It is usually exogenous in origin, occurring after ocular trauma or surgery [2, 3].
An endotamponade that remains in the vitreous cavity for several months may absorb endogenous substances from the ocular tissues or exogenous substances via the blood stream.
However, they could also have originated from unusual exogenous sources, e.g., contaminated surgical materials, ocular rinsing solutions, or a contaminated environment.
Most cases are exogenous and occur after eye surgery, after penetrating ocular trauma, or as an extension of corneal infection.
For the patient in our report, in the setting of reported trauma and negative metastatic work-up results, it is unclear whether ocular disease resulted independently as an exogenous infection or from endogenous lymphatic and/or hematogenous spread from the patient's lung.
Exogenous fungal endophthalmitis is associated with poorer visual acuity outcomes and higher rates of enucleation given associated ocular trauma and direct inoculation of the eye; however, these cases are also most commonly caused by molds, fusarium, or fungal species other than Candida[2, 3].
A recent work [28] demonstrated that monocular deprivation (MD) increases the expression of IGF-1 binding protein and affects several genes in the IGF-1 pathway; exogenous application of IGF-1 preventhethe physiological effect of MD on ocular dominance plasticity examined in vivo.
The vast literature on exogenous antioxidant supplementation and the mixed findings from epidemiological studies on ocular health are not surprising given that (1) these compounds are unable to reach their target tissue via the circulatory system and (2) transporter proteins must be expressed in the cornea and lens to specifically accumulate these exogenous molecules into ocular cells.
However, not all Chlamydiae are dependent on exogenous tryptophan: serovars D K of Chlamydia trachomatis, with urogenital rather than ocular tropism, possess trpRBA, a tryptophan synthase gene cluster, and can synthesize tryptophan from indole substrates produced by vaginal microbial flora [ 62].
For experiments involving intravitreal delivery of exogenous agents, animals that developed complications from the injection procedure (e.g., ocular infection, inflammation) were excluded from the analysis.
