- Email: [email protected]
Discussion by I. Howard Fine, MD
Ho¨h and Fischer 䡠 Erbium Laser Phacoemulsification 12. Wetzel W, Brinkmann R, Koop N, et al. Laserphakoemulsifikation mit dem Er:YAG-Laser. In: Vo¨ro¨smarthy et al, eds. Kongreß der deutschsprachigen Gesellschaft fu¨r Intraokularlinsenimplantation und refraktive Chirurgie, Vol. 10. Berlin: Springer, 1997:356 –9. 13. DeBry P, Olson RJ, Crandall AS. Comparison of energy required for phaco-chop and divide and conquer phacoemulsification. J Cataract Refract Surg 1998;24:689 –92. 14. Giers U. Phako-Chop verringert Ultraschallenergie auf 60% des Ausgangswertes. Ophthalmo-Chirurgie 1998;10:197–203. 15. Kohlhaas M, Stahlhut O, Tholuck J, Richard G. Entwicklung der Hornhautdicke und Endothelzelldichte nach Kataraktextraktion mittels Phakoemulsifikation. Ophthalmologe 1997; 94:515– 8. 16. Klebe S, Walkow T, Ander W, Hartmann C. Postoperativer Endothelzellenverlust nach Phakoemulsifikation in Abha¨ngigkeit von der Lokalisation des koreoskleralen 7-mmTunnelschnittes. In: Ohrloff C, et al, eds. Kongreß der deutschsprachigen Gesellschaft fu¨r Intraokularlinsenimplantation und refraktive Chirurgie, Vol. 11. Berlin: Springer, 1998:201– 6. 17. Brazitikos P, D’Amico DJ, Bochow TW, et al. Experimental ocular surgery with a high-repetition-rate erbium:YAG laser. Invest Ophthalmol Vis Sci 1998;39:1667–75. 18. Bissen-Miyajima H, Shimmura S, Tsubota K. Thermal effect on corneal incisions with different phacoemulsification ultrasonic tips. J Cataract Refract Surg 1999;25:60 – 4. 19. Jaffe NS, Jaffe MS, Jaffe GF. Cataract Surgery and Its Complications, 5th ed. St. Louis: Mosby, 1999. 20. Barak A, Desatnik H, Ma-Naim T, et al. Early postoperative
21. 22. 23.
24. 25. 26. 27. 28. 29.
intraocular pressure pattern in glaucomatous and nonglaucomatous patients. J Cataract Refract Surg 1996;22:607–11. Meyer MA, Savitt ML, Kopitas E. The effect of phacoemulsification on aqueous outflow facility. Ophthalmology 1997; 104:1221–7. Cherfan GM, Rich WJ, Wright G. Raised intraocular pressure and other problems with sodium hyaluronate and cataract surgery. Trans Ophthalmol Soc UK 1983;103:277–9. Fischer E, Ho¨h H. Entwicklung von Refraktion, Visus, Augeninnendruck, Hornhautdicke und Endothelzellzahl nach Erbiumlaserphakoemulsifikation. In: Duncker GIW, ed. Kongreß der deutschsprachigen Gesellschaft fu¨r Intraokularlinsenimplantation und refraktive Chirurgie, Vol. 12. Berlin: Springer,1998:362– 8. Jahn CE, Emke M. Wie reproduzierbar und stabil ist die Augendrucksenkung nach extrakapsula¨rer Kataraktextraktion? Klin Monatsbl Augenheilkd 1995;207:348 –52. Kammann J, Dornbach G, Cosmar E. Jahre korneale Kleinschnittchirurgie. Ophthalmologe 1995;92:266 –9. Rich WJ, Radtke ND, Cohan BE. Early ocular hypertension after cataract extraction. Br J Ophthalmol 1974;58:725–31. Sponagel LD, Gloor B. Ist die Implantation einer Hinterkammerlinse ein drucksenkender Eingriff? Klin Monatsbl Augenheilkd 1986;188:495–9. Galin MA, Lin LL-K, Obstbaum SA. Cataract extraction and intraocular pressure. Trans Ophthalmol Soc UK 1978;98: 124 –7. Ho¨h H, Fischer E. Erbiumlaserphakoemulsifikation—Eine klinische Pilotstudie. Klin Monatsbl Augenheilkd 1999;214: 203–10.
