva lines the posterior surface of the upper and lower lids and the anterior surface of the globe

• Forms superior fornix(8-10mm from limbus) and inferior fornix(8 mm from limbus)

• Caruncle and the plica semilunaris

Arrow pointing to the region of the superior fornix

Region of the inferior fornix (arrow)

Medical region of the eye showing the caruncle (C) and plica semilunaris (P)

Region of the lateral fornix (arrow) 14 mm from the limbus

Palpebral conjunctiva

Palpebral conjunctiva

• Starts from posterior end of the eyelid margin at the mucocutaneous junction

• Marked adherent to tarsal plate of lids

• Freely movable in fornices (forniceal conjunctiva)

Follicular reaction•identical to lymphoid follicles•viral and chlamydial infections as well as toxic conjunctivitis due to application of certain topical medications

Papillary reaction•chronic inflammatory cells such as lymphocytes and plasma cells•presence of blood vessels at their center•,Allergic conjunctivitis, Bacterial conjunctivitis,Contact lens wears,Superior limbic keratoconjunctivitis.

Bulbar conjunctiva

Bulbar conjunctiva

• limbus to the forniceal area.• thin and translucent.• loosely adherent to the sclera to allow the eye free

movement in all directions.• Approximately 3 mm from the limbus, the bulbar

conjunctiva, Tenon's capsule, and sclera become firmly attached, and the conjunctiva cannot be easily picked up.

This attachment is routinely encountered during the dissection of a limbal-based conjunctival flap in ocular surgery.

Conjunctival glands

42

6-8

2-5

2

Conjunctival layers

• The stratified epithelial layer

• The substantia propria layer

Conjunctival epithelium

• 2 to 4 layers-upper tarsal portion

• 6 to 8 layers-corneoscleral junction,

• 8 to 10 layers-conjunctival margins

Conjunctival epithelium

• Columnar in the fornix

• Cuboidal on the bulbar and tarsal conjunctiva

Types of cells

• Type I cells are the goblet cells• Type II cells are defined by the numerous

60- to 300-nm electron-dense granules• Type III cells are recognizable by their well

developed Golgi complex• type IV cells are characterized by rough

endoplasmic reticulum• Type V cells are identified by the high

content of mitochondria

Goblet cells

Goblet cells

• middle and superficial layers of the epithelium

• 25 by 25 μm

• 2.2 μL of mucus daily

Function of goblet cell mucus

• Preserve stability of tear film

• Local immunity

• Cleansing mechanism of the eye

• Traps cell debris, foreign bodies, and bacteria

• inflammatory response

Substantia propria

• Connective tissue layer

• Anti-infectious potential

• Numerous mast cells (6000/mm3), lymphocytes, plasma cells, and neutrophils are normally present in this layer.

Substantia propria

Superficial lymphoid layer•Not present at birth•Lymphocytes aggregrated into nodules

Deeper fibrous layer•thick, collagenous, elastic tissue and contains the vessels and nerves of the conjunctiva in addition to Krause's glands

Senile elastotic degeneration

Blood supply

Internal carotid artery ophthalmic artery

The palpebral branches of the nasal and lacrimal arteries of the lid

Anterior ciliary artery.

Venous drainage

• numerous than the arteries

• tarsal conjunctiva and the bulbar conjunctiva is directed to the palpebral veins

• superior and inferior ophthalmic veins

Lymphatic drainage

• a superficial plexus and a deeper plexus

• Ultimately as in the lids drains to the pre auricular and sub-mandibular lymph glands.

Nerve supply

Caruncle

• small, flesh-like body that lies to the medial side of the plica semilunaris

• stratified squamous epithelium similar to skin, but does not undergo keratinization

• Hair,sebaceous and sweat glands, goblet cells and accessory lacrimal glands similar to Krause's glands.

