Diseases of the Conjunctiva

CONJUNCTIVITIS

Normal flora of the conjunctiva include coagulase negative staphylococcus and diphtheroids.

Common causative organisms for different types of conjunctivitis are:

• Purulent (hyperacute conjunctivitis) : Gonococci, Neisseria meningitidis
• Angular conjunctivitis : Moraxella-Axenfeld (Haemophilus lacunatum)
• Swimming pool conjunctivitis (inclusion conjunctivitis) : Chlamydia tracho­matis serotypes D to K
• Epidemic kerato-conjunctivitis  : Adenovirus type 8,19
• Acute haemorrhagic conjunctivitis (Apollo conjunctivitis) : Enterovirus type 70
• Beal’s conjunctivitis (Pharyngoconjunctival fever) : Adenovirus type 3 & 7
• Egyptian ophthalmia (Trachoma) : Chlamydia tracho­matis serotype A,B, Ba, C
• Acute membranous conjunctivitis : Corynebacterium diphtheriae and streptococcus haemolyticus
• Ophthalmia neonatorum : Gonococci, chlamydia, trachomatis (D to K), staphylococci, herpes simplex
• Acute follicular conjunctivitis : Adenovirus, chlamydia oculogenitalis, herpes simplex
• Ophthalmia nodosa : Caterpillar hair

Bacterial conjunctivitis

• Staphylococcus aureus is the most common cause of bacterial conjunctivitis and blepharo-conjunctivitis.
• Pneumococcal conjunctivitis is usually associated with petechial subconjunctival haemorrhages
• Streptococcus pyogenes usually produces pseudomembranous conjunctivitis
• Haemophilus influenzae (H. aegyptius or Koch- Weeks Bacillus) classically causes epidemics of mucopurulent conjunctivitis (red-eye)
• Moraxella-Axenfeld bacillus is most common cause of blepharoconjunctivitis
• Neisseria gonorrhoeae produce acute purulent conjunctivitis.
• Corynebacterium diphtheriae causes acute membranous conjunctivitis.

Acute mucopurulent conjunctivitis

• Most common type of acute bacterial conjunctivitis.
• Common causative organisms: Staphylococcus aureus (commonest), Haegyptius (Koch-Weeks bacillus), pneumococcus and streptococcus.

Acute purulent conjunctivitis

• Commonest causative organism is gonococcusDiseases of the Conjunctiva, rarely it may be staphylococcus aureus or pneumococcus.
• May be associated with urethritis and arthritis.
• In gonococcal conjunctivitis, when cornea is not involved, a single IM injection of ceftriaxone 1 gm is effective.
• When cornea is involved a 5 days course of ceftriaxone 1-2 gm daily is needed.

Acute membranous conjunctivitis

• A rare disease, typically caused by corynebacterium diphtheriae and occasionally by virulent type of streptococcus haemolyticus.
• Corneal ulceration is frequent complication. The bacteria may even invade the intact corneal epithelium.

Angular conjunctivitis

• Caused by Moraxella-Axenfeld diplococci, so also called as diplobacillary conjunctivitis.
• Source of infection is usually nasal cavity.
• M. A. bacillus produces proteolytic enzyme which macerates epithelium of the conjunctiva, lid margin and the skin surrounding angles of the eye.

Chlamydial conjunctivitis

Chlamydia lie midway between bacteria and viruses. Like viruses, they are obligate intracellular and filterable, whereas like bacteria they contain both DNA and RNA, divide by binary fission and are sensitive to antibiotics.

Trachoma

• Also called Egyptian ophthalmia is caused by chlamydia trachomatis; serotypes, A,B,Ba and C are associated with hyperendemic (blinding) trachoma.
• Chlamydia trachomatis is epitheliotropic and produces intracytoplasmic inclusion bodies called
H. P. (Halberstaedter Prowazeke) bodies.
• Most common mode of trachoma spread is through fomites and flies.
• Prevalence of trachoma is worldwide (affecting about 500 million people), but is highly prevalent in North-Africa, Middle-East and certain regions of South-East Asia.
• It is responsible for 15-20 percent of the world’s blindness.
• Incubation period varies from 5 lo 21 days.
• Pothognomic features of trachoma follicles are presence of Leber cells and areas of necrosis.
• Herbert follicles refer to typical trachoma follicles present in the limbal area.
• Trachomatous pannus initially is seen in the upper part. In progressive pannus infiltration is ahead of vascularization while in regressive pannus it stops short of limbus.

