Endophthalmitis: decreasing rates

Endophthalmitis is one of the most feared complications that can affect the eye after eye surgery and can sometimes lead to dramatic outcomes such as enucleation.

Endophthalmitis clinically is an inflammation involving the internal structures of the eye and is caused by infectious agents such as bacteria, fungi and, on rare occasions, parasites that enter the eye during the intra- or postoperative phase. More rarely, it arises due to other causes, such as an intraocular lens entrapment after complicated cataract surgery or due to toxic agents.

Endophthalmitis can be schematically classified into endogenous and exogenous. In the form endogenous the infecting agent reaches the eye through the bloodstream. Predisposing conditions include impairment of the immune system (AIDS, tumours) and other debilitating conditions. This is a rare occurrence, but especially possible in people who use intravenous drugs. In 50% of cases endogenous endophthalmitis is caused by a fungal infection, usually candida or aspergillus.

Forms of endophthalmitis exogenous are due to the penetration of an infectious agent into the eye through any type of injury to the eyeball and are classified into post-surgical (acute and chronic) and post-traumatic. Post-surgical forms can occur after all types of eyeball surgery: cataract surgery and secondary IOL implants, glaucoma filtering surgery, vitreoretinal surgery and intravitreal injections. Post-traumatic forms arise after ocular perforating trauma with or without intraocular foreign body retention.

In the case of exogenous post-surgical endophthalmitis, the most frequent aetiology is bacterial. The contamination may occur during surgery or in the first few days of the postoperative course. The infecting microorganism is usually part of the normal bacterial flora present on the eyelids or conjunctiva, so the infection can occur due to poor perioperative and postoperative hygiene. Other possible causes of infection are contaminated surgical instruments or the surgical environment, insufficient or delayed healing due to suboptimal construction of the corneal 'tunnel', which favours the passage of bacteria into the eye during the early postoperative period. The preoperative presence of eyelid abnormalities, blepharitis, conjunctivitis, canaliculitis, nasolacrimal duct obstruction, dacryocystitis may also play an important role. Surgical complications such as incarceration of the vitreous in the corneal tunnel and capsular rupture increase the risk of endophthalmitis by 3-5 times up to 14-17 times.

The severity and clinical course of postoperative endophthalmitis are related to the virulence of the infecting bacteria, the timeliness of the diagnosis and the immunological status of the patient. The infectious process has an initial incubation phase, which may have no clinical signs, lasting at least 16-18 hours before sufficient bacterial load is reached to cause fibrinous exudation and neutrophil infiltration. Subsequently, inflammation increases in the posterior segment, extends to the anterior segment and an infiltration of macrophages and lymphocytes develops in the vitreous cavity resulting in the emergence of specific antibacterial antibodies. The chemical mediators of inflammation can in turn induce further recruitment of leucocytes that cause further destructive effects, such as retinal damage and vitreo-retinal proliferation (PVR).

A study published last September Endophthalmitis Rates and Types of Treatments After Intraocular Procedures | Ophthalmology | JAMA Ophthalmology | JAMA Network reported data from a very large sample of 5.8 million intraocular procedures with a long-term follow-up of 22 years across the US.

It has been found that the incidence rate of endophthalmitis has decreased dramatically over the past 20 years, falling from the initial 0.2% in the year 2000 to 0.05% in 2022. In addition, vitrectomy has been used less and less frequently as a primary treatment, compared to the situation since the publication of the Endophthalmitis Vitrectomy Study (EVS) in 1995.

Indeed, since the earliest days of intraocular surgery, endophthalmitis has always been a dreaded postoperative threat, capable of endangering vision, and enormous efforts have been made to try to reduce its incidence. These efforts have fortunately been successful over the last century. With the advent of modern sterilisation techniques, the rate of post-surgical endophthalmitis had already dropped to 1% in the mid-1900s and continued to decline steadily over the next 50 years.

On the subject of endophthalmitis see also:

• Injectable IOLs reduce the risk of endophthalmitis - Oculista Italiano
• "Travelling a lot to learn... - Oculista Italiano

• VanderBeek BL, Chen Y, Tomaiuolo M, et al. Endophthalmitis Rates and Types of Treatments After Intraocular Procedures. JAMA Ophthalmol.2024;142(9):827–834. doi:10.1001/jamaophthalmol.2024.2749
• Levison AL Mendes TS, Bhisitkul. Post-procedural endophthalmitis: a review. Expert Rev Ophthalmol. 8:45- 62,2013
• Barry P, Cordovés L, Gardner S. ESCR Guidelines for Prevention and Treatment of Endophthalmitis Following Cataract Surgery: Data, Dilemmas and Conclusions. Published by The European Society for Cataract and Refractive Surgeon, 2013.