Discussion by I. Howard Fine, MD The best way to evaluate new phacoemulsification technology is to compare it with ultrasound, the current standard, with respect to efficacy, safety, cost, and clinical application. With respect to efficacy, we recognize that ultrasound can emulsify all grades of nuclear density, but in the erbium study, 90% of the nuclei were less than or equal to 2⫹, and 75% were 0 or 1⫹. My incision size for ultrasound is 2.5 mm. The erbium incision was 3.2 mm. All systems today are limited by incision sizes necessary for IOL implantation. My emulsification time using ultrasound is somewhere between 1 and 1.5 minutes, but because I use energy modulations, the effective phacoemulsification time (that is, how long it would have taken with continuous phacoemulsification at 100% power) is less than 20 seconds. The erbium laser had a mean ultrasound time of 4.2 minutes for grade 1⫹ nuclear sclerosis, and the longest time was 20 minutes. Four of the erbium laser treated lenses had to be converted to ultrasound emulsification or expressed as in extracapsular cataract extraction. With respect to fluidics, ultrasound phacoemulsification has highly sophisticated fluidics with multiple options, an ability to set parameters for vacuum and flow within wide limits, and an ability to use vacuum and flow as additional instruments to manipulate and extract cataract tissue. There is some potential for the system
From Oregon Health Sciences University, Portland, Oregon. Oregon Eye Associates, Eugene, Oregon. Address correspondence to I. Howard Fine, MD, 1550 Oak Street, Eugene, OR 97401.
to clog. The erbium system is also susceptible to occlusion and has an increased potential to clog and an increased need for flushing of the system. The fluid volume is threefold that of conventional ultrasound emulsification. The energy I place into eyes using ultrasound was calculated for me by engineers at different manufacturing companies. I use energy modulations (either burst mode or 2 pulses per second), where effective phacoemulsification time is 20 seconds or less and average phacoemulsification powers are 15% or less. In one system, I average 10 joules, in another I average 6 joules, and in a third I average 4 joules. Part of the energy with ultrasound, of course, is thermal. The average energy placed into the eye with the erbium system is 38.5 joules, none of which is thermal. The energy placed into the eye with the erbium system was not, as stated, a fraction of that used with ultrasound, because the use of power modulations with ultrasound allows for dramatically reduced energy levels than previously reported in the literature. Although one of the advantages of the erbium system is that there is no possibility for thermal injury, we cannot consider erbium laser phacoemulsification, which uses more total energy and which cannot be performed deeply within the endolenticular space in cases of Fuchs’ dystrophy, to be a more gentle procedure than ultrasound phacoemulsification. With regard to safety issues, in a recent paper published by Corey and Olson,1 we see that residents learning ultrasound phacoemulsification had an overall capsule rupture rate of 1.9% in nearly 400 cases, 63% of which were associated with vitreous loss. The erbium system capsule rupture rate was 7.5%, half of which was associated with vitreous loss. Of course, we have to recognize that residents being trained in ultrasound are being coached by experts
1061
Ophthalmology Volume 107, Number 6, June 2000 in highly sophisticated and well-accepted techniques, whereas the experienced surgeon using these new energy sources are functioning with little experience to guide them with respect to optimal technique. That notwithstanding, 35% of the erbium cases were associated with operative or postoperative complications, including 3 cases (7.5%) of postoperative fibrinoid anterior chamber reactions. Dick et al2 showed 4.2% endothelial cell loss for nuclear densities of 2⫹ or less and an average of 6.7% for all nuclear densities in conventional ultrasound phacoemulsification through clear corneal incisions. In the erbium study, the endothelial cell loss was 0.96%. Because 90% of the cases in this study were graded as 2⫹ or less nuclear sclerosis, it is hard to imagine that these differences are clinically relevant. With respect to cost, the purchase price for ophthalmic lasers currently in use for nonphacoemulsification purposes is approximately the same as for ultrasound phacoemulsification systems. It’s hard to speculate on comparative maintenance costs and the costs of reusables and disposables. With respect to clinical applications, the erbium laser both appears to have a learning curve similar to ultrasound phacoemulsification. Pre- and postoperative care appears to be approximately the same, and the rapidity of visual rehabilitation looks similar to ultrasound phacoemulsification. Perhaps a better way to view these new energy modalities
1062
would be to compare them with the status of ultrasound phacoemulsification in 1976. In 1976, phacoemulsifiers required manual tuning. There was no linear power; power was on/off 100%. We were not able to customize the parameters of vacuum rise time and aspiration flow rate or maximum vacuum; the fluidics were relatively unstable; there was a high complication rate. Ultrasound phacoemulsification was used by approximately 5% of surgeons at that time, mainly for cataracts with low grades of nuclear sclerosis, and was considered a bad and dangerous procedure by the rest of the surgeons. Laser phacoemulsification today is an emerging new technology. It is evolving rapidly and offers discernible patient benefits. We can anticipate major advances, both in technology and technique, and therefore consider the effort to develop these methods for cataract surgery both important and worthwhile. References 1. Corey RP, Olson RJ. Surgical outcomes of cataract extractions performed by residents using phacoemulsification. J Cataract Refract Surg 1998;24:66 –72. 2. Dick HB, Kohnen T, Jacobi FK, Jacobi KW. Long-term endothelial cell loss following phacoemulsification through a temporal clear corneal incision. J Cataract Refract Surg 1996;22: 63–71.
