LETTERS
Vector analysis with the femtosecond laser The paper by Kunert et al.,1 using vector analysis in patients receiving refractive lenticule extraction with a femtosecond laser has generated criticism related to attribution2,3 and interpretation.4 In their replies to these letters,2–4 Kunert et al. were straightforward in acknowledging shortcomings and defending their methods and analyses. However, as the author of the basic analytic techniques used in the study, as well as the original terminology used in the approach,5–8 I believe the replies were insufficient and that additional clarifications are needed. Kunert et al.1 wrote that the vector analysis in their study “was calculated on the refractive data that mainly followed the definitions and formulas given by Eydelman et al.”9 comprised for the Astigmatism Project Group of the American National Standards Institute and according to the then editor of the Journal of Refractive Surgery, the 2006 publication was a “Special Article” that did “not qualify for peer review.”10 A critical reading of this non-peer-reviewed paper reveals the obvious conclusion that the formulas and definitions were not “given” by Eydelman et al.; in fact, the formulas duplicated those from my previous publications and the definitions were minor and unnecessary rewording of those I published previously.5–8 Kunert et al.1 perpetrate a further oversight in describing the “different approaches” that have been published to derive a nomogram for astigmatism correction. They correctly note that I proposed the use of a coefficient of adjustment (CA),7 defined as the ratio of the intended to the induced astigmatism. They go on to write that the CA corresponds to the inverse of the correction ratio (CR) as defined by Eydelman et al.9 The CR described by Eydelman et al.9 is, in fact, a minor rewording of my previously described correction index.6,7 Although the non-peer-reviewed paper by Eydelman et al.9 does not seem to have been widely cited thus far, it concerns me that it may become a de facto standard for astigmatism analysis. Others have noted the inadequacy of its referencing.11,12 Its use of nonzero targets was described in my 1993 publication,5 and the terminology it offers reflects minor rewording of terms defined many years previously, and thus only foments confusion among those who wish to use or report vector-based astigmatism analysis in a consistent way. The intent of the original Astigmatism Project Group was to provide a regulatory framework for reporting and evaluating laser systems to treat astigmatism and would more appropriately have been published in a governmental bulletin of some kind. These issues have been addressed in past correspondence and editorials8,11–15 generated by Eydelman 1246
Q 2014 ASCRS and ESCRS Published by Elsevier Inc.
et al.9 It is unfortunate that potentially good science can be overshadowed by neglecting the fundamentals of accurate sourcing and reporting of data. I am disappointed that during the 6-month review period of the Kunert et al.1 paper, reviewers did not bring these deficiencies to the authors' attention. The net result of systematic failures such as happened here is that authors and their articles become notable for all the wrong reasons. Noel Alpins, FRANZCO, FRCOphth, FACS Cheltenham, Victoria, Australia Dr Alpins is the innovator of the astigmatism analysis of the Alpins Method. He has developed the Assort Surgical Management Systems (Assort Pty. Ltd. Melbourne, Australia) with a financial interest in this group of software products to assist doctors in the application of the technique.
