Fact-sheet: Persistent hyperplastic primary vitreous
Updated on 04/23/2019 at 9:52 AM
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Definition
Persistent fetal vasculature is a spectrum of rare ocular malformations ranging from a simple embryonic remnant to global ocular involvement (with potential compromise of visual prognosis and globe viability).
Risk of severe amblyopia, inflammatory complications, and painful glaucomatous crisis.
Incidence: 1/30,000 births
5% of childhood blindness
Embryology and pathophysiology:
- the primary vitreous appears at 5 weeks of embryonic life.
- the hyaloid artery centers the primary vitreous, where it gives off branches reaching the posterior pole of the lens vesicle.
- Mesoblast enters the optic cup through the embryonic fissure along the hyaloid artery and fills the interior of the cup up to the posterior part of the lens vesicle.
- At the 6th week of embryonic life, the first fibers of the secondary vitreous appear. They push the primary vitreous forward and centrally. The embryonic fissure begins to close at the same time.
- It captures the hyaloid artery within the future optic nerve, which will become the central retinal artery by the 5th month.
- From the 4th month onward, the vessels of the posterior tunica vasculosa lentis regress and then disappear.
- The vitreous portion of the hyaloid artery atrophies, leaving an empty channel, or Cloquet's canal, which connects the optic disc to the posterior surface of the lens.
Thus, the mature vitreous, composed mainly of secondary vitreous, is avascular.
- Several hypotheses: occurrence of an anomaly during the 6th week, at the time of intraocular vascular development?
Clinical features
- Leukocoria, microphthalmia, strabismus
- Prematurity and intrauterine growth restriction are commonly found in the history
- Physical examination sometimes supplemented by examination under general anesthesia, combining one or more of the following signs:
Cataract, presence of a retrolental vascular membrane, centripetal stretching of the ciliary processes, total or partial persistence of the hyaloid fetal vasculature, microphthalmia.
Ultrasound
First-line examination:
on B-mode, allows exclusion of a retinal tumor or intraocular calcifications
assesses the presence of microphthalmia (measurement of the axial length of the globe)
shows the vitreous as a wavy, mildly echogenic membrane, of variable thickness, extending from the posterior surface of the lens to the optic disc
detects vitreous hemorrhage, retinal detachment, and choroidal thickening.
Doppler evaluation can demonstrate persistent blood flow.
CT
Orbital CT provides information equivalent to ultrasound but allows better visualization of vascular structures through contrast administration.
it also shows the brain structures as part of the workup for a posterior form.
MRI
Predominant role.
At the ocular level, it shows T1 and T2 hyperintensity of the posterior segment related to the fibrovascular residue and subretinal fluid.
Also evaluates associated systemic malformations.
Rules out differential diagnoses (e.g., tumors).
Management
Surgical management is sometimes indicated in anterior forms because of the potential for visual recovery.
It is more debated in mixed and posterior forms (aim of avoiding complications, cosmetic reasons).
Classification
Involvement is isolated, unilateral, and sporadic in 90% of cases.
Bilateral forms are most often associated with systemic abnormalities.
Three main clinical forms may present: anterior, posterior, and mixed.
Anterior form: inconsistently combines the following three features: microphthalmia sometimes associated with microcornea, leukocoria due to the presence of a fibrovascular membrane or cataract, centripetal stretching of the ciliary processes by contraction of the fibrovascular membrane, occasionally with anastomoses to the iris vessels.
Posterior form: rarer, initially described under the name of falciform fold.
The retina may appear normal or show numerous abnormalities such as macular dysgenesis, pigmentary changes, glial or microcystic degeneration. The Bergmeister papilla (located at the center of the optic disc, a small cluster of fibrous tissue corresponding to a remnant of the hyaloid artery) is a minimal posterior form of persistent fetal vasculature.
When more extensive, it is characterized by pre-retinal vitreous condensation, often oriented radially, forming vitreoretinal traction bands.
These are responsible for areas of tractional retinal detachment.
Occasionally, a hyaloid artery persists, attached to the optic disc, with its anterior portion floating freely in the vitreous, without visual consequence.
Mixed form: the most common. Most often limited to a posterior polar cataract. Lens involvement is associated with a more or less atrophic vascular cord ending in a posterior attachment to the optic disc or peripapillary region.
Differential diagnosis
- Cataract
- Retrolental fibroplasia
- Retinoblastoma
- Exceptional congenital retinal detachments
- Norrie Disease (cataract, retinal dysplasia, mental retardation, deafness)
- Coats disease (idiopathic, retinal telangiectasias).