We read with interest the paper by Wimpissinger et al comparing
sutureless 23-gauge system to a standard 20-gauge system for pars plana
vitrectomy, in a randomized clinical trial.[1] We aim to highlight a few
issues in the design, methodology and analysis.
The authors have analysed postoperative pain and conjunctival
injection as primary outcome measures. The effort by the assessor to
elicit a...
We read with interest the paper by Wimpissinger et al comparing
sutureless 23-gauge system to a standard 20-gauge system for pars plana
vitrectomy, in a randomized clinical trial.[1] We aim to highlight a few
issues in the design, methodology and analysis.
The authors have analysed postoperative pain and conjunctival
injection as primary outcome measures. The effort by the assessor to
elicit a response on the degree of pain is likely to be biased if he is
not masked, as in this study. In assessment, the authors have used
descriptive terms like no pain, mild, moderate and severe pain. The
authors could have used other standardized methods described to measure
pain such as numerical scores, faces scale, visual analogue scales and
multidimensional instruments like various questionnaires. Literature in
Ophthalmology has precedence of using a visual analogue scale for
assessment of pain.[2]
The authors determined the sample size by statistical pre-study
evaluation (by two group t-test with a 0.05 two-sided significance
level).
Since the authors have not provided data on effect size (delta), and
power (1-beta), it is not clear how a sample size of 60 with 30 patients
in each arm was arrived at.
The other confounding variable likely to be of significance are the
issues like randomization of 4 surgeons (instead of preferably single
surgeon), use of different machines for 20Ga and 23Ga surgeries,
unspecified cut rates for 20Ga system (likely to influence time of
vitrectomy), the lens status (likely to influence the extent of
vitrectomy possible and aimed at), type of tamponade (likely to
influence postoperative intraocular pressures) and suturing technique of
conjunctiva (likely to influence subjective pain) after 20Ga surgery.
In analysis, nominal type of categorical data (as used for
assessing postoperative pain and conjunctival injection) would have been
better analysed in terms of median and interquartile range rather than
taking their minimum, maximum and average values.
The authors have concluded that "The 23 gauge system seems to be a
safe system suitable for a broad spectrum of vitreoretinal diseases". We
disagree with this conclusion as the data provided shows that 3 (10%,
95% CI -0.74 to 20.74%) patients developed serious complications, 2 of
whom required re-surgery.[1]
An international group developed the Consolidated Standards for
Reporting Trials (CONSORT) statement in an attempt to improve documented
suboptimal reporting of RCTs.[3] In an attempt to further improve the
reporting of RCTs, the same international group published the revised
CONSORT statement in 2001 which outlined a checklist of 22 items.[4]
References
1. B Wimpissinger, L Kellner, W Brannath, K Krepler, U Stolba, C
Mihalics and S Binder. 23-gauge versus 20-gauge system for pars plana
vitrectomy: a prospective randomised clinical trial. Br J Ophthalmol
2008; 92; 1483-1487.
2. Mathew MR, Williams A, Esakowitz L, Webb LA, Murray SB, Bennett
HG. Patient comfort during clear corneal phacoemulsification with sub-
Tenon's local anesthesia. J Cataract Refract Surg 2003 ; 29(6): 1132-6.
3. Begg C, Cho M, Eastwood S, et al. Improving the quality of
reporting of randomized controlled trials. The CONSORT statement. JAMA
1996;276:637-9.
4. Moher D, Schulz KF, Altman DG. The CONSORT statement: revised
recommendations for improving the quality of reports of parallel-group
randomised trials. Lancet 2001;357:1191-4.
I read with interest the recent study by Yi et al.
A very minor point... were the Stratus OCT images obtained using the
"Radial
Lines" protocol or the "Fast Macular Thickness" protocol? From Figure 1, I suspect that the higher resolution Radial Lines protocol was used (and not Fast Macular Thickness as described in the manuscript).
In any event, I commend the authors for a worthwhile addition to the
li...
I read with interest the recent study by Yi et al.