McCallan classification of trachoma

• Stage I-Hyperaemia of upper palpebral conjunctiva with immature follicles
• Stage II – Mature follicles, papillae and progressive pannus
• Stage III – Conjunctival scarring, Herbert’s pit
• Stage IV – Stage of sequelae

WHO classification (FISTO)

• Trachomatous inflammation follicular (TF): Five or more follicles (each bigger than 0.5 mm) on the upper tarsal conjunctiva.
• Trachomatous inflammation intense (TI): Inflammatory thickening of the upper tarsal conjunctiva obscures more than half of the normal deep tarsal vessels.
• Trachomatous scarring (TS): Scarring on the tarsal conjunctiva.
• Trachomatous Trichiasis (TT): When at least one eye lash mbs the eye.
• Trachomatous corneal opacity (CO): Easily visible corneal opacity present over the pupil.

Sequelae of trachoma

• Lids: Trichiasis, entropion, tylosis, ptosis, madarosis, ankyloblepharon.
• Conjunctiva: Concretions,. pseudocyst, xerosis, symblepharon.
• Cornea: Opacity, xerosis, total corneal pannus.

Adult inclusion conjunctivitis

• Caused by serotypes D to K of chlamydia trachomatis.
• Source of infection is urethritis in males and cervicitis in females.
• Mode of infection is through contaminated fingers or more commonly through contaminated water of swimming pool (hence the name swimming pool conjunctivitis).

Viral conjunctivitis

Acute haemorrhagic conjunctivitis

• Caused by picomaviruses (enterovirus type 70)
• Also known as ‘Apollo conjunctivitis’ or ‘epidemic haemorrhagic conjunctivitis’ (EHC).

Epidemic keratoconjunctivitis (EKC)

• Caused by adenovirus 8 and sometimes by 19.
• Acute follicular conjunctivitis associated with preauricular lymphadenopathy.
• Superficial punctate keratitis which appears after one week of onset is a distinctive feature of EKC.

Pharyngoconjunctival fever (Beal’s conjunctivitis)

• Caused by adenovirus 3 and 7.
• Primarily affects children and appears as epidemics
• Acute follicular conjunctivits associated with pharyngitis, fever and pre-auricular lymphadenopathy.

Ophthalmia neonatorum

• Bilateral inflammation of conjunctiva occuring during first 30 days of life.
• Any discharge or watering from the eyes in the First week of life should arouse its suspicion since tears are not formed till then.

Etiology

• Gonococcal infection is most common cause in developing countries.
• Neonatal inclusion conjunctivitis caused by serotypes D to K of chlamydia trachomatis is emerging as the most important cause.
• Staphylococcal/streptococcal infection.
• Chemical conjunctivitis induced by silver nitrate or antibiotics used as prophylaxis.
• Herpes simplex infection by type II virus is a rare cause.

Incubation period

 

 

 

Drug prophylaxis for ophthalmia neonatorum includes use of tetracycline eye ointment, erythromycin eye ointment or 1 percent silver nitrate eye drops (Crede’s method).

Allergic conjunctivitis

Spring catarrh (vernal Keratoconjunctivitis)

• A hypersensitivity reaction to exogenous allergens.
• It is thought to be an atopic allergic disorder in many cases, in which IgE mediated mechanisms play important role.
• More common in boys than girls between 4 and 20 years of age.
• Intense itching is a characteristic symptom.
• Cobble stone arrangement of papillae on the upper tarsal conjunctiva, Homer Tranta’s spots and ropy discharge are pathognomic.
• Palpebral form is more common than bulbar and mixed types.
• Vernal keratopathy occurs in following forms:
– Punctate epithelial keratitis involving upper cornea
– Ulcerative vernal keratitis (shield ulcer)
– Vernal corneal plaques
– Subepithelial scarring
– Pseudogerontoxon (Cupids bow)
• Keratoconus may be associated with spring catarrh

Atopic keratoconjunctivitis (AKC)

• It can be thought of as an adult equivalent of . vernal keratoconjunctivitis.
• Often associated with atopic dermatitis.
• Associations may be keratoconus and atopic cataract (posterior subcapsular).

Giant papillary conjunctivitis (GPC)

• A localised allergic response to a physically rough or deposited surface such as contact lens, prosthesis, leftout nylon sutures
• Papillae are 1 mm or more in diameter.

Phlyctenular keratoconjunctivitis

• Phlycten is a pinkish white nodule (1 to 3 mm in size), surrounded by hyperaemia on the bulbar conjunctiva, usually near the limbus.

• It is believed to be a delayed hypersenstivity (type IV-cell mediated) response to endogenous microbial proteins such as: tubercular, staphylococcal (most common), moraxella bacillus, and parasites (worm infestation)
• More common in girls than boys between 3 and 15 years of age.
• Comeal involvement may be in the form of scrofulous ulcer, fascicular ulcer and miliary ulcer.

