Fig. 19.1
Persistent pupillary membrane. A 5-year-old boy with a visible pupillary membrane and iris dysplasia in the right eye
19.2.1.2 Iridohyaloid Blood Vessels
Iridohyaloid blood vessels are also caused by the failure of involution in the anterior tunica vasculosa lentis. These vessels lead to the appearance of radial vessels lying superficially in the iris stroma. They appear as hairpin loops when reaching the pupil. Occasionally, limbal connective tissue malformation may be detected in the same meridian.
19.2.1.3 Mittendorf Dot
A white dot is found about 0.5 mm nasal to the posterior pole of the lens capsule, which is due to the incomplete regression of the hyaloid artery. It is also found in 0.7–2.0 % of the normal population. Since it rarely affects the vision, no treatment is needed.
19.2.1.4 Persistence of the Posterior Fetal Fibrovascular Sheath of the Lens
Persistent posterior fibrovascular sheath of the lens is characterized by fibrous membranes located in the retrolental space and is caused by the failure of regression of the posterior tunica vasculosa lentis, which is classically called PFV syndrome (Fig. 19.2a, b). Typically, the retrolental membrane is white or pink, distinguishing it from the yellow exudation found in Coats’ disease or the snow-white calcifications in retinoblastoma. The area of the retrolental membrane varies widely, and in some cases, it may be as small as a dot or, in others, the entire posterior surface of the lens is covered. The lens itself varies from completely clear to severe opacification on the posterior capsule. Sometimes, the elongated ciliary processes can be found, which is due to the proliferation and traction of the incompletely involuted posterior tunica vasculosa lentis (Fig. 19.2c).
Fig. 19.2
Persistence of the posterior fetal fibrovascular sheath of the lens. (a) A 2-year-old boy with a yellowish-white fibrous membrane covering the entire posterior surface of the lens in the left eye. There are vessels extending on the membrane, the fundus is invisible, and the lens is clear (A photograph taken with a RetCam – a wide-field imaging system). (b) A 3-year-old boy with a visible fibrous membrane (5 × 5 mm) at the center and superior temporal of the posterior lens capsule in the right eye (A photograph of the anterior segment of the eye). (c) A 1½-year-old girl with leukokoria in her right eye. A yellowish fibrous membrane was found immediately posterior to the lens. There are vessels extending on the membrane, and the fundus is invisible. The arrows indicate the ciliary processes on the temporal side that are centrally dragged (A photograph taken using a RetCam – a wide-field imaging system)
19.2.1.5 Lens Opacity
The proliferative fibrous membrane in the vitreous chamber accounts for most cases of lens opacity. The main causes of a proliferative fibrous membrane leading to lens opacity include the following: (1) The proliferation and construction of the fibrous membrane may break through the posterior lens capsule and enter into the lens, leading to secondary cataract. (2) Due to the involution and traction of the persistent hyaloid artery, the posterior capsular membrane of the lens may rupture, causing opacification of the lens, which then induces an immune response and the growth of granulation tissue (Fig. 19.3).
Fig. 19.3
Lens opacity. Photograph of the anterior segment of the eye shows a 4-year-old boy with lens opacity in the right eye. An attached retina is visible through the clear inferior lens
19.2.1.6 Persistent Hyaloid Artery
Fetal hyaloid vessels are usually located within Cloquet’s canal and ordinarily involute by the 7th month of gestation. If this hyaloid system fails to regress completely, a remnant cord extending from the optic nerve head to the posterior lens capsule is manifested (Fig. 19.4).
Fig. 19.4
Persistent hyaloid artery. A photograph taken using a RetCam – a wide-field imaging system – shows a 9-month-old girl with a visible remnant extending from the optic disk to the posterior lens capsule. Part of the posterior capsule is opaque and the retina is attached
19.2.1.7 Bergmeister Papilla
A Bergmeister papilla is the incomplete regression of the posterior part of the hyaloid artery, and it manifests as a membranous or short band-like lesion attached to the optic disk head (Fig. 19.5). A Bergmeister papilla itself will not affect visual function, and its impact on vision mainly depends on whether the remnant causes macula traction.
