Ординатура / Офтальмология / Английские материалы / Textbook of Vitreoretinal Diseases and Surgery_Natarajan, Hussain_2008

Textbook of Vitreoretinal Diseases and Surgery

FIGURE 8-3: Optical coherence tomography: macular traction in a case of exudative age related macular degeneration with choroidal neovascularization (female, 85 years)

FIGURE 8-4: Intraoperative fundus image during vitrectomy: preretinal proliferations and tactional vitreous adhesions are visible

the Marburg eye clinic. It turned out that a complete PVD was found only in those 600 eyes with a rhegmatogenous retinal detachment. The posterior vitreous was found to be most adherent in patients with a proliferative diabetic vitreo-retinopathy. Here, tight connections were frequently found between the posterior vitreous and tractions along the great vessel arcades. The membranes were partially vascularized and had to be removed from the retina surgically with vitreous scissors. In some patients, a PVD was found over the macular area, in others, a second membranous structure was found beneath that was removed as well. If fine folds of the internal limiting membrane (ILM) were recognized, the ILM too was removed in an area with a radius of about two disc diameters

88 around the fovea. If the membrane could not be clearly visualized, it was colored with indocyaningreen (ICG). It could be observed, that ICG only precipitated on the preretinal vitreous structures

Textbook of Vitreoretinal Diseases and Surgery

FIGURES 8-6A AND B: Fundus image (A) and fluorescein angiography (B) in a case of age-related macular degeneration presenting choroidal neovascularization with incomplete posterior vitreous detachment and macular traction (female, 85 years)

around the optic nerve head and very difficult to identify due to its transparency in these patients. Some eyes show a tangential traction inserting at the rim of the macular hole. These patients frequently complicate with intraoperative retinal break formation because of peripheral tractions, which is treated by cryopexy or endolaser intraoperatively.

The posterior vitreous was often attached even in those eyes described as stage IV macular holes preoperatively, probably because vitreous clouding was interpreted as PVD. In all those eyes ICGassisted ILM-peeling was performed apart from inducing a PVD.

It was noted that the ILM appeared thinner than in diabetics but could be removed more easily than in an edematous macula. As already mentioned above, the ILM is especially adherent to the rim of macular holes and most likely itself a component of tangential traction. In stage I macular holes a perforating hole can be induced accidentally by the surgical procedure.

Patients with a cystoid macular edema following cataract surgery (Irvine-Gass-Syndrome) or recurrent inflammation presented with increased local vitreous adherence and incomplete PVD similar to a macular traction syndrome. This is also the case in patients with epiretinal gliosis, where the gliosis comes off together with the posterior vitreous.

Retinal Vein Occlusions

We performed pars plana vitrectomy with sheathotomy (separation of the common adventitial sheath of retinal arteries and veins in the area of occlusion) in patients suffering from branch retinal vein occlusion and neurotomy (cutting of the scleral ring at the optic nerve head) in those suffering from central retinal vein occlusion. None of these eyes presented with a PVD intraoperatively. Routine ILM removal proved more difficult in these cases with edematous retina, because the ILM seemed to be more adherent to the other retinal structures and at the same time more fragile. It could therefore not be removed in one piece.

Vitrecomy is Helpful in Many Retinal Diseases

90 The close neighborhood between retina and vitreous may explain the interdependence of disease

Retinal Stress by Vitreous Traction

processes of both structures. Schepens already described that a rhegmatogenous retinal detachment is only possible if the vitreous is liquefied and detached.7 A PVD becomes more likely with increasing age and is seen in over 50% in patients 65 years and older. 1,8,9

It is all the more amazing that this physiologic process is missing in many diseases of the posterior retina.10

Traction components may interfere with retinal physiology and metabolism by an adherent, thickened posterior vitreous attached to the retina thus negatively influencing diffusion between anterior and posterior areas in the eye. Several studies could show that vitrectomy may improve various retinal diseases. A PVD induced during surgery might be the key effect of vitreous surgery similar to the vitreous liquefaction found in diabetics following panretinal photocoagulation for proliferative diabetic vitreoretinopathy (PDVR).11

Many pathologies such as macular edema disappears after surgically induced PVD. Macular holes may close spontaneously following surgically induced PVD. ILM-peeling could increase the closure rate, but a sole vitrectomy may be sufficient in some patients.14

In AMD patients previously treated without success by PDT and intravitreal injections, the posterior vitreous was found attached during subretinal surgery.10 The reason could be that permanent macular traction causes an increased release of inflammatory parameters and VEGF into the subretinal space. This in turn might be responsible for the persistence, the growth, or even the induction of choroidal neovascularisation.

