Conjunctiva and sclera

Anatomy of
conjunctiva and
sclera
DR SUHANA SHRESTHA
1ST YEAR RESIDENT
NEH(NAMS)

CONTENTS
A. Conjunctiva
Embryology
Gross anatomy
Histology
B. Sclera
Embryology
Gross anatomy
Histology

Embryology
◦ Closely related to development
of the eye lids.
◦ Eyelids develop as folds of
surface ectoderm above and
below the developing cornea
◦ Folds fuse at 3rd month
intrauterine life
◦ Closed space, conjunctival sac,
exists in front of cornea
◦ start separating at about 5th
month

• thin, translucent mucous membrane
• joins eyeball to the lids
• covers lids posteriorly
• reflected anteriorly at the fornix onto anterior surface of
eyeball
• contains 7μl of tear fluid
• can accommodate up to 30μl
• Instilled eye drops in excess of this volume either overflow
from the lids or drained by the lacrimal sac.
Gross anatomy

a. Marginal conjunctiva
oextends from lid margin to sulcus subtarsalis (2mm from
lid margin)
otransitional zone between skin and conjunctiva proper
othin non keratinized squamous epithelium
opuncta opens in this zone

Applied anatomy
o common site for foreign body: Sulcus subtarsalis
oconjunctival infection may spread into the nose and
vice versa.

b. Tarsal conjunctiva
Thin, translucent, very vascular
Intimately adherent to superior tarsus
lower tarsus adherent only to half of the tarsal width
Tarsal glands appear as yellowish streaks
Applied anatomy
Common site: follicular and papillary reaction
Due to strong adherance surgical repair is very
difficult here.

c. Orbital conjunctiva
oextends from upper border of tarsus to fornix
oloosely adherent to subadjacent non-striated
muscle (Muller muscle)

Bulbar conjunctiva
oin contact with eyeball
othin, translucent
olies loosely except at 1mm posterior to sclerocorneal limbus.
oseparated from anterior sclera by episcleral tissue and Tenon capsule.
omobile, allows ocular movements because it is attached adjacent structures by
areolar tissue
oLoosely attached to the Tenon capsule by connective tissue to sclera and fascia
bulbi
oInserted into the limbus

a. Scleral conjunctiva
oThin, transparent and loosely attached to sclera
oPermit vascularization of sclera and episcleral
vessels
oSeparated from sclera by episcleral vessel and
Tenon’s capsule

b. Limbal conjunctiva
o 3mm ridge of bulbar
conjunctiva around cornea
o closely attached to the sclera
and fascia bulbi
oThe conjunctiva limbus
(conjunctiva fuse to cornea) is
1mm anterior to the edge of
corneal limbus(junction
between cornea and sclera).

oThrough the vascularity of thin palpebral conjunctiva, diagnosis of anaemia is
possible
oAbout 3 mm from cornea, conjunctiva becomes closely adherent to fascia bulbi
and sclera, and the conjunctiva here is less mobile and a firm hold obtained in
surgery
Applied anatomy

3. Conjunctival fornix
o continuous annular cul-de-sac
o broken in medial side by caruncle and plica semilunaris
o transitional zone: joins palpebral and bulbar conjunctiva
o becomes enmeshed with the fibrous elements of levator aponeurosis and
Mulller muscle in upper eyelid and fibrous expansion of inferior rectus and
inferior tarsal muscle in the lower lid
o

Parts
a) Superior fornix:
◦ extends 8-10mm from limbus
◦ Extension of fascial sheath of levator and superior rectus is attached to
conjunctiva over superior fornix.
◦ Glands of Krause and Muller muscle are present.
◦ Foreign body in superior fornix is seen only after double eversion of upper lid.
b) Inferior Fornix:
o slightly below the lower border of lower tarsal plate to about 8 mm from
limbus,
c) Medial Fornix:
o shallow, lies between the caruncle and plica semilunaris dipped in pool of
tears.
d) Lateral Fornix:
o 14mm from lateral limbus

Clinical anatomy
If the fascial expansions of sheaths of levator and recti muscle loosen the fornix
will protrude in front.

Cells present in conjunctiva
1. Goblet cells:
◦ present between epithelium cells
◦ the chief source of tear mucin
◦ Occurs throughout the conjunctiva especially plica
semilunaris
◦ Most dense nasally and absent in the palpebral
mucocutaneous junction
2. Melanocytes: at limbus, fornix, caruncle and at the site of
entry of anterior ciliary vessels
3. Langerhans cells: in almost all parts of conjunctiva

o Consists of fine delicate connective tissue
o superficial lymphoid and deep fibrous layer
b. Substantia propria

Adenoid layer ( Lymphoid layer)
- has a large collection of lymphocytes
- highest concentration in fornices
- absent at marginal conjunctiva
- not present at birth, develop 2-3 months after birth.
-contains many lymphocytes predominantly T
lymphocytes , neutrophils, plasma cells and mast
cells.

