The eyeball anatomy

the layers of eyeball, the parts, and features of the layers
along with the refractive media of the eyeball

1. The eyeball
All the information, including the images and pics
collected from different sources is strictly for teaching
purposes only.
G R N 1

2. Learning objectives
1.Name the layers of eyeball
2.Describe the parts and features of layers of eyeball
3.Describe the refractive media of the eyeball

3. The eyeball
•Outer surface of eye is
composed of parts of two
spheres with different radii.
•Anterior segment is part of
smaller sphere formed by the
transparent cornea(7% of
ocular surface).
•Posterior segment is part of
the larger sphere formed by
the opaque sclera.

4. The eyeball
1.Fibrous coat/layer
a)sclera
b)cornea
2.Vascular layer(uveal
tract)
a)choroid
b)ciliary body
c)iris
3.Neural layer or retina
(inner most)

6. 1.Fibrous layer(Tunica fibrosa)
It consists of two components: sclera &cornea
1. The sclera(= hard, tough) :
An opaque layer of dense connective tissue which gives shape
to the eyeball that can be seen anteriorly through its
conjunctival covering as the 'white of the eye'.
Occupies ~ five-sixths(5/6) of the surface (accounts 93% of the
outer coat) , extending from the entrance of the optic
nerve(scleral canal) to the corneoscleral junction anteriorly.
Provides attachment for the extraocular muscles
Anteriorly the external scleral surface is covered by conjunctiva
which is reflected onto it from the deep surfaces of the eyelids

8. Conjunctiva (Conj):
Thin, transparent,loose
connective tissue that covers
anteriorly, the sclera of the
eyeball (bulbar conjunctiva) and
reflects upon itself to line the
inner surface of the eyelid
(palpebral conjunctiva).
At the limbus, it meets the
cornea.
The accessory lacrimal glands
(Krause and Wolfring), along with
goblet cells, are contained within
the conjunctiva.
Keeps bacteria and foreign
material from getting behind eye
http://www.images.missionforvisionusa.org/anatomy/2005/11/conjunctiva-answers.html

9. Bilateral viral conjunctivitis presenting
with watering, red eyes.
Spring catarrh (vernal conjunctivitis)
with large flattened papillary hypertrophy
of upper palpebral conjunctiva

10. Pterygium(Surfer's Eye)-refers to a benign growth of theconjunctiva

11. The sclera
•It meets the cornea anteriorly at corneoscleral junction or
limbus.
•Punctured by several foramina:
1.Optic nerve( enters 3 mm medial to the posterior pole),
2.Long and short ciliary nerves and arteries(enter posteriorly)
3.Anterior ciliary arteries ( penetrate it anteriorly),
4.Vortex veins (cross the sclera equatorially),
•It is thickest posteriorly (~ 1000 μm=1mm ), decreasing
gradually towards the equator where it is only of 300μm
(=0.3mm)thick under the tendons of the recti.

12. Cornea
1.Transparent(allows light to enter
the eyeball), avascular structure.
2.Convex anteriorly
3.covers the anterior one-sixth of
the surface of the eyeball (1.1 cm
2
,
~ 7% of the external tunic area)
4.Horizontal diameter (11.7 mm) is
greater than its vertical (10.6 mm )
5.The cornea is approximately 700
μm(~ 0.7mm) thick close to the
corneoscleral junction, and
520 μm (~ 0.5mm) at its centre.
(thicker peripherally,thinner
centrally)
Cornea has the highest concentration of
nerve endings -extremely sensitive to
any kind of trauma.

13. Central pneumococcal corneal
ulcerwith hypopyon
(pus in anterior chamber).
corneal dystrophy
with diffuse corneal oedema

14. Cornea

15. Dense corneal opacity causing
blindness
After surgery, clear penetrating corneal
graft with continuous 10/0
monofilament nylon suture

16. 2.Vascular layer (Uvea)
•Internal to the sclera
•Consisting of three
continuous parts
1.A thin choroidlying
posteriorly
2.A thicker ciliary
body centrally
3.Andirismost
anteriorly

18. A). choroid
The choroid is a thin (60–160 μm, thickest behind macula) highly
vascular, pigmented layer which lines almost five-sixthsof the eye
posteriorly.
It is pierced by the optic nerve where it is firmly adherent to the
sclera and at the optic disc is continuous with the pia-arachnoid
layers around the optic nerve.
Its external surface is loosely connected to the sclera by the
suprachoroid layer (lamina fusca).
Internal surface is attached to the retinal pigment epithelium Four
layers can be identified in transverse section:
1.suprachoroid (lamina fusca),
2.vascular(large& small vessels) stroma,
3.choriocapillaris and
4.lamina vitrea (Bruch's membrane)

