"+/– 0.33 mm error, when compared to measurements of the anterior chamber depth by Scheimpflug photography. One peculiar feature of the anterior chamber is dampened immune response to allogenic grafts. This is called ""anterior chamber associated immune deviation"" (ACAID), a term introduced in 1981 by Streilein et al. This phenomenon is relevant to the fact that the eye is considered an ""immune privileged site"", like the brain and the testis. Anterior chamber of eyeball The anterior chamber (AC) is the aqueous humor-filled space inside the eye between the iris and the cornea's innermost surface, the endothelium. Hyphema, anterior uveitis and"
"membrane called the conjunctiva. It helps lubricate the eye by producing mucus and tears. It also contributes to immune surveillance and helps to prevent the entrance of microbes into the eye. In many animals, including humans, eyelids wipe the eye and prevent dehydration. They spread tears on the eyes, which contains substances which help fight bacterial infection as part of the immune system. Some species have a nictitating membrane for further protection. Some aquatic animals have a second eyelid in each eye which refracts the light and helps them see clearly both above and below water. Most creatures will automatically"
"other vertebrates. The outer layer of the eye consists of the transparent cornea at the front, and two layers of sclera — a tough white collagen fibre layer which surrounds the rest of the eye and supports and protects the eye as a whole. The eye is divided internally by the lens into two main segments: the anterior segment and the posterior segment. The anterior chamber is filled with a watery fluid called the aqueous humour, and the posterior chamber contains the vitreous humour, a clear jelly-like substance. The lens is a transparent convex or 'lens' shaped body with a"
"Vitreous membrane The vitreous membrane (or hyaloid membrane or vitreous cortex) is a layer of collagen separating the vitreous humour from the rest of the eye. At least two parts have been identified anatomically. The posterior hyaloid membrane separates the rear of the vitreous from the retina. It is a false anatomical membrane. The anterior hyaloid membrane separates the front of the vitreous from the lens. Bernal et al. describe it ""as a delicate structure in the form of a thin layer that runs from the pars plana to the posterior lens, where it shares its attachment with the posterior"
"Uvea The uvea (/ˈjuːvɪə/) (Lat. ""uva"", grape), also called the ""uveal layer"", ""uveal coat"", ""uveal tract"", ""vascular tunic"" or ""vascular layer"" is the pigmented middle of the three concentric layers that make up an eye. The name is possibly a reference to its reddish-blue or almost black colour, wrinkled appearance and grape-like size and shape when stripped intact from a cadaveric eye. Its use as a technical term in anatomy and ophthalmology is relatively modern. The uvea is the vascular middle layer of the eye. It is traditionally divided into three areas, from front to back, the: The prime functions"
"Orbital septum The orbital septum (Palpebral fascia) is a membranous sheet that acts as the anterior boundary of the orbit. It extends from the orbital rims to the eyelids. It forms the fibrous portion of the eyelids. In the upper eyelid, the orbital septum blends with the tendon of the levator palpebrae superioris, and in the lower eyelid with the tarsal plate. When the eyes are closed, the whole orbital opening is covered by the septum and tarsi. Medially it is thin, and, becoming separated from the medial palpebral ligament, attaches to the lacrimal bone at its posterior crest. The"
"zonule via Wieger’s ligament, also known as Egger’s line"". Vitreous membrane The vitreous membrane (or hyaloid membrane or vitreous cortex) is a layer of collagen separating the vitreous humour from the rest of the eye. At least two parts have been identified anatomically. The posterior hyaloid membrane separates the rear of the vitreous from the retina. It is a false anatomical membrane. The anterior hyaloid membrane separates the front of the vitreous from the lens. Bernal et al. describe it ""as a delicate structure in the form of a thin layer that runs from the pars plana to the posterior"
"be capable of making one cadaver-donor's corneal cells be expanded and be usable in more than one patient's eye. Cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. The cornea, with the anterior chamber and lens, refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is approximately 43 dioptres. The cornea can be reshaped by surgical procedures such as LASIK. While the cornea contributes most of the eye's focusing power, its focus is fixed. Accommodation (the"
"Nictitating membrane The nictitating membrane (from Latin ""nictare"", to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye from the medial canthus for protection and to moisten it while maintaining vision. Some reptiles, birds, and sharks have full nictitating membranes; in many mammals, a small, vestigial portion of the membrane remains in the corner of the eye. Some mammals, such as camels, polar bears, seals and aardvarks, have full nictitating membranes. Often called a third eyelid or haw, it may be referred to in scientific terminology as the ""plica semilunaris"","
"can be prone to prolapse of the gland of the third eyelid, resulting in a condition called cherry eye. Nictitating membrane The nictitating membrane (from Latin ""nictare"", to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye from the medial canthus for protection and to moisten it while maintaining vision. Some reptiles, birds, and sharks have full nictitating membranes; in many mammals, a small, vestigial portion of the membrane remains in the corner of the eye. Some mammals, such as camels, polar bears, seals and aardvarks, have full nictitating membranes."
