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

ADULT INCLUSION CONJUNCTIVITIS

Adult Inclusion conjunctivitis is a type of acute follicular conjunctivitis associated with mucopurulent discharge. It usually affects the
sexually active young adults.

Etiology
Inclusion conjunctivitis is caused by serotypes D to
K of Chlamydia trachomatis. The primary source of
infection is urethritis in males and cervicitis in

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

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

TRACHOMA Symptoms & Signs

Symptoms

• In the absence of secondary infection, symptoms are minimal and include mild foreign body sensation in the eyes, occasional lacrimation, slight stickiness of the lids and scanty mucoid discharge.
• In the presence of secondary infection, typical symptoms of acute mucopurulent conjunctivitis develop.

Signs
A. Conjunctival signs
1. Congestion of upper tarsal and forniceal conjunctiva.

2. Conjunctival follicles. Follicles (Fig. 1 and Fig.2) look like boiled

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 

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 

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

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

Refractive surgery for presbyopia

Refractive surgery for presbyopia, still under trial,
includes :

• Monovision LASIK, i.e., one eye is corrected for distance and other is made slightly near sighted.
• Monovision conductive keratoplasty (CK) is being considered increasingly to correct presbyopia in one eye. Principle is same as for correction of hypermetropia.
• Scleral expansion procedures are being tried, but results are controversial.
• LASIK-PARM i.e., LASIK by Presbyopia Avalos Rozakis Method is a technique undertrial in which the shape of the

CONTACT LENSES

what is contact lens

Contact lens is an artificial device whose front surface
substitutes the anterior surface of the cornea.
Therefore, in addition to correction of refractive error,
the irregularities of the front surface of cornea can
also be corrected by the contact lenses.
Parts, curves, and nomenclature for contact lens
To understand the contact lens specifications
following standard nomenclature has been recommended
(Fig. 1).

Fig. 1. A contact lens.

1. Diameters of the lens are as follows :
i. Overall diameter (OD) of the lens is the linear measurement of the greatest distance across the physical boundaries of 

INSUFFICIENCY OF ACCOMMODATION

(continue  ACCOMMODATION ANOMALIES) Insufficiency of accommodation

The term insufficiency of accommodation is used when the accommodative power is significantly less than the normal physiological limits for the patient's
age. Therefore, it should not be confused with presbyopia in which the physiological insufficiency of accommodation is normal for the patient's age.

Causes
1. Premature sclerosis of lens.
2. Weakness of ciliary muscle due to

Accommodation eye

Definition. As we know that in an emmetropic eye, parallel rays of light coming from infinity are brought to focus on the retina, with accommodation being at rest. However, our eyes have been provided with a unique mechanism by which we can even focus the
diverging rays coming from a near object on the retina in a bid to see clearly (Fig. 1).
This mechanism is called accommodation. In it there occurs increase in

 FIG 1 Effect of accommodation on divergent rays
entering the eye

Fig. 2. Changes in the crystalline lens during
accommodation.

the power of crystalline lens due to increase in the
curvature of its surfaces (Fig. 2).
At rest the