Module 13 Flashcards
Inherited ocular disease in dogs - congenital
MODs, PPMs, cataract, PHPV
Congenital: can occur in any dog as a one off non-inherited spontaneous defect, but if bilateral and in predisposed breed then likely inherited.
- MODs - combination of microphthalmos, cataract, retinal dysplasia, nystagmus and PPMs. bilateral but not always symmetrical. Cockers, westies, golden retrievers, and border terriers
- PPM/persistent pupillary membranes - small insignificant remnants of mesodermal tissue, arise from iris collarette, tags that adhere to iris itself, lens capsule or corneal endothelium (see focal opacities) May form a cobweb like appearance across the visual axis and then may have effect on vision. Basenjis (inherited), Lancashire heeler, cockers and pugs. Not a fault for breeding
- Congenital cataract - nuclear, squashed with age so vision can improve, posterior lenticonus and microphakia can accompany the defect, as can microphthalmos and nystagmus (MODs). Mini Schnauzer only breed currently listed on UK testing scheme for congenital inherited cataract.
*Persistent Hyperplastic Primary Vitreous (PHPV) - Dobies and staffies. Fibrovascular plaque +/- pigment, seen on posterior aspect of the lens. Lenticonus or lentiglobus, colobomas, intra-lenticular haemorrhage, secondary cataract etc. may also be seen. Effect on vision variable.
Scoring system for Dobies:
1) capsular and retrolental pigment, minor posterior capsular cataract
2) denser, more intense cataract, pigment dots and yellow-brown fibrous tissue
3) grade 2 + hyaloid vessels
4) grade 2 + posterior lenticonus
5) 3+4
6) all of above plus lens coloboma, microphakia, miscophthalmos, IO haemorrhage.
Inherited ocular disease in dogs2 - congenital
CEA, retinal dysplasia, ON hypoplasia
*Collie Eye Anomaly (CEA) - rough and smooth collies, shertland sheepdogs, border collies, lancashire heeler. Dx best 6 weeks of age. Pathognomic sign is choroidal hypoplasia lateral to optic disc, vessels in the area are abnormal. May be difficult to appreciate in merle coloured dogs. 1/3 also have colobomas of ONH mostly but also peripapillary region. Retinal detachment and IO haemorrhage are less common. Condition is not progressive unless large colobomas result in retinal detachment at a few months. “go normals” - RPE covers defects.
Gene for CEA is on chromosome 37, recessive. likely polygenetic hence wide variety of clinical signs
*Retinal dysplasia - retina fails to differentiate normally.
1) multifocal (multifocal or geographic)
2) total (rare - born blind)
MRD generally less severe, can be detected at 6 weeks. Focal retinal detachment in geographic form. ESS (can look like inactive choroiditis in this breed), CKCS, rottweiler, ACS, golden and lab retrievers. Generally does not affect vision unless form retinal detachments. Not progressive but lesions can change with remodelling during development, best examine at 6 weeks or after remodelling at >12 weeks
TRD renders dogs blind - retinal non attachment. Sealyham and Bedlington terrier in the uk. labrador and samoyeds not currently in the UK but seen in associated with osculoskeletal dz (short-limbed dwarfism).
*Optic nerve hypoplasia - failure to develop, blindness. Dark and small. Toy and miniature poodles. Often unilateral. micropapilla - smaller than expected but some vision.
Inherited ocular disease in dogs3
Glaucoma
Inherited glaucoma: may be born with abnormalities but signs may not develop until adulthood, especially in POAG.
- POAG: no clinical abnormalities prior to onset of glaucoma, may present with dilated pupil or subluxated lens. Closure of angle very late in disease process.
- Petit Basset Griffon Vendeen (DNA test available)
- Basset (DNA test available)
- Shar pei
*PCAG: abnormalities in the pectinate ligaments and drainage angle. Screening from 6 months can eliminate from breeding pool. Presents as an acute emergency. Gonioscopic findings are not static as once believed and iridocorneal angle changes with ageing. Repeated examinations are advised from susceptible breeds - currently q3years. Pilot grading scheme started 2017, incorporated into eye scheme 2018.
0 = normal, 1 = <25% affected, 2=25-75%, 3= >75% (DO NOT BREED)
Acquired inherited dz - breed related
Divided into :1) Inherited dz we are concerned about - retinal and lens and 2) breed associated dz which are conformational issues which are multifactorial
Breed associated conditions:
*Eyelids: entropion in sher pei, chow chow, labrador, spaniels. Should not be bred from. Ectropion is common is loose skin breeds, may not cause a problem but predisposes to conjunctivitis. Giant breeds tend to suffer from a combination of entropion and ectropion - diamond eye.
TEL scrolling and prolapse of TEL gland requiring sx correction, should not be considered for breeding
*Eyelashes: distichiasis from opening of the meibomian gland - cockers, staffies, english bulldogs, mini LH dachshund. +/- irritation (rubbing, inc lacrimnation, ulceration)
Ectopic cilium more severe, grows through conj and directed straight at cornea - particularly in flat coated retrievers.
*Cornea: corneal lipidosis is a bilateral inherited condition, opacities in central cornea. Appear in early adulthood and not associated with visual disturbance. CKCS, huskies, shetland sheepdogs, rough collies, golden retrievers. Systemic dz can also cause this (hypoT4, hyperlipidaemia, Cushing’s disease)
Acquired inherited dz
Macular corneal dystrophy
Cornea:
*Macular corneal dystrophy (MCD) - described in Labrador retriever, mutation located to CHST6. DNA test available. Young to middle age dogs, bilateral symmetrical condition. White fluffy deposits in the anterior stroma –> corneal oedema and vascularisation. No discomfort but impaired vision, with ltd tx.