Fibrous layer
- meshwork of collagenous and elastic fibres
-blends with underlying Tenon capsule in the region
of bulbar conjunctiva.
- thicker than lymphoid layer
-contains blood vessels, nerves, smooth muscles
and
accessory lacrimal glands

Follicles
◦ Yellowish white
◦ round elevations
◦ 1-2mm in diameter
◦ localized aggregation of lymphocytes in subepithelial adenoid layer.
◦ Vessels disappear toward the center
◦ Consist of lymphocytes, lymphoblasts and macrophages
◦ Physiologic folliculosis older chidren/ adolescent

o more prominent in inferior palpebral
conjunctiva except in trachoma.
o conjunctivital inflammations: Chlamydia,
adenovirus, HSV, Molluscum contagiosum

Papillae
oHyperplasia of the normal vascular system with glomerulus-like bunches of
capillaries growing into the epithelium in inflammatory conditions.
oTiny dome shaped nodules ,bumpy appearance.
oConsist of central core of hyperemic blood vessels that protrude upward ,
perpendicular to the tarsal plate surrounded by edema, inflammatory cells and
sometimes fibrosis.
oDepending on the size
◦ Micropapillae (<0.3mm)
◦ Small/ fine papillae (0.3-0.6mm)
◦ Medium papillae (0.6-1mm)
◦ Giant papillae (>1mm) Vernal and atopic conjunctivitis (contact
lens/prosthetic eyes)

Membrane and Pseudomembrane
True membrane:
◦ Infiltrate the superficial layers of
conjunctival epithelium
◦ Attempt to remove may cause tearing of
epithelium and bleeding
Pseudomembrane:
◦ Coagulated exudates adhrent to the
inflammed conjunctival epithelium
◦ easily peeled leaving the epithelium
intact

oAssociated with conjunctiva are 2 groups of lacrimal accessory glands:
1. Glands of Krause
about 42 in upper fornix
6-8 in lower fornix
lie in deep conjunctiva tissue
in upper fornix between palpebral part of lacrimal gland and upper tarsus
Ductile unite to a single duct before emptying into fornix
2. Glands of Wolfring
larger than of Krause
2 to 5 above the superior tarsus
within the lower edge of inferior tarsus

Glands of Henle
folds of mucus membrane between fornices and tarsal plates
Contain few goblet cells
Glands of Manz
encircle the limbus

Goblet cells
o throughout the conjunctiva between
epithelial cells
o unicellular glands
o secretes mucin
o arise from basal layer of epithelium
o round and oval in shape
o 10-20 µm in size
o up to 2.2 microlitre of mucus daily
o Few or absent in limbus area, numerous on
nasal side
o High in children and young adults

Applied anatomy
o Goblet cells: secrete mucin layer of tear film
o Accessory lacrimal glands of Krause and Wolfring: aqueous layer of tear film
o essential in maintaining corneal transparency

1)Palpebral conjunctiva and fornices:
two palpebral arches (viz. marginal and
peripheral )
2)Bulbar conjunctiva: anterior and
posterior conjunctival arteries
Arterial supply

The palpebral arches:
a. Marginal arch
• medial plus lateral palpebral arteries
• runs 3mm from lid margin
• between tarsal plate and orbicularis
oculi muscle
Arterial supply

b. Peripheral arch
• branch of medial palpebral arteries
• Lies 4mm from lid margin
• supply superior and inferior
conjunctival fornices then form
posterior conjunctival arteries, supply
bulbar conjunctiva
• continue forward upto limbus where
they anastomose with anterior
conjunctival arteries, which are
branches of anterior ciliary arteries

Lymphatic drainage
o From lateral side: preauricular and
parotid lymph node.
oFrom medial side: submandibular
lymph node.

