Definitions
The iris in vertebrates (and even chordates at large) is an apposition of two classes of biological tissue material, of distinct embryological origins:
- the epithelia, posteriorly (towards the posterior pole of the eyeball)
- the stroma, anteriorly (towards the anterior pole of the eyeball)
Origins
The epithelia are two in number and derive from the apposed, never completely fused, anterior neuroectodermic rims of the optic cup .
The stroma is unique and derives from the condensed, never completely rigid anterior (cephalic or cranial ) mesenchyme which is the connective tissue of embryonic fame.
Unique Features
The iris stroma displays an intracate, complex, indeed fascinating pattern of coiled, but resilient collagen fibers, pigment clusters, crypts, iris ridge relief, colors and transparencies, never the same, not in identical twins, not in the same individual, and not even in the same eye in time.
The iris stroma is the only living tissue, always visible with open eyelids through the transparent cornea - that portion of the external tunic of the eyeball specialized for near-perfect transparency around the anterior pole . The iris stroma in itself is specialized for less-then-perfect opacity, because of complex, not only visual functionality.
"Some Lucrative Opportunities"
No doubt that such unique anterior pole biological prowess has stimulated either cranks, serious researchers, or, sometimes, even both. Indeed, from iridologists to trans-iridial studies specialists, a bandwagon of researchers keeps adding noise to the anatomical signal, maintaining that they can read health, mind, palms, future, hands and anything else for that matter.
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