Ocular Conditions

By | 2011-11-26

Contents

BVA/KC/ISDS Eye Scheme

The British Veterinary Association/Kennel Club/International Sheep Dog Society Eye Scheme has been set up to enable breeders to reduce the frequency of inherited eye disease by screening dogs for these conditions prior to breeding. Screening is carried out by appointed eye panelists. A list of panelists can be obtained from the Kennel Club or British Veterinary Association.

Schedule 1 is a list of eye diseases of which it is considered that enough evidence exists to show that the condition is inherited in the breeds shown. Schedule 3 is a list of conditions under investigation for the possibility of inheritance in the breeds shown.

Conditions included in the scheme are those of the eye itself only, eyelid and lacrimal conditions are not included.

Canine anterior uveal melanoma

Melanocytic tumours of the iris or ciliary body. Most are unilateral and benign, however they may cause secondary glaucoma.

Caruncular trichiasis

Hairs growing from the conjunctiva at the medial canthus which may cause ocular irritation.

Cataract

An opacity which may affect all or part of the lens or lens capsule, unilaterally or bilaterally. Cataracts may be primary (where a hereditary basis is suspected) or secondary, e.g. to ocular inflammation, metabolic disease or congenital anomalies such as persistent pupillary membranes or persistent hyaloid artery.

Cataracts may be detected first in a variety of different areas of the lens and may progress at different rates. A complete cataract involves the whole lens and obscures the fundus, resulting in blindness in the affected eye.

Central progressive retinal atrophy (CPRA) or retinal pigment epithelial dystrophy (RPED)

Abnormal accumulation of pigment within the retina resulting in a progressive retinal degeneration and visual deficiencies. The condition was previously seen most commonly in England, but is now infrequently seen.

Chediak-Higashi syndrome

A condition seen in the Persian cat. Symptoms may include ocular and cutaneous albinism, cataracts, susceptibility to infection and bleeding tendencies. See also under Haematological/ Immunological conditions.

Chronic superficial keratitis (pannus)

A bilateral progressive inflammatory disease of the cornea. A fleshy, vascular lesion spreads towards the central cornea from the temporal limbus. Corneal pigmentation follows and, if severe, vision loss occurs. It is suspected to have an immune-mediated basis and is influenced by ultraviolet radiation. The condition is more severe in dogs living at high altitude. May be seen with Plasma cell infiltration of the nictitating membrane (plasmoma).

Coloboma

A congenital absence of part of an ocular structure which may affect the eyelid, iris, choroid, lens or optic disc.

Collie eye anomaly

A congenital condition characterised by abnormal development of the eye. The severity and effect on vision is variable. Mild cases may have only choroidal hypoplasia. More severe cases may also have optic nerve colobomas, retinal detachment and intraocular haemorrhage.

Congenital, subepithelial, geographic corneal dystrophy

A transient, non-inflammatory corneal opacity seen in puppies younger than ten weeks and absent by 12-14 weeks.

Convergent strabismus (esotropia)

Abnormal deviation of the eyeballs medially.

Corneal dystrophy

A primary, non-inflammatory bilateral opacity of the cornea. The term ‘dystrophy’ implies an hereditary nature of the condition. However, in many cases of corneal dystrophy firm evidence of inheritance is lacking, although no underlying disease can be found.

Different layers of the cornea may be affected giving epithelial, endothelial and stromal dystrophies. The appearance, age of onset and rate of progression vary with the breed. Visual disturbance may occur if the lesion becomes extensive.

Corneal sequestrate

A disease of the cornea seen in the cat. The disease is characterised by the development of a pigmented lesion in the centre of the cornea.

Dermoid

A congenital defect in which palpebral skin is abnormally located on the conjunctiva or cornea, often at the limbus, and may cause irritation due to the hairs growing from its surface.

Diamond eye

See Macropalpebralfissure.

