BAG OF STATEMENTS FOR EYES


 * Refracting Media | The Accessory Organs of the Eye | Normal values of the eyeHOLES

=SIMAPLIFIED SENTENCES FROM GRAY and other sources= WE NEED ID's for these SIMPLE STATEMENTS to REFER TO them in general communication. SIMPLE SENTENCE is the minimum piece of knowledge.
 * 1) Henry Gray (1821–1865). Anatomy of the Human Body.  1918. http://221.186.138.155/project/vbob/GraysAnatomy2/contents.html
 * 2) * Tunic of the eye: this page
 * 3) * Refracting Media
 * 4) * The Accessory Organs of the Eye
 * 5) *Nerves of the eyes
 * 6) **CN2Optic nerve
 * 7) **CN3Occulomotor Nerve
 * 8) **CN4Trochlear nerve
 * 9) **CN5Trigeminal Nerve
 * 10) **CN5-3 Mandibular nerve
 * 11) Normal values of the eye
 * 12) Pocket Atlas of Pocket Atlas of Human Anatomy: Based on the International Nomenclature (Thieme Flexibook) Heinz Feneis http://www.amazon.co.jp/dp/0865779287
 * 13) *Feneis atlas Items for eye
 * 14) *Feneis atlas Items for heart artery vein lymph
 * 15) *mapping FENEIS to FMA
 * 16) *Arteries of brain
 * 17) *Artery of brain from At a Glans
 * ex) Your observation is against "The knowledge ID KID12345"
 * ex) this figure fulfills the KID1234,KID2323,...

1. The Tunics of the Eye

 * The Tunics of the Eye is made up with fibrous tunic + vascular tunic + nervous tunic.
 * A fibrous tunic of the eye, (Fig. 869) is made up with the sclera behind and the cornea in front;
 * a vascular pigmented tunic of the eye ,is made up with, the choroid,behind + ciliary body, middle and iris, behind;
 * a nervous tunic of the eye is made up with the retina.	  1
 * The Fibrous Tunic is AKA tunica fibrosa oculi
 * the sclera is opaque
 * the sclera constitutes the posterior five-sixths of the tunic of the eye;
 * the cornea is transparent, and forms the anterior sixth.	  2
 * The sclera has received its name from its extreme density and hardness;
 * The sclera is a firm, unyielding membrane,
 * The sclera is serving to maintain the form of the bulb.
 * The sclera is much thicker behind than in front;
 * the thickness of The sclera 's posterior part is 1 mm.
 * The sclera 's external surface is of white color,
 * The sclera 's external surface is in contact with the inner surface of the fascia of the bulb;
 * The sclera 's external surface is quite smooth, except at the points where the Recti and Obliqui are inserted into it;
 * The sclera 's anterior part is covered by the conjunctival membrane.
 * The sclera 's inner surface is brown in color
 * The sclera 's inner surface is marked by grooves--in which the ciliary nerves and vessels are lodged;
 * The sclera 's inner surface it is separated from the outer surface of the choroid by an extensive lymph space (spatium perichorioideale)
 * spatium perichorioideale is traversed by the lamina suprachorioidea.
 * the lamina suprachorioidea is an exceedingly fine cellular tissue
 * Behind The sclera is pierced by the optic nerve,
 * The sclera is continuous with the dura mater through the fibrous sheath of the optic nerve.
 * the sclera forms the lamina cribrosa scleræ Where the optic nerve passes through the sclera,
 * the minute orifices in the lamina cribrosa scleræ serve for the transmission of the nervous filaments,
 * and the fibrous septa dividing the minute orifices in the lamina cribrosa scleræ from one another are continuous with the membranous processes which separate the bundles of nerve fibers.
 * The largest orifices in the lamina cribrosa scleræ occupies the center of the lamina;
 * The largest orifices in the lamina cribrosa scleræ transmits the central artery and vein of the retina.
 * Around the entrance of the optic nerve are numerous small apertures for the transmission of the ciliary vessels and nerves,
 * four or five large apertures for the transmission of veins (venæ vorticosæ) locates in the midway between lamina cribrosa scleræ and the sclerocorneal junction.
 * the sclera is directly continuous with the cornea In front.
 * the sclero-corneal junction is junction of the corne and sclera.
 * In the inner part of the sclera close to this junction is a circular canal,
 * the sinus venosus scleræ is a ciecular canal close to the inner part of the sclero-corneal junction.
 * the sinus venosus scleræ is AKA canal of Schlemm
 * In a meridional section of this region this sinus presents the appearance of a cleft, the outer wall of which consists of the firm tissue of the sclera, while its inner wall is formed by * a triangular mass of trabecular tissue (Fig. 870); the apex of the mass is directed forward
 * a triangular mass of trabecular tissue is continuous with the posterior elastic lamina of the cornea.
 * The sinus is lined by endothelium and communicates externally with the anterior ciliary veins.	  3
 * The aqueous humor drains into the scleral sinuses by passage through the “pectinate villi”
 * the pectinate villi are analogous to the arachnoid villi of the cerebral meninges, in structure and function.

