Introduction
Macular edema is an ocular condition characterized by fluid filling up inside the macula of the eyes—the accumulation of the fluid results in the thickening of the macula and distortion of the vision. According to the International Classification of Diseases (ICD), the code for macular edema is H59.033.
How Common Is Macular Edema of the Eye?
The macula of the eyes is the centermost part of the retina responsible for sharp and clear vision. In addition, the eye's retina contains millions of photoreceptor cells that aid in visualizing objects.
Macular edema is common, with diabetic macular edema being one of the most common outcomes of diabetic retinopathy. The prevalence of diabetic macular edema is around 3.8 percent in the United States of America.
What Are the Causes of Macular Edema of the Eyes?
Macular edema of the eyes is caused due to numerous factors, such as:
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Diabetic retinopathy.
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Age-related degeneration of the macula.
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After cataract surgery.
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Inflammatory conditions of the eye structures like uveitis, scleritis, iritis, etc.
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Conditions affecting the eyes' blood vessels, including retinal vein occlusion.
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Tumors of the eye.
Various drugs can cause cystoid macular edema of the eyes, also known as drug-induced macular edema. Drugs that are administered both locally and systemically have been considered to be responsible for causing macular edema. Prostaglandins, epinephrine, Timolol, Niacin, interferons, etc., are the few drugs that can cause macular edema.
What Are the Risk Factors Associated With Macular Edema?
The trigger for the initiation and progression of the edema inside the macula is the damage caused to the retinal blood vessels. The destruction of the retinal arteries and veins results in fluid leakage from the damaged vessels that get filled inside the macula. The resultant thickening of the macula ultimately impairs vision.
The risk factors which aggravate or increase the chances of macular edema are:
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Diabetes (increased blood sugar levels).
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Dyslipidemia (lipid imbalance).
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Hypertension (increased blood pressure).
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Neuropathy (damage to the nerves).
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Anemia (decreased red blood cells).
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Sleep apnea (a type of serious sleep disorder).
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Glitazone usage.
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Pregnancy.
What Are the Clinical Manifestations of the Macular Edema of the Eyes?
The two major types of macular edema are:
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Diabetic Macular Edema (DME): Diabetic macular edema typically represents the swelling and fluid buildup inside the macula due to diabetic retinopathy.
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The cystoid macular edema (CME): The fluid accumulation inside the macula in a cyst-like pattern is known as cystoid macular edema.
Patients suffering from macular edema chiefly complain of blurring of vision, especially in the center of the eye. They also complain of gradual vision loss. Other symptoms include:
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Fading of colors.
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Wavy central vision.
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Difficulty in reading.
How Is Macular Edema of the Eyes Diagnosed?
The diagnosis of the macular edema is confirmed by an ophthalmologist based on the complete medical history, clinical examination, and imaging of the patient with the abnormality. The various tests used in diagnosing macular edema of the eyes are;
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Visual Acuity Test: In this test, the doctor examines the visual acuity of each eye separately by reading the letters in the chart.
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Dilated Eye Examination: The retina is examined thoroughly by dilating the pupils of the eye and examining for any damage caused to the blood vessels.
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Fluorescein Angiography: Fluorescein dye is injected into the arm of the patient, and the blood vessels of the retina are viewed better by taking photos of the eyes.
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Optical Coherence Tomography (OCT): It is a non-invasive imaging modality to view the retina and its surrounding structures in detail. For example, it helps detect the retina's thickness, which is often ignored by the naked eye.
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Amsler Grid: The grid evaluates the patient's central vision.
How Is Macular Edema Treated?
The main principle behind treating macular edema is to remove the underlying cause of the disease. Recently, the main treatment modality for macular edema remains the laser photocoagulation of the damaged blood vessels. However, due to the side effects related to the laser treatment, other treatment modalities are also considered, such as:
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Intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) agents help block the leaky blood vessels and new blood vessel formation.
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Anti-inflammatory drugs like corticosteroids are prescribed systemically and topically to reduce the inflammation of the macula. The most commonly used drugs are extended-release steroids for treating macular edema.
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Non-steroidal anti-inflammatory drugs are given before and after cataract surgery to prevent edema.
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Vitrectomy surgery removes the vitreous humor layer of the eye, especially in cases where the vitreous cause swelling of the eyes by pulling the macula.
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Unfortunately, there is no permanent cure for macular edema. The leaking of the blood vessels remains; however, it can be controlled with treatment.
What Are the Complications of Macular Edema?
If left untreated, macular edema can result in vision-threatening conditions, including complete loss of sight. The most common complications of macular edema are;
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Foveal burns are caused due to laser photocoagulation of the eyes while treating the condition.
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Cataract.
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Vitreous hemorrhage.
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Central artery occlusion.
The conditions that are similar to macular edema of the eyes are:
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Vitreomacular traction.
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Chronic serous chorioretinopathy.
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Berlin edema.
Macular edema of the eyes can occur after cataract surgeries in one to three percent of the population if the eye's blood vessels get damaged. Although, the condition is primarily transient and can be corrected with mild drops.
Does Macular Edema Enjoy a Good Prognosis?
The macular edema of the eyes is a serious complication of numerous systemic and ocular diseases affecting the eye's blood vessels. It can ultimately lead to loss of vision.
The condition's prognosis usually depends on the cause of the disease. However, several prognostic markers help in determining the prognosis of the disease, such as:
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Hyperreflective retinal foci.
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Intraretinal cystoid spaces.
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Photoreceptor outer segment.
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Disorganization of the inner retinal layers.
Conclusion
Macular edema is the most common cause of gradual vision loss. It is more commonly caused by diabetic retinopathy and mainly affects the central vision of the eyes. The lesion can be diagnosed with clinical examination and optical coherence tomography. The treatment of the condition remains laser photocoagulation and steroid therapy.
