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Phacoemulsification after RD Surgery
Ophthalmology
Volume 103, Number 11 , November 1996
of the upper eyelid contour and therefore more predictable results than other techniques I have tried. I accept Dr. Frueh's criticism, but ask that he not overemphasize the importance of the vertical eyelid position and fissure measurements at the expense of an aesthetically pleasing upper eyelid contour. Results in thyroid-related eyelid surgery are highly subjective. If Dr. Frueh can suggest a way to quantify contour results, I and others will be grateful forever. For the moment, I cannot quantify it, but having examined and operated on thousands of eyelids for more than 15 years of practice, can promise "I know a good contour when I see one." JOHN W. SHORE, MD, FACS Boston, Massachusetts
Phacoemulsification after RD Surgery Dear Editor: In the article entitled "Phacoemulsification after Retinal Detachment Surgery" (Ophthalmology 1996; 103:2169), the authors suggest that the retinal redetachment rate after phacoemulsification is low. The authors encountered no redetachments in a series of 47 surgeries. This finding is compatible with an actual redetachment rate of as high as 6%, 1 well within the range reported with standard extracapsular cataract extraction quoted by the authors. This reinforces the authors' statement that the data cannot determine whether phacoemulsification is the preferred technique for these complicated cases. RA VI THOMAS, MD ANDREW BRAGANZA, MD Vellore, India Reference 1. Sackett DL, Haynes RB, Guyatt GH, Tugwell P. Clinical Epidemiology: A Basic Science for Clinical Medicine, 2nd ed. Toronto: Little, Brown and Co, 1991;175-6.
PPA: Automated Lamellar Keratoplasty Dear Editor: I was extremely pleased to read the American Academy of Ophthalmology's Preliminary Procedure Assessment entitled "Automated Lamellar Keratoplasty (Ophthalmology 1996; 103:852-61). I applaud the Academy on not only choosing to perform a preliminary assessment of procedures, but for their choice of their first preliminary assessment. I performed my first keratophakia and keratomileusis procedures in 1980 using the original Steinway instrumentation.1 I subsequently implanted four intracorneal hydrogel lenses in the late 1980s using the Steinway microkeratome to create a lamellar pocket. For all the reasons cited in the Preliminary Procedure Assessment, I abandoned lamellar refractive surgery. In 1993, I restarted lamellar refractive surgery using the Chiron, Inc, automated corneal shaper. Since then, I have performed keratomileusis in situ (automated lamellar keratoplasty [ALK]) for myopia and hyperopia using the Chiron microkeratome, the Eye Technology, Inc, microkeratome (as a paid consultant), and Univer-
1714
salkeratome (as Medical Director for Phoenix Keratek, Inc). I study the clinical and morphologic effects of microkeratome instrumentation through scientific publications in peer-review journals? I, therefore, believe I am qualified to respond to aspects of the preliminary procedure assessment that I believe are flawed. The questions regarding the evaluation of the accuracy of marketing claims are all appropriate. The review of the nascent literature is good, but due to time constraints, some recent articles are not included.3- 7 The assessment suggests that if the marketing claims are correct, one would be able to obtain reproducible results by simply adjusting a nomogram. Conversely, if the microkeratome theory was flawed, unpredictability of postoperative refractive errors and degraded optical performance will be incurred. The microkeratomes, in and of themselves, can produce smooth optical surfaces of relatively predictable diameter and thickness. Blades may be high quality and yet postoperative prediction of refraction andlor loss of best-corrected spectacle visual acuity may occur, not because of the mechanical aspects of the procedure, but because of many of the other variables involved in microkeratome technology and the lamellar refractive procedures. Current techniques that require the cornea to be applanated during the keratotomy produce parallel-faced tissue resection for the myopic power cut; such a tissue shape is not ideal optically and can lead to smaller than anticipated optical zones 2 and irregular astigmatism. Most microkeratomes incise the cornea using an angle of approach of the blade from 9° to 25°, which can produce smaller than anticipated optical zone diameters. The speed of the blade oscillation or rotation and the speed of blade traverse across the cornea have not been studied to determine the effect on predictability of outcome. The intraocular pressure at the time of tissue resection, the hydration of the host's stromal tissue and, of course, surgeon skill will all produce variable results that are not the fault of the microkeratome technology, but basically a result of lamellar surgery. Previous clinical reports of freehand lamellar dissection have documented degradation of visual images. 8 It is possible that the creation of a second optical interface may, in and of itself, degrade visual performance. None of these factors are the fault of the microkeratome technology, but the theoretical basis of the procedures themselves. The use of the laser to create the stromal resection laser in situ keratomileusis (LASIK) is also subject to these same potential risks and complications. The procedure assessments would like to define current minimal measurement criteria to determine refractive outcome. Unfortunately, it is not known what role cap diameter or planned cap thickness has on outcome, irrespective of whether the procedure being performed is keratomileu sis in situ or LASIK. Cap thickness may have no effect on refractive outcome, whereas cap diameter may. Because the parameters of keratomileusis in situ are totally different than those used for LASIK, the Committee on Procedure Assessments should determine which of these two procedures are to be analyzed and which parameters
