Gross pathology and Histopathology Wound healing Sequalae of ocular trauma Specimen Handling

1. BASIC PATHOLOGY IN
OPHTHALMOLOGY
DR NAIGA MAGEMBE HAWA , MBCHB
YEAR I MASTERS IN OPHTHALMOLOGY

2. SCOPE
• GROSS PATHOLOGY
• HISTOPATHOLOGY
• WOUND HEALING
• HISTOLOGIC SEQUELAEOF OCCULARTRAUMA
• SPECIMEN HANDLINGTECHNIQUES

3. PATHOLOGY
• the science of the causes and effects of diseases, especially the branch of
medicine that deals with the laboratory examination of samples of body tissue for
diagnostic or forensic purposes.
Histopathology : the study of changes in tissues caused by disease.

4. Inflammation
• is the response of tissue to a noxious stimulus.
• The response can be localized or generalized, and the stimulus can be infectious or
non-infectious.
• Non-infectious can be exogenous / endogenous
• Exogenous causes originate outside the eye, e.g. penetrating trauma, alkali
chemical injury, or external allergens.
• Endogenous causes originate in the eye and body such as uveitis secondary to
leaked lens matter (phacoantigenic uveitis), spread from adjacent structures (the
sinuses in orbital cellulitis), and haematogenous spread.
• Can be acute and chronic

5. Mediators
Chemical mediators
• Histamine
• Serotonin
• Leukotrines
• Prostaglandins
• Cytokines

6. Cell mediators
ACUTE
• Polymorphonuclear leukocytes (PMNs), including neutrophils, eosinophils, and
basophils
• Neutrophils(acute inflammatory cells) Multisegmented nucleus and
intracytoplasmic granules
• Eosinophils- Bilobed nuclei and prominent intracytoplasmic eosinophilic granules
• Mast cells are the tissue- bound equivalent of the blood-borne basophils.

7. Cont
CHRONIC
• Monocytes that migrate from the intravascular space into tissue are classified as
histiocytes or macrophages. Epitheloids (epithelial like histiocytes). Epithelioid
histiocytes may form a ball-like aggregate known as a granuloma.
• Multinucleated giant cell (merged epitheloid/monocytes) eg Langhan’s giant cell,
Foreign body giant cell,Touton giant cell
• Lymphocytes
• Plasma cells
• Eosinophils

8. Polymorphonuclear leukocyte with
multisegmented nucleus

9. Eosinophil with bilobed nucleus
and intracytoplasmic eosinophilic granules

10. Basophil with intracytoplasmic
basophilic granules

11. Monocyte with indented nucleus

12. Lymphocyte with small, hyperchromatic
nucleus and scant cytoplasm

13. Granulomas with necrotic centers
(arrows) are classified as caseating
granulomas

14. Langhans giant cell. Note peripheral
arrangement of nuclei

15. Touton giant cell. Note central
eosinophilic cytoplasm and annulus of nuclei
surrounded by lipid- filled clear zone

16. Foreign body giant cell. Note haphazardly
arranged nuclei

17. Acute Inflammation
Five cardinal signs :
1. Rubor (Redness) - increased blood flow
2. Calor (Heat) - increased blood flow
3. Tumour (Mass) - oedema caused by leakage of fluid andcells
4. Dolor (pain)
5. Loss of function
• The triple response - refers to the behaviour of blood vessels in damaged tissue

18. Acute
• Neutrophils are the main infl ammatory cells in the acute phase of infl ammation.
They are thought to follow a chemotactic stimulus released by vascular
endothelial cells, leukocytes, mediators of complement, or even bacteria
themselves at the site of injury
• There are many chemical mediators involved in acute infl ammation. In addition to
this, those present in plasma are interrelated cascade systems, including the
clotting cascade, fibrinolysis, complement, and bradykinin systems.
• The outcome of acute inflammation is dependent on many factors, for example in
infectious cases the organism, host response, and extent of necrosis.
• Acute inflammation may resolve, repair with scarring, or progress to chronic
inflammation.