19. A). choroid

20. Triangular -shaped
structure forming a
complete ring around the
eyeball(lies between the
choroid and the iris).
In cross section the ciliary
body is composed of four
layers (from internal to
external):
1.Epithelium(a double
layer of epithelial
cells),
2.Stroma ,
3.Ciliary muscle and
4.Supraciliary layer
B. Ciliary body

21. B.Ciliarybody
•It is externallymarked by a
line which extends from 1.5
mm posterior to the limbus
(corresponding also to the
scleral spur) to a line
approximately 7.5–8 mm
posterior to this .
•It projects posteriorly from
the scleral spur( which is
its attachment) with a
meridional width of ~from
6.0 mm.
•Anteriorly, it is confluent with
the periphery of the iris, and
forms the lateral boundary
(externally bounds) of the
iridocorneal angle of the
anterior chamber.

22. B. Ciliary body
Internally, it’s
posterior limit is the
ora serrata –a
crenated or
scalloped periphery,
where it is
continuous with the
choroid and retina .

23. •Note thelens, attached by the
fibres of the zonule of Zinn
(suspensory ligament or ciliary
zonule) to the ciliary
processes (pars plicata ciliaris
or corona ciliaris–a ) of the
ciliary body
•Note the pars
plana ciliaris (b) or orbiculus
ciliaris of the ciliary
body which has a scalloped
posterior limit, theora serrata
(c)-separates it from the retina
(d).
The ciliary region(0.6mm meridional width) seen from the
ocular interior

24. The ciliary region seen from
the ocular interior
The ciliary muscle

25. Action of ciliary muscle-Accommodation reflex
•At rest lens is under tension
from zonular ligaments and
hence flattened
•On accommodation, ciliary
muscle contracts(shortens)
•Tension on the zonular
ligaments is relaxed
•Once tension on it is
released it assumes more
convex shape suitable for
focusing closer objects

26. Accommodation

27. Functions of the ciliary body
•Anchors the lensvia suspensory ligament(ciliary zonule of Zinn)
•Changes the refractive power of the lens (accommodation) by the
contraction of its smooth muscle( musculus ciliaris) .
•Its anterior internal surface is also the source of aqueous humour,
while posterior internal surface is contiguous with the vitreous
humour and secretes several of its components.
•The anterior and the long ciliary arteries meet in the ciliary body
and the nerves to all the anterior tissues of the eyeball pass
through it.

28. C. Iris
•Ring shaped tissue with a central
aperture known as the pupil ,whose
size can be adjusted
•Colored part of eye
•It is positioned between the cornea
and lens and is immersed in aqueous
fluid
•Controls the amount of light that
enters the eye like an adjustable
diaphragm
•Has two muscles : by the action of
these two muscles, the pupillary
aperture is adjusted
1.Sphincter pupillae-constricts pupil
2.Dilator pupillae
Iris divides the anterior segment into
an anterior chamber, enclosed by the
cornea and iris and aposterior
chamber, which lies between the iris
and the lens anterior to the vitreous.

29. Muscles of Iris

30. Lens
•Lens is located immediately behind
Iris
•Biconvex, transparent, colorless
•No vessels, no nerves
•10 mm.in diameter,4 mm.thick
•It is suspended from ciliary body by
theZonule of Zinn.Zonular fibres
attach to the lens either sides of its
equator
•Smooth muscle within ciliary body
regulates tension exerted on lens
and determine its shape
(contributes to accommodation).
•Consist of :
–Lens capsule
–Anterior lens epithelium
–Lens substances: cortex(new
f.)&nucleus(old f.)

31. Mature cataract where entire lens
becomes opaque

32. Chambers of eyeball
Iris and lens separate eye
into three chambers
1.Anterior chamber
2.Posterior chamber
3.Vitreous chamber

33. Posterior and anterior chambers
•Spaces between lens and
iris, & iris and cornea are
the posterior and anterior
chambers respectively
•They are filled with
aqueous humour
•Aqueous humour provides
metabolic support to the
avascular lens and cornea.

