OCULAR INFECTIONS

DR A. R. OJEWUYI

Introduction

Introduction

• External ocular structures and surfaces are often involved in infections from a variety of pathogens.

• Infections/Damage to the eye structures usually results from:

The structure and immune status of the host Integrity of the underlying tissue The character of the invading organism Immune response of the host

Introduction

Host immune protective mechanism:

Protection of ocular structures is supported by a defence system that includes

local and systemic

specific and non-specific

humoral and cellular mechanisms

Introduction

These defence mechanisms includes:1. Anatomical arrangement of the eye that keeps the

inner ocular structures protected.2. The intact epithelia of the lid, conjunctiva and cornea

which provide a protective barrier.3. Tear and tear film contain a high concentration of IgA,

lysozyme, and lactoferrin.4. The blinking action and flow of tears remove debris

and bacteria from the ocular surface.5. Cooler ocular surface temperature also inhibit survival

of many microorganisms.

Risk Factors Associated with Ocular Infections

• Age: Acute bacterial and viral conjunctivitis occurs more in childhood, chronic conjunctivitis and VZV conjunctivitis occurs more in the elderly

• Sex

• Race

• Socioeconomic status

• Behaviour

• Geographic location

• Occupation

• Underlying disease

Infections of the Eye Structures

• Conjunctivitis: Infections of the conjunctivae; it is the most common ocular complaint.

• Blepharitis: Infections of the eye lids.• Keratitis: Infections of the cornea• Scleritis and Episcleritis: Infection of the sclera and

episclera.• Preseptal and Orbital Cellulitis: Infections of the orbit• Endophthalmitis: Infections of the Intraocular chambers• Uveitis: Infections of the iris, ciliary body and choroids• Retinitis: Infections of the retina• Infections of the lacrimal apparatus; Dacryoadenitis,

Canaliculitis, Dacryocystitis

Some Microorganisms Associated with Ocular Infectious Disease

• Bacteria

Chlamydia trachomatis

Treponema pallidum

Listeria monocytogens

Staphylococccus spp.

Streptococcus spp.

Heamophilus spp.

Neisseria spp.

Moraxella spp.

Rickettsia spp.

Mycobacterium spp.

Pseudomonas aeruginosa

• Fungi

Candida spp.

Cryptococcus neoformas

Aspergillus spp.

• Viruses Adenovirus

Coxsackievirus

Cytomegalovirus

Enterovirus

EBV

HSV

HIV

Measles virus

• Parasites

Acantamoeba spp.

Ascaris lumbricoidesOnchocerca volvulus

Loa loa

Toxoplasma gondii

Plasmodium spp.

Chlamydial Ocular Infections

• Chlamydial trachomatis causes a myriad of ocular infections including trachoma, neonatal conjuctivitis, inclusion conjuctivitis and lymphogranuloma venereum(LGV is an STI which can involve the eyes in cases of accidental innoculation)

• There about 15 serotypes;A, B, Ba, C, D, E, F, G, H, I, J, K, L1, L2, L3

• Serotypes A, B, Ba, C cause trachoma• Serotypes D-K cause urethritis, PID, ectopic pregnancy,

neonatal conjunctivitis, neonatal pneumonia• Serotypes L1-L3 cause LGV

Trachoma

• An ancient disease which is a leading cause of world blindness.

• There is regional variation in prevalence and severity.

• More common among the poor and people with poor personal hygiene.

• Follicular conjunctivitis followed by repeat infections, scarring and ultimately blindness.

Laboratory Diagnosis

• Direct detection of chlamydial inclusion or elementary bodies in specimen by immunofluorescence staining

• Culture : McCoy or Hep-2 cell lines

• Non-culture methods: PCR, Ligase chain reaction (LCR), Enzyme immunoassay (EIA)

Treatment

• Tropical treatment alone is inadequate

• Adults: Doxycycline,100mg twice a day for 7 days OR azithromycin, 1g by mouth as a single dose

• Neonates: Erythromycin syrup, 50mg/kg/day by mouth in four doses for 14days

Viral Conjunctivitis

• This is the most commonly recognised ocular infectious disease

• May present as acute or chronic, mild/self limiting to severe/destructive disease

• Acute viral infections are caused mainly by adenoviruses, herpesviruses and enteroviruses

• Adenovirus type 8 and 19 cause Epidemic keratoconjuntivitis (EKC)

• Pharyngoconjuctival fever (PCF) is caused mailyby adenovirus type 3, occasionally by serovars 1, 2, 4, 5, 6, 8, and 14

Viral Conjunctivitis

• Acute hemorrhagic conjunctivitis or epidemic hemorrhagic conjunctivitis (Apollo XI) is caused by enterovirus 70, coxsackievirus A24, and rarely adenovirus type 11

• HSV also causes blepharoconjunctivitis and is responsible for majority of severe ocular infections especially in children

• HSV infection should be differentiated from adenovirus infections and treated.