http://www.bartleby.com/107/Images/large/image870.gif http://www.bartleby.com/107/Images/large/image872.gif http://lifesciencedb.jp/bp3d/API/animation.cgi?av=09051901&iw=320&ih=320&bcl=FFFFFF&cf=0&hf=0&model=bp3d&bv=4.0&tn=isa&dt=20130524101257&dp=1&cx=-0.7391&cy=-962.9532&cz=1575.31&tx=-0.7391&ty=-74.8972&tz=1575.31&ux=0&uy=0&uz=1&zm=4&cm=N&oid001=FMA72662&ocl001=f0d2a0&osz001=S&oop001=1.0&orp001=S&odcp001=0&oid002=FMA72977&ocl002=f0d2a0&osz002=S&oop002=1.0&orp002=S&odcp002=0&oid003=FMA67957&ocl003=BE7807&osz003=S&oop003=0.3&orp003=S&odcp003=0&dpl=0&dpod=1&dpol=0&crd=bp3d.gif
 * The sclera is formed of white fibrous tissue intermixed with fine elastic fibers; flattened connective-tissue corpuscles, some of which are pigmented, are contained in cell spaces between the fibers.
 * The sclera 's fibers are aggregated into bundles, which are arranged chiefly in a longitudinal direction.
 * The sclera 's vessels are not numerous, the capillaries being of small size, uniting at long and wide intervals.
 * The sclera 's nerves are derived from the ciliary nerves, but their exact mode of ending is not known.	  5

The Cornea.

 * The cornea is the projecting transparent part of the external tunic, and forms the anterior sixth of the surface of the bulb.
 * The Cornea is almost circular in outline, occasionally a little broader in the transverse than in the vertical direction.
 * The Cornea is convex anteriorly
 * The Cornea projects like a dome in front of the sclera.
 * The Cornea 's degree of curvature varies in different individuals, and in the same individual at different periods of life, being more pronounced in youth than in advanced life.
 * The cornea is dense and of uniform thickness throughout;
 * The Cornea 's posterior surface is perfectly circular in outline,
 * The Cornea 's posterior surface exceeds the anterior surface slightly in diameter.
 * the cornea bulges inward as a thickened rim, immediately in front of the sclero-corneal junction
 * there is a distinct furrow between the attachment of the iris and the sclero-corneal junction behind the cornea bulges inward as a thickened rim..
 * The furrow between the attachment of the iris and the sclero-corneal junction has been named as the sulcus circularis corneæ by Arthur Thomson
 * the sulcus circularis corneæ is bounded externally by the trabecular tissue already described as forming the inner wall of the sinus venosus scleræ.
 * Between this tissue and the anterior surface of the attached margin of the iris is an angular recess, named the iridial angle.
 * the iridial angle is AKA filtration angle of the eye (Fig. 870).
 * Immediately outside the filtration angle is a projecting rim of scleral tissue
 * which appears in a meridional section as a small triangular area, termed the scleral spur.
 * the scleral spur's base is continuous with the inner surface of the sclera immediately to the outer side of the filtration angle
 * the scleral spur's apex is directed forward and inward.
 * To the anterior sloping margin of this spur are attached the bundles of trabecular tissue just referred to; from its posterior margin the meridional fibers of the Ciliaris muscle arise.

Structure (Fig. 871).—


 * The cornea is made up with (1) the corneal epithelium, (2) the substantia propria (3) the posterior elastic lamina; and (4) the endothelium of the anterior chamber.
 * the corneal epithelium is continuous with the epithelium of the conjunctiva.
 * The corneal epithelium covers the front of the cornea
 * The corneal epithelium is made up with the several layers of cells.
 * The cells of the deepest layer of The corneal epitheliumare columnar;
 * the medial layer of the corneal epithelium is two or three layers of polyhedral cells,
 * the majority of the medial layer of the corneal epithelium are prickle cells similar to those found in the stratum mucosum of the cuticle.
 * The outer layer of The corneal epithelium three or four layers of squamous cells, with flattened nuclei.
 * The substantia propria of the cornea is fibrous, tough, unyielding, and perfectly transparent.
 * The substantia propria of the cornea is composed of about sixty flattened lamellæ, superimposed one on another.
 * the lamellæ of The substantia propria of the cornea are made up of bundles of modified connective tissue,
 * the fibers in the lamellæ of The substantia propria of the corneaof which are directly continuous with those of the sclera.
 * The fibers of each lamella of the substantia propria of the cornea are for the most part parallel with one another, but at right angles to those of adjacent lamellæ.
 * Fibers, however, frequently pass from one lamella to the next.	  9
 * The lamellæ are connected with each other by an interstitial cement substance, in which are spaces, the corneal spaces.
 * These are stellate in shape and communicate with one another by numerous offsets.
 * Each contains a cell, the corneal corpuscle, resembling in form the space in which it is lodged, but not entirely filling it.


