What is Endophthalmitis ?
Endophthalmitis is defined as an inflammation of the inner structures of the eyeball uveal tissue and retina associated with vitreous cavity, anterior chamber and posterior chamber.
Etiology of Endophthalmitis ?
The causes of endophthalmitis may be infectious or non-infectious.
A. Infective endophthalmitis
1. Exogenous infections.
Purulent inflammations are generally caused by exogenous infections following perforating injuries, perforation of infected corneal ulcers or as postoperative infections following intraocular operations.
2. Endogenous endophthalmitis.
It may occur rarely through blood stream from some infected focus in the body such as caries teeth, generalised septicaemia and puerperal sepsis.
3. Secondary infections from surrounding structures.
It is very rare. However, cases of purulent intraocular inflammation have been reported following extension of infection from orbital cellulitis, thrombophlebitis and infected corneal ulcers.
Causative organisms
1. Bacterial endophthalmitis.
The most frequent pathogens causing acute bacterial endophthalmitis are gram positive cocci i.e., staphylococcus epidermidis and staphylococcus aureus. Other causative bacteria include streptococci, pseudomonas, pneumococci and corynebacterium. Propionio bacterium acnes and actinomyces are gram-positive organisms capable of producing slow grade endophthalmitis.
2. Fungal endophthalmitis
is comparatively rare. It is caused by aspergillus, fusarium, candida etc.
B. Non-infective (sterile) endophthalmitis
Sterile endophthalmitis refers to inflammation of inner structures of eyeball caused by certain toxins/toxic substances.
It occurs in following situations.
1. Postoperative sterile endophthalmitis may occur as toxic reaction to:
Chemicals adherent to intraocular lens (IOL) or Chemicals adherent to instruments.
2. Post-traumatic sterile endophthalmitis may occur as toxic reaction to retained intraocular foreign body, e.g., pure copper.
3. Intraocular tumour necrosis may present as sterile endophthalmitis (masquerade syndrome).
4. Phacoanaphylactic endophthalmitis may be induced by lens proteins in patients with Morgagnian cataract.
Clinical picture of acute bacterial endophthalmitis
Acute postoperative endophthalmitis is a catastrophic complication of intraocular surgery with an incidence of about 0.1%. Source of infection in most of the cases is thought to be patient’s own periocular bacterial flora of the eyelids, conjunctiva, and lacrimal sac. Other potential sources of infection include contaminated solutions and instruments, and environmental flora including that of surgeon and operating room personnel.
Symptoms of Endophthalmitis
Acute bacterial endophthalmitis usually occurs within 7 days of operation and is characterized by severe ocular pain, redness, lacrimation, photophobia and marked loss of vision.
Signs of Endophthalmitis :
1. Lids become red and swollen.
2. Conjunctiva shows chemosis and marked circumcorneal congestion.
Note: Conjunctival congestion, corneal oedema, hypopyon and yellowish white exudates in the vitreous seen in the pupillary area behind the IOL.
3. Cornea is oedematous, cloudy and ring infiltration may be formed.
4. Edges of wound become yellow and necrotic and wound may gape in exogenous form.
5. Anterior chamber shows hypopyon; soon it becomes full of pus.
6. Iris, when visible, is oedematous and muddy.
7. Pupil shows yellow reflex due to purulent exudation in vitreous. When anterior chamber becomes full of pus, iris and pupil details are not seen.
8. Vitreous exudation. In metastatic forms and in cases with deep infections, vitreous cavity is filled with exudation and pus. Soon a yellowish white mass is seen through fixed dilated pupil. This sign is called amaurotic cat’s-eye reflex.
9. Intraocular pressure is raised in early stages, but in severe cases, the ciliary processes are destroyed, and a fall in intraocular pressure may ultimately result in shrinkage of the globe.
Treatment of Endophthalmitis
An early diagnosis and vigorous therapy is the hallmark of the treatment of endophthalmitis. Following therapeutic regime is recommended for suspected bacterial endophthalmitis.
A. Antibiotic therapy
1. Intravitreal antibiotics and diagnostic tap should be made as early as possible. It is performed transconjunctivally under topical anaesthesia from the area of pars plana (4-5 mm from the limbus). The vitreous tap is made using 23-gauge needle followed by the intravitreal injection using a disposable tuberculin syringe and 30-gauge needle.
The main stay of treatment of acute bacterial endophthalmitis is intravitreal injection of antibiotics at the earliest possible. Usually a combination of two antibiotics – one effective against gram positive coagulase negative staphylococci and the other against gram-negative bacilli is used as below :
• First choice: Vancomycin 1 mg in 0.1 ml plus ceftazidime 2.25 mg in 0.1 ml.
• Second choice: Vancomycin 1 mg in 0.1 ml plus Amikacin 0.4 mg in 0.1 ml.
• Third choice: Vancomycin 1 mg in 0.1 ml plusgentamycin 0.2 mg in 0.1 ml.
Note: Some surgeons prefer to add dexamethasone 0.4 mg in 0.1 ml to limit post-inflammatory consequences.
• Gentamycin is 4 times more retinotoxic (causes macular infarction) than amikacin. Preferably the aminoglycosides should be avoided.
• The aspirated fluid sample should be used for bacterial culture and smear examination. If vitreous aspirate is collected in an emergency when immediate facilities for culture are not available, it should be stored promptly in refrigerator at 4°C.
• If there is no improvement, a repeat intravitreal injection should be given after 48 hours taking into consideration the reports of bacteriological examination.
2. Subconjunctival injections of antibiotics should be given daily for 5-7 days to maintain therapeutic intraocular concentration :
• First choice : Vancomycin 25 mg in 0.5 ml plus. Ceftazidime 100 mg in 0.5 ml
• Second choice : Vancomycin 25 mg in 0.5 ml plus Cefuroxime 125 mg in 0.5 ml
3. Topical concentrated antibiotics should be started immediately and used frequently (every 30 minute to 1 hourly). To begin with a combination of two drugs should be preferred, one having a predominant effect on the gram-positive organisms and the other against gram-negative organisms as below:
• Vancomycin (50 mg/ml) or cefazoline (50mg/ml) plus.
• Amikacin (20 mg/ml) or tobramycin (15 mg%).
B. Steroid therapy
Steroids limit the tissue damage caused by inflammatory process. Most surgeons recommend their use after 24 to 48 hours of control of infection by intensive antibiotic therapy. However, some surgeons recommend their immediate use (controversial). Routes of administration and doses are:
• Intravitreal injection of dexamethasone 0.4 mg in
0.1ml.
• Subconjunctival injection of dexamethasone 4 mg (1ml) OD for 5-7 days.
• Topical dexamethasone (0.1%) or predacetate (1%) used frequently.
Systemic steroids.
Oral corticosteroids should preferably be started after 24 hours of intensive antibiotic therapy. A daily therapy regime with 60 mg prednisolone to be followed by 50, 40, 30, 20 and 10 mg for 2 days each may be adopted.
C. Supportive therapy
1. Cycloplegics. Preferably 1% atropine or alternatively 2% homatropine eyedrops should be instilled TDS or QID.
2. Antiglaucoma drugs.In patients with raised intraocular pressure drugs such a oral acetazolamide (250 mg TDS) and timolol (0.5% BD) may be prescribed.
D. Vitrectomy operation
Vitreoctomy should be performed if the patient does not improve with the above intensive therapy for 48 to 72 hours or when the patient presents with severe infection with visual acuity reduced to light perception. Vitrectomy helps in removal of infecting organisms, toxins and enzymes present in the infected vitreous mass.