5. dell’Omo R, Mura M, Lesnik Oberstein SY, Bijl HM, Tan HS. Early simultaneous fundus autofluorescence and optical coherence tomography features after pars plana vitrectomy for primary rhegmatogenous retinal detachment. Retina 2012;32(4):719–728. 6. dell’Omo R, Tan HS, Schlingemann RO, et al. Evolution of outer retinal folds occurring after vitrectomy for retinal detachment repair. Invest Ophthalmol Vis Sci 2012;53(13):7928–7935.
However, some other cases demonstrated metamorphopsia that was unexplainable by a transient retinal morphologic change. One patient exhibited normal-appearing OCT findings and severe metamorphopsia even 10 days after surgery. Future studies involving more evaluation points with shorter intervals may further facilitate our understanding about metamorphopsia after RD surgery. FUMIKI OKAMOTO
REPLY
YOSHIMI SUGIURA YOSHIFUMI OKAMOTO
WE THANK DRS DELL’OMO AND MURA FOR THEIR COM-
TAKAHIRO HIRAOKA
ments regarding our article. In almost all of our cases, we performed 5 horizontal and 5 vertical raster scans at least 3 times using spectral-domain optical coherence tomography (OCT), and selected a representative image centered on the fovea. In our results, 32 of the 50 metamorphopsic eyes (64%) after rhegmatogenous retinal detachment (RD) surgery exhibited normal-appearing OCT findings without any disruption of inner/outer segment (IS/OS), external limiting membrane (ELM), or abnormal macular contour.1 As Drs dell’Omo and Mura pointed out, outer retinal folds (ORFs) and IS/OS skip reflectivity abnormalities (RAs)2,3 might have been included in these 32 cases with normalappearing OCT. ORFs tend to resolve spontaneously within 6 months or less following vitrectomy. However, we evaluated the patients at 6-12 months postoperatively. Thus, it is difficult to detect transient retinal morphologic abnormalities occurring in the 6-month period after surgery. From the total of 32 cases with metamorphopsia and normal-appearing OCT, therefore, we extracted some cases whose OCT images were obtained within 6 months postoperatively. As a result, we were able to investigate OCT images within 1 month postoperatively in 5 of the 32 cases, and within 3 months postoperatively in 20 of the 32 cases. The results showed that 2 of the 32 cases had ORFs at the fovea at 3 months postoperatively. The ORFs resolved, but IS/OS skip RAs remained at 6 months postoperatively. Seven of the 32 cases had hyperreflective IS/OS line at the foveal region at 3 months postoperatively, of which the hyperreflective IS/OS line resolved at 6 months postoperatively in 5 cases and no change was observed in the other 2 cases. We are not sure whether the hyperreflective IS/OS line in these 7 cases had ORFs within 3 months postoperatively. Nine of the 20 cases whose OCT images were obtained at 3 months postoperatively had neither ORFs nor IS/OS skip RAs. It could be considered that certain retinal morphologic abnormalities existed in these cases within 3 months following surgery. dell’Omo and associates found that the presence of ORFs was associated with metamorphopsia.2 In consideration of our results and those of the previous report, our findings suggested that transient retinal morphologic abnormalities such as ORFs and IS/OS skip RAs occurred within 6 months after operation and caused metamorphopsia in some of the cases with ‘‘normal-appearing OCT.’’
TETSURO OSHIKA
VOL. 157, NO. 6
Ibaraki, Japan CONFLICT OF INTEREST DISCLOSURES: SEE THE ORIGINAL article1 for any disclosures of the authors.
REFERENCES
1. Okamoto F, Sugiura Y, Okamoto Y, Hiraoka T, Oshika T. Metamorphopsia and optical coherence tomography findings after rhegmatogenous retinal detachment surgery. Am J Ophthalmol 2014;157(1):214–220. 2. dell’Omo R, Mura M, Lesnik Oberstein SY, Bijl HM, Tan HS. Early simultaneous fundus autofluorescence and optical coherence tomography features after pars plana vitrectomy for primary rhegmatogenous retinal detachment. Retina 2012; 32(4):719–728. 3. dell’Omo R, Tan HS, Schlingemann RO, et al. Evolution of outer retinal folds occurring after vitrectomy for retinal detachment repair. Invest Ophthalmol Vis Sci 2012;53(13):7928–7935.
