We thank the authors for their careful perusal of our study report and thoughtful observations. We agree that as demonstrated by the large population study1,2 referenced by us and by them, the rate of complications with cataract surgery is non-homogenous and increases dramatically with advanced stage cataracts – as much as 200%+ increase in rate of PCT in cases with high grade cataract, pseudoexfoliation and other comorbidities. In fact, with the co-existence of multiple factors, the compound rate can be even higher.
Our pilot study was in patients with advanced cataracts and multiple co-existing ocular pathologies and given the small sample size we are not surprised that the study point estimate for the PCT rate may be on the higher end of the overall range demonstrated by the larger population study. In addition, the randomized control design of the clinical trial further validates a PCT rate which was similar for both treatment and control groups. Certainly, an informed reader would appreciate that such a small trial is underpowered to be conclusive regarding the small difference between the two groups so no claims should be made about the slightly better rate of PCT and lower trend demonstrated in the miLOOP group.
What is important to appreciate from both the population study and our pilot data is that the rate of PCT is not the same for all cataract surgeries and there is a multiplier effect in certain subgroups and subpopulations. Our authorship team...
We thank the authors for their careful perusal of our study report and thoughtful observations. We agree that as demonstrated by the large population study1,2 referenced by us and by them, the rate of complications with cataract surgery is non-homogenous and increases dramatically with advanced stage cataracts – as much as 200%+ increase in rate of PCT in cases with high grade cataract, pseudoexfoliation and other comorbidities. In fact, with the co-existence of multiple factors, the compound rate can be even higher.
Our pilot study was in patients with advanced cataracts and multiple co-existing ocular pathologies and given the small sample size we are not surprised that the study point estimate for the PCT rate may be on the higher end of the overall range demonstrated by the larger population study. In addition, the randomized control design of the clinical trial further validates a PCT rate which was similar for both treatment and control groups. Certainly, an informed reader would appreciate that such a small trial is underpowered to be conclusive regarding the small difference between the two groups so no claims should be made about the slightly better rate of PCT and lower trend demonstrated in the miLOOP group.
What is important to appreciate from both the population study and our pilot data is that the rate of PCT is not the same for all cataract surgeries and there is a multiplier effect in certain subgroups and subpopulations. Our authorship team felt that for investigational transparency and authenticity it is important to report all results, including the ones we don’t like and the ones that give us pause in order to stimulate thoughtful discourse such as the one unfolding through the comments in your letter.
Sean Ianchulev, MD MPH
Professor of Ophthalmology
New York Eye and Ear Infirmary of Mount Sinai
References
1. Jaycock P, Johnston RL, Taylor H, et al. The Cataract National Dataset electronic multi-centre audit of 55,567 operations: updating benchmark standards of care in the United Kingdom and internationally. Eye 2009 23(1):38-49.
2. Narendran N, Jaycock P, Johnston RL, et al. The Cataract National Dataset electronic multicenter audit of 55,567 operations: risk stratification for posterior capsule rupture and vitreous loss. Eye 2009 23(1):31-7.
We are interested in the work of Ianchulev et al in their recent interventional randomized controlled trial.[1] What piqued our interest was the rate of posterior capsular tears (PCT). 4/53 (7.5%) patients in the miLOOP+phaco group experienced PCT, and 5/48 (10.4%) phaco-alone controls with PCT. These rates are much higher than standard phacoemulsification reports. The authors refer to a large study that identified advanced cataracts increased risk of PCT at comparable levels.[2] That same group published investigations expounding upon this.[3-4] Advanced cataracts were specifically identified as brunescent/white cataracts, contrasting Grade 3-4 in the miLOOP study (curiously described as LOCSIII classification in the manuscript).
Using the risk calculation,[3] the range of composite adjusted odds ratio (aOR) for the miLOOP study was 49.93 (25-28% risk) to an aOR of 0.87 (<1% surgical risk). The average patient from the miLOOP investigation had an aOR of 4.43, thus <5% PCT risk.
Our concerns: First, the authors state that “There was a trend towards a lower rate of capsular tear during the phaco portion with miLOOP-assisted phaco (7.5%) compared to standard phaco (10.4%).” Given the numbers representing these percentages this is an inappropriate description of this relationship.
Let us assume that a control group presented with a PCT rate similar to that reported in literature: <5%. Here, miLOOP-phaco PCT rate would be higher than the control...
We are interested in the work of Ianchulev et al in their recent interventional randomized controlled trial.[1] What piqued our interest was the rate of posterior capsular tears (PCT). 4/53 (7.5%) patients in the miLOOP+phaco group experienced PCT, and 5/48 (10.4%) phaco-alone controls with PCT. These rates are much higher than standard phacoemulsification reports. The authors refer to a large study that identified advanced cataracts increased risk of PCT at comparable levels.[2] That same group published investigations expounding upon this.[3-4] Advanced cataracts were specifically identified as brunescent/white cataracts, contrasting Grade 3-4 in the miLOOP study (curiously described as LOCSIII classification in the manuscript).
Using the risk calculation,[3] the range of composite adjusted odds ratio (aOR) for the miLOOP study was 49.93 (25-28% risk) to an aOR of 0.87 (<1% surgical risk). The average patient from the miLOOP investigation had an aOR of 4.43, thus <5% PCT risk.
Our concerns: First, the authors state that “There was a trend towards a lower rate of capsular tear during the phaco portion with miLOOP-assisted phaco (7.5%) compared to standard phaco (10.4%).” Given the numbers representing these percentages this is an inappropriate description of this relationship.
Let us assume that a control group presented with a PCT rate similar to that reported in literature: <5%. Here, miLOOP-phaco PCT rate would be higher than the control raising safety concerns. Yet the study showed a similarly high complication rate in the control group, statistically maintaining the miLOOP’s safety.
Finally, this occurs in the setting of considerable financial interest.
Regardless of the opportunities not otherwise afforded to these patients by their generous work, ethical standards and protection against bias is essential to protect patients. The complication rate was unacceptably high, and the trial should have been stopped and the study should not have been published.
References
1. Ianchulev T, Chang DF, Koo E, et al. Microinterventional endocapsular nucleus disassembly: novel technique and results of first-in-human randomized controlled study. Br J Ophthalmol 2019 103(2):176-180.
2. Jaycock P, Johnston RL, Taylor H, et al. The Cataract National Dataset electronic multi-centre audit of 55,567 operations: updating benchmark standards of care in the United Kingdom and internationally. Eye 2009 23(1):38-49.
