The macula is a very small area at the center of the retina—a thin layer of light-sensitive tissue that lines the back of the eye. Light rays are focused onto the retina, where they are transmitted to the brain and interpreted as the images you see. It is the macula that is responsible for your pinpoint vision, allowing you to read, sew or recognize a face. Macular edema develops when blood vessels in the retina are leaking fluids. The macula does not function properly when it is swollen. Vision loss may be mild to severe, but in many cases, your peripheral (side) vision remains. Macular edema is often a complication of diabetic retinopathy, and is the most common form of vision loss for people with diabetes—particularly if it is left untreated.
SOURCE: American Academy of Ophthalmology
Potential Causes of Macular Edema?
Eye surgery, including cataract surgery, can increase your risk of developing macular edema due to blood vessels becoming irritated and leaking fluids. Macular edema that develops after cataract surgery is called cystoid macular edema (CME).
Some of the other macular edema causes include:
- Age-related macular degeneration
- Retinal vein occlusion
- Blockage in the small veins of the retina, due to radiation, macular telangiectasis
- Side effects of certain medications
- Certain genetic disorders, such as retinoschisis or retinitis pigmentosa
Macular Edema Symptoms
Macular edema can cause:
- a decrease in central vision (peripheral vision is unaffected)
- blurriness / wave-like distortion in the middle of the field of view.
- distortion of colors
- reduced contrast sensitivity.
To treat cystoid macular edema, where the eye is irritated by the presence of a new lens, your ophthalmologist may prescribe non-steroidal anti-inflammatory (NSAID) eyedrops for a few months. If these drops do not help to reduce the edema and improve vision, you may need to use steroid drops. Sometimes, more powerful steroid injections around or even inside the eye may be used. In rare cases, when cystoid macular edema does not respond to drops or shots, vitrectomy surgery may be needed to clear the gel inside the eye. Also, in rare instances, a lens replacement may be required.
Sometimes the swelling in your eye can cause you to have increased pressure within the eye, called glaucoma. In such cases, your ophthalmologist will treat you with medicines to control your glaucoma.
Depending on the cause of the macular edema and the treatment plan your doctor has recommended, the macular edema may take several months to resolve. During this time, it is important to follow the treatment regimen that your ophthalmologist recommends in order for your treatment to be effective.
The American Academy of Ophthalmology Preferred Practice Patterns defines Cystoid Macular Edema (CME) as retinal thickening of the macula due to a disruption of the normal blood-retinal barrier; this causes leakage from the perifoveal retinal capillaries and accumulation of fluid within the intracellular spaces of the retina, primarily in the outer plexiform layer. Vision loss occurs from retinal thickening and fluid collection that distorts the architecture of the photoreceptors. CME is a leading cause of central vision loss in the developed world.