A very minor point... were the Stratus OCT images obtained using the
"Radial
Lines" protocol or the "Fast Macular Thickness" protocol? From Figure 1, I suspect that the higher resolution Radial Lines protocol was used (and not Fast Macular Thickness as described in the manuscript).
In any event, I commend the authors for a worthwhile addition to the
literature.
I read with interest the article by Dr. Cohn, et al regarding the
natural history of
autosomal dominant optic atrophy (DOA). The authors describe an average
of
10-year follow up for 69 patients with genetically confirmed DOA. In
their
study, 6 (9%) patients enjoyed improvement in visual acuity by 2 or more
lines.
I found this surprising, and I wonder if the authors could provide...
I read with interest the article by Dr. Cohn, et al regarding the
natural history of
autosomal dominant optic atrophy (DOA). The authors describe an average
of
10-year follow up for 69 patients with genetically confirmed DOA. In
their
study, 6 (9%) patients enjoyed improvement in visual acuity by 2 or more
lines.
I found this surprising, and I wonder if the authors could provide
further
information regarding this group. Is it the opinion of the authors that
these
patients actually improved or that this may represent testing artifact or
bias?
Were they significantly younger than the rest of the cohort? Was their
follow up
significantly shorter? By how much did the acuities improve among this
group?
Was their baseline acuity more likely to come from outside records?
We are very interested to read Prof Radcliffe’s data showing a variable
IOP rise in different subjects tested with the same goggle design. Their
results, like ours,[1] suggest that individual anatomic or physiologic
factors are important in determining the IOP rise. Currently, these
factors are unknown with significant certainty, however som...
We are very interested to read Prof Radcliffe’s data showing a variable
IOP rise in different subjects tested with the same goggle design. Their
results, like ours,[1] suggest that individual anatomic or physiologic
factors are important in determining the IOP rise. Currently, these
factors are unknown with significant certainty, however some of our
results identified that subjects with reduced orbital area were more prone
to IOP elevation. These results were not confirmed by subsequent
measurement and analysis of a separate cohort.[1] However, it is our
impression that subjects with a flatter orbital profile, without a
prominent orbital brow and with more soft tissue in the anterior orbit are
at greater risk of IOP rise.
We also provide a service to our patients whereby we can test their
IOP response to wearing goggles. We use either a standard set with holes
drilled or their own and drill holes through to enable applanation
tonometry whilst they wear them in the clinic. We agree fully with Prof
Radcliffe that this is a useful service for glaucoma patients and
suspects.
Yours Sincerely
W H Morgan
For W H Morgan, T S Cunneen, C Balaratnasingam and D-Y Yu
Reference
1. Morgan WH, Cunneen TS, Balaratnasingam C, Yu DY. Wearing swimming
goggles can elevate intraocular pressure. British Journal of Ophthalmology
2008;92:1218-21.
We would like to congratulate Drs Morgan and colleagues on their
recent paper “Wearing swimming goggles can elevate intraocular pressure.”
We performed a similar study and presented our data at the Association for
Research in Vision and Ophthalmology in 2007. Our findings demonstrated
that in healthy participants, IOP measurements taken during goggle wear
were significantly higher at both one and five minutes, with an av...
We would like to congratulate Drs Morgan and colleagues on their
recent paper “Wearing swimming goggles can elevate intraocular pressure.”
We performed a similar study and presented our data at the Association for
Research in Vision and Ophthalmology in 2007. Our findings demonstrated
that in healthy participants, IOP measurements taken during goggle wear
were significantly higher at both one and five minutes, with an average
increase of 12.5% or +1.5 mmHg. A small subset of eyes (10%) in our study
had an increase in IOP greater than 5 mmHg at both one and five minutes of
goggle wear. We applaud the use of a predictive model in evaluating which
goggles may be associated with IOP elevation. In our study, utilizing a
single goggle design (Speedo), the IOP did not increase significantly in
40% of subjects but increased over 5mmHg in others. In light of this
variability we have retained our prototype study goggle in order to
measure the goggle-induced IOP effect in our glaucoma patients who wish to
swim. Regularly testing these patients in the office allows us to better
inform our patients of the potential risks of goggle wear during swimming.
