**3. Ophthalmic manifestations of systemic thrombosis**

Systemic venous thrombosis can cause significant ocular symptoms and signs. Evidence suggests that ocular manifestation in systemic thrombosis increases the risk of cerebral events (Asherson, Khamashta et al. 1989) and ultimately, this impacts the prognosis of the patient.

It is, therefore, important to consider ocular features of systemic venous thrombosis, but, it is also equally important that clinicians are aware of the ophthalmic features of systemic conditions that predispose to a venous thrombosis, such as thrombophilias.

It is clearly impossible to consider all systemic conditions that cause a predisposition to venous thrombosis in this chapter. Therefore, here we will consider two systemic conditions that have important ocular manifestations. Firstly, we will discuss cerebral venous sinus thrombosis and to highlight the ocular features of systemic thrombosis. Then we will examine anti-phospholipid syndrome to review the ocular features of a condition that is a risk factor for venous thrombosis.

#### **3.1 Ophthalmic manifestations of cerebral venous sinus thrombosis**

Cerebral venous sinus thrombosis (CVT) is a condition that results from thrombosis and occlusion of the cerebral veins or dural sinus. This thrombosis causes increased venous pressure and subsequently results in impairment of cerebrospinal fluid (CSF) absorption and increased intracranial pressure (ICP). Regardless of the site, all CVT can cause raised ICP. The common sites for CVT include the cavernous sinus, sigmoid sinus, transverse sinus and sagittal sinus. Rarer sites of thrombosis include the lateral sinus, jugular vein, posterior fossa vein and the deep cerebral venous system (straight sinus).

Impaired CSF absorption is associated with increased intracranial pressure, while increased capillary pressure disrupts the blood-brain barrier, decreases capillary perfusion and results in capillary damage. This increased capillary pressure ultimately causes vasogenic and cytotoxic oedema as well as cerebral parenchyma lesions (Gotoh, Ohmoto et al. 1993; Yoshikawa, Abe et al. 2002).

#### **3.1.1 Prevalence**

CVT is a rare thrombotic occurrence with an incidence of 3-4 per million (Stam 2005). It is more common in females compared to males with a ratio of 3:1 (Ferro, Canhao et al. 2004), and is also more common in children compared to adults (Agnelli and Verso 2008).

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Fig. 7. Fundus photograph showing a 'champagne cork' like appearance in chronic

a Y shaped retinochoroidal shunt (S) due to the retinal vessels diverting towards the choroidal vessels and is another fundus feature of chronic papilloedema. Corresponding visual fields images shows significant field constriction in the right eye (c) and an enlarged

blind spot in the left eye (d).

papilloedema in the right eye (a) and left eye (b) of the same patient. In the right eye, there is
