Iris Pigmentation Research Info


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Optics 1

The Eye 1 Anatomy of the Eye - Outline

The Eye 2 Anatomy of the Eye - Cross-Section, Light Microscopy, Anterior Chamber
The Eye 3 Anatomy of the Eye - Anterior Chamber
The Eye 4 Anatomy of the Eye - Fovea

Terms 1
Terms 2 Analogous Terms
Terms 3 Components of the Iris
Terms 4 Components of the Iris

The Iris 6
Sample Iris Image Pair
The Iris 7 Iris Blood Supply
The Iris 8 Iris Section (LM)
The Iris 9 Iris Cross-Section (LM)
The Iris 10 Fluorescein Iris Angiogram - late phase

From Histology of the Eye, by Hogan, Alvarez, Weddell

Iris Histology 11
Figure I-11.
Pupillary margin (LM)

Iris Histology 12
Figure I-12.
Pupillary margin of the iris to show the two pigment epithelial layers (a) and their continuity with the anterior border layer of the iris (b). The sphincter muscle of the iris (c) is slightly curved near the pupillary margin and is continuous with the anterior border layer by a thin layer of connective tissue. A clump cell measuring 90 microns (d) is seen near the sphincter muscle. (X 680.)

Iris Histology 13 Figure I-13 A pigmented iris showing the anterior border layer (a) and an iris freckle (b). In the area of the freckle the anterior border layer becomes more cellular. The iris stroma (c) beneath the freckle also is more cellular. (X 400.)

Iris Histology 15 Cross-sectional diagram of iris melanocytes and fibroblasts

Iris Histology 17
Figure I-17
Iris stromal fibroblast.
The Golgi apparatus is seen at (a) and a cilium (b) arises from the basal body (c) in the cytoplasm. The filaments from the basal body can be traced into the cilium (d). (X 32,000.)

Iris Histology 18
Figure I-18
Iris stromal melanocytes.
The melanin granules are enclosed by a membrane and are filled with melanoprotein. One cell has a well developed Golgi apparatus which surrounds a centriole (a). Part of a cilium is seen at (b). The cytoplasm is filamentous and contains rough-surfaced endoplasmic reticulum (c) and free ribosomes (d). (33,000.)

Iris Histology 19
Figure I-19
Iris stromal mast cell.
In the limbus this type of mast cell is more abundant than the one shown in Figure 6-16. This mast cell is distinguished by the fact that many of its granules contain cylindrical structures which are seen in longitudinal section (a) or in cross-section (b). A finely granular material is also contained (c) within the granules. (X 27,000.)

Iris Histology 20
Figure I-20
B, Higher magnification to show the cylindrical structures within the membrane of the mast cell granules. They are uniformly dense and of equal length. (X 60,000.) C, View of the cross-sections of the cylindrical structures. Each cylinder is formed by a single lamellar membrane which is wound into a scroll. The core of the cylinder contains an electron-dense material. (X90,000.) D, Cylinders in mast cell granules seen in cross-section. The core material (a) and a mass of granular material (b) are found within the granules. (X 99,000.)

Iris Histology 21
Figure I-21
Diagrammatic cross section of iris stroma tissue

Iris Histology 22
Figure I-22
Light micrograph of some small iris vessels measure between 7 and 10 microns in diameter. Two appear to be capillaries (a) and one a venule (b). The lighter inner zone adjacent to the endothelium is less apparent in these small vessels. (X 640.)

Iris Histology 23
Figure I-23
Low-power electron micrograph of the two layers of iris epithelium. The anterior epithelium and dilator muscle are shown at (a) and the posterior epithelium at (b). The epithelial portion of the anterior epithelium is at (c) and the muscular component at (d). Note the paucity of melanin granules in the anterior epithelium and their distribution in the apical portion near the nucleus. The posterior iris surface shows two deep furrows (e) and the basal epithelium shows extensive infolding (f). (X2500.)

Iris Histology 24
Figure I-24
Posterior iris epithelium (a) and dilator muscle (b) in the pupillary region.
A spur of dilator muscle tissue (c) extends into the stroma toward the sphincter (X 640).

Iris Histology 25
Figure I-25
Area shown in detail in Figure 25

Iris Histology 26
Figure I-26
Anterior Iris Epithelium
Anterior iris epithelium. The apical or epithelial portion of three cells with their nuclei (a), melanin granules, cell organelles and some clusters of myofilaments (b) are shown. These cells are in close contact with the posterior epithelium (c) by means of numerous desmosomes and tight junctions. Intercellular spaces containing villous processes are shown (d). The basal portion of the anterior epithelium sends tongue-like projections into the iris stroma. These cellular projections are filled with myofilaments (e) and form the dilator muscle. A basement membrane (f) surrounds the muscular portion of these cells (X 8840).