21. 22. 23.
24. 25. 26. 27. 28. 29.
intraocular pressure pattern in glaucomatous and nonglaucomatous patients. J Cataract Refract Surg 1996;22:607–11. Meyer MA, Savitt ML, Kopitas E. The effect of phacoemulsification on aqueous outflow facility. Ophthalmology 1997; 104:1221–7. Cherfan GM, Rich WJ, Wright G. Raised intraocular pressure and other problems with sodium hyaluronate and cataract surgery. Trans Ophthalmol Soc UK 1983;103:277–9. Fischer E, Ho¨h H. Entwicklung von Refraktion, Visus, Augeninnendruck, Hornhautdicke und Endothelzellzahl nach Erbiumlaserphakoemulsifikation. In: Duncker GIW, ed. Kongreß der deutschsprachigen Gesellschaft fu¨r Intraokularlinsenimplantation und refraktive Chirurgie, Vol. 12. Berlin: Springer,1998:362– 8. Jahn CE, Emke M. Wie reproduzierbar und stabil ist die Augendrucksenkung nach extrakapsula¨rer Kataraktextraktion? Klin Monatsbl Augenheilkd 1995;207:348 –52. Kammann J, Dornbach G, Cosmar E. Jahre korneale Kleinschnittchirurgie. Ophthalmologe 1995;92:266 –9. Rich WJ, Radtke ND, Cohan BE. Early ocular hypertension after cataract extraction. Br J Ophthalmol 1974;58:725–31. Sponagel LD, Gloor B. Ist die Implantation einer Hinterkammerlinse ein drucksenkender Eingriff? Klin Monatsbl Augenheilkd 1986;188:495–9. Galin MA, Lin LL-K, Obstbaum SA. Cataract extraction and intraocular pressure. Trans Ophthalmol Soc UK 1978;98: 124 –7. Ho¨h H, Fischer E. Erbiumlaserphakoemulsifikation—Eine klinische Pilotstudie. Klin Monatsbl Augenheilkd 1999;214: 203–10.
Discussion by I. Howard Fine, MD The best way to evaluate new phacoemulsification technology is to compare it with ultrasound, the current standard, with respect to efficacy, safety, cost, and clinical application. With respect to efficacy, we recognize that ultrasound can emulsify all grades of nuclear density, but in the erbium study, 90% of the nuclei were less than or equal to 2⫹, and 75% were 0 or 1⫹. My incision size for ultrasound is 2.5 mm. The erbium incision was 3.2 mm. All systems today are limited by incision sizes necessary for IOL implantation. My emulsification time using ultrasound is somewhere between 1 and 1.5 minutes, but because I use energy modulations, the effective phacoemulsification time (that is, how long it would have taken with continuous phacoemulsification at 100% power) is less than 20 seconds. The erbium laser had a mean ultrasound time of 4.2 minutes for grade 1⫹ nuclear sclerosis, and the longest time was 20 minutes. Four of the erbium laser treated lenses had to be converted to ultrasound emulsification or expressed as in extracapsular cataract extraction. With respect to fluidics, ultrasound phacoemulsification has highly sophisticated fluidics with multiple options, an ability to set parameters for vacuum and flow within wide limits, and an ability to use vacuum and flow as additional instruments to manipulate and extract cataract tissue. There is some potential for the system
From Oregon Health Sciences University, Portland, Oregon. Oregon Eye Associates, Eugene, Oregon. Address correspondence to I. Howard Fine, MD, 1550 Oak Street, Eugene, OR 97401.