 * The layer immediately beneath the corneal epithelium presents certain characteristics which have led some anatomists to regard it as a distinct membrane.
 * The layer immediately beneath the corneal epithelium has been named the anterior elastic lamina of the cornea
 * the anterior elastic lamina of the cornea is AKA lamina elastica anterior
 * the anterior elastic lamina of the cornea is AKA the anterior limiting layer
 * the anterior elastic lamina of the cornea is AKA  Bowman’s membrane
 *  Bowman’s membrane differs from the posterior elastic lamina, in presenting evidence of fibrillar structure, and in not having the same tendency to curl inward, or to undergo fracture, when detached from the other layers of the cornea.
 *  Bowman’s membrane consists of extremely closely interwoven fibrils, similar to those found in the substantia propria, but contains no corneal corpuscles. It may be regarded as a condensed part of the substantia propria.	  11
 * The posterior elastic lamina covers the posterior surface of the substantia propria, and is an elastic, transparent homogeneous membrane, of extreme thinness, which is not rendered opaque by either water, alcohol, or acids.
 * The posterior elastic lamina is AKA lamina elastica posterior;
 * The posterior elastic lamina is AKA membrane of Descemet
 * The posterior elastic lamina is AKA  membrane of Demours
 * membrane of Descemet curls up with the attached surface innermost, When stripped from the substantia propria.
 * At the margin of the cornea membrane of Descemet breaks up into fibers which form the trabecular tissue already described;
 * the spaces between the trabeculæ are termed the spaces of the angle of the iris.
 * the spaces of the angle of the iris is AKA the spaces of Fontana
 * the spaces of Fontana communicate with the sinus venosus scleræ
 * the spaces of Fontana communicate with  the anterior chamber at the filtration angle.
 * Some of the fibers of this trabecular tissue are continued into the substance of the iris, forming the pectinate ligament of the iris;
 * Some of the fibers of this trabecular tissue are connected with the forepart of the sclera and choroid.	  13
 * The endothelium of the anterior chamber is AKA endothelium cameræ anterioris;
 * The endothelium of the anterior chamber is AKA posterior layer of the cornea; * The endothelium of the anterior chamber is AKA corneal endothelium
 * corneal endothelium covers the posterior surface of the elastic lamina,
 * corneal endotheliumis reflected on to the front of the iris,
 * corneal endothelium lines the spaces of the angle of the iris;
 * corneal endotheliumis made up with a single stratum of polygonal, flattened, nucleated cells.

Vessels and Nerves

 * The cornea is a non-vascular structure
 * the capillary vessels ending in loops at the cornea's circumference are derived from the anterior ciliary arteries.
 * Lymphatic vessels have not yet been demonstrated in the cornea.
 * Lymphatic vessels of the cornea are represented by the channels in which the bundles of nerves run;
 * these channels are lined by an endothelium.
 * The nerves in the cornea are numerous.
 * The nerves in the cornea are derived from the ciliary nerves.
 * The nerves in the cornea form an annular plexus Around the periphery of the cornea * * annular plexus fibers of the cornea enter the substantia propria.
 * annular plexus fibers of the cornea lose their medullary sheaths
 * and ramify throughout its substance in a delicate net-work,
 * and their terminal filaments form a firm and closer plexus on the surface of the cornea proper, beneath the epithelium.
 * This is termed the subepithelial plexus,
 * from it fibrils are given off which ramify between the epithelial cells, forming an intraepithelial plexus.

The Vascular Tunic (tunica vasculosa oculi)

 * The vascular tunic of the eye is formed by the choroid,+ the ciliary body, + the iris.
 * The choroid invests the posterior five-sixths of the bulb,
 * The choroid extends as far forward as the ora serrata of the retina.
 * The ciliary body connects the choroid to the circumference of the iris.
 * The iris is a circular diaphragm behind the cornea,
 * The iris has a central hole, the pupil.

The Choroid (chorioidea).
http://www.bartleby.com/107/Images/large/image874.gif Tapetum.—This name is applied to the outer and posterior part of the choroid, which in many animals presents an iridescent appearance. 22
 * The choroid is a thin, highly vascular membrane, of a dark brown or chocolate color,
 * The choroid invests the posterior five-sixths of the globe
 * The choroid is pierced behind by the optic nerve
 * The choroid in this situation is firmly adherent to the sclera.
 * The choroid is thicker behind than in front.
 * The choroid 's outer surface is loosely connected by the lamina suprachorioidea with the sclera
 * The choroid 's inner surface is attached to the pigmented layer of the retina.	  18
 * The choroid consists mainly of a dense capillary plexus, and of small arteries and veins.
 *  the lamina suprachorioidea is a delicate non-vascular lamellæ on The choroid 's external surface.
 * each layer of  the lamina suprachorioidea consisting of a net-work of fine elastic fibers among which are branched pigment cells.
 * The spaces between the lamellæ are lined by endothelium,
 * The spaces between the lamellæ open freely into the perichoroidal lymph space,
 * which, in its turn, communicates with the periscleral space by the perforations in the sclera through which the vessels and nerves are transmitted.	  19
 * Internal to the lamina suprachorioidea is the choroid proper,
 * the choroid proper,is made up with two layers
 * an outer layer of the choroid proper,consists of small arteries and veins, with pigment cells interspersed between them;
 * and an inner layer of the choroid proper, consists of a capillary plexus.
 * The outer layer of the choroid proper is lamina vasculosa of the choroid proper.
 * lamina vasculosa of the choroid properconsists, in part, of the larger branches of the short ciliary arteries
 * the larger branches of the short ciliary arteries run forward between the veins, before they bend inward to end in the capillaries, but is formed principally of veins, named the venæ vorticosæ.
 * the venæ vorticosæ converge to four or five equidistant trunks, which pierce the sclera about midway between the sclero-corneal junction and the entrance of the optic nerve.
 * Interspersed between the vessels are dark star-shaped pigment cells, the processes of which, communicating with those of neighboring cells, form a delicate net-work or stroma, which toward the inner surface of the choroid loses its pigmentary character.
 * The inner layer (lamina choriocapillaris) consists of an exceedingly fine capillary plexus, formed by the short ciliary vessels;
 * the net-work is closer and finer in the posterior than in the anterior part of the choroid.
 * About 1.25 cm behind the cornea its meshes become larger, and are continuous with those of the ciliary processes.
 * These two laminæ are connected by a stratum intermedium consisting of fine elastic fibers.
 * On the inner surface of the lamina choriocapillaris is a very thin, structureless, or faintly fibrous membrane, called the lamina basalis;
 * the lamina basalis is closely connected with the stroma of the choroid,
 * choroid separates the lamina basalis from the pigmentary layer of the retina.
 * FIG. 874– The veins of the choroid. (Enlarged.) (See enlarged image)
 * the choroid provides nutrition for the retina,
 * the choroid convey vessels and nerves to the ciliary body and iris.

