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Displaying 1-9 letters out of 461 published

  1. Details of participants in the study are incomplete.

    I have read the article with great interest as it is one of the early reports of this emerging technology. Going through the article I noticed that though the inclusion criteria describe that the patients with refractive error less than 10 diopter of myopia and astigmatism less than 5 diopter were included, the results show only the average myopia and standard deviation. The range of spherical myopia is not given, though the range of astigmatism is provided.

    i will be keen to know the range of myopia included as it is obvious that a very thin lenticule will be difficult to create and retrieve in case of low myopia.

    Kindly comment on the following points, 1. the range of myopic refractive error included in the study. 2. Any limitation in including patients with low myopia. 3. Was there any difficulty in handling a thin lenticule in the patients with low refractive error?

    Conflict of Interest:

    None declared

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  2. Dua's Layer and Success of Non Penetrating Glaucoma Filtering surgery

    Dear Editor,

    We read with interest the article on extension of Dua's layer into trabecular meshwork.(1)This knowledge has implications also in success of newer surgeries like deep sclerectomy. Deep Sclerectomy is a safer option to trabeculectomy but is known to fail in some cases (2)(3). Guedes et al(4) have investigated the factors affecting the success of this surgery. George Kistos et al (5) have discussed a modified deep sclerectomy to deal with failure and they postulated an external removal of the inner wall of Schlemm's canal and the external layers of the trabecular meshwork with external trabeculectomy . Iordanidou et al (6) have shown how the bio mechanics of the cornea changes after deep sclerectomy and this may be responsible for success in stabilising field defects independent of the intra ocular pressure . Dua's layer has been shown by Dua et al to affect the corneal biomechanics.It now seems that the removal of the Dua's layer may be central to success of deep sclerectomy due to various reasons, one being imperviousness of this layer ( which gets confused with Descemet's layer) and the other being the fact that the biomechanics of the cornea changes with removal of this layer. We have been doing modified deep sclerectomy since 5 years at our hospitals and go a little ahead anteriorly into the cornea and create a Descemet's window without perforating that window and sometimes we do not see egress of fluid at the removal of deep scleral flap and deroofing of the schlemm's canal and the Descemet's window. We routinely do a video audit of our cases. In our video audit we have noted that in cases where there is no fluid egress the "descemet's membrane" withstands pressure and the air bubble in the anterior chamber is visible and even on increasing the anterior chamber pressure with a large bubble the "descemets membrane" does not rupture. Dua et al (7)have discussed the properties of this layer and it is said to be impervious to air and known to withstand pressures upto 200kPa.We postulate that this is a combination of descemet's layer and Dua's layer which has not been removed. These are the cases in which the deep sclerectomy fails and needs a gonio puncture. In other cases the "descemet's membrane" is very thin and shows egress of fluid spontaneously and sometimes ruptures if the anterior chamber pressure is high due to large air bubble, releasing a small air bubble but no prolapse of iris or sometimes leading to iris prolapse without the membrane being touched. In these cases there is good egress of fluid even from the area of schlemm's canal.These cases of deep sclerectomy are successful. These are the cases where the Dua's layer has been removed and hence the layer remaining in the eye is purely Descemet's layer and allows egress of fluid and cannot withstand pressure. We postulate that the thick membrane that withstands pressure and does not allow egress of fluid easily is a sclerosed peripheral part of Dua's layer which if not removed causes failure of deep sclerectomy necessitating a gonio puncture later. Removing this layer is probably the key to success of Deep Sclerectomy. Further evaluation is needed to substantiate this hypothesis though our video audit shows that, cases in which the layer has not been removed ,fail and need a gonio puncture and the cases in which the Dua's layer is removed are successful and do not need a gonio puncture suggesting that removal of Dua's Layer is essential for success of Deep Sclerectomy, modified or otherwise.

