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Head and Neck
15 September 2009
Victor L Caparas M.D.
OCULAR HISTOLOGY
OUTLINE
I. Objectives
II. Introduction
III. Instruments Used in Ophthalmology
IV. Trauma Case 1: The Flying Pool Cue
A. The Tunics of the Eye
B. Penetrated Structures
a. Conjuctiva
b. Sclera
c. Choroid
V. Trauma Case 2: The Near Sighted Med
Student
A. Myopia
B. Lasik Surgery
C. Affected Part
a. Cornea
VI. Trauma Case III: The Vanishing Golf Ball
A. Parts Involved
PLEASE REFER TO SUPPLEMENTARY POWERPOINT FOR MORE
HISTOLOGICAL IMAGES
D.
Optical Coherence Tomography – Electronic imaging
of retinal cross section; allows visualization of retinal
layers
IV. Trauma Case I: Un-planned Trauma
THE CASE OF THE FLYING POOL CUE
Case History
38-year-old male poked in the left eye, complaining of
severe headache and poor vision after being hit by a
pool cue.
Extraocular muscle limitation: 70% in all fields of gaze.
Cue stick penetrated the conjuctiva, sclera, choroid, and
retina and then reached the vitreous chamber
Discussion of the Case
A. The Tunics of the Eye
* a lot of structures of the eye change in appearance
when fixed with formalin to make the Histological slides
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I.
OBJECTIVES
A.
B.
C.
To know the layers and chambers of the eye.
To be able to describe the pathway of light.
Know the structure and components of the eye
Introduction
A. All organs in the body are composed of
proportions of only four basic tissues in the body. These are:

Epithelium

Connective Tissue

Muscle

Nervous Tissue
B. Each tissue consists of cells and extracellular
matrices.
C. Histology of the eye is NO DIFFERENT when it
comes to these structures.
Relative to Ophthalmology

Although the basic principles of
histology are the same for the eye, it has
special relevance to the practice of
Ophthalmology.

Much of clinical ophthalmology practice
relies on direct observation
measurement of the microscopic
structure of the eye.
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II.
III. Instruments used in Ophthalmology
A. Slit lamp bio microscope – use by all
ophthalmologists for PE of the eye
B. Specular Microscope – used if to visualize the
cells of the corneal epithelium
C. Retinal Microscope - to visualize capillaries,
arterioles and venules of the retina; used for
diabetic patients
Group 10
Jen, Margot, Issa, Louie, Caye, Zue 
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B.
Cornea

continuous with the sclera,
transparent, window to the eye,
where light passes through
Anterior Chamber

space behind cornea and before the
iris and lens; filled with aqueous
humor
Iris (360o structure)

functions as the “shutter”, opens
and closes depending on amount of
light
Lens

Structure of pure protein; hardest to
preserve histologically
Posterior Chamber

space behind iris anterior to the
zonules

zonules are tiny, finger like
projections of protein which serve as
attachments; also poorly preserved
histologically
Vitreous

