• Cause: developmental ocular disorder.
• Signs: there is a spectrum of effects, from no visible outward signs to intraocular hemorrhage, cataracts and blindness.
• Diagnosis: ophthalmoscopy, ocular ultrasonography.
• Treatment: none unless vision impairment is caused by cataracts, which can be surgically removed by modified phacoemulsification.
• Prognosis: more severely affected dogs have poor vision. Phacoemulsification is more complicated in these cases and so the risks are greater.

Presenting signs

• The severity of the clinical findings of PHTVL/PHPV vary on a spectrum and a grading system of grades 1-6 developed by Stades has been internationally adopted.
• Grade 1 - Limited posterior capsular cataract with multifocal pigment or white dots on the capsule or retrolental.
• Grade 2 - More extensive central posterior capsular cataract with yellow-brown capsular/retrolental fibrous tissue. Multiple pigment dots found in both the central and peripheral portions of the posterior lens capsule. Cataract may be dense. Persistent pupillary membrane (PTVL anterioris) may also be apparent.
• Grade 3 - PTVL - hyaloid system vessels visible retrolentally as a meshwork, associated with Grade 2 abnormalities to a greater or lesser extent.
• Grade 4 - Posterior lenticonus of varying extent and associated Grade 2 abnormalities.
• Grade 5 - Combination of Grade 3 and Grade 4 abnormalities.
• Grade 6 - The severest manifestation, a combination of the other grades, plus abnormalities such as lens coloboma Lens: coloboma, microphakia, microphthalmos and intraocular hemorrhage.

Age predisposition

• Congenital condition which should be visible by six weeks of age.

Breed/Species predisposition

• Dobermann (inherited) Dobermann.
• Staffordshire Bull Terrier (inherited) Staffordshire Bull Terrier.
• Bloodhound Bloodhound.
• Bouvier des Flandres Bouvier des Flandres.
• Samoyed Samoyed.
• Siberian Husky Siberian Husky.
• Spanish Pachon.

Special risks

• Cataract surgery is more challenging when there is a patent hyaloid artery, which will require cautery. A planned posterior continuous curvilinear capsulorrhexis is usually required. An anterior vitrectomy may be required.
• Potential complications include vitreal hemorrhage with the formation of traction bands that could result in retinal detachment.