Retinal Detachment
Retinal Detachment is 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 or vitreal degeneration, 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 or lens 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 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,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
Species
Dog and cat
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-Tzu, Boston terrier, Italian greyhound, Chihuahua—appear to be predisposed to spontaneous rhegmatogenous detachments owing to abnormal liquefied vitreous.
Dogs with merle coat color; Australian shepherd, Shetland sheepdog, harlequin Great Dane, collie.
Breeds that may have severe retinal dysplasia: springer spaniel, Labrador, Bedlington terrier.
Breeds with serous retinopathy (also known as RPE dysplasia, canine multifocal retinopathy): Great Pyrenees, mastiff, Coton de Tulear.
Mean Age and Range
Depends on cause.
Older patients—cataracts and systemic diseases (e.g., hypertension, neoplasia, and immune-mediated disease).
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” 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.
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 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
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—traumatic probably never occurs.
Penetrating injury or foreign body.
Severe blunt trauma with inflammation or hemorrhage.
Surgical trauma—may contribute to retinal tearing.
Toxic—idiosyncratic reactions to drugs (e.g., trimethoprim-sulfa, ethyelene glycol 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 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.
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.
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.
MEDICATIONS
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.
FOLLOW-UP
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.
MISCELLANEOUS
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
Visit your veterinarian as early recognition, diagnosis, and treatment are essential.