Retinal layers thickness changes following epiretinal membrane surgery

Abstract

PurposeTo evaluate the time course of changes in the thickness of retinal layers after epiretinal membrane (ERM) removal surgery.MethodsA retrospective cohort study of patients following surgery for idiopathic ERM. We used new specialized image analysis software to create a thickness map of each retinal layer and analyzed changes during one year follow-up. Healthy fellow eyes were used as negative controls and the retina prior to surgery as positive control.ResultsTwenty-one patients were included with a mean age of 68±13 years. Central macular thickness decreased steadily until 6 months after surgery (25% decrease, 516±76 to 386±73 μm, P<0.001) with no further decrease between 6 and 12 months (386±73 to 390±73 μm, P=0.291). The retinal nerve fiber layer (RNFL), and the ganglion cell and inner plexiform layer (GCIPL) were most affected (57%, P<0.001 and 27%, P=0.010, respectively). The thickest region showed a more abrupt decrease of 21% at first follow-up (504±61 to 399±58 μm, P=0.001) with subsequent decrements of about 3%. Prior to surgery all retinal layers were thicker in study eyes compared with healthy control eyes (6-63%, all P<0.05).ConclusionsFollowing ERM surgery, in the course of 6 months, the macula gradually becomes thinner after which a stable state is reached. All layers appear to be affected, with the RNFL and GCIPL impacted the most. Our results provide a unique view on how the thickness of different retinal layers changes following ERM surgery.

Figure 1

A representative retinal thickness analysis of one our patients, a 21-year-old male who suffered from a decrease in visual acuity in his right eye which progressed during the year prior to his admission. His medical and surgical histories were otherwise unremarkable. The left eye (control) is shown in a; the right eye is shown in b, lines represent borders between retinal layers generated automatically, notice the ERM causing traction and loss of the foveal pit. The same eye one year after surgery is shown in c, notice the thinning of the RNFL and GCIPL most prominent in the foveal region. (d) A thickness map of the TRT of the left (control) eye, the TRT of the right eye prior to surgery is shown in (e) and one year after surgery in f, notice the thickness of the temporal-superior region prior to surgery. ERM, epiretinal membrane; RNFL, retinal nerve fiber layer; GCIPL, ganglion cell and inner plexiform layer; TRT, total retinal thickness.

Figure 2

Flow diagram of the inclusion process. ^†SD-OCT inclusion criteria were both a high-quality SD-OCT scan in the month prior to surgery and at least two high-quality SD-OCT scans in the year following surgery. Further details regarding the excluded patients can be found in the online supplement. ERM, epiretinal membrane; PDR, proliferative diabetic retinopathy; NPDR, non-proliferative diabetic retinopathy; SD-OCT, spectral-domain optical coherence tomography.

Figure 3

Overview of retinal layer progression following surgery. Note the decrease in thickness in the study eyes affecting mostly the inner layers. The control eyes show normal retinal architecture and did not change significantly during the follow-up period. RNFL, retinal nerve fiber layer; GCIPL, ganglion cell and inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; PR, photoreceptor layer.

Figure 4

Central macular retinal layers before and after epiretinal membrane peeling. Percent (%) quantities indicate the extent of thickness change relative to the thickness prior to surgery. Note the significant reduction in retinal thickness attained within 6 months followed by a relatively stable progression. The RNFL and GCIPL thickness decreased most dramatically while the OPL and PR were the only layers not to decrease significantly following surgery. *Total retinal thickness change before and 6 months following surgery. **Total retinal thickness change between 6 and 12 months following surgery. ^†Difference between the layer thickness prior to surgery and the end of follow-up. RNFL, retinal nerve fiber layer; GCIPL, ganglion cell and inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; PR, photoreceptor layer; BCVA, best-corrected visual acuity.

Figure 5

Inner and outer annulus progression. Percent (%) quantities indicate the extent of thickness change relative to the thickness prior to surgery. *Total retinal thickness change before and 6 months following surgery. **Total retinal thickness change between 6 and 12 months following surgery. ^†Difference between the layer thickness prior to surgery and the end of follow-up. RNFL, retinal nerve fiber layer; GCIPL, ganglion cell and inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; PR, photoreceptor layer; BCVA, best-corrected visual acuity.

Figure 6

(a) Shows the location of the thickest region prior to surgery according to the ETDRS grid, gray-scale coloring, and percent quantities (%) indicate the frequency of the thickest region occurring in that region. (b) Illustrates the relative thickness of each retinal layer during follow-up of the thickest region only, Percent (%) quantities indicate the extent of thickness change relative to the thickness prior to surgery. ^†Difference between the layer thickness prior to surgery and the end of follow-up. RNFL, retinal nerve fiber layer; GCIPL, ganglion cell, and inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; PR, photoreceptor layer; ETDRS, early treatment of diabetic retinopathy study.