Introduction

• Abnormal development and growth of the retina resulting in retinal folds, rosettes and sometimes retinal detachment Retina: detachment.
• Cause: inherited in many dogs, acquired forms develop from insults experienced in utero or soon after birth.
• Signs: no clinical signs with mild forms; blindness Blindness with severe forms; one form is accompanied by skeletal chondrodysplasia.
• Diagnosis: signs, ophthalmoscopic examination.

Pathogenesis

Pathophysiology

Multifocal retinal dysplasia

• Separation of the neural retina from the underlying retinal pigment epithelium (RPE), probably via dysplastic development. 
• Retina is thrown up in folds.
• Folds may number a few to many.
• Primarily located in the dorsal tapetal retina, adjacent to the dorsal artery and vein.

Geographic retinal dysplasia

• Involve larger areas of the retina and are more rounded or patchy in shape. Duplication of retinal layers may occur, with formation of retinal rosettes.
• In working strains of the English springer spaniel the lesions are difficult to differentiate from post-inflammatory lesions.
• Cataract formation and intra-ocular hemorrhage may also be seen.

Total retinal detachment

• The retina is so dysplastic that is does not remain attached to the retinal pigmented epithelium.
• The neural retina is often seen lying within the vitreous humor.
• Hyaloid remnants may be a feature of this condition thus resulting in the subsequent formation of cataracts Cataract.
• Some dogs (eg Labrador retriever, German shepherd dog, Samoyed) also have skeletal chondrodysplasia Carpus: osteochondrodysplasia and are achondrodysplastic dwarfs.

Acquired dysplasia

• Infectious diseases canine adenovirus Canine adenovirus type 1 disease Canine adenovirus type 2 disease , canine herpesvirus Canine herpesvirus disease , canine parvovirus Parvovirus disease associated with CPV-1 Parvovirus disease associated with CPV-2.
• Vitamin A deficiency.
• Toxins.
• Radiation.
• Intrauterine trauma.

Inheritance patterns

• Inheritance patterns are variable.
• Many forms of multifocal dysplasia are suspected to be autosomal recessive traits.
• Skeletal and ocular abnormalities are believed to be carried by one gene, with recessive effects on the skeleton and incompletely dominant effects on the eye.
• Genetic mutations responsible for oculoskeletal dysplasia in the Labrador Retriever (drd1) and the Samoyed (drd2) have been identified, and genetic tests are available through Optigen (www.optigen.com/opt9_rdosd.html).
• In the Labrador Retriever and the Samoyed, the study concluded that heterozygotes may exhibit a milder ocular phenotype that ranges from vitreal strands and/or localized retinal dysplasia characterized by focal or multifocal folds, to large plaques of dysplastic retinal tissue. Heterozygotes may not have any skeletal abnormalities.

Diagnosis

Treatment

Outcomes