REFERENCES 1. Kunert KS, Russmann C, Blum M, Sluyterman vLG. Vector analysis of myopic astigmatism correct by femtosecond refractive lenticule extraction. J Cataract Refract Surg 2013; 39:759–769 2. Goggin M. Vector analysis terminology [letter]. J Cataract Refract Surg 2013; 39:1626–1627; reply by KS Kunet, C Russmann, M Blum, G Sluytermann v. L., 1627 ~ ero DP. Terminology and referencing of astigmatic vector 3. Pin analysis [letter]. J Cataract Refract Surg 2013; 39:1792; reply by KS Kunet, C Russmann, M Blum, G Sluytermann v. L., 1792–1793 4. Holladay JT. Interpretation of doubled-angle plots [letter]. J Cataract Refract Surg 2013; 39:1627–1628; reply by KS Kunet, C Russmann, M Blum, G Sluytermann v. L., 1628 5. Alpins NA. A new method of analyzing vectors for changes in astigmatism. J Cataract Refract Surg 1993; 19:524–533 6. Alpins NA. New method of targeting vectors to treat astigmatism. J Cataract Refract Surg 1997; 23:65–75 7. Alpins N. Astigmatism analysis by the Alpins method. J Cataract Refract Surg 2001; 27:31–49 8. Alpins N. Terms used for the analysis of astigmatism [letter]. J Refract Surg 2006; 22:528; reply by MB Eydelman, B Drum, J Holladay, G Kezirian, D Durrie, RD Stulting, D Sanders, B Wong, Astigmatism Project Group, 528–529 9. Eydelman MB, Drum B, Holladay JT, Hilmantel G, Kezirian G, Durrie D, Stulting RD, Sanders D, Wong B. Standardized analyses or correction of astigmatism by laser systems that reshape the cornea. J Refract Surg 2006; 22:81–95 10. Waring GO III. Review process for special articles [editor’s comment]. J Refract Surg 2006; 22:529 11. Koch DD. Astigmatism analysis: the spectrum of approaches [editorial]. J Cataract Refract Surg 2006; 32:1977–1978 12. Dupps WJ Jr. Impact of citation practices: beyond journal impact factors [editorial]. J Cataract Refract Surg 2008; 34:1419–1421 13. Lenton L. Standardized analyses of correction of astigmatism [letter]. J Refract Surg 2006; 22:636–638; reply by MB Eydelman, B Drum, J Holladay, G Hilmantel, G Kezirian, D Durrie, RD Stulting, D Sanders, B Wong, Astigmatism Project Group, 638 14. Goggin M. More on astigmatism analysis [letter]. J Refract Surg 2007; 23:430; reply by MB Eydelman, B Drum, J Holladay, G
0886-3350/$ - see front matter http://dx.doi.org/10.1016/j.jcrs.2014.05.014
1247
LETTERS
Kezirian, D Durrie, RD Stulting, D Sanders, B Wong, Astigmatism Project Group, 430–431 15. Masket S. Special articles and peer review [letter]. J Refract Surg 2007; 23:115; reply by Waring GO III, 115
Editors Note: We agree: It is important to recognize and reference Alpins5 pioneering work in this area and particularly the analytical system that he developed, a modified version of which was described by Eydelman et al. For purposes of clarity and consistency with the majority of papers that use this type of analysis, we recommend that authors use Alpins5 original terms and equations.
Risk for longer suction-on times in femtosecond laser–assisted cataract surgery The March 2014 issue included 2 reports of the same complication of inadvertent femtosecond lasering of the cornea when suction loss was encountered during femtosecond fragmentation.1,2 In the same issue, I reported the differing suction-on times of 3 of the major femtosecond laser phaco platforms, highlighting that the Lensx suction-on time was less than half that of the other platforms discussed.3 In her reply to my letter, Donaldson3 commented that “the clinical significance of the duration of IOP [intraocular pressure] increase is likely to be minimal.” As far as the risk of the low increases of IOP to the optic nerve in glaucoma patients is concerned, I concur that the risk to the optic nerve is not great, but it is probably also not zero. Because of the word limitation of a letter, I was unable to highlight that the other significant issue with prolonged suction time is that it exposes the eye to greater risk for suction loss and consequent complications. This is amply demonstrated in the 2 cases described by Schultz and Dick1 and Lubahn et al.2 Both occurred in patients using the grid modality of treatment, which takes more time than quadrant division alone. Fortunately, the lasered grid pattern was in the corneal peripheries in both cases with no visual detriment. In their case report, Lubahn et al.2 state that the treatment time was 58.2 seconds. Treatment time is a slightly misleading term as it ignores the time between the suction cup being applied to the eye and swinging the patient under the microscope, positioning, docking, and planning prior to the actual start of the treatment. Clearly, if these other steps are taken into consideration, the suction-on time (which is actually a better term to use than dock duration because docking does not mean the same thing for the different platforms) will be much longer and not less than a minute
as suggested. It stands to reason that the longer the suction-on time, the greater the risk for suction loss. All femtosecond phaco platforms can do a 4-quadrant or more nuclear fragmentation pattern. The Catalys has had the grid pattern of nuclear softening available since introduction to the market and this will be introduced in the Lensx shortly. While I believe that this nuclear softening is helpful in reducing ultrasound energy usage in denser cataracts, the advantages of nuclear softening in an already soft nucleus are minimal. This is important because doing an extra grid pattern of treatment on top of quadrant division increases the suction-on time. Each surgeon therefore needs to make a judgment call as to whether this prolongation of nuclear fragmentation is worth the increased risk of longer suction-on time, especially in softer cataracts. Suction loss during femtosecond laser–assisted cataract surgery is multifactorial; there are patient factors such as deep-set eyes with narrow palpebral apertures and nervous patients who squeeze their eyelids. The suction-on time is something we can minimize immediately by choosing an appropriate platform or by using a fragmentation pattern that is appropriate to the nuclear density. Ronald Yeoh, FRCS (Glas), FRCS (Ed), FRCOphth(UK), FAM(Singapore) Singapore Dr. Yeoh is on the speaker panels of Alcon Laboratories, Inc., and Abbott Medical Optics, Inc.
