Analysis of Retinal Ganglion Cell Complex Thickness after Brilliant Blue-Assisted Vitrectomy for Idiopathic Macular Holes

Abstract

Response to the comment on “Analysis of retinal ganglion cell complex thickness after Brilliant Blue-assisted vitrectomy for idiopathic macular holes.”

We would like to thank Sheng and Tong for their comments on our study. We would also like to add that these comments have greatly contributed to our clinical and surgical management.

First, we would like to state that our study is not aimed at examination of functional or histopathological effects of Brilliant Blue G (BBG)-assisted internal limiting membrane (ILM) peeling on retina. In our study, we aimed to examine the effects of the surgery on retinal ganglion cell complex (GCC) layer and retinal nerve fiber layer by means of optical coherence tomography measurements.

Effects of ILM peeling on retina have been intensely and widely discussed in the ophthalmology literature recently. It has been claimed that the ILM is the basal lamina of Muller cells, and its removal could cause damage both to these cells and retinal function, as we mentioned in our study.1 However, points of view claiming that this has a decreasing effect on visual acuity and adverse effects on other retinal layers are controversial. Moreover, there are also contradictory publications. Notwithstanding all those negative effects, in most cases of ILM peeling macular hole surgery, a significant increase in visual acuity was reported after the surgery.

In the studies carried out by Nakamura et al. and Baba et al.2,3 as cited by Sheng and Tong, indocyanine green (ICG) was used for ILM peeling. It is well-known that ICG has a toxic effect on the retina and may even have serious consequences such as optic atrophy. Therefore, these studies cannot be compared to our study. Furthermore, in another study of Baba et al.,4 a BBG group was compared with an ICG group, and significantly better results in terms of retinal sensitivity, visual acuity, photoreceptor inner segment/outer segment junction and external limiting membrane defects were reported in the BBG group compared to the ICG group. However, no significant difference in terms of GCC thickness was reported between these two groups at 3 and 6 months of follow-up. These data demonstrate that the comments of Sheng and Tong about these publications are inaccurate.

In a study of Ohta et al.,5 it was reported that inner retinal layer thickness decreased in the temporal quadrant yet increased in the nasal quadrant in cases subjected to ILM peeling for macular hole surgery. The reason why the results obtained from the temporal and nasal quadrants differed, as stated above, cannot be explained. In our study, inferior and superior quadrants were examined separately, and no significant difference was observed. Software of the device we used is not programmed to differentiate between temporal and nasal quadrants. In addition, manual measurements, as Ohta et al. made, increases the risk of error.

There are many studies in the literature concerning the safety of BBG. Januschowski et al.6 assessed the effect of 0.4 ml BBG on retinal function of a pseudo in vivo model using bovine and human whole mount cultures. The results of the study indicated that, for an exposure time of up to 120 s, BBG has no toxicity upon direct contact with the retina and it can be recommended for clinical use. In addition to this study, Iriyama et al.7 researched the effect of BBG on retinal ganglion cells of rats in vitro and in vivo; however, they observed no significant toxic effect. Ejstrup et al.8 stated that no toxicity was observed histopathologically in vitrectomized pig eyes even after BBG was subretinally injected.

To our knowledge, it does not seem possible to constitute a control group in which there is no ILM peeling, but BBG is applied in a prospective study as Sheng and Tong suggested, since intraocular use of an off-label medicine experimentally unfortunately calls for serious ethical sanctions. In our country, off-label medicine use is allowed only when there is no alternative treatment option. Furthermore, the efficacy of the medicine must be supported by the related literature, and patient consent must be obtained in advance.

Currently, the combination of pars plana vitrectomy with ILM peeling significantly increases the surgical success in macular hole surgery. Furthermore, ILM peeling is recommended for cases of epiretinal membrane (ERM) and vitreomacular traction syndrome with the assumption that it could prevent possible ERM recurrences. Whether ILM peeling causes any microstructural changes or damage or has a visual or functional negative effect on the retina will be examined and demonstrated more clearly over time.

Declaration of interest

The authors report no conflicts of interest.