Examining various imaging approaches for macular edema

Ann Arbor, MI-As the final common pathway in many retinal disorders, macular edema can be considered the leading cause of visual loss in the developed world, and thus has an enormous socioeconomic importance, according to Mark Johnson, MD.

A rational therapeutic approach to macular edema, Dr. Johnson said, depends on identifying and treating all underlying pathophysiologic-possibly multifactorial-mechanisms in the patient history, evaluation, and by prudent use of imaging technologies. These mechanisms include:

·      Increased vascular permeability.

·      Retinal blood flow.

·      Dysfunctional retinal pigment epithelial barrier/pump.

·      Tractional stress.

·      Drug reactions.

·      Fluid migration from the optic disc.

“Tailoring the therapy to specific causative factors in a given patient is not only more effective, but also avoids the cost and risk of unnecessary treatments,” said Dr. Johnson, professor, Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, Ann Arbor.

In inflammatory disorders, iris angiography is useful for distinguishing between diabetic macular edema and pseudophakic cystoid macular edema (CME), he said. The angiography identified leakage from iris vessels, which suggested a pseudophakic component that was successfully treated with a non-steroidal anti-inflammatory drug with macular edema resolution.

In retinal vascular disease, widefield fluorescein angiography has been used increasingly to assess the perfusion status of the peripheral retina. Extensive ischemia throughout the retina and capillary nonperfusion in the far periphery, which may not be visualized otherwise, can then be treated appropriately, Dr. Johnson commented.

In patients whose macular edema is unresponsive to anti-vascular endothelial growth factor drugs, enhanced-depth optical coherence tomography (OCT) imaging of the choroid can identify central serous maculopathy and facilitate appropriate treatment.

Drug reactions may or may not be accompanied by angiographic leakage.

“Angiography can be helpful in exploring CME caused by drug reactions,” Dr. Johnson said.

In cases with traction macular edema, fluorescein angiography is useful to identify the absence of vascular leakage. OCT demonstrates the traction mechanism, the size of the vitreous adhesion, and the presence of an epiretinal membrane and its relationship to the vitreous.

Finally, in patients with cavitary disc anomalies, OCT can show the route of fluid migration, guide treatment, and assess therapeutic responses. The technology can also provide insight into the pathogenesis of the responsible pressure gradients when vitreous is pulled into the pit, Dr. Johnson concluded.

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