Etiology

• Endophthalmitis/panophthalmitis falls into roughly three etiologic categories:
• Inflammation associated with an underlying systemic illness, ie. the systemic mycoses, neoplasia, bacterial septicemia (rare), and feline infectious peritonitis (rare; primarily endophthalmitis). Any infectious cause of chorioretinitis can potentially result in endophthalmitis, but the diseases listed are the most common causes.
• Inflammation associated with a bacterial infection that is introduced into the eye, eg following surgery to remove the lens, following penetrating ulcers, or associated with contamination of penetrating wounds (especially cat scratches).
• Inflammation associated with migration of penetrating foreign bodies. This last category may or may not be complicated by bacterial infection.

Predisposing factors

General

• Exposure to pathogenic or drug resistant bacteria.
• Pre-existing inflammation within the eye or penetration of the eye.

Pathophysiology

• Endophthalmitis may begin as penetrating keratitis Keratitis, anterior uveitis Anterior uvea: traumatic uveitis or chorioretinitis Eye: chorioretinitis. Progressive infection and necrosis, or migration/inflammation induced by a foreign body results in extension of the inflammation into the surrounding or adjacent structures.
• Panophthalmitis results when the sclera also becomes involved. Panophthalmitis may then extend into the periocular tissues and affect the episclera, conjunctiva, extraocular muscles, periorbital fat, third eyelid and external eyelids.
• Endophthalmitis does not usually result in a change in the shape of the eye, although the development of severe secondary glaucoma may cause buphthalmos.
• Panophthalmitis may cause dramatic thickening of the sclera and periocular tissues, along with secondary glaucoma, and may cause a change in the shape of the eye.
• Vision is threatened with both conditions, and blindness is almost always present in eyes with panophthalmitis.
• Extension of inflammation into the optic nerve may also occur.

Timecourse

• Most cases of endophthalmitis/panophthalmitis develop rapidly. Clinical signs may develop within 24-72 hours.
• The clinical course is often protracted, with therapy required for several weeks to months.