Lecture 14: Retina and optic nerve pathology

A developmental disorder where the primary vitreous proliferates instead of regressing

Persistent hyperplastic primary vitreous (PHPV)

Signalment for PHPV

Dobbie and Staffordshire Terriers

CS of PHPV

Leukocoria (white pupil)

r/out with PHPV

Cataracts

Treatments for PHPV

Leave alone or surgical removal of cataract and/or fibrovascular tissue

PHPV diagnostics

Presurgical US to determine the extend and viability of the remaining hyaloid system prior to surgery

What it is: A developmental disorder where the primary vitreous proliferates instead of regressing

Signalment: Most common in Dobermans and Staffordshire Terriers

Clinical sign: Leukocoria (white pupil)

What to rule out: Cataracts

Treatment: Leave alone or surgical removal of cataract and/or fibrovascular tissue

Diagnostics: Presurgical ultrasound to determine the extent and viability of the remaining hyaloid system prior to surgery

PHPV

Degenerative disorder w/ calcium or lipid deposits suspended in the vitreous

Asteriod Hyalosis

Signalment of Asteriod Hyalosis

Aged animals

Other causes of asteriod hyalosis

Secondary to inflammation or as sequela or intraocular neoplasia

CS of asteriod hyalosis

Particles move upon the surface of eye but bounce back to the original position when eyes stop moving

Treatment of asteriod hyalosis

No considered a problem

What it is: Degenerative disorder associated with calcium or lipid deposits suspended in the vitreous

Signalment: Aged animals

Other causes: Can be seen secondary to inflammation or as a sequela of intraocular neoplasia

Clinical sign: Particles move upon movement of the eye but bounce back to the original position when eyes stop moving

Treatment: Not considered a problem

Asteroid Hyalosis

Bleeding into the vitreous

Vitreal Hemorrhage

Causes of vitreal hemorrhage

Hypertensive retinopathy, retinal detachments, clotting abnormalities, PHPV, fungal endophthalmitis, posterior uveitis, trauma (rare)

Treatment of vitreal hemorrhage

Topical and systemic corticosteriods

What it is: Bleeding into the vitreous

Causes: Hypertensive retinopathy, retinal detachments, clotting abnormalities, PHPV, fungal endophthalmitis, posterior uveitis

Rare cause: Trauma (unless perforation of the globe)

Treatment: Topical and systemic corticosteroids

Vitreal hemorrhage

What are the layers of the retina?

Retinal pigmented epithelium

Photoreceptors (rods and cones)

External limiting membrane

Outer nuclear layer

Outer plexiform layer

Inner nuclear layer

Inner plexiform layer

Ganglion cells

Nerve fiber layer

Internal limiting membrane

Who is holangiotic vascular pattern common in?

Dogs, cats, cattle, sheep, and pigs

Who is paurangiotic vascular pattern common in?

Horses

Who is merangiotic vascular pattern common in?

Rabbits

Who is anangiotic vascular common in?

Birds and reptiles

Congenital and inherited syndrome involving the posterior vascular and fibrous tunic of the eye, believed to be caused by abnormal mesodermal differentiation

Collie Eye Anomaly (CEA)

CEA signalment

Collies

CS of CEA:

Chorodial hypoplasia, coloboma, retinal detachment, retinal hemorrhage (interferes with vision)

What it is: Congenital and inherited syndrome involving the posterior vascular and fibrous tunic of the eye, believed to be caused by abnormal mesodermal differentiation

Signalment: Collies

Inheritance: Simple autosomal recessive trait

Clinical signs:

Choroidal hypoplasia

Coloboma

Retinal detachment

Retinal hemorrhage

Interference with vision: Retinal detachment and retinal hemorrhage

Progressive: Not progressive except that dogs born with coloboma of the disc are prone to developing retinal detachment and/or intraocular hemorrhage

Breeding: No affected animal should be bred

CEA

Progressive degeneration of the neuroepithelium, followed by the atrophy of the entire retina w/loss of layer organization