34. Vitreous chamber
•Vitreous chamber, is
filled with vitreous
humour
•It lies posterior to
lens
•Comprising about
two-thirds of
volume of eye

36. Vitreous Hemorrhage
Blood becomes trapped in
vitreoushumor and does
not immediately sink to the
bottom of the eye or
dissolve. Thus, symptoms
usually include seeing
floaters or spots in the
vision which increase with
time. The most common
cause found in adults
isdiabetic retinopathy.

37. Circulation of aqueous humour
•Ciliary process
•Posterior chamber
•Pupil
•Anterior Chamber
•Absorbed at the
irido-corneal angle
drained via canal of
Schlemm

38. Aqueous humour drainage
•It is drained out from eye
through canal of
Schlemm(sinus venosus
sclerae) at the iridocorneal
(filtration) angle
•Iridocorneal (filtration)
angle formed between
posterior aspect of
corneoscleral limbus and
periphery of iris.

39. Gonioscopy
Gonioscopy

40. Retina(Tunica interna / nervosa)
•Most internal layer of eye, facing the vitreous
–Acts like the film in a camera to create an image having
photoreceptor cells(RODS & CONES). Rods-low light
situations, Cones-allows you to see color
•Converts light energy into electrical energy which is then
sent to the brain via the optic nerve
•Actually, an extension of brain tissue
•Microscopically composed of 10 layers

41. The retina
Thin layer of cells lining the inner surface of the eyeball, thickness ranges
from 100 μm (at its edge) to 300 μm (at the foveal rim).
It is sandwiched between the choroidexternally and the vitreous body
internally and terminates anteriorly at the ora serrata .
Can be viewed with an ophthalmoscope (fundus examination of the eyes)
During fundoscopy following features are seen:
1.Blood vessels emanating from and entering the optic disc
2.‘central retina’ or macula lutea (approximate diameter 5–6 mm): lies
temporal side and inferior to the disc, which is an avascular ,darker area
compared to the rest of the fundus ,the middle of which is composed of
the fovea and foveola, .The lack of blood vessels at the foveola more
clearly seen in a fluorescein angiogram
3.‘peripheral retina’–all that lies outside the central retina.

42. The retina is made up of 120-160 million rods and 6-8 million
cones which can be divided into "red" cones (64%), "green"
cones (32%), and "blue" cones (2%).
Fundoscopic view of Retina

43. Macula
Located in the central part of the
retina
Responsible for giving sharp
central vision(visual acuity)
Used for reading, recognizing
faces, and watching TV
Any disease that affects the
macula will cause a change &
impairment in the central
vision/visual acuity
http://www.dukehealth.org/eye_center/specialties/macular_degeneration/care_guides/macular_degeneration
_frequently_asked_questions

44. DESCRIPTION OF THE FUNDUS
Optic disc
•Colour —Pink, temporal side
usually paler.
•Margin —Sharp and flat.
Nasal margin may be
relatively blurred and raised
(in hypermetropia).
•Many normal variations
including pigmentation and
myopic crescent.
•Cup —Varies in size and
depth. Situated at centre of
disc and slopes temporally.
•Cup/disc ratio —is ratio of
diameter of cup to that of
optic disc.
Normal optic disc with cup/disc
ratio 0.4.

45. Retinal vessels
•Colour —Arteries lighter than
veins.
•Diameter —Arteries narrower
than veins. Ratio approximately
2:3.
•Crossing —Arteries cross anterior
to veins at arteriovenous
•crossings.
Fundus background
•Colour —Red fundal background
because of the choroidal vessels
and retinal pigment layer.
•Darker in pigmented races. In
lightly pigmented persons, large
choroidal vessels seen against the
white sclera. Tessellated (tigroid
appearance) in myopia.
Macular area
•Colour —Normally darker than
rest of fundus. At centre, normal
foveal light reflex.

47. Fundoscopic
appearance of Large
terminal
glaucomatous cup
with cup/disc ratio 1.0
and optic atrophy
(note: eye is blind)

48. Fundoscopic appearance of Papilloedema

50. Central Retinal Artery Occlusion (CRAO)
•True ophthalmic emergency!
•Sudden painless and often severe visual
loss
•Permanent damage to the ganglion cells
caused by prolonged interruption of retinal
arterial blood flow
•Characteristic “ cherry-red spot ”
•No optic disc swelling unless there is
ophthalmic or carotid artery occlusion
•Months later, pale disc due to death of
ganglion cells and their axons