The eye and visual system in the preeclampsia/eclampsia syndrome: What to expect?

Abstract

The preeclampsia/eclampsia syndrome is a multisystem disorder that can include cardiovascular changes, hematologic abnormalities, hepatic and renal impairment, and neurologic or cerebral manifestations. It also can affect the eye and visual pathways. Visual symptoms concern up to 25% of patients with severe preeclampsia and 50% of patients with eclampsia. This review discusses the ophthalmic complications of preeclampsia/eclampsia with focus on the hypertensive retinopathy, exudative retinal detachment and cortical blindness.

Introduction

Pregnancy, being a real challenge to the human body, is associated with a group of physiologic and pathologic changes. One of the most important pathologies accompanying pregnancy is the preeclampsia/eclampsia syndrome. The syndrome is a multisystem disorder that can include cardiovascular changes, hematologic abnormalities, hepatic and renal impairment, and neurologic or cerebral manifestations.^1,2 It also can affect the visual pathways, from the anterior segment to the visual cortex. Improved understanding of the nature and pathophysiology of ocular diseases that accompany preeclampsia/eclampsia offer the opportunity for meaningful counseling and management of the pregnant women who presents with ocular changes. This review discusses the ophthalmic complications of preeclampsia/eclampsia with focus on the hypertensive retinopathy, exudative retinal detachment and cortical blindness.

Definition

Preeclampsia is a clinical syndrome that afflicts 3–5% of pregnancies and is a leading cause of maternal mortality, especially in developing countries.^3,4 It is a multisystem hypertensive disorder, with the clinical spectrum including severe preeclampsia; eclampsia; hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome; and HELLP syndrome with eclampsia. Preeclampsia is defined as the new onset of hypertension and proteinuria during the second half of pregnancy.¹ The diagnosis of preeclampsia requires blood pressure >140/90 mm Hg on two occasions combined with urinary protein excretion >300 mg/day¹.^4,5 Edema is a classic feature of the disease, however, it is no longer considered a diagnostic feature given its lack of sensitivity or specificity.^1,2,4,5 Eclampsia is an acute and life-threatening complication of pregnancy characterized by the appearance of tonic-clonic seizures, usually in a patient who had developed preeclampsia.²

Pathophysiology

Preeclampsia is considered a systemic vascular disorder where both hypertension and proteinuria implicate the endothelium as the target of the disease. The hypertension of preeclampsia is characterized by peripheral vasoconstriction and decreased arterial compliance.^3,4

In preeclampsia, the refractoriness to vasoactive agents is lost first followed by the loss of vasoconstriction, which results in a decrease in intravascular volume, which in turn, shunts to the extravascular spaces. There is also an imbalance between proangiogenic and antiangiogenic factors during preeclampsia. The two important antiangiogenic factors implicated in preeclampsia are soluble vascular endothelial growth factor (VEGF) and soluble endoglin. Nitric oxide signaling is involved in vascular relaxation and is reduced in preeclampsia.^4,5

Ocular complications

The complications of preeclampsia extend to involve multiple systems and organs, the eye and visual system are of no exception. Visual symptoms concern up to 25% of patients with severe preeclampsia and 50% of patients with eclampsia.^5–7

Preeclampsia/eclampsia has various ocular manifestations. Blurred vision is the most common visual complaint. Focal or generalized arteriolar narrowing is the most common ocular finding in preeclampsia/eclampsia syndrome. Other ocular manifestations include photopsia, visual field defects, sudden inability to focus, and in severe cases, complete blindness.^5–7

Blindness and preeclampsia/eclampsia

Although visual disturbances are quiet common, complete blindness is rare, with an incidence of 1–3%.^6–8

Blindness in preeclampsia/eclampsia syndrome can be due to the involvement of the occipital cortex, retina, or optic nerve. In the past, most cases of blindness in preeclampsia and eclampsia were commonly attributed to retinal pathology including vascular abnormalities, edema or detachment and acute ischemic optic neuropathy as a result of decreased blood supply to the prelaminar portion of the optic nerve. Nowadays, more emphasis is being placed on cortical blindness.^6–8

Hypertensive retinopathy

The effect of hypertension extends to involve the vasculature of the retina, choroids and optic nerve head.⁹ At the pathophysiologic level, the primary response of the retinal vasculature to systemic arterial hypertension is vascular narrowing. This response to an increased blood pressure leads to focal or diffuse vasoconstriction. In addition, extravasation of fluid to the extravascular spaces occurs as a result of increased vascular permeability. Resultant retinal changes may manifest as decreased retinal to vein ratio, cotton wool spots, hemorrhages, Elschnig spots and serous retinal detachments.^9,10 Jaffe and Schatz, found a significant relationship between reduced arteriole to vein ratio and preeclampsia, suggesting retinal vasospasm and resistance to blood flow as a possible explanation for visual symptoms.⁷

A measurable narrowing of the retinal arteries can be demonstrated in about 50% of uncomplicated pregnancies with physiologic increase in blood pressure. This narrowing is functional and disappears with the termination of pregnancy. The degree of narrowing ranges from 10% to 40%, thus it is very difficult to discriminate between a normal and mild preeclamptic patient based on fundoscopy.^9,11