3. Narendran N, Jaycock P, Johnston RL, et al. The Cataract National Dataset electronic multicenter audit of 55,567 operations: risk stratification for posterior capsule rupture and vitreous loss. Eye 2009 23(1):31-7.
4. Johnston RL, Taylor H, Smith R, et al. The Cataract National Dataset Electronic Multi-center audit of 55,567 operations: variation in posterior capsule rupture rates between surgeons. Eye 2010 24(5):888-93.
We thank Drs. Robert and Vidal for their comments. After carefully reading their original series of 5 patients and observing their videos [1], our impression was that both series could definitely refer to the same unique phenomenon.
As stated before [2], a drawback of our series was the inability to acquire eye movement recordings for any of our patients due to technical obstacles and parental refusal. We found Robert and Vidal’s ability to do so in one of their patients very important to the understanding and definition of the phenomenon [1]. Clearly their recordings demonstrate an upbeating nystagmus that would be expected in patients with tonic downgaze, assuming the eyes drift down while saccadic correcting movements are upward towards primary gaze. Hopefully, additional supporting recordings will be added to the literature in the future, allowing us to conclude that this is a representing finding for all of these patients.
This condition was apparently described under different titles over the years owing to scarce descriptions in the literature and difficulty providing convincing support for one definition over the other. This is an important step in that direction. We agree that with their addition of data, the term should include “upbeat nystagmus” and therefore suggest the term “benign infantile positional tonic downgaze with upbeat nystagmus”.
1. Robert MP, Michel S, Adjadj E, Boddaert N, Desguerre I, Vidal PP. Benign intermittent upbeat nystag...
We thank Drs. Robert and Vidal for their comments. After carefully reading their original series of 5 patients and observing their videos [1], our impression was that both series could definitely refer to the same unique phenomenon.
As stated before [2], a drawback of our series was the inability to acquire eye movement recordings for any of our patients due to technical obstacles and parental refusal. We found Robert and Vidal’s ability to do so in one of their patients very important to the understanding and definition of the phenomenon [1]. Clearly their recordings demonstrate an upbeating nystagmus that would be expected in patients with tonic downgaze, assuming the eyes drift down while saccadic correcting movements are upward towards primary gaze. Hopefully, additional supporting recordings will be added to the literature in the future, allowing us to conclude that this is a representing finding for all of these patients.
This condition was apparently described under different titles over the years owing to scarce descriptions in the literature and difficulty providing convincing support for one definition over the other. This is an important step in that direction. We agree that with their addition of data, the term should include “upbeat nystagmus” and therefore suggest the term “benign infantile positional tonic downgaze with upbeat nystagmus”.
1. Robert MP, Michel S, Adjadj E, Boddaert N, Desguerre I, Vidal PP. Benign intermittent upbeat nystagmus in infancy: a new clinical entity. Eur J Paediatr Neurol. 2015; 19: 262-5.
2. Sternfeld A, Lobel D, Leiba H, Luckman J, Michowiz S, Goldenberg-Cohen N. Long-term follow-up of benign positional vertical opsoclonus in infants: retrospective cohort. Br J Ophthalmol. 2018; 102: 757-60.
We thank Dr. Bunce et al for their interest in our paper.1 We would like to apologize for not mentioning the Statistics Notes Series2-12 from the UK Ophthalmology Research Section of the NIHR Statistics group. Given that our paper’s purpose is to evaluate whether the correlated eye data were analyzed properly in published ophthalmic clinical science papers, we did not cite these papers because we think most of them serve as introductions of general statistical methods instead of specific statistical methods for correlated eye data.
We agree these Statistics Notes Series are very helpful to the vision research community to improve the statistical analysis and interpretation of ophthalmic data. We applaud the UK Ophthalmology Research Section of the NIHR Statistics group for their collaborative efforts in improving the quality of statistics for ophthalmic research through these series of publications and workshops. Similarly in the USA, we have been promoting the proper analysis of correlated eye data through tutorial papers13-14 and the ARVO short course. We believe all these efforts will lead to improvement in the statistical practice for ophthalmic data.
We also agree that there are varying degrees of misuse of statistical methods in analyzing correlated eye data. Ignoring the inter-eye correlation when data from both eyes are analyzed is very bad practice as it can lead to the invalid conclusion, while analyzing correlated ocular data at person-level does...
We thank Dr. Bunce et al for their interest in our paper.1 We would like to apologize for not mentioning the Statistics Notes Series2-12 from the UK Ophthalmology Research Section of the NIHR Statistics group. Given that our paper’s purpose is to evaluate whether the correlated eye data were analyzed properly in published ophthalmic clinical science papers, we did not cite these papers because we think most of them serve as introductions of general statistical methods instead of specific statistical methods for correlated eye data.
We agree these Statistics Notes Series are very helpful to the vision research community to improve the statistical analysis and interpretation of ophthalmic data. We applaud the UK Ophthalmology Research Section of the NIHR Statistics group for their collaborative efforts in improving the quality of statistics for ophthalmic research through these series of publications and workshops. Similarly in the USA, we have been promoting the proper analysis of correlated eye data through tutorial papers13-14 and the ARVO short course. We believe all these efforts will lead to improvement in the statistical practice for ophthalmic data.
We also agree that there are varying degrees of misuse of statistical methods in analyzing correlated eye data. Ignoring the inter-eye correlation when data from both eyes are analyzed is very bad practice as it can lead to the invalid conclusion, while analyzing correlated ocular data at person-level does not take full advantage of data and may lead to the inefficient conclusion.
We are saddened by the death of Professor Altman. We have learnt and benefited so much from the papers published by him. Professor Altman’s death is an immense loss to the applied statistics community.
References
1. Zhang HG, Ying GS. Statistical approaches in published ophthalmic clinical science papers: a comparison to statistical practice two decades ago. Br J Ophthalmol. 2018 Sep;102(9):1188-1191.
2. Stephenson J, Bunce C, Doré CJ, Freemantle N; Ophthalmic Statistics Group. Ophthalmic statistics note 11: logistic regression. Br J Ophthalmol. 2016 Dec;100(12):1594-1595.
3. Bunce C, Stephenson J, Doré CJ, Freemantle N; Ophthalmic Statistics Group.Ophthalmic statistics note 10: data transformations.Br J Ophthalmol. 2016 Dec;100(12):1591-1593.