19. CHRONIC
May start as chronic or result from acute inflammation
Proliferative inflammation characterized by acellular infiltrate of lymphocytes and
plasma cells (sometimes polymorphonuclear neutrophils (PMNs) or eosinophils)
Granulomatous and non-granulomatous.

20. Granulomatous
• Granulomatous -The characteristic cell type in granulomatous inflammation is the
epithelioid or giant cell. Classic examples include tuberculosis and sarcoid
• Three patterns
• Diffuse type: sympathetic uveitis, juvenile xanthogranuloma,Vogt–Koyanagi–Harada
syndrome, toxoplasmosis. Epithelioid cells are distributed randomly against a
background of lymphocytes and plasma cells.
• Discrete type: sarcoidosis, tuberculoid leprosy, military tuberculosis. Nodules or
tubercles form due to accumulation of epithelioid or giant cells surrounded by a narrow
rim of lymphocytes and plasma cells.
• Zonal type: caseous necrosis of tuberculosis, chalazion, ruptured dermoid cyst, reaction
to suture material, rheumatoid scleritis, toxocara. A central area of necrosis surrounded
by a palisade of epithelioid cells. In addition, PMNs, Langhan’s giant cells, and
macrophages are in turn surrounded by lymphocytes and plasma cells

21. Non-granulomatous
• Cell types may includeT and B lymphocytes, plasmacytoid cells (a variation of the
plasma cell), and plasma cells with a Russell body. A Russell body is an inclusion in
a plasma cell whose cytoplasm is fi lled and enlarged with eosinophilic structures.
The nucleus is eccentric or absent.These are seen in B cell lymphomas.
• Examples include the many forms of anterior and posterior uveitis, Behcet’s
disease, multiple sclerosis, retinal vasculitis, and endocrine exophthalmos

22. Noncaseating granulomas, or
“hard” tubercles, are formed by aggregates
of epithelioid histiocytes

24. CELLULARANDTISSUE REACTIONS
• Hypertrophy: an increase in size of cells, fi bres, or tissues without an increase in
number (e.g. RPE hypertrophy).
• Atrophy: a decrease in size of cells, fi bres, or tissues.
• Hyperplasia: an increase in the number of individual cells in a tissue; their size may
or may not increase. Growth will reach equilibrium and is not indefi nite (e.g. RPE
hyperplasia secondary to trauma).
• Hypoplasia: arrested development of a tissue during embryonic life (e.g. aniridia)

25. CONT
• Aplasia: lack of development of a tissue in embryonic life (e.g. aplasia of the optic
nerve).
• Metaplasia: the transformation of one type of tissue into another type (e.g. in
anterior subcapsular cataract fibrous metaplasia of the lens epithelium).This can
arise due to chronic irritation and will usually involve columnar or cuboidal
epithelium changing to squamous epithelium.
Dysplasia: abnormal growth of tissue with increased mitoses and reduced diff
erentiation (e.g. retinal dysplasia). Dysplastic tissue is not invasive and will not pass
through the basement membrane

26. Ageing, degeneration, and dystrophy
The term degeneration refers to a wide variety of tissue changes that may occur over
time. It occurs in tissue that has reached its full growth and can come in many
forms.
Not usually associated with a proliferation of cells; rather,there is often an
accumulation of acellular material or a loss of tissue mass. Extracellular deposits
may result from cellular overproduction of normal material or metabolically
abnormal material.These processes may occur in response to an injury or an
inflammatory process.

