The corneal limbus (''Latin'': corneal border) is the border between the
cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical ...
and the
sclera
The sclera, also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective, outer layer of the human eye containing mainly collagen and some crucial elastic fiber. In humans, and so ...
(the white of the eye). It contains
stem cells in its palisades of Vogt. It may be affected by
cancer
Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
or by
aniridia
Aniridia is the absence of the iris, a muscular structure that opens and closes the pupil to allow light into the eye. It is also responsible for eye color. Without it, the central eye appears all black. It can be congenital, in which both ey ...
(a developmental problem), among other issues.
Structure
The corneal limbus is the border between the
cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical ...
and the
sclera
The sclera, also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective, outer layer of the human eye containing mainly collagen and some crucial elastic fiber. In humans, and so ...
.
It is highly vascularised.
Its
stratified squamous epithelium
A stratified squamous epithelium consists of squamous (flattened) epithelial cells arranged in layers upon a basal membrane. Only one layer is in contact with the basement membrane; the other layers adhere to one another to maintain structural ...
is continuous with the
epithelium
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...
covering the cornea.
The corneal limbus contains radially-oriented fibrovascular ridges known as the palisades of Vogt that contain
stem cells.
The palisades of Vogt are more common in the superior and inferior quadrants around the eye.
Clinical significance
Cancer
The corneal limbus is a common site for the occurrence of
corneal epithelial neoplasm
A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
.
Aniridia
Aniridia
Aniridia is the absence of the iris, a muscular structure that opens and closes the pupil to allow light into the eye. It is also responsible for eye color. Without it, the central eye appears all black. It can be congenital, in which both ey ...
, a developmental anomaly of the
iris, disrupts the normal barrier of the cornea to the conjunctival epithelial cells at the limbus.
Glaucoma
The corneal limbus may be cut to allow for
aqueous humour
The aqueous humour is a transparent water-like fluid similar to plasma, but containing low protein concentrations. It is secreted from the ciliary body, a structure supporting the lens of the eyeball. It fills both the anterior and the posteri ...
to drain from the
anterior chamber of the
eye into the subconjunctival space.
This can be used in
glaucoma
Glaucoma is a group of eye diseases that result in damage to the optic nerve (or retina) and cause vision loss. The most common type is open-angle (wide angle, chronic simple) glaucoma, in which the drainage angle for aqueous humor, fluid withi ...
treatment.
The hole created only needs to be small, although slightly bigger than needed to account for gradual healing.
This procedure sometimes fails, particularly if the hole is large.
It can lead to
eye irritation
The human eye is a sensory organ, part of the sensory nervous system, that reacts to visible light and allows humans to use visual information for various purposes including seeing things, keeping balance, and maintaining circadian rhythm.
T ...
from blebbing.
Trabeculectomy, a surgery used to treat glaucoma, is best performed with an
incision
Incision may refer to:
* Cutting, the separation of an object, into two or more portions, through the application of an acutely directed force
* A type of open wound caused by a clean, sharp-edged object such as a knife, razor, or glass splinter
* ...
through the superior part of the corneal limbus.
Mattress suturing may be used to close this incision.
History
The word "limbus" comes from the
Latin
Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
meaning "border".
See also
*
Limbus sign
*
Limbal ring
*
Limbal stem cell
Limbal stem cells, also known as corneal epithelial stem cells, are stem cells located in the basal epithelial layer of the corneal limbus. They form the border between the cornea and the sclera. Characteristics of limbal stem cells include a sl ...
References
External links
* - "Sagittal Section Through the Eyeball"
* https://web.archive.org/web/20060510060508/http://www.vetmed.ucdavis.edu/courses/vet_eyes/images/s_4021_2.jpg
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Human eye anatomy
Ophthalmology drugs