Lecture 18 4/10/25

Question 1

What is retinal dysplasia?

Answer 1

congenital maldevelopment and improper differentiation of the neurosensory retina; can be inherited or due to various in utero insults

Question 2

What are the retinal dysplasia classifications?

Answer 2

-multifocal; small, multiple areas
-geographic; large, single area
-total dysplasia with retinal detachment

Question 3

What is the history and signalment of multifocal retinal dysplasia?

Answer 3

-no clinical signs
-usually an incidental finding
-responsible breeders will check for inherited dz before breeding

Question 4

What is the ophthalmoscopic/histologic appearance of the retina in multifocal retinal dysplasia?

Answer 4

histology:
-retina is thrown into folds
-photoreceptors are disorganized into “rosettes”
ophthalmoscopy:
-linear, dot shaped, or vermiform streaks in tapetum or nontapetum
-green or gray lesions in tapetum +/- surrounding hyperreflectivity
-white lesions in nontapetum

Question 5

What are the etiologies of multifocal retinal dysplasia?

Answer 5

-inherited autosomal recessive disorder
-toxin or infection exposure in utero during retinal development

Question 6

What is the treatment for multifocal retinal dysplasia?

Answer 6

no treatment available or needed; lesions are non-progressive and do not cause noticeable visual impairment

Question 7

What are the characteristics of geographic retinal dysplasia?

Answer 7

-can have some degree of visual impairment if severe
-large coalescing areas of folds and rosettes seen on histopath.
-grey to brown discoloration in a horseshoe/circular pattern seen in tapetum
-lesions often immediately superior to optic disc
-hyporeflective discoloration is surrounded by hyperreflective areas
-inherited dz
-no treatment; not recommended to breed animals with dz

Question 8

What are the characteristics of total retinal dysplasia with detachment?

Answer 8

-animal is blind from birth
-can see a retinal detachment that is typically bullous in nature
-histopath. shows nonunion between RPE and neurosensory retina
-rotary nystagmus likely
-hemorrhage can occur with retinal tears
-inherited dz
-no treatment; not recommended to breed animals with dz

Question 9

What are the characteristics of oculoskeletal dysplasia syndrome?

Answer 9

-combination of chondrodysplasia and vision compromise
-can see various forms of retinal dysplasia and potentially retinal detachment
-caused by a genetic defect that leads to multiple congenital abnormalities and skeletal chondrodysplasia
-no treatment; not recommended to breed

Question 10

What is canine multifocal retinopathy?

Answer 10

-unusual early onset retinopathy that manifests as focal to multifocal bullous retinal detachments
-can progress until about 1 year of age and then remains static
-no clinical signs; often an incidental finding

Question 11

What are the ophthalmoscopic findings in canine multifocal retinopathy?

Answer 11

-multifocal gray to tan fundic patches that vary in size from pinpoint to optic disc-sized
-lesions often near optic disc and around major veins

Question 12

What is the etiology of canine multifocal retinopathy?

Answer 12

-inherited autosomal recessive mutation of the BEST1 gene
-suspected to be an RPE dysplasia that prevents RPE from absorbing fluid appropriately from subretinal space

Question 13

What is the treatment for canine multifocal retinopathy?

Answer 13

no treatment; lesions do not progress and do not cause notable visual impairment
-do not breed affected animals

Question 14

What is collie eye anomaly?

Answer 14

-inherited, congenital malformation of the fundus of collies
-primary defect is maldifferentiation of neural crest cells in posterior pole of eye
-affects both eyes
-usually no signs or significant history, but some affected animals are blind

Question 15

What is the first stage of collie eye anomaly?

Answer 15

*grade 1 and 2: choroidal dysplasia
-focal area of abnormal development of choroid temporal to optic disc
-basic lesion of the syndrome
-absence of tapetum and RPE pigment allows visualization of abnormal blood vessels, but vision is not impaired
-possible for animals to “go normal” after this stage and develop pigment; must examine by 12 weeks of age to diagnose

Question 16

What is the second stage of collie eye anomaly?

Answer 16

*grade 3: optic disc coloboma
-vision usually not significantly impaired
-can lead to severe vision changes if large area is affected

Question 17

What is the third stage of collie eye anomaly?

Answer 17

*grade 4: retinal detachment
-secondary to large area of retina and choroid being hypoplastic
-hypoplasticity leads to a tear
-occurs later in life

Question 18

What is the fourth stage of collie eye anomaly?