Impact of Crystalline Lens Opacification on Effective Phacoemulsification Time in Femtosecond Laser–Assisted Cataract Surgery EDITOR: WE WOULD LIKE TO THANK MAYER AND ASSOCIATES1 FOR
describing reduction of ultrasound energy with femtosecond laser phacofragmentation. However, the authors’ methodology is ambiguous and may ignore the contribution of torsional power during phacoemulsification. Mayer and associates used the Infiniti Vision System (Alcon, Inc, Ft. Worth, Texas, USA). Ambiguity results because the Infiniti Metrics Display does not provide Effective Phaco Time (EPT). Rather, it provides Phaco Time, defined as the ‘‘total time phaco power was active,’’ and 2 metrics of phaco power, ‘‘Average Phaco Power’’ and ‘‘Average Phaco Power in Position 3.’’ Average Phaco Power is defined as ‘‘Average phaco power over time when
CORRESPONDENCE
1323
phaco power was applied. For example, if Ultrasound Burst mode was selected and 100 mS burst pulses at 70% stroke were generated once a second, the Average Power would record 70%.’’ Average Phaco Power in Position 3, on the other hand, represents ‘‘Average phaco power over time when phaco power was applied in foot pedal position 3. This takes into account the U/S modulation aspects, resulting in a significantly lower reading than Average phaco power. For example, if Ultrasound Burst mode was selected and 100 mS burst pulses at 70% stroke were generated once a second, the Average Power in Position 3 would record 7%.’’2 It is unclear whether Mayer and associates used Average Phaco Power or Average Phaco Power in Position 3. If they used any modality other than Continuous Phaco, the latter would have been more appropriate. The authors’ ‘‘divide and conquer’’ combination of sculpting, cracking, and quadrant removal might have involved multiple power modulations, which would further suggest the use of Average Phaco Power in Position 3 as the more appropriate metric. Any contribution of torsional power in the authors’ methodology may have been neglected if they used the OZil modality. In January 2006, Alcon Surgical incorporated OZil torsional technology into the Infiniti Vision System.3 Other authors who have written about ultrasound reduction after femtosecond laser phacofragmentation have referred to Cumulative Dissipated Energy (CDE).4 CDE represents the ‘‘Total U/S energy in footpedal position 3 (both phaco and torsional) calculated as: (Phaco Time 3 Average Phaco Power) þ (Torsional Time 3 0.4 3 Average Torsional Amplitude).’’2 In general, metrics for ultrasound phacoemulsification such as percentage phaco power, EPT, and CDE remain proprietary and unique to each manufacturer, much as they were over a decade ago, when it was written that ‘‘Although outcomes such as slit lamp examination and visual acuity may be fairly represented as comparative, we caution against using EPT and average power for drawing conclusions about the relative efficiency of different phaco machines.. Because manufacturers may use different algorithms to calculate these quantities, comparison among different machines remains fraught with difficulty.’’5 With the increasing utilization of reduction in ultrasound energy as a means to compare the effectiveness of various femtosecond laser phacofragmentation platforms, it is imperative that authors pay scrupulous attention to the definitions of the language that they use. MARK PACKER JONATHAN D. SOLOMON
Bowie, Maryland BOTH AUTHORS HAVE COMPLETED AND SUBMITTED THE ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Packer is a consultant to Abbott Medical Optics, Inc; Bausch & Lomb (Valeant Pharmaceuticals International, Inc); and Lensar, Inc. The authors report no funding support.
