Mechanisms of macular edema: Beyond the surface

Prog Retin Eye Res. 2018 Mar;63:20-68. doi: 10.1016/j.preteyeres.2017.10.006. Epub 2017 Nov 7.


Macular edema consists of intra- or subretinal fluid accumulation in the macular region. It occurs during the course of numerous retinal disorders and can cause severe impairment of central vision. Major causes of macular edema include diabetes, branch and central retinal vein occlusion, choroidal neovascularization, posterior uveitis, postoperative inflammation and central serous chorioretinopathy. The healthy retina is maintained in a relatively dehydrated, transparent state compatible with optimal light transmission by multiple active and passive systems. Fluid accumulation results from an imbalance between processes governing fluid entry and exit, and is driven by Starling equation when inner or outer blood-retinal barriers are disrupted. The multiple and intricate mechanisms involved in retinal hydro-ionic homeostasis, their molecular and cellular basis, and how their deregulation lead to retinal edema, are addressed in this review. Analyzing the distribution of junction proteins and water channels in the human macula, several hypotheses are raised to explain why edema forms specifically in the macular region. "Pure" clinical phenotypes of macular edema, that result presumably from a single causative mechanism, are detailed. Finally, diabetic macular edema is investigated, as a complex multifactorial pathogenic example. This comprehensive review on the current understanding of macular edema and its mechanisms opens perspectives to identify new preventive and therapeutic strategies for this sight-threatening condition.

Keywords: Cysts; Diabetes; Edema; Macula; Mechanisms; Retina.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Blood-Retinal Barrier
  • Central Serous Chorioretinopathy / complications
  • Central Serous Chorioretinopathy / physiopathology
  • Choroidal Neovascularization / complications
  • Choroidal Neovascularization / physiopathology
  • Diabetic Retinopathy / complications
  • Diabetic Retinopathy / physiopathology
  • Fluorescein Angiography
  • Humans
  • Macular Edema / diagnosis
  • Macular Edema / physiopathology*
  • Macular Edema / prevention & control
  • Retinal Vein Occlusion / complications
  • Retinal Vein Occlusion / physiopathology
  • Retinal Vessels / physiopathology
  • Subretinal Fluid
  • Tomography, Optical Coherence