Pathology of the and

Philippe Labelle, DVM, DACVP Antech Diagnostics 13th Biannual William Magrane Basic Science Course in Veterinary and Comparative

1 Cornea

• Congenital/dystrophies/degenerations • Non‐specific responses to injury • • Specific infections/conditions

2 General Considerations

• Cornea has limited ways it responds to injury • Cornea has limited healing capacity (to maintain function)

3 Dermoid

• Ectopic island of skin on cornea (or ) • Congenital choristoma • Has many or all features of normal skin • “Cutaneous metaplasia” is not analogous to a dermoid.

4 Dermoid

Courtesy UC Davis VMTH Ophthalmology Service

5 Dermoid

Courtesy of Dr. Chris Reilly

6 Dermoid

Hair follicle Thick pigmented epithelium

Sebaceous glands

Courtesy of Dr. Chris Reilly

7 and Degeneration

• Epithelial, stromal or endothelial • True dystrophy is bilateral and symmetric • Not associated with inflammatory or metabolic disease • Often breed‐related/heritable • Degeneration: Lesions secondary to other diseases, not true dystrophies

8 Corneal Epithelial Dystrophy

• Shetland Sheepdogs; Longhaired Dachshunds • Superficial punctate corneal dystrophy • Dysplasia of basement membrane • Dyskeratosis and necrosis of epithelium • Unlikely to be biopsied

9 Corneal Epithelial Dystrophy

10 Corneal Epithelial Dystrophy

Epithelial dystrophy in a Basilisk lizard H&E Deposition of excessive irregular PAS‐positive, basement membrane material both on PAS the basal aspect of the epithelium and in the epithelium

Courtesy of COPLOW

11 Mineral/Band Keratopathy

• Deposition of mineral in the basement membrane of the corneal epithelium and/or superficial stroma • Usually secondary (not a true dystrophy) • Inflammation and hypercalcemia are potential causes of secondary mineral deposition. • Horses (/ steroid and phosphate containing topical solutions)

12 Mineral/Band Keratopathy

• Calcareous degeneration: affects both the basement membrane area and the deep stroma; may be present in the absence of any other ocular disease • von Kossa stain highlights the phosphorus of the calcium‐phosphorus complex. Alizarine Red specifically stains calcium

13 Band Keratopathy

14 Band Keratopathy

15 Band Keratopathy

Courtesy of Dr. Chris Reilly

16 Stromal Lipid Dystrophy

• “Corneal dystrophy” • Bilateral and symmetrical with no association to metabolic disease • Accumulation of lipids within the stroma • Macrophages may border these foci • Acquired lipid keratopathy can be associated with corneal or adjacent disease, or metabolic disease; typically well‐vascularized

17 Stromal Lipid Dystrophy

• Lipids are dissolved during routine processing • Lipids appear as clear space/vacuoles/clefts • Cholesterol clefts angular or needle shaped clearings. It is one form of lipid accumulation • Special stains for lipid (Oil Red O, Sudan Black) can on be performed on fresh, frozen or fixed but unprocessed sections

18 Lipid/Cholesterol Dystrophy

19 Lipid Dystrophy/Keratopathy

20 Lipid Dystrophy/Keratopathy

Oil Red O, Courtesy of COPLOW

21 Lipid Dystrophy/Keratopathy

22 Lipid Dystrophy

Courtesy of Dr. Brian Stacy, UCDavis

23 Endothelial Dystrophy

• Most often secondary (not true dystrophy) • Primary in Boston terrier, Chihuahua • Initially affects the temporal cornea • Leads to corneal edema +/‐ ulceration • Endothelial cell attenuation

24 Endothelial Dystrophy

• Formalin fixation can cause artifactual vacuolation of the endothelium • Anterior uveitis, , surgery, anterior luxation, are possible causes of endothelial degeneration • Fibrometaplasia, retrocorneal membranes may be present with endothelial degeneration • The endothelium can slide but cannot replicate (post‐miotic) with rare exceptions (rabbits +\‐ dogs).