"the ventral part along the length of the tube. The Joseph cells extend from the caudal end of the anterior vesicle (or cerebral vesicle) to the boundary between myomeres 3 and 4, where the Hesse organs begin and continue nearly to the tail. The frontal eye consists of a pigment cup, a group of putative photoreceptor cells (termed ""Row 1""), three rows of neurons (""Rows 2–4""), and glial cells. The frontal eye, which expresses the PAX6 gene, has been proposed as the homolog of vertebrate paired eyes, the pigment cup as the homolog of the RPE (retinal pigment epithelium), the"
"Cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. The cornea, with the anterior chamber and lens, refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is approximately 43 dioptres. The cornea can be reshaped by surgical procedures such as LASIK. While the cornea contributes most of the eye's focusing power, its focus is fixed. Accommodation (the refocusing of light to better view near objects) is accomplished by changing the geometry of the lens. Medical terms"
"is separated from the anterior margin by a very conspicuous narrow convex preglabellar field that is lower than and does not reach the adjacent cheeks (or genae). To the back of the glabella, the occipital ring is distinct. Without eyes but for one known exception. The eye ridges (when present) are threadlike, evenly curved, extending from the anterior corners of the glabella to the genal angles. The anterior cephalic border furrow is deep, concave and wider than the narrow convex border itself. The lateral cephalic border is divided longitudinally by a suture and is continued into slender, backward-directed genal spines,"
"as the ""aquula"" (Latin, ""a little stream"", dim. of ""aqua"", ""water"") or ""crystalline lens"". The lens is part of the anterior segment of the human eye. In front of the lens is the iris, which regulates the amount of light entering into the eye. The lens is suspended in place by the suspensory ligament of the lens, a ring of fibrous tissue that attaches to the lens at its equator and connects it to the ciliary body. Posterior to the lens is the vitreous body, which, along with the aqueous humor on the anterior surface, bathes the lens. The lens"
"LASIK procedures. This complication is not present in PRK or other non-flap vision correction procedures. Corneal epithelium The corneal epithelium (epithelium corneæ anterior layer) is made up of epithelial tissue and covers the front of the cornea. It acts as a barrier to protect the cornea, resisting the free flow of fluids from the tears, and prevents bacteria from entering the epithelium and corneal stroma. The corneal epithelium consists of several layers of cells. The cells of the deepest layer are columnar, known as basal cells. Then follow two or three layers of polyhedral cells, commonly known as wing cells."
