Medical Study point

Chalcosis oculi (Greek chalkos: copper): Chronic ophthalmic exposure to particulate elemental copper or one of its alloys may result in its deposition in the cornea, lens, vitreous and retina. Copper deposits in the cornea (chalcosis corneae) appear as golden brown, ruby red or green pigment ring in the peripheral Descemet's membrane (Kayser Fleischer ring). Lens opacities (chalcosis lentis) occur in the form of anterior subcapsular cataract ('sunflower' cataract and typically greenish in color).

Ochronosis:-  ochronosis is the bluish black discoloration of tissues, such as the ear cartilage and the ocular tissue (sclera, between the margin of the cornea and the outer or inner canthus), seen with alkaptonuria (autosomal recessive metabolic disorder caused by deficiency of homogentisic acid oxidase). It can also occur from exposure to various substances, such as phenol, trinitrophenol, resorcinol, mercury, picric acid, benzene, hydroquinone and antimalarials.

                            NECROSIS Definition :- Necrosis is defined as a localised area of death of tissue followed later by degradation of tissue by hydrolytic enzymes liberated from dead cells; it is invariably accompanied by inflammatory reaction. Based on etiology and morphologic appearance, there are 5 types of necrosis: coagulative, liquefaction (colliquative), caseous, fat, and fibrinoid necrosis. 1. COAGULATIVE NECROSIS:- This is the most common type of necrosis caused by irreversible focal injury, mostly from sudden cessation of blood flow. 2. LIQUEFACTION (COLLIQUATIVE) NECROSIS:- Lique- faction or colliquative necrosis also occurs commonly due to ischaemicinjury and bacterial or fungal infections but hydrolytic enzymes in tissue degradation have a dominant role in causing semi-fluid material. The common examples are infarct brain and abscess cavity. 3. CASEOUS NECROSIS:- Caseous (caseous= cheese-like) necrosis is found in the centre of foci of tuberculous infections. It