Persistent hyperplastic primary vitreous
Persistent tunica vasculosa lentis and primary vitreous is an autosomal-recessive congenital ocular disease of dogs characterized by the presence of a fibrovascular plaque on the posterior aspect of the lens.
This condition develops as a consequence of the hyaloid-tunica vasculosa lentis system (the normally transient blood supply to the embryonic lens) to regress post-natally. Normally, the hyaloid vascular system in dogs begins to atrophy by day 45 of gestation. As the hyaloid vasculature regresses, the anterior pupillary membrane persists for a further 2 weeks after birth and eventually disappears. In some dogs, the pupillary membrane persists permanently and may extend to the anterior lens capsule, resulting in varying degrees of pathology such as anterior lenticular opacification and cataract formation.
A number of breeds appear to be predisposed, including the Staffordshire Bull Terrier, Bouviers des Flandres, Greyhound, Bloodhound, Airedale terrier, German Shepherd, Alaskan Malamute, Siberian Husky, Miniature Poodle, Labrador Retriever, Irish setter, Doberman Pinscher and Irish wolfhound.
Clinically affected dogs are often under six months of age and present with hemeralopia and a history of stumbling and bumping into objects. On ophthalmological examination, hyphema, secondary glaucoma, uveitis, leukocoria (white pupil), cataracts and retinal detachment may be observed.
This condition is graded clinically, based on severity:
- Grade 1 — retrolental fibrovascular pigmented dots
- Grade 2 — dots in combination with retrolental tissue proliferation attached to the posterior lens capsule
- Grade 3 — plaque in combination with parts of the hyaloid (tunica vasculosa lentis-TVL) system
- Grade 4 — plaque combined with lenticonus posterior
- Grade 5 — plaque, lenticonus posterior, and persistent parts of the hyaloid-TVL (combination of Grades 3 and 4)
- Grade 6 — combinations of former grades associated with abnormal lens shape due to coloboma or microphakia, and retrolental clots of pigment or free blood
Diagnosis of PHTVL/PHPV is based on history, ophthalmic examination findings following complete pupillary dilation, and exclusion of other causes of leukocoria.
Ocular ultrasonography usually reveals a small hyperechoic lens, a hyperechoic linear soft-tissue strand extending from the posterior pole of the lens through the optic disc and a persistent hyaloid artery.
Treatment is usually conservative, but in bilaterally affected severe cases, phacoemulsification of cataract and anterior hyaloid removal, with intraocular lens implantation is required.
- Doberman Breed Council
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