The Ciliary Body (corpus ciliare)

 * The ciliary body comprises the orbiculus ciliaris,+ the ciliary processes,+ the Ciliaris muscle.
 * Pars plana contains connective tissue with vasculature and very thin muscle layer (OK note)
 * Pars plicata contains ciliary processes and vasculature and muscular tissue.(OK note)
 * The ciliary body is a layer of tissue connecting the iris and the choroid.
 * The cilicary body spans from the orra serrata to the corneal limbus(okubo)
 * The ciliary body is rich in vasculature, smooth muscle and epithelial folding.
 * The orbiculus ciliaris is AKA pars plana.
 * The orbiculus ciliaris is a zone of about 4 mm. in width,
 * The orbiculus ciliaris is directly continuous with the anterior part of the choroid;
 * The orbiculus ciliaris presents numerous ridges arranged in a radial manner (Fig. 875).
 * The ciliary processes (processus ciliares) are formed by the inward folding of  the choroid proper and the lamina basalis,
 * The ciliary processes are received between corresponding foldings of the suspensory ligament of the lens.
 * The ciliary processes are arranged in a circle,
 * The ciliary processes form a sort of frill behind the iris, around the margin of the lens (Fig. 875).
 * The ciliary processes vary from sixty to eighty in number, lie side by side,
 * The ciliary processes may be divided into large and small
 * the large ciliary processes are about 2.5 mm. in length,
 * the small ciliary processes numbers about half of the large ciliary process.
 * the small ciliary processesare situated in spaces between large ciliary process irregularly. * The peripheral edge of The ciliary processes are attached to three or four of the ridges of the orbiculus ciliaris
 * The ciliary processes are continuous with the layers of the choroid.
 * The ciliary processes 's opposite extremities are free and rounded.
 * The ciliary processesand are directed toward the posterior chamber of the eyeball and circumference of the lens.
 * The ciliary processes are continuous with the periphery of the iris, In front.
 * The ciliary processes 's posterior surfaces are connected with the suspensory ligament of the lens.

http://www.bartleby.com/107/Images/large/image875.gif
 * FIG. 875– Interior of anterior half of bulb of eye.

=Other materials from the web= http://www.ejournalofophthalmology.com/ejo/Ejo/EJO10/Picture2.JPG Viewing from inside of the eyeball, after removal of lens and zonal fibers.
 * Varsha V. Prabhu, MS; Parag K. Shah, DNB.
 * The ciliary body extends posteriorly from the root of the iris to the ora serrata.
 * the ora serrata is approximately 7 mm away from the surgical limbus on the temporal side of the globe in adults
 * the ora serrata is approximately 6 mm away from the surgical limbus on the nasal side of the globe in adults.
 * The ciliary body is grossly subdivided into two portions, the pars plicata and the pars plana.
 * The pars plicata exhibits 70 to 80 corrugated, fin-like ridges on its inner surface that are arranged around the circumference of the crystalline lens (Fig. 1).
 * Each individual ridge is referred to as a ciliary process, and
 * The ciliary processes are divided into categories of major and minor processes based on their relative height.
 * Major processes of the ciliary processes predominate, and they extend into the posterior chamber of the eye approximately 1 mm.
 * Minor processes of the ciliary processes are about one third as high.
 * In the scanning electron micrograph shown in Figure 2 these structures and their relationships are clearly discernible.
 * These fibers form a continuous carpet over the inner surface of the pars plana of ciliary body and are then channeled into the valleys between adjacent processes in the pars plicata on their way to the lens capsule.
 * As such, in vivo, the valleys between adjacent ciliary processes are largely filled with zonules leaving only the crest of each process exposed to the posterior chamber (Fig. 3).

OCULIST DOT NET
http://www.oculist.net/downaton502/prof/ebook/duanes/graphics/figures/v7/0010/016af.jpg http://www.oculist.net/downaton502/prof/ebook/duanes/graphics/figures/v7/0130/005f.jpg
 * (LeftPanel)  pars plicata (a) and the pars plana (b), The ora serrata (c), cystoid degeneration (d). The bays (e) and dentate processes (f) of the ora, linear ridges or striae (g)
 * The zonular fibers arise from the pars plana beginning 1.5 mm from the ora serrata. The radial (h) and circular furrows (i) of the peripheral iris are shown.
 * A. Most of the ciliary muscle (CM) lies in the anterior half as a white band.
 * A flat ribbon-like long posterior ciliary nerve (N) and thin artery (A) bifurcate shortly before the ora serrata(OS).
 * B. Transillumination indicates the actual site of the ora serrata and relationships to the choroidal vessels.

Eyeworld dot org
http://www.eyeworld.org/images/New_Articles/2010/12/16.jpg http://www.missionforvisionusa.org/anatomy/uploaded_images/wZonulespan-737375.JPG http://www.eyeworld.org/images/New_Articles/2010/02/40_b.jpg
 * Pars plana is a point of intraviterous injection of needles. (Safe Piercing point for eyeball)
 * Pars plana is free of retina, scarce in zonular fibers, not so much bleed.

Structure.