We thank Dr. Alm for his interest and comment on our paper entitled
“Practical recommendations for measuring rates of visual field change in
glaucoma.” We agree that the standard error of slope estimates is
dependent
on the number of examinations and duration of follow-up. However, these
two parameters are not interchangeable. As pointed out correctly by Dr.
Alm,
the same number of examinations ov...
We thank Dr. Alm for his interest and comment on our paper entitled
“Practical recommendations for measuring rates of visual field change in
glaucoma.” We agree that the standard error of slope estimates is
dependent
on the number of examinations and duration of follow-up. However, these
two parameters are not interchangeable. As pointed out correctly by Dr.
Alm,
the same number of examinations over a longer time period will lead to a
better slope estimation and therefore greater power simply because the
amount of net change is larger. Hence the difference in follow-up of 3 (27 compared to 24 months) months in his example yields an additional change
of -0.5 dB in Mean Deviation and therefore the number of examinations
derived to obtain equivalent power is not surprising.
The goal of our first recommendation of 6 examinations in the first
two years
was not to determine whether the slope of visual field decay is
statistically
significant or not. It was to identify patients who we feel are
progressing
rapidly. In these patients we do not feel that prolonging the follow-up
is an
adequate substitute for more frequent examinations. Even if equivalent
statistical power is obtained with this approach, prolonging the follow-up comes with the very significant cost of more visual field loss.
Our paper was meant to be an initial guideline for clinicians on what rates of visual field change could be detected (with varying degrees of power) with a
given frequency of examinations. We would like to emphasise that there is a large distinction between detection of progression and determining the
rate of visual field change. Therefore the proposed guidelines are not necessarily
designed to detect progression. We welcome the comments of Dr. Alm and others that encourage us to factor in aspects such as the time-separation
between tests and measures besides Mean Deviation which consider the
location of visual field defects.
Sincerely,
BC Chauhan, DF Garway-Heath, FJ Goñi, L Rossetti, B Bengtsson, AC
Viswanathan and A Heijl
There are many pertinent and interesting observations in your
article. As one of the first few users of PASCAL in India, we have now a
large data-base of patients in a short span of time. Critical to
understanding PASCAL is the fluence. Contrary to what we always thought,
retinal hemorrhages and acoustic damage are not seen at 10 ms pulses if
the fluence is within limits. I wish that PASCAL was also programmed to
fix the flue...
There are many pertinent and interesting observations in your
article. As one of the first few users of PASCAL in India, we have now a
large data-base of patients in a short span of time. Critical to
understanding PASCAL is the fluence. Contrary to what we always thought,
retinal hemorrhages and acoustic damage are not seen at 10 ms pulses if
the fluence is within limits. I wish that PASCAL was also programmed to
fix the fluence level at the beginning of each procedure (titrated for each eye) so that inadvertently fluence does not shoot up when the spot size
is changed. PASCAL has really taken out the sting from PRP.
In the article entitled 'Electrophysiological effects of intravitreal
Avastin (bevacizumab) in the treatment of exudative age-related macular
degeneration (ARMD)' by Karanjia et al (Br J Ophthalmol 2008), the authors
examine the sensitivity of multifocal-electroretinogram (mfERG) at
measuring changes in retinal electrical activity in response to Avastin
treatment for ARMD.
In this interesting paper t...
In the article entitled 'Electrophysiological effects of intravitreal
Avastin (bevacizumab) in the treatment of exudative age-related macular
degeneration (ARMD)' by Karanjia et al (Br J Ophthalmol 2008), the authors
examine the sensitivity of multifocal-electroretinogram (mfERG) at
measuring changes in retinal electrical activity in response to Avastin
treatment for ARMD.
In this interesting paper the authors study the changes of P1 response
amplitude and support that this is the first study to demonstrate a
statistically significant change in retinal electrical activity post-bevacizumab in patients with ARMD.