27. TYPES OF DEGENERATION
• Hyaline e.gWalls of arteriolosclerotic small vessels of the eye in ageing,benign hypertension,
and diabetes
• Amyloid e.g solitary nodule in eyelid, orbit, conjunctiva—in the cornea it can be seen in lattice
dystrophy and gelatinous drop-like dystrophy
• Hydropic e.g Infection, intoxication, anaemia, or circulatory disturbance
• Cloudy swelling e.g Mild infection, intoxication, anaemia, or circulatory disturbance
• Calcification Band keratopathy involves calcification of Bowman’s layer and the superficial
stromaThis also occurs in hyperparathyroidism, hypervitaminosis D,and sarcoidosis.
Cataracta ossea is calcification in the fibrous and degenerative cortex of the lens Bruch’s
membrane can be calcified in Paget’s disease In phthisis bulbi, ossification of the metaplastic
fibrous tissue derives from proliferation of the RPE in a hypotonic eye.Woven and lamellar
bone is located on the inner surface of Bruch’s membrane Ossification can extend into the
vitreous and choroid

28. cont
• Elastotic e.g Skin in ageing individuals, pterygia and pseudoxanthoma elasticum in
which ruptures in Bruch’s membrane expose the choroid (angioid streaks)
• Fatty change - Arcus senilis of the cornea—fatty infiltration of the
peripheralcorneal stroma Xanthelasma—lipid within clumps of macrophages in
the dermis of the eyelid seen in ageing and hypercholesterolaemia Deposition of
lipid and cholesterol in the intima of arteries, leading to atheroma, can lead to
thrombosis
• Glycogen infiltration e.g Diabetes mellitus-lacy vacuolation of iris pigment
epithelium Long-standing neural retinal detachment due to lack of nutrition and in
proliferating RPE cells

29. DYSTROPHY
• Dystrophy is a primary, inherited disorder that can occur at any age. Dystrophies
may involve a single matrix component.
• Usually bilateral, symmetric, inherited conditions that appear to have little or no
relationship to environmental or systemic factors. Eg corneal dystrophies

30. AGEING
Ageing involves:
• a decline in tissue cellularity
• a reduction in blood fl ow due to vascular disease
• atrophy of tissue
• tissue replacement with an acellular collagenous matrix.

31. NEOPLASIA
• Increase in the number of cells in a tissue; growth exceeds and is uncoordinated
with that of the normal tissues.This results in a neoplasm, which persists in an
excessive manner after cessation of the stimuli that evoked the change.
• stereotypic, monotonous new growth of a specific tissue phenotype.
• Neoplasia is caused by an upregulation of proliferation(excessive or inappropriate
oncogene action) or a failure of mechanisms that lead to cell death (tumour
suppressor genes).
• A neoplasm may be benign or malignant.
• General histologic signs of malignancy include nuclear hyperchromasia and
pleomorphism, necrosis, hemorrhage, and mitotic activity.

34. General classification and growth patterns of
malignant tumors

35. WOUND HEALING
The purpose of wound healing is to restore the anatomical and functional integrity
of an organ or tissue as quickly and perfectly as possible.
• The acute inflammatory phase may last from minutes to hours. Blood clots quickly
in adjacent vessels in response to tissue activators. Neutrophils and fluid enter the
extravascular space. Macrophages remove debris from the damaged tissues, new
vessels form, and fibroblasts begin to produce collagen
• Regeneration, the replacement of lost cells, occurs only in tissues composed of
cells capable of undergoing mitosis throughout life (eg, epithelial cells, fibroblasts)
Repair is the process of restructuring of tissues that leads to a fibrous scar.
• In the final phase, contraction causes the reparative tissues to shrink so that the
scar is smaller than the surrounding uninjured tissues.

