Anatomy of SCLERA

APPLIED ANATOMY OF SCLERA

Sclera forms the posterior five-sixth opaque part of the external fibrous tunic of the eyeball. Its whole outer surface is covered by Tenon's capsule. In the anterior part it is also covered by bulbar conjunctiva. Its inner surface lies in contact with choroid with a potential suprachoroidal space in

KERATOPLASTY

Keratoplasty, also called corneal grafting or corneal transplantation, is an operation in which the patient's diseased cornea is replaced by the donor's healthy

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

CORNEAL OPACITIES

The word 'corneal opacification' literally means loss of normal transparency of cornea, which can occur in many conditions. Therefore, the term 'corneal
opacity' is used particularly for the loss of transparency

CORNEAL OEDEMA

 Corneal oedema

The water content of normal cornea is 78 percent. It is kept constant by a balance of factors which draw water in the cornea (e.g., intraocular pressure and swelling pressure of the stromal matrix = 60 mm of Hg) and the factors which draw water out of

KERATOCONUS , KERATOGLOBUS , KERATOCONUS POSTERIOR

KERATOCONUS
Keratoconus (conical cornea) (Fig. 1) is a noninflammatory bilateral (85%) ectatic condition of cornea in its axial part. It usually starts at puberty and progresses slowly.

Etiopathogenesis. It is still not clear. Various theoriesproposed so far label it as developmental condition,degenerative condition, hereditary dystrophy and

POSTERIOR CORNEAL DYSTROPHIES

Cornea Guttata of vogt
This condition is characterised by drop-like excrescences involving the entire posterior surface of Descemet's membrane. These are similar to Hassal- Henle bodies which represent the age change and are mainly found in the

STROMAL CORNEAL DYSTROPHIES

Granular dystrophy
Also known as 'Groenouw type I, is an autosomal
dominant dystrophy characterised by milky-granular
hyaline deposits in anterior stroma. Intervening
stroma is

Anterior corneal dystrophies

ANTERIOR DYSTROPHIES

Epithelial basement membrane dystrophy
Also known as Cogan's microcystic dystrophy and
map-dot finger print dystrophy, is the most common
of all corneal dystrophies seen in working age adults.
The typical lesions, involving corneal

CORNEAL PATHOLOGICAL DEGENERATIONS

Fatty degeneration (Lipoid keratopathy)
Fatty degeneration of cornea is characterised by whitish or yellowish deposits. The fat deposits mostly consist of cholesterol and fatty acids. Initially fat deposits are intracellular but some become extracellular with necrosis of stromal

corneal AGE-RELATED DEGENERATIONS

Arcus senilis
Arcus senilis refers to an annular lipid infiltration of corneal periphery. This is an age-related change occurring bilaterally in 60 percent of patients between
40 and 60 years of age and in nearly all patients over the age of 80. Sometimes, similar changes occur in young persons (arcus juvenilis) which may or may
not be associated with hyperlipidemia. The arcus starts in the superior

CORNEAL DEGENERATIONS

Corneal degenerations refers to the conditions in which the normal cells undergo some degenerative changes under the influence of age or some
pathological

Tuberculous interstitial keratitis & Cogan's syndrome

 Tuberculous interstitial keratitis

The features of tubercular interstitial keratitis are
similar to syphilitic interstitial keratitis except that it

is more frequently unilateral and sectorial (usually
involving a lower sector of cornea).

Treatment consists of systemic antitubercular drugs,
topical steroids and cycloplegics.

Cogan's syndrome
This syndrome comprises the interstitial keratitis of
unkown etiology, acute tinnitis, vertigo, and
deafness. It typically occurs in middle-aged adults
and is often bilateral.

Treatment consists of topical and systemic corticosteroids. An early treatment usually prevents permanent deafness and blindness.
 

Syphilitic (luetic) interstitial keratitis

INTERSTITIAL KERATITIS
Interstitial keratitis denotes an inflammation of the corneal stroma without primary involvement of the epithelium or endothelium.

Causes. Its common causes are:
Congenital syphilis
Tuberculosis
Cogan's syndrome
Acquired syphilis
Trypanosomiasis
Malaria
Leprosy
Sarcoidosis

Syphilitic (luetic) interstitial keratitis
Syphilitic interstitial keratitis is associated more frequently (90 percent) with congenital

FILAMENTARY KERATITIS

It is a type of superficial punctate keratitis, associated with formation of corneal epithelial filaments.

Pathogenesis
Corneal filaments which essentially consist of a tag of elongated epithelium are formed due to aberrant epithelial healing. Therefore, any condition that leads
to focal epithelial erosion may produce filamentary

THYGESON'S SUPERFICIAL PUNCTATE KERATITIS

THYGESON'S SUPERFICIAL PUNCTATE KERATITIS a type of chronic, recurrent bilateral superficial punctate keratitis, which has got a specific clinical identity.

Etiology
Exact etiology is not known. 

• A viral origin has been suggested without any conclusion. 
• An allergic or dyskeratotic nature also has been suggested owing to its response to

SUPERIOR LIMBIC KERATOCONJUNCTIVITIS

Superior limbic keratoconjunctivitis of Theodore is the name given to inflammation of superior limbic, bulbar and tarsal conjunctiva associated with
punctate keratitis of the superior part of

PHOTO-OPHTHALMIA

Photo-ophthalmia refers to occurrence of multiple
epithelial erosions due to the effect of ultraviolet rays
especially from 311 to 290μ.
Causes
1. Exposure to bright light of a short circuit.
2. Exposure to a naked arc light as in industrial welding and cinema

NON-ULCERATIVE SUPERFICIAL KERATITIS

NON-ULCERATIVE SUPERFICIAL KERATITIS group includes a number of conditions of varied

etiology. Here the inflammatory reaction is confined to epithelium, Bowman's membrane and superficial stromal lamellae. Non-ulcerative superficial keratitis may present in two

MOOREN'S ULCER

 All about glaucoma surgery and treatment click here

The Mooren's ulcer (chronic serpiginous or rodent ulcer) is a severe inflammatory peripheral ulcerative keratitis.

