What's in a name? When it comes to ophthalmology, a lot. Persistent hyperplastic primary vitreous-an old name that addressees only the status of the primary vitreous-needs updating, said Michael Trese, MD.
Persistent fetal vasculature syndrome (PFVS), coined by Morton Goldberg, MD, seems more relevant because PFVS includes both the primary vitreous and the tunica vasculosa lentis (TVL).
"PFVS is a vitreoretinal dystrophy," said Dr. Trese, clinical professor of ophthalmology, Eye Research Institute, Associated Retinal Consultants, Oakland University, William Beaumont School of Medicine, Royal Oak, MI.
During normal development, the vessels fill the vitreous cavity. Usually the largest is the hyaloid artery from the disc to the lens in the area of the Mittendorf dot. This involutes by apoptosis beginning at 28 weeks of gestational age and is complete by the time of birth usually leaving Cloquet's canal. The vessels that engulf the lens, the TVL, generally regress in a similar fashion, according to Dr. Trese.
Three presentations of PFVS have been recognized.
The first, classic PFVS, is 90% unilateral and the affected eye is smaller than the fellow eye. Leukocoria at birth usually is when PFVS is discovered with no or a poor view of the posterior pole. The ciliary processes are pulled in.
Importantly, Dr. Trese noted, retinal dysplasia is the rate-limiting step for vison in all three forms of PFVS. A stalk is present from the optic nerve to the lens that can result from a tiny vessel or a larger stalk.
A variation of the classical anterior form may include multiple stalks that extend from other parts of the retina to the lens. A posterior form is characterized by a star fish appearance of the retina with small areas of retinal detachment around the disc that pull in to a stalk that does not reach the lens, he explained.
Surgical management of the classical form of PFVS usually is by a two-port vitrectomy.
"The white material and the capsule are removed," Dr. Trese said. "The posterior pole determines whether or not vision will be possible."
In some cases parts of the retina may retain some function.
The second PFVS presentation, the eccentric stalk, presents when the patient is 6 to 8 months of age with strabismus. In this form, a stalk can extend from the disc to the lens wrapped posteriorly with a traction retinal detachment that drags or detaches the fovea and causes the strabismus.
Following vitreous surgery, the strabismus can be reversed without muscle surgery. The lens insertion of the stalk generally does not involve the visual axis. The stalk can regress markedly when it is divided and not removed. Macroscopic or microscopic retinal dysplasia can limit vision.
During pars plana vitrectomy to manage an eccentric stalk, the eye is entered using an infusion light pipe. The light pipe is put in the eye but the infusion is off so as not to disrupt the attachment between the stalk and the posterior lens capsule; disturbing that tissue can result in development of a white cataract in a very short time, Dr. Trese explained.
When good visualization of the interior of the eye has been achieved, vertical scissors are introduced and the stalk is divided as close as possible to the lens without damaging the capsule. In a representative case, Dr. Trese reported that 6 months postoperatively the stalk regressed completely.
"The important point is that the surgeon does not have to remove the stalk in these cases with the associated potential of removing the surrounding retinal tissue," he said.
The third presentation, multifocal PFVS, is new and became recognized with the introduction of wide-field fluorescein angiography (FA).
"With wide-field FA, we found that PFVS often has a small to medium-sized avascular peripheral retina. This is quite important," he noted.
This new form of PFVS is characterized by areas of vessel remnants along the retinal surface and at the disc that do not behave as new vessels.
Dr. Trese said that they are thought to be isolated parts of the primary vitreous that did not involute. This is seen in eyes with avascular peripheral retina.
This is important, he explained, because the genetically driven apoptotic involution of the PFV vessels is blocked by vascular endothelial growth factor (VEGF) as in retinopathy of prematurity, which causes the tractional cells that contribute to retinal detachment. There is sufficient VEGF to prevent the involution of the PFV vessels completely, but insufficient VEGF to allow neovascularization and exudation, which are protected by an intact Wnt signaling system.
Dr. Trese and colleagues have been following five children who presented with multifocal PFVS when they were infants or young children.
The children have avascular peripheral retina and multifocal areas of PFV in the vitreous cavity along the retinal surface seen on FA. The retinal dysplasia has been difficult to assess because good optical coherence tomography scans have not been obtained.
One of the children was found to have a Wnt signaling mutation in LRP5; these children can achieve good vision, Dr. Trese noted.
Multifocal PFVS can be treated with laser application to the avascular peripheral retina. The patients are followed with wide-field FA. No disease progression has been seen after 3 to 5 years.
Dr. Trese concluded by noting that the three presentations of PFVS require different treatments.
"The final vision is dependent on the degree of retinal dysplasia, but functional vision can be achieved," he said.
Michael Trese, MD
Dr. Trese has no financial interest in any aspect of this report.