Largest chamber of the eye
The cue stick penetrated the patient’s :
1. CONJUCTIVA
- Thin, transparent mucous membrane that
lines the posterior surfaces of the lids and the anterior
part of the globe up to the cornea.
- Conjunctival epithelium varies when it comes
to the shapes of its component cells. The cells may
range from stratified squamous to stratified columnar
(at the reflection from the sclera to the eyelid)
- The epithelium rests on a loose connective tissue layer
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- The part which lines the anterior part of the eye
ontains goblet cells which provide mucin needed
for a healthy tear film.
2. SCLERA
about 0.5 mm thick
Branches and anastosmoses so its very tough, looks
like an eggshell
The site of attachments of the extraorbital muscles
(EOMs)
Provides 4/5ths of the container of the eye (other
anterior 1/5 is provided by cornea)
continuous anteriorly with the limbus
Merges with the cornea and produces a protrusion
into the anterior chamber called the scleral spur
o Provides a point of insertion for part of
the ciliary muscle.
o Important to visualize in patients with
glaucoma
o Houses the Canal of Schlemm, where the
aqueous humor drains into ciliary veins.
o If the aqueous is not drained properly,
you can have build up which leads to
glaucoma
Sclera is more highly colored structure
histologically
Following the sclera posteriorly, it has parts which
merges where the nerve fibers from the retina
converge to form the optic disk
Here the sclera becomes sieve – like with
perforations where the optic nerve fascicles pass
This scleral sieve-like extension is called the Lamina
cribrosa
the perforations are called Laminar dots
the sclera therefore also serves as an anchoring
structure for the optic nerve
* Gonioscope – “gonio” means angle (referring to angle
formed by back of cornea and root of iris) You can visualize
the angle of the anterior chamber with this instrument
3. CHOROID
Uvea
o Anterior: Iris, ciliary body
o Posterior: Choroids
Vascular structure of the Retina; main function is to
provide blood supply
Innermost layer: Choriocapillaries
o Immediate blood supply of retina
Boundary between retina: Bruch’s membrane
(avascular and acellular)
Retinal pigment epithelium is the pigment cell layer
that is attached to the choroids. It provides
nourishment to retinal cells.
Outer part of choroids – extremely pigmented layer
V.
Trauma Case II: Planned Trauma
THE CASE OF THE HEAR-SIGHTED MED STUDENT
Case History
23-year-old, male, medical student
Group 10
 Jen, Margot, Issa, Louie, Caye, Zue 
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Complains of blurrings vision
-7.50 myope, bilateral
Structures involved (All are transparent):
1. Cornea
2. Aqueous
3. Crystalline Lens
4. Vitreous Body
Geeky med student decides that he doesn’t want to look
like a science geek anymore.
Elects for LASIK surgery.
Discussion of the Case
A. Myopia
Nearsightedness
Light rays from distant objects focus in front of the
retina, instead of focusing on the retina. So the image is
blurred
Decreases the convergence of light
When one wears glasses or contact lenses, it delays light
focus so it lands exactly on the retina
B.
C.
LASIK SURGERY
- corneal dissection, cutting a flap from the
cornea (lamellar flap);
- laser to cut a small layer (15mm) off from tissue
under flap;
then putting the flap back.
Done microscopically, under anesthesia,
fast operation, approx 5 mins
Affected Parts
1. Cornea
a. Anterior Cornea - 0.5mm thick
Layers
Squamous cell layer (flattened, with microvilli which
latch onto the mucins produced by goblet cells)
Cuboidal cells
Basal columnar cells (stem cells; as they move to the
surface they become more flat and form tight junctions,
establishing the blood-aqueous barrier)
Bowman’s layer (acellular layer under the epithelium’s
basement membrane)
*IMPORTANT: There are NO BLOOD VESSELS in the cornea.;
It has very few cells (keratocytes); and it is maintained in a
relatively dehydrated state
*THE PATHWAY OF VISION: Cornea to aqueous to crystalline
to vitreous body
b. Stroma
- Also called substantia propria, no blood vessels or
lymphatics
- forms 90% of cornea’s thickness;
- Contains regularly spaced collagen fibrils, normally
glycoprotein and mucoprotein, which makes cornea
transparent
- differentiated from sclera by looking at the fibers which
are uniformly arranged and set in unvarying layers at 90
degrees to each other.
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- Normally see stromal lamellae separated by clefts;
absence of clefts is caused by stromal edema, due to
damage of "endothelium"
-
Extends from the optic nerve anteriorly to the iris
Posterior Retina: Light-Receiving Structure
c. Posterior Cornea:
Stromal keratocyte
Stromal lamellae
Descemet’s membrane (A true basal lamina
produced by underlying corneal endothelial cells,
10-12 microns thick in adults; it continually thickens
throughout a person’s life)
Endothelium (single layer of cells, maintains
dehydrated state of cornea via an active pump that
pumps out solutes and electrolytes. It also forms
tight junctions and maintains the barrier,
preventing aqueous from coming in)
Light Pathway
Factors for Transparency of Cornea
1. no blood vessels
2. only a few cells are found in it
3. it is relatively dehydrated (compared to other
structures)
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VI. Trauma Case III
THE CASE OF THE VANISHING GOLF BALL
o
Case History
70-years-old, male, senior executive
Gradual, progressive blurring of the vision of the
right eye
Increased glare, decreased sharpness experienced
especially when the following flight of golf ball
Not much trouble “putting” or near distance
DIAGNOSIS: formation of Cataract
Discussion of Case III
A. Parts Involved
1. LENS: Light-Transmitting Media
Crystalline lens provides 1/3 of the refraction of the
eye
Layers composed of:
o Capsule –basal lamina, acellular
o Anterior subscapular epithelium
o Endothelium –