These observations by authors suggest that in the future more attention should be given to the vitreous when treating retinal pathology. If the posterior vitreous remains attached following minimally invasive procedures such as laser or intraocular injections, a surgically induced PVD by pars plana vitrectomy may be considered.

In future, a PVD or vitreolysis might be induced pharmacologically, i.e. by plasmin or microplasmin. Prospective, randomized, controlled, clinical trials are necessary to see whether a vitrectomy as primary treatment is reasonable in cases where there is no obvious traction and to assess the value of adjunct measures such as neurotomy, sheathotomy, and ILM-peeling.

Summary

Due to the immediate neighborhood of vitreous and retina, retinal diseases are frequently associated with changes is the vitreous. During the last years, the condition of the vitreous and posterior vitreous adherence were diagnosed biomicroscopically, my ultrasound and OCT. The results were then compared with findings during vitrectomy. In almost all vitrectomies for macular and retinal diseases we found an attached posterior vitreous intraoperatively, which seemed especially adherent at the posterior pole. This correlated only partly with preoperative findings, where a posterior vitreous detachment was described frequently. The literature describes a high percentage of complete posterior vitreous detachment in patients, increasing with age. In patients who undergo vitreoretinal surgery for macular or retinal diseases, an attached posterior vitreous is found frequently. We postulate that this finding, which is atypical for that age group, may be a causative agent for retinal or vascular disease and prevents a successful treatment of AMD and other diseases because

of macular traction. An early removal of the posterior vitreous may support treatment of these 91

Textbook of Vitreoretinal Diseases and Surgery

Introduction

Polypoidal choroidal vasculopathy (PCV) has been recognized since the 1980s. It was first described by Stern et al. and Perkovich et al as “multiple recurrent retinal pigment epithelial detachments in black women”.1,2 Later, it was classified as “posterior uveal bleeding syndrome” by Kleiner et al and Blumenkranz et al.3,4 In 1990, Yannuzzi and colleague designated it “idiopathic polypoidal choroidal vasculopathy” in order to characterize it as a distinct clinical entity of unknown etiology with a peculiar network of choroidal vessels, polypoidal subretinal choroidal nodular lesions, and recurrent serous and hemorrhagic detachments of the retinal pigment epithelium (RPE) and neurosensory retina.5 Using indocyanine green angiography (ICGA), Spaide et al confirmed that PCV has two basic choroidal vascular components: a branching network of vessels in the inner choroid and aneurysmal vascular dilations in a polypoidal configuration.6

More than two decades after the original report, knowledge about PCV has increased rapidly, thus allowing us to understand the demographic profile, clinical manifestations, clinicopathological correlation, natural course, modalities of treatment, and the visual prognosis in patients with PCV with greater detail and precision. The natural history of PCV is reported to be more favorable than that of neovascular age-related macular degeneration (AMD),7 however, half of all patients may suffer from severe visual loss due to massive hemorrhage or severe RPE atrophy after a longer follow-up period.8 Possible treatments include laser photocoagulation, photodynamic therapy (PDT), intravitreal anti-vascular endothelial growth factor (anti-VEGF), and surgical removal of the fibrovascular membrane with or without macular translocation.9-17

Epidemiology

PCV previously was thought to be a rare disease. However, although the true incidence of PCV is still unclear, improvements in diagnostic techniques have shown that PCV is actually more common than originally believed. The clinical presentations of PCV can mimic those of AMD; therefore, many patients may have received a diagnosis of AMD before PCV was well-recognized. Currently, ICGA is the diagnostic choice in differentiating PCV from AMD. Yannuzzi et al reviewed 167 patients initially diagnosed with AMD in the US, and found that 13 (7.8%) of them had PCV.18 Similar results were obtained by Sforzolini et al, in which 19 (9.8%) of 194 Italian patients presumed to have AMD actually had PCV.19 Kwok et al performed ICGA in 204 Chinese patients with provisional diagnoses of AMD, and found that 22 eyes of 19 patients (9.3%) had PCV.20 This percentage is even higher in the Japanese population. Sho et al performed fluorescein angiography (FA) and ICGA in 471 eyes with presumed neovascular AMD, and diagnosed PCV in 110 eyes (23%).21 Thus, PCV might actually be quite common among patients previously thought to have AMD.