4. Skene SS, Bunce C, Freemantle N, Doré CJ; Ophthalmic Statistics Group. Ophthalmic statistics note 9: parametric versus non-parametric methods for data analysis. Br J Ophthalmol. 2016 Jul;100(7):877-878.
5. Bunce C, Quartilho A, Freemantle N, Doré CJ; Ophthalmic Statistics Group. Ophthalmic statistics note 8: missing data--exploring the unknown. Br J Ophthalmol. 2016 Mar;100(3):291-4.
6. Cipriani V, Quartilho A, Bunce C, Freemantle N, Doré CJ; Ophthalmic Statistics Group. Ophthalmic statistics note 7: multiple hypothesis testing—to adjust or not to adjust. Br J Ophthalmol. 2015 Sep;99(9):1155-7.
7. Cook JA, Bunce C, Doré CJ, Freemantle N; Ophthalmic Statistics Group. Ophthalmic statistics note 6: effect sizes matter. Br J Ophthalmol. 2015 May;99(5):580-1.
8. Saunders LJ, Zhu H, Bunce C, Doré CJ, Freemantle N, Crabb DP; Ophthalmic Statistics Group. Ophthalmic statistics note 5: diagnostic tests—sensitivity and specificity. Br J Ophthalmol. 2015 Sep;99(9):1168-70.
9. Nash R, Bunce C, Freemantle N, Doré CJ, Rogers CA; Ophthalmic Statistics Group.
Ophthalmic Statistics Note 4: analysing data from randomised controlled trials with baseline and follow-up measurements. Br J Ophthalmol. 2014 Nov;98(11):1467-9.
10. Ophthalmic statistics note: the perils of dichotomising continuous variables. Cumberland PM, Czanner G, Bunce C, Doré CJ, Freemantle N, García-Fiñana M; Ophthalmic Statistics Group.Br J Ophthalmol. 2014 Jun;98(6):841-3.
11. Bunce C, Patel KV, Xing W, Freemantle N, Doré CJ; Ophthalmic Statistics Group. Ophthalmic statistics note 2: absence of evidence is not evidence of absence. Br J Ophthalmol. 2014 May;98(5):703-5.
12. Bunce C, Patel KV, Xing W, Freemantle N, Doré CJ; Ophthalmic Statistics Group Ophthalmic statistics note 1: unit of analysis. Br J Ophthalmol. 2014 Mar;98(3):408-12.
13. Ying GS, Maguire MG, Glynn R, Rosner B. Tutorial on Biostatistics: Linear regression analysis of continuous correlated eye data. Ophthalmic Epidemiology 2017;24:130-140.
Ying GS, Maguire MG, Glynn R, Rosner B. Turtorial on biostatistics: Statistical analysis for correlated binary eye data. Ophthalmic Epidemiology 2018;25:1-12.
We congratulate the authors for bringing out an ingenious theory regarding pathogenesis of cupping in glaucomatous (GC) and non-glaucomatous (NGC) eyes using this optical coherence tomography (OCT) model. (1) Differentiating a NGC from GC has been a point of discussion for decades and to finally have an objective parameter “anterior laminar depth (ALD)” which appears specific for glaucomatous cupping from this study is indeed beneficial. The authors have used a linear regression model to compare the GC and NGC eyes with healthy controls with adjustment of age, axial length and peripapillary choroidal thickness (PCT). However, it remains to be further studied, how the ALD is to be used for an individual patient, for eg., what cut-off of ALD above which a patient can be labelled as falling in the glaucomatous range. In this regard, we had a doubt regarding inclusion of PCT in ALD calculation. Since the authors have finally adjusted for PCT in the end, we wonder how the results will turn out if they would remove PCT from ALD measurement and compare the remainder measurement (ALD - PCT) between NGC and GC groups.
Finally, we observed that in this sentence “No significant difference was found in visual field mean deviation (MD) <0.001).”, there is a typographical error and an inadequacy of explanation. No significant difference in visual field MD was indeed seen between NGC and GC groups (p should be >0.99 and not <0.001, as seen in Table...
We congratulate the authors for bringing out an ingenious theory regarding pathogenesis of cupping in glaucomatous (GC) and non-glaucomatous (NGC) eyes using this optical coherence tomography (OCT) model. (1) Differentiating a NGC from GC has been a point of discussion for decades and to finally have an objective parameter “anterior laminar depth (ALD)” which appears specific for glaucomatous cupping from this study is indeed beneficial. The authors have used a linear regression model to compare the GC and NGC eyes with healthy controls with adjustment of age, axial length and peripapillary choroidal thickness (PCT). However, it remains to be further studied, how the ALD is to be used for an individual patient, for eg., what cut-off of ALD above which a patient can be labelled as falling in the glaucomatous range. In this regard, we had a doubt regarding inclusion of PCT in ALD calculation. Since the authors have finally adjusted for PCT in the end, we wonder how the results will turn out if they would remove PCT from ALD measurement and compare the remainder measurement (ALD - PCT) between NGC and GC groups.
Finally, we observed that in this sentence “No significant difference was found in visual field mean deviation (MD) <0.001).”, there is a typographical error and an inadequacy of explanation. No significant difference in visual field MD was indeed seen between NGC and GC groups (p should be >0.99 and not <0.001, as seen in Table 1), however, both MD of NGC and GC were individually significantly different from the control group (p<0.001).
References
1. Fard MA, Moghimi S, Sahraian A, et al Optic nerve head cupping in glaucomatous and non-glaucomatous optic neuropathy British Journal of Ophthalmology Published Online First: 23 May 2018. doi: 10.1136/bjophthalmol-2018-312161
We read with great interest the recent paper by Zhang and Ying exploring statistical approaches in published ophthalmic clinical science papers.1 We very much agree with the main conclusion drawn by the authors that collaborative efforts should be made in the vision research community to improve statistical practise for ocular data. In this vein, however, we were disappointed not to see reference to the Statistics Notes Series that has been published in this very journal. These have been written with a view to tackling some of the more prevalent statistical issues within ophthalmology and we would encourage readers to make use of these.2- 12. Within the UK this view that there needs to be greater collaboration in the vision research community has led to the formation of the Ophthalmology Research Section of the NIHR Statistics group which is championing cross- professional collaboration and active discussion in relation to statistical issues. It is always important when reviewing misuse of statistics in biomedical research to distinguish between misuse that leads to distorted or incorrect results and those methods which do not fully use data to maximum potential given that this loss of information might be viewed as unethical. In this regard we find the results from Zhang et al pleasing in that the proportion of papers which analysed at the level of the individual because of the nature of the observation rose from 15.2 % in 1995 to 50 % in 2017. A finding which is...