 * The ciliary processes  are similar to the choroid.
 * the vessels of The ciliary processes  are larger than vessels in the choroid
 * the vessels of The ciliary processes  have chiefly a longitudinal direction.
 * The ciliary processes  's posterior surfaces are covered by a bilaminar layer of black pigment cells,
 * The ciliary processes  's posterior surfaces are covered by the pars ciliaris retinæ.
 * the pars ciliaris retinæ is continued forward from the retina.
 * In the stroma of the ciliary processes there are also stellate pigment cells.
 * stellate pigment cells in the stroma of the ciliary processes are not so numerous as in the choroid itself.
 * the aqueous humor is a secretion formed by the active intervention of the epithelial cells lining the apices of the ciliary processes. (Henderson)


 * The Ciliaris muscle is AKA m. ciliaris;
 * The Ciliaris muscle is AKA Bowman’s muscle
 * The Ciliaris muscleis made up with unstriped fibers.
 * The Ciliaris muscle forms a grayish, semitransparent, circular band, about 3 mm. broad, on the outer surface of the fore-part of the choroid.
 * The Ciliaris muscle is thickest in front,
 * The Ciliaris muscle is made up with meridional fibers and circular fibers.
 * The meridional fibers of ciliarius muscle arise from the posterior margin of the scleral spur.
 * The meridional fibers of ciliarius muscle run backward,
 * The meridional fibers of ciliarius muscle are attached to the ciliary processes and orbiculus ciliaris.
 * One bundle of The meridional fibers of ciliarius muscle is inserted into the sclera, according to Waldeyer.
 * The circular fibers are internal to the meridional ones, and in a meridional section appear as a triangular zone behind the filtration angle and close to the circumference of the iris.
 * They are well-developed in hypermetropic, but are rudimentary or absent in myopic eyes.
 * The Ciliaris muscle is the chief agent in accommodation, i. e., in adjusting the eye to the vision of near objects.
 * When contracts, The Ciliaris muscle draws forward the ciliary processes, relaxes the suspensory ligament of the lens, and thus allows the lens to become more convex.	   28

http://www.bartleby.com/107/Images/large/image876.gif http://www.bartleby.com/107/Images/large/image877.gif FIG. 876– Vessels of the choroid, ciliary processes, and iris of a child. (Arnold.) Magnified 10 times. a. Capillary net-work of the posterior part of the choroid, ending at b, the ora serrata. c. Arteries of the corona ciliaris, supplying the ciliary processes, d, and passing into the iris e. f. The capillary net-work close to the pupillary margin of the iris. (See enlarged image)

FIG. 877– Diagram of the blood vessels of the eye, as seen in a horizontal section. (Leber, after Stöhr.). Course of vasa centralia retinæ: a. Arteria. a. 147 Vena centralis retinæ. B. Anastomosis with vessels of outer coats. C. Anastomosis with branches of short posterior ciliary arteries. D. Anastomosis with chorioideal vessels. Course of vasa ciliar. postic. brev.: I. Arteriæ, and I1. Venæ ciliar. postic. brev. II. Episcleral artery. II1. Episcleral vein. III. Capillaries of lamina choriocapillaris. Course of vasa ciliar. postic. long.: 1. a. ciliar. post. longa. 2. Circulus iridis major cut across. 3. Branches to ciliary body. 4. Branches to iris. Course of vasa ciliar. ant.: a. Arteria. a1. Vena ciliar. ant. b. Junction with the circulus iridis major. c. Junction with lamina choriocapill. d. Arterial, and d1. Venous episcleral branches. e. Arterial, and e1. Venous branches to conjunctiva scleræ. f. Arterial, and f1. Venous branches to corneal border. V. Vena vorticosa. S. Transverse section of sinus venosus scleræ. (See enlarged image)

=The Iris=
 * The iris has received its name from its various colors in different individuals.
 * The iris is a thin, circular, contractile disk
 * The iris is suspended in the aqueous humor between the cornea and lens,
 * The iris perforated a little to the nasal side of its center by the pupil.
 * Periphery The iris is continuous with the ciliary body,
 * The iris is also connected with the posterior elastic lamina of the cornea by means of the pectinate ligament;
 * The iris 's surfaces are flattened,
 * and look forward and backward, the anterior toward the cornea, the posterior toward the ciliary processes and lens.
 * The iris divides the space between the lens and the cornea into an anterior chamber and a posterior chamber.
 * The anterior chamber of the eye is bounded in front by the posterior surface of the cornea; behind by the front of the iris and the central part of the lens.
 * The posterior chamber is a narrow chink behind the peripheral part of the iris,
 * The posterior chamber is a narrow chink in front of the suspensory ligament of the lens and the ciliary processes.
 * In the adult the two chambers communicate through the pupil,
 * In the fetus up to the seventh month, the anterior chamber and the posterior chamber are separated by the membrana pupillaris.	  29

Structure

 * The iris is composed of the following structures:
 * The iris has a layer of flattened "iridial endothelial cells" on the frontal surface.
 * "The iridial endothelial cells" are placed on a delicate "hyaline basement membrane".
 * The layer of "iridial endothelial cells" is continuous with the corneal endothelium.
 * "iridial endothelial cells" contain pigment granules in colored people.
 * "The stroma of iris" consists of fibers and cells.
 * The fibers in iris are made up of delicate bundles of fibrous tissue;
 * a few fibers at the circumference of the iris have a circular direction;
 * The majority of the fibers in iris radiate toward the pupil,
 * The radial fibers of iris form delicate meshes, in which the vessels and nerves are contained.
 * Interspersed between the bundles of connective tissue are numerous branched cells with fine processes.
 * In dark eyes many of interspersing branched cells in iridial fibers contain pigment granules,
 * In blue eyes and the eyes of albinos interspersing branched cells in iridial fibers are unpigmented.
 * The muscular fibers are involuntary, and consist of circular and radiating fibers.
 * The circular fibers form the Sphincter pupillae;
 * Muscle fibers in sphincter pupillae are arranged in a narrow band about 1 mm in width.
 * Muscle fibers in sphincter pupillae surrounds the margin of the pupil toward the posterior surface of the iris;
 * Muscle fibers in sphincter pupillae near the free margin are closely aggregated;
 * Muscle fibers in sphincter pupillae near the periphery of the band are somewhat separated and form incomplete circles.
 * The radiating fibers of iris form the Dilatator pupillae;
 * the Dilatator pupillae converge from the circumference toward the center,
 * the Dilatator pupillae blend with the circular fibers near the margin of the pupil.

