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Pupil Anatomical basics, Physiology, Clinicals

Pupil Anatomical basics, Physiology, Clinicals . Dr. Qumber Abbas, M.B.B.S Eye Unit 1 Services Hospital Lahore,2004. Insight into pupil. Anatomical Basics. Mesenchyme on the anterior surface of the lens condenses to form pupillary membrane.

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Pupil Anatomical basics, Physiology, Clinicals

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  1. Pupil Anatomical basics, Physiology, Clinicals Dr. Qumber Abbas, M.B.B.S Eye Unit 1 Services Hospital Lahore,2004 Insight into pupil

  2. AnatomicalBasics • Mesenchyme on the anterior surface of the lens condenses to form pupillary membrane. • The two layers of the neuroectoderm forming the edge of the optic cup now extend onto the posterior surface of pupillary membrane. These structures fuse to become iris. • The opening in the central part of iris becomes the pupil • At about 8 month the pupillary membrane starts to degenerate and disappear. Insight into pupil

  3. Pupilmovements • Miosis (contraction) • Sphincter pupillae constricts the pupil in bright light and during accomodation • In response to parasympathetic activity • Mediated by muscarinic receptor (M) • Chemical mediator is acetylcholine • Mydricyl is a muscarinic antagonist • Mydriasis (dilation) • Dilator pupillae dilates pupil in dim light and during excitment and fear • Occurs in response to sympathetic activity • Mediated by adrenergic receptors (a) • Chemical mediator is norepinephrine • Isonephrine is an adrenergic agonist Insight into pupil

  4. Direct and consensual light reflex

  5. Accomodation reflex • Afferent impulses travel from retina through optic nerve, optic chiasma and optic tract, lateral geniculate body and optic radiation to visual cortex • The visual cortex is connected to the eye field of the frontal cortex. • From here, the cortical fibers descend via the internal capsule to the oculomotor nuclei in midbrain. • IIIrd nerve travel to the medial rectus muscles. • Some of the descending cortical fibers synapse with the parasympathetic nuclei of oculomotor nerves of both sides. Insight into pupil

  6. Functions of the pupil Control of retinal illumination Depth of focus Reduction in optical aberrations Insight into pupil

  7. Clinical importance of the pupil Pupil inequality (anisocoria) as a reflection of autonomic Nerve input to each iris Pupil movement Objective indicator of light input Pharmacological indicator Testing of denervation super sensitivity Localization of sympathetic denervation Testing of drug treatment in psychiatric disorders Pupil diameter as an indicator of wakefulness Insight into pupil

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