• Blood supply-superior palpebral arteries• Nerve supply-infratrochlear nerve• Lymphatic drainage-sub maxillary lymph

nodes

Plica semilunaris

• Fold of conjunctiva lying lateral to the caruncle

• cul-de-sac of approximately 2 mm in depth is formed when the globe is adducted

• nonexistent when the globe is abducted• nictitating membrane in lower vertebrates

Sclera

• Introduction

• Development

• Gross anatomy

• Layers

• Blood supply,drainage and nerve supply

Sclera

Introduction

• dense connective tissue that accounts for five sixths of the outer coat of the eyeball

• sklera mannix- hard membrane1.protects intraocular components from trauma,

light, and mechanical displacement2.withstands the considerable expansive force

generated by the intraocular pressure maintaining the shape of the globe

3.provides attachment sites for the extraocular muscles.

Prenatal development

• neural crest-mesodermal origin

• anterior to posterior and from inside to outside

5th week double-layered optic cup or neuroectoderm

6th week Differentiation into sclera and choroid anterior to equator

8th week Backward to the equator

12th week Posterior pole

4th month Scleral spur

5th month Lamina cibrosa

Postnatal development and age related characterstics

• Postnatal- relatively thin, bluish, distensible, small, and translucent

• Childhood and puberty-thicker, whiter, less distensible, larger, and more opaque

• Adult- poorly distensible,opaque or translucent depending on water content

• Elderly- less distensible,yellowish color and senile scleral plaques.

Gross anatomy

five sixths of the eyeball with a radius of curvature of 12 mm

Optic nerve

Equator=0.4-0.5mm

Behind insertionsInsertions=0.6mm

Thickness of sclera

Clinical applications

• The traumatic scleral rupture

• Strabismus surgery.

Tenons capsule• fascial sheath of the eyeball• extends anteriorly from the

limbus backward, envelopes the globe and fuses with the optic nerve dural sheath and with the sclera around the exit of the optic nerve

• supports the eyeball within the orbit

• permits the eyeball movement produced by the extraocular muscles

Sclera foramina

• anterior for the cornea

• posterior for the optic nerve

Anterior scleral foramen

• Sclera merges with the cornea at the anterior scleral foramen forming the corneoscleral junction or limbus

Fig: longitudinal section through the region of the corneoscleral junction showing the peripheral cornea, the sclera, the conjunctiva, and Tenon's capsule, canal of Schlemm, the trabecular meshwork, and the iris

Posterior scleral foramen

• The exit of the optic nerve• Lamina cribrosa-After piercing the lamina cribrosa, the axons of the

optic nerve become myelinated. One of the small perforations is larger than the rest and permits the passage of the central retinal artery and vein.

Layers of sclera

• Episclera

• Scleral stroma

• Lamina fusca

Episclera

• Superficial aspect of sclera

• bundles of collagen circumferentially arranged

• rich blood supply anteriorly

• thickest anterior to the rectus muscle insertions and becomes progressively thinner toward the back of the eye.

Scleral stroma

• bundles of collagen intermingled with fibroblasts, melanocytes, elastic fibers, proteoglycans, and glycoproteins

• variability in collagen fiber diameter, interlacing in bundles of collagen, and relative deficiency in water-binding substances accounts for the scleral dull-white color.

Lamina fusca

• Brown color due to melanocytes

• grooves for the passage of ciliary vessels and nerves (emissary canals)

• attached to the choroid by fine collagen fibers

Melanosis oculi

Blood supply

• Episclera-anterior and posterior ciliary arteries

• Scleral stroma-relatively avasculature structure

Venous drainage

• Episcleral collecting veins

• Vortex veins

Anterior ciliary veins

Nerve supply

• Rich in nerve supply

• Anterior sclera- long posterior ciliary nerves

• Posterior sclera- short posterior ciliary nerves

• Pain- inflammation, stretching due to oedema and movement of eye

Thank you

References

1. Fundamentals and principles of Ophthalmology,section 2,2014-2015, American Academy of Ophthalmology

2. External Disease and Cornea, Section 8, 2014-2015, American Academy of Ophthalmology

3. Duane's Foundations of Clinical Ophthalmology, Foundation volume 1

4. Jack J Kanski, Brad Bowling, Clinical Ophthalmology, seventh edition 2011

5. M.J. Roper- Hall, Stallard’s Eye Surgery, Seventh Edition, 1989

6. Parsons’ Diseases of the Eye, Twentieth Edition 20077. Internet