Journal of Refractive Surgery

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The Barraquer Lecture: Surgical Management of Myopia-A Clinician's Perspective

Richard L Lindstrom, MD

Abstract

This lecture attempts to help the comprehensive ophthalmologist understand the major surgical approaches to the correction of myopia and the market for those procedures- refractive keratotomy, photorefractive keratectomy (PRK), automated lamellar keratoplasty, and laser in situ keratomileusis (LASIK).

Many ophthalmologists are interested in refractive surgery. In an Ocular Surgery News survey, 62% of a small random sample of U.S. ophthalmologists- 9,000 to 10,000 ophthalmologists- said they intended to perform PRK.1 An audience poll at the 1994 Pre-Academy Meeting of the International Society of Refractive Surgery revealed that 97% intended to perform PRK Refractive surgery will be as big or bigger than cataract surgery is today both to ophthalmology and the industry that supports us.

Is it ethical and appropriate to do refractive surgery? I have debated this in many different settings. Although I believe their numbers are decreasing, there are ophthalmologists who do not think that refractive surgery is ethical or appropriate. For me, the word handicap places the question in perspective. I think it is ethical and appropriate for physicians to help patients overcome handicaps; it is a common function of medicine. From the Prospective Evaluation of Radial Keratotomy (PERK) Study: "The desire to have normal bodily function without dependence on external prosthetic devices is normal."2 I can personalize this. I am 47 years old, 1.50 diopters (D) presbyopic, and this morning I went to a breakfast meeting and forgot my readers. I was handicapped. I could not read the notes, I could not look at the handouts, and if tomorrow I could have one of my talented colleagues correct my presbyopia with a procedure having a similar risk-benefit ratio as mini-radial keratotomy, PRK, or LASIK, I would have the surgery and be willing to pay $2000 for that surgery.

Table

Even at relatively low volumes, refractive surgery can be an important income stream to the ophthalmologist (Table 10). All comprehensive ophthalmologists with any interest at all should consider participating in refractive surgery. Unless you anticipate a volume of 750 to 1000 eyes per year, however, I would discourage you from buying a laser (Table 11). Be wary of limited partnerships, although my own experiences here may be coloring my opinion.

I recall that 10 years ago, I made a living performing penetrating keratoplasty. I performed cataract surgery as a service to my patients, and refractive surgery as a hobby. Ten years later, I make a living performing refractive surgery; I continue to perform cataract surgery as a service to my patients; and I perform penetrating keratoplasty as a hobby. I think many of you may find that same transition over the next 5 years. Refractive surgery is here to stay and will play a major role in the shape of ophthalmology's future.

Dedication

This lecture is dedicated to my family: to my father, who taught me the value of honesty, integrity and hard work; to my mother, who taught me about empathy, compassion and goodwill; to my wife, Jaci, and my children, who taught me the meaning of love.

1. FaxPoll, Ocular Surgery News 1995;13:13.

2. Waring GO, Lynn MJ, McDonnell PJ, and the PERK Study Group. Results of the Prospective Evaluation of Radial Keratotomy (PERK) study 10 years after surgery. Arch Ophthalmol 1994;112:1298-1308.

3. Lindstrom RL. Minimally invasive radial keratotomy: MiniRK. J Cataract Refract Surg 1995;21:27-34.

4. Schachar RA, Black TD, Huang T. A physicist's view of radial keratotomy with practical surgical implications. In: Schachar RA, Levy NS, Schachar L (eds). Kerato-refraction; Proceedings of the Keratorefractive Society Meeting. Denison, Texas; LAL Publishing;1980:195-219.

5. Jester JV, Venet T, Lee JS, Schanzlin DJ, Smith RE. A statistical analysis of…

This lecture attempts to help the comprehensive ophthalmologist understand the major surgical approaches to the correction of myopia and the market for those procedures- refractive keratotomy, photorefractive keratectomy (PRK), automated lamellar keratoplasty, and laser in situ keratomileusis (LASIK).

Many ophthalmologists are interested in refractive surgery. In an Ocular Surgery News survey, 62% of a small random sample of U.S. ophthalmologists- 9,000 to 10,000 ophthalmologists- said they intended to perform PRK.1 An audience poll at the 1994 Pre-Academy Meeting of the International Society of Refractive Surgery revealed that 97% intended to perform PRK Refractive surgery will be as big or bigger than cataract surgery is today both to ophthalmology and the industry that supports us.

