R: Retinal Detachment

Retinal Detachment

BASICS

DEFINITION

Any separation of the neural retina from the retinal pigment epithelium.

PATHOPHYSIOLOGY

Subretinal space—a potential space between the RPE and neural retina in which fluid or exudates accumulate.
Characterized by its etiopathogenesis—one or a combination of rhegmatogenous (retinal tear), subretinal exudation, or traction.

Rhegmatogenous

A tear or hole in the retina that may be related to age, cataracts, traction from inflammatory debris, trauma, or retinal degeneration. Vitreous fluid moves into the subretinal space, which results in detachment. Probably the predominant type that occurs in association with cataracts and after cataract surgery. Requires some vitreous abnormality (e.g., liquefaction, traction).

Exudative

Fluid accumulates in the subretinal space because of breakdown of the blood-retinal barrier.
Subretinal fluid—may be serous, hemorrhagic, or exudative (e.g., granulomatous in patients with blastomycosis).
Hematogenous/systemic pathogenetic factors—common.
Vasculitis, hypertension, and hyperviscosity—may cause serous detachment with or without hemorrhage.

Traction

Usually by fibrous or fibrovascular tissue; detaches retina underlying RPE and/or may cause retina hole or tear.
May be associated with trauma, intraocular foreign bodies, or any cause of severe vitreal inflammation.

SYSTEMS AFFECTED

Nervous—dogs with GME will often develop neurologic symptoms.
Ophthalmic—retina.
May be manifestation of a systemic disease.

GENETICS

Depends on cause—dogs with hereditary cataracts or lens luxations may develop rhegmatogenous detachment. Some breeds may have retinal tears and detachment from primary vitreous abnormalities.

INCIDENCE/PREVALENCE

Exudative—most common in dogs and cats.
Rhegmatogenous—more common in dogs because of the greater prevalence of cataracts and cataract surgery.

SIGNALMENT

Species

Dogs and cats

Breed Predilections

Depends on cause.
Terrier breeds—predisposed to primary lens luxation, which may contribute to retinal tear and detachment with or without surgery.
Breeds that develop cataracts.
Shih-tzus, Boston terriers, Italian greyhounds—appear to be predisposed to spontaneous rhegmatogenous detachments owing to abnormal liquefied vitreous.
Dogs with merle coat color: Australian shepherds, Shetland Sheepdogs, harlequin Great Danes, collies.
Breeds that may have severe retinal dysplasia: springer spaniels, Labradors, Bedlington terriers.
Breeds with serous retinopathy (also known as RPE dysplasia, canine multifocal retinopathy): Great Pyrenees, mastiffs, Coton de Tulear.

Mean Age and Range

Depends on cause.
Older patients—cataracts and systemic diseases (e.g., hypertension, neoplasia, and immune-mediated disease) are often age related.
Young dogs: affected with severe retinal dysplasia, canine multifocal retinopathy.

SIGNS

Blindness or reduced vision in affected eye.
Dilated pupil with slow or no PLR. PLR may be near normal if detachment is acute.
Blood vessels or a “membrane” (which is the retina) may be observed easily through the pupil just behind the lens.
Vitreous abnormalities—floaters, hemorrhage, or syneresis (liquefaction); common.
Interruption or alteration of the course of blood vessels owing to retinal elevation.
With clear subretinal fluid—vessels may cast shadows.
With exudative fluid or blood, tapetum may not be visible.
Other symptoms will depend on any underlying systemic diseases.
See Chorioretinitis for signs of inflammation. Canine multifocal retinopathy: multifocal gray to tan elevated lesions (focal detachments) of various size. Starts around 11 weeks, progresses with time.

CAUSES

Bilateral—suggests a systemic problem led to disruption of blood-retinal barrier.

Degenerative

End-stage progressive retinal degeneration—may lead to retinal hole formation and detachment: see Retinal Degeneration.

Anomalous

Colobomas—collie eye anomaly: abnormal retina around colobomatous optic nerve or large choroidal staphylomas may lead to rhegmatogenous type detachments; border collies, Australian shepherds, and other breeds in which dogs have merle coats (merle ocular dysgenesis).
Multiple ocular anomalies—Akitas, any breed.
Severe retinal dysplasia—oculoskeletal dysplasia in Labrador retrievers and Samoyeds; retinal dysplasia; English springer spaniels and Bedlington terriers.
Canine multifocal retinopathy—suspect RPE dysplasia; Great Pyrenees, mastiffs, Coton de Tulear.