25 Endothelial Dystrophy

26 Cornea

• Congenital/dystrophies/degenerations • Non‐specific responses to injury • Keratitis • Specific infections/conditions

27 Inclusion cysts, epithelial downgrowth

• Cysts • Congenital or traumatic • Often secondary to surgery

• Epithelial downgrowth • Trauma, ulceration

28 Inclusion cyst

29 Epithelial nests/cysts

Courtesy of COPLOW

30 Epithelial Downgrowth

Courtesy of Dr. Chris Reilly

31 Epithelial Downgrowth

32 Epithelial Downgrowth

33 Descemet’s Membrane

• Duplication of Descemet’s membrane • Double layer of basement membrane • Relatively common • Trauma, lens luxation, glaucoma, surgery are possible causes • May accompany breaks in Descemet’s membrane • There may be endothelium lining one or both layers • Unclear significance unless associated with extension on the or traumatic lesions elsewhere – Kafarnik et al. Vet Path 2009

• Descement’s membrane detachment in horses with glaucoma causing corneal edema – Henriksen ML et al. VO 2017

34 Descemet’s Duplication

Courtesy of Dr. Chris Reilly

35 Descemet’s Duplication

36 Descemet’s Duplication

37 Descemet’s Duplication

38 Endothelial Pigment

• Secondary to release of uveal pigment • Neoplasia, inflammation, anterior , ruptured uveal cyst, iris‐cornea PPM • Does not appear to affect function (not associated with corneal edema)

39 Endothelial Pigment

40 Cornea

• Congenital/dystrophies/degenerations • Non‐specific responses to injury • Keratitis • Specific infections/conditions

41 Keratitis, General Considerations

• Ulcerative vs non‐ulcerative • Inflammatory cellular infiltrate • Acute = neutrophils • Chronic= lymphoplasmacytic • Corneal edema • Stromal neovascularization

42 Corneal edema

• Loss of normal lamellar arrangement of the stroma • Must be differentiated from fixation artifact causing separation of lamellae

43 Corneal edema

Edema Artifact

Courtesy of Dr. Chris Reilly

44 Corneal edema

45 Acute Bullous Keratopathy

• Cats • Severe corneal edema • Rupture of Descemet’s membrane • The cause is not known • An association with systemic anti‐ inflammatory/immunosuppressive drugs has been proposed • Pierce KE Jr et al. VO 2016; Pederson SL et al. VO 2016

46 Acute Bullous Keratopathy

47 Acute Bullous Keratopathy

48 Acute Bullous Keratopathy

49 Corneal Stromal Hemorrhage

• Clinical entity • Hemorrhage in all levels • Corneal vascularization present – Violette NP et al. VO 2017

50 Keratitis/Stromal Neovascularization

• Begins 48‐72 hours after injury • Progresses up to 1mm/24h • May be superficial, midstromal or deep, depending on the cause • Midstromal neovascularization can be secondary to uveitis

51 Keratitis/Stromal Neovascularization

Courtesy of Dr. Chris Reilly

52 Ulcerative keratitis

• Ulcerative keratitis • SCCED • Ulcerative keratitis with keratomalacia (melting ulcers)

53 Ulcerative keratitis

• Epithelial changes in the remaining epithelium include sliding, rounding of the epithelial edges, hyperplasia • Neutrophils predominate in acute cases • Lymphoplasmacytic infiltration, stromal fibrosis and neovascularization with chronicity

54 Ulcerative keratitis

55 Ulcerative keratitis

56 Ulcerative keratitis

57 Ulcerative keratitis

58 Ulcerative keratitis‐Descemetocele

59 Ulcerative Keratitis with Keratomalacia

• Melting ulcer • Horses, dogs (brachycephalic) +\‐ cats • Degeneration of stromal collagen • Metalloproteinases, serine proteases • Endogenous (inflammation/neutrophils) • Exogenous (some bacteria and fungi produce proteases)

60 Ulcerative Keratitis with Keratomalacia

61 Ulcerative Keratitis with Keratomalacia

Courtesy of Dr. Chris Reilly

62 Ulcerative Keratitis with Keratomalacia

Courtesy of Dr. Chris Reilly

63 Infectious Crystalline Keratopathy

• Clinical findings of anterior stromal crystaline opacities • Suspected to represent bacterial infection following epithelial injury • Ledbetter EC et al. VO 2017

64 Infectious Crystalline Keratopathy

Ledbetter EC et al. VO 2017

65 Chronic Keratitis (Nonspecific)

• “Chronic keratitis, superficial” • End result of a variety of corneal insults • It is not a disease, but a response pattern • Buphthalmos, /, neurogenic disorders, lacrimal/Meibomian disorders (KCS), irritation from a mass or issue • Frequent in enucleated globes • Severe cases may mimic Chronic Superficial Keratitis/Pannus

