Blindness and Low Vision Clinical Trial
Official title:
Study of the Benefit of Early Treatment With an Endothelin Inhibitor (Bosentan) in Patients With Sudden Blindness Due to Giant Cell Arteritis: CECIBO
Giant cell arteritis , also named Horton's disease, is the most common vasculitis in subjects
over 50 years old. The incidence increases with age : from 188 to 290 cases per million
inhabitants per year, with a North-South gradient.
The major risk of Horton's disease is blindness, unilateral, occurring in 15 to 20% of cases,
sometimes preceded by episodes of transient amaurosis. The decrease in visual acuity is often
brutal, irreversible and bilateral in 25 to 50% of cases. The mechanism of this blindness is
an arterial ischemia: Acute Anterior Ischemic Optic Neuropathy acute anterior ischaemic optic
neuropathy (90%), acute retro-bulbar ischaemic optic neuropathy (5%), occlusion of the
central artery of the retina (5%).
The pathogenesis of this brutal ischemia is not fully understood. One of the hypotheses
suggests that, during stimulation by an antigen of the environment, preactivated dendritic
cells of the arterial wall would stimulate T lymphocytes. These will recruit cells that cause
an inflammatory infiltrate polymorphic predominant at the media level. These lesions may be
accompanied by destruction of the internal elastic lamina, with inconstant but pathognomonic
presence of multinucleated giant cells. All arteries with internal elastic lamina can be
affected by parietal inflammation, which results in stenosis and occlusion, explaining the
ischemia.
The visual loss is usually abrupt and very severe, leaving the patient with definitely very
low or no residual visual acuity.
Conventional treatment currently recommended includes systemic corticosteroid therapy at 1 mg
/ kg / day, preceded or not by 500 mg pulses of methylprednisolone , and associated with
antiplatelet and anticoagulant therapy (LMWH). Despite the decline in visual acuity thus
occurred is then always final. Certainly loss of vision has a major impact on the quality of
life of patients.
Apart from this lymphocytic inflammation, a process of vascular remodeling is at the origin
of the vascular occlusion phenomenon. The endothelin system is a family of amino acids
including 3 members: ET1, ET2 and ET3. ET1 is a potent vasoconstrictor. ET1 receptors (ETA
and ETB) are expressed in the arteries of patients with giant cell arteritis . The expression
of ET1 associated with proliferation of muscle cells in arteries will decrease under the
effect of endothelin inhibitors. This has been shown during treatment of pulmonary
hypertension. In giant cell arteritis , the endothelin system continues to be very active up
to 8 days despite the introduction of systemic corticosteroids. Bosentan is a mixed
endothelin receptor antagonist with affinity for both ETA and ETB receptors. This inhibitor
is used in treatment of pulmonary artery hypertension, digital ulcerations of systemic
sclerosis and critical peripheral arterial ischemia.
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