Metabolic

Hypothyroidism.
Hyperviscosity.
Polycythemia.
Hypoxia with hemorrhagic complications.
Dogs—systemic hypertension (any cause such as renal failure or pheochromocytoma), hypothyroidism, hypercholesterolemia, and hyperproteinemia (e.g., with multiple myeloma).
Cats—most often caused by systemic hypertension either as a primary condition or secondary to renal failure or hyperthyroidism. Multiple myeloma, adrenal tumors also can cause RD due to hyperviscosity or hypertension.

Neoplastic

Any primary or metastatic neoplasm.
Commonly associated with multiple myeloma, lymphoma, granulomatous meningoencephalitis, and intraocular masses—ciliary body adenocarcinoma or melanoma.
Hypertension secondary to adrenal tumors like pheochromocytoma; rare.

Infectious

Infectious retinitis or chorioretinitis—may cause focal or diffuse detachment.
Infection may extend from or to the CNS.
See Chorioretinitis.

Immune Mediated/Inflammatory

Immune complex disease—may cause vasculitis or inflammation resulting in exudative detachment.
Dogs—SLE; uveodermatologic syndrome.
Cats—periarteritis nodosa; SLE.

Idiopathic

If all other causes are ruled out, including retinal tears.
Idiopathic steroid-responsive detachment—reported in giant-breed dogs but may occur in any breed.

Trauma and Toxic

Bilateral—probably never occurs.
Penetrating injury or foreign body that causes retinal tears or intraocular hemorrhage—may cause partial or complete detachment.
Severe blunt trauma with inflammation or hemorrhage.
Surgical trauma—may contribute to retinal tearing.
Toxic—idiosyncratic reactions to drugs (e.g., trimethoprim-sulfa in dogs, griseofulvin in cats).

RISK FACTORS

Systemic hypertension.
Old age: retinal thinning, severe vitreal degeneration.
Hypermature cataracts.
Luxated lenses.
Lens extraction.
Hereditary: young dogs that have more severe retinal dysplasia and/or multiple ocular anomalies.

DIAGNOSIS

DIFFERENTIAL DIAGNOSIS

Blindness or impaired vision—optic neuritis; glaucoma; cataracts; progressive retinal atrophy; SARDS (see Retinal Degeneration); CNS disease.
Dilated pupil with slow or absent pupillary light reflexes—glaucoma; oculomotor nerve lesion; optic neuritis; progressive retinal atrophy; SARDS.
Membrane or vessels associated with or behind lens—persistent tunica vasculosa lentis; persistent pupillary membranes; fibrovascular membrane secondary to intraocular neoplasia or inflammation.

CBC/BIOCHEMISTRY/URINALYSIS

Typically normal if the problem is confined to the eye.
Abnormalities consistent with an associated systemic disease process.

OTHER LABORATORY TESTS

Depends on suspected systemic problem.
Protein electrophoresis.
Documentation of Bence-Jones protein in urine.
Coagulation profile.
Bacterial culture of ocular or body fluids.
Thyroid hormone measurement.
Serologic testing for infectious diseases—see Chorioretinitis.

IMAGING

Thoracic radiograph, abdominal x-rays, and abdominal ultrasound—search for lymphadenopathy, primary neoplasia, metastatic disease, or infiltrates consistent with infectious agents.
Radiographs of the spine—may reveal bony changes consistent with multiple myeloma.
Ocular ultrasound—identify retinal detachments, intraocular masses, and sometimes lens luxations; helpful if the ocular media is not clear.
Cardiac ultrasound—cats with hypertensive retinopathy.

DIAGNOSTIC PROCEDURES

Ophthalmic examination.
Single or repeated blood pressure measurement—may reveal hypertension; mean arterial pressure in dogs and cats usually < 160 mm Hg.
CSF tap—indicated with signs of CNS disease or optic neuritis.
Vitreocentesis or subretinal fluid aspirate—may be performed if other diagnostic tests failed to yield a cause and an infectious agent or neoplasia is suspected; may aggravate the inflammation or induce hemorrhage.

PATHOLOGIC FINDINGS

Retina separated from the RPE and underlying choroids.
May note masses or subretinal exudate or etiologic infectious organism.
Chronic—results in retinal atrophy and a tombstone appearance to the RPE.

