Exposing the LASIK Scam

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PostPosted: Sat Dec 30, 2006 2:16 pm 
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Original Articles:

Probability Model of the Inaccuracy of Residual Stromal Thickness Prediction to Reduce the Risk of Ectasia After LASIK Part II: Quantifying Population Risk

Journal of Refractive Surgery Vol. 22 No. 9 November 2006

Dan Z. Reinstein, MD, MA(Cantab), FRCSC; Sabong Srivannaboon, MD; Timothy J. Archer, BA(Oxon), DipCompSci(Cantab); Ronald H. Silverman, PhD; Hugo Sutton, MD; D. Jackson Coleman, MD

Quote:
The standard deviation of flap thickness can be up to (or even above) 30 μm for some commercially available microkeratomes.19-22 With a fl ap thickness standard deviation of 30 μm, an RST error of 90 μm is likely to occur in 0.5% of eyes (99% of values lie within 3 standard deviations for a Normal distribution). Spadea et al23 reported a case of ectasia where a Moria manually guided MDSC microkeratome (Moria, Antony, France) with a predicted fl ap thickness of 120 μm was used. The fl ap was measured histologically as 260 μm; an error of 140 μm. Figure 1 shows an Artemis VHF digital ultrasound B-scan (Ultralink LLC, St Petersburg, Fla) of a LASIK fl ap created with a Hansatome 160 microkeratome (Bausch & Lomb, Rochester, NY). The predicted fl ap thickness was 160 μm and the fl ap was measured to be 323-μm-thick centrally; an error of 163 μm.


Quote:
The model predicted that the safe minimum target RST was 329 μm for the rate of ectasia to be reduced to 1:1,000,000.

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PostPosted: Sun Jan 21, 2007 12:24 am 
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LASIK Flap Characteristics Using the Moria M2 Microkeratome With the 90-?m Single Use Head

Journal of Refractive Surgery Vol. 23 No. 1 January 2007

Quote:
However, intraoperative pachymetry should be done routinely, considering high range of flap thickness of as much as 95 μm, not only to prevent ectasia after LASIK but also for possible enhancement reoperation.

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PostPosted: Sat Feb 24, 2007 2:25 am 
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Kaohsiung J Med Sci. 2007 Jan;23(1):25-9.

Corneal flap thickness during laser in situ keratomileusis.

Hsu SY.

Department of Ophthalmology, Buddhist Tzu Chi General Hospital and Tzu Chi University, Hualien, Taiwan. wps59@yahoo.com.tw

To analyze the actual corneal flap thickness (FT) after flap making by MK-2000 microkeratome during laser in situ keratomileusis (LASIK), 42 females and 20 males with myopia or myopic astigmatism were enrolled in this study. FTs were created using a microkeratome with a 130 microm head. Corneal thickness was measured by ultrasonic pachymeter. The correlations between FT and central corneal thickness (CCT), keratometric power and age were analyzed. The mean age at operation for all study subjects was 27.6+/-4.9 years. The average FT was 133.2+/-15.4 microm. The average CCT was 540.+/-30.3 microm. The average keratometric power was 43.66+/-1.32 D. There was a positive correlation between FT and CCT and no correlation between FT and keratometric power or between FT and age. We recommend that LASIK surgeons inspect the actual FT when using microkeratome.

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PostPosted: Sun Apr 29, 2007 2:16 am 
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Long-term results of laser in situ keratomileusis for high myopia: Risk for ectasia

Patrick I. Condon, MCh, FRCS, FRCOphth, Michael O?Keefe, MCh, FRCS, FRCOphth, Perry S. Binder, MD

J Cataract Refract Surg
Vol 33, Apr 2007


Quote:
There are several circumstances in which excessive corneal tissue may be removed during LASIK surgery. The first is having a flap with a thickness greater than planned, leaving the laser ablation deeper in the
stroma. Variability of flap thickness creation is well known; thus, one may have planned to create a 160 mmflap and actually create a 220 mm flap.

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PostPosted: Thu May 17, 2007 2:07 am 
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Non-peer reviewed:

Quote:
?There were a lot of things that suggested that PRK would ultimately be better because of reduced biomechanics and other variables caused by the creation of the flap,? recalls Dr. Krueger. ?We now know that this was mostly due to the variability in flap thickness that we see with mechanical microkeratomes.?