Fig. 19.5
Bergmeister papilla. A photograph taken using a RetCam – a wide-field imaging system – shows a 4-month-old boy with a short band attached to the optic papilla in the right eye. A Bergmeister papilla, a clear lens, and an attached retina are demonstrated
19.2.1.8 Retinal Folds
In some cases, PFV is also accompanied by retinal folds, which may occur in any quadrant, but is mostly an inferotemporal predilection. A normal anterior chamber and clear lens are present, with possible occurrence of microphthalmos. It is presumed that a small amount of fibroproliferative tissues backward along Cloquet’s canal and attach to the retina, thus leading to the formation of retinal folds. In some serious cases, this may cause tractional retinal detachment with a poor prognosis (Fig. 19.6).
Fig. 19.6
Retinal folds. A photograph taken using a RetCam – wide-field imaging system – shows a 1-year-old boy with inferotemporal retinal folds
19.2.1.9 Congenital Tent-Shaped Retinal Detachment
The primary vitreous containing the hyaloid artery, located at the optic disk, proliferates and adheres to the retina, causing partial retinal traction and thus leading to tent-shaped retinal detachment (Fig. 19.7).
Fig. 19.7
Congenital tent-shaped retinal detachment. A photograph taken using a RetCam – wide-field imaging system – shows a 7-year-old girl with the primary vitreous located between the posterior lens capsule and the optic papilla in the left eye. The primary vitreous tracts part of the retina, forming the tent-shaped detachment
19.2.1.10 Macular Abnormalities
Macular abnormalities are secondary to tractional retinal detachment. Visual function is extremely poor in these patients.
19.2.1.11 Microphthalmos
Microphthalmos may be found in the anterior or posterior PFV, or it may be secondary to tractional retinal detachment. Usually, PFV is accompanied by arrested development of the eyeball.
19.2.1.12 Secondary Glaucoma
Secondary glaucoma is the most common cause of eventual blindness in children with PFV. The pathogenesis of secondary glaucoma associated with PFV is as follows: (1) The traction of the retrolental fibrovascular membrane leads to the rupture of the posterior capsule and the ensuing secondary cataract, lens expansion, anterior shift of the iris diaphragm, shallow anterior chamber depth, and secondary angle-closure glaucoma. With long-term high intraocular pressure (IOP), the corneal and scleral walls expand, ultimately resulting in buphthalmos. (2) Secondary glaucoma may also result from the inflammatory reaction and depigmentation of the iris. (3) When the ciliary process is involved in the retrolental fibrovascular membrane and centrally dragged, sequential zonular laxity will exaggerate the anterior displacement of the iris diaphragm [9, 10].
According to the ocular segments involved, PFV is traditionally divided into three types: anterior, posterior, and combined PFV. Anterior PFV is relatively common, accounting for 25 % of all cases, and its main manifestations are cataracts and retrolental mass. In some pediatric patients, it can also present as a shallow anterior chamber, elongation of the ciliary processes, and thickening of the blood vessels of the iris. Secondary angle-closure glaucoma may also occur in a few cases due to the expansion of the lens. Posterior PFV, as the name suggests, mainly involves the vitreous and the retina and accounts for 12 % of the affected population. It may manifest as solid remnants in the vitreous, retinal proliferative membrane and retinal folds. Sometimes, it may also present as abnormalities of the macula or the optic disk. Combined PFV, involving the anterior and posterior segment, is commonly seen in clinical practice, accounting for approximately 60 % of all cases [4]. As this classification system provides guidance to clinical treatments, particularly the choice of surgical approach, it is now widely used clinically.
19.2.2 Imaging Diagnosis
19.2.2.1 Ultrasonography and Color Doppler Imaging
With high resolution, ultrasonography is great merit to the eyes with opaque media in PFV. A-mode ultrasonography can reveal a shortened axial length. B-mode ultrasonography demonstrates the typical umbrella-shaped lesions that occupy Cloquet’s canal between the posterior capsule and anterior vitreous (Fig. 19.8). The umbrella lies behind the lens and adheres to the posterior capsule. The struts of the umbrella run through the vitreous cavity to the optic papilla. The internal reflection of the struts is irregular and without after movements.
Fig. 19.8
B-mode ultrasonography examination for PFV. A B-mode ultrasound image reveals that a tubular membrane adherent to the optic disk in the vitreous cavity in the left eye of a 3-year-old boy
Color Doppler imaging (CDI) utilizes the principles of ultrasound to assess the physical characteristics, morphological structures, and functions of human tissues. With its direct revelation of the pathological location, morphology, and characteristics of the blood flow signals and spectrum in the affected location, CDI is now widely used in ocular diseases. Since it is noninvasive and reproducible, CDI is of great application value in diagnosing PFV, especially in cases where the fundus examination cannot be conducted due to noncompliance or the opaque media.