1324
REFERENCES
1. Mayer WJ, Klaproth OK, Hengerer FH, Kohnen T. Impact of crystalline lens opacification on effective phacoemulsification time in femtosecond laser-assisted cataract surgery. Am J Ophthalmol 2014;157(2):426–432.e1. 2. INFINITI Vision System Directions for Use. Document 8065751606. Alcon, Inc, 2009-10. 3. Helvacioglu F, Yeter C, Tunc Z, Sencan S. Outcomes of torsional microcoaxial phacoemulsification performed by 12degree and 22-degree bent tips. J Cataract Refract Surg 2013; 39(8):1219–1225. 4. Chang JS, Chen IN, Chan WM, Ng JC, Chan VK, Law AK. Initial evaluation of a femtosecond laser system in cataract surgery. J Cataract Refract Surg 2014;40(1):29–36. 5. Fine IH, Packer M, Hoffman RS. Power modulations in new phacoemulsification technology: improved outcomes. J Cataract Refract Surg 2004;30(5):1014–1019.
REPLY IN OUR STUDY WE ASSESSED PREOPERATIVE CATARACT
grades in manual and femtosecond laser–assisted cataract surgery and evaluated its influence on effective phacoemulsification times. For phacoemulsification the Infinity System was used (Alcon, Fort Worth, Texas, USA).1 The effective phacoemulsification time (EPT) is determined by multiplying the phacoemulsification time (seconds) with the average phacoemulsification power (percent).2 In contrast to EPT, the cumulative dissipated energy (CDE) reflects the total U/S energy in footpedal position 3 and includes phaco and torsional times. At present, no phaco platform offers surgeons a direct or standard measure of the energy that is placed into the eye during cataract surgery in units such as Joules.3 As mentioned by Drs Packer and Solomon, the Infinity system includes the OZil torsional technology, which features both longitudinal and torsional ultrasound delivery. OZil torsional technology produces a side-to-side motion of the phaco tip to break up the nucleus by shearing.4 We are aware that we did not describe this feature in our study settings, as it is a standard technique setting of the Infinity system. For our study purposes the average phaco power and phaco time was assessed in footpedal position 3 to calculate EPT, as EPT is commonly used in this context regardless of the type of power modulation or lens segmentation technique. The lens segmentation was undertaken in both treatment groups using a divide-and-conquer approach. We agree that it is difficult to compare different phaco machines because manufacturers may use different algorithms to calculate EPT or CDE quantities.
AMERICAN JOURNAL OF OPHTHALMOLOGY
JUNE 2014
However, some other cases demonstrated metamorphopsia that was unexplainable by a transient retinal morphologic change. One patient exhibited normal-appearing OCT findings and severe metamorphopsia even 10 days after surgery. Future studies involving more evaluation points with shorter intervals may further facilitate our understanding about metamorphopsia after RD surgery. FUMIKI OKAMOTO
REPLY
YOSHIMI SUGIURA YOSHIFUMI OKAMOTO
WE THANK DRS DELL’OMO AND MURA FOR THEIR COM-
TAKAHIRO HIRAOKA
ments regarding our article. In almost all of our cases, we performed 5 horizontal and 5 vertical raster scans at least 3 times using spectral-domain optical coherence tomography (OCT), and selected a representative image centered on the fovea. In our results, 32 of the 50 metamorphopsic eyes (64%) after rhegmatogenous retinal detachment (RD) surgery exhibited normal-appearing OCT findings without any disruption of inner/outer segment (IS/OS), external limiting membrane (ELM), or abnormal macular contour.1 As Drs dell’Omo and Mura pointed out, outer retinal folds (ORFs) and IS/OS skip reflectivity abnormalities (RAs)2,3 might have been included in these 32 cases with normalappearing OCT. ORFs tend to resolve spontaneously within 6 months or less following vitrectomy. However, we evaluated the patients at 6-12 months postoperatively. Thus, it is difficult to detect transient retinal morphologic abnormalities occurring in the 6-month period after surgery. From the total of 32 cases with metamorphopsia and normal-appearing OCT, therefore, we extracted some cases whose OCT images were obtained within 6 months postoperatively. As a result, we were able to investigate OCT images within 1 month postoperatively in 5 of the 32 cases, and within 3 months postoperatively in 20 of the 32 cases. The results showed that 2 of the 32 cases had ORFs at the fovea at 3 months postoperatively. The ORFs resolved, but IS/OS skip RAs remained at 6 months postoperatively. Seven of the 32 cases had hyperreflective IS/OS line at the foveal region at 3 months postoperatively, of which the hyperreflective IS/OS line resolved at 6 months postoperatively in 5 cases and no change was observed in the other 2 cases. We are not sure whether the hyperreflective IS/OS line in these 7 cases had ORFs within 3 months postoperatively. Nine of the 20 cases whose OCT images were obtained at 3 months postoperatively had neither ORFs nor IS/OS skip RAs. It could be considered that certain retinal morphologic abnormalities existed in these cases within 3 months following surgery. dell’Omo and associates found that the presence of ORFs was associated with metamorphopsia.2 In consideration of our results and those of the previous report, our findings suggested that transient retinal morphologic abnormalities such as ORFs and IS/OS skip RAs occurred within 6 months after operation and caused metamorphopsia in some of the cases with ‘‘normal-appearing OCT.’’