Distichiasis

Abnormally positioned cilia (eyelashes) which emerge through or close to Meibomian gland orifices. They are often of no clinical significance but in some cases may cause ocular irritation.

Ectopic cilia

Cilia (eyelashes) which emerge directly through the palpebral conjunctiva to cause corneal irritation, ulceration and pain.

Ectropion

Eversion of all or part of the eyelid margin leading to exposure of the conjunctival tissues. In some cases this predisposes to conjunctivitis, epiphora and precorneal tear film deficiencies.

Entropion

An inward rolling of all or part of the eyelid margin resulting in irritation of the conjunctival and corneal surfaces.

Eversion of the cartilage of the nictitating membrane

Scrolling of the cartilage of the third eyelid which may result in chronic conjunctivitis. Seen most commonly in young large-breed dogs.

Fibrosing esotropia

Fibrosis of the extraocular muscles, particularly the medial rectus, leads to medial deviation of the eyeball. It is generally bilateral, but may be unilateral. It is most commonly seen in the Shar Pei.

Glaucoma (canine)

A group of diseases characterised by degeneration of the retinal ganglion cells and optic nerve resulting in progressive loss of vision. The condition is associated with an increase in intraocular pressure. Primary glaucoma develops without the presence of other intraocular disease and may be hereditary, with potential for bilateral involvement. Primary glaucomas may be divided by the appearance of the iridocorneal filtration angle into ‘open-angle’ and ‘closed-angle’ glaucomas. Causes of secondary glaucomas include lens luxation, uveitis, neoplasia and cataracts.

Generalised progressive retinal atrophy (GPRA)

Degeneration of the retinal cells. An autosomal recessive inheritance is suspected in most breeds. Different breeds are affected at different ages by different types of GPRA. However, all cases are bilateral and progress to blindness. The earliest clinical sign is night blindness with day vision being lost a variable time later.

Ophthalmoscopically there is attenuation of retinal vessels and tapetal hyper-reflectivity. In the later stages, the condition is often accompanied by cataracts. More than 100 breeds of dog have been identified as suffering from generalised progressive retinal atrophy; however, only those where the condition is seen relatively frequently, or is well-described, have been included in site.

Goniodysgenesis (pectinate ligament dysplasia)

Abnormal development of the iridocorneal filtration angle which may predispose to closed-angle glaucoma later in life.

Hereditary retinal dystrophy of Briards (congenital stationary night blindness)

A retinal dystrophy causing congenital night blindness with a variable effect on day vision. In most cases there is no progression of visual impairment. Nystagmus may be present.

Hemeralopia

Day blindness with no ophthalmoscopically visible abnormality. The condition results from selective degeneration of the cone photoreceptors of the retina. Dogs are able to see in dim light.

Idiopathic epiphora

The failure of normal tear drainage leading to overflow of tears over the lower lid, without evidence of increased tear production or obstruction of the drainage system.

Iris cyst

Cysts of the iris and ciliary body are usually benign and may be single or multiple, unilateral or bilateral. They may be congenital, or acquired secondarily to ocular inflammation or trauma.

Keratoconjunctivitis sicca (dry eye)

A common disease, characterised by reduced aqueous tear production resulting in drying and inflammation of the conjunctiva and cornea. The condition may be congenital (rarely), or result from infectious, drug-induced, neurological or immune-mediated causes. A genetic influence is suggested by the high incidence in a number of breeds.

Lacrimal punctal aplasia (imperforate lacrimal punctum)

A congenital anomaly where there is a failure of the lacrimal punctum (tear duct) to open. It may affect upper, lower or both punctae and may be unilateral or bilateral. The lower punctum is most commonly affected, resulting in epiphora (overflow of tears).

Lens luxation

Displacement of the lens from its normal position, which may be primary (and in some breeds inherited) or secondary to trauma, cataract formation, glaucoma, neoplasia or uveitis. Lens luxation is a potentially serious condition and may result in raised intraocular pressure and glaucoma. Where both lens luxation and glaucoma occur, it is not always clear which condition is primary. Primary lens luxation is usually bilateral though both lenses do not usually luxate simultaneously.

