Anatomy Learning Tool

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A brief introduction

Welcome to an overview for the sense of vision  

EYE The eye, a part of the sensory nervous system, is the organ responsible for humans' conscious sense of light and visibility. It has the ability to phototransduce, which is the conversion of photon energy into an integrated neural signal that passes through the optic nerve as an action potential to the visual cortex of the brain. The processing of the brain information there results in the senses of colour, luminance, contrast, and dimension (Nguyen and Duong, 2020). ANATOMY OF THE EYE The eye is a three-layered sphere of fluid-filled tissue. The outer layer is called fibrous tunic and is made up of the sclera, a hard, white, fibrous substance. The cornea, a specialised transparent tissue that allows light to enter the eye, replaces this opaque outer layer at the front of the eye. The iris, ciliary body, and choroid are three separate but connected structures that make up the middle layer of tissue. The coloured area of the eye that is visible through the cornea is called the iris. It has 2 pairs of muscles with opposit functions to one another, allowing the pupil's size to be changed under neurological control (Purves et al., 2001). The inner layer of the eyeball is the retina and it consists grossly of two functional parts with distinct locations: the optic and nonvisual parts. The optic part of the retina is sensitive to visual light rays and has two layers: a neural layer and pigmented layer. The neural layer is light receptive. The pigmented layer consists of a single layer of cells that reinforces the light-absorbing property of the choroid in reducing the scattering of light in the eyeball (Clinically oriented anatomy book). Structure of the eye Six cranial nerves innervate the motor, sensory, and autonomic components in the eyes. The six cranial nerves are the facial nerve, abducens nerve, trigeminal nerve, trochlear nerve, optic nerve, and oculomotor nerve (CN II–CN VI and CN VII).  The optic nerve detects the incoming light and transfers the image seen on the retina to the cerebral brain (Smith and Czyz, 2022). The superior, medial and inferior rectus, inferior oblique, levator palpebrae superioris, ciliary, and sphincter are among the extraocular muscles of the eyes that are innervated by the oculomotor nerve.  The superior oblique muscle causes the eye to torque inferiorly and inward, is motorily innervated by the trochlear nerve (Kim, Motlagh and Naqvi, 2022). The ophthalmic branch (CN V1), maxillary branch (CN V2), and mandibular branch (CN V3) are the three divisions of the trigeminal nerve (CN V). However, the eye is innervated by the trigeminal nerve's ophthalmic branch (Huff and Daly, 2021). The lateral rectus muscle, which permits abduction on the eye, is innervated by the abducens nerve (Nguyen, Reddy and Varacallo, 2020). the facial nerve innervates the orbicularis oculi muscle, which is responsible for eye closure and blinking (Dulak and Naqvi, 2021). • The lacrimal nerve, which arises in the lateral wall of the cavernous sinus and passes to the lacrimal gland, giving sensory branches to the conjunctiva and skin of the superior eyelid; its distal part also carries secretomotor fibers conveyed to it from the zygomatic nerve (CN V2). • The frontal nerve, which enters the orbit through the superior orbital fissure and divides into the supra-orbital and supratrochlear nerves, providing sensory innervation to the superior eyelid, scalp, and forehead • The nasociliary nerve, the sensory nerve to the eyeball, which also supplies several branches to the orbit, face, paranasal sinuses, nasal cavity, and anterior cranial fossa. The infratrochlear nerve, a terminal branch of the nasociliary nerve, supplies the eyelids, conjunctiva, etc. The ciliary muscle is a smooth muscle ring that controls accommodation by altering the shape of the lens, as well as controlling the flow of aqueous humor into Schlemm's canal. The ciliary muscle is attached to the zonular fibers, which...

The human eyeball consists of three main layers of the eye are: (1) the outermost supporting layer, which is composed of the clear cornea, the opaque sclera, and their zone of interdigitation, known as the limbus; (2) the middle uveal layer, which is composed of the iris, ciliary body, and choroid and constitutes the central vascular layer of the globe; and (3) the interior layer, which is commonly referred to as the retina.  

Glaucoma is an irreversible, progressive optic neuropathies caused by high intraocular pressure, which can result in significant vision field loss and blindness. Older age, black race, Hispanic origin, family history of glaucoma, and diabetes mellitus are all risk factors for primary open-angle glaucoma.

The Schlemm's canal is a ring-shaped, endothelium-lined vessel that surrounds the cornea. It is located against the trabecular meshwork's juxtacanalicular area. Following filtering via the trabecular meshwork, one of its primary functions is to transfer aqueous humour into the collecting channels.

There are seven extraocular muscles. There are a total of four rectus muscles, two oblique muscles, and the standalone levator palpebrae superioris. The four rectus muscles are the medial rectus, lateral rectus, superior rectus, and inferior rectus. The oblique muscles are the superior and inferior obliques. Levator palpabrae superioris acts to elevate the superior eyelid. Superior oblique acts to abduct, depress and rotate the eyeball medially. Inferior oblique acts to abduct, elevate and rotate the eyeball laterally. Superior rectus acts elevate, adduct and rotate the eyeball medially. Inferior rectus acts depress, adduct and rotate the eyeball laterally. Medial rectus acts to adduct the eyeball. Lateral rectus acts to abdoct the eyeball.