1 or 2 layers

Mitotically active cells

Responsible for producing the
lens fibers which are produced
continually.

Center of lens is oldest part and
newer layers are pushed out.

Anterior fibers are called
cortex.
o Cortical fibers/ epinucleus – layers of lens
fibers
o Nucleus – deepest part of the Lens
o Posterior Lens Capsule
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Retinal pigment layer

melanin/ pigment in this layer
absorbs the light.

That’s why albinos have poor vision,
they do not have pigment to catch
the light.
Rods and Cones layer

photoreceptors; cones on the
center, rods on the periphery of the
retina.

Turns optical energy to electrical
energy
Outer limiting membrane
Outer nuclear layer – conduit
Inner nuclear layer
Inner plexiform layer
Ganglion cell layer
Nerve fiber
Outer limiting layer
And then the signal passes through the optic
nerve and then to the back of the brain
* ora serrata – where the sclera meets the retina; where eye
injections are done because it is mostly avascular and you wont
hit the retina
3. CILIARY BODY
CIliary muscle: 3 bundles of smooth muscle with a bit of
connective tissue
Inner non-pigmented epithelium
Continuation of retina
4. CILIARY PROCESS and ZONULES
2. RETINA: Light-Receiving Structure
Inner lining of the eye
Group 10
 Jen, Margot, Issa, Louie, Caye, Zue 
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BATCH 2014  OCULAR HISTOLOGY
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Outer pigmented epithelium – nearer the sclera
(NOTE: Inner means it is nearer the Vitreous)
Inner, non-pigmented epithelium
Blood-retinal barrier
Similar to Ciliary Body but the muscle is mostly
replaced by vascular tissue
Fibrillin fibers extended from ciliary processes to
attach to equatorial anterior capsule of the lens
Suspensory ligament of the lens: zonules
Two bundles of ciliary muscle attach to the sclera.
o Stretch ciliary body, regulates tension of
zonules
o Change shape of lens: accommodation
.
-
where the aqueous is produced/ filtered from
blood plasma
*Blood retinal barrier (inner non pigmented epithelium) –
blocks medicine injected before the ciliary process.
5. IRIS
-
Anterior layer: Melanocytes
o Melanocytes are the cells that gives the
iris its color
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MORE REFERENCES:
OCULAR HISTOLOGY MANUAL
http://files.me.com/vcaparas/z5ky86
OCULAR HISTOLOGY STUDY SLIDES
http://files.me.com/vcaparas/82lki2
OCULAR HISTOLOGY LECTURE
http://files.me.com/vcaparas/dqraja
Group 10
 Jen, Margot, Issa, Louie, Caye, Zue 
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BATCH 2014  OCULAR HISTOLOGY
Group 10
 Jen, Margot, Issa, Louie, Caye, Zue 
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BATCH 2014  OCULAR HISTOLOGY
Group 10
 Jen, Margot, Issa, Louie, Caye, Zue 
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