Is it ethical and appropriate to do refractive surgery? I have debated this in many different settings. Although I believe their numbers are decreasing, there are ophthalmologists who do not think that refractive surgery is ethical or appropriate. For me, the word handicap places the question in perspective. I think it is ethical and appropriate for physicians to help patients overcome handicaps; it is a common function of medicine. From the Prospective Evaluation of Radial Keratotomy (PERK) Study: "The desire to have normal bodily function without dependence on external prosthetic devices is normal."2 I can personalize this. I am 47 years old, 1.50 diopters (D) presbyopic, and this morning I went to a breakfast meeting and forgot my readers. I was handicapped. I could not read the notes, I could not look at the handouts, and if tomorrow I could have one of my talented colleagues correct my presbyopia with a procedure having a similar risk-benefit ratio as mini-radial keratotomy, PRK, or LASIK, I would have the surgery and be willing to pay $2000 for that surgery.

Table

Table 1Summary of Visual Acuity Outcomes in the Prospective Evaluation of Radial Keratotomy (PERK) Study in 374 Patients at 10 years after Surgery

Table 1

Summary of Visual Acuity Outcomes in the Prospective Evaluation of Radial Keratotomy (PERK) Study in 374 Patients at 10 years after Surgery

REFRACTIVE KERATOTOMY

I have performed radial keratotomy since the early 1980s, and was a participating surgeon in the PERK study.2 The 10-year PERK data show that 53% of patients have at least 20/20 visual acuity and 85% see 20/40 or better. We can therefore tell patients that the PERK study showed that most patients, meaning more than half, get 20/20 visual acuity, 85% are able to drive legally without glasses, and that seven out often are independent of spectacles, even 10 years after surgery (Table 1). If we define visually significant loss of spectacle-corrected visual acuity as being the loss of two lines on the Snellen chart, only 3% lost this level of spectaclecorrected vision. If these results had been presented to the Food and Drug Administration's Ophthalmic Devices Advisory Panel, radial keratotomy probably would have received approval based on 1 to 2-year data for low myopia.

Figure 1 : Slit-lamp photograph of a cornea after automated lamellar keratoplasty (deep lamellar keratotomy) for hyperopia shows anterior protrusion and steepening of the cornea, resembling keratoconus. The procedure is no longer performed.

Figure 1 : Slit-lamp photograph of a cornea after automated lamellar keratoplasty (deep lamellar keratotomy) for hyperopia shows anterior protrusion and steepening of the cornea, resembling keratoconus. The procedure is no longer performed.

Unfortunately, we found a problem: progressive hyperopic shift. When you weaken the cornea, it tends to flatten progressively with time. Those of us who performed radial keratotomy in the 1980s have created a significant number of hyperopes. I have lived through one epidemic in ophthalmologyPseudophakie corneal edema caused by iris-fixated lenses, closed-loop anterior chamber lenses, and the early learning curves of phacoemulsification. We probably are going to see another, and that will be consecutive hyperopia after traditional radial keratotomy. If we performed about a million radial keratotomies from 1980 to 1995, we may potentially have at least 200,000 consecutive hyperopes to treat. The average radial keratotomy patient was 35 to 40 years old; now they are 45 to 50, presbyopic, potentially hyperopic, and unhappy.

I have had the opportunity in the last 2 years to treat some of these patients with another operation-automated lamellar keratoplasty for hyperopia (deep lamellar keratoplasty). I would encourage you not to utilize this approach, as two of my ten consecutive hyperopes after radial keratotomy developed a severe ectasia- in a sense, an iatrogenic keratoconus- following automated lamellar keratoplasty for hyperopia (Fig 1). Consider using instead either the Grene or the Lindstrom modification of the Grene lasso compression suture (Fig 2) until and unless another retractive procedure for hyperopia is developed to the point where it can be used safely.

I was ready to abandon radial keratotomy after I went from eight to four incisions and still saw a hyperopic shift in my patients. In 1992, 1 developed mini -radial keratotomy.3 The concept was to maximize corneal flattening with the minimum number and length of incisions in order to stay below the range where the cornea destabilizes. Schachar and others did work in this area.4"6 I described the concept of the "zone of maximum benefit," a 2-mm zone between the 3-mm (my smallest preferred clear zone) and 7-mm clear zones (Fig 3).