Contact dermoconjunctivitis

A delayed hypersensitivity (type IV) response to prolonged contact with chemicals and drags such as: atropine, penicillin, neomycin, soframycin, and gentamicin.

Miscellaneous conjunctivitis

Acute follicular conjunctivitis is a feature of:

• Adult inclusion conjunctivitis,
• Epidemic keratoconjunctivitis (EKC)
• Pharyngo conjunctival fever (PCF)
• New-castle conjunctivitis
• Acute herpetic conjunctivitis

Pseudomembranous conjunctivitis is a feature of:

• Severe adenoviral infection
• Ligneous conjunctivitis
• Gonococcal conjunctivitis
• Autoimmune conjunctivis

Conjunctivitis associated with skin diseases such as acne rosacea, Stevens-Johnson syndrome, epidermolysis bullosa, and pemphigoid.

Ligneous conjunctivitis is a cicatrizing conjunctivitis in which membrane is cast off and recurs again and again.

Ophthalmia nodosa is a granulomatous inflammation of the conjunctiva in response to irritation caused by the retained hair of caterpillar.

Parinaud’s oculoglandular syndrome is a group of conditions characterised by unilateral granulomatous conjunctivitis, pre-auricular lymphadenopathy, and fever. Its common causes are cat scratch disease, tuberculosis, syphilis, lymphogranuloma venereum. . sarcoidosis and tularemia.

DEGENERATIVE CONDITIONS

Pterygium

• It is a combined elastotic degeneration with hyperplasia of the subconjunctival tissue in the form of vascularised granulation tissue.
• Exposure to ultraviolet rays of sunlight is implicated in the etiology.
• Fully developed pterygium has three parts: head, neck and body.
• Deposition of iron seen sometimes in corneal epithelium anterior to advancing head is called stocker’s line.
• Recurrence after surgical removal is 30-50 percent
• Measures to reduce recurrence include: transplantation in lower fornix (McReynold’s operation), postoperative beta irradiation, postoperative use of antimitotic drops (mitomycin- C or thiotepa), and mucous membrane grafts.
• Lamellar keratectomy and lamellar keratoplasty is indicated in recurrent recalcitrant cases.

Concretions

• These are formed due to accumulation of inspissated mucous and dead epithelial cell debris into the conjunctival depressions called loops of Henle.
• These are not calcareous deposits.
• Causes are trachoma, age-related degeneration and idiopathic.

CONJUNCTIVAL XEROSIS

Parenchymatous xerosis occurs following cicatricial disorganization of the conjunctiva due to local causes
such as:

• Trachoma
• Diphtheric membranous conjunctivitis
• Stevens-Johnson syndrome
• Pemphigus
• Pemphigoid
• Thermal, chemical or radiational burns of conjunctiva
• Prolonged exposure due to lagophthalmos.

Epithelial xerosis occurs due to hypovitaminosis- A. It typically occurs in children and is characterised
by varying degree of conjunctival thickening, wrinkling and pigmentation.

CYSTS AND TUMOURS

• Commonest cysts of the conjunctiva are lymphatic cysts and implantation cysts.
• Commonest congenital tumour of the conjunctiva is epibulbar dermoid.
• In Goldenhar’s syndrome epibulbar dermbid is associated with preauricular skin tag, hemifacial hypoplasia and vertebral anomalies
• Epithelioma (epidermoid carcinoma) of the conjunctiva usually occurs at limbus.
• Premalignant conditions of conjunctiva are intraepithelial epithelioma (Bowen’s disease), superficial spreading melanoma, Lentigomaligna (Hutchinson’s freckle).
• Naevus of Ota refers to oculodermal melanosis.

SOME SALIENT POINTS

• The eyes should not be bandaged in acute catarrhal or mucopurulent conjunctivitis.

• Topical steroids are contraindicated in acute bacterial conjunctivitis.

• Hyperaemia is the most conspicuous clinical sign of acute conjunctivitis.

• Unilateral chronic conjunctivitis should suggest the presence of a foreign body retained in the fornix, trichiasis or inflammation of the lacrimal sac.

• Trachoma and other conjunctival inflammation in the newborn cannot produce a follicular reaction; because the adenoid layer is devoid of lymphoid tissue until 2-3 months postnatally.

• Preauricular lymphadenopathy is a feature of viral and chlamydial conjunctivitis which is rarely present in bacterial conjunctivitis, but seldom in allergic conjunctivitis.

• Conjunctival ulceration should always suggest either the presence of an embedded foreign body or a tuberculous or syphilitic lesion.

• Epidemic keratoconjunctivitis is the only serious eye disease known to be transmissible by tonometry.