Bilateral persistent hyperplastic primary vitreous: A rare entity.

Bilateral persistent hyperplastic primary vitreous (PHPV) is an uncommon entity which usually presents as leukocoria, microphthalmia, and cataract.[1] It is a developmental disorder of the eye which occurs due to abnormal persistence of fetal intraocular vessels in the anterior or posterior segments of the eye.[2] Primary vitreous forms around 7th week of intragestation life and starts involuting around 20th week and nearly always disappears at the time of birth. Failure of regression of primary vitreous results in many of the abnormalities seen in PHPV.[3] In these cases, the child usually presents due to poor vision and white reflex.[1] The entity often presents a diagnostic challenge as it is often confused with retinoblastoma.[2]

We present a case of a 8-month-old female child who presented with poor vision in both eyes. On examination, the patient poorly followed light with both eyes. A wide-angle convergent squint with left eye fixating was noted. Nystagmus and leukocoria were noted bilaterally [Figure 1]. There was no history of trauma. Family history and birth history were negative. The child was born at full-term by normal vaginal delivery. No history of any hospitalization or history of oxygenation was obtained.

Figure 1

Patient showing bilateral small globes and strabismus

Orbital ultrasound and computed tomography (CT) were performed. Ultrasound: B-scan ultrasonography was done using a high-frequency (10 MHz) transducer. An echogenic band in the posterior segment of both the globes extending from posterior surface of the lens to optic nerve head was observed [Figure 2]. On color Doppler, arterial blood flow was seen in this band confirming the diagnosis to bilateral PHPV [Figures 3a and 3b]. Axial lengths of left and right eyes were 16.1 and 16.2 mm, respectively. CT scan: CT scan showed a subtle hyperdense linear density in the posterior segment of both the globes representing hyaloid artery in the Cloquet's canal. No mass lesion or calcification was seen [Figures 4, 5a and 5b].

Figure 2

Ultrasound showing echogenic band in the posterior segment of both the globes extending from posterior surface of the lens to optic nerve head. Axial lengths of right and left eye are 16.2 and 16.1 mm, respectively

Figure 3

Color Doppler of (a) left and (b) right eye showing arterialized blood flow in the echogenic band

Figure 4

Axial CT imaging of bilateral globes showing linear hyperdensity extending from optic nerve head to the posterior surface of the lens representing hyaloid artery in Cloquet's canal (arrows). No mass or calcification seen

Figure 5

Sagittal CT of (a) right and (b) left globe showing linear hyperdensity extending from optic nerve head to the posterior surface of the lens representing hyaloid artery in Cloquet's canal (arrows)

Based on the above findings, a diagnosis of bilateral PHPV was made. Examination under anesthesia was performed which revealed corneal diameter of 8.9 mm in right eye and 9.1 mm in left eye with anterior chamber depth of 3 mm on right side and 3.1 mm on left side. Intraocular pressure was normal bilaterally (12–13 mm Hg). Lens was normal bilaterally. The posterior segment showed a falciform fold arising from the optic disk to posterior capsules of lens.

PHPV occurs due to incomplete regression of the embryonic vitreous and fetal intraocular vessels. The primary vitreous is formed during the 1st month of intrauterine life and starts regressing during the formation of secondary vitreous at 9th week. By the end of 3rd month, secondary vitreous fills most of the vitreous cavity and primary vitreous condenses into a narrow band (Cloquet's canal) running from the optic nerve to posterior aspect of lens.[1]

PHPV is usually isolated and unilateral. Bilateral lesions are usually associated with systemic or syndromic conditions,[4] such as trisomy 13,15, or 18.[2] In a study by Pollard, out of 83 cases only 2 patents (2.4%) had bilateral PHPV.[5] Haddal et al. found 7 of 62 (11%) cases to be bilateral.[1]

The most common presenting signs and syndrome are leukocoria, poor vision, and small eye and strabismus.[34] PHPV is classified into three types: Anterior, posterior, or combination of anterior and posterior.[1] Anterior PHPV has the best prognosis for vision, but approximately half of these patients also have an associated posterior component.[4] The anterior type of PHPV included a shallow or collapsed anterior chamber, a retrolental vascular membrane, cataract, and anterior chamber anomalies.[6] Abnormalities of lens and anterior chamber are signs of combined anterior and posterior variant of PHPV.[4] Complications of PHPV can be rupture of lens capsule, cataract, intraocular hemorrhage, secondary glaucoma, traction retinal fold, and subsequent phthisis bulbi.[1]

Diagnosis of PHPV can be made on imaging. Ultrasound reveals a hyperechoic, inhomogenous structure bilaterally in the vitreous chamber extending from the posterior wall of the lens till the optic nerve head and retina and vascularized on color Doppler.[7] From an imaging point of view, only the features of posterior PHPV are well known. In posterior PHPV, the globe is small and a fine linear structure extending from the head of the optic nerve to the posterior surface of the lens is seen on CT scan, which represents the Cloquet's canal. When seen, it is considered typical of PHPV.[3] On magnetic resonance imaging (MRI), PHPV appears as a triangular retrolental vascular soft tissue mass with a central stalk of hyaloid remnant connected to the optic disc. The overall shape of PHPV has been likened to a martini glass.[4] Presence of a band in post segment in PHPV should not be confused with retinal detachment in which hyperdense band extends from the papilla to oraserrata rather than to posterior wall of lens.[8]

Differential diagnosis of PHPV includes retinoblastoma, Coat's disease, vitreoretinal dysplasia, ocular toxocariasis, and a condition contributing to subretinal fluid or hemorrhage and retinopathy of prematurity.[6]

It is important to exclude retinoblastoma in all cases of lenkocoria. PHPV has a typical imaging appearance which allows reliable differentiation from retinoblastoma. It can be easily differentiated from vitreoretinal dysplasia as a patent hyaloid artery is not a feature of vitreoretinal dysplasia. Differentiation from retinopathy of prematurity is difficult on imaging. History of prematurity and low birth weight and supplementation of oxygen help in the diagnosis of retinopathy of prematurity.[1]

Although rare, bilateral PHPV should be considered in the differential diagnosis while evaluating a case of bilateral leukocoria. Typical imaging features of ultrasound, CT, and MRI can be helpful in the diagnosis and are important in differentiating this entity from the retinoblastoma.