36. CORNEA
Abrasion - Regenerates at the limbus and spreads rapidly across cornea
• Cell migration – parabasilar epithelial cells begin to migrate across the denuded area
until they touch other migrating cells; then contact inhibition stops further migration
[1hr]
• Proliferation - surrounding basal cells undergo mitosis to supply additional cells to cover
the defect
• Differentiation – restoration of the full thickness of epithelium (5–7 layers) and re-
formation of the anchoring fibrils [5 weeks]
If a thin layer of anterior corneal stroma is lost with the abrasion, epithelium
will fill the shallow crater, forming a facet
• Bowman’s layer-Does not regenerate
• Descemet’s membrane- Does not regenerate. Is elastic and can recoil at the edge of
a deficit

37. Corneal healing in a full thickness laceration
• Immediate phase: Retraction of Descemet’s membrane and stromal collagen,
anterior and posterior wound gaping of the wound, fibrin plug formation from
aqueous fibrinogen, and stromal oedema.
• Leukocytic phase: (30 min)polymorphonuclear leukocytes/ neutrophils from the
conjunctival vessels,tears and from the aqueous invade the wound. Limbal
wounds have an invasion of mononuclear cells from limbal vessels.These can
transform to fibroblasts after 12–24 hours.
• Epithelial phase: at 1 hour full thickness ingrowth is inhibited by healthy
endothelium.
• Fibroblastic phase: central corneal wound fibrocytes[fibroblast-like cells] are
derived from keratocytes.They produce collagen and mucopolysaccharides to
form an avascular matrix
• Endothelial phase: at 24 hours endothelial sliding allows for coverage of the
posterior wound.

38. Clear corneal wound. 1, Tears carry neutrophils with lysozymes to the wound within an hour. 2, Immediately after
closure of the incision, the wound edge shows early disintegration and edema.The glycosaminoglycans at the edge
are degraded.The nearby fibrocytes are activated. 3, At 1 week, migrating epithelial and endothelial cells partially
seal the wound; fibrocytes begin to migrate and supply collagen. the surrounding lamellae.The number of
fibrocytes decreases.

39. 4, Fibrocyte activity and collagen and matrix deposition continue.The endothelium, sealing the inner
wound, lays down new Descemetmembrane. 5, Epithelial regeneration is complete. Fibrocytes fill the
wound with type I collagen and repair slows. 6, The final wound contracts.The collagen fibers are not
parallel with the surrounding lamellae.The number of fibrocytes decreases.

40. Full- thickness corneal wound
(arrows) from cataract surgery

41. Sclera
• Differs from the cornea in that its collagen fibers are randomly distributed rather
than laid down in orderly lamellae, and dermatan sulfate is its glycosaminoglycan
• Relatively avascular and hypocellular
• Scars from episcleral and uveal fibroblasts
• When stimulated by wounding, the episclera migrates into the scleral wound,
supplying vessels, fibroblasts, and activated macrophages.The final wound
contracts, creating a puckered appearance.
• Dense adhesion between the uvea and the sclera if adjacent uvea involved
• Tensile strength of wounds is less than that of the native, undisturbed tissue thus
in certain clinical situations, modifying the healing process through the use of
topical chemotherapy, such as 5-fluorouracil or mitomycin C, or via collagen cross-
linking, may be desirable

42. Uvea
• Fibrinolysins in the aqueous inhibit fibrin clot formation, hence the patency of iris
defects If the edges of a wound appose, reactive proliferation of the iris pigment
epithelium can occur
• Though richly endowed with blood vessels and fibroblasts, the iris stroma does not
produce granulation tissue to close a defect
• Migration is usually limited to the subjacent surface of the lens capsule, where
subsequent adhesion of epithelial cells occurs (posterior synechia)
• Stroma and melanocytes of the ciliary body and choroid do not regenerate after
injury.Granulation followed by scar tissue forms from fibroblasts

43. Lens
• Epithelium responds to trauma by fibrous metaplasia
• Small tears in the anterior lens capsule are sealed by nearby lenticular epithelial
cells.
• In circumstances that make the lenticular epithelium anoxic or hypoxic, such as
posterior synechiae or markedly elevated intraocular pressure (IOP), a metaplastic
response may occur, producing fibrous plaques intermixed with basement
membrane