"upper one is the frontal region, which has continuity with the apex, the orbital region and the gena, 2. the lower one, the face or clypeus, contains the insertion of the antennae and ends with the epistomal edge which comprises the upper lip. The eyes are usually very obvious, but reach a remarkable development in the Brachycera. In this suborder the eyes are markedly convex and have grown to occupy most of the side of the head. The space between the two eyes can sometimes be reduced to a narrow strip running from the front of the occipital region, or"
"Posterior segment of eyeball The posterior segment or posterior cavity is the back two-thirds of the eye that includes the anterior hyaloid membrane and all of the optical structures behind it: the vitreous humor, retina, choroid, and optic nerve. The portion of the posterior segment visible during ophthalmoscopy (or fundoscopy) is sometimes referred to as the posterior pole, or fundus. Some ophthalmologists specialize in the treatment and management of posterior segment disorders and diseases. In some animals, the retina contains a reflective layer (the tapetum lucidum) which increases the amount of light each photosensitive cell perceives, allowing the animal to"
"membrane 3. Stroma 4. Pre Descemets layer 5. Descemet's membrane 6. Endothelium For the human eye to see, the cornea or the front window of the eye should be clear or transparent. For that to happen the inside corneal layer the endothelium pumps out water from the cornea so that the cornea remains transparent and light can pass into the eye and one can see. If the endothelium is bad the cornea starts having lot of water and gets damaged which is called Bullous Keratoplasty. Thus PDEK helps in replacing the non function endothelium in bullous keratopathy. Prof Amar Agarwal"
"membrane or opaque fluid that rested between the lens and the pupil. The method for treating cataracts in medieval Islam (known in English as couching) was known through translations of earlier publishings on the technique. A small incision was made in the sclera with a lancet and a probe was then inserted and used to depress the lens, pushing it to one side of the eye. After the procedure was complete, the eye was then washed with salt water and then bandaged with cotton wool soaked in oil of roses and egg whites. After the operation, there was concern that"
"""membrana nictitans"", or ""palpebra tertia"". The nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining vision. The term comes from the Latin word ""nictare"", meaning ""to blink"". It is often called a ""third eyelid"" or ""haw"", and may be referred to in scientific terminology as the ""plica semilunaris"", ""membrana nictitans"", or ""palpebra tertia"". Unlike the upper and lower eyelids, the nictitating membrane moves horizontally across the eyeball. In many species, any stimulus to the eyeball (such as a puff of air)"
"layer, known as the fibrous tunic, is composed of the cornea and sclera. The middle layer, known as the vascular tunic or uvea, consists of the choroid, ciliary body, pigmented epithelium and iris. The innermost is the retina, which gets its oxygenation from the blood vessels of the choroid (posteriorly) as well as the retinal vessels (anteriorly). The spaces of the eye are filled with the aqueous humour anteriorly, between the cornea and lens, and the vitreous body, a jelly-like substance, behind the lens, filling the entire posterior cavity. The aqueous humour is a clear watery fluid that is contained"
"Conjunctiva The conjunctiva lines the inside of the eyelids and covers the sclera (the white of the eye). It is composed of non-keratinized, stratified squamous epithelium with goblet cells, and also stratified columnar epithelium. The conjunctiva is highly vascularised, with many microvessels easily accessible for imaging studies. The conjunctiva is typically divided into three parts: Blood to the bulbar conjunctiva is primarily derived from the ophthalmic artery. The blood supply to the palpebral conjunctiva (the eyelid) is derived from the external carotid artery. However, the circulation of the bulbar conjunctiva and palpebral conjunctiva are linked, so both bulbar conjunctival and"
"of the size of the pupil, regulation and suppression of the hormone melatonin and entrainment of the body clock. The eye is not shaped like a perfect sphere, rather it is a fused two-piece unit, composed of the anterior segment and the posterior segment. The anterior segment is made up of the cornea, iris and lens. The cornea is transparent and more curved, and is linked to the larger posterior segment, composed of the vitreous, retina, choroid and the outer white shell called the sclera. The cornea is typically about 11.5 mm (0.3 in) in diameter, and 1/2 mm (500"
"in Bruch's membrane which may lead to choroidal neovascularization. Alport's Syndrome, a genetic disorder affecting the alpha(IV) collagen chains, can also lead to defects in the Bruch membrane such as 'dot and fleck' retinopathy. Bruch's membrane was named after the German anatomist Karl Wilhelm Ludwig Bruch. Bruch's membrane Bruch's membrane is the innermost layer of the choroid. It is also called the ""vitreous lamina"", because of its glassy microscopic appearance. It is 2–4 μm thick. Bruch's membrane consists of five layers (from inside to outside): The retinal pigment epithelium transports metabolic waste from the photoreceptors across Bruch's membrane to the"