Our research shows that according to CDI results, all PFV eyes could be grouped into four types: Type I (“I” shape), Type II (“Y” shape), Type III (inverted “Y” shape), and Type IV (“X” shape) (Fig. 19.9) [11]. Type I (“I” shape) presents as a linear narrow band extending from the optic disk to the posterior lens capsule, and blood flow can be detected in the band. Type II (“Y” shape) manifests as a membranous septum with a narrow base extending from the optic disk; however, the posterior lens capsule is widely covered. Ciliary detachment and traction or dense ciliary membranes were noted with ultrasonography. CDI showed detectable blood flow in both the membranous septum and the retrolenticular fibrovascular membrane. Type III (inverted “Y” shape) is characterized by a membranous septum with a wide base extending from the optic disk, which narrows gradually or suddenly, and is attached to the center or paracenter of the posterior lens capsule. Besides significant blood flow in the slim stalk, flow on the margin of the mass with a wide base anterior to the optic nerve was detected in all subjects. Funduscopy for these patients revealed the protrusion lesion to consist of a tractional retina detachment and fibrosis of the vitreous. The retinal artery and veins were noted to be tortuous or partially occluded with fundus fluorescein angiography (FFA). A detached and dislocated macula was found in the protrusion lesion in most of the subjects. Type IV (“X” shape) is characterized in a membranous septum extending from the optic disk with a wide base and covering the majority of the posterior lens capsule. Blood flows can be detected in the band between the optic disk and the lens and in the retrolental fibrovascular membrane.
Fig. 19.9
The classification of PFV according to CDI results. (a) A 4-year-old boy with an “I”-shaped echo in the right eye, blood flow can be detected in the retrolental band. (b) A 4-year-old girl with a “Y”-shaped echo in the left eye, blood flow can be detected in the retrolental band and the retrolental fibrovascular membrane. (c) A 4-month-old boy with an inverted “Y”-shaped echo in the right eye. The central blood flow presents as the persistent hyaloid vessel. The blood flows in the two sides present as the retina, revealing traction on the optic disk and the peripheral retina. (d) A 1-year-old boy with an “X”-shaped echo in the right eye. Blood flows can be detected in the band extending from the optic disk to the posterior surface of the lens and the retrolental fibrovascular membrane. The central blood flow presents as the persistent hyaloid vessel, and the blood flow signals are also visible on either side of the prepupillary fibrous mass
Four types of combined PFV were suggested in this study, with the determination made according to the area of posterior capsule coverage and the base of the preoptic elevated echogenic tissue. Types II and IV had a wide base attached to the posterior surface of the lens, usually accompanied by ciliary detachment and traction or dense ciliary membrane. Types III and IV had preoptic stalks with a wide base, while Type I had narrow adhesion to both the lens and optic nerve. Children with different types of PFV demonstrated different clinical characters. The axial length is normal in Type I, but decreased in the other types, especially in Type IV. However, visual function was affected more obviously in Type I, probably due to the retrolenticular stalk that was often attached to the central part of the posterior capsule. Thus, early screening is highly recommended in children, even in newborns, in order to facilitate the early detection and treatment of PFV.
Due to recent advances in surgical instrumentation and techniques, the indications for surgery in combined PFV have changed. Early surgical intervention may prevent progressive, pathologic changes and so can offer hope for a positive visual outcome [4, 6]. However, two different techniques have been advocated to remove the retrolenticular membranes associated with different forms of PFV: an anterior transpupillary approach and a posterior pars plana/plicata approach. When using ultrasound and CDI imaging, the pars plana/plicata approach should be avoided in Type II and Type IV patients according to our current classification system because of the dense coverage of the ciliary plana/plicata membranes. Surgical removal via the pars plana/plicata may increase the risk of inadvertent excision of the retina or retinal detachment. The anterior technique, which allows removal of these dense lenticular or retrolenticular membranes under continuous direct visualization, is safer and more reliable in this context. On the other hand, in patients with Types I and III PFV, if surgery is performed, it is safe to utilize a pars plana incision.
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