Imaging and Diagnosis of Polypoidal Choroidal Vasculopathy

Introduction

Polypoidal choroidal vasculopathy (PCV) was first described as a type of macular disorder presenting with recurrent subretinal pigment epithelial hemorrhage by Yannuzzi et al . in 1982. Similar cases have then been described by Kleiner and Stern. Initial findings from these patients all displayed two main features, including dilated and branching inner choroidal vessels, together with terminal reddish-orange, spheroid aneurysmal-like polyps, which can be found at subfoveal, juxtafoveal, extrafoveal, peripapillary, or peripheral regions. These vascular abnormalities were associated with multiple, recurrent serosanguineous detachments of the retinal pigmentary epithelium and the neurosensory retina, with hemorrhage originating from the polypoidal components, as confirmed with fluorescein angiographies. With advances in imaging and clinical findings, it has now been accepted that PCV is a distinct form of choroidal neovascularization, with unique risk factors, clinical manifestations, natural course, treatment responses, and final outcomes.

Epidemiology

PCV is more commonly found in pigmented race including black people and Asians. The prevalence can be up to 54.7% of patients suffering from presumed neovascular age-related macular degeneration (AMD) as described in one study from Japan but only accounting for only 5–10% of patients with AMD in Caucacians. Initially, it was believed that it would not occur in white people but now it has been found in Caucacians as well though with different clinical features like higher prevalence of peripapillary involvement and bilateral involvement.

Most of the patients suffering from PCV are over the age of 50, with a generally slightly younger presentation than wet AMD. Regarding sex predilection, studies from Japan showed a predominant involvement of male patients (71%), but for Europeans, females are more likely to be affected (75%).

Pathology

Histopathological findings from vitreoretinal surgeries and enucleation specimens have improved our understanding of the pathology of the disease. Large vascular channels have been identified from eyes with early vasculopathy. Degeneration of large dilated venules, small degenerated arterioles, and capillaries with thickened basement membranes were also found. In another study, hyalinization of choroidal vessels together with exudation of fibrin in plasma have been reported to be present in patients with PCV. Report of intra-Bruch membrane choroidal neovascularization has been identified which supported the idea that PCV is a variant of neovascular AMD. Interestingly, regarding the role of vascular endothelial growth factor (VEGF), different specimens showed conflicting immunostaining results, which may explain partly the refractory responses of PCV toward anti-VEGF treatment.

Risk Factors

Clinical Features and Course

Patient with PCV can be asymptomatic if there is no leakage from the lesions, whereas the less fortunate patients may suffer from acute or progressive visual loss. Acute visual loss is usually due to spontaneous rupture of the polypoidal lesions resulting in submacular hemorrhage ( Fig. 18.1 ) presenting with scotoma or even breakthrough vitreous hemorrhage causing profound visual loss. Polypoidal lesions may also result in exudative changes with accumulation of subretinal fluid and exudates, causing metamorphopsia and progressive blurring of vision.

On physical examination patients with PCV may have variable sized serous and serosanguinous detachments of neurosensory retina and/or pigmentary epithelium. Underlying vascular abnormalities may sometimes be visible especially when the overlying retina is flat and pigment epithelium is atrophic. Polyps’ size and number vary among patients. Microrips or tears of retinal pigment epithelium (RPE) may be present at margin of serosanguinous pigment epithelial detachments (PEDs). Complications may occur resulting in subretinal fibrosis, pigment epithelial hyperplasia, and atrophic degeneration. These lesions may appear in various parts of the retina and may be present bilaterally. Drusen may be present in the fellow eye, though less common than in cases of AMD.

The natural course of PCV can be highly variable, depending on the location, size, and associated complications including hemorrhages and exudates. It was previously thought that if PCV was left untreated, about 50% of patients will enjoy favorable outcome with spontaneous regression of lesions. However, it has been reflected from the results of longer term studies that PCV might not be as benign as ophthalmologists thought. Many PCV patients would instead suffer from repeated hemorrhage and leakage resulting in degeneration of photoreceptors and scarring of RPE, and subsequently leading to significant visual impairment. Microrips of RPE, though may present during the disease course, may resolve spontaneously afterward. A grape-like cluster of polyps have been identified to be associated with poorer visual outcomes due to their propensity to bleeding. A retrospective study in Chinese patients has revealed that there was a mean loss of 3.1 lines among PCV patients resulting in final visual outcome of 20/200 or worse in 68.2% of patients.

Clinical Imaging of Polypoidal Choroidal Vasculopathy

In this era of multimodal imagings for retinal diseases, there are reports on the use of various imaging modalities to visualize PCV. The use of these imaging techniques is useful not only in making the diagnosis but also has treatment implications. Moreover, it could be used to monitor treatment progress. In this section, we shall look into detail how different imaging modalities can be of use.

Clinical Diagnosis

The diagnosis, or at least suspicion of PCV, can be picked up at slit-lamp biomicroscopy. At times, PCV appears as an orange-red nodule ( Fig. 18.2 ). This is when there is elevation of the RPE overlying the polyp. Although this is highly indicative of PCV, it can sometimes be just a small PED.

However, when PCV presents in other ways, such as massive subretinal hemorrhage ( Fig. 18.1 ), or presents with subretinal fluid only, making a diagnosis at the slit-lamp may be difficult. In any case, any clinical suspicion should lead to indocyanine-green angiography (ICGA), for better delineation of the lesion.