Macular Edema

What is Macular Edema?

Macular edema is an eye condition that occurs when fluid builds up in the central part of the retina, the part of the eye responsible for clear, straight-ahead vision. This tends to occur along with other eye diseases like diabetic retinopathy, retinal blood vessel blockages, and uveitis. Over time, this fluid accumulation can cause blurry vision or severe vision loss if left untreated. This build up happens when there’s an imbalance in the fluid going in and out of the retina, causing proteins and other substances to enter the retinal tissue.

The macula, the central part of the retina, has unique features that make it prone to fluid accumulation. For example, it has lots of light-sensitive cells, high energy needs, and limited ability to absorb excess fluid due to a central area without blood vessels. It also has specific cells like Müller cells and systems that make it act as a storage for fluid retention.

People with macular edema may often experience symptoms such as distortion in vision (metamorphopsia), seeing objects as smaller than they are (micropsia), blurry vision, a dark spot in the central vision (central scotoma), and decreased color or contrast sensitivity. Diagnosing macular edema can be challenging, especially in patients with mild disease or when the back of the eye isn’t easily seen. Doctors often use imaging tests like fundus fluorescein angiography (FFA), which is a dye test, and optical coherence tomography (OCT), which is like an ultrasound for the eye, to help identify the disease. The good news is the vision changes caused by macular edema can often be managed or even reversed with the right treatment.

There are several treatment options for macular edema, and the choice depends on what is causing the fluid build up. These may include therapies that target growth factors in blood vessels, corticosteroids, anti-inflammatory medications, or even surgery. These treatments primarily aim to manage the substances and processes causing the disruption in the retina.

What Causes Macular Edema?

Macular edema happens primarily because of increased leakage from damaged blood vessels in the retina, the part of the eye that senses light. New, abnormal blood vessels can grow deep in the retina and these don’t have normal tight junctions so they can leak serum from the bloodstream into the retina. Another reason is the breakdown of the blood-retinal barrier, which helps prevent substances in the blood from entering the retina.

Other key reasons for macular edema are diabetes, blockages in the retinal veins (branch and central retinal vein occlusion or RVO), abnormal growth of new blood vessels beneath the retina (choroidal neovascularization), inflammation at the back of the eye (posterior uveitis), inflammation after surgery, and central serous chorioretinopathy, a disease that causes fluid build-up under the retina.

Added to these, Coats disease (a rare eye disorder), retinal artery macroaneurysms (large bulges in the arteries of the retina), radiation retinopathy (damage to the retina caused by exposure to radiation), high blood pressure related eye disease (hypertensive retinopathy), inflammation disorders, certain medications, tumors in the layer of blood vessels at the back of the eye (choroidal tumors), retinitis pigmentosa (a group of rare genetic disorders affecting the retina), nonarteritic anterior ischemic optic neuropathy (NAION, a condition caused by loss of blood flow to the optic nerve), and Irvine-Gass syndrome can also cause macular edema.

Other conditions like acute central serous chorioretinopathy (a disease causing fluid accumulation under the retina), polypoidal choroidal vasculopathy (an abnormality in the blood vessels under the retina), uveitis (inflammation in the middle layer of the eye), including Vogt-Koyanagi-Harada syndrome, sympathetic ophthalmia (an inflammation of both eyes following trauma), posterior scleritis (inflammation of the back part of the wall of the eye), and choroidal granuloma can cause fluid to build up underneath the center of the retina without any fluid in the retina itself. Also, foveoschisis (splitting of the layers of the retina), with or without fluid under the retina, characterizes optic disc pit maculopathy, a condition that affects the area of the retina that provides sharp, central vision.

Risk Factors and Frequency for Macular Edema

Macular edema, a condition that causes vision loss, is the main issue affecting the sight of working people worldwide who are suffering from diabetic retinopathy. Incidences vary between different kinds of diabetes. For type 1 diabetes, between 4.2% to 7.9% of people are affected, whereas type 2 diabetes affects between 1.4% and 12.8% of individuals. An important point to note is that within 9 years of being diagnosed, 27% of those with type 1 diabetes will develop diabetic macular edema.

When it comes to Retinal Vein Occlusion (RVO), the occurrence of macular edema slightly varies. Central RVO (CRVO) affects about 0.1% to 0.2% of the population, while branch RVO (BRVO) impacts around 0.5% to 2% of individuals. In Canada, the yearly rate of severe vision loss happening because of macular edema linked with BRVO is 0.056%, and for CRVO, it’s 0.021%.

