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Retina: detachment

ISSN 2398-2977

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Podcast: Retina: detachment

Introduction

  • The neurosensory retina (NSR) is closely related and attached by a glycosaminoglycan (GAG) intercellular matrix to the retinal pigment epithelium (RPE).
  • Detachment of the NSR from the RPE occurs through the intraretinal space with disruption of the matrix by:
    EitherImpaired synthesis.
    OrHydration of the matrix by choroidal derived transudates/exudates
    OrDissection of vitreous into this space.
  • Points adjacent to the optic disk and pars ciliaris retinae are particularly firmly attached and are rarely separated.

Pathogenesis

Congenital
  • May occur as an isolated lesion or in association with multiple congenital abnormalities eg microphthalmia   Eyeball: microphthalmos  , lens cataracts   Cataract: congenital  or luxations   Lens: subluxation / luxation  .
  • The detached retina is often dysplastic histologically.
  • Probably represents congenital non-attachment of the NSR to the RPE due to incomplete invagination of the optic vesicle.
  • Etiologic factors include: developmental disorders eg differing growth rates of the developing NSR and RPE, or ?heritable.

Acquired

Post-inflammatory

  • Retinal detachment may occur in latter stages of uveitis   Uveitis: anterior - overview  or chorioretinitis as a result of
    EitherAccumulation of exudative fluid and inflammatory cells between the RPE and NSR.
    OrSecondary to the formation of vitreoretinal adhesions and traction bands.
    OrExudative optic neuritis   Optic nerve: neuritis  with traction bands.
  • May occur months or years after initial uveitis.

Rhegmatogenous

  • Usually complete detachments or giant retinal tears due to the migration of vitreous through a defect in the NSR (usually traumatically acquired).

Traumatic

  • Rarely skull or ocular trauma may cause detachment (usually traumatic optic neuropathy   Optic nerve: neuropathy - trauma  , either by physical detachment at the time of trauma or subsequently (more usual) due to vitreoretinal hemorrhage or posterior segment inflammatory changes.

Post-surgical complication of cataract surgery

  • Prolapse of vitreous.

Idiopathic

  • Older horses with vitreal degenerative processes.

Diagnosis

Congenital

History

  • Young foals.
  • Any breed but more common in Standardbreds/Thoroughbreds
  • Apprehensive behavior and collisions with objects.
  • Visual deficits.

Clinical signs

  • Unilateral or bilateral (more common).
  • Detachment is usually complete and will cause blindness in affected eye(s).
  • Bilateral cases have a searching nystagmus.
  • Pupils are dilated and fixed.

Ancillary aids

  • Direct ophthalmoscopy  Eye: examination - direct ophthalmoscopy - close  :
    • Retina appears as a grey veil, often folded, projecting vitread and attached at the optic disk, which is frequently obscured by the dorsal retina falling into the ventral vitreous   Retina: detachment 01    Retina: detachment 02  ; hyper-reflective tapetum.
    • Other congenital abnormalities may include: luxated lens   Lens: subluxation / luxation  , cataracts   Cataract: overview  , microphthalmia   Eyeball: microphthalmos  , corneal dystrophies, retinal dysplasia, aniridia, iris colobomas   Iris: coloboma  , etc which can affect the visualization of the retina.

Acquired

History

  • Any age animal.
  • Previous ocular or skull trauma.
  • Previous or active uveitis (more common) - sometimes months/years earlier.
  • Cataract surgery.
  • Visual deficits.

Clinical signs

  • Unilateral (more common) or bilateral.
  • Partial detachments are common initially but usually progress to complete.
  • Partial detachments   →   specific visual field deficits.
  • Complete detachment   →   blindness and fixed dilated pupils   Eye: retinal detachment - acute uveitis  .
  • If inflammatory in origin: evidence of anterior uveitis   Uveitis: anterior - overview  , chorioretiniti, optic neuritis   Optic nerve: neuritis  with traction bands, vitritis   Vitreous: vitritis (vitreous haze)  .
  • Other evidence of skull/ocular trauma may be present.

Ancillary aids

  • Direct ophthalmoscopy:
    • Detachment may appear as 'sunburst-like', multiple radiating gray retinal veils or striae, attached near the disk (partial) or progress to complete detachment or giant retinal tear as seen in congenital form.

    Vitreoretinal adhesions and detachments may be present obscuring view of retina.

Ancillary aids

Treatment

Congenital
  • No effective treatment.

Acquired

  • Treat primary condition   Uveitis: anterior - overview  .
  • Early recognition and treatment is essential - may restrict the detachment area.
  • Often unsuccessful - detachment progresses.

Prognosis

Congenital
  • Grave - especially if bilateral.

Acquired

  • Poor - especially if other ocular pathology is present.
  • Recurrence of uveitis and progression to complete detachment/blindness is common.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Verhulst D, Barnett K C & Mayhew I G (2001) Equine motor neuron disease and retinal degeneration. Equine Vet Educ (2), 84-87.
  • Rebhun W C (1992) Retinal and optic nerve diseasesVet Clin North Am Equine Pract (3), 587-608 PubMed.