66 Chronic Keratitis (Nonspecific)

• Epithelial lesions (hyperplasia, pigmentation +\‐ keratinization) • Lymphoplasmacytic inflammation • Pigmentary incontinence (leakage of melanin) • Stromal fibrosis and neovascularization

67 Chronic Keratitis (Nonspecific)

68 Chronic Keratitis (Nonspecific)

69 Chronic Keratitis (Nonspecific)

70 Chronic Keratitis (Nonspecific)

71 Cornea

• Congenital/dystrophies/degenerations • Non‐specific responses to injury • Keratitis • Specific infections/conditions

72 Chronic Superficial Keratitis (Pannus)

• Immune mediated • German shepherds and sighthounds • Chronic lichenoid lymphoplasmacytic inflammation • Stromal fibrosis and neovascularization • Epithelial lesions (hyperplasia, pigmentation +\‐ keratinization) • Unlikely to be biopsied

73 Chronic Superficial Keratitis/Pannus

74 Chronic Superficial Keratitis/Pannus

75 Chronic Superficial Keratitis (Pannus)

Courtesy of Dr. Chris Reilly

76 Spontaneous Chronic Corneal Epithelial Defects (SCCEDs) • Dogs (Boxers), cats, horses • Separation of the epithelium and stroma results in erosion/ulceration • Separated epithelium shows dysmaturation with loss of organized layering • Thin, acellular, hyalinized band in the superficial stroma

• Murphy et al, IOVS, 2001; Bentley et al, IOVS, 2002; Gosling et al, VO, 2013; Hempstead JE et al VO, 2014.

77 SCCED

Courtesy of Dr. Chris Reilly

78 SCCED

79 SCCED

80 SCCED

*

81 Corneal Sequestrum

• Cats (Persians) +\‐ horses, dogs • Well‐circumscribed area of stromal devitalization, often with pigmentation • Some are not overtly pigmented • Acellular/devitalized/necrosis • Inflammation and neovascularization only at the periphery • Ulceration

82 Corneal Sequestrum

• Melanin? Iron? Porphyrins? • Association of feline herpesvirus in some studies, not in others

• Stiles et al, AJVR 1997 • Nassisse et al, AJVR 1998 • Ejima et al, Science 1993 • Featherstone et al, VO, 2004 • Cullen et al, VO 2005 • Newkirk et al, VO, 2011

83 Corneal Sequestrum

84 Corneal Sequestrum

85 Corneal Sequestrum

Courtesy of COPLOW

86 Corneal Sequestrum (dog)

87 Florida Keratopathy

• Florida spots • No convincing histologic lesions • Material in the picture in G5 may be acid fast positive; not acid‐fast bacteria • Sarfaty (ECVO 2008) suggests fire ants

88

• Horses +\‐ dogs, rarely cats • Neutrophils +\‐ keratomalacia +\‐ stromal abscess • Ulceration • Fungal hyphae may be numerous or rare • Fungal hyphae are mostly in the deep stroma • Fungal hyphae may invade Descemet’s membrane • Aspergillus spp, Fusarium spp. • Opportunistic fungal colinization of injured will be only superficial – Nevile JC et al. VO 2016

89 Fungal Keratitis

90 Equine Fungal Keratitis

Malacic stroma

Courtesy of Dr. Chris Reilly

91 Equine Fungal Keratitis

Courtesy of Dr. Chris Reilly

92 Equine Fungal Keratitis

93 Equine Fungal Keratitis

94 Fungal Keratitis

95 Fungal Keratitis

96 Fungal Keratitis

97 Protozoal Keratitis/

• Dogs, rare • Mass effect in the cornea +/‐ conjunctiva • Granulomatous/pyogranulomatous inflammation • Preexisting ocular surface disease, typically KCS • Immunomodulatory therapy • Amoeba, T. gondii, Leishmania (Beckwith‐Cohen B et al. VO, 2016; Swinger RL et al. VO 2009); Sarcocytis • Cats, rare, Amoeba, Spain (Montoya A et al. Exp Parasitol 2018).

98 Protozoal Keratitis/Conjunctivitis

Right (a) and left (b) eyes at the time the Right eye 2 months after protozoal conjunctivitis was diagnosed tacrolimus was discontinued and clindamycin initiated

Veterinary Ophthalmology Volume 19, Issue 3, pages 206-213, 3 JUN 2015 DOI: 10.1111/vop.12285 http://onlinelibrary.wiley.com/doi/10.1111/vop.12285/full#vop12285-fig-0002

99 Protozoal Keratitis/Conjunctivitis

100 Protozoal Keratitis/Conjunctivitis

Sarcocystis sp.

