Canis ISSN: 2398-2942

Retina: detachment

Contributor(s): Dennis E Brooks, Rhea Morgan, Stephen Termote

Introduction

  • Separation of neurosensory retina (NR) from underlying retinal pigment epithelium (RPE). RPE is more tightly adherent to choroid and relatively weak link to photoreceptor (PR) layer.
  • Cause: inflammation, trauma, congenital, metabolic and vascular disease, toxicity, neoplasia, lens and vitreous disorders, glaucoma Glaucoma , intraocular surgery, retinal pathology (degeneration).
  • Signs: visual impairment (might be difficult to appreciate if RD is unilateral), anisocoria - pupil dilation.
  • Diagnosis: history, ophthalmic examination.
  • Clinical examination to help determine underlying cause, ultrasonography, hematology, biochemistry, blood pressure monitoring.
  • Treatment: directed at the underlying cause, laser retinopexy for partial detachments.
  • Prognosis: guarded to poor depending on duration, type, extent and cause of RD.

Pathogenesis

Etiology

  • The causes of retinal detachments are numerous and are related to the type of detachment present. Three basic forms of retinal detachment may occur in the dog.
  • Rhegmatogenous detachmentsarise with tears in the retina and progress from migration of liquefied vitreous into the subretinal space. Causes include:
    • Cataract formation, especially development of hypermature cataracts Cataract.
    • Glaucoma Glaucoma.
    • Trauma.
    • Intraocular surgery, especially with loss of vitreous.
    • Movement of the lens and/or vitreous.
    • Vitreal degeneration.
    • Inherited spontaneous giant tears in shih tzus and other dogs.
    • Secondary to generalized or central progressive retinal atrophy Retina: central progressive retinal atrophy (CPRA).
    • Secondary to senile cystic retinal
  • Detachments associated with congenital ocular defects(eg retinal dysplasia, collie eye anomaly, persistent hyperplastic primary vitreous, other multiple ocular defects, etc.) are usually inherited.
  • Acquired nonrhegmatogenous detachmentsdevelop when fluid or cells accumulate between the neurosensory retina and the RPE. They may be classified as transudative, hemorrhagic, or exudative.
  • Causes oftransudative detachments(serous subretinal fluid) include hyperviscosity syndrome, uremia, hypertension, other circulatory disorders, panuveitis, immune-mediated disorders (eg panuveitis of large breed dogs, VKH-like syndrome, systemic lupus erythematosus Systemic lupus erythematosus ), vitritis, trauma, Rocky Mountain spotted fever, borreliosis, granulomatous meningoencephalitis Granulomatous meningoencephalomyelitis , certain toxins, vasculitides, etc.
  • Causes ofhemorrhagic detachments(blood or bloody subretinal fluid) include coagulopathies, hypertension, hyperviscosity syndrome, polycythemia Polycythemia: primary Polycythemia: secondary , certain blood dyscrasias, immune hemolytic anemia Anemia: immune mediated hemolytic , post-transfusion therapy, ehrlichiosis, trauma, some neoplasms, etc.
  • Causes ofexudative detachments(infiltration of inflammatory or neoplastic cells subretinally) include blastomycosis Blastomycosis , coccidioidomycosis Coccidioidomycosis , histoplasmosis Histoplasmosis , cryptococcosis , protothecosis, brucellosis Brucellosis , mycobacteriosis, lymphosarcoma and many forms of metastatic tumors.

Pathophysiology

  • The neurosensory retina is only tightly attached to the back of the eye in only two locations, around the optic nerve and at the ora ciliaris.
  • The photoreceptors of the retina are attached to the RPE via an intercellular matrix substance, and a potential space exists between the photoreceptors and the RPE.
  • A retinal detachment may occur from loss of this matrix substance, dysplastic development of retina and RPE and effusion of fluid, blood or cells into this potential space.

