VASCULARIZATION OF CORNEA

Normal cornea is avascular except for small capillary loops which are present in the periphery for about 1 mm. In pathological states, it can be invaded by
vessels as a defence mechanism against the disease or injury. However, vascularization interferes with corneal

Pathology of sloughing corneal ulcer and formation of anterior staphyloma

When the infecting agent is highly virulent and/or body resistance is very low, the whole cornea sloughs with the exception of a narrow rim at the margin and
total prolapse of iris occurs. The iris becomes inflamed and exudates block the pupil and cover the iris surface; thus a false cornea is formed. Ultimately these exudates organize and form a thin fibrous layer over which the conjunctival or corneal epithelium rapidly grows and thus a pseudocornea is

ULCERATIVE KERATITIS

Inflammation of the cornea (keratitis) is characterised by corneal oedema, cellular infiltration and ciliary congestion.

ULCERATIVE KERATITIS
Corneal ulcer may be defined as discontinuation in normal epithelial surface of cornea associated with necrosis of the surrounding corneal tissue.
Pathologically it is characterised by oedema and cellular infiltration. Common types of corneal ulcers are described below.INFECTIVE KERATITIS
BACTERIAL CORNEAL ULCER
Being the most anterior part of eyeball, the cornea is exposed to atmosphere and hence prone to get infected easily. At the same time cornea is protected
from the day-to-day minor infections by the

Cornea congenital anomalies

Megalocornea
Horizontal diameter of cornea at birth is about 10 mm and the adult size of about 11.7 mm is attained by the age of 2 years. Megalocornea is labelled when the horizontal diameter of cornea is of adult size at birth or 13 mm or greater after the age of 2 years. The cornea is usually clear with normal thickness and vision. The condition is not progressive. Systemic association include Marfan's, Apert, Ehlers Danlos and Down syndromes.

Differential diagnosis
1. Buphthalmos. In this condition IOP is raised and the eyeball is enlarged as a whole. The enlarged cornea is usually associated with

cornea anatomy

APPLIED CORNEA ANATOMY
The cornea is a transparent, avascular, watch-glass like structure. It forms anterior one-sixth of the outer fibrous coat of the eyeball.

Dimensions

• The anterior surface of cornea is elliptical with an average horizontal diameter of 11.7 mm and vertical diameter of 11 mm.
• The posterior surface of cornea is circular with an average diameter of 11.5 mm.
• Thickness of cornea in the centre is about 0.52 mm while at the periphery it is 0.7 mm.
• Radius of curvature. The central 5 mm area of the cornea forms the powerful

Trachoma Management

Management of trachoma should involve curative as
well as control measures.

A. Treatment of active trachoma
Antibiotics for treatment of active trachoma may be
given locally or systemically, but topical treatment is
preferred because:

• It is cheaper,
• There is no risk of systemic side-effects, and

TRACHOMA Complications & Diagnosis

Complications
The only complication of trachoma is corneal ulcer
which may occur due to rubbing by concretions, or
trichiasis with superimposed bacterial infection.

Diagnosis
A. The clinical diagnosis of trachoma is made from
its typical signs; at least two sets of signs should be
present out of the following:

Grading of trachoma

McCallan's classification
McCallan in 1908, divided the clinical course of the
trachoma into following four stages:

• Stage I (Incipient trachoma or stage of infiltration). It is characterized by hyperaemia of palpebral conjunctiva and immature follicles.
• Stage II (Established trachoma or stage of florid infiltration). It is characterized by appearance of mature

what is trachoma ?

Trachoma (previously known as Egyptian ophthalmia) is a chronic keratoconjunctivitis, primarily affecting the superficial epithelium of
conjunctiva and cornea simultaneously. It is characterised by a mixed follicular and papillary response of conjunctival tissue. It is still one of the
leading causes of 

CHLAMYDIAL CONJUNCTIVITIS

Chlamydia lie midway between bacteria and viruses,
sharing some of the properties of both. Like viruses,
they are obligate intracellular and filterable, whereas
like bacteria they contain both

ANGULAR CONJUNCTIVITIS

ANGULAR CONJUNCTIVITIS is a type of chronic conjunctivitis characterised by mild grade inflammation confined to the conjunctiva and lid margins near the angles (hence the name) associated with maceration of the surrounding skin.

Etiology
1. Predisposing factors are same as for 'simple chronic conjunctivitis'.
2. Causative organisms. Moraxella Axenfeld is the commonest causative organism. MA bacilli are placed end to end, so the disease is also called

CHRONIC CATARRHAL CONJUNCTIVITIS

Chronic catarrhal conjunctivitis’ also known as
‘simple chronic conjunctivitis’ is characterised by
mild catarrhal inflammation of the conjunctiva.

Etiology
A. Predisposing factors
1. Chronic exposure to dust, smoke, and chemical
irritants.
2. Local cause of irritation such as trichiasis,
concretions, foreign body and seborrhoeic scales.
3. Eye strain due to 

PSEUDOMEMBRANOUS CONJUNCTIVITIS

It is a type of acute conjunctivitis, characterised by
formation of a pseudomembrane (which can be easily
peeled off leaving behind intact conjunctival
epithelium) on the conjunctiva.

