Eyes experience thinning of ganglion cell-inner plexiform layer after epiretinal membrane surgery

Andre J. Witkin, MD

This was a prospective interventional cohort study called the Prospective Retinal and Optic Nerve Vitrectomy Evaluation (PROVE) study. Although the title of the manuscript was “Five-year functional outcomes after epiretinal membrane surgery,” the study assessed both functional and anatomic outcomes over a 5-year period, using automated OCT analysis of the ganglion cell-inner plexiform layer (GC-IPL) as well as mean deviation and pattern standard deviation on Humphrey visual fields. The authors designed the study to examine the hypothesized relationship between vitrectomy and secondary open-angle glaucoma.

Forty eyes of 20 patients undergoing unilateral vitrectomy surgery for idiopathic epiretinal membrane were enrolled. Baseline GC-IPL thickness was thinner at baseline and at 3 months postoperatively in surgical eyes compared with fellow eyes; the authors state these automated measurements were unreliable at baseline and month 3, which may explain this discrepancy. Subsequently, there was progressive thinning of the GC-IPL in surgical eyes compared with fellow eyes, which reached statistical significance at 5 years. In terms of functional outcomes, there was a statistically significant difference in mean deviation between surgical eyes and fellow eyes at 12 and 24 months after surgery, although the authors do not state specifically whether this was driven by the phakic group; there was no difference in pattern standard deviation between surgical and fellow eyes.

The authors hypothesized that progressive temporal GC-IPL thinning might have been caused at the site of epiretinal membrane peel initiation, although one would think that there would have been a difference in thinning pattern between right and left eyes if that were the case. Another hypothesis was possible increasing IOP leading to progressive GC-IPL thinning, although this was not supported by progressive visual field changes, and IOP was not reported. The authors suggest that progressive GC-IPL thinning may be associated with an increased risk for glaucoma, although only one patient in this cohort required IOP-lowering eye drops postoperatively.

Overall, this was an ambitious endeavor, and the authors should be commended for the study design. Further studies with larger patient populations will be necessary to more thoroughly evaluate the effects of macular surgery on the inner retinal layers and visual function, and to further elucidate the relationship between vitrectomy and glaucoma.