Volume 103, Number 11 , November 1996
of the upper eyelid contour and therefore more predictable results than other techniques I have tried. I accept Dr. Frueh's criticism, but ask that he not overemphasize the importance of the vertical eyelid position and fissure measurements at the expense of an aesthetically pleasing upper eyelid contour. Results in thyroid-related eyelid surgery are highly subjective. If Dr. Frueh can suggest a way to quantify contour results, I and others will be grateful forever. For the moment, I cannot quantify it, but having examined and operated on thousands of eyelids for more than 15 years of practice, can promise "I know a good contour when I see one." JOHN W. SHORE, MD, FACS Boston, Massachusetts
Phacoemulsification after RD Surgery Dear Editor: In the article entitled "Phacoemulsification after Retinal Detachment Surgery" (Ophthalmology 1996; 103:2169), the authors suggest that the retinal redetachment rate after phacoemulsification is low. The authors encountered no redetachments in a series of 47 surgeries. This finding is compatible with an actual redetachment rate of as high as 6%, 1 well within the range reported with standard extracapsular cataract extraction quoted by the authors. This reinforces the authors' statement that the data cannot determine whether phacoemulsification is the preferred technique for these complicated cases. RA VI THOMAS, MD ANDREW BRAGANZA, MD Vellore, India Reference 1. Sackett DL, Haynes RB, Guyatt GH, Tugwell P. Clinical Epidemiology: A Basic Science for Clinical Medicine, 2nd ed. Toronto: Little, Brown and Co, 1991;175-6.
PPA: Automated Lamellar Keratoplasty Dear Editor: I was extremely pleased to read the American Academy of Ophthalmology's Preliminary Procedure Assessment entitled "Automated Lamellar Keratoplasty (Ophthalmology 1996; 103:852-61). I applaud the Academy on not only choosing to perform a preliminary assessment of procedures, but for their choice of their first preliminary assessment. I performed my first keratophakia and keratomileusis procedures in 1980 using the original Steinway instrumentation.1 I subsequently implanted four intracorneal hydrogel lenses in the late 1980s using the Steinway microkeratome to create a lamellar pocket. For all the reasons cited in the Preliminary Procedure Assessment, I abandoned lamellar refractive surgery. In 1993, I restarted lamellar refractive surgery using the Chiron, Inc, automated corneal shaper. Since then, I have performed keratomileusis in situ (automated lamellar keratoplasty [ALK]) for myopia and hyperopia using the Chiron microkeratome, the Eye Technology, Inc, microkeratome (as a paid consultant), and Univer-
1714
salkeratome (as Medical Director for Phoenix Keratek, Inc). I study the clinical and morphologic effects of microkeratome instrumentation through scientific publications in peer-review journals? I, therefore, believe I am qualified to respond to aspects of the preliminary procedure assessment that I believe are flawed. The questions regarding the evaluation of the accuracy of marketing claims are all appropriate. The review of the nascent literature is good, but due to time constraints, some recent articles are not included.3- 7 The assessment suggests that if the marketing claims are correct, one would be able to obtain reproducible results by simply adjusting a nomogram. Conversely, if the microkeratome theory was flawed, unpredictability of postoperative refractive errors and degraded optical performance will be incurred. The microkeratomes, in and of themselves, can produce smooth optical surfaces of relatively predictable diameter and thickness. Blades may be high quality and yet postoperative prediction of refraction andlor loss of best-corrected spectacle visual acuity may occur, not because of the mechanical aspects of the procedure, but because of many of the other variables involved in microkeratome technology and the lamellar refractive procedures. Current techniques that require the cornea to be applanated during the keratotomy produce parallel-faced tissue resection for the myopic power cut; such a tissue shape is not ideal optically and can lead to smaller than anticipated optical zones 2 and irregular astigmatism. Most microkeratomes incise the cornea using an angle of approach of the blade from 9° to 25°, which can produce smaller than anticipated optical zone diameters. The speed of the blade oscillation or rotation and the speed of blade traverse across the cornea have not been studied to determine the effect on predictability of outcome. The intraocular pressure at the time of tissue resection, the hydration of the host's stromal tissue and, of course, surgeon skill will all produce variable results that are not the fault of the microkeratome technology, but basically a result of lamellar surgery. Previous clinical reports of freehand lamellar dissection have documented degradation of visual images. 8 It is possible that the creation of a second optical interface may, in and of itself, degrade visual performance. None of these factors are the fault of the microkeratome technology, but the theoretical basis of the procedures themselves. The use of the laser to create the stromal resection laser in situ keratomileusis (LASIK) is also subject to these same potential risks and complications. The procedure assessments would like to define current minimal measurement criteria to determine refractive outcome. Unfortunately, it is not known what role cap diameter or planned cap thickness has on outcome, irrespective of whether the procedure being performed is keratomileu sis in situ or LASIK. Cap thickness may have no effect on refractive outcome, whereas cap diameter may. Because the parameters of keratomileusis in situ are totally different than those used for LASIK, the Committee on Procedure Assessments should determine which of these two procedures are to be analyzed and which parameters