Iris Histology 35
Figure I-35
Posterior Iris Epithelium
Posterior pigmented iris epithelium. The large melanin granules of the iris pigmented epithelium are round in cross-section, measuring 0.6 um and of spindle shape in longitudinal section, measuring 1.96 um in length. Note that these granules are membrane-bound (a) and that there is a narrow zone at the periphery of the granule (arrows) free of melanin. An incompletely melanized granule (b) is seen on the right (X 62,5000).

Iris Histology 36
Figure I-36
Iris posterior epithelium.
A, Iris posterior epithelium. The basal surface of the posterior epithelium faces the posterior chamber and the lens. A thin basement membrane is found on this surface (X 45,000).

Iris Histology 37
Figure I-37
Posterior Pigment Epithelium
Posterior epithelial layers. The anterior iris epithelium has two morphologically distinct portions: an apical epithelial portion (a) and a basal muscular portion (b). The cytoplasm of the basal portion is filled with myofibrils and a moderate number of mitochondria. The tongue-like muscular processes overlap each other, creating three to five layers.

Iris Angiography 5

Iris Angiography 6
Iris Angiography 7
Iris Angiography 8
Iris Angiography 9 Shows late-phase smokestacking.

Iris Pigment Granules 1

Iris Pigment Granules 2
Iris Pigment Granules 3
Iris Pigment Granules 4

From Iris pigmentation and pigmented lesions: an ultrastructural study, by Eagle RC Jr. Trans Am Ophthalmol Soc. 1988;86:581-687. Available from PubMed, see PMID: 2979031:

Iris Ultrastructure Table 1
Cellularity of the Anterior Border Layer
Iris Ultrastructure Table 2 Pigment Granule Diameter
Iris Ultrastructure Table 3 Melanin Granule Prevalence by Iris Color
Iris Ultrastructure Table 4 Melanin Granule Diameter in Freckles
Iris Ultrastructure Table 5 Morphological Terms

Iris Ultrastructure Pic 1
Figure 1.
Two Layers of the Iris
Cross section, brown iris. Contraction furrow (center) grooves loosely textured, collagen-rich iris stroma. Density of stromal cells is markedly increased in avascular anterior border layer zone. Scattered cells and thick-walled vessels, examined under high power in Fig. 3, are seen in deeper layers of stroma. Circumferential folds scallop posterior surface of iris pigment epithelium, which contains myriad round pigment granules. The dilatator muscle forms a thin band at stromal-epithelial junction (SEM, X 160).

Iris Ultrastructure Pic 2
Figure 2
Anterior Border Layer of the Blue Iris
Anterior border layer, blue iris. Branching, flattened processes of discontinuous anterior fiberblastic layer partially obscures delicate processes of underlying stromal melanocytes. Microvilli are seen on surface of fibroblasts (SEM, X 160).

Iris Ultrastructure Pic 3
Figure 3
Iris Stromal Vessel Cross Section
"Thick-walled" iris stromal vessels. Thick mantle of collagen fibers ensheath vessels in mid-stroma. An irregular, delicate matrix of fibers permeates intervening stroma. (SEM X 640)

Iris Ultrastructure Pic 4
Figure 4
Macrophoto of Light Blue Iris
Segment of light blue iris examined by SEM in Fig. 5. Sinuously radiating fibers are most striking clinical feature of blue iris. No crypts are apparent in marginal cribriform zone. (Macrophoto, X 19)

Iris Ultrastructure Pic 5
Figure 5
SEM of Light Blue Iris
Scanning electron micrograph of light blue iris seen in Fig. 4. Preparation of specimen for SEM has opacified the clinically transparent, nonpigmented anterior border layer and stroma of the blue iris, obscuring the radially oriented, collagen-ensheathed midstromal vessels. Pupillary and marginal crypts in the iris stroma are accentuated by SEM. At this magnification, blue and brown irides are indistinguishable by scanning microscopy (SEM, X 20)

Iris Ultrastructure Pic 7
Figure 7
Nevus of Ota
Nevus of Ota: Thickness of anterior border layer of normal light-brown right iris (A) and eye with Ota's nevus (B) are compared at same magnification. Heavily pigmented anterior border layer is at least twice as thick in the involved left eye (1 micron Epon sections, X 250).

Iris Ultrastructure Pic 8
Figure 8
Nevus of Ota
Nevus of Ota: Relatively smooth anterior surface and delicate processes of normal-light brown right iris (A) contrast sharply with roughened texture and thickened, pigment-engorged processes of left iris with diffuse nevus (B). Numerous framboisiform cellular processes stud the anterior border layer of the involved left iris (stereo SEM, original magnification, X 640).