As people age, there’s an increased risk of developing age-related macular degeneration. Each year, it affects about 0.3 per 1000 people aged 55 to 59, and 36.7 per 1000 people who are aged 90 or older. Uveitis, a condition that might cause macular edema, has variable rates depending on the specific type of uveitis. A person’s chance of developing uveitis varies between 10.5 and 52 per 100,000 each year.

Another condition that causes macular edema is Irvine-Gass syndrome, also called pseudophakic cystoid macular edema. It develops after uncomplicated cataract surgery and can be detected in between 0.1% to 2.35% of patients. When these patients are evaluated with certain medical imaging techniques, it’s revealed that up to 30% of those who underwent one type of cataract surgery and 4% to 11% of others who had a different surgical technique developed the condition. Factors that increase the risk of developing this syndrome include having diabetes or high blood pressure, previous eye conditions like diabetic retinopathy and RVO, and certain complications during cataract surgery.

• In a study, around 64% of eyes with Non-Arteritic Ischemic Optic Neuropathy (NAION) showed fluid accumulation near the optic disc.
• The fluid extended to the fovea in 16% of cases.
• However, these numbers might be an underestimate as not all patients with NAION regularly undergo the required medical imaging technique.
• Macular edema was detected in 10% to 50% of patients with retinitis pigmentosa, a genetic disorder that leads to vision loss.

Signs and Symptoms of Macular Edema

Macular edema is a condition that can sometimes result in no noticeable symptoms. However, people with macular edema often report blurry vision, seeing straight lines as warped or bent, or perceiving the world as smaller than it is. It could also lead to vision problems such as seeing a dark spot in the center of your vision or having reduced color sensitivity. The severity of these vision problems can range from mild to severe. For certain conditions like central serous chorioretinopathy, patients usually see dark round or oval spots in the center of their vision.

In cases of Retinal Vein Occlusion (RVO), typical symptoms include problems seeing certain areas in their field of vision or having blurred or grey vision. If this condition affects the major branch of retinal vein (BRVO), symptoms might not be noticeable, or they could experience issues with their peripheral vision. If the central part of the retina or the macula is affected, it could result in blurred central vision. Central Retinal Vein Occlusion (CRVO) and hemiretinal vein occlusion usually presents with sudden, painless, blurry vision.

Coats disease commonly found in young and middle-aged males, is often identified by reduced vision, crossed eyes, or a white color in the pupil. It usually affects one eye and is sometimes a secondary response to past damage to the blood vessels. When examined, it shows fatty deposits beneath the retina along with abnormal blood vessels.

Retinal artery macroaneurysms could lead to sudden vision loss in one eye without any pain. If the central part of the retina is not affected, or if there is no leakage or bleeding from the aneurysm, the patient might not have any symptoms.

Radiation retinopathy normally does not show any symptoms and is usually discovered during an eye examination. When it does show symptoms, it might cause painless vision loss months or years after radiation therapy. Confirmation can be achieved through an extensive eye examination which might reveal swelling of the retina, fatty deposits, tiny aneurysms, and abnormal blood vessels.

Irvine-Gass syndrome is frequently diagnosed in patients who report decreased or blurry vision following cataract surgery. In some cases, swelling of the optic nerve can be found during an eye examination.

Nonarteritic Anterior Ischemic Optic Neuropathy typically presents with vision loss in one eye that occurs over hours to days. Upon examination, doctors might find reduced visual acuity, decreased color vision, a usually hyperemic optic disc, splinter hemorrhages around the optic disc, and a smaller-than-normal optic cup in the unaffected eye.

Testing for Macular Edema

There are various tools used to evaluate macular edema, which is swelling in the part of the eye responsible for detailed vision. Recently, the most common investigative tools have been Optical Coherence Tomography (OCT) and Fundus Fluorescein Angiography (FFA). These tools help doctors assess the condition of the eye and monitor any disease progression. Checking a patient’s eyesight is also important. While it doesn’t directly diagnose macular edema, it plays a significant role in monitoring how the disease is progressing.

The first step in examining macular edema involves using a device called a slit-lamp biomicroscope. This tool allows the doctor to see the extent of thickness and swelling in the macula, identify any fluid-filled areas (cysts), and any deposits (exudates). It can show patterns of cysts in the macula and make changes in visibility due to varying levels of eye fluid noticeable. A three-dimensional perspective is also available through stereoscopic examination, making it easier to identify elevated areas of the retina.

Fundus Fluorescein Angiography is another crucial tool used in identifying diseases in the retina. It uses a fluorescent dye to highlight the blood vessels in the back of the eye. Doctors use FFA to classify different types of diabetic macular edema based on the degree of leakage. Leakage refers to how much dye spilling out from the blood vessels, which helps identify any abnormality in blood vessel behavior. Sometimes leakage of the dye is masked by certain types of edema and can be distinguished by specialized leakage patterns during specific stages of the examination.