    References:-

    1)Harminder S Dua, Lana A Faraj,Matthew J Branch,Aaron M Yeung,Mohamed S Elalfy,Dalia G Said,Trevor Gray,and James Lowe.The collagen matrix of the human trabecular meshwork is an extension of the novel pre-Descemet's layer (Dua's layer)Br J Ophthalmol 2014 98:691-697;

    2)El Sayyad F(1), Helal M, El-Kholify H, Khalil M, El-Maghraby A.Nonpenetrating deep sclerectomy versus trabeculectomy in bilateral primary open-angle glaucoma.Ophthalmology. 2000 Sep;107(9):1671-4.

    3)Zsolt Varga and Tarek Shaarawy.Deep Sclerectomy: Safety and Efficacy.Middle East Afr J Ophthalmol. 2009 Jul-Sep; 16(3): 123-126.

    4)Guedes RA(1), Guedes VM, Chaoubah A. Factors associated with non-penetrating deep sclerectomy failure in controlling intraocular pressure.Acta Ophthalmol. 2011 Feb;89(1):58-61.

    5)George Kitsos,Miltiades Aspiotis, Yannis Alamanos, Konstantinos Psilas. A modified deep sclerectomy with or without external trabeculectomy: a comparative studyClinical Ophthalmology 2010:4 557-564

    6)Iordanidou V(1), Hamard P, Gendron G, Labb? A, Raphael M, Baudouin C.Modifications in corneal biomechanics and intraocular pressure after deep sclerectomy.J Glaucoma. 2010 Apr-May;19(4):252-6.

    7)Dua HS, Faraj LA, Said DG, Gray T, Lowe J (September 2013). "Human corneal anatomy redefined: a novel pre-Descemet's layer (Dua's layer)". Ophthalmology 120 (9): 1778-85

    Conflict of Interest:

    None declared

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  3. Reply to Response: Optical coherence tomography of the suprachoroid after CyPass Micro-Stent implantation for the treatment of open angle glaucoma

    We thank Huisingh and McGwin (1) for their interest and comments regarding our manuscript describing the optical coherence tomography (OCT) findings after CyPass Micro-Stent implantation for the treatment of open angle glaucoma (2). The importance of formal statistical analysis was considered at the time of submission. Given the small sample size of the study, and the descriptive nature of the study, we found that statistical analysis of this data beyond what is presented in manuscript was not appropriate. We hope future studies with a larger scale and a prospective nature will incorporate more advanced statistical analysis. Based on the findings of our study, we believe that OCT of the supraciliary space can be a powerful predictor of outcomes in patients undergoing CyPass Micro-Stent implantation. Hady Saheb1, Tsontcho Ianchulev2, Iqbal 'Ike' K. Ahmed3 1McGill University, Montreal, QC, Canada; 2University of California San Francisco, San Francisco, CA, USA; 3University of Toronto, Toronto, ON, Canada

    Corresponding author Iqbal 'Ike' K. Ahmed Credit Valley EyeCare 3200 Erin Mills Parkway, Unit 1 Mississauga, Ontario L5L 1W8, Canada Contributors: HS, TI and IKA contributed to the conception of the letter and final approval of the version to be published. REFERENCE 1. Huisingh, C. & McGwin, G. Response: Optical coherence tomography of the suprachoroid after CyPass Micro-Stent implantation for the treatment of open angle glaucoma. Br J Ophthalmol (2014). doi:10.1136/bjophthalmol- 2013-304806 2. SAHEB, H., Ianchulev, T. & Ahmed, I. I. K. Optical coherence tomography of the suprachoroid after CyPass Micro-Stent implantation for the treatment of open-angle glaucoma. Br J Ophthalmol 98, 19-23 (2014).

    Conflict of Interest:

    IIK Ahmed (Transcend Medical: research grant, consultant), H Saheb (Transcend Medical: travel grant), T Ianchulev (Transcend Medical: employee)

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  4. CHARACTERIZATION OF UVEITIS IN ASSOCIATION WITH MULTIPLE SCLEROSIS

    Dear Editor, We congratulate Messenger et al. for their study entitled 'Characterization of uveitis in association with multiple sclerosis'.[1] The authors investigated clinical and demographic characteristics of multiple sclerosis (MS) patients with uveitis. The study has significant results including the ratios of anterior, intermediate and posterior uveitis in this group of MS patients.

