**9. Endogenous endophthalmitis**

Endogenous endophthalmitis (EE), also called metastatic endophthalmitis, occurs as a result of the hematogenous spread of microorganisms from the body to the eye. The microorganism primarily spreads through the posterior segment vessels. The right

## *Infectious Endophthalmitis: Ongoing Challenges and New Prospectives DOI: http://dx.doi.org/10.5772/intechopen.106923*

eye is more commonly affected due to dominant and direct blood flow from the right carotid artery, however, approximately 25% of cases have a bilateral presentation [81].

The reported incidence of EE is 2 to 8% [82, 83]. However, it has been reported that the causative pathogens have geographical variations. They can be fungal or bacterial, with fungal pathogens being the commonest [82]. According to reported cases from Asia, fungal EE accounts for nearly 11.1 to 17.54% of total cases [84]. In bacterial EE, gram-positive streptococcus and staphylococcus are the most common pathogens. Gram-negative bacterial EE, however, is more common in Asian countries [85]. Among fungal species, *Candida albicans* account for many cases being the most common yeast, and among the molds, *Aspergillus flavus* is the commonest [86].

The risk factors for EE are primarily systemic conditions or medications which reduce immunity. Among these are diabetes mellitus, malignancies, asplenia, cardiac or renal transplant, and severe infections (e.g., pneumonia, urinary tract infection, vertebral osteomyelitis, liver abscess, and acquired immune deficiency syndrome), chronic alcoholism, intravenous catheters, and drug abuse and long-term use of steroids or other immunosuppressants [87–90].

The patients with the aforementioned risk factors and associated with ophthalmic symptoms require a thorough ophthalmic assessment to rule out EE. Such symptoms vary from eye pain, redness, photophobia, blurred vision, floaters, and flashes. The clinical signs are similar to other types of endophthalmitis, however, in EE the vitreous involvement, for example, vitreous haze, vitreous cells and floaters as well as subretinal membranes and exudates are the most important associated findings to look for [91, 92]. Aspergillus flavus is known to cause yellow/white exudates in the vitreous, which vary from focal to diffuse. The hallmark feature of Candida EE is the presence of fluffy cotton wool-like white retinal exudates or colonies along with vitritis (**Figure 5**) [92].

The management of EE should be focused on systemic evaluation and management of underlying causes. In addition to clinical evaluation, a B scan ultrasound may delineate choroidal abscess, which appears as a dome-shaped elevation on B scan similar to choroidal detachment [93].

Blood cultures and urine cultures are important adjuvant diagnostic modality in the diagnosis of possible systemic infection. It was reported that blood culture has shown a higher culture positivity than the vitreous sample, probably due to the

**Figure 5.** *Bilateral endogenous Nocardia endophthalmitis. Note the subretinal infiltrates and vitirtis. (Courtesy of Dr. Hemant Trehan).*

sample volume obtained. Moreover, culture at extraocular sites has yielded a 21–100% positivity rate as per previous reports [94].

Medical management includes topical and systemic antibiotics or antifungals, intravitreal antibiotics or antifungals, and pars plana vitrectomy (PPV). PPV is recommended for non-resolving vision-threatening EE cases. PPV serves both diagnostic and therapeutic purposes. Sato et al. suggested early vitrectomy in Candida EE cases [95]. Yoon et al. suggested early PPV in Klebsiella endophthalmitis, which may result in better visual effects [96]. The collaboration of the treating ophthalmologist or vitreoretinal surgeon, microbiologists, pathologists, and the critical care physician plays a vital role in determining the patient's final systemic and ocular outcome [82].

Prognosis of EE similar to other endophthalmitis depends on the duration of the condition, the extent of the ocular structures involved, the virulence of the causative agents, and the timing of initiation of treatment as well as the response to the treatment. Reported studies have shown that yeasts have a better prognosis, followed by bacteria followed by molds, which have the worst prognosis.
