The sclera, episclera and limbus

Natasha Mitchell

doi:10.22233/9781910443170.13

British Small Animal Veterinary Association , 232 (2014); https://doi.org/10.22233/9781910443170.13

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The sclera, episclera and limbus

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Author: Natasha Mitchell
From: BSAVA Manual of Canine and Feline Ophthalmology
Item: Chapter 13, pp 232 - 240
DOI: 10.22233/9781910443170.13
Copyright: © 2014 British Small Animal Veterinary Association
Publication Date: January 2014

Abstract

The chapter looks at the sclera, episclera and limbus, their anatomy and physiology; investigation of disease; canine and feline conditions.

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Figures

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13.2

Glaucoma secondary to chronic cataractous lens luxation. There is a circumlimbal brush-border of blood vessels (A). The congested episcleral blood vessels (B) are very prominent. Conjunctival blood vessels (C) are much narrower. © 2014 British Small Animal Veterinary Association

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13.2 Glaucoma secondary to chronic cataractous lens luxation. There is a circumlimbal brush-border of blood vessels (A). The congested episcleral blood vessels (B) are very prominent. Conjunctival blood vessels (C) are much narrower.

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13.3

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13.3 Corneoscleral limbus in a cat. A = major arterial circle of the iris; B = pigmented limbus; C = conjunctival blood vessels; D = deep scleral vessels.

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13.4

Conjunctiva extending over the limbus on to the cornea (‘conjunctivalization’ of the cornea) following a corneal/limbal injury in a 3-year-old Domestic Shorthaired cat. (Courtesy of D Gould) © 2014 British Small Animal Veterinary Association

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13.4 Conjunctiva extending over the limbus on to the cornea (‘conjunctivalization’ of the cornea) following a corneal/limbal injury in a 3-year-old Domestic Shorthaired cat. (Courtesy of D Gould)

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13.5

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13.5 Jaundiced (icteric) sclera and conjunctivitis in a dog with leptospirosis.

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13.6

Wide-field fundus image showing a large peripheral region of scleral ectasia (equatorial staphyloma) in an Australian Shepherd with merle ocular dysgenesis. (Courtesy of NC Buyukmihci) © 2014 British Small Animal Veterinary Association

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13.6 Wide-field fundus image showing a large peripheral region of scleral ectasia (equatorial staphyloma) in an Australian Shepherd with merle ocular dysgenesis. (Courtesy of NC Buyukmihci)

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13.7

Subgross photomicrograph showing a large area of scleral outpouching (*) in a dog with merle ocular dysgenesis. (Reproduced from Dubielzig et al., 2010 with permission from the publisher) © 2014 British Small Animal Veterinary Association

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13.7 Subgross photomicrograph showing a large area of scleral outpouching (*) in a dog with merle ocular dysgenesis. (Reproduced from Dubielzig et al., 2010 with permission from the publisher)

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13.8

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13.8 T2-weighted MR image of a cat that suffered blunt trauma showing interruption of the sclera nasally along with vitreal dislocation of the lens.

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13.9

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13.9 Epibulbar dermoid arising from the temporal limbus and affecting the temporal cornea in a 6-month-old crossbred collie.

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13.10

Sclerocornea in a 5-month-old English Cocker Spaniel with multiple ocular defects, including microphthalmia and persistent pupillary membrane. Note that the sclera has replaced the inferotemporal cornea. © 2014 British Small Animal Veterinary Association

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13.10 Sclerocornea in a 5-month-old English Cocker Spaniel with multiple ocular defects, including microphthalmia and persistent pupillary membrane. Note that the sclera has replaced the inferotemporal cornea.

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13.11

Diffuse episcleral hyperaemia associated with peripheral corneal oedema, stromal lipid deposition and neovascularization in a 5-year-old crossbred collie with generalized episcleritis. © 2014 British Small Animal Veterinary Association

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13.11 Diffuse episcleral hyperaemia associated with peripheral corneal oedema, stromal lipid deposition and neovascularization in a 5-year-old crossbred collie with generalized episcleritis.

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13.12

Focal thickening of the nasal episclera with extension into the adjacent cornea in a 2-year-old Cavalier King Charles Spaniel with regional episcleritis. © 2014 British Small Animal Veterinary Association

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13.12 Focal thickening of the nasal episclera with extension into the adjacent cornea in a 2-year-old Cavalier King Charles Spaniel with regional episcleritis.