We read with great interest the recent paper by Zhang and Ying exploring statistical approaches in published ophthalmic clinical science papers.1 We very much agree with the main conclusion drawn by the authors that collaborative efforts should be made in the vision research community to improve statistical practise for ocular data. In this vein, however, we were disappointed not to see reference to the Statistics Notes Series that has been published in this very journal. These have been written with a view to tackling some of the more prevalent statistical issues within ophthalmology and we would encourage readers to make use of these.2- 12. Within the UK this view that there needs to be greater collaboration in the vision research community has led to the formation of the Ophthalmology Research Section of the NIHR Statistics group which is championing cross- professional collaboration and active discussion in relation to statistical issues. It is always important when reviewing misuse of statistics in biomedical research to distinguish between misuse that leads to distorted or incorrect results and those methods which do not fully use data to maximum potential given that this loss of information might be viewed as unethical. In this regard we find the results from Zhang et al pleasing in that the proportion of papers which analysed at the level of the individual because of the nature of the observation rose from 15.2 % in 1995 to 50 % in 2017. A finding which is statistically significant (P< 0.001, two-tailed Chi-square test). This is pertinent in that historically single person-level responses were often created by ophthalmologists (taking the worse eye only for example or combining information from each eye) prior to the development of the more advanced techniques that make better use of the data (by using data from both eyes instead of one) such as generalised estimating equations. A review by Gange et al has shown that point estimates and tests of significance that used this simple person-level approach are similar to those obtained from the more complex methods and concluded that there would therefore be unlikely benefit from a reanalysis with more sophisticated methods 13 . Misuse of statistics in medical research is unethical and this is a message that has been strongly advocated by Professor Doug Altman since 1980. 14 Professor Altman died in June of 2018 and his loss is hugely felt by the applied statistics community. Let us make 2019 a year of improved statistics throughout all research in vision and eyes.
1 Zhang HG, Ying GS. Statistical approaches in published ophthalmic clinical science papers: a comparison to statistical practice two decades ago. Br J Ophthalmol. 2018 Sep;102(9):1188-1191.
2 Stephenson J, Bunce C, Doré CJ, Freemantle N; Ophthalmic Statistics Group. Ophthalmic statistics note 11: logistic regression. Br J Ophthalmol. 2016 Dec;100(12):1594-1595.
3 Bunce C, Stephenson J, Doré CJ, Freemantle N; Ophthalmic Statistics Group.Ophthalmic statistics note 10: data transformations.Br J Ophthalmol. 2016 Dec;100(12):1591-1593.
4 Skene SS, Bunce C, Freemantle N, Doré CJ; Ophthalmic Statistics Group. Ophthalmic statistics note 9: parametric versus non-parametric methods for data analysis. Br J Ophthalmol. 2016 Jul;100(7):877-878.
5 Bunce C, Quartilho A, Freemantle N, Doré CJ; Ophthalmic Statistics Group. Ophthalmic statistics note 8: missing data--exploring the unknown. Br J Ophthalmol. 2016 Mar;100(3):291-4.
6 Cipriani V, Quartilho A, Bunce C, Freemantle N, Doré CJ; Ophthalmic Statistics Group. Ophthalmic statistics note 7: multiple hypothesis testing—to adjust or not to adjust. Br J Ophthalmol. 2015 Sep;99(9):1155-7.
7 Cook JA, Bunce C, Doré CJ, Freemantle N; Ophthalmic Statistics Group. Ophthalmic statistics note 6: effect sizes matter. Br J Ophthalmol. 2015 May;99(5):580-1.
8 Saunders LJ, Zhu H, Bunce C, Doré CJ, Freemantle N, Crabb DP; Ophthalmic Statistics Group. Ophthalmic statistics note 5: diagnostic tests—sensitivity and specificity. Br J Ophthalmol. 2015 Sep;99(9):1168-70.
9 Nash R, Bunce C, Freemantle N, Doré CJ, Rogers CA; Ophthalmic Statistics Group.
Ophthalmic Statistics Note 4: analysing data from randomised controlled trials with baseline and follow-up measurements. Br J Ophthalmol. 2014 Nov;98(11):1467-9.
10 Ophthalmic statistics note: the perils of dichotomising continuous variables. Cumberland PM, Czanner G, Bunce C, Doré CJ, Freemantle N, García-Fiñana M; Ophthalmic Statistics Group.Br J Ophthalmol. 2014 Jun;98(6):841-3.
11 Bunce C, Patel KV, Xing W, Freemantle N, Doré CJ; Ophthalmic Statistics Group. Ophthalmic statistics note 2: absence of evidence is not evidence of absence. Br J Ophthalmol. 2014 May;98(5):703-5.
12 Bunce C, Patel KV, Xing W, Freemantle N, Doré CJ; Ophthalmic Statistics Group Ophthalmic statistics note 1: unit of analysis. Br J Ophthalmol. 2014 Mar;98(3):408-12.
13 Gange SJ, Linton KL, Scott AJ, DeMets DL, Klein R. A comparison of methods for correlated ordinal measures with ophthalmic applications. Stat Med. 1995 Sep 30;14(18):1961-74
14 Altman DG. Statistics and ethics in medical research. Misuse of statistics is unethical. Br Med J. 1980 Nov 1;281(6249):1182-4.
We read with great interest the nice series from Sternfeld et al. about so-called “benign positional vertical opsoclonus in infants”. [1] As stated by the authors, the very specific condition they describe is not uncommon in the population, yet still poorly described in the scientific literature. Additionally, it is called differently by different authors, one reason for it being the difficulty to assess through the naked eye the very nature of the high frequency eye movements, as shown in video n°1.
The condition combines a positional tonic downgaze and abnormal vertical eye movements. Oculomotor recordings of infants presenting with this clinical picture do actually confirm that these movements comprise downbeating slow phases and upbeating saccades 2, as clinically seen in video n°2, and are therefore a vertical kind of nystagmus. We therefore proposed to refer to them as benign intermittent upbeat nystagmus in infancy. [2] As stated by the authors, the association of a tonic downgaze and an upbeat nystagmus is logical and has been related to posterior semicircular canal predominance. [3]
In addition to the evidence of slow phases in this condition and to the fact that, to the best of our knowledge, no pulse of purely vertical saccades has ever been recorded, the very possibility for the oculomotor system to produce such movements is questionable. Opsoclonus, by definition, designates a succession of multidirectional saccades. We therefo...