Figure 2: A) The Lindstrom modification of the Grene lasso suture currently may be the preferred method of treating radial keratotomy patients who have drifted into hyperopia. B) Cornea 3 months after a Lindstrom-Grene compression suture for consecutive hyperopia after radial keratotomy. Before suturing, the refraction was +2.50 +0,75 x 94° and 3 months after suturing, the refraction was -0.50 +0.75x91°.

Figure 2: A) The Lindstrom modification of the Grene lasso suture currently may be the preferred method of treating radial keratotomy patients who have drifted into hyperopia. B) Cornea 3 months after a Lindstrom-Grene compression suture for consecutive hyperopia after radial keratotomy. Before suturing, the refraction was +2.50 +0,75 x 94° and 3 months after suturing, the refraction was -0.50 +0.75x91°.

McDonnell, who evaluated the burst strength of eyes in the laboratory, showed that even with an eight-incision mini-radial keratotomy, there is no weakening of the globe.7 When I perform miniradial keratotomy now, I can tell patients that I do not weaken their eye and it is no more susceptible to trauma than a normal eye.

Figure 3: Mini-radial keratotomy incisions are restricted to the "zone of maximum benefit" between the 3-mm and 7-mm clear zones.Figure 4: The hyperopic shift of mini-radial keratotomy patients at 3 years was a mean of 0.04 D compared to about 0.50 D in the PERK2 and Werblin8 studies.

Figure 3: Mini-radial keratotomy incisions are restricted to the "zone of maximum benefit" between the 3-mm and 7-mm clear zones.

Figure 4: The hyperopic shift of mini-radial keratotomy patients at 3 years was a mean of 0.04 D compared to about 0.50 D in the PERK2 and Werblin8 studies.

In addition, we are beginning to develop evidence that mini-radial keratotomy may not be as susceptible to hyperopic shift. I now have 3-year data on 72 eyes. Figure 4 demonstrates the relative stability of mini-radial keratotomy when compared to the hyperopic shift reported in the PERK2 and Werblin8 studies. I feel secure that mini-radial keratotomy does not excessively weaken the eye and that we may be able to continue to use mini-radial keratotomy in patients with low to moderate myopia.

In my series of 100 mini-radial keratotomy patients, operated on for -1.00 to -6.00 D of myopia, 64% achieved 20/20 visual acuity, 94% achieved 20/25 to 20/30 visual acuity, and 100% see 20/40 or better. None lost two or more lines of spectaclecorrected visual acuity at 1 year.

Table

Table 2Percent of Eyes Achieving Three Levels of Visual Acuity after Photorefractive Keratectomy

Table 2

Percent of Eyes Achieving Three Levels of Visual Acuity after Photorefractive Keratectomy

Mini-radial keratotomy, in my opinion, will remain useful for low myopia even in a PRK era. It may also find application as an enhancement operation after PRK, automated lamellar keratoplasty, LASIK, refractive cataract surgery, and penetrating keratoplasty. I believe future "PRK surgeons'* may be glad to perform mini-radial keratotomy for the patient who has waited 1 year to see well but has -1.00 to -3.00 D of residual myopia. A one- or two-cut RK can be done, and 5 minutes later the patient is smiling and happy. My usual radial keratotomy procedure involves only one to four radial incisions. When utilizing one or two-incision radial keratotomy, the incisions are oriented in the steeper meridian.

PHOTOREFRACTIVE KERATECTOMY

I am also an advocate of PRK, and became involved with PRK quite early. My colleagues and I at the Phillips Eye Institute have worked with four different lasers and have performed approximately 1200 PRKs.

In patients with low to moderate myopia (-1.00 to -6.00 D), the Summit excimer laser, now approved by the FDA for PRK, results in about 60% of patients having 20/20 visual acuity, 75% having 20/25 or better, and 90% having 20/40 or better (Table 2). If these data look similar to radial keratotomy data, it is because they are. Many surgeons, however, do not feel comfortable with radial keratotomy; these surgeons should know that they can duplicate radial keratotomy results with PRK and expect less intersurgeon variability.