REFERENCES 1. Schultz T, Dick HB. Suction loss during femtosecond laser– assisted cataract surgery. J Cataract Refract Surg 2014; 40:493–495 2. Lubahn JG, Kankariya VP, Yoo SH. Grid pattern delivered to the cornea during femtosecond laser–assisted cataract surgery. J Cataract Refract Surg 2014; 40:496–497 3. Yeoh R. Practical differences between 3 femtosecond phaco laser platforms [letter]. J Cataract Refract Surg 2014; 40:510; reply by KE Donaldson, 510–511
Reply : Dr. Yeoh provides a valuable contribution to the emerging topic of possible complications in femtosecond laser–assisted cataract surgery. As surgeons working with that technology, we would like to express our appreciation to every colleague who, like Dr. Yeoh, adds to our knowledge of the dangers that might be lurking while we explore the potentials, but also the limits, of that evolving technology. Recently, Dr. Yeoh shared his experience with 3 laser platforms and described the different suction-on times of these lasers (Catalys Precision Laser System, Lensx,
J CATARACT REFRACT SURG - VOL 40, JULY 2014
Vector analysis with the femtosecond laser The paper by Kunert et al.,1 using vector analysis in patients receiving refractive lenticule extraction with a femtosecond laser has generated criticism related to attribution2,3 and interpretation.4 In their replies to these letters,2–4 Kunert et al. were straightforward in acknowledging shortcomings and defending their methods and analyses. However, as the author of the basic analytic techniques used in the study, as well as the original terminology used in the approach,5–8 I believe the replies were insufficient and that additional clarifications are needed. Kunert et al.1 wrote that the vector analysis in their study “was calculated on the refractive data that mainly followed the definitions and formulas given by Eydelman et al.”9 comprised for the Astigmatism Project Group of the American National Standards Institute and according to the then editor of the Journal of Refractive Surgery, the 2006 publication was a “Special Article” that did “not qualify for peer review.”10 A critical reading of this non-peer-reviewed paper reveals the obvious conclusion that the formulas and definitions were not “given” by Eydelman et al.; in fact, the formulas duplicated those from my previous publications and the definitions were minor and unnecessary rewording of those I published previously.5–8 Kunert et al.1 perpetrate a further oversight in describing the “different approaches” that have been published to derive a nomogram for astigmatism correction. They correctly note that I proposed the use of a coefficient of adjustment (CA),7 defined as the ratio of the intended to the induced astigmatism. They go on to write that the CA corresponds to the inverse of the correction ratio (CR) as defined by Eydelman et al.9 The CR described by Eydelman et al.9 is, in fact, a minor rewording of my previously described correction index.6,7 Although the non-peer-reviewed paper by Eydelman et al.9 does not seem to have been widely cited thus far, it concerns me that it may become a de facto standard for astigmatism analysis. Others have noted the inadequacy of its referencing.11,12 Its use of nonzero targets was described in my 1993 publication,5 and the terminology it offers reflects minor rewording of terms defined many years previously, and thus only foments confusion among those who wish to use or report vector-based astigmatism analysis in a consistent way. The intent of the original Astigmatism Project Group was to provide a regulatory framework for reporting and evaluating laser systems to treat astigmatism and would more appropriately have been published in a governmental bulletin of some kind. These issues have been addressed in past correspondence and editorials8,11–15 generated by Eydelman 1246
Q 2014 ASCRS and ESCRS Published by Elsevier Inc.