We read with great interest the nice series from Sternfeld et al. about so-called “benign positional vertical opsoclonus in infants”. [1] As stated by the authors, the very specific condition they describe is not uncommon in the population, yet still poorly described in the scientific literature. Additionally, it is called differently by different authors, one reason for it being the difficulty to assess through the naked eye the very nature of the high frequency eye movements, as shown in video n°1.
The condition combines a positional tonic downgaze and abnormal vertical eye movements. Oculomotor recordings of infants presenting with this clinical picture do actually confirm that these movements comprise downbeating slow phases and upbeating saccades 2, as clinically seen in video n°2, and are therefore a vertical kind of nystagmus. We therefore proposed to refer to them as benign intermittent upbeat nystagmus in infancy. [2] As stated by the authors, the association of a tonic downgaze and an upbeat nystagmus is logical and has been related to posterior semicircular canal predominance. [3]
In addition to the evidence of slow phases in this condition and to the fact that, to the best of our knowledge, no pulse of purely vertical saccades has ever been recorded, the very possibility for the oculomotor system to produce such movements is questionable. Opsoclonus, by definition, designates a succession of multidirectional saccades. We therefore believe that the term “vertical opsoclonus” should be avoided.
1. Sternfeld A, Lobel D, Leiba H, Luckman J, Michowiz S, Goldenberg-Cohen N. Long-term follow-up of benign positional vertical opsoclonus in infants: retrospective cohort. Br J Ophthalmol. 2018; 102: 757-60.
2. Robert MP, Michel S, Adjadj E, Boddaert N, Desguerre I, Vidal PP. Benign intermittent upbeat nystagmus in infancy: a new clinical entity. Eur J Paediatr Neurol. 2015; 19: 262-5.
3. Brodsky MC, Donahue SP. Primary oblique muscle overaction: the brain throws a wild pitch. Arch Ophthalmol. 2001; 119: 1307-14.
I read with great interest the article by Bae and collegues.1 In their retrospective study, the authors concluded that the presence of atypical epiretinal tissue (AET) in a full-thickness macular hole (FTMH) was related to poorer anatomical success and less visual recovery after surgery.
I agree with the authors on the association of their OCT findings with the visual prognosis. I also agree with them that it is important to identify a good indicator of visual prognosis based on OCT findings. However, there are many confounders to be addressed in this study. For example, preoperative MH size with OCT has been known as a prognostic factor for postoperative visual outcome and anatomical success rate of MH surgery.2,3 A previous study also demonstrated that ERM prevalence increased with severity and size of the FTMH.4 In addition, preoperative visual acuity or preoperative photoreceptor integrity also seems to correlate with visual prognosis.
Thus, their results should be supported by appropriate statistical analysis, that is, multivariate regression analyses. I hope that the authors will comment on the results of multivariate regression analyses to identify the most significant factor to predict visual prognosis after MH surgery.
References
1. Bae K, Lee SM, Kang SW, et al. Atypical epiretinal tissue in full-thickness macular holes: pathogenic and prognostic significance. Br J Ophthalmol. 2018 (in press)
2. Ullrich S, Haritoglou C, Gass...
I read with great interest the article by Bae and collegues.1 In their retrospective study, the authors concluded that the presence of atypical epiretinal tissue (AET) in a full-thickness macular hole (FTMH) was related to poorer anatomical success and less visual recovery after surgery.
I agree with the authors on the association of their OCT findings with the visual prognosis. I also agree with them that it is important to identify a good indicator of visual prognosis based on OCT findings. However, there are many confounders to be addressed in this study. For example, preoperative MH size with OCT has been known as a prognostic factor for postoperative visual outcome and anatomical success rate of MH surgery.2,3 A previous study also demonstrated that ERM prevalence increased with severity and size of the FTMH.4 In addition, preoperative visual acuity or preoperative photoreceptor integrity also seems to correlate with visual prognosis.
Thus, their results should be supported by appropriate statistical analysis, that is, multivariate regression analyses. I hope that the authors will comment on the results of multivariate regression analyses to identify the most significant factor to predict visual prognosis after MH surgery.
References
1. Bae K, Lee SM, Kang SW, et al. Atypical epiretinal tissue in full-thickness macular holes: pathogenic and prognostic significance. Br J Ophthalmol. 2018 (in press)
2. Ullrich S, Haritoglou C, Gass C, et al. Macular hole size as a prognostic factor in macular hole surgery. Br J Ophthalmol 2002;86:390-3.
3. Duker JS, Kaiser PK, Binder S, et al. The International Vitreomacular Traction Study Group classification of vitreomacular adhesion, traction, and macular hole. Ophthalmology 2013;120:2611-9.
4. Cheng L, Freeman WR, Ozerdem U, et al. Prevalence, correlates, and natural history of epiretinal membranes surrounding idiopathic macular holes. Vitrectomy for Macular Hole Study Group. Ophthalmology 2000;107:853-9.
We thank Dr. Sarnicola and family for their interest in our work and at the same time we apologize for not mentioning their preliminary results published in 2010; in this regard, some issues need be clarified.
We used an acronym to shorten the text and facilitate the readers of our article by eliminating this way long descriptive wording of the procedure. This did not imply by any means an attempt at modifying the terminology of surgical techniques, which is usually a task of the ophthalmological community. In fact, a particular acronym becomes a standard only when it is cited as such by numerous papers in the literature. This is not seeming the case, for the acronym “AVB”, that has never been used after its initial introduction by Sarnicola et al., thus failing to achieve the purpose aimed at.
In addition, we had a reason to introduce a new acronym because of a substantial difference in the surgical technique: in fact, instead of creating a new corneal tunnel into the emphysematous tissue, we inject ophthalmic viscoelastic device (OVD) in the same track created for pneumatic dissection, thus increasing surgical reproducibility and safety.
The lack of previous data we indicated (“…little data are available on the success rate…type of cleavage obtained, visual results and complications of this approach”) was simply related to the new concept of performing the injection of the OVD in the same corneal path where the air had failed.
In our series visual...
We thank Dr. Sarnicola and family for their interest in our work and at the same time we apologize for not mentioning their preliminary results published in 2010; in this regard, some issues need be clarified.
