Persistent fetal vasculature (PFV), also known as persistent hyperplastic primary vitreous (PHPV), is caused by incomplete degeneration of the primary vitreous. In recent years, continuous embryonic vasculopathy is recommended. Apart from the front PFV and rear PFV, two types of simultaneous performance, known as the mixed type. Front PFV is characterized by residual anterior original vitreous artery, vascularized fibrous membrane behind the lens, small eyeball, shallow anterior chamber, small lens with cataract, and elongated ciliary process surrounding the small lens. Leukocoria may also be noted at birth in combination with glaucoma. The main manifestation during the natural course of the disease is amaurosis, and vision may be partly preserved after surgery in some patients. The rear PFV may occur alone or may be accompanied with front PFV, which is often combined with small eyeball with normal anterior chamber and transparent lens without proliferation of the membrane of posterior lens. In the vitreous cavity, pedicellate tissue which emanates from the optic disc extends forward often along the folds of retina and is often pulled towards the subtemporal peripherals. These tissues fan out towards the anterior vitreous body. It is estimated that in 90% of the cases, the disease occurs in one eye, and often results in poor vision[1]. Residual membrane of the pupil, also known as persistent pupillary membrane (PPM), is created by the incomplete absorption of the vascular membrane on the surface of the lens during the embryonic period. PPM is a common congenital anomaly of the eye, and there are two types of residual membrane: filamentous and membranous. When the PPM attachment points are located in the iris, one end begins at the anulus iridis minor and the other end is attached to the outside of the contralateral anulus iridis minor or the anterior capsule of the lens. There are also stellate pigment masses which are completely attached to the anterior surface of the lens. In general, PPM does not affect vision and pupil movement, and resolves by itself without treatment. However, in cases with a thick PPM that affects vision, surgery or laser treatment are required [1]. Fibrovascular pupillary membrane(FPM)is also referred to as a unilateral anterior segment disorder associated with a congenital white pupillary membrane and anterior chamber angle abnormalities. In 1986, Cibis described it as a fibrovascular membrane partly covering the pupil and attached to the lens, and fibrous tissue extended to the angle of the anterior chamber [2]. Since then, researchers have considered it to be a congenital pupillary-iris-lens membrane with goniodysgenesis or congenital idiopathic microcoria [3, 4]. Because of the fibrous pupillary-iris-lens membrane and the prominent Schwalbe’s line, the disease often tends to progress to glaucoma for the goniosynechia[2, 5]. Congenital idiopathic microcoria was described as a condition with some minor fibrous tissue at the margin of the pupil by Lambert by observing 5 cases[4]. In this condition, the lens always lacks opacity, and the membrane can be peeled off the anterior capsule[2–6]. We know from anatomy that in early development, the pupillary membrane is attached to the edge of the pupil. Later, due to mesenchymal division, the pupil membrane begins to separate from the iris, but remains attached to the septum at the front of the iris. Around the eightieth month, the pupil membrane begins to degenerate and eventually disappear. Tiny fibrous remnants often exist after birth. Cibis and colleagues postulated that FPM originates from the neuroectoderm and is a remnant of the embryonic iris tissue[7]. Lambert and colleagues proposed that it may be a remnant of the anterior tunica vasculosa lentis[4]. Kesarwani et al. suggested that the presence of fibrous tissue and tissue of embryonic muscle origin indicated that the membrane is more likely to be a remnant of the fetal iris than a remnant of fetal blood vessels, and that myofibroblasts or smooth muscle cell lineages can cause progressive contraction of the membrane[8]. In clinical practice, the anterior capsular plaque (ACP) in congenital cataract has been reported, which is described as a distinct opaque region. Plaque is a multifocal, dense, white opacity adherent to the internal surface of anterior and posterior lens capsule[9]. The lens contains lens epithelial cells (LECs), which can undergo epithelial-to-mesenchymal transition (EMT) and secrete extracellular matrix (ECM)[10, 11]. Studies[9] have also shown that the incidence of ACP is highest in a mature cataract, which may be due to the chronic biochemical changes that trigger LECs to form ACP. Alterations to LECs may trigger the proliferation of LECs in certain areas, resulting in overlapping of cells. These overlapping cells may undergo rapid division and EMT, forming smaller ACPs. The growth or fusion of small ACPs forms large ACPs. The area of ACP is proportional to the amount of ECM. Anterior subcapsular cataract (ASC) is a fibrotic disease caused by abnormal degradation and aggregation of the extracellular matrix. Given that the development of ASC involves the transformation and proliferation of anterior lens epithelial cells[12], both Smad3 signaling and lens-specific expression of TGF-β play important roles in ASC[13]. [14].
In the present case, the child was misdiagnosed as congenital cataract due to poor coordination and incomplete examination. After treatment, a diagnosis of FPM combined with PPM was made. The disease presented as opaque plaque on the external surface of the anterior capsule associated with residual pupil membrane.
The purpose of this case report is to review the diagnosis and treatment of FPM, and to identify the clinical features, with the overarching aim of avoiding the misdiagnosis of congenital membranous cataract.