Bulbar conjunctiva
 long ciliary nerves (branch of nasociliary nerve, a branch of ophthalmic
division of trigeminal nerve)
Nerve supply

Nerve supply
o Superior palpebral conjunctiva and
superior fornix: frontal and lacrimal
branches of ophthalmic division of
trigeminal nerve
o Inferior palpebral conjunctiva and
inferior fornix: laterally- lacrimal nerve
medially - infraorbital nerve

Caruncle
o Soft pink, fleshy ovoid body, 5mm x 3mm
oContains lacus lacrimalis
o Situated in lacus medial to plica semilunaris
omodified skin: few fine colorless hair, sebaceous glands,
sweat glands, goblet cells
oGlands of Krause often conspicuous at center of caruncle
oAttached to inferomedial side of plica semilunaris
oNonkeratinized stratified squamous epithelium
oBlood supply – superior medial palpebral arteries
oLymphatics: submandibular lymph nodes
oNerve supply – infratrochlear nerve
o

Plica semilunaris: nictitating membrane/ 3rd eyelid
oNarrow, pinkish, highly vascular,
crescent vertical fold of conjunctiva
o lateral and partly behind the
caruncle at the medial angle of the
eye
oExtends upto middle of inferior
fornix inferiorly
oEpithelium resembles bulbar
conjunctiva, rich in goblet cells
oStroma: fat and nonstriated muscle

Physiology
oSecretes mucin and aqueous component of tear film.
oHighly vascular: supplies nutrition to the peripheral cornea.
oAqueous veins drains from anterior chamber maintenance of IOP.
oLymphoid tissue helps in combating infections.
oBasic secretion—reflex secretion.

Applied anatomy
o Enormous potential for combating infection because:
(1) highly vascular
(2) different cell types initiate defensive inflammatory reaction
(3) rich supply of immunoglobulins
(4) engulf and neutralize foreign particles, such as viruses.
oThe bulbar surfaceloosely adherent  used to great advantage in glaucoma
surgery.
o Capacity to heal rapidly ensures the success of many surgical procedures.

o Conjunctival vessels Sickle cell anemia
o Scleral icterus Jaundice
o Bitot's spot  Vitamin A deficiency
Pathognomic signs in conjunctiva:

Keratinization of conjunctiva:
 Stevens-Johnson syndrome
Cicatricial pemphigoid
Vitamin A deficiency

Pingecula: degeneration of
conjunctival stroma.
Pterygium: Traingular fibrovascular
subepithelial ingrowth of
degenerative bulbar conjunctival
tissue over the limbus to the cornea.
Pseudopterygium: band of
conjunctiva adhering to an area of
compromised cornea at its apex

o a fold of redundant,nonoedematous
conjunctiva interposed between the globe
and the eyelid, protruding over the lid
margin
oCause: unknown
oMay associate with aging
o Chronic inflammation
Conjunctivochalasis

Concretion:
• minute, hard, yellow –white spots.
• Formed due to accumulation of
epithelial cells and traped debris
• Eg: aging, chronic inflammation

Fascia Bulbi/Tenons capsule
oThin membrane that envelopes the
eyeball and separates it from the orbital
fat.
oForms the socket for the eyeball
oDense, elastic and vascular connective
tissue that surrounds the globe (except
over the cornea)
oBegins at perilimbal sclera, extends to
the optic nerve, and fuses with the dural
sheath and the sclera.

o two surfaces Inner surface and Outer surface
a. Inner surface: smooth, shiny and is separated from the outer surface of
the sclera  Episcleral space
b. Outer surface: anteriorly, firmly attached to the sclera about 1.5mm posterior to
the limbus. Posteriorly, it fuses with the meninges around the optic nerve and
the sclera around the exit of the optic nerve.

o The fascial sheath is pierced by
1. The ciliary nerves and vessels
2. The vortex vein
3. Tendons of all six extrinsic muscles of the eye.
At the site, where the tendons pierce the fascia, the sheath
is reflected along the tendons of these muscles to form 
Tubular sleeve.

o Inferiorly: thickened to form medial and
lateral check ligaments
o Inferiorly the hammock like
arrangement of the facial sheaths is
known as suspensory ligament of
lockwood

MAIN FUNCTION
◦ To position and support the globe within the orbital
cavity.
◦ To permit the actions of extrinsic muscles to produce
movement of eyeball.

Applied anatomy
o During enucleation of the eyeball the fascial sheath should be preserved to
serve as a socket for the prosthesis
o Close relationship exists between the suspensory ligament of lockwood and
the inferior rectus and the inferior oblique muscle making operations on these
muscles difficult.
o Even after extensive removal of maxilla, eyeball does not sag down because
the suspensory ligament is strong enough to provide the eyeball with adequate
support from below.
o Extension of the fascial sheath through the orbital fat to the bony walls of
orbital cavity assists the orbital septum in preventing herniation of fat into the
lids.