We used an acronym to shorten the text and facilitate the readers of our article by eliminating this way long descriptive wording of the procedure. This did not imply by any means an attempt at modifying the terminology of surgical techniques, which is usually a task of the ophthalmological community. In fact, a particular acronym becomes a standard only when it is cited as such by numerous papers in the literature. This is not seeming the case, for the acronym “AVB”, that has never been used after its initial introduction by Sarnicola et al., thus failing to achieve the purpose aimed at.
In addition, we had a reason to introduce a new acronym because of a substantial difference in the surgical technique: in fact, instead of creating a new corneal tunnel into the emphysematous tissue, we inject ophthalmic viscoelastic device (OVD) in the same track created for pneumatic dissection, thus increasing surgical reproducibility and safety.
The lack of previous data we indicated (“…little data are available on the success rate…type of cleavage obtained, visual results and complications of this approach”) was simply related to the new concept of performing the injection of the OVD in the same corneal path where the air had failed.
In our series visual acuity was significantly better after big bubble-DALK than after viscobubble-DALK in the first postoperative months, suggesting a transient negative effect of the OVD; this is an original result never described in any of the papers cited by the Sarnicola et al. in addition, they classified as dDALK all those procedures with a successful pneumatic dissection, whereas we now know that most of big bubbles created with air injection are actually pre-descemetic. This has been demonstrated by several authors after the initial observation by Dua.1 This mistake due to the lack of knowledge of the true anatomy of the floor is combined with the procedural error of putting together all cases with a successful bubble creation, without distinction between those obtained with air injection and those obtained with OVD injection. Our original results show a significant difference in postoperative vision between these two subgroups and represents the main original contribution of the paper. Instead, the methodology used by the Sarnicola group leads to a completely false analysis of the results because it is based to the erroneous assumption that all successful bubbles are descemetic.
References:
1. Dua HS, Faraj LA, Said DG, et al. Human corneal anatomy redefined: a novel pre-
Descemet’s layer (Dua’s layer). Ophthalmology 2013;120:1778–85.
Tuning Of The Literature Related To The Airviscobubble (AVB) DALK Technique
Corresponding author:
Vincenzo Sarnicola
Address: Clinica degli Occhi Sarnicola,
Via Mazzini no. 62, Grosseto 58100, Italy.
Fax: +39-0564-413023
Tel: +39-3201158500
e-mail address: v.sarnicola@hotmail.it or sarnicolavincenzo@gmail.com
Affiliation:
1 Clinica degli Occhi Sarnicola, Grosseto, Italy
2 Ospedale Oftalmico di Torino, Struttura Complessa Oculistica 2, Turin, Italy
3 Ospedale San Giovanni Bosco, Struttura Complessa Oculistica 2, Turin, Italy
4 Department of Biomedical and Specialty Surgical Sciences, University of Ferrara, Ferrara, Italy;
We read with interest the article published by Scorcia et al.[1] It is encouraging to see others, such as Scorcia et al, embracing the use of ophthalmic viscoelastic device (OVD) injection as a second bubble a...
Tuning Of The Literature Related To The Airviscobubble (AVB) DALK Technique
Corresponding author:
Vincenzo Sarnicola
Address: Clinica degli Occhi Sarnicola,
Via Mazzini no. 62, Grosseto 58100, Italy.
Fax: +39-0564-413023
Tel: +39-3201158500
e-mail address: v.sarnicola@hotmail.it or sarnicolavincenzo@gmail.com
Affiliation:
1 Clinica degli Occhi Sarnicola, Grosseto, Italy
2 Ospedale Oftalmico di Torino, Struttura Complessa Oculistica 2, Turin, Italy
3 Ospedale San Giovanni Bosco, Struttura Complessa Oculistica 2, Turin, Italy
4 Department of Biomedical and Specialty Surgical Sciences, University of Ferrara, Ferrara, Italy;
We read with interest the article published by Scorcia et al.[1] It is encouraging to see others, such as Scorcia et al, embracing the use of ophthalmic viscoelastic device (OVD) injection as a second bubble attempt after a failed air big bubble (BB) with air. However, it looks unreasonable to use new acronym (VB-DALK).[1] We would like to highlight that the orginal technique was first described by Sarnicola et al in 2010 and named airviscobubble (indicated with the acronym “AVB”).[2] Scorcia et al probably did not notice this paper in literature, citing only a later study by Muftuoglu et al from 2013.[1-3] Consistency of terms that are well-established in literature should be maintained. Attempting to rename both the name (viscobubble DALK instead of airviscobubble) and the acronym (VB-DALK instead of AVB) of a recognized technique without specific reasons does not serve any purpose as it is confusing for to readers and problematic for the comparison of future studies.
The Authors also stated in the introduction of their paper that “…little data are available on the success rate, type of cleavage obtained, visual results and complications of this approach”.[1] A more complete review of the literature would demonstrate the inaccuracy of this statement.[4-9] Several studies have reported the efficacy of AVB as a rescue bubble technique, showing a 15% increase of descemetic DALK in 507 eyes, the advantages of using a cannula for the OVD injection, the usefulness of the technique even in cases of herpetic corneal scar, and the importance of performing a paracentesis before the AVB formation.[4-9]
Despite the manuscript is very well written and pleasant to read, we would like to draw attention to another small inaccuracy. The consideration statement reported in the 6th paragraph of the discussion section (“The loss of pressure … trephination size.”) is missing the appropriate reference.[1,3]
REFERENCES:
1. Scorcia V, DE Luca V, Lucisano A, et al. Br J Ophthalmol 2018;102:1288–1292. doi:10.1136/bjophthalmol-2017-311419
2. Sarnicola V, Toro P, Gentile D, et al: Descemetic DALK and predescemetic DALK: outcomes in 236 cases of keratoconus. Cornea 2010;29:53-9.
3. Muftuoglu O, Toro P, Hogan RN, et al. Sarnicola air-visco bubble technique in deep anterior lamellar keratoplasty. Cornea 2013;32:527-32.
4. Sarnicola V, Toro P. Blunt cannula for descemetic deep anterior lamellar keratoplasty. Cornea 2010;30:859-8.
5. Sarnicola V, Toro P. Deep anterior lamellar keratoplasty. In herpes simplex corneal opacities. Cornea 2011;29:60-4.
6. Sarnicola V, Toro P, Sarnicola C, et al. Long-term graft survival in deep anterior lamellar keratoplasty. Cornea. 2012;31:621-6.