Retinal changes due to severe preeclampsia are similar to the changes of hypertensive retinopathy without the organic changes of arteriolosclerosis.^9–11

Severe arteriolar spasm is the most common fundoscopic finding, occurring in 70% of preeclampsia cases. As a result of this spasm, retinal vessels appear like a corkscrew or a beaded pearl necklace. Other fundoscopic features include arteriovenous crossings, hard and cotton-like exudates, retinal hemorrhages and optic head swelling.^11,12

The severity of retinal arteriolar changes is more closely related to the degree of underlying vasospasm. Previous studies showed that the level of retinopathy in patients with preeclampsia did not correspond to the severity of hypertension (systolic or diastolic).^9–12 It has been suggested that retinal changes in preeclampsia may indirectly indicate the level of placental vascular status and, hence, placental insufficiency and fetal birth weight.^9–12

Preeclampsia/eclampsia related retinopathy generally resolves soon after delivery and no specific treatment is required.^9–12

Serous retinal detachment (SRD)

SRD is an unusual cause of visual loss in preeclampsia, first described by von Graefe in 1855. It involves separation of the neurosensory retina from the pigmented retinal epithelium (RPE) and is one of the emergency situations in ophthalmology.¹²

The exact pathophysiology of SRD in cases of preeclampsia is not well known. It is usually present in patients with severe preeclampsia or eclampsia, and they are usually observed in the absence of significant retinal vascular abnormalities and retinal breaks. Hayreh et al. suggested that SRD in preeclampsia may be caused by choroidal ischemia secondary to accelerated hypertension.¹³

The incidence of SRD is approximately 1% for severe preeclampsia and 10% for eclamptic patients.^12,14 Clinically, patients present with sudden loss of vision. The detachments are often bullous and bilateral. Although it can be present at any time during pregnancy, this condition most often appears before, or soon after, delivery.^14,15 Mothers with the most severe forms of preeclampsia have the worst fundoscopic findings.^14–17

Conflicting opinions exist on whether maternal or fetal outcome is worse in patients with fundoscopic signs. Some studies reported poor fetal prognosis, while others reported no prognostic implications on the fetus.¹⁷ SRD management in preeclampsia is conservative and involves treating the underlying condition. Spontaneous resolution usually occurs within few weeks and visual prognosis is excellent. After delivery, the subretinal fluid is reabsorbed by the RPE and visual acuity should return to pre-detachment levels within weeks.⁷ However, patients with severe preeclampsia may be left with permanent visual loss, despite resolution of the SRD due to extensive RPE necrosis.⁷

Cortical blindness

Acute cortical blindness is one of the most dramatic presentations of preeclampsia and is historically known to be reversible. It is defined as blindness occurring in association with normal fundoscopy and pupillary function.¹⁸

The exact mechanism of cortical blindness in preeclampsia/eclampsia is unclear. It may result from cerebral vasospasm and ischemic injury or it may arise from vasogenic edema due to increased capillary permeability. Previous reports suggested that cortical blindness in association with preeclampsia/eclampsia may result from petechial hemorrhages and focal edema in the occipital cortex.⁸ Recently, single-photon emission tomography studies supported the finding that elevated capillary permeability and vasogenic edema are involved in patients with cortical blindness.^18–20

Cortical blindness is manifested in 1–15% of patients with severe preeclampsia and eclampsia.⁸ It may occasionally be the first clinical symptom preceding seizures by 4–7 hours. Cortical lesions are usually bilateral and is often in the posterior cortical areas.^18–20

Neuroimaging findings in cortical blindness range from normal to typical findings. Typically, there are bilateral cortical occipital lesions with hypodensity on CT or hyperdensity on T2-weighted MRI.^20,21

Fortunately, blindness due to occipital lesions is reversible and the lost vision is usually regained within 4 hours to 8 days.^18–21

Late complications

Permanent ocular changes may develop in patients with preeclampsia and may be mistaken for hereditary disorders if discovered later in life. Permanent changes include narrowing of arteriolar caliber, retinal pigment epitheliopathy and patches of choroidal atrophy.²²

Other late complications include proliferative retinopathy (PR). The occurrence of PR is rare and is thought to be a consequence of ischemia following microthrombus formation in the periphery of the retinal microcirculation. The latter was related to hemorrhagic alterations and activation of the thromboplastin–fibrinogen system that occur in preeclampsia.²³

Other complications

Rare ocular complications of preeclampsia/eclampsia that have been previously reported include; choroidal infarcts, papillophlebitis, retinal artery and vein occlusion, ischemic optic neuropathy, optic atrophy, optic neuritis, thrombosis of the central retinal artery and purtscher-like retinopathy.^24–26

Conclusion

Visual disturbances are very common among pregnant women with preeclampsia/eclampsia. Physicians should have a firm understanding of the various ocular conditions associated with these disturbances. In addition, it is very important to be vigilant about the rare and serious conditions that may occur in pregnant women with visual complaints. Prompt evaluation may be required and the immediate transfer of care of the patient may help saving the lives of both the mother and the baby.