Progressive retinal atrophy (PRA)

Signalment of PRA

Every purebred dog

History with PRA

• Diminished vision first in subdued light

• Late afternoon and evening and nigh blindness (nyctalopia)

• Eyes appear “brighter” because tapetal reflectivity is increased and pupils tend to remain dilated

• The dog becomes blind

PE findings w/ PRA

• Pupils dilated

• Bilateral disease

• Increased tapetal reflectivity

• Attenuation of retinal blood vessels

• Optic disc becomes pale then white or gray-white

Treatment of PRA

None

What it is: progressive degeneration of the neuroepithelium, followed by atrophy of the entire retina with loss of layer organization

Inheritance: Autosomal recessive in almost all researched cases

Signalment: Most every purebred dog breed out there

History:

Diminished vision first in subdued light

Late afternoon and evening and night blindness (nyctalopia)

Loss of peripheral vision also occurs first

Eyes appear "brighter" because tapetal reflectivity is increased and pupils tend to remain dilated

As atrophy progresses, the dog becomes blind

Examination:

Pupils dilated—response to light slower than usual

Bilateral disease

Increased tapetal reflectivity

Attenuation of retinal blood vessels

Optic disc becomes pale then white or gray-white

Treatment: None

PRA

Sudden onset of blindness

Sudden acquired retinal degeneration (SARD)

Signalment of SARD

Typically overweight middle-aged female but seems to occur in any dog

CS of SARD

• Sudden onset of day and night blindness

• Absent or very sluggish and incomplete direct and indirect PLR

• History of PU/PD and potentially polyphagia

Treatments for SARD

No known treatment

Diagnostics of SARD

ERG (flat line as rods and cones, retina initially normal in appearance)

What it is: Sudden onset of blindness

Signalment: Typically in overweight, middle-aged female dogs but seems to occur in any dog

Clinical signs:

Sudden onset of day and night blindness

Absent or very sluggish and incomplete direct & indirect PLR's

History of polyuria/polydipsia and potentially polyphagia

Diagnostics:

ERG—flat line as rods and cones are both affected

Retina initially normal in appearance

Treatment: No known treatment

SARD

How do you differentiate PRA and SARD?

PRA is typically a disease of middle-aged dogs, but can be younger depending on the breed. SARD can occur in any dog

PRA is night blind first and day blind second. SARD is day and night blind

ERG: Even late in the disease process, animals with PRA should have some detectable activity on an ERG in contrast to SARDs that has no activity

Lesion in the area centralis

Feline Central Retinal Degeneration (FCRD)

CS of FCRD

No visual deficits in early stages, usually found incidentally

Lesions seen with FCRD

• Round cigar to foot ball lesion in the area centralis

• May be extended to become ellipsoid to complete band across the top of the disk

Cause of FCRD

Lack of taurine

What it is: Lesion in the area centralis

Clinical signs: No visual deficits in early stages, usually found incidentally on general physical

Lesions: Round to cigar to football shaped lesion in the area centralis

May extended to become ellipsoid to a complete band across the top of the disc

Area within the lesion will be hyperreflective caused by retinal degeneration

Lesions are graded based on their clinical appearance (1-5)

Cause: Lack of taurine

FCRD

Intraretinal separation that occurs at the embryologic separation of the RPE and the photoreceptors

Retinal detachment

Intraretinal separation that occurs at the embryologic separation of the RPE and the photoreceptors

Retinal detachment

Causes of retinal detachment

• Inflammatory/infection (Chorioretinitis w/subretinal exudate)

• Hypertension (secondary to serous subretinal effusion)

• Traction (secondary to vitreal hemorrhage or inflammation)

• Trauma (rare)

What it is: Intraretinal separation that occurs at the embryologic separation of the RPE and the photoreceptors

Causes:

Inflammatory/infectious: secondary to some causes of chorioretinitis with subretinal exudate