I would like to draw attention to the authors of this article that in our
prospective study 'Intravitreal use of bevacizumab (Avastin) for
choroidal neovascularization due to ARMD: a preliminary mfERG and OCT
study' by Moschos MM et al (Doc Ophthalmol 2007; 114:37-44) really for
the first time we evaluated the macular function before and after
intravitreal use of Avastin.
In our paper based on the study of 18 eyes, 1 month after treatment the
retinal response density of mfERG really shows an improvement but 3 months
after treatment no difference was found between baseline and 3 months.
Our results show that there are anatomical correlates to support the
concept of disease amelioration 1 month after treatment. This is mainly
the decrease of macular thickness as measured by OCT in an extremely
significant degree (p<0.001) the first month after treatment. On the
contrary the mean visual acuity improved only by 0.03 the first month
after treatment and by 0.02 three months after treatment. On the contrary
the mfERG improvement did not follow the decrease of macular thickness and
is significant only the first month after treatment. These findings show
that the increase of visual acuity, as also the improvement of electrical
responses of the macular area is disproportional to the decrease of
macular thickness. This may be explained by the fact that macular edema
is only a parameter that may affect visual acuity and electrophysiological
responses in the beginning of the disease. Atrophy of the retina,
particularly of the photoreceptors, atrophy of the pigment epithelium and
scarring are all unmeasured variables, which influence vision [1, 2].
References
1. Moschos M, Brouzas D, Apostolopoulos M, et al. Intravitreal use of
bevacizumab (Avastin) for choroidal neovascularization due to ARMD: a
preliminary multifocal-ERG and OCT study. Doc Ophtalmol 2007;114:137-144.
2. Moschos M, Panayotidis D, Theodossiadis G, et al. Assessment of macular
function by electroretinography in age-related macular degeneration before
and after photodynamic therapy. J Fr Ophtalmologie 2004;27:1001-1006.
Marilita M Moschos, MD, PhD
Department of Ophthalmology, University of Athens, Athens, Greece
Correspondence and reprints:
Moschos M. Marilita MD, PhD
144, Kountouriotou Str
185 35 Piraeus
Greece
Tel : ++30 6944887319
Fax: ++30 210 4122139
E-mail: moschosmarilita@yahoo.fr
This is an interesting haematological syndrome. I would question calling
the occurrence simultaneous when the vision loss was symptomatically
sequential. Roughly 20% of normals have areas of absent choroidal
filling in the early venous phase of the retinal circulation. These
areas fill suddenly as the dye arrives in a normal manner; if there is
true pathological delay such as occurs with giant cell arteritis the...
This is an interesting haematological syndrome. I would question calling
the occurrence simultaneous when the vision loss was symptomatically
sequential. Roughly 20% of normals have areas of absent choroidal
filling in the early venous phase of the retinal circulation. These
areas fill suddenly as the dye arrives in a normal manner; if there is
true pathological delay such as occurs with giant cell arteritis the
areas tend to fill slowly and from the edges. It can not be called
pathological relative choroidal perfusion delay till the retinal
circulation has reached the mid venous phase as defined by the vein
being half filled with fluorescence. The most common cause for a delay
from injection to the early venous phase is a mild vasovagal reaction or
a reduced cardiac output in a patient with atrial fibrillation. The time
from injection thus cannot be used to define choroidal perfusion delay.
We read with interest the recent study by Krebs et al. demonstrating the limitations of StratusOCT mapping software in the context of age-related macular degeneration (AMD).[1] We wish to applaud the authors for their study - while the limitations of StratusOCT automated analysis have previously been reported,[2] the fact remains that many ophthalmologists may not be well acquainted with these errors. We agree wi...
