Contact illumination

From Biology-Online Dictionary | Biology-Online Dictionary

Contact illumination

illumination of the eye by means of an instrument in contact with the cornea or bulbar conjunctiva.

critical illumination, the precise focusing of the light Source directly upon the object being examined.

Dark-field illumination, a procedure in which a black circular shield is used to block the majority of the vertically directed rays of light (e.g., the field is dark), and a circumferential, suitably angled, mirrored surface is used to direct the peripheral rays horizontally against the object, thereby reflecting the light vertically through the objective lens and along the optical axis; thus, the object is well illuminated in a contrasting dark background.

Synonym: dark-ground illumination.