7. Sarnicola E, Sarnicola C, Sarnicola V. Deep anterior lamellar keratoplasty: surgical technique, indications, clinical results and complications. In: Guell JL, ed. Cornea ESASO Course Series. Basel, Switzerland: Karger; 2015:81-101.
8. Sarnicola V, Sarnicola E, Sarnicola C. Recovery techniques in DALK, Chapter 120 In: Mannis M, Holland E Cornea 4th edition 2016. Editor: Elsevier - Health Sciences Division.
9. Sarnicola E, Sarnicola C, Sabatino F, et al. Cannula DALK versus Needle DALK for Keratoconus. Cornea 2016;35:1508-11.
We thank the authors for their careful perusal of our study report and thoughtful observations. We agree that as demonstrated by the large population study1,2 referenced by us and by them, the rate of complications with cataract surgery is non-homogenous and increases dramatically with advanced stage cataracts – as much as 200%+ increase in rate of PCT in cases with high grade cataract, pseudoexfoliation and other comorbidities. In fact, with the co-existence of multiple factors, the compound rate can be even higher.
Our pilot study was in patients with advanced cataracts and multiple co-existing ocular pathologies and given the small sample size we are not surprised that the study point estimate for the PCT rate may be on the higher end of the overall range demonstrated by the larger population study. In addition, the randomized control design of the clinical trial further validates a PCT rate which was similar for both treatment and control groups. Certainly, an informed reader would appreciate that such a small trial is underpowered to be conclusive regarding the small difference between the two groups so no claims should be made about the slightly better rate of PCT and lower trend demonstrated in the miLOOP group.
What is important to appreciate from both the population study and our pilot data is that the rate of PCT is not the same for all cataract surgeries and there is a multiplier effect in certain subgroups and subpopulations. Our authorship team...
Show MoreWe are interested in the work of Ianchulev et al in their recent interventional randomized controlled trial.[1] What piqued our interest was the rate of posterior capsular tears (PCT). 4/53 (7.5%) patients in the miLOOP+phaco group experienced PCT, and 5/48 (10.4%) phaco-alone controls with PCT. These rates are much higher than standard phacoemulsification reports. The authors refer to a large study that identified advanced cataracts increased risk of PCT at comparable levels.[2] That same group published investigations expounding upon this.[3-4] Advanced cataracts were specifically identified as brunescent/white cataracts, contrasting Grade 3-4 in the miLOOP study (curiously described as LOCSIII classification in the manuscript).
Using the risk calculation,[3] the range of composite adjusted odds ratio (aOR) for the miLOOP study was 49.93 (25-28% risk) to an aOR of 0.87 (<1% surgical risk). The average patient from the miLOOP investigation had an aOR of 4.43, thus <5% PCT risk.
Our concerns: First, the authors state that “There was a trend towards a lower rate of capsular tear during the phaco portion with miLOOP-assisted phaco (7.5%) compared to standard phaco (10.4%).” Given the numbers representing these percentages this is an inappropriate description of this relationship.
Let us assume that a control group presented with a PCT rate similar to that reported in literature: <5%. Here, miLOOP-phaco PCT rate would be higher than the control...
Show MoreWe thank Drs. Robert and Vidal for their comments. After carefully reading their original series of 5 patients and observing their videos [1], our impression was that both series could definitely refer to the same unique phenomenon.
As stated before [2], a drawback of our series was the inability to acquire eye movement recordings for any of our patients due to technical obstacles and parental refusal. We found Robert and Vidal’s ability to do so in one of their patients very important to the understanding and definition of the phenomenon [1]. Clearly their recordings demonstrate an upbeating nystagmus that would be expected in patients with tonic downgaze, assuming the eyes drift down while saccadic correcting movements are upward towards primary gaze. Hopefully, additional supporting recordings will be added to the literature in the future, allowing us to conclude that this is a representing finding for all of these patients.
This condition was apparently described under different titles over the years owing to scarce descriptions in the literature and difficulty providing convincing support for one definition over the other. This is an important step in that direction. We agree that with their addition of data, the term should include “upbeat nystagmus” and therefore suggest the term “benign infantile positional tonic downgaze with upbeat nystagmus”.
1. Robert MP, Michel S, Adjadj E, Boddaert N, Desguerre I, Vidal PP. Benign intermittent upbeat nystag...
Show MoreWe thank Dr. Bunce et al for their interest in our paper.1 We would like to apologize for not mentioning the Statistics Notes Series2-12 from the UK Ophthalmology Research Section of the NIHR Statistics group. Given that our paper’s purpose is to evaluate whether the correlated eye data were analyzed properly in published ophthalmic clinical science papers, we did not cite these papers because we think most of them serve as introductions of general statistical methods instead of specific statistical methods for correlated eye data.
We agree these Statistics Notes Series are very helpful to the vision research community to improve the statistical analysis and interpretation of ophthalmic data. We applaud the UK Ophthalmology Research Section of the NIHR Statistics group for their collaborative efforts in improving the quality of statistics for ophthalmic research through these series of publications and workshops. Similarly in the USA, we have been promoting the proper analysis of correlated eye data through tutorial papers13-14 and the ARVO short course. We believe all these efforts will lead to improvement in the statistical practice for ophthalmic data.
We also agree that there are varying degrees of misuse of statistical methods in analyzing correlated eye data. Ignoring the inter-eye correlation when data from both eyes are analyzed is very bad practice as it can lead to the invalid conclusion, while analyzing correlated ocular data at person-level does...
Show MoreDear authors,
We congratulate the authors for bringing out an ingenious theory regarding pathogenesis of cupping in glaucomatous (GC) and non-glaucomatous (NGC) eyes using this optical coherence tomography (OCT) model. (1) Differentiating a NGC from GC has been a point of discussion for decades and to finally have an objective parameter “anterior laminar depth (ALD)” which appears specific for glaucomatous cupping from this study is indeed beneficial. The authors have used a linear regression model to compare the GC and NGC eyes with healthy controls with adjustment of age, axial length and peripapillary choroidal thickness (PCT). However, it remains to be further studied, how the ALD is to be used for an individual patient, for eg., what cut-off of ALD above which a patient can be labelled as falling in the glaucomatous range. In this regard, we had a doubt regarding inclusion of PCT in ALD calculation. Since the authors have finally adjusted for PCT in the end, we wonder how the results will turn out if they would remove PCT from ALD measurement and compare the remainder measurement (ALD - PCT) between NGC and GC groups.
