What Is Eales Disease?

Introduction

Eales disease is a condition affecting the eyes where the walls of the blood vessels in the retina become inflamed. This inflammation leads to the vessel's narrowing, which causes problems with blood flow and causes new blood vessels to grow. This disease primarily affects young people assigned male at birth who are from the sub-Indian continent.¹ It is characterised by idiopathic (meaning of unknown cause) occlusive vasculitis, which involves the mid-peripheral retina.¹

Background

Most cases of Eales disease are found largely in Asia, most commonly within the Sub-Indian continent and some parts of Africa.¹ There is a higher prevalence of the disease in tropical or subtropical climates.¹ Whilst the disease has been found to mostly affect those assigned male at birth, Eales disease has been reported in both sexes. Most males develop the condition at around 20-30 years of age.¹

Although the exact cause of Eales disease remains unknown, it is believed that some individuals have a genetic predisposition for the condition, and there may also be a range of environmental factors that contribute to the onset of the disease. Smoking has been suggested as a risk factor for developing Eales disease, as evidence has suggested that there is a significant prevalence of Eales disease among those who smoke.¹

Eales disease is considered to be relatively rare, and the number of reported cases varies by region. Whilst on a global scale the disease is very rare, in certain regions it is considered to be fairly common.² In parts of India, it has been reported to be one of the leading causes of inflammation in the retinal blood vessels and of vision loss among young adults, accounting for 1 in 200-250 patients with eye issues.^1,3  The prevalence of Eales disease in many countries appears to be declining, possibly due to better health and living standards.^1,4

Causes and risk factors

The exact cause of Eales disease remains unclear, and it is considered idiopathic, meaning it arises spontaneously or of unknown cause. However, various risk factors have been proposed and studied as potential contributors to the development of Eales disease.¹

Eales disease primarily affects the retinal blood vessels, and vascular abnormalities are the central feature of the disease. Some researchers believe that an initial injury to the retinal vessels triggers a cascade of immune responses, leading to inflammation, retinal haemorrhages, and neovascularisation (development of new blood vessels) seen in Eales disease.¹ There is evidence of immune system involvement in Eales disease; abnormal immune responses, including autoimmune reactions, have been suggested as potential contributors. Inflammation of the retinal blood vessels is a hallmark of the disease and is a key defense mechanism in the immune system.¹

It has been found that many individuals who suffer from the condition have a genetic predisposition to develop Eales disease. A range of genetic factors have been found to play a role in an individual’s susceptibility to the disease. Some research has found that genetic variations related to the immune system and inflammation may increase the risk of developing the condition.⁵ This genetic link would likely explain why the condition is more common in males and in specific regions of the world.

There are several environmental factors thought to contribute to the onset of the disease. People who smoke have been proposed to have a higher risk of developing Eales disease. Other environmental factors include oxidative stress, which can damage blood vessels and cause inflammation, and hormonal imbalances. Hormonal imbalances predominantly affect young adults, which may explain the higher incidence of disease in this age group. Furthermore, several studies have reported an association between exposure to tuberculosis and Eales disease.¹

Despite continuing research, the exact cause of Eales disease is unknown, and it is thought to arise from a combination of the above factors.

Symptoms

Patients who suffer from Eales disease generally have no noticeable symptoms at first. Typically, the first presenting symptoms are caused by what is known as a vitreous haemorrhage, which is blood in the eye caused by damaged blood vessels.³  Patients suffering from vitreous haemorrhage may experience reduced vision in one or both eyes as well as photopsia (flashes of light) and floaters, which are small floating specks in the patient’s vision.³ 

Diagnosis

Diagnosing Eales disease can be challenging because it is a rare eye disorder that has no specific diagnostic test, and it can often be confused with other conditions that exhibit similar symptoms. Diagnosis typically relies on a combination of clinical findings, medical history, and exclusion of other possible causes of retinal inflammation and vasculitis.³ There are several steps a clinician may take in diagnosing Eales disease:

• Clinical Examination: The first step in diagnosing Eales disease is a thorough clinical examination by an ophthalmologist. The doctor will take a detailed medical history and ask about symptoms, including any vision changes or eye discomfort.³
• Fundus Examination: The ophthalmologist will perform a fundus examination, which involves dilating the pupils and using specialized instruments to examine the back of the eye, including the retina and blood vessels.³ This will identify any damage indicative of Eales disease.
• Laboratory Tests: While there is no specific blood test to diagnose Eales disease, blood tests may be performed to rule out other conditions that can mimic its symptoms, such as infectious diseases or autoimmune disorders.
• Rule Out Other Conditions: Eales disease is diagnosed on the basis of exclusion, meaning other possible causes of retinal vasculitis and inflammation must be ruled out before an Eales disease diagnosis can be made. These may include conditions like sarcoidosis, tuberculosis, syphilis, Behçet's disease, and others.
• Medical History and Risk Factors: The ophthalmologist will also consider medical history and any potential risk factors, such as whether the patient is or has been a smoker, as this is sometimes associated with Eales disease.¹

It's important to understand that Eales disease is rare, and its diagnosis can be complex. There are often many diagnostic challenges involved because the disease shares similarities with other retinal disorders, and there is no specific diagnostic test. Diagnosis is typically based on clinical findings, such as retinal haemorrhages, inflammation, and the exclusion of other possible causes.

Treatment

Treatment of Eales disease aims to control inflammation, manage complications like retinal neovascularisation, and preserve vision. A key aim of Eales disease treatment and management is to avoid further vitreous haemorrhage to preserve vision and avoid further complications.³ Treatment options may include:

• Corticosteroids: These anti-inflammatory medicines can be taken orally or through the eye (periocular) and are often given at a high dosage when the condition is first diagnosed,  and then the dosage is decreased as the vasculitis improves.³ This treatment is typically very effective and has been shown to improve symptoms greatly.³
• Vitrectomy: Healthcare providers may opt for a vitrectomy (removal of the vitreous humour, jelly-like fluid in the eye) when vitreous haemorrhage does not improve with other treatments or when the case is very severe and has done significant damage to the eye.³ The prognosis following this treatment is usually very positive and usually greatly improves vision.³
• Immunosuppressive medications: These are occasionally considered but typically the response to corticosteroids is sufficient and further treatment with immunosuppressive drugs is not needed.¹
• Laser therapy: Laser therapies such as photocoagulation are commonly used to treat Eales disease; 95% of patients in an Eales disease study underwent Laser photocoagulation.³

The outcome of treatment is greatly improved when the condition is diagnosed and treated early; the further the disease progresses before receiving the treatment, the poorer the prognosis.2 It is important to understand that research on Eales disease is still ongoing, and there needs to be a deeper understanding of its epidemiology and underlying causes. Given its rarity, large-scale epidemiological studies are limited, and the information available may not fully represent the global prevalence and distribution of the disease.

Summary

In conclusion, Eales Disease is a rare condition characterised by inflammation of the retinal blood vessels, primarily affecting young people assigned to males from the sub-Indian continent at birth. While its exact cause remains unclear, a combination of genetic predisposition, environmental factors such as smoking, oxidative stress, hormonal imbalances, and immune system abnormalities may contribute to its development.

Diagnosing Eales disease can be challenging due to its rarity. Diagnosis relies on clinical examination, fundus examination, laboratory tests, and the exclusion of other potential causes of retinal inflammation. The treatment aims to control inflammation, manage complications, and preserve vision through corticosteroids, immunosuppressive medications, or laser therapy.

Research on Eales Disease is ongoing, and a deeper understanding of its epidemiology and underlying causes is needed. Given its rarity, large-scale epidemiological studies are limited, and the available information may not fully represent its global prevalence and distribution. Further research is essential to improve our knowledge of this complex disorder.