"Eyelid An eyelid is a thin fold of skin that covers and protects the human eye. The levator palpebrae superioris muscle retracts the eyelid, exposing the cornea to the outside, giving vision. This can be either voluntarily or involuntarily. The human eyelid features a row of eyelashes along the eyelid margin, which serve to heighten the protection of the eye from dust and foreign debris, as well as from perspiration. ""Palpebral"" (and ""blepharal"") means relating to the eyelids. Its key function is to regularly spread the tears and other secretions on the eye surface to keep it moist, since the"
"in blinking. Instead the eye is lubricated by the nictitating membrane, a third concealed eyelid that sweeps horizontally across the eye like a windscreen wiper. The nictitating membrane also covers the eye and acts as a contact lens in many aquatic birds when they are under water. When sleeping, the lower eyelid rises to cover the eye in most birds, with the exception of the horned owls where the upper eyelid is mobile. The eye is also cleaned by tear secretions from the lachrymal gland and protected by an oily substance from the Harderian glands which coats the cornea and"
"of the external eye muscles) may be less complete, however. Tenon's capsule The fascia bulbi (also known as the capsule of Tenon and the bulbar sheath) is a thin membrane which envelops the eyeball from the optic nerve to the limbus, separating it from the orbital fat and forming a socket in which it moves. Its inner surface is smooth, and is separated from the outer surface of the sclera by the periscleral lymph space. This lymph space is continuous with the subdural and subarachnoid cavities, and is traversed by delicate bands of connective tissue which extend between the fascia"
"see better under low light conditions. Posterior segment of eyeball The posterior segment or posterior cavity is the back two-thirds of the eye that includes the anterior hyaloid membrane and all of the optical structures behind it: the vitreous humor, retina, choroid, and optic nerve. The portion of the posterior segment visible during ophthalmoscopy (or fundoscopy) is sometimes referred to as the posterior pole, or fundus. Some ophthalmologists specialize in the treatment and management of posterior segment disorders and diseases. In some animals, the retina contains a reflective layer (the tapetum lucidum) which increases the amount of light each photosensitive"
"Crypts of Henle Crypts of Henle are microscopic pockets found in scattered sections of the conjunctiva around the eyeball. They are responsible for secreting mucin, a proteinous substance that makes up the inner layer of tears. It coats the cornea to provide a hydrophilic layer that allows for even distribution of the tear film. The layer of mucin allows tears to glide evenly across the eye’s surface. The crypts of Henle are named after German anatomist Friedrich Gustav Jakob Henle (1809-1885). Another anatomical structure called the ""glands of Manz"" perform a similar function. They are located in the eyeball's conjunctiva,"
"are completely reduced. Above these are antenna1 bristles closer to (but still some distance from) the margin of eyes. Three bristles are spaced along the margin of eyes-anterolateral midlateral and posterolateral. Immediately before the ocellar callus are two preocellar bristles. The ocellar callus bears a pair of ocellar bristles and in some genera between the antennae and the preocellar bristles two additional, intermediate bristles occur. The convex mesonotum is usually covered with hairs and rows of bristles. An important taxonomic character is the precise location of the anterior spiracles on the pleura of the thorax. The metapleuron may be entire"
"subdivided by a narrow oblique fissure, the superior meatus of the nose, bounded above by a thin, curved plate, the superior nasal concha; the posterior ethmoidal cells open into this meatus. Below, and in front of the superior meatus, is the convex surface of the middle nasal concha; it extends along the whole length of the medial surface of the labyrinth, and its lower margin is free and thick. The lateral surface of the middle concha is concave, and assists in forming the middle meatus of the nose. The middle ethmoidal cells open into the central part of this meatus,"
"the eye slightly outward to the rear margin of the cephalon (a state called opisthoparian) opposite the base of the pleural spines. From the front of the eye the suture describes a slight S-curve forward cutting the front margin in front of the eye. The central raised area of the cephalon (or glabella) is divided in the occipital ring furthest to the back, followed by the first lobe that is, like the occipital ring, defined by a furrow across the midline and two more lobes that have furrows that do not connect across the midline. The frontal lobe is the"
"the patient's eye. The normal cornea (Fig 1) has from the front to the back the following layers: 1. Epithelium 2. Bowmans membrane 3. Stroma 4. Pre Descemets layer 5. Descemets membrane 6. Endothelium For the human eye to see, the cornea or the front window of the eye should be clear or transparent. For that to happen the inside corneal layer the endothelium pumps out water from the cornea so that the cornea remains transparent and light can pass into the eye and one can see. If the endothelium is bad the cornea starts having lot of water and"