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The pupil constricts when the iris sphincter muscle is stimulated and contracts. In humans, it functions to constrict the pupil in bright light (pupillary light reflex) or during accommodation. [citation needed] In lower animals, the muscle cells themselves are photosensitive causing iris action without brain input. [5]
The iris (brown coloured portion of the eye) controls the size of the pupil by contracting the sphincter pupillae and dilator pupillae muscles. The sphincter pupillae is the opposing muscle of the dilator pupillae. The pupil's diameter, and thus the inner border of the iris, changes size when constricting or dilating.
The intraocular muscles are responsible for the protraction and retraction of the eyelids and reaction to light and pupil accommodation. [2] They're different to the extraocular muscles that are outside of the eye and control the external movement of the eye. [2] There are three intrisic ocular muscles: the ciliary muscle, pupillary sphincter ...
The pupil of the human eye can range in size from 2 mm to over 8 mm to adapt to the environment. The human eye can detect a luminance from 10 −6 cd/m 2, or one millionth (0.000001) of a candela per square meter to 10 8 cd/m 2 or one hundred million (100,000,000) candelas per square meter.
It also changes the shape of the lens within the eye but not the size of the pupil [5] which is carried out by the sphincter pupillae muscle and dilator pupillae. The ciliary muscle, pupillary sphincter muscle and pupillary dilator muscle sometimes are called intrinsic ocular muscles [6] or intraocular muscles. [7]
The visual system includes the eyes, the connecting pathways through to the visual cortex and other parts of the brain (human system shown). The eye is the sensory organ of the visual system. The iris , pupil , and sclera are visible
Light enters the eye through the pupil, and the iris regulates the amount of light by controlling the size of the pupil. This is known as the pupillary light reflex. The iris contains two groups of smooth muscles; a circular group called the sphincter pupillae, and a radial group called the dilator pupillae. When the sphincter pupillae contract ...
Blue eyes and the eyes of albinos, however, lack pigment. Structure of the iris and surrounding parts showing the stroma of iris ( stroma iridis ). The stroma connects to a sphincter muscle ( sphincter pupillae ), which contracts the pupil in a circular motion, and a set of dilator muscles ( dilator pupillae ) which pull the iris radially to ...