Eales disease is a rare eye condition that can significantly affect vision. It involves inflammation and blockage of blood vessels within the retina, the light-sensitive tissue at the back of the eye. This disorder can lead to various visual impairments, ranging from subtle changes to severe vision loss.
Understanding Eales Disease
Eales disease is an inflammatory condition that primarily affects the retinal blood vessels, particularly the veins, a process known as periphlebitis retinae. This inflammation can lead to the narrowing or occlusion of these vessels, impairing blood flow to parts of the retina. Over time, this reduced blood supply can trigger the growth of new, fragile blood vessels, a process called neovascularization. These new vessels are prone to leakage and rupture, often resulting in bleeding into the retina or the vitreous humor, the clear gel that fills the eye.
The condition was first described by Henry Eales in 1880 and is considered idiopathic, meaning its exact cause is unknown. It commonly affects young adults and is observed more frequently in males, with some studies reporting up to a 20:1 male-to-female ratio. Eales disease is particularly prevalent in the Indian subcontinent, though cases occur globally.
Recognizing the Signs
The initial signs of Eales disease can be subtle, with some patients being asymptomatic in the early stages of retinal perivasculitis. As the disease progresses, individuals may notice floaters, which appear as cobweb-like figures or small specks drifting across their vision. Blurred vision is also a common early symptom, often fluctuating in severity.
More severe manifestations include sudden and significant vision loss, which frequently occurs due to vitreous hemorrhage. Patients may also experience photopsia, or flashes of light. While Eales disease can initially affect one eye, it often progresses to involve both eyes. Other signs observed during eye examinations can include visible inflammation of retinal blood vessels and, in advanced stages, retinal detachment or epiretinal membranes.
Diagnosing Eales Disease
Diagnosing Eales disease involves a comprehensive eye examination and a process of exclusion to rule out other conditions with similar symptoms. A detailed history, including ocular and systemic health, is a part of this process. Specialized imaging techniques are then employed to visualize the retinal blood vessels and assess for abnormalities.
Fundus fluorescein angiography (FFA) is a common diagnostic tool that involves injecting a dye into the bloodstream to highlight the retinal vasculature. This allows ophthalmologists to identify areas of retinal periphlebitis, as well as areas of capillary non-perfusion and neovascularization. Optical coherence tomography (OCT) provides high-resolution cross-sectional images of the retina, which can reveal macular edema, intraretinal fluid, subretinal fluid, and vitreoretinal traction. If the view of the retina is obscured by significant vitreous hemorrhage, B-scan ultrasonography may be used to assess the posterior segment and detect complications like retinal detachment.
Treatment Approaches
Treatment for Eales disease aims to preserve vision and prevent further complications, with approaches varying based on the disease stage. For active inflammation, corticosteroids are often the first line of medical therapy, administered orally, through periocular injections, or intravitreally to reduce retinal vasculitis. In cases where corticosteroids are insufficient or cause unacceptable side effects, immunosuppressive agents such as azathioprine or methotrexate may be considered.
Laser photocoagulation is a common intervention for areas of retinal ischemia and neovascularization. This procedure uses a laser to ablate ischemic retinal tissue, reducing new, fragile blood vessel growth and the risk of hemorrhage. Pan-retinal photocoagulation may be performed for more widespread neovascularization. Additionally, intravitreal injections of anti-VEGF (vascular endothelial growth factor) agents can be used to inhibit the growth of new blood vessels and reduce vascular leakage.
For severe complications like persistent vitreous hemorrhage or retinal detachment, vitreoretinal surgery, such as vitrectomy, is often necessary. This surgical procedure involves removing blood and fibrovascular tissue from the vitreous cavity to restore vision and reattach the retina. Early vitrectomy may improve visual outcomes in patients with recurrent vitreous hemorrhages.
Exploring Potential Causes
The precise cause of Eales disease remains unknown. However, ongoing research suggests a multifactorial etiology involving a complex interplay of genetic, environmental, and immunological factors. One prominent theory proposes a possible hypersensitivity reaction to tuberculoprotein after exposure to Mycobacterium tuberculosis. While this association has been suggested historically, it is not a direct infection of the eye, and the definitive link is still debated.
Immunological studies have indicated the involvement of an abnormal immune response, potentially triggered by various antigens, contributing to the pathogenesis of the disease. Genetic predispositions, including certain human leukocyte antigen (HLA) types, and factors like oxidative stress have also been explored as potential contributors to the disease’s development.