101 Feline Eosinophilic Keratitis/ • Proliferative keratitis • Proliferative gross appearance • Eosinophils are a component of the inflammation • Eosinophils may not be the predominant cell type (lymphoplasmacytic) • Herpesvirus infection, Mycoplasma, Chlamydophila • Typically unilateral • Typical cases unlikely to be biopsied

102 Feline Eosinophilic Keratitis/Keratoconjunctivitis

103 Feline Eosinophilic Keratitis/Keratoconjunctivitis

104 Feline Eosinophilic Keratitis/Keratoconjunctivitis

105 Feline Eosinophilic Keratitis/Keratoconjunctivitis

106 Feline Eosinophilic Keratitis/Keratoconjunctivitis

Herpesvirus dermatitis

107 Malignant Catarrhal Fever

• Bovine • Alcelaphine herpesvirus 1, ovine herpesvirus 2 • Endotheliitis

108 Malignant Catarrhal Fever

Courtesy of COPLOW

109 Canine Adenovirus

• Infection or some vaccines • Adenovirus type 1‐2 • Endothelial necrosis +\‐ inclusions • Results in severe corneal edema, “blue eye”

110 Canine Adenovirus

Courtesy of COPLOW

111 Canine Adenovirus

Adenoviral inclusion

Courtesy of COPLOW

112 Corneal Healing and Repair

• Healed corneal epithelium may be irregular • Basement membrane may be thickened • Stromal heals mostly with fibrosis +/‐ neovascularization • Descemet’s membrane can be doubled

113 Corneal Healing and Repair

114 Corneal Healing and Repair

115 Corneal Healing and Repair

116 Corneal Healing and Repair

117 Corneal Healing and Repair

118 Post Mortem Interval

• increases significantly at greater than 8 hours after death • Intraocular pressure decreased significantly from 12.8 to 5.7 mm Hg over the first 12 hours after death (handheld tonometer)

• Brooks JW. Postmortem Changes in Animal Carcasses and Estimation of the Postmortem Interval. Vet Pathol. 2016 Sep;53(5):929‐40.

119 SCLERA

120 Staphyloma

• Full or partial thickness scleral (or corneal) defect lined by protruding • Congenital or acquired (glaucoma, ocular melanosis) • Some cases with staphyloma present as a suspicion of neoplasia (melanocytic neoplasia)

121 Staphyloma

Courtesy of Dr. Carol Naranjo

122 Staphyloma

123 Granulomatous

• Severe granulomatous inflammation centered on the sclera • The term “necrotizing” causes confusion as it has been used in reference to cases with collagen degeneration/lysis or cases with neutrophils • Can extend in the uveal tract • No association with immune‐mediated diseases affecting other sites (except 1 dog). • Denk et al, VO, 2012; Day et al. VO, 2008.

124 Granulomatous Scleritis

Courtesy of Dr. Chris Reilly

125 Granulomatous Scleritis

Courtesy of Dr. Chris Reilly

126 Granulomatous Scleritis

Courtesy of Dr. Chris Reilly

127 Granulomatous Scleritis

Courtesy of Dr. Chris Reilly

128 Granulomatous Scleritis

Courtesy of Dr. Chris Reilly

129 Scleral Mineralization/Metaplasia

• Horses (mineralization) • Age associated change

• Sheep (cartilage, dorsal sclera) • Unclear significance; Smith et al, Vet Path, 2011

• Goats (cartilage +/‐ bone, typically dorsal or near ON) • Unclear significance; Tusler CA et al. VO 2016 Epub.

• Fisher rats (bone +/‐ cartilage, dorsal sclera) • Age associated change

130 Scleral Mineralization/Metaplasia

131 Scleral Mineralization/MetaplasiaFigure 1. Sclera; sheep No. 1.

Alcian blue Type II collagen IHC J. D. Smith et al. Vet Pathol 2010;48:827-829

Copyright © by American College of Veterinary Pathologists

132 Scleral Mineralization/Metaplasia

Tusler CA et al. VO 2016 Epub

133 Scleral Mineralization/Metaplasia

Tusler CA et al. VO 2016 Epub

134 Mineralization/Metaplasia

Guinea pig, uveal heterotopic bone

135 Scleral Rupture

136