Embryology
o Differentiates from neural crest cells and
mesoderm at 7 week
o Majority arises from neural crest that surround
the optic cup of neuroectoderm.
o Small portion arise from mesoderm

o forms posterior 5/6th of fibrous external tunic of eyeball
o Tough and protects intraocular contents from injury and mechanical
displacement
o Contains almost entirely of collagen(type I and III)
o relatively avascular
o Prevents deformation of globe
Gross anatomy

The sclera
o viscoelastic
o Elastic – rapid but brief stretching
o Viscid – slow stretching
o IOP causes a stretching of scleral collagen, hence it is always under slight
tension

o Infantile glaucoma: viscid slow stretch in response to changes in IOP
results in buphthalmic globe
o Progressive myopia: expansion and thinning of sclera is seen
Applied anatomy
o Staphyloma: Localised bulging of
weak and thin outer tunic of
eye(cornea or sclera)
Lined by uveal tissue which shine
through the defect.

Gross anatomy
The sclera is opaque and white due to
◦ high (68%) water content
◦ disorderly array of transverse and oblique collagen (75%) fibers that make
up its coat.
◦ the greater variation in collagen fibril separation and diameter
◦ the greater degree of fibril interweaving in the sclera.
Usually opaque, although some diffuse light does enter globe through sclera

o Sclera is designed for strength and not clarity.
o If the water content of sclera is reduced below 40%, it begins to appear clear like the
cornea
o healing of wounds, can take months or years to complete.
o The interior surface of the sclera is brown, due to melanocytes.
o scleral structure is protected by episclera

Applied anatomy
1. Change in colour of sclera: aging and disease
o children: blue color due to underlying choroid
shown through the thin sclera
o elderly: yellowish color due to fatty deposits
2. Blue sclera
◦ generalised: in newborns (congenital)
◦ focal: beneath insertions of recti
◦ during surgery – transient effect of drying
3. Jaundice: yellow discolouration is due to
deposition of bilirubin

Blue sclera
A. Congenital disease associated with blue sclera are
◦ osteogenesis imperfecta
◦ Ehlers- Danlos syndrome
◦ Pseudoxanthoma elasticum and other collagen diseases
◦ Marfan syndrome
In these sclera is thin and blue due to defective collagen synthesis
B. Acquired
eg iron deficiency anemia

Dimensions
oAnteroposterior diameter:
at birth : 16-17 mm
at 3yrs : 22.5mm
oAverage coronal diameter of adult:
(>/=13 years) 22-24mm

Dimensions
Thickness:
Thickest : 1mm near the optic nerve
head
Thinnest : 0.3mm near insertions of
rectus muscles
At equator : 0.4 -0.5 mm thick
Anterior to muscle insertion: 0.6mm
thick

Applied anatomy
1. Thin sclera: Strabismus (tendon recession) and retinal detachment
surgery require careful placement of sutures.
2. Most common sites for scleral rupture durin blunt trauma:
• in the superonasal quadrant, near the limbus
• in a circumferential arc parallel to the corneal limbus opposite to the site
of impact
• behind the insertion of rectus muscle

Canal of Schlemm: circular canal posterior to
the limbus and lies within the sclera

Special region of sclera
Scleral sulcus
◦ An indentation on the inner most
surface of the anterior of sclera
near limbus.
Sclera spur
◦ a circular flange of anterior most
part of sclera which lies deep to
Schlemm’s canal.
◦ Prevents Schlemm’s canal collapse
by ciliary muscle.

Lamina cribrosa
oReinforces the globe at its weakest point
o located in the posterior part of sclera
ohelps to preserve a pressure gradient between the extraocular and intraocular
spaces
oIn the lamina cribrosa the RGC axons are most vulnerable to IOP-related stress
and strain
oconcave at intraocular aspect
oholes in the network remain relatively aligned with each other providing
unobstructed passage for bundle of nerve fibres

Function: lamina cribrosa
◦ Exit for ganglion cell axons and the central retinal vein
◦ allow the central retinal artery to enter the intraocular space, and
◦ to stabilize the intraocular pressure by forming a barrier between the intraocular
space and the extraocular space.
◦ barrier function: it prevents a major leakage of aqueous humor from the
intravitreal space into the retrobulbar CSF space surrounding the retrobulbar
part of the optic nerve.
◦ forms the border between the intraocular space (higher pressure) and the
retrobulbar space (lower pressure), a pressure gradient exists across the lamina
cribrosa, which is the intraocular pressure minus the pressure in the retrobulbar
cerebrospinal fluid space. In ocular diseases, the pressure on one or both sides
of the lamina cribrosa is either abnormally high or abnormally low.