We read with interest the recent study by Krebs et al. demonstrating the limitations of StratusOCT mapping software in the context of age-related macular degeneration (AMD).[1] We wish to applaud the authors for their study - while the limitations of StratusOCT automated analysis have previously been reported,[2] the fact remains that many ophthalmologists may not be well acquainted with these errors. We agree with the authors and wish to underline the importance of these errors in this era of optical coherence tomography (OCT)-guided retreatment regimens for anti-angiogenic agents and increasing adoption of quantitative OCT measurements as secondary outcome parameters in clinical trials.[3]
In their study, the authors present evidence that automated Stratus software provides correct results in only 57.1% of eyes with AMD.[1] These results are consistent with previous reports and in line with clinical experience.[2] As mentioned in the discussion, manual placement of boundaries on OCT scans may represent a solution to this problem. We wish to thank the authors for mentioning our custom OCT grading software termed “OCTOR” as one possible software tool to perform this kind of analysis. The authors comment that "this software is not commercially available or supported by the StratusOCT". However, OCTOR was designed specifically with StratusOCT in mind and readily handles raw exported StratusOCT images. OCTOR is publicly available and can be downloaded from www.diesel.la. This software facilitates manual segmentation of OCT images and allows quantitative analysis of any area of interest in these images e.g. retina, subretinal fluid, subretinal tissue, or pigment epithelium detachment.[4] Furthermore, the most recent version of the Stratus OCT software (version 5.0) enables users to manually correct errant boundaries.
In their discussion, the authors comment that "manually set boundary lines would add subjectivity to the retinal thickness measurements". Recent research demonstrating both the accuracy and reproducibility of manual grading with OCTOR software in the setting of neovascular AMD suggests that manual grading does not necessarily add subjectivity to retinal thickness measurements.[5] Instead, manually corrected boundaries allow for more reliable data than the frequently erroneous automated boundary detection of the StratusOCT software. We recently used the manual grading software OCTOR to quantify the volumes of the neurosensory retina, subretinal fluid, subretinal tissue, and pigment epithelial detachments. Intergrader comparisons showed a high level of agreement and a strong correlation between measurements for all spaces (weighted Kappa= 0.72-0.97; ICC = 0.92-0.99). Although these values were obtained by graders who had undergone a formal certification program in our reading center, in our experience OCT grading can be learned both more quickly, and more easily, than grading of fluorescein angiography. This hypothesis is supported by the level of agreement between measurements in our study which was appreciably better than that which has been reported elsewhere for fluorescein angiography.[6]
Although significant progress is being made, the complex morphology of neovascular AMD presents a challenge to the development of automated OCT interpretation software. As automated segmentation algorithms improve, it will be necessary to assess their efficacy in a quantitative manner against a 'gold standard'. We believe that the accuracy of manual segmentation by trained human graders is such that it could serve as a 'gold standard' against which to compare the results of automated analysis.
In conclusion, we wish to commend the authors for highlighting this area, which is likely to be of critical importance as the next generation of OCT technology is incorporated into the diagnosis and management of neovascular AMD.
LICENCE FOR PUBLICATION:
The Corresponding Author has the right to grant on behalf of all authors, and does grant on behalf of all authors, an exclusive licence on a worldwide basis to the BMJ Publishing Group Ltd to permit this article (if accepted) to be published in BJO and any other BMJPGL products and sublicences such use and exploit all subsidiary rights, as set out in our licence (http://bjo.bmj.com/ifora/licence.pdf).
COMPETING INTERESTS:
Drs. Walsh and Sadda are co-inventors of Doheny intellectual property related to spectral domain optical coherence tomography that has been licensed by Topcon Medical Systems.
FUNDING:
Supported in part by NIH Grant EY03040 and NEI Grant R01 EY014375
References
1. Krebs I, Haas P, Zeiler F, Binder S. Optical coherence tomography: limits of the retinal-mapping program in age-related macular degeneration. Br J Ophthalmol 2008;92:933-5.
2. Sadda SR, Wu Z, Walsh AC, et al. Errors in retinal thickness measurements obtained by optical coherence tomography. Ophthalmology 2006;113:285-93.
3. Fung AE, Lalwani GA, Rosenfeld PJ, et al. An optical coherence tomography-guided, variable dosing regimen with intravitreal ranibizumab (Lucentis) for neovascular age-related macular degeneration. Am J Ophthalmol 2007;143:566-83.
4. Sadda SR, Joeres S, Wu Z, et al. Error correction and quantitative subanalysis of optical coherence tomography data using computer-assisted grading. Invest Ophthalmol Vis Sci 2007;48:839-48.
