Graefes Arch Clin Exp Ophthalmol DOI 10.1007/s00417-015-3003-5
LETTER TO THE EDITOR (BY INVITATION)
Analysis of the ganglion cell layer and photoreceptor layer using optical coherence tomography after idiopathic epiretinal membrane surgery Sung Who Park 1,2 & Ik Soo Byon 1,3 & Ji Eun Lee 1,2 & Boo Sup Oum 1,2
Received: 11 March 2015 / Accepted: 25 March 2015 # Springer-Verlag Berlin Heidelberg 2015
Dear Editor, We appreciate Dr. Iuliano for his interest and comments regarding our article, and we are pleased to share our opinions regarding visual prognosis after epiretinal membrane (ERM) surgery. Studies from Dr. Iuliano’s group and our group have shown that the ganglion cell layer (GCL) is a significant factor in determining visual acuity in idiopathic ERM [1, 2]. A decrease in the thickness of the GCL was correlated with postoperative visual recovery in their study,[1] whereas thinning of the GCL was correlated with poor visual acuity in our study [2]. We agree with Dr. Iuliano’s comment that our study was not properly controlled, given its retrospective nature; however, we do not believe that this is the main reason for the discrepancy in findings between the two studies. Our primary goal was to reveal the respective impact of the inner and outer retina on postoperative visual acuity [2]. In contrast, their study was focused on the correlation between the GCL and postoperative visual recovery [1]. One feature that differed between the two studies was the severity of ERM. As ERM progresses, multiple retinal layers are compromised, and both studies were based on the hypothesis that the inner retinal layer would be damaged before the outer [1, 2]. Visual acuity at baseline and 6 months in our study was 20/60 and 20/40 as to Snellen’s equivalent, which
* Ji Eun Lee [email protected] 1
Department of Ophthalmology, School of Medicine, Pusan National University, Yangsan, Korea
2
Medical Research Institute, Pusan National University Hospital, Busan, Korea
3
Research Institute for Convergence of Biomedical Science and Technology, Yangsan Pusan National University Hospital, Yangsan, Korea
seemed worse than the 20/50 and 20/25 observed in Pierro’s study [1]. Our inability to obtain a baseline thickness might be related to the greater distortion of the inner retina by ERM. In addition, despite the use of the same name, the two studies assessed different anatomical regions. We chose the ganglion cell complex (GCC), which represents the GCL+ the inner plexiform layer (IPL), as provided by the commercial optical coherence tomography (OCT) machine [1]. They also used the GCC, but it included the GCL+IPL+the nerve fiber layer (NFL), which was provided by a different OCT machine [2]. It has not been determined which parameter is superior to the other. Dr. Iuliano claimed that including the NFL would be the best modality, as it is closer to the ERM. However, this means that the NFL would not be the best choice when the disease is more advanced or damaging the outer retina. Moreover, a variable including multiple parameters cannot represent a specific layer and may introduce the possibility of bias. Lee et al. [3] also measured the GCL+IPL thickness, and achieved results similar to ours—that the postoperative GCC was thinner than normal controls, and a thinner GCC was correlated with poor visual outcomes. Alternatively, Koo et al. [4] prospectively evaluated specific retinal layers, including the inner and outer retina, using a method similar to that of Pierro et al. [1], and showed that the visual acuity improvement was significantly correlated with a reduction in retinal thickness. To understand these conflicting results, the pathological process in ERM should be addressed. The inner retina is thickened by traction of ERM. The thickening of the inner retina represents a pathologic deformation, and its postoperative reduction would be correlated with an improvement of visual acuity, as demonstrated by Pierro et al. [1]. Conversely, the thickness of the inner retina is proportional to the amount of neural tissue. If irreversible loss of the ganglion cells were to place, the postoperative thickness of the GCC should be thinned, as demonstrated in our study [3].
Graefes Arch Clin Exp Ophthalmol
Taken together, the results described herein highlight the importance of the inner retina in ERM and suggest that preventing damage to the outer retina would be insufficient for determining a good visual outcome. Financial disclosure The authors have no proprietary or commercial interest in any of the materials discussed in this article.
References 1.