Show MoreFinally, we observed that in this sentence “No significant difference was found in visual field mean deviation (MD) <0.001).”, there is a typographical error and an inadequacy of explanation. No significant difference in visual field MD was indeed seen between NGC and GC groups (p should be >0.99 and not <0.001, as seen in Table...
We read with great interest the recent paper by Zhang and Ying exploring statistical approaches in published ophthalmic clinical science papers.1 We very much agree with the main conclusion drawn by the authors that collaborative efforts should be made in the vision research community to improve statistical practise for ocular data. In this vein, however, we were disappointed not to see reference to the Statistics Notes Series that has been published in this very journal. These have been written with a view to tackling some of the more prevalent statistical issues within ophthalmology and we would encourage readers to make use of these.2- 12. Within the UK this view that there needs to be greater collaboration in the vision research community has led to the formation of the Ophthalmology Research Section of the NIHR Statistics group which is championing cross- professional collaboration and active discussion in relation to statistical issues. It is always important when reviewing misuse of statistics in biomedical research to distinguish between misuse that leads to distorted or incorrect results and those methods which do not fully use data to maximum potential given that this loss of information might be viewed as unethical. In this regard we find the results from Zhang et al pleasing in that the proportion of papers which analysed at the level of the individual because of the nature of the observation rose from 15.2 % in 1995 to 50 % in 2017. A finding which is...
Show MoreDear Editor,
We read with great interest the nice series from Sternfeld et al. about so-called “benign positional vertical opsoclonus in infants”. [1] As stated by the authors, the very specific condition they describe is not uncommon in the population, yet still poorly described in the scientific literature. Additionally, it is called differently by different authors, one reason for it being the difficulty to assess through the naked eye the very nature of the high frequency eye movements, as shown in video n°1.
Show MoreThe condition combines a positional tonic downgaze and abnormal vertical eye movements. Oculomotor recordings of infants presenting with this clinical picture do actually confirm that these movements comprise downbeating slow phases and upbeating saccades 2, as clinically seen in video n°2, and are therefore a vertical kind of nystagmus. We therefore proposed to refer to them as benign intermittent upbeat nystagmus in infancy. [2] As stated by the authors, the association of a tonic downgaze and an upbeat nystagmus is logical and has been related to posterior semicircular canal predominance. [3]
In addition to the evidence of slow phases in this condition and to the fact that, to the best of our knowledge, no pulse of purely vertical saccades has ever been recorded, the very possibility for the oculomotor system to produce such movements is questionable. Opsoclonus, by definition, designates a succession of multidirectional saccades. We therefo...
I read with great interest the article by Bae and collegues.1 In their retrospective study, the authors concluded that the presence of atypical epiretinal tissue (AET) in a full-thickness macular hole (FTMH) was related to poorer anatomical success and less visual recovery after surgery.
I agree with the authors on the association of their OCT findings with the visual prognosis. I also agree with them that it is important to identify a good indicator of visual prognosis based on OCT findings. However, there are many confounders to be addressed in this study. For example, preoperative MH size with OCT has been known as a prognostic factor for postoperative visual outcome and anatomical success rate of MH surgery.2,3 A previous study also demonstrated that ERM prevalence increased with severity and size of the FTMH.4 In addition, preoperative visual acuity or preoperative photoreceptor integrity also seems to correlate with visual prognosis.
Thus, their results should be supported by appropriate statistical analysis, that is, multivariate regression analyses. I hope that the authors will comment on the results of multivariate regression analyses to identify the most significant factor to predict visual prognosis after MH surgery.
References
Show More1. Bae K, Lee SM, Kang SW, et al. Atypical epiretinal tissue in full-thickness macular holes: pathogenic and prognostic significance. Br J Ophthalmol. 2018 (in press)
2. Ullrich S, Haritoglou C, Gass...
We thank Dr. Sarnicola and family for their interest in our work and at the same time we apologize for not mentioning their preliminary results published in 2010; in this regard, some issues need be clarified.
Show MoreWe used an acronym to shorten the text and facilitate the readers of our article by eliminating this way long descriptive wording of the procedure. This did not imply by any means an attempt at modifying the terminology of surgical techniques, which is usually a task of the ophthalmological community. In fact, a particular acronym becomes a standard only when it is cited as such by numerous papers in the literature. This is not seeming the case, for the acronym “AVB”, that has never been used after its initial introduction by Sarnicola et al., thus failing to achieve the purpose aimed at.
In addition, we had a reason to introduce a new acronym because of a substantial difference in the surgical technique: in fact, instead of creating a new corneal tunnel into the emphysematous tissue, we inject ophthalmic viscoelastic device (OVD) in the same track created for pneumatic dissection, thus increasing surgical reproducibility and safety.
The lack of previous data we indicated (“…little data are available on the success rate…type of cleavage obtained, visual results and complications of this approach”) was simply related to the new concept of performing the injection of the OVD in the same corneal path where the air had failed.
In our series visual...
Tuning Of The Literature Related To The Airviscobubble (AVB) DALK Technique
Corresponding author:
Vincenzo Sarnicola
Address: Clinica degli Occhi Sarnicola,
Via Mazzini no. 62, Grosseto 58100, Italy.
Fax: +39-0564-413023
Tel: +39-3201158500
e-mail address: v.sarnicola@hotmail.it or sarnicolavincenzo@gmail.com
Authors:
Vincenzo Sarnicola, MD1
v.sarnicola@hotmail.it
Enrica Sarnicola, MD1-3
e.sarnicola@hotmail.it
Caterina Sarnicola, MD 4
c.sarnicola@hotmail.it
Affiliation:
1 Clinica degli Occhi Sarnicola, Grosseto, Italy
2 Ospedale Oftalmico di Torino, Struttura Complessa Oculistica 2, Turin, Italy
3 Ospedale San Giovanni Bosco, Struttura Complessa Oculistica 2, Turin, Italy
4 Department of Biomedical and Specialty Surgical Sciences, University of Ferrara, Ferrara, Italy;
Competing interests: None.
Keywords: DALK; airviscobubble; AVB; dDALK; descemetic DALK.
Word Count: 303
To the Editor:
We read with interest the article published by Scorcia et al.[1] It is encouraging to see others, such as Scorcia et al, embracing the use of ophthalmic viscoelastic device (OVD) injection as a second bubble a...
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