Iris Ultrastructure Pic 9
Figure 9
Nevus of Ota
Nevus of Ota: Another specimen from an eye enucleated for a posterior uveal malignant melanoma. Stout cellular processes laden with pigment granules are partially hidden by smooth surface fibroblastic layer, which is prominent in this region. Spheroidal cellular processes project from iris surface. Melanin granules are large and fairly uniform in diameter (stereo SEM, X 640).

Iris Ultrastructure Pic 10
Figure 10
Nevus of Ota
Nevus of Ota: Pigment granules in melanocytes of normal light-brown right iris (A) are smaller than those in left eye with Ota's nevus (B). The cellular processes also are more delicate in the lighter eyes (TEM, original magnification, X 8000).

Iris Ultrastructure Pic 11
Figure 11
Blue Stroma with Freckle
Specimen EE: Blue stroma, medium-brown and light yellow-brown freckle. Radially-oriented, collagen-clad vessels are strikingly evident. A light dusting of pigment occurs focally. The freckles are examined by light microscopy and TEM in Figs 76 to 81. The iris pigment epithelium in this specimen was damaged during dissection.

Iris Ultrastructure Pic 12
Tan Stroma with Freckles.
In relaxed state with 6 circumferential contraction furrows. (LM)

Iris Ultrastructure Pic 18
Figure 18.
Anterior Border Layer of Blue Iris.
Anterior border layer, blue iris (specimen EE). A few small pigment granules are seen in some of the superficial cells. Thirty-eight nuclei are present in this photomicrograph (1 micron Epon section, X 250).

Iris Ultrastructure Pic 30
Figure 30
Light Tan Iris Stroma
Light-tan stroma (specimen P). Melanosomes are generally round. A few fused granules are evident (TEM, X 12,000).

Iris Ultrastructure Pic 31 Tan Iris Stroma (TEM)

Iris Ultrastructure Pic 32 Tan Iris Stroma (TEM)

Iris Ultrastructure Pic 33 Medium Brown Iris Stroma (TEM)

Iris Ultrastructure Pic 34 Dark Brown Iris Stroma (TEM)

Iris Ultrastructure Pic 35 Dark Brown Iris Stroma (TEM)

Iris Ultrastructure Pic 36 Dark Brown Iris Stroma (TEM)

Iris Ultrastructure Pic 37 Anterior Iris (SEM X20 - stereo)

Iris Ultrastructure Pic 38 Stellate Collarette SEM X 10

Iris Ultrastructure Pic 39 Anterior Iris Collarette SEM X 12.5

Iris Ultrastructure Pic 40
Figure 40
Pupillary Margin
Pupillary margin, anterior iris. Beaded pupillary ruff of iris pigment epithelium surrounds pupil. Crenations ("mamelons" of Gallemaerts and Kleefeld) in pigment epithelium are the result of pupillary miosis. Radial grooves cross spongy pupillary stroma. Surface of anterior lens capsule is smooth (SEM, X 320)

Iris Ultrastructure Pic 41
Figure 41
Pupillary Margin, Premature Infant
Anterior iris, premature infant. The collarette closely approximates the pupillary border, the stroma is markedly cellular (SEM, X 160).

Iris Ultrastructure Pic 42
Figure 42
Pupillary Zone
Pupillary zone, anterior iris. Numerous diamond-shaped spaces in the relatively paucicellular stroma are enclosed by intersecting strands of tissue. This pattern, a response to pupillary mechanics, reflects organization of the stroma's connective tissue skeleton. A curious band of large globoid stromal cells borders the pigment epithelium (SEM, X 160)

Iris Ultrastructure Pic 43
Figure 43
Anterior Surface
The collarette is indistinct superiorly. Below, it is marked by crypts and trabeculae. The inner part of ciliary zone between the collarette and contraction furrows is relatively smooth, and its stroma is densely matted. In contrast, the surface of the attenuated pupillary stroma exhibits myriad interweaving strands and minute crypts. The interrupted, discontinuous nature of the contraction furrows is evident at right (SEM, X 80).

Iris Ultrastructure Pic 44
Figure 44
Crypt of Fuchs
Crypt of Fuchs: The cell-rich superficial layer of iris stroma is focally absent. In contrast to the smooth and matted appearance of encircling anterior border layer, exposed deep stroma in crypt's floor is loosely textured, and relatively paucicellular with myriad interweaving strands and minute crypts. Trabeculae forming part of collarette are seen at right (SEM, X 160).

From Differentiation of Iris Markings, by Deck J:

Iris Reflex Theory 1 Metamery

Iris Reflex Theory 2 Flower

Iris Reflex Theory 3 Color spot

Iris Reflex Theory 4 Rufin

Iris Reflex Theory 5 Stomach Zone

Iris Reflex Theory 6 Ulcers

Iris Reflex Theory 7 Stomach Ulcers

Iris Reflex Theory 8 Dialectic Ring

Iris Reflex Theory 9 Cotyledon

Iris Reflex Mapping 1