TREATMENT

APPROPRIATE HEALTH CARE

Depends on the physical condition of the patient.
Usually outpatient.
Acute blindness—vision may be restored if the underlying cause is rapidly identified and treated; make every attempt to determine the cause.
Degeneration occurs rapidly—provide therapy as soon as possible after diagnosis.
Rhegmatogenous—an ophthalmologist may be able to provide surgical reattachment.

CLIENT EDUCATION

Explain that RD may be a sign of systemic disease, so diagnostic testing is important.
Inform client that RD associated with lens luxation or cataract surgery has a bilateral potential.
Inform client that with short-duration RD return of vision may occur if the underlying cause is treated.
Advise client that blind pets, especially cats, can adapt remarkably well and live a good-quality life (see Retinal Degeneration).

SURGICAL CONSIDERATIONS

Rhegmatogenous—may be surgically repaired by an ophthalmologist.
Laser retinopexy—may reverse detachments associated with optic disk colobomas with collie eye anomaly; may stabilize partial/small detachments.

MEDICATIONS

DRUG(S) OF CHOICE

Depends on underlying systemic causes, which should be identified and treated appropriately.
Systemic prednisone 2 mg/kg divided q12h for 3–10 days, then taper; if systemic mycosis is ruled out and the detachment is believed to be immune mediated; may facilitate retinal reattachment; for immune-mediated disease, taper medications very slowly over months.
Anti-inflammatory doses of prednisone 0.5 mg/kg, then taper; may be useful for exudative detachments of an infectious nature as long as the underlying disease is being definitively treated.
Antihypertensive agents—amlodipine 0.5–1 mg/kg PO q24h in dogs; cats 0.625–1.25 mg. Others such as propranolol may be used if amlodipine fails to control hypertension. Enalapril (0.25–0.5 q12–q24h) or benazapril (0.25–0.5 mg/kg q24h) for cats with hypertension not responsive to amlodipine alone; may be important in cats that have renal failure and proteinuria. Consult with internist. See Renal Failure chapters.

CONTRAINDICATIONS

Systemic corticosteroids—do not use unless systemic mycosis is ruled out or is being definitively treated.

ALTERNATIVE DRUG(S)

Chemotherapeutic agents—suggested for treatment of neoplastic conditions.
Azathioprine: dogs, 2 mg/kg PO q24h initially, then 0.5–1 mg/kg q48h; to control inflammation; may be required in addition to steroids for uveodermatologic syndrome or idiopathic immune-mediated detachment.
Oral cyclosporine: dogs, 5 mg/kg/day may be effective in some immune-mediated RD; i.e., uveodermatologic syndrome.

FOLLOW-UP

PATIENT MONITORING

Azathioprine—obtain an initial CBC, then every 1–2 weeks for the first 1–3 months; monitor every 1–2 months for bone marrow suppression (if noted, reduce the dose or discontinue). Initial and follow-up chemistry panels to evaluate for liver or pancreas toxicity.
Monitor blood pressure in hypertensive cases.

POSSIBLE COMPLICATIONS

Permanent blindness.
Cataracts.
Glaucoma.
Chronic ocular pain.
Death if secondary to a systemic disease/neoplastic process.

EXPECTED COURSE AND PROGNOSIS

Prognosis for vision with complete detachment—guarded. The exception is hypertensive retinopathy that is diagnosed and treated promptly.
Blindness—may develop in days to weeks even if reattachment occurs (more likely with exudative than with serous detachments).
Vision may return if the underlying cause is removed and reattachment occurs.
Focal or multifocal chorioretinitis—does not markedly impair vision; will leave scars.

MISCELLANEOUS

ASSOCIATED CONDITIONS

Exudative—systemic disease.
Cataracts.
Trauma.
Traction and/or rhegmatogenous—vitreal hemorrhage or inflammation.
CNS signs in dogs with GME or systemic disease affecting CNS.

ABBREVIATIONS

CNS = central nervous system
CSF = cerebrospinal fluid
GME = granulomatous meningoencephalomyelitis
PLR = pupillary light reflex
RD = retinal detachment
RPE = retinal pigment epithelium
SARDS = sudden acquired retinal degeneration syndrome
SLE = systemic lupus erythematosus