Hypertension: secondary to serous subretinal effusion

Idiopathic/immune-mediated/steroid responsive: rule out other causes first

Traction: secondary to vitreal hemorrhage or inflammation

Trauma: rare cause of retinal detachment in most domestic species unless the trauma is penetrating

Therapies:

Medical - treat medical condition

Surgical - treat surgically with retinopexy or more invasive procedures such as scleral buckle and/or intravitreal reattachment surgery

Retinal detachment

Bleeding in the retina

Retinal hemorrhage

Causes of retinal hemorrhage

Hypertension, thrombocytopenia, coagulopathy, radiation, hyperviscosity, senile, trauma (rare)

Inflammation of the optic nerve

Optic neuritis

CS of optic neuritis

• No PLRs

• Visual deficit

• Optic disc is swollen, irregular and retinal vessels may be dilated

• Optic disc may appear normal if the inflammation is the retrobulbar optic nerve only

Causes of optic neuritis

• Meningoencephalitis of unknown etiology (MUE)

• Granulomatous meningoencephalitis (GME)

• Isolated optic neuritis

• Canine distemper, cryptococcosis, blastomycosis, histoplasmosis, toxoplasmosis, toxic, trauma, GME or reticulosis, neoplasia (lymphosarcoma)

Diagnostics of optic neuritis

Complete neurologic exam, CBC/Chem/UA, MRI of orbit and brain, CSF tap ± CSF culture, electroretinogram, serum or CSF distemper titers, serology for other infectious causes of neuritis

Treatment of optic neuritis

• Based on cause if determined

• Prednisolone

• Azathiaprin

• Systemic antibiotics IF infection is found

• Chemotherapuetic agents or antifungal IF appropriate

Edema of the optic disc

Papilledema

CS of papilledema

• Not usually associated with a visual deficit

• PLR’s generally present

• Elevation of the disc surface above the retina

  • Swollen, puffy disc that is not inflammed

Causes of papilledema

• Some space occupying mass causing increased CSF pressure

• Neoplasia of the optic nerve

• Hemorrhage

• Neoplasia resulting in compression of the optic nerve fiber or other space occupying mass

• Hydrocephalus

How do you differentiate optic neuritis and papilledema

Optic Neuritis: Acute blindness, absent PLRs, swollen/inflamed/hemorrhagic optic nerve

Papilledema: Some vision, PLRs are present and may be normal, caused by increased CSF pressure

Compare and contrast active and inactive retinal/choroidal lesions

Active:

Hyporeflective area with indistinct borders

Vascular engorgement

Perivascular sheathing of vessels

Retinal hemorrhages

Retinal detachment

Progressive enlargement of lesion

Inactive:

Hyperreflectivity over the tapetum

Depigmentation or pigment hypertrophy in nontapetal fundus

Decreased vessel size

Sharply defined borders

A 5-year-old Doberman presents with a white pupil. Which of the following is the most likely diagnosis?

a) Progressive Retinal Atrophy (PRA)

b) Sudden Acquired Retinal Degeneration (SARD)

c) Persistent Hyperplastic Primary Vitreous (PHPV)

d) Asteroid Hyalosis

c) Persistent Hyperplastic Primary Vitreous (PHPV)

An aging dog presents with small, white particles suspended in the vitreous that bounce back to their original position after eye movement. This is most likely:

a) Vitreal hemorrhage

b) Asteroid hyalosis

c) Persistent hyperplastic primary vitreous

d) Retinal detachment

b) Asteroid hyalosis

Which of the following vascular patterns is seen in dogs?

a) Anangiotic

b) Merangiotic

c) Paurangiotic

d) Holangiotic

d) Holangiotic

A collie puppy is examined and found to have choroidal hypoplasia and a coloboma. This is most consistent with:

a) Progressive retinal atrophy

b) Collie eye anomaly

c) Sudden acquired retinal degeneration

d) Retinal dysplasia

b) Collie eye anomaly

Which of the following lesions associated with Collie Eye Anomaly (CEA) is most likely to interfere with vision?