Limbal melanoma

These tumours are usually pigmented and found in the limbal region. They may invade the cornea. In older dogs they tend to remain static or grow slowly, in younger dogs growth is more rapid.

Lysosomal storage disease

An inherited deficiency of a specific degrada-tive enzyme leads to the accumulation of its substrate in cells, causing progressive cellular malfunction from an early age. Various enzymes may be involved and in some cases the eyes may be affected.

Macropalpebral fissure (euryblepharon)

An abnormally large palpebral fissure. In some cases (e.g. brachycephalic breeds), this occurs as a result of exophthalmos (protrusion of the globe), in others it results from overlong eyelid margins and may allow both entropion and ectropion to develop, resulting in ‘diamond eye’ in severe cases. The precorneal tear film is often disturbed, and corneal and conjunctival disease may occur secondarily.

Medial canthal pocket syndrome

The combination of a narrow skull with deep set eyes leads to the formation of a conjunctival pocket at the medial canthus, allowing the collection of debris which may cause recurrent conjunctivitis.

Microcornea

A congenital abnormally small cornea which may be associated with other ocular defects.

Micropalpebral fissure (blepharophimosis)

A congenital defect resulting in an abnormally small palpebral fissure.

Micropapilla

A congenitally small optic disc which is not associated with visual impairment. It may be difficult to distinguish from optic nerve hypo-plasia ophthalmoscopically.

Microphakia

A congenital defect resulting in an abnormally small lens, which may be associated with other intraocular defects.

Microphthalmia

A congenitally small eye, often seen with other ocular defects, e.g. microcornea, anterior chamber defects, cataract, persistent pupillary membranes and retinal defects (Multiple ocular defects).

Multiple ocular defects

Several congenital defects present in the same eye.

Nasal fold trichiasis

Prominent nasal folds in some breeds (notably the Pekingese) which allow the facial hair to come into contact with ocular tissues, causing irritation.

Neuronal ceroid lipofuscinosis

An inherited lipid-storage disease resulting in retinal degeneration and encephalopathy.

Nodular episclerokeratitis (fibrous histiocytoma, nodular granulomatous episclerokeratitis, proliferative keratoconjunctivitis)

Single or multiple, raised fleshy masses originating at the limbus and invading the cornea. Involvement of the nictitating membrane may occur. Usually a bilateral condition.

Nystagmus

Involuntary repetitive ocular movements.

Ocular melanosis

Large numbers of melanocytes infiltrate the iridocorneal angle, episclera, choroid and iris, predisposing to glaucoma (pigmentary glaucoma). Primarily seen in middle-aged Cairn Terriers.

Optic nerve coloboma

A congenital defect of the optic nerve head. The optic disc may appear irregular with a deep cavity. This defect may affect vision if large.

Optic nerve hypoplasia

A congenitally small optic disc with reduced numbers of optic nerve axons and visual impairment.

Pannus

See Chronic superficial keratitis.

Persistent hyaloid artery (PHA)

A congenital defect resulting from the failure of the hyaloid artery to regress. The remnant is seen as a segment (which may or may not contain blood) within the vitreal cavity between the optic disc and the lens. A cataract may form at the point of attachment to the lens capsule.

Persistent hyperplastic primary vitreous (PHPV)

A congenital condition in which there is abnormal development and regression of the hyaloid system and primary vitreous. It is often associated with persistent hyperplastic tunica vasculosa lentis (PHTVL) in which there is persistence of an embryonic vascular system attached to the posterior lens capsule. The condition is rare, but is seen more frequently in Dobermanns and Staffordshire Bull Terriers. The condition varies in severity. In its most severe form it is associated with microphthalmia and other ocular defects.