Answer 18

*grade 5: intraocular hemorrhage
-occurs secondary to retinal tear
-animal is blind at this point

Question 19

What is the etiology of collie eye anomaly?

Answer 19

inherited autosomal recessive disorder with multiple phenotypes

Question 20

What are other general features of collie eye anomaly?

Answer 20

-most dogs are affected with hypoplasia
-only about 5% of dogs have blinding manifestations
-thought to occur in 30 to 90% of US collies
-non-progressive, but lesions must build on each other
-beware of “go normal”

Question 21

What is the treatment for collie eye anomaly?

Answer 21

-no treatment
-counsel owner on managing blind dog if dog is blind
-do not breed homozygotes or clinically affected animals

Question 22

What are the characteristics of merle ocular dysgenesis?

Answer 22

-can occur in any breed with merle coloring
-not truly a retinal dz; mostly anterior segment dz that can affect retina

Question 23

What are the clinical signs of merle ocular dysgenesis?

Answer 23

-microphthalmia
-heterochromia
-dyscoria
-corectopia
-cataracts
-large equatorial staphylomas
-retinal detachments

Question 24

What is the etiology of merle ocular dysgenesis?

Answer 24

-inherited autosomal recessive disorder with incomplete penetrance
-affected animals are homozygous for merle gene and excessively white; do not breed together

Question 25

What is the treatment for merle ocular dysgenesis?

Answer 25

-treat uveitis secondary to cataracts with topical anti-inflammatories -treat hyphema secondary to retinal detachments with topical anti-inflammatories

Question 26

What are the general characteristics of retinal maturation?

Answer 26

-retinas are not fully developed at birth -retina reaches histologic maturation around 7 to 8 weeks -retina continues to mature by thinning and thickening until around 16 weeks

Question 27

What are the general characteristics of inherited retinal degenerations?

Answer 27

-may initially target rods, cones, or RPE -can be early or late onset photoreceptor degeneration -specific gene defect varies; numerous types -mostly affect dogs -age of onset and clinical progression varies significantly -almost all autosomal recessive -clinical signs, history, and appearance are similar amongst all disorders

Question 28

What is the main clinical sign in the early stages of IRDs?

Answer 28

nyctalopia: menace, dazzle, and PLRs are decreased in dim light due to rods being affected, but function normally in bright light

Question 29

What are the fundic changes that occur in IRDs?

Answer 29

-tapetal hyperreflectivity (retina thins and allows more light to hit tapetum) -depigmentation of non-tapetum -thinning of blood vessels/vascular attenuation -optic nerve atrophy -gray radial streaking in periphery of tapetum

Question 30

What is the definition of progressive retinal atrophy?

Answer 30

-group of inherited, acquired photoreceptor diseases -characterized by slowly progressive bilateral vision loss -due to loss of rod cell function first with subsequent progression to loss of cones and complete blindness

Question 31

What are the clinical signs/history of PRA?

Answer 31

-initial clinical sign is almost always nyctalopia -owner may notice increased "eye shine" -blindness progresses and generally becomes complete -cataract formation occurs as a secondary complication -PLRs may be normal early on, sluggish with progression, and absent in end stage dz -progression occurs over months to years

Question 32

How is PRA diagnosed?

Answer 32

-history -ophthalmic appearance -ERG -molecular genetic testing

Question 33

What is the treatment for PRA?

Answer 33

-no specific treatment -retina supplements may slow down progression -current work being done in gene vector treatments -counsel owner on maintenance of blind animal -do not breed affected animals

Question 34

What is SARDS?

Answer 34

-acquired disorder of retinal function characterized by sudden onset of complete blindness with initially normally appearing retinas -photoreceptor destruction occurs due to an unknown cause

Question 35

What are the clinical signs/history of SARDS?

Answer 35

-sudden onset of complete blindness -most common in middle-aged, overweight females of small breeds -PLRs typically maintained but may be slow and incomplete -no differences in dim vs bright light *appear cushingoid: -often PU/PD/PP -proteinuria -systemic hypertension -elevated ALP, AST, cholesterol, and abnormal stim. test

Question 36

What is the ophthalmoscopic appearance of SARDS?

Answer 36

retinas initially normal but develop retinal degeneration with time

Question 37

How is SARDS diagnosed?

Answer 37

-rule out other causes based on clinical signs and visual findings; normal fundic exam -ERG; will be flat -PLRs; often sluggish

Question 38

What is the treatment for SARDS?

Answer 38

-none established -can try immunosuppressives and steroids -counsel owner on maintenance of a blind animal