Dear Editor

We read with interest the article by Steven et al.[1] on their finding of secondary paracentral retinal holes following internal limiting membrane peel. We have also reported on 4 eyes of 4 patients that developed iatrogenic eccentric macular holes following vitrectomy with ILM peeling for idiopathic macular holes.[2] In their report, Steven et al treated 3 of the 7 patients with argon laser photocoagulation. Haritoglou et al.[3] reported paracentral scotomata following vitrectomy with ILM peeling for macular holes. Treatment of these paracentral holes with argon laser photocoagulation could therefore make these scotomas worse. The pathogenesis of these iatrogenic holes is unclear. We believe that there must be an element of mechanical trauma involved in the formation of these secondary holes, despite the fact that it is not visible at the time of surgery. Their speculation of weakening of the glial structure of the retina caused by decapitation of the Muller cells is interesting and may also play an important role – as all the holes reported are in the ILM- denuded area. We note that in the series by Steven et al, all the reported holes appear temporal to the fovea. In our series, the holes were reported inferior as well as nasal to the fovea. We used trypan blue to assist in the peeling of the ILM, and no obvious areas of retinal trauma were apparent at the time of surgery. The secondary holes became apparent in the follow-up period; none of them have had any treatment and have not caused any problems after long-term follow-up (6 years). We recommend that these holes should not be treated, as they do not appear to lead to retinal detachment.

References

1. Steven P, Laqua H, Wong D, Hoerauf H. Secondary paracentral retinal holes following internal limiting membrane removal. Br J Ophthalmol 2006;90:293-95.

2. Rubinstein A, Bates R, Benjamin L, Shaikh A. Iatrogenic eccentric full thickness macular holes following vitrectomy with ILM peeling for idiopathic macular holes. Eye 2005;19:1333-35.

3. Haritoglou C, Ehrt O, Gass CA, et al. Paracentral scotomata: a new finding after vitrectomy for idiopathic macular hole. Br J Ophthalmol 2001;85:231-3.

Dear Editor,

In a recent issue of the Journal Steven et al. describe secondary retinal holes after removal of the inner limiting membrane (ILM) [1]. We consider this a key retinal publication and therefore wish to strengthen the importance of the authors' findings for modern surgery of the vitreoretinal interface.

Interestingly, the paper included only patients with macular puckers and cystoid macular oedema, but not macular holes. In cases of macular holes only a small-sized central part of the ILM will usually be peeled. In contrast, macular puckers and cystoid oedemas will typically affect a larger region of the posterior pole. Thus a more extensive fraction of the ILM will be stripped if surgery is performed in such cases.

More than thirty years ago Foos [2] described two anatomical features of the ILM that might explain why current peeling of the peripheral ILM may be unsafe. Firstly, the ILM is thickest at the posterior pole and will become continuously thinner in the periphery. In the initiation of the ILM removal this may increase the risk for direct retinal trauma. Secondly, the Müller glia are more strongly attached to the ILM away from the macula. This may lead to indirect surgical trauma of the non-neuronal parts of the retina during the peeling process.

In conclusion, the more eccentric from the macula, the thinner and the more adherent to the retina is the ILM. As described by Steven et al., removal of these peripheral ILM fractions may lead to retinal hole formation. [1] Direct and/or indirect surgical trauma may be responsible for such injury, which may not be related to toxic effect of dyes used. One should therefore avoid stripping the peripheral ILM outside macular region to prevent inadvertent retinal damage.

References

1. Steven P, Laqua H, Wong D, Hoerauf H. Secondary paracentral retinal holes following internal limiting membrane removal. Br J Ophthalmol. 2006;90:293-95.

2. Foos RY. Vitreoretinal juncture; topographical variations. Invest Ophthalmol. 1972;11:801-8.