Persistent pupillary membranes (PPM)

Persistent pupillary membranes are uveal remnants which fail to regress normally in the first six weeks of life and persist in the anterior chamber (either unilaterally or bilaterally). Strands which bridge from iris-to-iris are generally of no clinical significance, however iris-to-cornea or iris-to-lens strands may cause focal corneal and lenticular opacities respectively. PPMs are a relatively common finding but severe visual impairment is rare.

Pigmentary keratitis

Corneal pigmentation is usually seen with chronic keratitis. Pigmentary keratitis is particularly common in brachycephalic breeds and may represent a pigmentary or epithelial dystrophy in these breeds.

Pigmentary uveitis

Inflammation of the iris and ciliary body associated with abnormal pigment deposition. Seen most commonly in the Golden Retriever and often seen in conjunction with iris cysts. Cataract and glaucoma are common sequelae.

Plasma cell infiltration of the nictitating membrane (plasmoma)

Bilateral plasma cell infiltration of the nictitating membrane resulting in follicle formation and depigmentation. Often associated with Chronic superficial keratitis (pannus).

Posterior lenticonus

A congenital abnormality where there is a conical protrusion of the posterior lens capsule and cortex into the vitreous. It may be associated with other ocular abnormalities and may be unilateral or bilateral.

Prolapse of the gland of the nictitating membrane (‘cherry eye’)

Prolapse of the tear gland normally located behind the nictitating membrane results in exposure and irritation of the gland. It is usually seen in young dogs, less than two years of age.

Proptosis

Anterior displacement of the globe with entrapment of the eyelids behind it. It usually results from trauma and occurs more easily in brachycephalic breeds.

Pseudopapilloedema

An enlarged optic nerve head due to excessive myelination of the optic nerve axons. No effect on vision.

Refractory corneal ulceration (indolent ulcer, Boxer ulcer, recurrent corneal erosion syndrome)

Slow-healing, superficial corneal ulcers which may represent a form of corneal epithelial dystrophy. Originally described in the Boxer, but also occurs in other breeds. Usually seen in middle-aged dogs.

Retinal detachment

Separation of the retina from the underlying tissues resulting in loss of function of the detached portion. May be partial or complete.

Retinal dysplasia

Abnormal differentiation of the retina present at birth. Retinal dysplasia may be inherited in some breeds. It may occur alone, or with other ocular defects or, in some cases, with skeletal defects. Three main forms exist:

• Multifocal retinal dysplasia: retinal folds exist as focal or multifocal lesions and appear as dots or linear streaks. Usually not associated with vision loss.

• Geographic retinal dysplasia: involvement of a larger irregular area of retina with some retinal elevation. May be associated with visual deficiencies.

• Total retinal dysplasia with detachment: the whole retina is involved and results in complete retinal detachment and vision loss.

Systemic histiocytosis (see also Histiocytosis under Neoplastic conditions)

A multisystemic disease characterised by infiltration of affected tissues with histiocytes. Ocular tissues may be affected, leading to uveitis, chemosis, episcleritis and conjunctivitis. The disease is primarily seen as a familial disease in the Bernese Mountain Dog.

Tapetal degeneration

An inherited condition seen in Beagles, wherein there is progressive degeneration of tapetal cells without any affect on vision.

Trichiasis

A condition in which normal hairs arising from the periocular or facial areas deviate to contact and irritate the cornea and conjunctiva.

Uveodermatological syndrome

This is believed to be an immune-mediated disorder similar to Vogt-Koyanagi-Harada syndrome seen in humans. Melanocytes are targeted by the immune system. Ocular signs include anterior uveitis, uveal depigmentation and retinal damage. Dermatological signs may include vitiligo (depigmentation) of the eyelids, nasal planum and lips. See also under Dermatological conditions.

Vitreal syneresis

Degeneration of the vitreous results in liquefaction. This is a common age-related finding and usually of no clinical significance. However, in some cases, extension of the abnormal vitreous into the anterior chamber may predispose to glaucoma. Rarely, it may predispose to retinal detachment.