Citation: Călugăru D, Călugăru M. Comment on "The
thickness and volume of the choroid, outer retinal layers and retinal pigment
epithelium layer changes in patients with diabetic retinopathy" Int
J Ophthalmol 2019;12(8):1366-1368. DOI:10.18240/ijo.2019.08.23
·Comment
and Response·
Comment
on "The thickness and volume of the choroid, outer retinal layers and
retinal pigment epithelium layer changes in patients with diabetic
retinopathy"
Dan Călugăru, Mihai Călugăru
Department of Ophthalmology, University of Medicine Cluj-Napoca 400014,
Romania
Correspondence
to: Mihai
Călugăru. Department of Ophthalmology, University of Medicine, Strada
Brâncoveanu 11, Cluj-Napoca 400467, Romania. mihai.calugaru@mail.dntcj.ro
Received:
DOI:10.18240/ijo.2019.08.23
Citation: Călugăru
D, Călugăru M. Comment on "The thickness and volume of the choroid,
outer retinal layers and retinal pigment epithelium layer changes in patients
with diabetic retinopathy" Int J Ophthalmol 2019;12(8):1366-1368
Dear Editor,
We would
like to address several issues that have arisen from the study by Wang et al[1].
The study was retrospectively conducted and evaluated the thickness and volume
changes of the choroid, outer retinal layers (ORL), and retinal pigment
epithelium (RPE) in patients with diabetic retinopathy (DR) using optical
coherence tomography (OCT) and correlated them with visual acuity.
The authors
defined the ORL thickness as the layers from the RPE to the external limiting
membrane (ELM), that is, the sum of the length of the inner and outer segments
of the photoreceptors. We wonder why the outer nuclear layer (ONL), which is a
part of the photoreceptor cell layer, was not included in this definition.
Moreover, the thickness of the inner retinal layers, whose data are given in
the Table 2, was not clearly defined as the authors did with the definition of
the RPE thickness. Taken together these issues make interpretation of the
results challenging.
There were
significant differences between the non-diabetic macular edema (DME) and DME
groups with respect to the best-corrected visual acuity (BCVA) score (75 and 65
Early Treatment Diabetic Retinopathy Study letters, respectively) and the level
of the Hemoglobin A
There were
no details with regard to the type (1/2) of diabetes, the stages of DR (mild,
moderate, and severe nonproliferative and proliferative DR), and the DME, which
is most commonly classified into being clinically significant or not and
center-involved/non-center-involved. Nothing was stated with respect to the
stratification of the DME eyes by OCT patterns (sponge-like swelling/cystoid
macular edema/subfoveal neuroretinal detachment/mixed type) as well as the
location of the cystoid type (ganglion cell layer,/inner/outer nuclear layers)
if it existed in some cases[2-3] of the DME group.
There were
no data referring to the damages of the photoreceptor cell layers comprising
thinning of the ONL, ELM band defects allowing fluid to enter the retina and
causing “cystoid macular degeneration”, ellipsoid zone disruption,
interdigitation zone loss, and hyperreflective foci in the neuroretina and
subretinal space. These changes could have been better correlated with BCVA
score than did the assessment of the thickness of the choroid, ORL, and RPE.
Likewise, the evaluation of the alterations in the various segments of the
inner retinal layers, that is, the ganglion cell complex, inner nuclear layer,
and outer plexiform layer could have been
better linked with the BCVA score than did the overall assessment of the
thickness of the inner retinal layers. The same thing can be said about the
evaluation of the changes of the retinal pigment epithelial band-Bruch
membrane complex [pigment
migration within the neurosensory retina, retinal pigment epithelium (RPE)
porosity, microrips or blowouts in the RPE, focal RPE atrophy, RPE thickening,
presence of reticular pseudodrusen, and diffuse ooze within or adjacent to the
decompensated RPE] compared with the overall assessment of the RPE thickness[4].