o The superior and inferior regions of the lamina cribrosa, which exhibit greater
pore size and less dense connective tissue, are more susceptible to axonal
damage.
oThe arcuate retinal ganglion cell axons, which pass through these regions, are
damaged first in early glaucoma.
o Myopic eyes cause optic disc tilt and torsion, parapapillary atrophy and thus it
causes axonal injury in glaucoma

Sclera is pierced by two potential openings
anterior scleral foramen
posterior scleral foramen

a. Anterior scleral foramen
o here sclera anatomically merges with the cornea
oBoth the internal and external margin of sclera at the sclerocorneal junction
project more anteriorly than the main body forming sclera- concave
cirumferential groove called Internal scleral sulcus

Posterior scleral foramen
oan exit for the optic nerve from the globe
oOptic nerve located 3mm medial to midline and 1mm above to posterior pole.
oThe Canal is a truncated cone with internal opening diameter of 1.5-2mm and
external opening 3-3.5mm

Emissaria
Channels through which vessels and nerves pass through the sclera
1. Anterior emissaria
2. Middle emissaria
3. Posterior emissaria

Anterior emissaria
• 3-4mm away from the limbus
• provides a passage for
• Anterior ciliary arteries
• Anterior ciliary veins
• Aqueous veins
• Ciliary nerves.

Middle emissaria
o 4-7 mm posterior to the equator
o These channels lie behind the
equator
o transmit
vortex veins(4 in number)locate at
1,11,5,7 o’clock
& accessory veins(1-2 mm from the
main vein)

Posterior emissaria
Posterior channels transmit the
long and short ciliary nerves and vessels
Pierce sclera about 3-4 mm from optic nerve

Clinical anatomy
• Wherever the nerves and vessels pierce
the sclera, it provides pathway for spread
of intraocular tumors. Eg.Extraocular
extension of malignant melanoma of the
choroid via. Middle emissaria.
• ciliary nerve branches supplying the
cornea sometimes leave the sclera to
form loops posterior to the nasal and
temporal limbus, called Axenfeld loops,
which are sometimes pigmented and,
mistaken for uveal tissue or malignant
melanoma.

◦ Outermost layer consisting of loose connective tissue
◦ thin, dense vascularized
◦ progressively thinner towards the back of eye
◦ contains fibroblasts, macrophages and lymphocytes
◦ Connected to Tenons capsule by loose connective tissue
◦ Blood supply: anterior ciliary arteries
a. Episclera

oEpiscleral veins may dilate due to
increase in pressure( normal 8-10mmHg)
in varity of diseases like glaucoma
oEpisclera is rich in blood supply and
results in rapid healing of surgical
incisions
Clinical Anatomy

b. Scleral stroma
◦ Dense fibrous tissue intermingled with fine elastic fibres
◦ Collagen fibres type I and III
◦ Irregular arrangement of collagen fibrils responsible for scleral opacity
◦ In between collagen fibrils few elongated fibroblast and occasional
melanocyte seen.
◦ moderate amount of ground substance

c. Lamina fusca
◦ Innermost layer of sclera
◦ Faintly brown due to melanocytes
◦ Has many grooves caused by passage of ciliary vessels and nerves
◦ Perichoroidal space separates it from choroid
◦ blends imperceptibly with the suprachoroidal and supraciliary lamellae of
the uvea.
◦ The collagen fibers in this portion of the sclera branch and intermingle with
the outer ciliary body and choroid.

o Sclera is avascular except for
intrascleral vascular plexus
(posterior to limbus) and episcleral
vessels
o Episcleral plexus: formed by
anterior ciliary arteries
Gives rise to superficial and deep
plexuses
Superficial plexus runs beneath the
Tenon capsule in a radial pattern
(Episcleritis)
Deep plexus rests on the surface of
the sclera (Scleritis)
Blood supply

Nerve supply
o Posterior portion: short ciliary nerves
o Anterior portion : two long ciliary nerves

Applied anatomy
o Profuse sensory innervation of sclera results in dull aching pain
associated with inflammations of sclera.
o The pain is worsened with ocular movement.

References
1. American Academy of Ophthalmology BCSC Course (2019-20):
Fundamentals and principles of Ophthalmology
2. Anthony J Bron, Ramesh C Tripathi, Brenda J Tripathi, Wolff’s
Anatomy of the eye and orbit, 8th edition.
3. Snell, Richard s. and Michael A. lemp, Clinical anatomy of the
eye,2nd Edition, India:Blackwell science,1998.
4. Sihota R. Tandon R. Parsons Diseases of the Eye. 23rd edition.
Haryna: Elsevier; 2020.

Conjunctiva and sclera

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