Eye Development | Main Anatomy Index | Ear
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Last updated 30 March 2006
This page was contributed by David
Layers of the eye
- The wall of the eye consists of 3 layers:
The uvea: a middle vascular layer including the choroid, the ciliary body and iris
The inner retina, including the outer
pigment epithelium, the inner neural retina,
and the epithelium of the ciliary body and iris.
- An outer, fibrous corneoscleral coat, including the sclera and the cornea
- The internal cavity of the eye is filled with the vitreous body,
a transparent gel that supports the shape of the eye.
The corneoscleral coat
- The cornea covers the anterior
one sixth of the eye, and is continuous with the fibrous sclera posteriorly.
- It consists of 5 layers:
, upon which the corneal epithelium sits
The corneal stroma (substantia propria) forming most of
the thickness of the cornea
Descemets membrane, the basil lamina of the corneal endothelium
The inner layer of cuboidal cells called the corneal endothelium
- The outer layer of stratified squamous, non keratinizing corneal
- Bowmans membrane
- The sclera consists of dense, irregular connective
tissue, making it opaque.
- Bowmans membrane ends at the junction of the cornea and the sclera, called the limbus, which contains the canal of
Schlemm that drains aqueous humour from the eye into veins of the sclera,
preventing the build up of intraocular pressure.
- This consists mainly of the choroid, which has a dark
brown colour due to many venous plexuses and capillaries, as well as melanin pigment,
which helps to reduce glare within the eye.
- Just posterior to the corneoscleral junction, the ciliary body
extends inwards to form a ring-like thickening, with ciliary processes on its anterior
third, from which the suspensory ligament of the lens (zonular
- The ciliary body continues posteriorly until it merges with the retina at the ora serrata.
- The layers of the ciliary body include a stroma and an epithelium, with the stroma
divided into 2 layers:
- The outer ciliary muscle, which alters the shape of the
lens in accommodation.
- An inner vascular region extending into the ciliary process
- The epithlium of the ciliary body is double
layered, derived from the layers of the optic cup (the retinal epithelium), and
thus the deeper layer is pigmented (like the retinal
- The superficial, non-pigmented epithelial layer
secretes aqueous humour, which passes into the anterior
chamber of the eye before draining laterally to the angle formed between the cornea and
iris, finding its way to the canal of Schlemm.
- The iris extends over the anterior surface of the lens
from the anterior border of the ciliary body, and consists of 5 layers, from anterior to
- A discontinuous layer of fibroblasts and melanocytes
- The avascular anterior stromal sheet (lamella)
- A vascular layer of loose connective tissue forming the bulk of the iris
- The posterior membrane, containing the circular sphincter pupillae and radial dilator
- A double layer of pigmented
- The inner, neural retina, containing photoreceptor
cells, with a 10 layered structure.
- The outer retinal pigment epithelium (RPE) that sits on
the choroid, consisting of cuboidal melanin-containing cells.
the retina, from the outside inwards
Retinal Pigment Epithelium
Layer of rods and cones
- Inner and outer segments of photoreceptor cells
External (Outer) limiting
- Apical boundary of Müllers cells
Outer nuclear layer
- Cell bodies of rods and cones
Outer plexiform layer
- 1st synaptic layer, between photoreceptors and horizontal, amacrine and
Inner nuclear layer
- Cell bodies of horizontal, amacrine, bipolar and Müllers cells
Inner plexiform layer
- 2nd synaptic layer, between horizontal, amacrine and bipolar cells and
Ganglion cell layer
- Cell bodies of ganglion cells
Layer of optic nerve fibres
- Processes of ganglion cells travelling to the brain
Internal (Inner) limiting
- Composed of the basal lamina of Müllers cells
- The neural retina meets the optic nerve at the optic disc (or optic papilla), which is devoid of photoreceptor
cells, forming a blind spot in the visual field.
- The fovea, lateral to the optic disc, is the area of
greatest visual acuity, and is surrounded by a yellow
pigmented zone called the fovea lutea.
Chambers of the eye
- There are 3 chambers of the eye:
- The anterior chamber, between the cornea and the iris
- The posterior chamber, between the posterior surface of
the iris and the anterior surface of the lens
- The vitreous space, between the posterior surface of
the lens and the neural retina.
- This is a thin, transparent mucous membrane extending from the lateral margin of the
cornea, across the sclera, and covering the internal surface of the eyelids.
- It is composed of a stratified squamous columnar epithelium, containing many goblet
cells, that rests on a lamina propria of loose connective tissue.
- The lens is a transparent, avascular, biconvex structure that is suspended by the
suspensory ligament of the lens, and has 3 components:
- The lens capsule, produced by anterior lens cells
- A subcapsular epithelium, a cuboidal layer of cells
that is only present on the anterior surface of the lens
- Lens fibres, derived from the subcapsular epithelial cells, which lose their
nuclei and organelles to become filled with proteins called crystallins.