Figure 5 depicts cumulative data from six surgeons at the Phillips Eye Institute using the VisXTaunton laser: 85% of patients saw 20/25 or better, and 99% saw 20/40 or better at 1 year. Preoperative refractions ranged from -1.00 to -8.00 D. Even after 15 years of radial keratotomy experience, I cannot duplicate with radial keratotomy the results I achieved in this series using PRK on patients with -4.00 to -8.00 D of preoperative myopia. I plan to make PRK my preferred procedure for patients with this amount of myopia.

Figure 5: Cumulative PRK data (Taunton 2015 excimer laser) from six surgeons at the Phillips Eye Institute for patients with preoperative myopia between -2.00 and -8,00 D. Ninety-nine percent of eyes at 1 year obtained 20/40 visual acuity or better (200 eyes at 6 months, 89 eyes at 12 months).

Figure 5: Cumulative PRK data (Taunton 2015 excimer laser) from six surgeons at the Phillips Eye Institute for patients with preoperative myopia between -2.00 and -8,00 D. Ninety-nine percent of eyes at 1 year obtained 20/40 visual acuity or better (200 eyes at 6 months, 89 eyes at 12 months).

Although we should avoid "bashing" radial keratotomy or PRK, the comprehensive ophthalmologist must remember that PRK is not without complications (Table 3). The PRK surgeon should be prepared to understand, prevent, and manage these concerns.

One of these problems is subepithelial haze, which can persist for up to a year or longer. In our series, haze was a factor for about one in 100 patients with preoperative myopia of -1.00 to -6.00 D. Fortunately, haze can be retreated. Persistent haze after retreatment occurs in about one in 100 cases. We tell patients that about one in 10,000 after two treatments will face significant loss of vision from haze.

Patients do not like the fact that it may take them 3 to 6 months to see well. This is something to which the surgeon must also adapt. Photorefractive keratectomy is more like penetrating keratoplasty than radial keratotomy in this regard. Both the patient and surgeon must be patient and wait for vision to improve after PRK. As newer lasers create more physiological corneal contours, the recovery of visual function will be faster.

We have not been successful, at least in prospective studies, at treating higher levels of myopia with PRK. Do not be tempted to perform two -7.00 D treatments with the Summit laser in order to correct a -14.00 D myope. In our series, 12% of patients with preoperative myopia of -8.00 D or greater lost two or more lines of spectacle-corrected visual acuity. Lin, using a modern multipass, multizone technique, reported that 15% of patients with -10.00 D or more of preoperative myopia lost two lines or more of spectacle-corrected visual acuity. Do not try to push PRK beyond the current approval level.

Table

Table 3Summary of Complications in Ten Prospective Studies of Excimer Laser PRK

Table 3

Summary of Complications in Ten Prospective Studies of Excimer Laser PRK

THE HIGH MYOPES- USIK AND ALK

What can we do for patients handicapped by high myopia? We are beginning to get some data. Following automated lamellar keratoplasty procedures for preoperative myopia between -6.00 and -30.00 D, between 50 and 87% of patients will see 20/40 or better if enhancements are included (Table 4). Automated lamellar keratoplasty appears to perform better than PRK in high myopes; however, patients should be told that LASIK may be superior to automated lamellar keratoplasty. There is a significant incidence of loss of spectacle-corrected acuity with automated lamellar keratoplasty. Personally, I am unhappy about that loss and as of 1996, I no longer perform automated lamellar keratoplasty but prefer to do LASIK. In my opinion, the most important contribution of automated lamellar keratoplasty has been to popularize lamellar refractive surgery.

LASIK will likely dominate the future of lamellar refractive surgery. LASIK is very patient-friendly in that it offers rapid visual recovery with little pain. It is, unfortunately, surgeon-unfriendly, because it requires two expensive technologies, expensive disposables, and significant surgical skill. Nonetheless, patients are going to drive the procedure, in my opinion. Just as they drove the transition from planned extracapsular to phacoemulsification cataract extraction, they will drive refractive surgeons from PRK to LASIK - and the data support that movement.