Etiology
It may be caused by following varied factors:
1. Bacterial infection. Common causative organisms
are Corynebacterium diphtheriae of low virulence,
staphylococci, streptococci, H. influenzae and N.
gonorrhoea.
2. Viral infections such as

ACUTE MEMBRANOUS CONJUNCTIVITIS

It is an acute inflammation of the conjunctiva,
characterized by formation of a true membrane on the
conjunctiva. Now-a-days it is of very-very rare
occurrence, because of markedly decreased
incidence of diphtheria. It is because of the fact that
immunization against diptheria is very effective.

Etiology
The disease is typically caused by Corynebacterium
diphtheriae and occasionally by virulent type of

ACUTE MUCOPURULENT CONJUNCTIVITIS AND OTHER TYPES OF CONJUNCTIVITIS

CLINICAL TYPES OF BACTERIAL
CONJUNCTIVITIS

Depending upon the causative bacteria and the
severity of infection, bacterial conjunctivitis may
present in following clinical forms:

•  Acute catarrhal or mucopurulent conjunctivitis. (DISCUSSED BELOW)
•  Acute purulent conjunctivitis (visit link)
•  Acute membranous conjunctivitis (visit link)
•  Acute pseudomembranous conjunctivitis (visit link)
•  Chronic bacterial conjunctivitis (visit link)
•  Chronic angular conjunctivitis (DISCUSSED IN COMING POSTS)

ACUTE MUCOPURULENT CONJUNCTIVITIS
Acute mucopurulent conjunctivitis is the most
common type of 

INFECTIVE & BACTERIALCONJUNCTIVITIS

Infective conjunctivitis, i.e., inflammation of the
conjunctiva caused by microorganisms is the
commonest variety. This is in spite of the fact that
the conjunctiva has been provided with natural
protective mechanisms in the form of :

•  Low temperature due to exposure to air,
•  Physical protection by lids,
•  Flushing action of tears,
•  Antibacterial activity of lysozymes and
•  Humoral protection by the tear immunoglobulins.

 BACTERIAL CONJUNCTIVITIS
There has occurred a relative decrease in the
incidence of bacterial conjunctivitis in general and
those caused by gonococcus and corynebacterium
diphtheriae in particular. However, in developing
countries it still continues to be the commonest type
of conjunctivitis. It can occur as sporadic cases and
as epidemics. Outbreaks of bacterial conjunctivitis
epidemics are quite frequent during monsoon season.

Etiology
A. Predisposing factors for bacterial conjunctivitis,
especially epidemic forms, are flies, poor hygienic
conditions, hot dry climate, poor sanitation and dirty
habits. These factors help the

Blood supply of conjunctiva

Arteries supplying the conjunctiva are derived from
three sources (Fig. 1):

(1) peripheral arterial arcade of the eyelid;
(2) marginal arcade of the eyelid; and
(3) anterior ciliary arteries.

• Palpebral conjunctiva and fornices are supplied by branches from the peripheral and marginal arterial arcades of the eyelids.
• Bulbar conjunctiva is supplied by two sets of vessels: the posterior conjunctival arteries which are branches from the

Structure of conjunctiva

Histologically, conjunctiva consists of three layers
namely, (1) epithelium, (2) adenoid layer, and (3)
fibrous layer (Fig. 1 below ).


1. Epithelium. The layer of epithelial cells in
conjunctiva varies from region to region and in its
different parts as
follows:

• Marginal conjunctiva has 5-layered stratified squamous type of epithelium.
• Tarsal conjunctiva has

ANATOMY of Conjunctiva

The conjunctiva is a translucent mucous membrane
which lines the posterior surface of the eyelids and
anterior aspect of eyeball. The name conjunctiva
(conjoin: to join) has been given to this mucous
membrane owing to the fact that it joins the eyeball
to the lids. It stretches from the lid margin to the
limbus, and encloses a complex space called
conjunctival sac which is open in front at the
palpebral fissure.

Parts of conjunctiva
Conjunctiva can be divided into three parts (Fig. 1):
1. Palpebral conjunctiva. It lines the lids and can be
subdivided into marginal, tarsal and orbital
conjunctiva.
i. Marginal conjunctiva extends from the

Refractive surgery for astigmatism

Refractive surgical techniques employed for myopia
can be adapted to correct astigmatism alone or
simultaneously with myopia as follows:
1. Astigmatic keratotomy (AK) refers to making
transverse cuts in the mid periphery of the steep
corneal meridian (Fig. 1).

Fig. 1. Astigmatic keratotomy. (A) showing flat and deep meridians of cornea; (B) paired transverse incisions to flattern
the steep meridian; (C) showing correction of astigmatism after astigmatic keratotomy.

AK can be performed
alone (for astigmatism only) or along with RK (for
associated myopia).
2. Photo-astigmatic refractive keratotomy (PARK)
is performed using