Author Response: Progressive Thinning of Regional Macular Thickness After Epiretinal Membrane Surgery

We appreciate the valuable comments of Azad and Takkar¹ on the mechanisms by which the temporal retina became thinner than baseline value, although the nasal retina remained thick for at least 48 months after epiretinal membrane surgery with inner limiting membrane (ILM) peeling.² 

First of all, the ILM peeling was started routinely at the superior retina, but not the temporal quadrant by a single surgeon. Thus, the fixed surgical protocol does not appear to be responsible for the temporal thinning due to instrumental retinal interaction. Furthermore, ILM peeling was enlarged in a clockwise circumferential manner using an intraocular end-gripping forceps. If inadvertent traction due to ILM peeling causes the increased retinal thinning, the progressive thinning should be different between the right and left eyes. For your reference, we have included the data for postoperative retinal thickness changes from 26 right eyes of 26 patients and 27 left eyes of 27 patients in Figures 1 and 2, respectively. As shown in these Figures, the progressive retinal thinning was identical between the right and left eyes. This holds true also after the macular hole surgery.^3,4 Thus, the fixed surgical protocol does not appear to be responsible for the increased retinal thinning in the temporal macula. 

Curcio et al.⁵ reported that the cell density of retinal ganglion cells (RGCs) and other retinal cells are highly symmetrical except for the temporal quadrant, but the difference between the temporal quadrant and other quadrants was not so large. The authors believe that thicker nasal retinal nerve fiber layer (RNFL) in the nasal quadrant and thinner temporal RNFL are more responsible for the asymmetry in retinal thicknesses rather than the cell density. 

We agree with the possible involvement of foveal displacement toward the optic disc after ILM peeling. However, the displacement does not appear to progress for many years. Thus, the possible involvement of the displacement would be limited to the early postoperative phase. 

Figure 1

 

Temporal changes of the average regional macular thicknesses in the inner temporal and nasal sectors.

Figure 2

 

Temporal changes of the average regional macular thicknesses in the outer temporal and nasal sectors.

We thank you for this opportunity to deepen our discussion for our study.