44. RETINA
• Retina is made of terminally differentiated cells that typically do not regenerate
when injured.
• Glial cells replace damaged nerve cells,which are derived from perivascular
astrocytes and Muller cells
• RPE can become metaplastic and proliferate and form fibrous tissue, for example
preretinal membranes
• Surgical techniques to close openings in the neurosensory retina are successful
when the retina and retinal pigment epithelium (RPE) are intentionally injured (eg,
as a result of cryotherapy, photocoagulation) forming an adhesive, atrophic scar

45. Vitreous
• Vitreous has few cells and no blood vessels
• The collagen fibrils of the vitreous can provide a scaffold for glial and fibrovascular
tissue from the retina and uveal tract to grow and extend into the vitreous to
proliferate as membranes.These membranes usually have a contractile
component, which can lead to retinal traction

46. Conjunctiva
• Can form granulation tissue
• Epithelium heals by sliding and proliferation similar to skin or cornea

47. SKIN
Epidermal
• (i) Cell migration, (ii) proliferation, (iii)diff erentiation
Dermal
• Invasion of fibrin clot by buds of endothelial cells from intact vessels
• Form blood vessels within 1 week
• Macrophages and fibroblasts invade wound
• Macrophages clear clots and fi broblasts produce collagen and
glycosaminoglycans. Myofibroblasts allow wound contraction by around 1 week

48. OPTIC NERVE
• Axonal loss and demyelination with reactive proliferation of glial cells and
connective tissue cells

49. Orbit and LacrimalTissues
The eyelid and orbit are compartmentalized by intertwining fascial membranes that
enclose muscular, tendinous, fatty, lacrimal, and ocular tissues; these tissues can
become distorted by scarring. Exuberant contraction distorts the muscle action,
producing dysfunctional scars.The striated muscles of the orbicularis oculi and
extraocular muscles are made of terminally differentiated cells that do not
regenerate, but the viable cells may hypertrophy.

50. Histologic Sequelae of OcularTrauma
The anterior chamber angle structures, especially the trabecular beams, are
vulnerable to distortion of the anterior globe.
• Traumatic recession of the anterior chamber angle - tear in the ciliary body between
the longitudinal and circular muscles with posterior displacement of the iris root
• Cyclodialysis - results from disinsertion of the longitudinal muscle of the ciliary
body from the scleral spur. Leads to hypotony
• Iridodialysis- tear in the iris at the thinnest portion of the diaphragm, the iris root,
where it inserts into the supportive tissue of the ciliary body
• Vossius ring- appears when iris pigment epithelial cells are compressed against the
anterior surface of the lens, depositing a ring of melanin pigment concentric with
the pupil.
• Cataract -The epithelium of the lens may be stimulated by trauma to form an
anterior fibrous plaque just inside the capsule.

54. Suprachoroidal hemorrhage. A, This eye developed an expulsive hemorrhage after
a corneal perforation. B, The intraocular suprachoroidal hemorrhage is dome shaped
(arrowheads),
delineated anteriorly by the insertion of the choroid at the scleral spur (arrow).

55. Iridodialysis. A, Clinical photograph of an eye showing iridodialysis, a disinsertion of
the iris root from the ciliary body. B, Gross photograph showing a posterior view of
iridodialysis (arrows).

56. Retinal dialysis.This photomicrograph illustrates the separation of the retina from
its normal attachment to the posterior edge of the nonpigmented epithelium of the pars plana
(arrowhead) at the ora serrata (asterisk). The vitreous base is still attached to the ora serrata
(arrows).

57. Cont
• Lens Displacement - lens zonular fibers are points of relative weakness; if they
rupture, lens displacement occurs, either partial (subluxation) or complete
(luxation)
• Vitreous prolapse - Focal areas of zonular rupture may allow formed vitreous to
enter the anterior chamber.
• Commotio retinae (Berlin edema) - complicates blunt trauma to the eye.Traumatic
retinopathy secondary to direct or indirect trauma to the globe. Retinopathy may
be present at areas of scleral impact (coup) and or distant sites (contrecoup)
including the macula.
• Retinal dialysis - Deformation of the eye can result in a circumferential retinal tear
at the point of attachment of the ora serrata or immediately posterior to the point
of attachment of the vitreous base

58. Anterior proliferative vitreoretinopathy (PVR). A, Traction of the vitreous base on
the peripheral retina (arrow) and ciliary body epithelium (asterisks). B, Incorporation of
peripheral retinal (arrow) and ciliary body tissue (arrowheads) into the vitreous base.