    We found out that 54% of MS patients without any visual symptoms and signs had significantly delayed P100 latency in pattern visual evoked potential s (PVEP).[2] This high ratio may mean that clinical symptoms and signs resemble an iceberg in MS world. This finding should force the researchers to use ocular electrophysiologic findings especially in researches including ocular involvement. Therefore, I want to ask to the authors whether they have PVEP results of the patients, but not only the patients included in the study. In case they have, would they mind to investigate the relation between P100 latency and the presence/absence of uveitis in the patients. The authors have a significant number of MS patients. They have the data whether each patient has uveitis. If they have PVEP results too, this gives them an invaluable chance. This is important, because if patients with higher P100 latency have a higher risk of uveitis, then these patients may be suggested to have ophthalmic examinations more frequently than patients with normal P100 latency. That kind of investigation would also add significant contribution to the MS literature.

    REFERENCES 1. Messenger W, Hildebrandt L, Mackensen F, Suhler E, Becker M, Rosenbaum JT. Characterisation of uveitis in association with multiple sclerosis. Br J Ophthalmol 2014 doi: 10.1136/bjophthalmol-2014-305518[published Online First: Epub Date]|. 2. Gundogan FC, Demirkaya S, Sobaci G. Is optical coherence tomography really a new biomarker candidate in multiple sclerosis? - A structural and functional evaluation. Investigative Ophthalmology & Visual Science 2007;48(12):5773-81 doi: Doi 10.1167/Iovs.07-0834[published Online First: Epub Date]|.

    Conflict of Interest:

    None declared

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  5. Three-year follow-up of posterior chamber toric phakic intraocular lens implantation for the correction of high myopic astigmatism in eyes with keratoconus.

    Dear Editor,

    We read with great interest the article by Kamiya et al about use of toric implantable collamer lenses (ICL) in patients with keratoconus. [1] The results are very encouraging. However, we found some discrepancies in the study.

    The mean manifest spherical equivalent was -9.70 D, up to -13.75 D. The Amsler-Krumeich classification system stage 2 includes patients up to -8.0 D of myopia, astigmatism or both.[2] There seems to be a mismatch between the included subjects and inclusion criteria.

    A control arm of patients using only contact lenses could have been taken. Higher order aberrations and contrast sensitivity should have been studied. For assessment of time course of events, the data should have been tested if it is parametric. otherwise Friedman's one-way analysis of variance (ANOVA) test should have been used. Pre operative best corrected visual acuity (BCVA) and post operative uncorrected visual acuity (UCVA) may be compared by Wilcoxon-signed-rank test for evaluation of the intervention on visual acuity.

    Irregular astigmatism at the corneal plane will not be corrected by the toric ICL and can lead to poor post operative vision and should be informed to the patient. This can be evaluated by looking at the rigid contact lens BCVA, and if it is significantly higher than the spectacle corrected BCVA, then after toric ICL implantation, vision will be poor.

    The authors also need to evaluate the centration of cone.[3] A decentred cone will lead to a mismatch between the visual axis, pupillary axis and axis through the cone and distortion of vision. In such cases, reshaping the cone by prior intrastromal ring segments would be useful. The use of the new V4b model of toric ICL with the central hole can also cause aberrations and poor visual quality and its effects need to be studied in eyes with keratoconus.[4]

