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What is Sympathetic ophthalmia and explain in detail?
Sympathetic ophthalmia (SO), also called spared eye injury, is a diffuse granulomatous inflammation of the uveal layer of both eyes following trauma to one eye. It can leave the affected person completely blind. Symptoms may develop from days to several years after a penetrating eye injury. It typically results from a delayed hypersensitivity reaction.

Signs and symptoms
Eye floaters and loss of accommodation are among the earliest symptoms. The disease may progress to severe inflammation of the uveal layer of the eye (uveitis) with pain and sensitivity of the eyes to light. The affected eye often remains relatively painless while the inflammatory disease spreads through the uvea, where characteristic focal infiltrates in the choroid named Dalén–Fuchs nodules can be seen. The retina, however, usually remains uninvolved, although perivascular cuffing of the retinal vessels with inflammatory cells may occur. Swelling of the optic disc (papilledema), secondary glaucoma, vitiligo, and poliosis of the eyelashes may accompany SO.

Pathophysiology
Sympathetic ophthalmia is currently thought to be an autoimmune inflammatory response toward ocular antigens, specifically a delayed hypersensitivity to melanin-containing structures from the outer segments of the photoreceptor layer of the retina. The immune system, which normally is not exposed to ocular proteins, is introduced to the contents of the eye following traumatic injury. Once exposed, it senses these antigens as foreign, and begins attacking them. The onset of this process can be from days to years after the inciting traumatic event.

Diagnosis
Diagnosis is clinical, seeking a history of eye injury. An important differential diagnosis is Vogt–Koyanagi–Harada syndrome (VKH), which is thought to have the same pathogenesis, without a history of surgery or penetrating eye injury.
Still experimental, skin tests with soluble extracts of human or bovine uveal tissue are said to elicit delayed hypersensitivity responses in these patients. Additionally, circulating antibodies to uveal antigens have been found in patients with SO and VKH, as well as those with long-standing uveitis, making this a less than specific assay for SO and VKH.

Treatment
Because SO is so rarely encountered following eye injury, even when the injured eye is retained, the first choice of treatment may not be enucleation or evisceration, especially if there is a chance that the injured eye may regain some function. Additionally, with current advanced surgical techniques, many eyes once considered nonviable now have a fair prognosis.
However, only if the injured eye has completely lost its vision and has no potential for any visual recovery, prevention of SO is done by enucleation of the injured eye preferably within the first 2 weeks of injury