Cystic Macular Edema - Causes, Clinical Presentation, and Treatment

Introduction

Cystic macular edema is a vision-threatening condition characterized by the thickening of the retinal macula due to fluid accumulation in the interstitial spaces due to disruption in the normal retinal blood flow. The edema or accumulation of fluid in the macular region leads to loss of central vision.

What Are the Causative Factors of Cystic Macular Edema?

The macula is part of the ocular retina. It is present in the back of the eye and shows the presence of multiple photoreceptor cells. These photoreceptor cells help to detect light. The macula of the retina aids in seeing the finer details of an object and also is responsible for central vision. In contrast, the other parts of the retina are responsible for peripheral vision.

The factors that are responsible for causing cystic edema of the macula are:

• Vitreomacular Traction: It is the detachment of the vitreous or gel-like substance that detaches and tugs with the eye's macula. The vitreous traction results in the release of several inflammatory factors resulting in the breakdown of the retinal-blood barrier.

• Separating the retinal pigment epithelium (RPE) and the retina may also lead to this condition.

How Does Cystic Macular Edema Develop?

Cystic macular edema chiefly occurs due to disturbances in the homeostatic mechanism involving the retina, vitreous, retinal pigment epithelium, and choroid region. As a result, the intrinsic balance of the retinal vasculature comprising the osmotic force, hydrostatic pressure, capillary permeability, and tissue compliance is disturbed. This results in fluid accumulation in the retina's inner layers, especially the outer plexiform layer (OPL).

What Are the Risk Factors for Cystic Macular Edema?

The most common risk factors that are responsible for the development of cystic macular edema are:

• Diabetes.

• Application of Epinephrine.

• Inflammation of uvea.

• Retinitis pigmentosa.

• Occlusion of the central retinal vein.

• Side effects of drugs.

• Trauma to the eyes.

• Greater doses of niacin acid and prostaglandin.

• Certain surgeries like laser photocoagulation, cryopexy (retinal surgery using cold to freeze the retinal tissues), and glaucoma surgeries.

What Are the Clinical Presentations of Cystic Macular Edema?

Cystic macular edema can be divided into two types based on the duration of the condition.

• Acute cystic macular edema remains for three to four months.

• Chronic cystic macular edema is a condition that stays for more than six months (approximately six to nine months).

Patients with cystic macular edema mostly remain asymptomatic but might experience blurred vision. The signs and symptoms that are commonly associated with cystic macular edema are:

• Decreased visual acuity.

• Edema of the retinal issues.

• Lack of contrast sensitivity.

• Loss of color vision.

• Central scotoma (the presence of a blind spot in the central vision).

• Metamorphosis or distorted vision of the shape of the objects.

How Are Patients With Cystic Macular Edema Diagnosed?

Clinical examination, history taking, and imaging can diagnose patients with cystic macular edema.

1. Clinical Examination: Clinical examination reveals inflammation of the vitreous region and the optic nerve head swelling. In addition, the slit-lamp technique or indirect ophthalmoscopy shows foveal edema and thickening of the retina by more than 300 micrometers.

2. Diagnostic Imaging:

• Optical coherence tomography reveals retinal thickening with intraretinal cystic areas. In addition, it provides high-resolution images of the retina.

• Color fundus photography (CFP) reveals intraretinal cysts in the fovea region, especially in the Henle's layer.

• Fluorescein angiography reveals the blood circulation of the retinal blood vessels. The dilation of the blood vessels in the perifoveal region is diagnosed in the initial stages.

• Autofluorescence imaging helps detect the health of the retinal pigment epithelium and intraretinal cysts.

• A retinal thickness analyzer helps detect the retina's three-dimensional images or maps.

How Are Patients With Cystic Macular Edema Treated?

The treatment of cystic macular edema primarily depends on the underlying cause. Acute cases get resolved within a few months. However, chronic cases may require surgical and medical management.

1. Medical Management of Cystic Macular Edema:

• Topical and systemic non-steroidal anti-inflammatory drugs (NSAIDs) like Indomethacin, Ketorolac, and others inhibit the production of proinflammatory substances like prostaglandin.

• Corticosteroids, when administered via topical, systemic, and intravitreal route, helps in reducing the expression of proinflammatory chemicals. Steroid implants can also be placed to help in reducing inflammation. Dexamethasone implants and Triamcinolone acetonide implants are the most commonly used.

• Carbonic anhydrase inhibitors help prevent fluid accumulation by altering the ionic channels in the interstitial places.

• Anti-vascular endothelial growth factors (anti-VEGF) Ranibizumab decreases the permeability of the vascular tissues.

• Pharmacologic vitreolysis agents like Microplasmin induce detachment of the vitreous membrane.

2. Surgical Management of Cystic Macular Edema:

• Pars plana vitrectomy procedures (PPV) can be performed to relieve the edema of the macular region. In addition, the posterior hyaloid is released in the procedure for correcting the traction present in vitreomacular traction (VMT). Surgeries are performed in refractory cases or patients who do not respond to medical therapy.

• Vitrectomy procedures following PPV help improve visual acuity. In addition, tractional elements of the disease can be treated with surgeries, while non-traction components can be cleared with anti-inflammatory therapies.

What Are the Complications of Cystic Macular Edema?

The major complication of cystic macular edema is the loss of central vision. The treatment of the condition can also lead to further complications, such as:

• Vitrectomy leads to cataracts, retinal detachment, glaucoma, and hemorrhage.

• Long-term use of steroids can also result in cataracts and glaucoma.

Overall, cystic macular edema is a self-limiting condition that gets resolved spontaneously within three to four years. However, the final outlook of the condition depends on the underlying areas. In chronic cases, it can lead to permanent vision damage.

Conclusion

Cystic macular edema is a vision-threatening ocular condition characterized by an imbalance in the retinal-blood barrier. The fluid leakage from the blood vessels into the retinal interstitial place and the macula results in loss of central vision. VMT is the primary cause of the state and is aggravated by several risk factors, including diabetes, trauma, and medicines. Patients with CME mainly complain of blurry vision and further progressive vision loss. Imaging and clinical examination help in diagnosing the condition. Acute CME does not require treatment, while chronic cases can be treated with medical and surgical management.