Acquired inherited dz
Cataract
Lens: cataract or luxations.
- Cataract - Causes - hereditary, post-inflammatory, traumatic, metabolic (DM), senile. Consider the location, age and breed. May be congenital or occur later in life
- DNA tests for a few breeds, some breeds have more than one form of inherited cataract.
- Boston terrier - early onset progressive form has a DNA test, second form which occurs later in life is of unknown inheritance
- Staffie - also has a second form of cataract as posterior polar subcapsular cataract, similar to that seen in labs, inheritance unknown
- Australian Shepherd Dog - HSF4 gene defective, posterior polar cataract, cortical extension, progressive. Young dogs. Dominant mode of inheritance but homozygotes will develop dz earlier.
- 5% of inherited cataracts are progressive
Acquired inherited dz
Luxation
Lens: cataract or luxations.
- Primary lens luxations - zonular rupture–> lens dislocation from normal position.
- JRT, Sealyham, Lancashire heeler, Mini bull terrier, fox terrier, border collie
- bilateral but one usually before the other
- look for signs of iridodonesis (iris wobble), strands of vitreous in AC, shallowing or deepening of AC.
- secondary glaucoma
- ADAMTS17 implicated (not in Shar pie(?) or Brittany Spaniel)
- Recessive but heterozygotes have been shown to have risk of developing dz (2-20% and older than homozygotes)
Acquired inherited dz
retina
PRA, RPED, CMR, CSNB, Cone Degeneration
Retina:
- Generalised progressive retinal atrophy - photoreceptor dysplasia or photoreceptor degeneration. Different forms affecting dogs at different ages. Secondary cataract formation. Typically in ECS and Labrador retriever there is poor night vision which progresses to loss of day vision over months to years in early middle age.
- hyperreflectivity and blood vessel attenuation followed by patchy depigmentation of the non tapetal fundus. Optic atrophy, total retinal degeneration.
- there is no tx.
- retinal pigment epithelial dystrophy - low serum vitamin E. Light brown lipopigment foci in the tapetal fundus, hyperreflective patches. Vascular attenuation and optic atrophy are variable. 2-3years at onset, variable effect on vision. Was common in Border Collies. Dietary vitamin E can halt progression. Cocker spaniel familial vit E deficiency.
- Canine multifocal retinopathy (CMR) - first in great pyrenees. Now Coton de Tulear and mastiffs plus others. Appears in first few months. Retinal degeneration is focal, serous retinal and RPE detachments. Lack of progression and vision maintained. Not currently on eye scheme. Multifocal grey, tan fundic patches which vary in size, found in the peripheral tapetal fundus, peripapillary region, inferior to optic disc.
- congenital station night blindness - Briard. Congenitally night blind, day vision is variable. Ophthalmoscopically normal until 2-3 years. Subtle hyperreflectivity followed by grey focal opacities within the tapetal fundus.
- cone degeneration - similar to above, early loss of cones at a few months results in total day blindness and normal night vision, seen in Alaskan Malamute. No fundal changes.
Control of inherited ocular disease
Eye Scheme and Testing
Tracking inherited eye disease:
1) examination and 2) testing
*Eye testing schemes in place since 1960. BV, KC and ISDS.
Panellists are certificate or diploma holders and assessment to be on panel.
Slit lamp, indirect and direct ophtho exam
Gonio is an additional test for PLA/PLD at risk breeds
US CERF scheme includes adnexa
ECVO scheme also includes adnexa
UK scheme adnexa is marked on form but since “breed related” rather than “inherited” it does not preclude breeding
*Genetic tests - do not replace Eye Scheme but work alongside it.
Advantages: can be tested at any age, carriers identified, human interpretation eliminated, one test for each conditions
Disadvantages: cost, limited conditions at present time, separate test for each mutation (dog can have a lesion from different mutation), no surveillance, open to abuse by unscrupulous breeders.
Inherited ocular dz of cats
Lids, Cornea, Glaucoma, Cataracts, Retina
Persian, Burmese, Siamese and Abyssinian mostly associated but not common
Eyelids:
- Congenital eyelid coloboma laterodorsally. DSHs, Persians and Burmese. PPM may also be seen, as well as occasional ONH coloboma.
- Dermoids at lateral canthus +/- cornea, Burmese
- Entropion - breed related in persians and exotics. Lower lids at medial canthus.
- NGP - Burmese mostly, but also DSH and Persian
Cornea:
*corneal sequestra - Persian and Burmese predisposed
Glaucoma:
*feline glaucoma is typically secondary. Siamese, Burmese and Persian have been reported with primary. A siamese colony has been shown to have PLA but does not appear to impact clinically
Cataracts:
*congenital and early onset sporadically reported.
Retina:
*rod-cone dysplasia/dystrophy/degeneration. Present with dilated pupils, poor night vision, hyperreflective tapetum, blood vessel attenuation. No secondary cataract unlike k9s.
Abyssinians - 2 forms of inherited PRA - one autosomal dominant rod-cone dysplasia (although cones die first) and one recessively inherited. Recessive form more a problem clinically and is also seen in Somali, Siamese and other similar breeds (rdAc deficiency)