Table

Table 4Results of Three Techniques of Refractive Surgery for High Myopia (-6.00 to -30.00 D)Table 5Six-month Results for 12-center Prospective Clinical Trial (N=202) of LASIK for Myopia of -1.00 to -10.00 DTable 6Six-month Results for 12-center Prospective Clinical Trial (N=21) of LASiK for Myopia of -10.00 to -30.00 D

Table 4

Results of Three Techniques of Refractive Surgery for High Myopia (-6.00 to -30.00 D)

Table 5

Six-month Results for 12-center Prospective Clinical Trial (N=202) of LASIK for Myopia of -1.00 to -10.00 D

Table 6

Six-month Results for 12-center Prospective Clinical Trial (N=21) of LASiK for Myopia of -10.00 to -30.00 D

In a series of myopes with -1.00 D to -10.00 D, operated on at 12 centers, LASIK resulted in 68% of patients with 20/20 visual acuity, 84% with 20/25 visual acuity, and 93% with 20/40 visual acuity (Table 5), with a very small incidence of loss of spectacle-corrected visual acuity- better than I obtain with PRK Particularly pleasing to me is the less than 5% incidence of loss of spectacle-corrected visual acuity in the extreme myope (Table 6).

MATCHING THE PROCEDURE WITH THE PATIENT

If we break down the data according to the amount of preoperative myopia, for -1.00 to -3.75 D of myopia, mini-radial keratotomy, PRK, and LASIK are comparable (Table 7). Each of these procedures can appropriately be used for low myopia. I do not think that ophthalmology can afford loud public squabbling over which procedure is better. I believe it should be appropriate in Minneapolis-St. Paul, or anywhere else, to do radial keratotomy, PRK, or LASIK in a low myope if that is what the surgeon and patient decide after proper informed consent. The data justify doing any of the three.

In a -4.00 to -6.00 D myope who is approximately 30 years old, PRK and LASIK appear better based on the data (Table 7). I no longer offer younger patients with more than -4.00 D of myopia the option of radial keratotomy, except in unusual situations. I think PRK or LASIK is the preferred approach for moderate myopia.

High myopia, -6.00 to -10.00 D, is the frontier. Laser in situ keratomileusis (LASIK) and PRK are clearly the competition (Table 7). I do not believe radial keratotomy should be performed for high myopia, except for an 80-year-old patient, and that is rare. Automated lamellar keratoplasty cannot compare to LASIK in regard to accuracy or safety for these patients.

Table

Table 7Comparison of Results: Mini-radial Keratotomy (Mini-RK), PRK, LASIK, and Automated Lamellar Keratoplasty (ALK) for Low, Moderate, High, and Extreme Myopia (% of Eyes)

Table 7

Comparison of Results: Mini-radial Keratotomy (Mini-RK), PRK, LASIK, and Automated Lamellar Keratoplasty (ALK) for Low, Moderate, High, and Extreme Myopia (% of Eyes)

Table

Table 8Refractive Error Distribution for Clinically Significant Myopia in U.S.Table 9Market Projections for Laser Refractive Surgery

Table 8

Refractive Error Distribution for Clinically Significant Myopia in U.S.

Table 9

Market Projections for Laser Refractive Surgery

In the extreme myope, interestingly enough, automated lamellar keratoplasty looks competitive to LASIK (Table 7). Perhaps we need to learn more about the algorithms we should use in LASIK. It is logical to me that LASIK will turn out to be better, even for extreme myopes.

DEMOGRAPHICS AND THE MARKET

How many myopes are candidates for refractive surgery? Nearly half of all myopes are within 1.00 D of emmetropia and therefore are not candidates for surgery. About 10% of the U.S. population- 26 million people- are myopes between -1.00 and -4.00 D. Only about 2%, or 5.2 million people, have myopia between -4.00 and -6.00 D. High and extreme myopia are relatively rare- another 2% combined (Table 8).

How big will the market be? The easiest way to analyze it is by the number of patient eyes per thousand population. The average comprehensive ophthalmologist takes care of about 20,000 people. I estimate that in 1996 we will do about two eyes per 1000, which means that the average comprehensive ophthalmologist should do about 40 eyes. This will grow to compare with cataract surgery- six eyes per 1000 by the year 2000, only 5 years away (Table 9). The dollar amount spent on refractive surgery is estimated at $1.2 billion in 1996, growing to over $2.4 billion by the year 2000 (personal communication).

