Vitrectomy an option for some cases of DME

Royal Oak, MI-Vitrectomy should be considered for some eyes with diffuse diabetic macular edema (DME). The procedure seems to be a long-term efficacious treatment in some eyes, according to Tarek S. Hassan, MD.

"We know from 13 years of published data that vitrectomy and peeling of the posterior hyaloid membrane, with or without internal limiting membrane (ILM) peeling, can lead to visual improvement in eyes with diffuse clinically significant DME that was previously thought to be refractory to treatment," said Dr. Hassan, who is co-director, Vitreoretinal Program, Associated Retinal Consultants, Royal Oak, MI, and assistant professor of biomedical sciences, Oakland University, Rochester, MI.

Five small, uncontrolled studies published between 1992 and 2000 showed that visual improvement and resolution of DME is seen in half to nearly all eyes with a visibly taut, opacified posterior hyaloid membrane following vitrectomy and membrane peeling. Ten similar series carried out between 1996 and 2005 reported that vitrectomy for eyes with an attached but not clinically visible taut posterior hyaloid membrane could also achieve substantial visual improvement. This improvement could be as great as two or more lines of vision and resolution of the macular edema from 40% to nearly all eyes following vitrectomy and posterior hyaloid stripping.

As seen in studies over the past 2 years, substantial visual improvements can also be achieved with vitrectomy in eyes with large submacular cysts, tangential traction, and massive subfoveal hard exudates, which do not respond to systemic or laser treatment, according to Dr. Hassan.

The mechanism of vitrectomy

There are questions about how vitrectomy works in these eyes, though it is likely that several mechanisms play a role. Evidence suggests that vitrectomy relieves the anteroposterior vitreomacular traction by creating a posterior vitreous detachment (PVD), Dr. Hassan explained, and this results in reduction of DME.

In 1988, Nasrallah and colleagues reported that in eyes with a PVD there was less macular edema compared with eyes without one. Hikichi and associates in 1997 reported spontaneous resolution of DME in many more eyes that developed PVDs than in those that did not when followed over time. In addition, it is known that vitreoschisis occurs often; Schwartz and associates reported in 1996 that vitreoschisis was present in 81% of 179 eyes with proliferative diabetic retinopathy and tractional retinal detachment, Dr. Hassan recounted.

"Vitreoschisis exists and is likely underdiagnosed in these eyes with a similar mechanism of traction of the posterior hyaloid," he emphasized.

Vitrectomy relieves tangential traction as well. An electron microscopy study by Jumper and colleagues reported in 2000 showed contractile multiple vitreous and retinal pigment epithelial cells in multilayered sheets on posterior hyaloid tissue that had been removed in eyes with refractory DME.

The ILM likely plays an important role and its removal seems to improve visual and anatomic outcomes, facilitate faster resolution of DME, and lower the recurrence rate of DME, as reported by Gandorfer in 2000. Results from a 2001 study by Yamamoto and colleagues did not concur with that previous study, Dr. Hassan pointed out.