Etiology
Exact etiology is not known. Different views are :
1. It is an idiopathic degenerative conditon.
2. It may be due to an ischaemic necrosis resulting from vasculitis of limbal vessels.
3. It may be due to the effects

ROSACEA KERATITIS

 all about glaucoma surgery and treatment click here

ROSACEA KERATITIS is defined as : Corneal ulceration is seen in about 10 percent cases of acne rosacea, which is primarily a disease of the sebaceous glands of the skin.

Clinical features
1. The condition typically occurs in elderly women in the form of facial eruptions presenting as butterfly configuration, predominantly involving
the malar and nasal

EXPOSURE KERATITIS

 all about glaucoma surgery and treatment click here

Normally cornea is covered by eyelids during sleep and is constantly kept moist by blinking movements during awaking. When eyes are covered insufficiently by the lids and there is loss of protective mechanism of blinking the condition of exposure

NEUROPARALYTIC KERATITIS

 (All about glaucoma surgery and treatment click here)

Neuroparalytic keratitis occurs due to paralysis of the sensory nerve supply of the cornea.
Causes

 
I. Congenital
1. Familial dysautonomia (Riley-Day syndrome)
2. Congenital insensitivity to Pain.
3. Anhidrotic ectodermal dysplasia.
II. Acquired
1. Following alcohol-block or electrocoagulation of Gasserian ganglion or section of the sensory root of trigeminal nerve for trigeminal neuralgia.
2. A neoplasm pressing on Gasserian

PROTOZOAL KERATITIS

ACANTHAMOEBA KERATITIS
Acanthamoeba keratitis has recently gained importance because of its increasing incidence, difficulty in diagnosis and unsatisfactory treatment.
Etiology
Acanthamoeba is a free lying amoeba found in soil, fresh water, well water, sea water, sewage and air. It exists in trophozoite and encysted forms.

Mode of infection. Corneal infection with acanthamoeba results from direct corneal contact with any material or water contaminated with the organism.
Following situations of

HERPES ZOSTER OPHTHALMICUS Treatment

  All about glaucoma surgery and treatment click here

Therapeutic approach to herpes zoster ophthalmicus should be vigorous and aimed at preventing severe devastating ocular complications and promoting rapid healing of the skin lesions without the formation of massive crusts which result in scarring of the nerves and postherpetic

HERPES ZOSTER OPHTHALMICUS

Herpes zoster ophthalmicus is an acute infection of Gasserian ganglion of the fifth cranial nerve by the varicella-zoster virus (VZV). It constitutes approximately 10 percent of all cases of herpes zoster.

Etiology
Varicella -zoster virus. It is a DNA virus and produces acidophilic intranuclear inclusion bodies. It is neurotropic in nature.

Mode of infection. The infection is contracted in childhood, which manifests as chickenpox and the child develops immunity. The virus then remains
dormant in the sensory ganglion of trigeminal nerve. It is thought that, usually in elderly people (can occur at any age) with depressed

HERPES SIMPLEX KERATITIS

Ocular infections with herpes simplex virus (HSV) are extremely common and constitute herpetic keratoconjunctivitis and iritis.
Etiology
Herpes simplex virus (HSV). It is a DNA virus. Its only natural host is man. Basically HSV is epitheliotropic but may become neurotropic.
According to different clinical and immunological
properties, HSV is of two types: HSV type I typically
causes infection above the

MYCOTIC CORNEAL ULCER

The incidence of suppurative corneal ulcers caused by fungi has increased in the recent years due to injudicious use of antibiotics and steroids.

Etiology
1. Causative fungi. The fungi which may cause corneal infections are :
i. Filamentous fungi e.g., Aspergillus, Fusarium, Alternaria, Cephalosporium, Curvularia and Penicillium.
ii. Yeasts e.g., Candida and Cryptococcus. (The fungi more commonly responsible for mycotic corneal ulcers are Aspergillus (most common), Candida and Fusarium).
2. Modes of infection
i. Injury by vegetative material such as crop leaf, branch of a

Marginal catarrhal ulcer

These superificial ulcers situated near the limbus are
frequently seen especially in old people.
Etiology
Marginal catarrhal ulcer is thought to be caused by a
hypersensitivity reaction to staphylococcal toxins. It
occurs in association with chronic staphylococcal
blepharoconjunctivitis. Moraxella and zzz  Haemophilus
are also known to cause such ulcers.
Clinical features
1. Patient usually presents with mild ocular irritation,
pain, photophobia and watering.

2. The ulcer is shallow, slightly infiltrated and often
multiple, usually associated with staphylococcal
conjunctivitis (Fig. 1).

Fig. 1. Marginal corneal ulcer in a patient with acute
conjunctivitis.

3. Soon vascularization occurs followed by
resolution. Recurrences are very common.
Treatment
1. A short course of topical corticosteroid drops
along with adequate antibiotic therapy often heals
the condition.
2. Adequate treatment of associated blepharitis and
chronic conjunctivitis is important to prevent
recurrences.