Polypoidal Choroidal Vasculopathy

Textbook of Vitreoretinal Diseases and Surgery

SYSTEMIC FACTORS

Some studies found that 20%-30% of patients with PCV had a history of hypertension.21,25,29 Ross et al had suggested that certain subgroups of PCV and retinal arterial macroaneurysm might be pathophysiologically related as analogous hypertensive insults to the choroidal and retinal vascular beds.30 However, a relationship between PCV and hypertension could not be shown in other studies.20,24

Pathophysiology

The peculiar abnormality of PCV is believed to originate in the inner choroid, external to the choriocapillaries.7 It consists of 2 fundamental elements: a dilated network of vessels and multiple terminal aneurysmal protuberances in a polypoidal configuration.7 These polypoidal lesions appear to account for the episodic leakage and bleeding under the RPE and neurosensory retina that can occur in these patients. The exudative changes can lead to variably sized serosanguineous pigment epithelium detachments (PEDs).5,7 Some patients may also experience bullous retinal detachment and vitreous hemorrhage.1-3,5,7

HISTOPATHOLOGY

Few specimens of PCV have been studied histopathologically. Most reports describe a collection of dilated thin-walled vessels derived from choroidal vessels beneath the RPE in Bruch’s membrane. Lafaut et al examined submacular tissue from an eye with PCV and found a thick fibrovascular membrane with drusen and dilated thin-walled vessels that appeared saccular in serial sections. The authors noted that the aneurysmal vessels appeared to be of venular origin and were probably the pathological counterpart of the PCV lesion in ICGA angiography.31 Okubo et al also found tortuous, unusually dilated venules in a submacular polypoidal vascular lesion that had been surgically removed.9 However, Rosa et al examined an enucleated eye and proposed that the network of peripapillary vessels seen on FA and ICGA derived from branches of posterior ciliary arties.32 Terasaki et al examined two neovascular membranes obtained during macular translocation surgery for PCV.15 They found polypoidal structures within Bruch’s membrane, which were composed of clusters of dilated, thin walled blood vessels surrounded by macrophages and fibrin material. They showed positive immunohistochemical staining for vascular endothelial growth factor (VEGF) in the RPE and the vascular endothelial cells. In two enucleated eyes with rubeosis iridis and acute angle block glaucoma due to massive subretinal hemorrhage,33,34 extensive fibrovascular proliferation was noted within Bruch’s membrane and between Bruch’s membrane and the RPE. This disciform scar may reflect the end stage of the disease (Figures 9-1 and 9-2).

Polypoidal Choroidal Vasculopathy

FIGURE 9-1: (A, top left) Color photography of the fundus of a patient with peripapillary PCV demonstrates hemorrhagic pigment epithelial detachment and subretinal hemorrhage. (B, top right) ICGA angiography reveals a cluster of actively leaking polypoidal choroidal lesions and abnormal vessels over the peripapillary area. (C, bottom left) Color photography of the fundus of a patient with macular PCV demonstrates subretinal exudates and fluids. (D, bottom right) ICGA angiography reveals two actively leaking polypoidal choroidal complexes over the macular area

45 eyes with PCV.36 They found that vessels comprising branching networks began to fill simultaneously with the surrounding choroidal arteries in 38 eyes. Vessel pulsation, not a feature of CNV, was seen in 24 eyes. These authors concluded that PCV is caused by inner choroidal vessel abnormalities, not CNV.36

Kondo et al recently published two genetic analyses of PCV using single nucleotide polymorphisms (SNPs).44,45 They found that the LOC387715/HTRA1 variants are associated with both PCV and wet AMD in the Japanese population. However, the odds ratios and population-attributable risks were higher for the patients with AMD than for the patients with PCV.44 In another study, they showed that the elastin gene (ELN) variant was significantly associated with susceptibility to PCV, but

not to AMD.45 Their findings might implicate ELN as a susceptibility gene for PCV, and suggest that 97 a different pathogenic process may be involved in the phenotypic expression of wet AMD and PCV.45