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an encircling region or area; by extension, any area with specific characteristics or boundary.
ciliary zone the outer of the two regions into which the anterior surface of the iris is divided by the collarette.
comfort zone an environmental temperature between 13 and 21°C (55 and 70°F) with a humidity of 30 to 55 per cent.
epileptogenic zone an area, stimulation of which may provoke an epileptic seizure.
erogenous zone (erotogenic zone) in psychoanalytic theory, an area of the body through which the libido expresses itself and which is therefore susceptible to erotic excitation upon stimulation; the primary sites are the oral, anal, and genital regions, but the other body orifices, breasts, and skin are also included.
zone of partial preservation in spinal cord injury, an area of only partial damage that may include up to three consecutive spinal segments caudal to the level of the injury.
pupillary zone the inner of the two regions into which the anterior surface of the iris is divided by the collarette.
transition zone (transitional zone) any anatomical region that marks the point at which the constituents of a structure change from one type to another; for example, the circle in the equator of the ocular lens in which epithelial fibers are developed into lens fibers, or the zone (anocutaneous line) that marks the junction of stratified squamous epithelium with columnar epithelium.
the central region of the anterior surface of the iris located between the collarette and the pupillary margin.
Synonym(s): zona pupillaris
The innermost of two annular areas visible on the anterior surface of the iris.See: ciliary zone
See also: zone
pertaining to or emanating from the pupil.
an obstruction to the flow of aqueous between the border of the pupil and the anterior capsule of the lens.
pupillary consensual light reflex
constriction of the pupil in the eye opposite to the one receiving an intensified beam of light, and reversal when the light is removed. The reflex is clearcut in humans and dogs but little used in food animals. Presence of the reflex is a guarantee of integrity of the optic pathways.
see iris cyst.
pupillary light reflex
constriction of a dilated pupil in response to an increase in light intensity and a dilatation of a constricted pupil in response to a decrease in the intensity. Activity of the reflex indicates the efficiency of the retina, the optic and oculomotor nerves and the musculature of the iris.
a surgical technique for resection of an iridocapsular membrane, formed as a sequela to cataract surgery.
persistent pupillary membrane
nonvascular remnants of the tunica vasculosa lentis may extend across the iris or from the iris to the cornea, often producing a corneal opacity at the site. A common defect in dogs, particularly in Basenjis.
the portion of iris closest to the pupillary border.