5. Joeres S, Tsong JW, Updike PG, et al. Reproducibility of quantitative optical coherence tomography subanalysis in neovascular age-related macular degeneration. Invest Ophthalmol Vis Sci 2007;48:4300-7.
6. Holz FG, Jorzik J, Schutt F, et al. Agreement among ophthalmologists in evaluating fluorescein angiograms in patients with neovascular age-related macular degeneration for photodynamic therapy eligibility (FLAP-study). Ophthalmology 2003;110:400-5.
Dear editor,
We read with interest the paper by Wimpissinger et al comparing sutureless 23-gauge system to a standard 20-gauge system for pars plana vitrectomy, in a randomized clinical trial.[1] We aim to highlight a few issues in the design, methodology and analysis.
The authors have analysed postoperative pain and conjunctival injection as primary outcome measures. The effort by the assessor to elicit a...
I read with interest the recent study by Yi et al.
A very minor point... were the Stratus OCT images obtained using the "Radial Lines" protocol or the "Fast Macular Thickness" protocol? From Figure 1, I suspect that the higher resolution Radial Lines protocol was used (and not Fast Macular Thickness as described in the manuscript).
In any event, I commend the authors for a worthwhile addition to the li...
Dear Editor:
I read with interest the article by Dr. Cohn, et al regarding the natural history of autosomal dominant optic atrophy (DOA). The authors describe an average of 10-year follow up for 69 patients with genetically confirmed DOA. In their study, 6 (9%) patients enjoyed improvement in visual acuity by 2 or more lines.
I found this surprising, and I wonder if the authors could provide...
Author’s Response re letter by Nathan M Radcliffe
Dear Editor,
We are very interested to read Prof Radcliffe’s data showing a variable IOP rise in different subjects tested with the same goggle design. Their results, like ours,[1] suggest that individual anatomic or physiologic factors are important in determining the IOP rise. Currently, these factors are unknown with significant certainty, however som...
We would like to congratulate Drs Morgan and colleagues on their recent paper “Wearing swimming goggles can elevate intraocular pressure.” We performed a similar study and presented our data at the Association for Research in Vision and Ophthalmology in 2007. Our findings demonstrated that in healthy participants, IOP measurements taken during goggle wear were significantly higher at both one and five minutes, with an av...
Dear Editor
We thank Dr. Alm for his interest and comment on our paper entitled “Practical recommendations for measuring rates of visual field change in glaucoma.” We agree that the standard error of slope estimates is dependent on the number of examinations and duration of follow-up. However, these two parameters are not interchangeable. As pointed out correctly by Dr. Alm, the same number of examinations ov...
There are many pertinent and interesting observations in your article. As one of the first few users of PASCAL in India, we have now a large data-base of patients in a short span of time. Critical to understanding PASCAL is the fluence. Contrary to what we always thought, retinal hemorrhages and acoustic damage are not seen at 10 ms pulses if the fluence is within limits. I wish that PASCAL was also programmed to fix the flue...
Dear Editor,
In the article entitled 'Electrophysiological effects of intravitreal Avastin (bevacizumab) in the treatment of exudative age-related macular degeneration (ARMD)' by Karanjia et al (Br J Ophthalmol 2008), the authors examine the sensitivity of multifocal-electroretinogram (mfERG) at measuring changes in retinal electrical activity in response to Avastin treatment for ARMD. In this interesting paper t...
This is an interesting haematological syndrome. I would question calling the occurrence simultaneous when the vision loss was symptomatically sequential. Roughly 20% of normals have areas of absent choroidal filling in the early venous phase of the retinal circulation. These areas fill suddenly as the dye arrives in a normal manner; if there is true pathological delay such as occurs with giant cell arteritis the...
We read with interest the recent study by Krebs et al. demonstrating the limitations of StratusOCT mapping software in the context of age-related macular degeneration (AMD).[1] We wish to applaud the authors for their study - while the limitations of StratusOCT automated analysis have previously been reported,[2] the fact remains that many ophthalmologists may not be well acquainted with these errors. We agree wi...
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