    References

    1 Kamiya K, Shimizu K, Kobashi H, et al. Three-year follow-up of posterior chamber toric phakic intraocular lens implantation for the correction of high myopic astigmatism in eyes with keratoconus. Br J Ophthalmol Published Online First: 21 August 2014. doi:10.1136/bjophthalmol-2014-305612 2 Choi JA, Kim M-S. Progression of keratoconus by longitudinal assessment with corneal topography. Invest Ophthalmol Vis Sci 2012;53:927-35. doi:10.1167/iovs.11-8118 3 Kummelil MK, Hemamalini MS, Bhagali R, et al. Toric implantable collamer lens for keratoconus. Indian J Ophthalmol 2013;61:456-60. doi:10.4103/0301-4738.116064 4 Huseynova T, Ozaki S, Ishizuka T, et al. Comparative study of 2 types of implantable collamer lenses, 1 with and 1 without a central artificial hole. Am J Ophthalmol 2014;157:1136-43. doi:10.1016/j.ajo.2014.01.032

    Conflict of Interest:

    None declared

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  6. Re:Reproducibility of aberrometry-based intraoperative refraction during cataract surgery, Statistical issues

    Dear Sirs, We are grateful to Sabour and Ghassemi for their interest in our recent article[1]. In our understanding, they query why we did not use intra class correlation (ICC) as a measure for precision. Our test-retest reliability (absolute agreement ICC) is derived from the maximum likelihood (LM) estimates of the one-way random effects model of the form: yij=Mu+ri+Epsilonij, where yij is the measurement of the ith eye by the jth measurement (say spherical equivalent measured on the first (second or third) occasion), Mu is the mean rating (say mean spherical equivalent), ri is the eye random effect and Epsilonij is a random error. As described in Rabe-Hesketh and Skrondal[2], the reliability is calculated as p ?=? ?/(? ?+? ?), where Psi is a between-subject variance and Theta is a within-subject variance. Here we assume that n eyes are randomly selected from the population of potential eyes. Each one is measured by a different set of k measurements, randomly drawn from the population of potential measurements. The consistency of agreement is not defined in this case, as each eye is evaluated by a different set of measurements. Thus, there is no between- measurements variability in this model. We agree that clinical judgement is paramount, which is why, indeed, we state in our paper (p 5) that "the clinical interpretation of the agreement range (...) is vital (underlining added)". It is before the background of such clinical interpretations in the paper and of the above explanations that we derived our conclusions in, as we trust, an appropriate way. Yours respectfully,

    References

    1. Huelle JO, Katz T, Druchkiv V, et al. First clinicial results on the feasibility, quality and reproducibility of aberrometry-based intraoperative refraction during cataract surgery. Br J Ophthalmol 2014. 2. Rabe-Hesketh S, Skrondal A. Multilevel and Longitudinal Modeling Using Stata, Second Edition: Stata Press, 2008. 3. McAlinden C, Khadka J, Pesudovs K. Statistical methods for conducting agreement (comparison of clinical tests) and precision (repeatability or reproducibility) studies in optometry and ophthalmology. Ophthalmic Physiol Opt 2011;31(4):330-8.

    Conflict of Interest:

    None declared

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  7. An additional explanation for azithromycin's efficacy in treating meibomian gland dysfunction

    We would like to congratulate Dr. Kashkouli et al for their recently published paper "Oral azithromycin versus doxycycline in meibomian gland dysfunction: a randomized double masked open label clinical trial". The authors found that azithromycin induced a significantly better overall clinical response than doxycycline, and attributed this effect to the antibacterial and anti-inflammatory effects of azithromycin. However, we would like to suggest an additional explanation for their results. We have discovered that azithromycin can directly increase lipid accumulation and promote terminal differentiation of human meibomian gland epithelial cells in vitro.1 This effect may be due to azithromycin's cationic amphiphilic structure and an associated phospholipidosis.2 We have also discovered that the stimulatory action of azithromycin on human meibomian gland epithelial cells is unique, and cannot be duplicated by exposure to doxycycline, minocycline or tetracycline.2 3 In effect, this lipid- promoting activity of azithromycin may improve the quality of meibomian gland secretions, alleviate the evaporative dry eye, and attenuate such additional signs as conjunctival redness and ocular surface staining. Overall, this ability of azithromycin to promote human meibomian gland epithelial cell function may account for its greater efficacy, as compared to doxycycline, in alleviating the signs and symptoms of human meibomian gland dysfunction.