a) Choroidal hypoplasia

b) Coloboma

c) Retinal detachment

d) Vermiform streaks

c) Retinal detachment

A dog presents with a history of night blindness that has progressed to day blindness. Examination reveals increased tapetal reflectivity and attenuated retinal vessels. The most likely diagnosis is:

a) Sudden acquired retinal degeneration

b) Progressive retinal atrophy

c) Retinal dysplasia

d) Optic neuritis

b) Progressive retinal atrophy

Which of the following is a typical clinical sign of Progressive Retinal Atrophy (PRA)?

a) Sudden onset of blindness

b) Decreased night vision

c) Normal pupillary light reflexes

d) Hyporeflective tapetum

b) Decreased night vision

A middle-aged, overweight female dog presents with sudden blindness. The owner reports that the dog has also been drinking and urinating more. On initial examination, the retina appears normal. What diagnostic test should be performed next?

a) Schirmer tear test

b) Electroretinogram (ERG)

c) Gonioscopy

d) Tonometry

b) Electroretinogram (ERG)

What finding on an electroretinogram (ERG) is most consistent with a diagnosis of Sudden Acquired Retinal Degeneration (SARD)?

a) Increased rod response

b) Increased cone response

c) Flat line

d) Normal waveform

c) Flat line

Feline central retinal degeneration (FCRD) is associated with a deficiency in which of the following nutrients?

a) Vitamin A

b) Taurine

c) Vitamin E

d) Thiamine

b) Taurine

A cat is diagnosed with FCRD. What lesion is expected on fundic exam?

a) A round to cigar-shaped lesion in the area centralis

b) Retinal detachment

c) Optic nerve swelling

d) Vitreal hemorrhage

a) A round to cigar-shaped lesion in the area centralis

What is the most common cause of a serous retinal detachment with intraretinal and/or vitreal hemorrhage?

a) Trauma

b) Hypertension

c) Retinal dysplasia

d) Collie eye anomaly

b) Hypertension

Which of the following is a potential therapy for retinal detachment?

a) Topical corticosteroids only

b) Retinopexy

c) Enucleation

d) Dietary modification

b) Retinopexy

A dog presents with retinal hemorrhages. Which of the following is the least likely cause?

a) Hypertension

b) Thrombocytopenia

c) Trauma

d) Hyperviscosity

c) Trauma

.

A dog presents with acute blindness, absent pupillary light reflexes, and a swollen optic disc. The most likely diagnosis is:

a) Progressive retinal atrophy

b) Optic neuritis

c) Papilledema

d) Sudden acquired retinal degeneration

b) Optic neuritis

Which diagnostic test can be used to differentiate optic neuritis from sudden acquired retinal degeneration (SARD)?

a) Schirmer tear test

b) Electroretinogram (ERG)

c) Gonioscopy

d) Tonometry

b) Electroretinogram (ERG)

What is a common cause of papilledema?

a) Hypertension

b) Increased cerebrospinal fluid pressure

c) Retinal detachment

d) Taurine deficiency

b) Increased cerebrospinal fluid pressure

How does papilledema typically affect vision and pupillary light reflexes (PLRs) in the early stages?

a) Causes acute blindness and absent PLRs

b) Does not usually cause a visual deficit, and PLRs are generally present

c) Causes night blindness and sluggish PLRs

d) Causes day blindness and normal PLRs

b) Does not usually cause a visual deficit, and PLRs are generally present

An ophthalmic exam reveals a retinal lesion with indistinct borders. The area is hyporeflective. This lesion is best described as:

a) Active

b) Inactive

c) Scarrred

d) Normal

a) Active

Which finding is most consistent with an inactive retinal lesion?

a) Hyporeflectivity

b) Indistinct borders

c) Hyperreflectivity

d) Retinal hemorrhage

c) Hyperreflectivity