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13.13

A focal nodular hyperaemic thickened region of episclera adjacent to the temporal limbus in a 4-year-old Border Collie with nodular granulomatous episcleritis. © 2014 British Small Animal Veterinary Association

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13.13 A focal nodular hyperaemic thickened region of episclera adjacent to the temporal limbus in a 4-year-old Border Collie with nodular granulomatous episcleritis.

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13.14

Gross pathology of an English Springer Spaniel with scleritis. There is tumour-like thickening of the episclera and sclera, extending from the limbus to the optic nerve. Note also the uveal thickening. (Courtesy of J Mould) © 2014 British Small Animal Veterinary Association

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13.14 Gross pathology of an English Springer Spaniel with scleritis. There is tumour-like thickening of the episclera and sclera, extending from the limbus to the optic nerve. Note also the uveal thickening. (Courtesy of J Mould)

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13.15

(a) Left and (b) right eye of a Labrador Retriever following a road traffic accident. (a) Note the blepharoedema, conjunctivitis, extensive corneal oedema and protrusion of the uvea through a large inferior scleral rupture at the limbus. (b) Note the blepharoedema, chemosis, conjunctivitis and pan-corneal oedema. Ultrasonography revealed rupture of the globe at the posterior pole. © 2014 British Small Animal Veterinary Association

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13.15 (a) Left and (b) right eye of a Labrador Retriever following a road traffic accident. (a) Note the blepharoedema, conjunctivitis, extensive corneal oedema and protrusion of the uvea through a large inferior scleral rupture at the limbus. (b) Note the blepharoedema, chemosis, conjunctivitis and pan-corneal oedema. Ultrasonography revealed rupture of the globe at the posterior pole.

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13.16

Laceration of the nasal cornea crossing the limbus to involve the adjacent sclera, resulting in protrusion of the underlying uvea, conjunctivitis and corneal oedema. © 2014 British Small Animal Veterinary Association

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13.16 Laceration of the nasal cornea crossing the limbus to involve the adjacent sclera, resulting in protrusion of the underlying uvea, conjunctivitis and corneal oedema.

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13.17

Gross enlargement of the right eye due to hydrophthalmos in a 12-week-old dog. Glaucoma occurred as a result of blunt trauma to the eye, and this led to exposure keratitis due to the inability to blink over such a large globe. © 2014 British Small Animal Veterinary Association

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13.17 Gross enlargement of the right eye due to hydrophthalmos in a 12-week-old dog. Glaucoma occurred as a result of blunt trauma to the eye, and this led to exposure keratitis due to the inability to blink over such a large globe.

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13.18

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13.18 Raised dark focal area adjacent to the superior limbus, consistent with an epibulbar melanoma.

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13.19

Multiple patches of dark pigment are visible within the sclera underlying the conjunctiva, along with episcleral congestion, corneal oedema and a dilated pupil in a Cairn Terrier with glaucoma secondary to ocular melanosis. © 2014 British Small Animal Veterinary Association

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13.19 Multiple patches of dark pigment are visible within the sclera underlying the conjunctiva, along with episcleral congestion, corneal oedema and a dilated pupil in a Cairn Terrier with glaucoma secondary to ocular melanosis.

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13.20

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13.20 Protrusion of uveal tissue through a cat scratch laceration at the superior limbus. Note the fibrin and blood visible in the anterior chamber.

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13.21

Gross pathology of a feline eye in which the sclera and lens were penetrated during a dental procedure. Features consistent with this form of penetrating trauma include the obvious scleral entry site (arrowed), dense infiltrate of inflammatory cells and protein exudation filling the anterior and posterior chambers and the vitreous cavity. Lens rupture was confirmed histologically. (Courtesy of J Mould) © 2014 British Small Animal Veterinary Association

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13.21 Gross pathology of a feline eye in which the sclera and lens were penetrated during a dental procedure. Features consistent with this form of penetrating trauma include the obvious scleral entry site (arrowed), dense infiltrate of inflammatory cells and protein exudation filling the anterior and posterior chambers and the vitreous cavity. Lens rupture was confirmed histologically. (Courtesy of J Mould)

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13.22

Gross pathology of a feline eye with a limbal (scleral shelf) melanoma. Note the outward extension of the pigmented mass and extension just into the iris base and angle. (Courtesy of J Mould) © 2014 British Small Animal Veterinary Association

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13.22 Gross pathology of a feline eye with a limbal (scleral shelf) melanoma. Note the outward extension of the pigmented mass and extension just into the iris base and angle. (Courtesy of J Mould)