http://www.bartleby.com/107/Images/large/image878.gif FIG. 878– Iris, front view. (See enlarged image)
 * The posterior surface of the iris is of a deep purple tint,
 * The posterior surface of the iris is covered by two layers of pigmented columnar epithelium,
 * continuous at the periphery of the iris with the pars ciliaris retinae.
 * The pigmented epithelium is named the pars iridica retinae,
 * the pars iridica retinae is AKA the uvea from the resemblance of its color to that of a ripe grape. (this is classic, OK).
 * Uvea is a collective name for the vascular tunic of the eye (Gray 40th p679)
 * Uvea is made up with the choroid, ciliary body, and iris.(Gray 40th p679)
 * The color of the iris is produced by the reflection of light from dark pigment cells underlying a translucent tissue, and is therefore determined by the amount of the pigment and its distribution throughout the texture of the iris.
 * The number and the situation of the pigment cells differ in different irides.
 * In the albino pigment is absent; in the various shades of blue eyes the pigment cells are confined to the posterior surface of the iris, whereas in gray, brown, and black eyes pigment is found also in the cells of the stroma and in those of the endothelium on the front of the iris.
 * The iris may be absent, either in part or altogether as a congenital condition, and in some instances the pupillary membrane may remain persistent, though it is rarely complete. Again, the iris may be the seat of a malformation, termed coloboma, which consists in a deficiency or cleft, clearly due in a great number of cases to an arrest in development. In these cases the cleft is found at the lower aspect, extending directly downward from the pupil, and the gap frequently extends through the choroid to the porus opticus. In some rarer cases the gap is found in other parts of the iris, and is not then associated with any deficiency of the choroid.	  36

Vessels and Nerves.

 * The arteries of the iris are derived from the long iliary arteries and anterior ciliary arteries, and from the vessèls of the ciliary processes (see p. 571).
 * Each of the two long ciliary arteries, having reached the attached margin of the iris, divides into an upper and lower branch;
 * these anastomose with corresponding branches from the opposite side and thus encircle the iris; into this vascular circle (circulus arteriosus major) the anterior ciliary arteries pour their blood, and from it vessels converge to the free margin of the iris, and there communicate and form a second circle (circulus arteriosus minor) (Figs. 877 and 878).	  37
 * The nerves of the choroid and iris are the long ciliary nerve and short ciliary nerve; * the long ciliary nerve is branches of the nasociliary nerve,
 * the short ciliary nerve is branch of the ciliary ganglion.
 * ciliary nerves pierce the sclera around the entrance of the optic nerve,
 * ciliary nerves run forward in the perichoroidal space, and supply the bloodvessels of the choroid.
 * After reaching the iris, the ciliary nerves form a plexus around its attached margin; from this are derived non-medullated fibers which end in the Sphincter and Dilatator pupillæ their exact mode of termination has not been ascertained.
 * Other fibers from the plexus end in a net-work on the anterior surface of the iris. The fibers derived through the motor root of the ciliary ganglion from the oculomotor nerve, supply the Sphincter, while those derived from the sympathetic supply the Dilatator.	  38

Membrana Pupillaris

 * In the fetus, the pupil is closed by a delicate the membrana pupillaris
 * the membrana pupillaris is a vascular membrane.
 * the membrana pupillaris divides the space in which the iris is suspended into two distinct chambers.
 * The vessels of the membrana pupillaris are partly derived from those of the margin of the iris and partly from those of the capsule of the lens
 * The vessels of the membrana pupillaris have a looped arrangement,
 * The vessels of the membrana pupillaris converge toward each other without anastomosing.
 * About the sixth month the membrana pupillaris begins to disappear by absorption from the center toward the circumference,
 * at birth only a few fragments of the membrana pupillaris are present
 * in exceptional cases the membrana pupillaris persists.

http://www.bartleby.com/107/Images/large/image879.gif FIG. 879– Interior of posterior half of bulb of left eye. The veins are darker in appearance than the arteries. (See enlarged image)

= The Retina (tunica interna)=
 * The retina is a delicate nervous membrane,
 * upon The retina the images of external objects are received.
 * The retina 's outer surface is in contact with the choroid;
 * The retina 's inner surface is in contact with the hyaloid membrane of the vitreous body.
 * Behind, The retina is continuous with the optic nerve;
 * The retina gradually diminishes in thickness from behind forward, and extends nearly as far as the ciliary body.
 * near ciliary body The retina appears to end in a jagged margin, the ora serrata.
 * At the ora serrata the nervous tissues of the retina end,
 * a thin prolongation of the membrane extends forward over the back of the ciliary processes and iris, forming the pars ciliaris retinæ and pars iridica retinæ.
 * the pars ciliaris retinæ and pars iridica retinæ consists of the pigmentary layer of the retina together with a stratum of columnar epithelium.
 * The retina is soft, semitransparent, and of a purple tint in the fresh state, owing to the presence of a coloring material named rhodopsin or visual purple;
 * The retina soon after resection becomes clouded, opaque, and bleached when exposed to sunlight.
 * an oval yellowish area, Exactly in the center of the posterior part of the retina, isthe macula lutea.
 * In the macula retina, the sense of vision is optically the most perfect.
 * the fovea centralis is a central derpresion in the macula retina.
 * At the fovea centralis the retina is exceedingly thin,
 * At the fovea centralis the dark color of the choroid is distinctly seen through it.
 * About 3 mm. to the nasal side of the macula lutæ is the optic disk.
 * The optic disK is the entrance of the optic nerve on the retina.
 * the circumference of The optic disK is slightly raised to form the colliculus nervi optici.
 * the colliculus nervi optici is an eminence around the optic disk.
 * the arteria centralis retinæ pierces the center of the optic disk.
 * the optic disk is the only part of the surface of the retina which is insensitive to light,
 * the optic disk is termed the blind spot.