59. C, A condensed vitreous base (asterisk), adherent retina (arrow),
and RPE hyperplasia (arrowhead).

60. Cont
• Fibrocellular proliferation - Penetrating injury, may lead to
vitreous/subretinal/choroidal hemorrhage; tractional retinal detachment;
proliferative vitreoretinopathy (PVR), including anterior PVR ,hypotony; and
phthisis bulbi (discussed later)
• Sequelae of intraocular hemorrhage include hemosiderosis bulbi, cholesterolosis,
and hemoglobin spherulosis.
• Rupture of Bruch membrane or a choroidal rupture - Choroidal neovascularization,
granulation tissue proliferation, and scar formation.
A subset of direct choroidal ruptures, those usually occurring after a projectile
injury, may result in focal posttraumatic choroidal granulomatous inflammation.
This inflammation may be related to foreign material introduced into the choroid.

61. Focal posttraumatic choroidal granulomatous inflammation. A, An enucleated eye in which a projectile
caused a perforating limbal injury that extends to the posterior choroid.
B, Photomicrograph shows chronic inflammation with multinucleated giant cells (arrowheads)
in the choroid, focal RPE hyperplasia (arrow), and attenuation of photoreceptor outer segments
(asterisks).

62. Cont
• Chorioretinitis sclopetaria - Chorioretinal rupture and necrosis
• Phthisis bulbi - Atrophy, shrinkage, and disorganization of the eye and intraocular
contents.
• Atrophia bulbi without shrinkage - size and shape of the eye are maintained despite the
atrophy of intraocular tissues
• Atrophia bulbi with shrinkage - eye becomes soft because of ciliary body dysfunction and
the progressive diminution of IOP
• Phthisis bulbi - In this end stage, the size of the globe shrinks from a normal average
diameter of 23–25 mm to an average diameter of 16–19 mm. Most of the ocular
contents become disorganized. In areas of preserved uvea, the RPE proliferates, and
drusen may develop. In addition, extensive dystrophic calcification of Bowman layer,
lens, retina, and drusen usually occurs. Osseous metaplasia of the RPE with bone
formation may be a prominent feature. Finally, the sclera becomes markedly thickened,
particularly posteriorly.

63. A, Gross photograph showing a globe with irregular contour, cataractous
lens with calcification (asterisk), cyclitic membrane with adherent retina (arrowheads),
and bone formation (between green arrows). B, Photomicrograph demonstrating the histopathologic
correlation with the gross photograph shown in part A. In addition, organized ciliochoroidal
effusions are apparent histologically (yellow arrows)

64. SPECIMEN HANDLING
COMMUNICATION to pathologist
• before, during, and after surgical procedures
• relevant and reasonably detailed clinical history when submitting the specimen to
the laboratory
• Pathology request
• Previous tissue biopsy
• Need for normal tissue
• Biopsy technique

65. FIXATIVES
• 10% neutral- buffered formalin
• Formalin is a 40% solution of formaldehyde that stabilizes proteins, lipids, and
carbohydrates and prevents enzymatic destruction of the tissue (autolysis)
• glutaraldehyde for electron microscopy
• Ethyl alcohol for cytologic preparations
• Michel medium for immunofluorescence studies.