    References

    1. Liu Y, Kam WR, Ding J, et al. Effect of azithromycin on lipid accumulation in immortalized human meibomian gland epithelial cells. JAMA ophthalmol 2014;132(2):226-8. 2. Liu Y, Kam WR, Ding J, et al. One man's poison is another man's meat: using azithromycin-induced phospholipidosis to promote ocular surface health. Toxicology 2014;320:1-5. 3. Liu Y, Kam WR, Ding J, et al. The effect of macrolide and tetracycline antibiotics on lipid expression in human meibomian gland epithelial cells. ARVO abstract 2014.

    Conflict of Interest:

    A provisional patent has been filed around the technology mentioned in our paper. The intellectual property for the application is owned by the Schepens Eye Research Institute/Massachusetts Eye and Ear.

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  8. Reporting of harms in clinical trials: why do we continue to fail?

    O'Day and colleagues describe in their recent paper the inadequate reporting of harm in randomized controlled trials of intra-vitreal therapies for diabetic macular oedema(O'Day et al., 2014). At first glance, the results are alarming. An average of only six recommendations of the 2004 CONSORT guidelines extension covering harms were met. Ophthalmologists are not alone in their inadequate reporting, however. Several other studies have found similar, and often worse examples of heterogenous and selective reporting of harm in RCTs in psychological medicine(Jonsson et al., 2014), asthma(Ntala et al., 2013) and cancer(Sivendran et al., 2014). Why, then, are we falling so far short of these internationally agreed standards, and who is to blame?

    Some might argue that there are too many recommendations. The CONSORT guidelines have 25 points, of which one is harm reporting (with ten recommendations)(Schulz et al., 2010). Whilst most published RCTs do not report them all, many do report on half or more (interquartile range 5-7 for the ophthalmic studies cited)(O'Day et al., 2014). In any case, they remain "recommendations", not "requirements" In order to address this, the recommendations might be adapted to suggest full reporting be made publically available elsewhere to limit the length of published reports.

    Perhaps the authors of the RCTs published are to blame? Could it be that they simply do not the data needed to fulfill the ten requirements? Whilst it is possible, and in some cases may highlight the need for investment in training, most authors could likely fulfill more of the ten recommendations than they currently do, for example the number of patients withdrawn due to an adverse event (only 36% in ophthalmic trials)(O'Day et al., 2014), essential data that most investigators surely can trace(Ioannidis JA and Lau J, 2001).

    Finally, it might be argued that journal editors are to blame for failing to implement these standards. This may not be an option for all except editors of the minority of most desirable publications. Raising the bar too high may lead to authors taking their work elsewhere where they know it will be accepted.

    How, then, to move forward? Like many "culture change" challenges faced in modern medicine, the adequate adoption of such standards requires a concerted effort by all parties involved in the research-publication pathway. John Kotter's 8-step change model provides some insights as to how, including establishing a sense of urgency by highlighting the harms associated with poor reporting, and forming powerful coalitions(Kotter, 1996). Most importantly, however, we as researchers must champion the improvement of reporting standards in our own work and demand this of our peers. Only then can we hope for change.