Parasitic Infections of the Eye

• Onchocerciasis• Loasis• Acanthamoeba spp. • Toxoplasmosis• Taenia solium• Toxocara canis and cati• Trypanosomiasis• Wuchereria bancrofti• Ascaris lumbricoides• Leishmania spp.• Plasmodium spp.

Onchocerca volvulus

• Onchocerca volvulus – Tissue nematodes, a filariaworms.

• Transmitted by Simulium blackflies

• The commonest vectors belong to the Simuliumdamnosum complex, which live their larval stages in clear, fast-running streams

• The adult flies survive only where there is high humidity and plenty of streamside vegetation

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MICROFILARIA

The larvae develop into male and female worms in subcutaneous tissue.

Viviparous females produce unsheathed microfilariae (lymph spaces/connective tissue).

Microfilariae can also be in fluids from nodules.

Microfilariae also migrate to the eye and other organs of the body.

ONCHOCERCA VOLVULUS

Onchocerciasis

• Adult (macrofilaria) clusters cause subcutaneous nodules, microfilariaecause blindness.

• In addition to visual impairment or blindness and nodules under the skin or debilitating itching.

• Worldwide, onchocerciasis is second only to trachoma as an infectious cause of blindness (WHO).

Ocular onchocerciasis

• Microfilariae are found in the cornea and in the anterior chamber.

• Cause iridocyclitis. choroiditis.

• There is redness and irritation.

• Progressive changes caused by inflammatory reaction around damaged and dead microfilariaecause sclerosing keratitiswhich lead to blindness.

• Cataract and glaucoma can also result

Destroyed Eye tissues

Diagnosis

• Observation of adult worm in prominent subcutaneous nodules and skin biopsy/snips.

• Histologic examination for microfilariae.

Onchocerciasis Therapy

Treatment involves: Surgery and Drugs

Surgical approach: removal of adults (macrofilariae),

• Nodulectomy

Chemotherapy: mainly for microfilariae;

• Diethylcarbamazine (DEC),

• Ivermectin (Mectizan)and

• Others e.g. Doxycycline, Suramin, etc

Ophthalmia neonatorum

• Neonatal conjunctivitis occurring in the first 28 days of life.

• Mostly infective in origin, can also be caused by chemicals.

• Bacterial causes are; Chlamydia trachomatis, Neisseria gonorrhoeae, Staphylococcus aureus, Streptococcus pneumoniae and others

• Viral causes include HSV

Ophthalmia neonatorum

• Affected babies present with purulent , mucopurulent or mucoiddischarge from one or both eyes.

• Treatment should be guided by the organism isolated.

• Hourly saline lavage

• Prevention by maternal screening, use of silver nitrate, erythromycin e.t.c

Contact Lenses and Solutions

• Contact lenses are major risk factors for microbial keratitis.

• Commonest pathogens involved are P. aeruginosa, S. marcescens, S. aureus andAcanthamoeba spp.

Laboratory Diagnosis of Ocular Infections

• Materials or scrapings for cultures should be collected as soon as possible after onset of infections.

• Samples must be collected from actual site of infections e.g conjunctival and lid cultures are inadequate to assess corneal involvement.

• All ocular fluids, tissues, sponges, and other surgical material must be submitted in sterile, leak proof containers that are properly labelled.

Laboratory Diagnosis of Ocular Infections

• Direct microscopic examination including Gram, Giemsa, calcofluor white, AFB and immunoflorescent stains, and impression cytology.

• Most of the bacterial and fungal ocular isolates may be recovered on chocolate and blood agar when incubated under the proper conditions of temperature and atmosphere.

• Molecular techniques: DNA probes, PCR

Ocular Therapy

• For ophthalmic drugs to be effective, they must reach ocular tissues in relatively high concentrations.

• Routes of administration include topical, periocular, intracameral and intravitreal

Case Review

• History- a healthy 20 year old woman with no history of ocular disease had been wearing disposable contact lenses for 3 months. She replaced them every 7 to 10 days. The patient developed blurred vision, pain, photophobia and redness in her right eye during the twelfth week.

• Examination- revealed oedema and four small ulcers with a green, mucopurulent discharge.

Case Review

• Investigations

– Gram and Giemsa stains were prepared from the mucopurulent discharge.

– Cultures were performed from the corneal scrapings and from the contact lens and solution

– Gram showed Gram negative bacilli and culture yielded an oxidase positive green pigment-producing organism.

What is the likely diagnosis?

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