Nothing was
stated concerning the existence or otherwise of a diabetic choroidopathy, which
consists in intrachoroidal vascular abnormalities and which may directly induce
choroidal ischemia, leading to RPE dysfunction. The authors of this study ascertained
that the mean choroidal thickness in both the non-DME and DME groups was
decreased significantly compared with the control group. On the contrary, Kim et
al[5] documented progressive thickening of the choroid layer
caused by increasing the severity of DR (from no DR to proliferative DR) and
development of DME (being thickest in eyes with serous neuroretinal detachment
type of DME), which denotes the progression of diabetic choroidopathy.
Altogether,
the authors of this series concluded that the choroid, ORL, and RPE thicknesses
are significantly decreased in DR patients compared with controls in different
segments. However, nothing was stated regarding the significance of the
significant increase in the thickness of the inner retinal layers in patients
of the DME group as well as the need to assess this change in all segments of
the inner retinal layers.
ACKNOWLEDGEMENTS
All authors
were involved in design and conduct of the study; collection, management,
analysis and interpretation of the data; and preparation, review or approval of
the manuscript.
Conflicts of
Interest: Călugăru
D, None; Călugăru M, None.
REFERENCES
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Author Reply
to the Editor
Dear Editor,
We very much
appreciate Professor Dan Călugăru and Mihai Călugăru’s comments on our study of
the thickness and volume of the choroid, outer retinal layers and retinal
pigment epithelium (RPE) layer changes in patients with diabetic retinopathy
(DR).
In our
study, segmentation of the retinal layers was performed on a horizontal macular
volume scan using new auto-segmentation software (version
Many
previous studies have shown that the stratification of the DME eyes by OCT
patterns (sponge-like swelling/cystoid macular edema/subfoveal neuroretinal
detachment/mixed type) as well as the location of the cystoid type (ganglion
cell layer/inner/outer nuclear layers) can affect the structure and function of
the retina[3-4]. We had not conducted further research in more
detail. In our previous study, we had evaluated variations in choroidal
thickness in different patterns of DME, as demonstrated by fluorescein
angiography and optical coherence tomography (OCT)[4].
Also, ELM
band defects, ellipsoid zone disruption, interdigitation zone loss, and
hyperreflective foci in the neuroretina and subretinal space have been
confirmed correlated with BCVA[5]. Likewise, it had been said that
the evaluation of the changes of the retinal pigment epithelial band-Bruch
membrane complex, the ganglion cell complex, inner nuclear layer, and outer
plexiform layer could have been better linked with the BCVA[6].
However, the topic of study is to study the thickness and volume of the
choroid, outer retinal layers and retinal pigment epithelium layer changes in
patients with diabetic retinopathy. The study of more detail factors can make
our conclusions more convincing, which is also the direction of our further
research.
Kim et al[7]
had documented choroidal thickness increased significantly as the severity
worsened from mild/moderate/no proliferative DR to proliferative DR. However,
in their study mean subfoveal choroidal thickness (SFChT) in groups with no DR
(40 eyes), was 262.3±68.4 μm was thicker than mild/moderate no proliferative DR
244.6±77.0 μm. In our study, we did not incorporate the patients with
proliferative DR into research. Also, as we had mentioned in the limitation,
the small sample size and selection bias of the study would cause discrepancy
in our results. SFChT had been reported they were significantly reduced in
patients with proliferative DR and DME[8]. There are many other
factors (gender, age, eye axis) that affected the choroidal thickness[9-10].
With the development of analysis techniques and software, further studies
should be performed to elucidate choroidal thickness changes in DME. Thanks
again for the evaluation of our research and looking forward to more exchanges
and cooperation.
REFERENCES
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Xiang-Ning
Wang1, Shu-Ting Li1, Qiang Wu1,2
1Department
of Ophthalmology, Shanghai Jiao Tong University Affiliated Sixth People’s
Hospital, Shanghai 200233, China
2Shanghai Key
Laboratory of Diabetes Mellitus, Shanghai 200233, China