Optical coherence tomography (OCT) is valuable in managing diabetic macular edema (DME), more so than fluorescein angiography, in which the degree of leakage is not correlated with visual acuity and outcomes, according to Peter Kaiser, MD. In addition, angiography does not show vitreoretinal abnormalities that may require a different treatment.

OCT provides a retinal thickness map that correlates well with leakage clinically, fluorescein leakage, and more importantly, with decreased visual acuity. The maps can be used to track progression and treatment efficacy, according to Dr. Kaiser, of the Cole Eye Institute, Cleveland Clinic.

The OCT single scan tomograms identify specific patterns in patients with DME.

"The patterns may have different prognoses and require different management," Dr. Kaiser said. "It is important to recognize the patterns on OCT."

The sponge-like pattern is the one most commonly seen in which the inner layers of the retina appear to be compressed as the result of fluid absorption. This pattern responds well to laser treatment.

Cystoid macular edema is characterized by cysts that grow and coalesce and are associated with worse visual acuity than with the sponge-like pattern; this responds to steroids and anti-vascular endothelial growth factor drugs.

Serous retinal detachment without posterior hyaloidal traction is characterized by serous fluid in the fovea not seen on ophthalmoscopy; treatment and absorption of the fluid often leads to the hard exudates deposits in the subretinal space.

Posterior hyaloidal traction leading to DME seems to be a distinct subgroup of patients. The traction is subtle but can be identified by sheen on clinical examination.

Traction can cause a traction retinal detachment in a few patients. If there is traction that is more tangential resulting from the hyaloidal traction, it can be very subtle.

A retinal detachment can occur without traction; this does not respond to laser or medical therapy but requires vitrectomy.

"There are six morphologic patterns on OCT of DME that may represent distinct entities that require different treatment regimens," Dr. Kaiser said. "Identifying the patterns allows more effective management of these patients."