66. Cont
Because most of the functional tissue of the eye is located within 2–3 mm of the
surface, it is not necessary or desirable to open the eye.Opening an eye before
fixation may damage or distort sites of pathology, making histologic interpretation
difficult or impossible. It is generally desirable to suspend an eye in formalin in a
volume of approximately 10:1 for at least 24–48 hours prior to processing to ensure
adequate fixation. However, different institutions may use different protocols, so
preoperative consultation is critical.

68. Orientation
• Once the laterality of the eye is determined, accurate location of ocular lesions is
possible. Position of attachment of the inferior oblique

69. Posterior view of right globe. N = nasal,T = temporal. Diagram

70. Macroscopic photograph. Note that the posterior ciliary artery and nerve appear as a subtle blue-gray
line as they pass through the sclera.This marks the horizontal meridian of the globe. Also note that
the rectus muscle insertions are not present.The rectus muscles are typically incised at their
scleral insertion during enucleation so that they may be attached to the orbital implant

71. Gross dissection
• Prior to gross dissection, eyes are transilluminated with bright light. Identify
intraocular lesions such as tumors, which block the transilluminated light and cast
a shadow
• Shadow can be outlined with a marking pencil on the sclera
• Outline can then be used to guide the gross dissection of the globe so that the
center of the section includes the maximum extent of the area of interest
• Objective is to open the globe in such a way as to display as much of the
pathologic change as possible on a single slide
• Pupil-optic nerve (PO) section ; pupil and optic nerve are present in the same
section

72. Transillumination shows blockage
of light due to an intraocular tumor and The area of blockage is marked with
a marking pencil.

73. The opened eye shows the intraocular tumor that was demonstrated by
transillumination.
The paraffin- embedded eye shows the intraocular tumor

74. The hematoxylin- eosin (H&E)–
stained section shows that the maximum extent of the tumor demonstrated
by transillumination
is in the center of the section, which includes the pupil and optic nerve

75. Cont
• The meridian, or clock-hour, of the section is determined by the unique features of
the case, such as the presence of an intraocular tumor or a history of previous
surgery or trauma. In routine cases, eyes with no prior surgery or intraocular
neoplasm are typically opened in the horizontal meridian, which includes the
macula in the same section as the pupil and optic nerve
• Globes with a surgical or nonsurgical wound should be opened such that the
wound is perpendicular to, and included in the PO section.
• Globes with intraocular tumors are opened in a way (horizontal, vertical, or
oblique) that places the center of the tumor, as outlined by transillumination, in
the PO section
• The globe can also be opened coronally with separation of the anterior and
posterior segments, allowing a clinician’s view of posterior segment pathology

76. Gross dissection of a globe. A, The goal of sectioning is to obtain a pupil–optic
nerve (PO) section that contains the maximum area of interest. B, Two caps, or calottes, are
removed to obtain a PO section. C, The first cut is generally performed from posterior to
anterior. D, The second cut yields the PO section

77. Processing and staining
Tissue processing
• infiltration and embedding process replaces most of the water in the tissue with
paraffin
• organic solvents used in this process dissolve lipids and may dissolve some
synthetic materials
• Routine processing usually dissolves intraocular lenses made of polymethyl
methacrylate (PMMA), acrylic, or silicone
• Sutures made of silk, nylon, or other synthetic materials do not dissolve during
routine processing

78. Cont
• Embedding tissue in a paraffin block mechanically stabilizes the tissue, allowing
for cutting very thin sections through the tissue.
• Rapid processing - reserved for biopsy specimens that require urgent handling
• Because the quality of histologic preparation after rapid processing is usually
inferior to that of standard processing, it should not be requested routinely.
• Surgeons should communicate directly with their pathologists about the
availability and shortcomings of these techniques

79. Tissue Staining and Slide Preparation
Sections are usually cut at 4–6 μm
• Cut section is colorless except for areas of indigenous pigmentation, and various
tissue dyes—principally hematoxylin- eosin and periodic acid–Schiff (PAS)—are
used to color the tissue for identification
• A small amount of resin is placed over the stained section and covered with a thin
glass coverslip to protect and preserve it