et al.9 It is unfortunate that potentially good science can be overshadowed by neglecting the fundamentals of accurate sourcing and reporting of data. I am disappointed that during the 6-month review period of the Kunert et al.1 paper, reviewers did not bring these deficiencies to the authors' attention. The net result of systematic failures such as happened here is that authors and their articles become notable for all the wrong reasons. Noel Alpins, FRANZCO, FRCOphth, FACS Cheltenham, Victoria, Australia Dr Alpins is the innovator of the astigmatism analysis of the Alpins Method. He has developed the Assort Surgical Management Systems (Assort Pty. Ltd. Melbourne, Australia) with a financial interest in this group of software products to assist doctors in the application of the technique.
REFERENCES 1. Kunert KS, Russmann C, Blum M, Sluyterman vLG. Vector analysis of myopic astigmatism correct by femtosecond refractive lenticule extraction. J Cataract Refract Surg 2013; 39:759–769 2. Goggin M. Vector analysis terminology [letter]. J Cataract Refract Surg 2013; 39:1626–1627; reply by KS Kunet, C Russmann, M Blum, G Sluytermann v. L., 1627 ~ ero DP. Terminology and referencing of astigmatic vector 3. Pin analysis [letter]. J Cataract Refract Surg 2013; 39:1792; reply by KS Kunet, C Russmann, M Blum, G Sluytermann v. L., 1792–1793 4. Holladay JT. Interpretation of doubled-angle plots [letter]. J Cataract Refract Surg 2013; 39:1627–1628; reply by KS Kunet, C Russmann, M Blum, G Sluytermann v. L., 1628 5. Alpins NA. A new method of analyzing vectors for changes in astigmatism. J Cataract Refract Surg 1993; 19:524–533 6. Alpins NA. New method of targeting vectors to treat astigmatism. J Cataract Refract Surg 1997; 23:65–75 7. Alpins N. Astigmatism analysis by the Alpins method. J Cataract Refract Surg 2001; 27:31–49 8. Alpins N. Terms used for the analysis of astigmatism [letter]. J Refract Surg 2006; 22:528; reply by MB Eydelman, B Drum, J Holladay, G Kezirian, D Durrie, RD Stulting, D Sanders, B Wong, Astigmatism Project Group, 528–529 9. Eydelman MB, Drum B, Holladay JT, Hilmantel G, Kezirian G, Durrie D, Stulting RD, Sanders D, Wong B. Standardized analyses or correction of astigmatism by laser systems that reshape the cornea. J Refract Surg 2006; 22:81–95 10. Waring GO III. Review process for special articles [editor’s comment]. J Refract Surg 2006; 22:529 11. Koch DD. Astigmatism analysis: the spectrum of approaches [editorial]. J Cataract Refract Surg 2006; 32:1977–1978 12. Dupps WJ Jr. Impact of citation practices: beyond journal impact factors [editorial]. J Cataract Refract Surg 2008; 34:1419–1421 13. Lenton L. Standardized analyses of correction of astigmatism [letter]. J Refract Surg 2006; 22:636–638; reply by MB Eydelman, B Drum, J Holladay, G Hilmantel, G Kezirian, D Durrie, RD Stulting, D Sanders, B Wong, Astigmatism Project Group, 638 14. Goggin M. More on astigmatism analysis [letter]. J Refract Surg 2007; 23:430; reply by MB Eydelman, B Drum, J Holladay, G
0886-3350/$ - see front matter http://dx.doi.org/10.1016/j.jcrs.2014.05.014
1247
LETTERS
Kezirian, D Durrie, RD Stulting, D Sanders, B Wong, Astigmatism Project Group, 430–431 15. Masket S. Special articles and peer review [letter]. J Refract Surg 2007; 23:115; reply by Waring GO III, 115
Editors Note: We agree: It is important to recognize and reference Alpins5 pioneering work in this area and particularly the analytical system that he developed, a modified version of which was described by Eydelman et al. For purposes of clarity and consistency with the majority of papers that use this type of analysis, we recommend that authors use Alpins5 original terms and equations.