Pierro L, Iuliano L, Gagliardi M, Codenotti M, Ambrosi A, Bandello F (2015) Role of ganglion cell complex in visual recovery following
surgical internal limiting membrane peeling. Graefes Arch Clin Exp Ophthalmol 253:37–452 2. Park SW, Byon IS, Kim HY, Lee JE, Oum BS (2015) Analysis of the ganglion cell layer and photoreceptor layer using optical coherence tomography after idiopathic epiretinal membrane surgery. Graefes Arch Clin Exp Ophthalmol 253: 207–214 3. Lee E, Yu H (2014) Ganglion cell-inner plexiform layer thickness after epiretinal membrane surgery. Ophthalmology 121: 1579–1587 4. Koo HC, Rhim WI, Lee EK (2012) Morphologic and functional association of retinal layers beneath the epiretinal membrane with spectral-domain optical coherence tomography in eyes without photoreceptor abnormality. Graefes Arch Clin Exp Ophthalmol 250: 491–498
LETTER TO THE EDITOR (BY INVITATION)
Analysis of the ganglion cell layer and photoreceptor layer using optical coherence tomography after idiopathic epiretinal membrane surgery Sung Who Park 1,2 & Ik Soo Byon 1,3 & Ji Eun Lee 1,2 & Boo Sup Oum 1,2
Received: 11 March 2015 / Accepted: 25 March 2015 # Springer-Verlag Berlin Heidelberg 2015
Dear Editor, We appreciate Dr. Iuliano for his interest and comments regarding our article, and we are pleased to share our opinions regarding visual prognosis after epiretinal membrane (ERM) surgery. Studies from Dr. Iuliano’s group and our group have shown that the ganglion cell layer (GCL) is a significant factor in determining visual acuity in idiopathic ERM [1, 2]. A decrease in the thickness of the GCL was correlated with postoperative visual recovery in their study,[1] whereas thinning of the GCL was correlated with poor visual acuity in our study [2]. We agree with Dr. Iuliano’s comment that our study was not properly controlled, given its retrospective nature; however, we do not believe that this is the main reason for the discrepancy in findings between the two studies. Our primary goal was to reveal the respective impact of the inner and outer retina on postoperative visual acuity [2]. In contrast, their study was focused on the correlation between the GCL and postoperative visual recovery [1]. One feature that differed between the two studies was the severity of ERM. As ERM progresses, multiple retinal layers are compromised, and both studies were based on the hypothesis that the inner retinal layer would be damaged before the outer [1, 2]. Visual acuity at baseline and 6 months in our study was 20/60 and 20/40 as to Snellen’s equivalent, which
* Ji Eun Lee [email protected] 1
Department of Ophthalmology, School of Medicine, Pusan National University, Yangsan, Korea
2
Medical Research Institute, Pusan National University Hospital, Busan, Korea
3
Research Institute for Convergence of Biomedical Science and Technology, Yangsan Pusan National University Hospital, Yangsan, Korea
seemed worse than the 20/50 and 20/25 observed in Pierro’s study [1]. Our inability to obtain a baseline thickness might be related to the greater distortion of the inner retina by ERM. In addition, despite the use of the same name, the two studies assessed different anatomical regions. We chose the ganglion cell complex (GCC), which represents the GCL+ the inner plexiform layer (IPL), as provided by the commercial optical coherence tomography (OCT) machine [1]. They also used the GCC, but it included the GCL+IPL+the nerve fiber layer (NFL), which was provided by a different OCT machine [2]. It has not been determined which parameter is superior to the other. Dr. Iuliano claimed that including the NFL would be the best modality, as it is closer to the ERM. However, this means that the NFL would not be the best choice when the disease is more advanced or damaging the outer retina. Moreover, a variable including multiple parameters cannot represent a specific layer and may introduce the possibility of bias. Lee et al. [3] also measured the GCL+IPL thickness, and achieved results similar to ours—that the postoperative GCC was thinner than normal controls, and a thinner GCC was correlated with poor visual outcomes. Alternatively, Koo et al. [4] prospectively evaluated specific retinal layers, including the inner and outer retina, using a method similar to that of Pierro et al. [1], and showed that the visual acuity improvement was significantly correlated with a reduction in retinal thickness. To understand these conflicting results, the pathological process in ERM should be addressed. The inner retina is thickened by traction of ERM. The thickening of the inner retina represents a pathologic deformation, and its postoperative reduction would be correlated with an improvement of visual acuity, as demonstrated by Pierro et al. [1]. Conversely, the thickness of the inner retina is proportional to the amount of neural tissue. If irreversible loss of the ganglion cells were to place, the postoperative thickness of the GCC should be thinned, as demonstrated in our study [3].
Graefes Arch Clin Exp Ophthalmol
Taken together, the results described herein highlight the importance of the inner retina in ERM and suggest that preventing damage to the outer retina would be insufficient for determining a good visual outcome. Financial disclosure The authors have no proprietary or commercial interest in any of the materials discussed in this article.
References 1.
Pierro L, Iuliano L, Gagliardi M, Codenotti M, Ambrosi A, Bandello F (2015) Role of ganglion cell complex in visual recovery following
surgical internal limiting membrane peeling. Graefes Arch Clin Exp Ophthalmol 253:37–452 2. Park SW, Byon IS, Kim HY, Lee JE, Oum BS (2015) Analysis of the ganglion cell layer and photoreceptor layer using optical coherence tomography after idiopathic epiretinal membrane surgery. Graefes Arch Clin Exp Ophthalmol 253: 207–214 3. Lee E, Yu H (2014) Ganglion cell-inner plexiform layer thickness after epiretinal membrane surgery. Ophthalmology 121: 1579–1587 4. Koo HC, Rhim WI, Lee EK (2012) Morphologic and functional association of retinal layers beneath the epiretinal membrane with spectral-domain optical coherence tomography in eyes without photoreceptor abnormality. Graefes Arch Clin Exp Ophthalmol 250: 491–498
