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 s ...

(the white of the eye). It contains

stem cells In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of ...

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 bl ...

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

and the

. 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 i ...

is continuous with the epithelium covering the cornea. The corneal limbus contains radially-oriented fibrovascular ridges known as the palisades of Vogt that contain

. 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 Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

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 fluid within the eye re ...

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 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 the power ...

meaning "border".

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 {{Authority control Human eye anatomy Ophthalmology drugs