Optical Coherence Tomography is a commonly used tool to study macular edema. It uses light waves to take cross-section pictures of the retina, revealing its layers. This tool enables doctors to understand the behavior of fluids within the eye in three dimensions which is crucial for managing diseases. OCT is used to monitor different types of fluid accumulation in the eye, which could be a result of various diseases like age-related macular degeneration, diabetic retinopathy, and others.

For instance, in patients suffering from diabetic macular edema, OCT can show diffuse retinal thickening, which represents an increase in the size of the retinal tissues, cystoid macular edema, showing fluid-filled spaces in the retina, and other symptoms that help doctors determine the best course of treatment. In other diseases like radiation retinopathy or juvenile X-linked retinoschisis, OCT enables doctors to classify and grade the disease based on the extent of macular edema present.

These diagnostic tools are pivotal in the evaluation and management of macular edema and allow doctors to make precise assessments, devise suitable treatment plans, and monitor the disease accurately over time.

Treatment Options for Macular Edema

Macular edema, or swelling of the macula (the center of the retina in the eye), is often treated using a combination of methods. These can include medication, both for the eyes and for the whole body, and in some cases, surgery.

Because macular edema often results from systemic health issues like diabetes, high blood pressure, or inflammation, dealing with those conditions can be the first step in treatment. Research has shown that strict control of blood sugar can delay the onset and progression of diabetic retinopathy, an eye disease caused by diabetes.

The primary treatment for macular edema typically involves injecting anti-VEGF agents into the eye. VEGF, or vascular endothelial growth factor, is a protein that contributes to the development of new blood vessels. Blocking this protein can help reduce swelling in the eye.

Several medications have been used for this purpose, including bevacizumab, ranibizumab, and aflibercept. These medications work by blocking VEGF, helping to reduce swelling in the eye. Research has shown that these treatments can be effective for certain cases of diabetic macular edema, although the specifics of when, how, and in what combination these drugs are used can vary.

Besides these injections, non-steroidal anti-inflammatory drugs (NSAIDs) might be used topically to manage inflammation after cataract surgery, and carbonic anhydrase inhibitors (CAI), could be used to increase fluid transport from the eye.

Ocular lasers are sometimes used to treat macular edema resulting from various diseases, and they’re usually recommended for patients where VEGF treatment didn’t work well. The usage of ocular lasers varies widely depending on the disease and the individual patient, but they generally work by applying intense light to the affected area of the eye..

Another treatment option is intraocular steroids, which are injected directly into the affected eye. The specific steroid used can vary and has included medications like Fluocinolone acetate, Triamcinolone acetonide, and Dexamethasone. These can be very effective, but they also have risks, such as causing cataracts or increasing pressure in the eye.

Choosing the best treatment depends on the patient’s specific condition and individual factors. For certain patients, managing underlying health conditions and taking systemic medications may be enough, but for others, surgery or ocular injections may be necessary. Thus, a step-by-step approach, guided by a qualified ophthalmologist, is crucial to managing macular edema effectively.

What else can Macular Edema be?

When trying to diagnose macular edema, a type of swelling or thickness in the eye’s retina, doctors need to consider a range of other conditions that could cause similar symptoms. These include:

• Vitreomacular traction and epiretinal membrane
• Cystoid macular edema due to Müller cell dysfunction
• Juvenile X-linked retinoschisis
• Foveoschisis
• Hypotony macular edema due to abnormal retinal capillary permeability with reduced eye pressure
• Congenital cavitary disc maculopathy – a catch-all for conditions like optic nerve head pit, morning glory anomaly, optic nerve coloboma, and extra-papillary cavitation
• Chronic central serous chorioretinopathy
• Microcystic macular edema in advanced glaucoma and optic neuropathy
• Berlin edema or commotio retinae
• Macular telangiectasia or idiopathic juxtafoveal telangiectasia
• And, central retinal arterial occlusion

These other conditions need to be thoroughly reviewed and tested for by the doctor to ensure a correct diagnosis.

What to expect with Macular Edema

The future health outcomes of macular edema, a condition where the central part of the eye’s retina (the macula) becomes swollen due to fluid build-up, usually depends on its root cause. Around 33% to 35% of people with diabetic macular edema, a common type, see it naturally clear up within half a year. With newer drugs being developed that can be injected directly into the eye, the outlook for most retinal disorders is now more positive.

Certain signs detected by an eye scanning technology known as OCT can assist in predicting the outlook of macular edema.

