A 61-year-old man with medical history of type 2 diabetes that presents a macular edema, evidenced by anOCT (the edema marked with arrows). The central image is a 3D reconstruction of the retinal thickness (the edema is coloured in red).
Diabetic macular edema, with hard exudates surrounding the blood vessels.
Macular edema occurs when fluid andprotein deposits collect on or under themacula of theeye (a yellow central area of theretina) and causes it to thicken and swell (edema). The swelling may distort a person's centralvision, because the macula holds tightly packedcones that provide sharp, clear, central vision to enable a person to see detail, form, and color that is directly in the centre of thefield of view.
The causes of macular edema are numerous and different causes may be inter-related.
It is commonly associated withdiabetes. Chronic or uncontrolled diabetes type 2 can affect peripheral blood vessels including those of the retina which may leak fluid, blood and occasionally fats into the retina causing it to swell.[2]
Age-relatedmacular degeneration may cause macular edema. As individuals age there may be a natural deterioration in the macula which can lead to the depositing ofdrusen under the retina sometimes with the formation of abnormal blood vessels.[3]
Replacement of thelens as treatment forcataract can cause pseudophakic macular edema ('pseudophakia' means 'replacement lens'), also known asIrvine–Gass syndrome. The surgery involved sometimes irritates the retina (and other parts of the eye) causing the capillaries in the retina to dilate and leak fluid into the retina. This is less common today with modern lens replacement techniques.[4]
Blockage of a vein in the retina can cause engorgement of the other retinal veins causing them to leak fluid under or into the retina. The blockage may be caused, among other things, byatherosclerosis,high blood pressure andglaucoma.[6]
A number of drugs can cause changes in the retina that can lead to macular edema. The effect of each drug is variable and some drugs have a lesser role in causation. The principal medications known to affect the retina arelatanoprost,epinephrine,rosiglitazone,timolol andthiazolidinediones among others.[7][8]
Cystoid macular edema (CME). There are intraretinal cystoid spaces
Cystoid macular edema (CME) involves fluid accumulation in the outer plexiform layer secondary to abnormal perifoveal retinal capillary permeability. The edema is termed "cystoid" as it appears cystic; however, lacking an epithelial coating, it is not truly cystic. The cause for CME can be remembered with the mnemonic "DEPRIVEN" (diabetes, epinepherine, pars planitis, retinitis pigmentosa, Irvine-Gass syndrome, venous occlusion, E2-prostaglandin analogues, nicotinic acid/niacin).[citation needed]
Diabetic macular edema (DME) is similarly caused by leaking macular capillaries. DME is the most common cause of visual loss in both proliferative, and non-proliferativediabetic retinopathy.[9]
Macular edema sometimes occurs for a few days or weeks (sometimes even much longer) aftercataract surgery, but most such cases can be successfully treated withNSAID orcortisoneeye drops. Prophylactic use ofNonsteroidal anti-inflammatory drugs has been reported to reduce the risk of macular edema to some extent.[10] Higher frequency use of topical steroids provides benefit in difficult to treat cases.[11]
Diabetic macular edema may be treated with laser photocoagulation, reducing the chance of vision loss.[12]
Iluvien, a sustained release intravitreal implant developed byAlimera Sciences, has been approved in Austria, Portugal and the U.K. for the treatment of vision impairment associated with chronic diabetic macular edema (DME) considered insufficiently responsive to available therapies. AdditionalEU country approvals are anticipated.[14]
On July 29, 2014, Eylea (aflibercept), an intravitreal injection produced byRegeneron Pharmaceuticals Inc., was approved to treat DME in the United States.[17] On January 28, 2022, Vabysmo, a different injectable eye medication produced by Genentech was approved to treat both Wet AMD and DME in the United States.[18]
Another Cochrane Review examined the effectiveness and safety of two intravitreal steroid treatments,triamcinolone acetonide anddexamethasone, for patients with from CRVO-ME.[21] The results from one trial showed that patients treated with triamcinolone acetonide were significantly more likely to show improvements in visual acuity than those in the control group, though outcome data was missing for a large proportion of the control group. The second trial showed that patients treated with dexamethasone implants did not show improvements in visual acuity, compared to patients in the control group.[citation needed]
Intravitreal injections and implantation of steroids inside the eye may result in a small improvement of vision for people with chronic orrefractory diabetic macular edema.[22] There is low certainty evidence that there does not appear to be any additional benefit of combininganti-VEGF and intravitreal steroids when compared to either treatment alone.[23]
Anti‐tumour necrosis factor agents have been proposed as a treatment for macular oedema due to uveitis but a Cochrane Review published in 2018 found no relevant randomised controlled trials.[24]
^'Oedema' is the standard form defined in theConcise Oxford English Dictionary (2011), with the precision that the spelling in the United States is 'edema'.
^Campochiaro PA, Han YS, Mir TA, Kherani S, Hafiz G, Krispel C, Liu TY, Wang J, Scott AW, Zimmer-Galler (June 2017). "Increased Frequency of Topical Steroids Provides Benefit in Patients With Recalcitrant Postsurgical Macular Edema".Am. J. Ophthalmol.178:163–175.doi:10.1016/j.ajo.2017.03.033.PMID28392176.
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