EyeWorld
April 2007

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PostPosted: Wed Aug 29, 2007 12:28 pm 
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JCRS
Analysis of ectasia after laser in situ keratomileusis: Risk factors
Volume 33, Issue 9, Pages 1530-1538 (September 2007)
Perry S. Binder

Quote:
The mean flap thickness measured at surgery by subtraction pachymetry (n = 350 eyes) was 113.1 ? 29.3 μm (range 29 to 221 μm).


Quote:
The RST measured directly after the laser ablation, recorded in 250 eyes, ranged from 102 to 384 μm.


If the eyes in that study had achieved flap thicknesses in excess of 200 μm, which is not uncommon with the microkeratomes used at that time, the residual thicknesses would have been less than 250 μm in all cases.

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PostPosted: Thu Feb 14, 2008 3:05 pm 
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Detection of an Abnormally Thick LASIK Flap With Anterior Segment OCT Imaging Prior to Planned LASIK Retreatment Surgery

Journal of Refractive Surgery Vol. 24 No. 2 February 2008
Luis Izquierdo, Jr, MD; Maria A. Henriquez, MD; Peter A. Zakrzewski, MD

PURPOSE
To report a case of an abnormally thick flap that was detected with the use of anterior segment optical coherence tomography (OCT) prior to planned LASIK retreatment surgery.

METHODS
A 43-year-old man presented 6 years after bilateral LASIK surgery with uncorrected visual acuity (UCVA) of 20/20 in the right eye and 20/100 in the left eye, and best spectacle-corrected visual acuity (BSCVA) of 20/20 in the right eye and 20/20 in the left eye (refraction -2.25 -1.25 x 131). Anterior segment OCT was performed before LASIK retreatment surgery in the left eye.

RESULTS
The flap was found to be 394 ?m and the residual stromal bed was too thin (152 ?m) to allow for safe LASIK retreatment surgery. After waiting 4 months to ensure refractive stability, photorefractive keratectomy was performed. Postoperative UCVA was 20/20 plano.

CONCLUSIONS
The use of anterior segment OCT in the preoperative examination for planned LASIK retreatment surgery provided more reliable data. [J Refract Surg. 2008;24:197-199.]

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PostPosted: Wed May 21, 2008 3:44 pm 
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Ophthalmic Surg Lasers Imaging. 2008 Mar-Apr;39(2):107-13.
Errors of residual stromal thickness estimation in LASIK. Cheng HC, Chen YT, Yeh SI, Yau CW.
Department of Ophthalmology, Mackay Memorial Hospital, Taipei, Taiwan.

BACKGROUND AND OBJECTIVE: To investigate inaccuracy and variability in residual stromal thickness estimation in LASIK by pachymetry and measurements of corneal thickness, flap thickness, and ablation depth.

PATIENTS AND METHODS: In 73 eyes of 37 patients, preoperative and postoperative corneal thicknesses were obtained with slit-scanning elevation topography and the ultrasound pachymeter. LASIK was performed and corneal flaps were created with a microkeratome. Flap thickness and ablation depth (expected and achieved) were calculated. Residual stromal thickness estimation error was analyzed.

RESULTS: The mean preoperative corneal thicknesses were 559.58 +/- 23.47 and 554.92 +/- 29.95 microm for the ultrasound pachymeter and slit-scanning elevation topography, respectively. Measurement differences ranged from -36 to 30 microm. With the pachymeter, calculated mean flap thickness was 139.58 +/- 17.59 microm. With this device, predicted ablation depth differed from achieved depth by 20% or more in approximately one-third (30.14%) of treated patients; ablation differences ranged from 10.0% to 19.99% in 37% of patients and 1.00% to 9.99% in 31.5% of patients.

CONCLUSION: Imprecision of microkeratome cuts, preoperative corneal pachymetry, and laser ablation depth have a significant impact on the inaccuracy of residual stromal thickness prediction. Especially in patients with borderline corneal thickness, intraoperative pachymetry measurements and a residual stromal thickness higher than the safety margin of 250 microm are recommended to minimize iatrogenic ectasia.

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