One such sign is the ‘disorganization of the inner retinal layers’, which is when the precise layers of the retina’s inner regions can’t be properly told apart in more than half of the central foveal 1-mm zone, a precise spot in the eye. If this disorganization affects half or more of this central foveal spot, it generally means a poor vision outcome.

‘Hyperreflective retinal foci’ are another sign. They point towards the presence of certain materials that leak following a disruption in the tight network of blood vessels in the retina. Their existence indicates a high chance of hard substance deposit under the retina after the resolution of macular edema.

Small, medium, or large ‘intraretinal cystoid spaces’, or hollow spaces in the retina, signify issues with certain supportive cells in the retina. Their size matters. Small ones measure less than 100µm, medium-sized ones range from 101 to 200µm, and large ones are over 200µm. Their location and whether they are also associated with fibrotic (scar tissue related) and inflammatory (inflammation related) material also affect their significance. This material shows up in OCT scans as signals relating to the motion of tiny particles, called Brownian motion. These signals usually vanish with the forming of hard substances. Large cysts usually relate to macular ischemia – a lack of blood flow to the retina, whereas giant cysts can damage to outer regions of the retina leading to worse vision.

The ‘photoreceptor outer segment’, which indicates the length between the junction of the inner and outer parts of the photoreceptors and the retinal pigment epithelium. Shorter lengths often tie to poorer vision.

Lastly, the intact state of the ‘external limiting membrane’ and ‘ellipsoid zone’, which are layers of the retina, indicate the health of photoreceptors and retinal pigment epithelium cells. In short, if these outer retinal layers are healthy, it often means a better visual outcome.

Possible Complications When Diagnosed with Macular Edema

If macular edema is not treated, it could possibly result in permanent loss of vision. Other complications may involve injury to the central retinal tissue, thinning of a region of the retina, a layer of fibrous tissue over the retina, lack of blood supply to the macula, a type of macular hole, and the formation of fibrous tissue in the macula. But, it’s important to note that the different treatment methods also carry their own risks. For example, a treatment method using lasers might accidentally lead to burns in the central area of the retina, the formation of scar-like tissue under the retina or choroidal new vessels. Similarly, injections into the interior of the eye can potentially generate severe problems such as infection inside the eye, along with bleeding in the vitreous part of the eye, blockage of the main artery in the eye, and tears in the retina.

Moreover, medications aiming to inhibit the formation of blood vessels might lead to stroke, inflammation of blood vessels leading to their blockage, and blockage of blood vessels in the retina. Taking corticosteroids may cause cloudiness of the usually clear lens of your eye and lead to glaucoma that is caused by the use of steroids.

Common Side Effects:

• Permanent loss of vision
• Injury to the central retinal tissue
• Thinning of a region of the retina
• Layer of fibrous tissue over the retina
• Lack of blood supply to the macula
• A type of macular hole
• Formation of fibrous tissue in the macula
• Accidental burns in the central area of the retina
• Formation of scar-like tissue
• Choroidal new vessels
• Infection inside the eye
• Bleeding in the interior part of the eye
• Blockage of the main artery in the eye
• Tears in the retina
• Stroke
• Inflammation and blockage of blood vessels
• Blockage of blood vessels in the retina
• Cloudiness of the lens of your eye
• Steroid-induced glaucoma

Preventing Macular Edema

Macular edema is a condition where fluid builds up in a part of the eye called the macula, which can eventually lead to vision loss if it’s not treated. It’s crucial to catch and treat macular edema early on, especially for people who are at risk, to avoid permanent damage to their sight. The American Academy of Ophthalmology suggests that people with type 1 diabetes should have their eyes checked within 5 years of being diagnosed, and those with type 2 diabetes should have their eyes checked right when they’re diagnosed. These regular eye check-ups are particularly important for people with diabetes or a history of RVO (a type of blocked blood vessel in the eye), as these conditions increase the chances of developing macular edema.

If you’re a patient, you should watch out for any changes in your vision like blurriness, blind spots in the center of your vision, or difficulty reading small words, and tell your eye doctor right away if you notice anything different. Keeping your blood sugar, blood pressure, and cholesterol levels under control, as well as stopping smoking, can help reduce your risk of developing macular edema or slow it down if it’s already happening. Also, it’s essential to understand the different treatment options available, such as injections of anti-VEGF (a medicine that can help stop the fluid buildup) or corticosteroid (a type of medicine that reduces inflammation), and laser therapy. Remember, sticking to the treatment plan given by your doctor is critical to protect your sight. By taking an active role in managing your health and staying informed about your eye health, you can effectively handle your condition and reduce the effect of macular edema on your daily life.