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.

Systems Affected

• Nervous-dogs with GME will often develop neurologic symptoms.
• Ophthalmic-retina,uvea.
• May be manifestation of a systemic disease or neoplasia.

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

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” 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 chapter, 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 unless severe vitreal degeneration is present in breed known to have predisposition e.g., Shih Tzu.

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.

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 or PCR 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; 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; normal mean arterial pressure in dogs and cats usually <160 mmHg.
• 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 choroid.
• May note masses or subretinal exudate or etiologic infectious organism.
• Chronic-results in retinal atrophy and a tombstone appearance to the RPE.

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.

Client Education

• Explain that RD may be a sign of systemic disease, so diagnostic testing is important.
• Inform client that RD associated with vitreal degeneration, lens luxation or cataract surgery has a bilateral potential, minimize head shaking.
• Inform client that with short-duration RD return of vision may occur if the underlying cause is treated.
• Advise client that blind pets 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. May prevent detachment in predisposed fellow eye.

Drug(s) Of Choice

• Depends on underlying systemic cause, which should be identified and treated.
• 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. Propranolol and/or enalapril (0.25–0.5 mg/kg q12–24h) or benazapril (0.25–0.5 mg/kg q24h) for cats with hypertension not responsive to amlodipine alone. Calcium channel blockers 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.
• Other immunosuppressive drugs may be needed in some immune-mediated RD if prednisone not effective long term at safe dose, i.e., uveodermatologic syndrome.
• Azathioprine: dogs, 2 mg/kg PO q24h initially, then 0.5–1 mg/kg q48h; to control inflammation.
• Oral cyclosporine: dogs, 5 mg/kg/day then taper.
• Leflunomide, mycophenolate: also can be used if prednisone is not effective at a safe dose; consult with internist.

Patient Monitoring

• Immunosuppressive drugs such as azathioprine-obtain an initial CBC, chemistry panel, then every 1–2 weeks to monthly (depending on which medication) to monitor for bone marrow suppression, liver, renal, 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
• Vision may return if the underlying cause is removed and reattachment occurs..
• Blindness-may develop in days to weeks even if reattachment occurs (more likely and rapid with exudative than with serous detachments).
• Focal or multifocal chorioretinitis-does not markedly impair vision; will leave scars.

Associated Conditions

• Exudative-systemic disease
• Cataracts
• Trauma
• Vitreous abnormalities
• CNS signs 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

Client Education Handout Available Online