to clog. The erbium system is also susceptible to occlusion and has an increased potential to clog and an increased need for flushing of the system. The fluid volume is threefold that of conventional ultrasound emulsification. The energy I place into eyes using ultrasound was calculated for me by engineers at different manufacturing companies. I use energy modulations (either burst mode or 2 pulses per second), where effective phacoemulsification time is 20 seconds or less and average phacoemulsification powers are 15% or less. In one system, I average 10 joules, in another I average 6 joules, and in a third I average 4 joules. Part of the energy with ultrasound, of course, is thermal. The average energy placed into the eye with the erbium system is 38.5 joules, none of which is thermal. The energy placed into the eye with the erbium system was not, as stated, a fraction of that used with ultrasound, because the use of power modulations with ultrasound allows for dramatically reduced energy levels than previously reported in the literature. Although one of the advantages of the erbium system is that there is no possibility for thermal injury, we cannot consider erbium laser phacoemulsification, which uses more total energy and which cannot be performed deeply within the endolenticular space in cases of Fuchs’ dystrophy, to be a more gentle procedure than ultrasound phacoemulsification. With regard to safety issues, in a recent paper published by Corey and Olson,1 we see that residents learning ultrasound phacoemulsification had an overall capsule rupture rate of 1.9% in nearly 400 cases, 63% of which were associated with vitreous loss. The erbium system capsule rupture rate was 7.5%, half of which was associated with vitreous loss. Of course, we have to recognize that residents being trained in ultrasound are being coached by experts
1061
Ophthalmology Volume 107, Number 6, June 2000 in highly sophisticated and well-accepted techniques, whereas the experienced surgeon using these new energy sources are functioning with little experience to guide them with respect to optimal technique. That notwithstanding, 35% of the erbium cases were associated with operative or postoperative complications, including 3 cases (7.5%) of postoperative fibrinoid anterior chamber reactions. Dick et al2 showed 4.2% endothelial cell loss for nuclear densities of 2⫹ or less and an average of 6.7% for all nuclear densities in conventional ultrasound phacoemulsification through clear corneal incisions. In the erbium study, the endothelial cell loss was 0.96%. Because 90% of the cases in this study were graded as 2⫹ or less nuclear sclerosis, it is hard to imagine that these differences are clinically relevant. With respect to cost, the purchase price for ophthalmic lasers currently in use for nonphacoemulsification purposes is approximately the same as for ultrasound phacoemulsification systems. It’s hard to speculate on comparative maintenance costs and the costs of reusables and disposables. With respect to clinical applications, the erbium laser both appears to have a learning curve similar to ultrasound phacoemulsification. Pre- and postoperative care appears to be approximately the same, and the rapidity of visual rehabilitation looks similar to ultrasound phacoemulsification. Perhaps a better way to view these new energy modalities
1062
would be to compare them with the status of ultrasound phacoemulsification in 1976. In 1976, phacoemulsifiers required manual tuning. There was no linear power; power was on/off 100%. We were not able to customize the parameters of vacuum rise time and aspiration flow rate or maximum vacuum; the fluidics were relatively unstable; there was a high complication rate. Ultrasound phacoemulsification was used by approximately 5% of surgeons at that time, mainly for cataracts with low grades of nuclear sclerosis, and was considered a bad and dangerous procedure by the rest of the surgeons. Laser phacoemulsification today is an emerging new technology. It is evolving rapidly and offers discernible patient benefits. We can anticipate major advances, both in technology and technique, and therefore consider the effort to develop these methods for cataract surgery both important and worthwhile. References 1. Corey RP, Olson RJ. Surgical outcomes of cataract extractions performed by residents using phacoemulsification. J Cataract Refract Surg 1998;24:66 –72. 2. Dick HB, Kohnen T, Jacobi FK, Jacobi KW. Long-term endothelial cell loss following phacoemulsification through a temporal clear corneal incision. J Cataract Refract Surg 1996;22: 63–71.