TETSURO OSHIKA
VOL. 157, NO. 6
Ibaraki, Japan CONFLICT OF INTEREST DISCLOSURES: SEE THE ORIGINAL article1 for any disclosures of the authors.
REFERENCES
1. Okamoto F, Sugiura Y, Okamoto Y, Hiraoka T, Oshika T. Metamorphopsia and optical coherence tomography findings after rhegmatogenous retinal detachment surgery. Am J Ophthalmol 2014;157(1):214–220. 2. dell’Omo R, Mura M, Lesnik Oberstein SY, Bijl HM, Tan HS. Early simultaneous fundus autofluorescence and optical coherence tomography features after pars plana vitrectomy for primary rhegmatogenous retinal detachment. Retina 2012; 32(4):719–728. 3. dell’Omo R, Tan HS, Schlingemann RO, et al. Evolution of outer retinal folds occurring after vitrectomy for retinal detachment repair. Invest Ophthalmol Vis Sci 2012;53(13):7928–7935.
Impact of Crystalline Lens Opacification on Effective Phacoemulsification Time in Femtosecond Laser–Assisted Cataract Surgery EDITOR: WE WOULD LIKE TO THANK MAYER AND ASSOCIATES1 FOR
describing reduction of ultrasound energy with femtosecond laser phacofragmentation. However, the authors’ methodology is ambiguous and may ignore the contribution of torsional power during phacoemulsification. Mayer and associates used the Infiniti Vision System (Alcon, Inc, Ft. Worth, Texas, USA). Ambiguity results because the Infiniti Metrics Display does not provide Effective Phaco Time (EPT). Rather, it provides Phaco Time, defined as the ‘‘total time phaco power was active,’’ and 2 metrics of phaco power, ‘‘Average Phaco Power’’ and ‘‘Average Phaco Power in Position 3.’’ Average Phaco Power is defined as ‘‘Average phaco power over time when
CORRESPONDENCE
1323
phaco power was applied. For example, if Ultrasound Burst mode was selected and 100 mS burst pulses at 70% stroke were generated once a second, the Average Power would record 70%.’’ Average Phaco Power in Position 3, on the other hand, represents ‘‘Average phaco power over time when phaco power was applied in foot pedal position 3. This takes into account the U/S modulation aspects, resulting in a significantly lower reading than Average phaco power. For example, if Ultrasound Burst mode was selected and 100 mS burst pulses at 70% stroke were generated once a second, the Average Power in Position 3 would record 7%.’’2 It is unclear whether Mayer and associates used Average Phaco Power or Average Phaco Power in Position 3. If they used any modality other than Continuous Phaco, the latter would have been more appropriate. The authors’ ‘‘divide and conquer’’ combination of sculpting, cracking, and quadrant removal might have involved multiple power modulations, which would further suggest the use of Average Phaco Power in Position 3 as the more appropriate metric. Any contribution of torsional power in the authors’ methodology may have been neglected if they used the OZil modality. In January 2006, Alcon Surgical incorporated OZil torsional technology into the Infiniti Vision System.3 Other authors who have written about ultrasound reduction after femtosecond laser phacofragmentation have referred to Cumulative Dissipated Energy (CDE).4 CDE represents the ‘‘Total U/S energy in footpedal position 3 (both phaco and torsional) calculated as: (Phaco Time 3 Average Phaco Power) þ (Torsional Time 3 0.4 3 Average Torsional Amplitude).’’2 In general, metrics for ultrasound phacoemulsification such as percentage phaco power, EPT, and CDE remain proprietary and unique to each manufacturer, much as they were over a decade ago, when it was written that ‘‘Although outcomes such as slit lamp examination and visual acuity may be fairly represented as comparative, we caution against using EPT and average power for drawing conclusions about the relative efficiency of different phaco machines.. Because manufacturers may use different algorithms to calculate these quantities, comparison among different machines remains fraught with difficulty.’’5 With the increasing utilization of reduction in ultrasound energy as a means to compare the effectiveness of various femtosecond laser phacofragmentation platforms, it is imperative that authors pay scrupulous attention to the definitions of the language that they use. MARK PACKER JONATHAN D. SOLOMON
Bowie, Maryland BOTH AUTHORS HAVE COMPLETED AND SUBMITTED THE ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Packer is a consultant to Abbott Medical Optics, Inc; Bausch & Lomb (Valeant Pharmaceuticals International, Inc); and Lensar, Inc. The authors report no funding support.
1324
REFERENCES
1. Mayer WJ, Klaproth OK, Hengerer FH, Kohnen T. Impact of crystalline lens opacification on effective phacoemulsification time in femtosecond laser-assisted cataract surgery. Am J Ophthalmol 2014;157(2):426–432.e1. 2. INFINITI Vision System Directions for Use. Document 8065751606. Alcon, Inc, 2009-10. 3. Helvacioglu F, Yeter C, Tunc Z, Sencan S. Outcomes of torsional microcoaxial phacoemulsification performed by 12degree and 22-degree bent tips. J Cataract Refract Surg 2013; 39(8):1219–1225. 4. Chang JS, Chen IN, Chan WM, Ng JC, Chan VK, Law AK. Initial evaluation of a femtosecond laser system in cataract surgery. J Cataract Refract Surg 2014;40(1):29–36. 5. Fine IH, Packer M, Hoffman RS. Power modulations in new phacoemulsification technology: improved outcomes. J Cataract Refract Surg 2004;30(5):1014–1019.
REPLY IN OUR STUDY WE ASSESSED PREOPERATIVE CATARACT
grades in manual and femtosecond laser–assisted cataract surgery and evaluated its influence on effective phacoemulsification times. For phacoemulsification the Infinity System was used (Alcon, Fort Worth, Texas, USA).1 The effective phacoemulsification time (EPT) is determined by multiplying the phacoemulsification time (seconds) with the average phacoemulsification power (percent).2 In contrast to EPT, the cumulative dissipated energy (CDE) reflects the total U/S energy in footpedal position 3 and includes phaco and torsional times. At present, no phaco platform offers surgeons a direct or standard measure of the energy that is placed into the eye during cataract surgery in units such as Joules.3 As mentioned by Drs Packer and Solomon, the Infinity system includes the OZil torsional technology, which features both longitudinal and torsional ultrasound delivery. OZil torsional technology produces a side-to-side motion of the phaco tip to break up the nucleus by shearing.4 We are aware that we did not describe this feature in our study settings, as it is a standard technique setting of the Infinity system. For our study purposes the average phaco power and phaco time was assessed in footpedal position 3 to calculate EPT, as EPT is commonly used in this context regardless of the type of power modulation or lens segmentation technique. The lens segmentation was undertaken in both treatment groups using a divide-and-conquer approach. We agree that it is difficult to compare different phaco machines because manufacturers may use different algorithms to calculate EPT or CDE quantities.
AMERICAN JOURNAL OF OPHTHALMOLOGY
JUNE 2014