http://www.bartleby.com/107/Images/large/image880.gif
 * FIG. 880– The terminal portion of the optic nerve and its entrance into the eyeball, in horizontal section. (Toldt.) (See enlarged image)

Structure

 * The retina consists of an outer pigmented layer and an inner nervous stratum or retina proper.
 * The pigmented layer of the retina consists of a single stratum of cells.
 * the cells in the pigment layer of the retine are smooth and hexagonal in shape, When viewed from the outer surface.
 * when seen in section each cell consists of an outer non-pigmented part containing a large oval nucleus and an inner pigmented portion which extends as a series of straight thread-like processes between the rods, this being especially the case when the eye is exposed to light.
 * In the eyes of albinos the cells of this layer are destitute of pigment.

Retina Proper

 * The nervous structures of the retina proper consist of seven layers, named from within outward as follows:1. Stratum opticum.2. Ganglionic layer.3. Inner plexiform layer. 4. Inner nuclear layer, or layer of inner granules.5. Outer plexiform layer. 6. Outer nuclear layer, or layer of outer granules. 7. Layer of rods and cones.
 * The stratum opticum is formed by the expansion of the fibers of the optic nerve;
 * The stratum opticum is thickest near the porus opticus, gradually diminishing toward the ora serrata.
 * As the nerve fibers pass through the lamina cribrosa scleræ they lose their medullary sheaths
 * the optic nerve fibers are continued onward through the choroid and retina as simple axis-cylinders.
 * In The stratum opticum of the retina, nerve fibers radiate in bundles, and in many places arranged in plexuses.
 * Most of the fibers are centripetal, and are the direct continuations of the axis-cylinder processes of the cells of the ganglionic layer, but a few of them are centrifugal and ramify in the inner plexiform and inner nuclear layers, where they end in enlarged extremities.
 *  The ganglionic layer consists of a single layer of large ganglion cells, except in the macula lutea, where there are several strata.
 * The cells are somewhat flask-shaped; the rounded internal surface of each resting on the stratum opticum, and sending off an axon which is prolonged into it.
 * From the opposite end numerous dendrites extend into the inner plexiform layer, where they branch and form flattened arborizations at different levels.
 * The ganglion cells vary much in size, and the dendrites of the smaller ones as a rule arborize in the inner plexiform layer as soon as they enter it; while those of the larger cells ramify close to the inner nuclear layer.	  45

http://www.bartleby.com/107/Images/large/image881.gif
 * FIG. 881– Section of retina. (Magnified.)


 * The inner plexiform layer is made up of a dense reticulum of minute fibrils formed by the interlacement of the dendrites of the ganglion cells with those of the cells of the inner nuclear layer; within this reticulum a few branched spongioblasts are sometimes imbedded.	  46

http://www.bartleby.com/107/Images/large/image882.gif
 * FIG. 882– Plan of retinal neurons. (After Cajal.) (See enlarged image)
 * The inner nuclear layer is made up of a number of closely packed cells, of which there are three varieties, viz.: bipolar cells, horizontal cells, and amacrine cells.	  47
 * The bipolar cells of retina, by far the most numerous cells in nuclear layer of the reticna.
 * The bipolar cells of retina are round or oval in shape, and each is prolonged into an inner and an outer process.
 * The bipolar cells of retinaare divisible into rod bipolars and cone bipolars.
 * The inner processes of the rod bipolars run through the inner plexiform layer and arborize around the bodies of the cells of the ganglionic layer; their outer processes end in the outer plexiform layer in tufts of fibrils around the button-like ends of the inner processes of the rod granules.
 * The inner processes of the cone bipolars ramify in the inner plexiform layer in contact with the dendrites of the ganglionic cells.


