Retina: detachment

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• Complete or partial detachment of the neurosensory retina (nsr) from the retinal pigment epithelium (rpe). Usually bilateral.
• Cause: commonly caused by hypertension in the elderly cat. Also inflammation, trauma, neoplasia, hyperviscosity syndromes, toxicity (ethylene glycol).
• Signs: any or all of: visual loss/compromise (often sudden onset may be difficult to appreciate if retinal detachment is unilateral), hyphema, vitreal hemorrhage, dilated pupil, leucocoria (white pupil).
• Diagnosis: ophthalmoscopy reveals detachments and hemorrhage.
• Treatment: depends on cause - treat primary cause and symptomatic management.
• Prognosis: previously considered to be poor unless treatment instituted very early; degeneration of feline retina is rapid following detachment; more recently treatment of hypertensive detachments with amlodipine has resulted in recovery of sight in a significant proportion of animals.

• Most commonly sudden visual loss and/or intra-ocular hemorrhage (note that sudden visual loss accompanies detachment in the second eye where the first may be chronically blind).

• Dilated pupils.

• Leucocoria.

• Elderly cat.

• Moderate.
• Treatment usually life-long.

• Causes of hypertension:
  • Primary or essential if it exists in the cat.
  • Renal disease .
  • Hyperthyroidism .
  • Cardiac disease .
  • Diabetes mellitus .
  • Anemia (chronic) .
  • Megestrol acetate .
  • Iatrogenic hyperadrenocorticism .
  • Primary aldosteronism.
• Inflammation (see chorioretinitis ).
• Neoplasia.
• Hyperviscosity syndromes:
  • Hyperproteinemia .
  • Polycythemia vera .
• Ethylene glycol toxicity .

• Primary (spontaneous or traumatic) - secondary to systemic or ocular disease. Partial (focal or multifocal) - total.
• Hypertension vascular pathology incompetence and leakage of plasma and fibrinogen.
• Fluid accumulation results in extensive bullous detachment.
• Inflammation: inflammatory exudates localize in the potential space between neurosensory retina and retinal pigment epithelium (junction of primordial inner and outer layers of optic cup) detachments.
• Neoplasia: tumor growth may infiltrate the sub-retinal space a solid, usually circumscribed, detachment.
• Hyperviscosity syndromes: hyperproteinemia and polycythemia vera detachments by causing vascular pathology as above.

• Hypertension affects choriocapillaris first, because lacks autoregulatory control of blood flow cf. retinal vessels focal hazy opacities (reflecting leakage of plasma and fibrinogen) focal intra-retinal hemorrhage if further damage to vessels occurs ('dot and blot' hemorrhages) ischemic damage to the retinal pigment epithelium (rpe) (very metabolically active cells) sub-retinal exudation and detachment.
• Detachment first flat, then multiple bullae (cobblestone appearance), then total.
• Uncontrolled hypertension intra-vitreal hemorrhage from retinal vessels, possible hyphema as bleeding occurs from iris vessels. Intra-ocular hemorrhage may secondary glaucoma .
• Hyperviscosity syndromes sludging of blood in vessels hypoxic damage pathophysiology as for hypertension.

• Usually 'sudden' in onset, ie sudden objective signs but this relates to the second eye affected - the first may have a chronically detached (and thus permanently damaged) retina.
• Early signs may be picked up on examination before objective signs, eg at routine annual vaccination (a good reason for ophthalmic examination at every routine examination in the older cat).

• Sudden onset blindness.
• Intra-ocular hemorrhage.
• Dilated pupils.

• Sudden onset vision loss/compromise.

• Intra-ocular hemorrhage.
• Bilateral dilated pupils.
• Signs compatible with conditions causing secondary hypertension (see etiology).

• Dilated pupils - usually show some response to light, though sluggish and incomplete.
• Direct and consensual PLR may be present.
• Intra-ocular hemorrhage - hyphema may render any further examination impossible.

• Detached retina may be seen ballooning forwards .
• If retina becomes attached to posterior lens capsule may result in leucocoria (white pupil).
• Full clinical examination may reveal underlying condition.

• See ophthalmoscopy . May reveal nature/extent of detachment and presence of intra-retinal or intra-vitreal hemorrhage.

2-D Ultrasonography

• To check for kidney, cardiac or other primary condition causing secondary hypertension.

Other

• Sphygmomanometry - non-invasive indirect methods for measurement of blood pressure.
• Either Doppler or oscillometric methods.
• Systolic blood pressure >180 mmHg probably pathological but consider stress level!

• History and clinical signs.
• Ophthalmoscopy.
• Ultrasound.

• Sphygmomanometry.

• Chorioretinitis .
• FCRD (feline central retinal degeneration or taurine deficiency retinopathy).
• Hereditary retinopathies .
• Glaucoma .
• Trauma.

• Calcium channel blockers (amlodipine besylate 0.625 mg SID PO (optimal regime), diltiazem hydrochloride 1.75-2.4 mg/kg BID-TID PO) or ACE inhibitors (benazepril 0.25 mg/kg SID PO, enalapril maleate 0.25-0.5 mg/kg SID-BID PO).
   Amlodipine and benazepril may be used together to effect greater systolic BP reduction.
• Diuretics, eg furosemide 1-2 mg/kg SID PO.
• Low sodium diet.
• Cage rest.

• Specific treatment for underlying cause, if identified.
• Combination of all above - aim is to reduce cardiac output.
  • Diuretics and low sodium diet reduce extracellular fluid volume.
  • Beta-adrenoreceptor blockers (propranolol 0.1-0.2 mg/kg BID PO) reduce heart rate.
  • Alpha-1 blockers (prazosin 0.25-1.0 mg/kg SID-TID PO), calcium channel blockers and ACE inhibitors reduce peripheral resistance.

• Reduction in systolic blood pressure.
• Retinal re-attachment.
• No new hemorrhages.
• Regaining vision/pupillary light responses (PLR).

• Monthly routine checks recommended.

• Good if early diagnosis and primary condition amenable to treatment.
• Poor if advanced and primary condition not amenable to treatment, eg decompensated renal failure .

• Recent references from PubMed.
• Littman M P (1994) Spontaneous systemic hypertension in 24 cats. JVIM 8, 79-86.
• Sansom J et al (1994) Ocular disease associated with hypertension in cats. JSAP 35, 604-611.

• Petersen-Jones S & Crispin S (2002) BSAVA Manual of Small Animal Ophthalmology. 2nd edn. British Small Animal Veterinary Association. ISBN 0 905214 54 4

• Dr Dennis E Brooks DVM PhD DipACVO, College of Veterinary Medicine, 2015 SW 16th Ave, University of Florida, PO Box 100126, Gainesville, FL 32610-0126, USA.
• David Williams MA Vet MB PhD CertVOphthal MRCVS, Department of Clinical Veterinary Medicine, Madingley Road, Cambridge CB3 0ES, UK.

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