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What is Endophthalmitis and explain in detail?
Endophthalmitis is inflammation of the interior cavity of the eye, usually caused by infection. It is a possible complication of all intraocular surgeries, particularly cataract surgery, and can result in loss of vision or loss of the eye itself. Infection can be caused by bacteria or fungi, and is classified as exogenous (infection introduced by direct inoculation as in surgery or penetrating trauma), or endogenous (organisms carried by blood vessels to the eye from another site of infection). Other non-infectious causes include toxins, allergic reactions, and retained intraocular foreign bodies. Intravitreal injections are a rare cause, with an incidence rate usually less than .05%.

Signs and symptoms
There is usually a history of recent eye surgery or penetrating trauma to the eye. Symptoms include severe pain, vision loss, and intense redness of the conjunctiva. Hypopyon can be present and should be looked for on examination by a slit lamp. It can first present with the black dot sign (Martin-Farina sign), where patients may report a small area of loss of vision that resembles a black dot or fly.
An eye exam should be considered in systemic candidiasis, as up to 3% of cases of candidal blood infections lead to endophthalmitis.

Complications
Panophthalmitis — Progression to involve all the coats of the eye.
Corneal ulcer
Orbital cellulitis
Impairment of vision
Complete loss of vision
Loss of eye architecture
Enucleation

Cause
Bacteria: N. meningitidis, Staphylococcus aureus, S. epidermidis, S. pneumoniae, other streptococcal spp., Cutibacterium acnes, Pseudomonas aeruginosa, other gram negative organisms. 
Viruses: Herpes simplex virus.
Fungi: Candida spp. Fusarium
Parasites: Toxoplasma gondii, Toxocara.A recent systematic review found that the most common source of infectious transmission following cataract surgery was attributed to a contaminated intaocular solution (i.e. irrigation solution, viscoelastic, or diluted antibiotic), although there is a large diversity of exogenous microorganisms that can travel via various routes including the operating room environment, phacoemulsifcation machine, surgical instruments, topical anesthetics, intraocular lens, autoclave solution, and cotton wool swabs.Late-onset endophthalmitis is mostly caused by Cutibacterium acnes.Causative organisms are not present in all cases