The most feared complication of any intraocular surgery is the development of endophthalmitis. The reported incidence of post surgical endophthalmitis in various series is 0.04%-4%. The incidence of post operative endophthalmitis in India varies from 1 in 200 to 1 in 1000. The literature talks about isolated cases of postoperative endophthalmitis as well as cluster endophthalmitis.
The risk factors are different for isolated and cluster endophthalmitis. Patient factors play a predominant role in isolated postoperative endophthalmitis. Patients own bacterial flora may gain entry at the time of surgery and thus increasing the development of postoperative endophthalmitis. We should also rule out diseases like chronic blepharitis, conjunctivitis, canaliculitis and keratoconjuntivitis sicca before planning ocular surgery for the patient. The other important intraoperative risk factors for isolated postoperative endophthalmitis are inadequate eyelid or conjunctival disinfection, prolonged surgery, vitreous loss, prolene haptics of Iol. The above factors can be taken care of by the use of pre-operative topical antibiotics for 24 hours, facial scrub, povidone iodine into the conjunctival sac, adhesive plastic drapes to separate eyelashes, surgeon gloves, subconjunctival antibiotics at the end of the surgery. The role of antibiotics in the irrigating solutions is still questionable.
External factors are the major risk factors in the causation of cluster postoperative endophthalmitis. There have been various reports from all over the world describing bacterial as well as fungal postoperative cluster endophthalmitis. Defects in sterlisation of instruments, contamination of tap water, multiple dose fluids and drugs have been held responsible for bacterial cluster postoperative endophthalmitis. Fungal cluster postoperative endophthalmitis has been reported after contaminated irrigating solutions, IOLs, viscoelastics, improper ventilation system, poor OT hygiene and even after hospital construction activity. To prevent the occurrence of these cluster infections, we have to remain on guard for any breach in infection control measures, use standardized irrigating solutions and drugs.
The prognosis in postoperative endophthalmitis depends on the virulence of the microorganisms and early intervention. For early recognition of postoperative infection, frequent postoperative follow up at 24 hours, 72 hour and 7 days is necessary. Every follow up examination comprises of recording visual acuity, slit lamp biomicroscopic examination and looking for media clarity. After the clinical diagnosis of endophthalmitis is made, the further management depends on the presenting visual acuity and the microbiological spectrum.
EVS, the largest multicentric trial on post operative endophthalmitis did not include the cases of fungal endophthalmitis. The microbiological spectrum as per the EVS was different from the microbiological spectrum found in our setup where we have higher incidence of fungal and gram negative endophthalmitis. The reported Indian figures show gram negative bacteria to account for 20% of the culture positive cases as against the incidence of 6% reported by EVS. Fungal endophthalmitis comprised of 16.7% of the culture positive cases.
As per the EVS guidelines, the eyes with visual acuity of hand motions or better are subjected to vitreous tap and intravitreal broad spectrum antibiotics. Vitreous sample is immediately subjected to gram stain, KOH and calcoflour smear. The sample is also innoculated on blood agar, chocolate agar, liquid agar and Sabauraud’s dextrose agar. We prefer to use Vancomycin 1 mg/0.1ml and Ceftazidime 2.25mg/0.1ml because 94% of the culture positive cases are caused by gram positive organisms which are 100% sensitive to Vancomycin and 6% of culture positive cases are by gram negative group of organisms which are 90% sensitive to Ceftazidime. Systemic antibiotics are not recommended in cases of acute bacterial postoperative endophthalmitis. The indications for pars plana vitrectomy are visual acuity of light perception at presentation, deterioration or no improvement despite intravitreal antibiotics, delayed onset endophthalmitis or fungal endophthalmitis. The protocol for managing fungal endophthalmitis is pars plana vitrectomy, intravitreal amphotericin B 5ug and systemic antifungals. The precautions while performing pars plana vitrectomy in endophthalmitis are the use of 6mm infusion cannula, clearing AC hypopyon and exudative membrane, collection of undiluted vitreous sample from midvitreous cavity, aiming to clear only core vitreous and IOL explantation only in cases of gross infection.
In our setup, post operative infections commonly occur in clusters. We see more of gram negative organisms and fungi. And different microbiological spectrum mandates pars plana vitrectomy in majority of your patients. The microbiology is suggestive of contaminated solutions as an important cause of post operative endophthalmitis in our setup. We should remain vigilant and follow standardized surgical protocols. Prompt and aggressive therapeutic interventions are required. In the least, intravitreal antibiotics should be given and the patient should be referred to vitreo-retinal services for subsequent management.
Prof. Amod Gupta
Professor and Head, Dept. of Ophthalmology,