 *  The horizontal cells in the granular layer of the retina lie in the outer part of the inner nuclear layer and possess somewhat flattened cell bodies.
 *  The horizontal cells in the granular layer of the retina 's dendrites divide into numerous branches in the outer plexiform layer, while their axons run horizontally for some distance and finally ramify in the same layer.	  49
 * The amacrine cells are placed in the inner part of the inner nuclear layer, and are so named because they have not yet been shown to possess axis-cylinder processes.
 * The amacrine cells 's dendrites undergo extensive ramification in the inner plexiform layer.
 * The outer plexiform layer is much thinner than the inner; but, like it, consists of a dense net-work of minute fibrils derived from the processes of the horizontal cells of the preceding layer, and the outer processes of the rod and cone bipolar granules, which ramify in it, forming arborizations around the enlarged ends of the rod fibers and with the branched foot plates of the cone fibers.
 * The outer nuclear layer contains several strata of oval nuclear bodies;
 * CElls in the outer nuclear layer are of two kinds, viz.: rod and cone granules, so named on account of their being respectively connected with the rods and cones of the next layer.
 * The rod granules are much the more numerous, and are placed at different levels throughout the layer.
 * Their nuclei present a peculiar cross-striped appearance, and prolonged from either extremity of each cell is a fine process; the outer process is continuous with a single rod of the layer of rods and cones; the inner ends in the outer plexiform layer in an enlarged extremity, and is imbedded in the tuft into which the outer processes of the rod bipolar cells break up. In its course it presents numerous varicosities. The cone granules, fewer in number than the rod granules, are placed close to the membrana limitans externa, through which they are continuous with the cones of the layer of rods and cones. They do not present any cross-striation, but contain a pyriform nucleus, which almost completely fills the cell. From the inner extremity of the granule a thick process passes into the outer plexiform layer, and there expands into a pyramidal enlargement or foot plate, from which are given off numerous fine fibrils, that come in contact with the outer processes of the cone bipolars.	  52
 * The Layer of Rods and Cones is AKA Jacob’s membrane.
 * —The elements composing The Layer of Rods and Cones are of two kinds, rods and cones,
 * the rod cells exceeds the cone cells except in the macula lutea.
 * The rods are cylindrical, of nearly uniform thickness, and are arranged perpendicularly to the surface.
 * Each rod consists of two segments, an outer and inner, of about equal lengths.
 * The segments differ from each other as regards refraction and in their behavior toward coloring reagents;
 * the inner segment is stained by carmine, iodine, etc.; the outer segment is not stained by these reagents, but is colored yellowish brown by osmic acid.
 * The outer segment is marked by transverse striæ, and tends to break up into a number of thin disks superimposed on one another;
 * it also exhibits faint longitudinal markings. The deeper part of the inner segment is indistinctly granular; its more superficial part presents a longitudinal striation, being composed of fine, bright, highly refracting fibrils. The visual purple or rhodopsin is found only in the outer segments.
 * The cones are conical or flask-shaped, their broad ends resting upon the membrana limitans externa, the narrow-pointed extremity being turned to the choroid.
 * Like the rods, each is made up of two segments, outer and inner; the outer segment is a short conical process, which, like the outer segment of the rod, exhibits transverse striæ.
 * The inner segment resembles the inner segment of the rods in structure, presenting a superficial striated and deep granular part, but differs from it in size and shape, being bulged out laterally and flask-shaped.
 * The chemical and optical characters of the two portions are identical with those of the rods.

Supporting Frame-work of the Retina

 * The nervous layers of the retina are connected together by a supporting frame-work, formed by the sustentacular fibers of Müller;
 * these fibers pass through all the nervous layers, except that of the rods and cones.
 * Each begins on the inner surface of the retina by an expanded, often forked base, which sometimes contains a spheroidal body staining deeply with hematoxylin, the edges of the bases of adjoining fibers being united to form the membrana limitans interna.
 * As the fibers pass through the nerve fiber and ganglionic layers they give off a few lateral branches; in the inner nuclear layer they give off numerous lateral processes for the support of the bipolar cells, while in the outer nuclear layer they form a network around the rod- and cone-fibrils, and unite to form the membrana limitans externa at the bases of the rods and cones.
 * At the level of the inner nuclear layer each sustentacular fiber contains a clear oval nucleus.

Macula Lutea and Fovea Centralis

 * In the macula lutea the nerve fibers are wanting as a continuous layer, the ganglionic layer consists of several strata of cells, there are no rods, but only cones, which are longer and narrower than in other parts, and in the outer nuclear layer there are only cone-granules, the processes of which are very long and arranged in curved lines.
 * In the fovea centralis the only parts present are (1) the cones; (2) the outer nuclear layer, the cone-fibers of which are almost horizontal in direction; (3) an exceedingly thin inner plexiform layer.
 * The pigmented layer is thicker and its pigment more pronounced than elsewhere.
 * The color of the macula seems to imbue all the layers except that of the rods and cones; it is of a rich yellow, deepest toward the center of the macula, and does not appear to be due to pigment cells, but simply to a staining of the constituent parts.	  56
 * At the ora serrata the nervous layers of the retina end abruptly, and the retina is continued onward as a single layer of columnar cells covered by the pigmented layer.
 * This double layer is known as the pars ciliaris retinæ,
 * the pars ciliaris retinæ can be traced forward from the ciliary processes on to the back of the iris, where it is termed the pars iridica retinæ or uvea.	  57
 * The arteria centralis retinae  and its accompanying vein pierce the optic nerve, and enter the bulb of the eye through the porus opticus.
 * The arteria centralis retinae  immediately bifurcates into an upper and a lower branch,
 * each of these again divides into a medial or nasal and a lateral or temporal branch, which at first run between the hyaloid membrane and the nervous layer; but they soon enter the latter, and pass forward, dividing dichotomously.
 * From these branches a minute capillary plexus is given off, which does not extend beyond the inner nuclear layer.
 * The macula receives two small branches from the temporal branches and small twigs directly from the central artery;
 * The branches of temporal branch of the arteria centralis retinae feeding the macula are the superior macular artery and inferior macular artery.
 * The feeding arteries of macula do not reach as far as the fovea centralis,
 * the fovea centralis has no bloodvessels.
 * The branches of the arteria centralis retinae do not anastomose with each other—in other words they are terminal arteries.
 * In the fetus, a small vessel, the arteria hyaloidea, passes forward as a continuation of the arteria centralis retinae through the vitreous humor to the posterior surface of the capsule of the lens.