Epiretinal membranes (ERM) form on the inner surface of the neurosensory retina idiopathically and can compromise vision significantly enough to lead patients to seek surgical intervention, such as pars plana vitrectomy with membrane peel. However, procedures to restore the patient’s vision can cause the ganglion cell–inner plexiform layer (GC-IPL) to thin, putting them at higher risk for glaucoma, according to a new study published in the journal Retina.

The authors followed 20 ERM surgery patients for five years to evaluate the functional outcomes of their inner retinas. They found that the mean GC-IPL of the eyes that underwent surgery for ERM were significantly thinner than the same patients’ fellow eyes, which didn’t undergo surgery, in the same time frame. “To our knowledge, this is the first prospective study with five-year follow-up evaluating functional outcomes after pars plana vitrectomy with membrane peeling for ERM,” the authors explained in their paper.

The overall mean GC-IPL thicknesses were 68.7µm (± 5.4µm) in the eyes that underwent surgery, whereas the fellow eyes were 77.4µm (± 2.4µm).

The investigators speculated that a possible mechanism for the thinning is the creation of the flap during ERM peeling. “All the surgeries were performed by right-handed surgeons, whose tendency was to create a flap in the ERM superotemporally or inferotemporally to avoid the papillomacular bundle and more difficult-to-access nasal macula in flap initiation,” the article explains. The researchers also considered that mechanical trauma from the surgery may explain an initial sharp decrease in GC-IPL thickness, since some recovery was observed over the following 12 months. After three years, however, GC-IPL thickness progressively declined.

Retinal nerve fiber layer defects are used as an early diagnostic method in glaucoma screening, as it often precedes other noticeable changes of the optic nerve head and visual field. Macular GC-IPL is also used for early detection as it correlates strongly with macular sensitivity, the report indicates.

Jonna G, Thompson I, Mendel T, Kim S. Five-year functional outcomes after epiretinal membrane surgery. Retina. September 17, 2018. [Epub ahead of print].