Effusive nonrhegmatogenous RD

  • Disruption of the blood ocular barrier from inflammation, circulatory disorders, vascular disease, etc. causes infiltration and accumulation of exudate, transudate or blood in subretinal space. Focal, multifocal, quadrant, or complete detachments may occur.
  • With serous or transudative detachments the subretinal fluid is clear and the background is often visible. With hemorrhagic detachments, intraretinal, subretinal and even preretinal hemorrhages may be seen. With exudative detachments, pink white to gray effusion is seen in the subretinal space and focal chorioretinitis lesions may also be detected.

Rhegmatogenous RD (RRD)

  • Liquefied vitreous seeps into the subretinal space via a tear in the neurosensory retina. Abnormal vitreous may be crucial in development of these detachments. Degenerative changes of vitreous cause an increase in the liquid content (liquefaction, syneresis) and increase the risk of RRD development in the presence of a tear in NR.
  • Disruption of intimate vitreo-retinal and vitreal-lens interfaces (lens disease, trauma, cataract development, intraocular surgery) may also contribute.
  • Most retinal tears appear to happen at the vitreal base.

Tractional RD

  • Is a variant of the rhegmatogenous detachment.
  • Organization of inflammatory material (blood, fibrin) within the vitreous adheres to the NR, pulling the retina forward.
  • Traction itself can lead to retinal tearing and RRD.
  • Traction on NR from anterior displacement of the vitreous during intraocular surgery, lens luxation, or trauma may also cause loss of support of NR.

Progressive changes

  • Reabsorption or evacuation of subretinal fluid with repositioning of the NR against the RPE is crucial for reattachment.
  • Irreversible RD causes retinal degeneration with loss of vision depending on the duration and size of area affected.
  • RPE undergoes rapid reactive hypertrophy, pigmentation and hyperplasia, with possible migration of RPE into SR space within days.
  • Associated vascular pathology can cause ischemia and retinal necrosis. Cystic degeneration of overlying retina may occur.

Diagnosis

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Treatment

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Outcomes

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Andrew S E, Abrams K L, Brooks D E & Kubilis P S (1997) Clinical features of steroid responsive retinal detachments in 22 dogs. Vet Comp Ophthalmol (2), 82-87 VetMedResource.
  • Sullivan T C, Davidson M G, Nasisse M P & Glover T L (1997) Canine retinopexy - a determination of surgical landmarks, and a comparison of cryoapplication and diode laser methods. Vet Comp Ophthalmol (2), 89-95 VetMedResource.
  • Vainisi S J, Packo K H, (1995) Management of giant retinal tears in dogs. J Am Vet Med Assoc 206 (4), 491-5 PubMed.
  • Hendrix D V, Nasisse M P, Cowen P & Davidson M G (1993) Clinical signs, concurrent diseases and risk factors associated with retinal detachment in dogs. Prog Vet Comp Ophthalmol (3), 87-91 VetMedResource.
  • Christmas R E (1992) Common ocular problems of Shih Tzu dogs. Can Vet J 33 (6), 390-393 PubMed.

Other sources of information

  • Boeve M H & Stades F C (1999)diseases and surgery of the canine vitreous.In:Veterinary Ophthalmology3rd Ed: K N Gelatt. Lippincott, Williams & Wilkins, Baltimore, pp 857.
  • Narfstrom N & Ekesten B (1999)diseases of the canine ocular fundus.In:Veterinary Ophthalmology3rd Ed: K N Gelatt. Lippincott, Williams & Wilkins, Baltimore, pp 869.
  • Smith P J (1999)Surgery of the canine posterior segment.In:Veterinary Ophthalmology3rd Ed: K N Gelatt. Lippincott, Williams & Wilkins, Baltimore, pp 935.
  • Wheeler C A (1997)Disorders of the posterior segment.In: Morgan R V (ed)Handbook of Small Animal Practice. 3rd Ed. W B Saunders, Philadelphia, pp 1047-1058.
  • Gelatt K N & Gelatt J P (1995)Vitreoretinal surgery.In:Handbook of Small Animal Ocular SurgeryVol. 2. Corneal and Intraocular Procedures. 1st Ed. Pergamon, pp 211.

     


ADDED