During the tenth week of development in humans (time varies depending on species), the lens grows independent of a blood supply and the hyaloid artery usually regresses. Its proximal portion remains as the central artery of the retina. Regression of the hyaloid artery leaves a clear central zone through the vitreous humor, called the hyaloid canal or Cloquet's canal. Cloquet's canal is named after the French physician Jules Germain Cloquet (1790–1883) who first described it.
Occasionally the artery may not fully regress, resulting in the condition persistent hyaloid artery. More commonly, small remnants of the artery may remain. Free remnants can sometimes be seen as "floaters". An anterior remnant of the hyaloid artery can be seen in some people as Mittendorf's dot, a small pinpoint-like scar on the posterior surface of the lens.[1] A posterior remnant may be seen where the artery left the optic disc, and is known as Bergmeister's papilla.
The optic nerve, also known as cranial nerve II, or simply as CN II, is a paired cranial nerve that transmits visual information from the retina to the brain. In humans, the optic nerve is derived from optic stalks during the seventh week of development and is composed of retinal ganglion cell axons and glial cells; it extends from the optic disc to the optic chiasma and continues as the optic tract to the lateral geniculate nucleus, pretectal nuclei, and superior colliculus.
Eye floaters are sometimes visible deposits within the eye's vitreous humour, which is normally transparent, or between the vitreous and retina. Each floater can be measured by its size, shape, consistency, refractive index, and motility. They are also called muscae volitantes, or mouches volantes. The vitreous usually starts out transparent, but imperfections may gradually develop as one ages. The common type of floater, present in most people's eyes, is due to these degenerative changes of the vitreous. The perception of floaters, which may be annoying or problematic to some people, is known as myodesopsia, or, less commonly, as myodaeopsia, myiodeopsia, or myiodesopsia. It is not often treated, except in severe cases, where vitrectomy (surgery), laser vitreolysis, and medication may be effective.
The lens is a transparent biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. By changing shape, it functions to change the focal length of the eye so that it can focus on objects at various distances, thus allowing a sharp real image of the object of interest to be formed on the retina. This adjustment of the lens is known as accommodation. Accommodation is similar to the focusing of a photographic camera via movement of its lenses. The lens is more flat on its anterior side than on its posterior side.
The vitreous body is the clear gel that fills the space between the lens and the retina of the eyeball of humans and other vertebrates. It is often referred to as the vitreous humor or simply "the vitreous".
Eye surgery, also known as ocular surgery, is surgery performed on the eye or its adnexa, typically by an ophthalmologist. The eye is a very fragile organ, and requires extreme care before, during, and after a surgical procedure to minimise or prevent further damage. An expert eye surgeon is responsible for selecting the appropriate surgical procedure for the patient, and for taking the necessary safety precautions. Mentions of eye surgery can be found in several ancient texts dating back as early as 1800 BC, with cataract treatment starting in the fifth century BC. Today it continues to be a widely practiced type of surgery, with various techniques having been developed for treating eye problems.
The aqueous humour is a transparent watery fluid similar to plasma, but containing low protein concentrations. It is secreted from the Ciliary body, a structure supporting the lens. It fills both the anterior and the posterior chambers of the eye, and is not to be confused with the vitreous humour, which is located in the space between the lens and the retina, also known as the posterior cavity or vitreous chamber.
The middle meningeal artery is typically the third branch of the first portion of the maxillary artery. After branching off the maxillary artery in the infratemporal fossa, it runs through the foramen spinosum to supply the dura mater and the calvaria. The middle meningeal artery is the largest of the three (paired) arteries that supply the meninges, the others being the anterior meningeal artery and the posterior meningeal artery.
Entoptic phenomena are visual effects whose source is within the eye itself.
The ophthalmic artery (OA) is the first branch of the internal carotid artery distal to the cavernous sinus. Branches of the OA supply all the structures in the orbit as well as some structures in the nose, face and meninges. Occlusion of the OA or its branches can produce sight-threatening conditions.
The central retinal artery branches off the ophthalmic artery, running inferior to the optic nerve within its dural sheath to the eyeball.
A posterior vitreous detachment (PVD) is a condition of the eye in which the vitreous membrane separates from the retina. It refers to the separation of the posterior hyaloid membrane from the retina anywhere posterior to the vitreous base.
The posterior cerebral artery (PCA) is one of a pair of arteries that supply oxygenated blood to the occipital lobe, part of the back of the human brain. The two arteries originate from the distal end of the basilar artery, where it bifurcates into the left and right posterior cerebral arteries. These anastomose with the middle cerebral arteries and internal carotid arteries via the posterior communicating arteries.
The middle cranial fossa, deeper than the anterior cranial fossa, is narrow medially and widens laterally to the sides of the skull. It is separated from the posterior fossa by the clivus and the petrous crest.
Optic disc drusen (ODD) are globules of mucoproteins and mucopolysaccharides that progressively calcify in the optic disc. They are thought to be the remnants of the axonal transport system of degenerated retinal ganglion cells. ODD have also been referred to as congenitally elevated or anomalous discs, pseudopapilledema, pseudoneuritis, buried disc drusen, and disc hyaline bodies.
The vitreous chamber is the space in the eye occupied by vitreous humor.
Hyaloid canal is a small transparent canal running through the vitreous body from the optic nerve disc to the lens. It is formed by an invagination of the hyaloid membrane, which encloses the vitreous body.
Mammals normally have a pair of eyes. Although mammalian vision is not so excellent as bird vision, it is at least dichromatic for most of mammalian species, with certain families possessing a trichromatic color perception.
Bergmeister's papilla arises from the centre of the optic disc, consists of a small tuft of fibrous tissue and represents a remnant of the fetal hyaloid artery.
Persistent hyperplastic primary vitreous (PHPV), also known as persistent fetal vasculature (PFV), is a rare congenital developmental anomaly of the eye that results following failure of the embryological, primary vitreous and hyaloid vasculature to regress. It can be present in three forms: purely anterior, purely posterior and a combination of both. Most examples of PHPV are unilateral and non-hereditary. When bilateral, PHPV may follow an autosomal recessive or autosomal dominant inheritance pattern.
Sickle cell retinopathy is a major ocular complication of the sickle cell disease (SCD) which causes permanent loss of vision. Retinopathy can occur in sickling hemoglobinopathies like sickle cell disease, sickle cell C disease, and sickle cell thalassaemia disease.
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