Risk for longer suction-on times in femtosecond laser–assisted cataract surgery The March 2014 issue included 2 reports of the same complication of inadvertent femtosecond lasering of the cornea when suction loss was encountered during femtosecond fragmentation.1,2 In the same issue, I reported the differing suction-on times of 3 of the major femtosecond laser phaco platforms, highlighting that the Lensx suction-on time was less than half that of the other platforms discussed.3 In her reply to my letter, Donaldson3 commented that “the clinical significance of the duration of IOP [intraocular pressure] increase is likely to be minimal.” As far as the risk of the low increases of IOP to the optic nerve in glaucoma patients is concerned, I concur that the risk to the optic nerve is not great, but it is probably also not zero. Because of the word limitation of a letter, I was unable to highlight that the other significant issue with prolonged suction time is that it exposes the eye to greater risk for suction loss and consequent complications. This is amply demonstrated in the 2 cases described by Schultz and Dick1 and Lubahn et al.2 Both occurred in patients using the grid modality of treatment, which takes more time than quadrant division alone. Fortunately, the lasered grid pattern was in the corneal peripheries in both cases with no visual detriment. In their case report, Lubahn et al.2 state that the treatment time was 58.2 seconds. Treatment time is a slightly misleading term as it ignores the time between the suction cup being applied to the eye and swinging the patient under the microscope, positioning, docking, and planning prior to the actual start of the treatment. Clearly, if these other steps are taken into consideration, the suction-on time (which is actually a better term to use than dock duration because docking does not mean the same thing for the different platforms) will be much longer and not less than a minute
as suggested. It stands to reason that the longer the suction-on time, the greater the risk for suction loss. All femtosecond phaco platforms can do a 4-quadrant or more nuclear fragmentation pattern. The Catalys has had the grid pattern of nuclear softening available since introduction to the market and this will be introduced in the Lensx shortly. While I believe that this nuclear softening is helpful in reducing ultrasound energy usage in denser cataracts, the advantages of nuclear softening in an already soft nucleus are minimal. This is important because doing an extra grid pattern of treatment on top of quadrant division increases the suction-on time. Each surgeon therefore needs to make a judgment call as to whether this prolongation of nuclear fragmentation is worth the increased risk of longer suction-on time, especially in softer cataracts. Suction loss during femtosecond laser–assisted cataract surgery is multifactorial; there are patient factors such as deep-set eyes with narrow palpebral apertures and nervous patients who squeeze their eyelids. The suction-on time is something we can minimize immediately by choosing an appropriate platform or by using a fragmentation pattern that is appropriate to the nuclear density. Ronald Yeoh, FRCS (Glas), FRCS (Ed), FRCOphth(UK), FAM(Singapore) Singapore Dr. Yeoh is on the speaker panels of Alcon Laboratories, Inc., and Abbott Medical Optics, Inc.
REFERENCES 1. Schultz T, Dick HB. Suction loss during femtosecond laser– assisted cataract surgery. J Cataract Refract Surg 2014; 40:493–495 2. Lubahn JG, Kankariya VP, Yoo SH. Grid pattern delivered to the cornea during femtosecond laser–assisted cataract surgery. J Cataract Refract Surg 2014; 40:496–497 3. Yeoh R. Practical differences between 3 femtosecond phaco laser platforms [letter]. J Cataract Refract Surg 2014; 40:510; reply by KE Donaldson, 510–511
Reply : Dr. Yeoh provides a valuable contribution to the emerging topic of possible complications in femtosecond laser–assisted cataract surgery. As surgeons working with that technology, we would like to express our appreciation to every colleague who, like Dr. Yeoh, adds to our knowledge of the dangers that might be lurking while we explore the potentials, but also the limits, of that evolving technology. Recently, Dr. Yeoh shared his experience with 3 laser platforms and described the different suction-on times of these lasers (Catalys Precision Laser System, Lensx,
J CATARACT REFRACT SURG - VOL 40, JULY 2014
