Angioid Streaks - Causes, Symptoms, Diagnosis, and Management

Introduction

The eyes are considered necessary in a human's body. Without eyes, the quality of life will be highly affected. The eye comprises a number of layers like the conjunctiva, sclera, cornea, anterior chamber, posterior chamber, pupil, lens, iris, vitreous humor, retina, and optic nerve. Each layer is responsible for our vision, and each of them is highly prone to infections and trauma. One of the conditions to be discussed in this article is angioid streaks.

Angioid streaks were first reported in 1889 and are also called Knapp streaks. It is a rare condition caused by trauma or systemic conditions. Angioid streaks present as irregular, radiating lines (looks like blood vessels) from deeper retinal layers and running towards the optic nerve. It is a bilateral condition. This is believed to be caused by a break in the Bruch membrane (a layer between the retinal pigment epithelium and choroid capillaries) of the eye. This membrane is a mediator between the blood flow from the choroid and retinal pigment epithelium. The color of the streaks could be red, orange, gray, or brown and is often mistaken for blood vessels on examination.

What Are the Causes of Angioid Streaks?

Medical Conditions:

• Pseudoxanthoma Elasticum: This is an inherited connective tissue disorder, and its occurrence is rare. It accumulates calcium and mineral deposits on the elastic fibers of the eye. Due to this, minor breaks occur in the Bruch membrane causing angioid streaks. 85 % of people affected with pseudoxanthoma elasticum will develop ocular conditions, and this combination of conditions is called Gronblad-Strandberg syndrome.

• Paget Disease: A condition of bone deformity.

• Ehlers danlos syndrome is a collagen disorder resulting in several eye conditions and angioid streaks being one.

• Acromegaly: Pituitary gland disorder where an excess of growth hormone will be produced.

• Diabetes mellitus.

• Myopia: This is a condition of the eye where the individual can see near objects clearly, but objects farther away look blurry. Myopia occurs when shape of the eye causes light rays to bend or refract inaccurately.

• Epilepsy: This is a neurological condition in which the nerve cell activity in the brain is disturbed leading to seizures.

• Tuberculosis.

• Dwarfism.

• Neurofibromatosis: This is a genetic disorder where tumors are formed on the nerves.

Hemoglobinopathies:

Hemoglobinopathies are a group of inherited blood disorders causing abnormal production of hemoglobin. Some of the conditions causing angioid streaks are,

• Hemoglobin H.

• Sickle cell thalassemia.

• Spherocytosis (the red blood cells are round-shaped instead of disc-shaped and are more fragile than normal red blood cells).

• Sickle cell hemoglobin (hemoglobin will be constricted to a sickle or crescent shape).

How Do Angioid Streaks Occur?

The pathophysiology of angioid streaks is still controversial. There are many theories as to why the Bruch membrane breaks.

• The nature of angioid streaks suggests the intrinsic and extrinsic pull of the elastic eye muscles around the optic nerve site is the cause.

• Due to some systemic conditions’ action of calcium, mineral accumulation, and the Bruch membrane's elastic fibers degeneration, the Bruch membrane is affected by opacities and breaks.

What Are the Symptoms of Angioid Streaks?

Angioid streaks are generally asymptomatic. Only when the streaks extend into the macula (back part of the retinal layer), there are a few symptoms,

• Vision impairment (when it involves the fovea of the eye).

• Choroidal neovascularization (new blood vessels are formed from the choroid layer due to the break-in Bruch membrane).

• Subretinal hemorrhage.

What Are the Possible Complications of Angioid Streaks?

• Subretinal hemorrhage.

• Retinal detachment.

• Atrophy of fovea.

• Choroidal neovascularization.

How to Diagnose Angioid Streaks?

Angioid streaks are generally asymptomatic and cannot be confirmed with a visual examination.

Clinical Evaluation:

A thorough examination of the eye is done by carrying out tests to know,

• Visual acuity.

• Intraocular pressure.

• Ocular motility.

All the layers of the eye are studied if there is a presence of an angioid streak following features are diagnosed.

• Irregular lines originating from the optic disc.

• Jagged lines form a ring-like structure around the optic disc.

• The lines taper towards the retina.

• The margins of the lines are serrated.

• The location of the streaks is subretinal (beneath or deeper retinal layer).

• Streaks are bilaterally present.

Fundoscopy Examination:

Also called ophthalmoscopy which is used by ophthalmologists to study the back of the eye.

• Peau D'Orange's appearance of the fundus is a classic feature of angioid streaks and appears like orange skin. It is a small area of pigmentation found near the retinal pigment epithelium. It is rare in sickle cell conditions and Paget's disease cases.

• Optic Nerve Drusen: Abnormal accumulation of calcium and protein in the optic nerve.

• Subretinal crystalline bodies.

Fluorescein Angiography Test:

This test involves using a dye to study the blood flow in the retinal and choroidal layers.

• Invisible streaks during the visual examination can be seen.

• Hyperfluorescent streaks with hyperfluorescent margins, which in the later stage get stained.

How to Manage Angioid Streaks?

Angioid streaks are asymptomatic in most cases, and observation is only required if complications are not found.

If there is subretinal hemorrhage and choroidal neovascularization is ruled out, the hemorrhage will resolve independently.

If choroidal neovascularization is detected, the patient will undergo,

• Laser photocoagulation.

• Transpupillary thermotherapy (used to treat the tumors by raising their temperature).

• Photodynamic therapy (light-sensitive medicines and a light source are used to kill abnormal cells)

• Anti-vascular Endothelial Growth Factor Therapy: Agents like Ranibizumab and Aflibercept successfully stabilize vision.

Surgical Care:

In the case of subfoveal choroidal neovascularization, photocoagulation therapy is not advised.

In that case, the choroidal neovascularization membrane is removed, and transplantation of the same is carried out in a few instances.

Follow Up:

Follow-up is critical in the case of angioid streaks. Patients who underwent laser treatment will need three months to follow up.

The ones who are asymptomatic will need six months of follow-up and screening.

Prognosis:

Untreated choroidal neovascularization shows a poor prognosis. Proper management is mandatory to ease the condition.

Conclusion

Advising patients with systemic conditions to take up a regular eye checkups can prevent complications to a greater extent. The emerging medical sources for diagnosing and managing angioid streaks are a ray of hope for everyone.