    Ioannidis JA, and Lau J (2001). Completeness of safety reporting in randomized trials: An evaluation of 7 medical areas. JAMA 285, 437-443. Jonsson, U., Alaie, I., Parling, T., and Arnberg, F.K. (2014). Reporting of harms in randomized controlled trials of psychological interventions for mental and behavioral disorders: a review of current practice. Contemp. Clin. Trials 38, 1-8. Kotter, J.P. (1996). Leading Change (Harvard Business Press). Ntala, C., Birmpili, P., Worth, A., Anderson, N.H., and Sheikh, A. (2013). The quality of reporting of randomised controlled trials in asthma: a systematic review. Prim. Care Respir. J. J. Gen. Pract. Airw. Group 22, 417-424. O'Day, R., Walton, R., Blennerhassett, R., Gillies, M.C., and Barthelmes, D. (2014). Reporting of harms by randomised controlled trials in ophthalmology. Br. J. Ophthalmol. 98, 1003-1008. Schulz, K.F., Altman, D.G., and Moher, D. (2010). CONSORT 2010 Statement: Updated Guidelines for Reporting Parallel Group Randomized Trials. Ann. Intern. Med. 152, 726-732. Sivendran, S., Latif, A., McBride, R.B., Stensland, K.D., Wisnivesky, J., Haines, L., Oh, W.K., and Galsky, M.D. (2014). Adverse event reporting in cancer clinical trial publications. J. Clin. Oncol. Off. J. Am. Soc. Clin. Oncol. 32, 83-89.

    Conflict of Interest:

    None declared

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  9. Perceptual learning in visual acuity and contrast sensitivity: continuous improvement or discovery effect?

    In their paper "Repetitive tests of visual function improved visual acuity in young subjects" Otto and Michelson [1] assessed effects of practice on visual acuity, using the Freiburg Visual Acuity Test "FrACT" developed by one of us [2,3]. At first glance they seem to confirm our findings [4], which showed a marked increase of visual acuity after visual training, more than 0.1 logMAR. At closer inspection, discrepancies emerge: During the first 7 sessions, Otto and Michelson's found only a random variability. Then, suddenly, acuity improved in most subjects, and inter-subject variability decreased markedly. In contrast, we found a continuous improvement starting already during the first session (one session comprised 14 acuity test runs) [4]. When we provided feedback by displaying the correct orientation after the response, we found a marked additional step increase in performance already between the first and second session. (Otto and Michelson do not mention whether or not they employed feedback.) The shape of the time course has theoretical implications: A sudden increase of visual acuity like that reported by Otto and Michelson would suggest a "discovery effect" rather than a "fluency effect" [5].

    Otto and Michelson's data on contrast sensitivity are also challenging to understand, not only because the authors used the terms contrast threshold and contrast sensitivity interchangeably (the one is the reciprocal of the other). Looking at figure 1B and supplementary figure 2B, we suspect that the stated effect size of 45% (derived only from the last data point in the graph) can be attributed to random fluctuations, given the non-monotonous change of average contrast sensitivity over sessions. Otto and Michelson seem to share our reservation, since they write in the Discussion "the progress was not consistent enough to show a significant percentage development in one direction". Hopefully, this number 45% will not stick with readers, who could miss the fact that the p values where not derived from the same comparisons as the effect size.

    The reason why the learning curves of Otto and Michelson's subjects are different from those of Heinrich et al's subjects remains speculative. The methods appear to be similar. It is, however, unclear whether Otto and Michelson used feedback and whether or not they presented the optotypes separately or in rows. Furthermore, the participants underwent a practice scheme that included several different visual tasks, so it is difficult to attribute improvement of performance to any single task or combination of tasks. Clearly, future careful studies in this exciting field promise further insights and clinical applications.

    References

    1 Otto J, Michelson G. Repetitive tests of visual function improved visual acuity in young subjects. Br J Ophthalmol 2014;98:383-6. doi:10.1136/bjophthalmol-2013-304262

    2 Bach M. The Freiburg Visual Acuity Test - Automatic measurement of visual acuity. Optom Vis Sci 1996;73:49-53.

    3 Bach M. Homepage of the Freiburg Visual Acuity & Contrast Test ('FrACT'). 2009. http://michaelbach.de/fract.html

    4 Heinrich SP, Krueger K, Bach M. The dynamics of practice effects in an optotype acuity task. Graefes Arch Clin Exp Ophthalmol 2011;249:1319 -26. doi:10.1007/s00417-011-1675-z

    5 Kellman PJ, Garrigan P. Perceptual learning and human expertise. Phys Life Rev 2009;6:53-84. doi:10.1016/j.plrev.2008.12.001

    Conflict of Interest:

    None declared

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