Table

Table 10Individual Surgeon Practice Revenue Projections (1995 to 2000) for Refractive SurgeryTable 11Cost Effectiveness of Laser Purchase for Individual Surgeons - 1996

Table 10

Individual Surgeon Practice Revenue Projections (1995 to 2000) for Refractive Surgery

Table 11

Cost Effectiveness of Laser Purchase for Individual Surgeons - 1996

Even at relatively low volumes, refractive surgery can be an important income stream to the ophthalmologist (Table 10). All comprehensive ophthalmologists with any interest at all should consider participating in refractive surgery. Unless you anticipate a volume of 750 to 1000 eyes per year, however, I would discourage you from buying a laser (Table 11). Be wary of limited partnerships, although my own experiences here may be coloring my opinion.

I recall that 10 years ago, I made a living performing penetrating keratoplasty. I performed cataract surgery as a service to my patients, and refractive surgery as a hobby. Ten years later, I make a living performing refractive surgery; I continue to perform cataract surgery as a service to my patients; and I perform penetrating keratoplasty as a hobby. I think many of you may find that same transition over the next 5 years. Refractive surgery is here to stay and will play a major role in the shape of ophthalmology's future.

Dedication

This lecture is dedicated to my family: to my father, who taught me the value of honesty, integrity and hard work; to my mother, who taught me about empathy, compassion and goodwill; to my wife, Jaci, and my children, who taught me the meaning of love.

REFERENCES

1. FaxPoll, Ocular Surgery News 1995;13:13.

2. Waring GO, Lynn MJ, McDonnell PJ, and the PERK Study Group. Results of the Prospective Evaluation of Radial Keratotomy (PERK) study 10 years after surgery. Arch Ophthalmol 1994;112:1298-1308.

3. Lindstrom RL. Minimally invasive radial keratotomy: MiniRK. J Cataract Refract Surg 1995;21:27-34.

4. Schachar RA, Black TD, Huang T. A physicist's view of radial keratotomy with practical surgical implications. In: Schachar RA, Levy NS, Schachar L (eds). Kerato-refraction; Proceedings of the Keratorefractive Society Meeting. Denison, Texas; LAL Publishing;1980:195-219.

5. Jester JV, Venet T, Lee JS, Schanzlin DJ, Smith RE. A statistical analysis of radial keratotomy in human cadaver eyes. Am J Ophthalmol 1981;92:172-177.

6. Salz JJ, Lee JS, Jester JV1 Steel D, Villasenor RA, Nesburn AB, Smith RE. Radial keratotomy in fresh human cadaver eyes. Ophthalmology 1981;88:742-746.

7. Pinheiro MN Jr, Bryant MR, Tayyanipour R, Nassaralla BA, Wee WR, McDonnell PJ. Corneal integrity after refractive surgery: effects of radial keratotomy and mini-radial keratotomy. Ophthalmology 1995;102:297-301.

8. Werblin TP, Stafford GM. The Casebeer system for predictable keratorefractive surgery: one-year evaluation of 205 consecutive eyes. Ophthalmology 1993;100:1095-1102.

Table 1

Summary of Visual Acuity Outcomes in the Prospective Evaluation of Radial Keratotomy (PERK) Study in 374 Patients at 10 years after Surgery

Table 2

Percent of Eyes Achieving Three Levels of Visual Acuity after Photorefractive Keratectomy

Table 3

Summary of Complications in Ten Prospective Studies of Excimer Laser PRK

Table 4

Results of Three Techniques of Refractive Surgery for High Myopia (-6.00 to -30.00 D)

Table 5

Six-month Results for 12-center Prospective Clinical Trial (N=202) of LASIK for Myopia of -1.00 to -10.00 D

Table 6

Six-month Results for 12-center Prospective Clinical Trial (N=21) of LASiK for Myopia of -10.00 to -30.00 D

Table 7

Comparison of Results: Mini-radial Keratotomy (Mini-RK), PRK, LASIK, and Automated Lamellar Keratoplasty (ALK) for Low, Moderate, High, and Extreme Myopia (% of Eyes)

Table 8

Refractive Error Distribution for Clinically Significant Myopia in U.S.

Table 9

Market Projections for Laser Refractive Surgery

Table 10

Individual Surgeon Practice Revenue Projections (1995 to 2000) for Refractive Surgery

Table 11

Cost Effectiveness of Laser Purchase for Individual Surgeons - 1996

10.3928/1081-597X-19970501-15

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