Exposing the LASIK Scam

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 Post subject: IOL calculations are inaccurate after LASIK
PostPosted: Thu Dec 08, 2005 1:30 am 
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Everyone who lives long enough will develop cataracts, including LASIK patients.

LASIK patients are not being informed that the method used to calculate the power of the IOL for cataract surgery is inaccurate after LASIK.

LASIK patients who have subsequent cataract surgery are in for a "refractive surprise".

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http://www.ncbi.nlm.nih.gov/entrez/quer ... query_hl=1


Klin Monatsbl Augenheilkd. 2005 May;222(5):419-23.

[Comparative results of keratometry with three different keratometers after LASIK]

[Article in German]

Schafer S, Kurzinger G, Spraul CW, Kampmeier J.

Augenklinik, Universitatsklinikum Ulm. sabine.schaefer@medizin.uni-ulm.de

BACKGROUND: Postoperative hyperopia is a frequent result of cataract surgery in eyes after previous myopic kerato-refractive surgery. One reason for the underestimation of intraocular lens (IOL) power is the wrong corneal refractive power measurement obtained by keratometers and corneal topography systems after LASIK. The aim of this study was to compare the precision of measurements of three different keratometers after LASIK.

METHOD: We studied 58 eyes of 34 refractive patients aged between 20 and 51 years. The preoperative measurements and the measurements one month after LASIK were performed with the Keratometer (Zeiss), the corneal topograph (EyeSys Technologies) and the IOL-Master (Zeiss). We compared our postoperative measurement results obtained with the three keratometers with the results obtained by using the clinical history method (chm).

RESULTS: The smallest mean deviation was achieved with the IOL-Master (measured mean +/- SD: 38.94 +/- 1.88 D, vs. chm: 38.35 +/- 2.13 D). The Keratometer (Zeiss) showed a larger deviation (measured: 39.12 +/- 1.76 D, chm 38.34 +/- 2.07 D) and the largest deviation was shown with the corneal topograph (measured: 39.84 +/- 1.85 D, chm: 38.86 +/- 2.10 D), which measured in mean one diopter higher than what was obtained utilizing the chm. A positive correlation between corrected myopia and the postoperative difference between the measured and calculated value for each keratometer was found.

CONCLUSION: This study demonstrates that with common keratometers central corneal power is measured too high after LASIK. For IOL calculation in patients after LASIK, the wrongly positive deviation from measured central corneal power has to be taken into account.


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PostPosted: Mon Apr 10, 2006 11:25 am 
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Cont Lens Anterior Eye. 2006 Apr 4;

The AS biometry technique-A novel technique to aid accurate intraocular lens power calculation after corneal laser refractive surgery.

Sambare C, Naroo S, Shah S, Sharma A.

The Ophthalmic Department, Kempston Road, Bedford Hospital, Bedford MK42 9DJ, UK.

Intraocular lens power (IOL) calculation for cataract surgery has been shown to be inaccurate after photorefractive keratectomy (PRK), laser-assisted subepithelial keratectomy (LASEK) and laser in situ keratomileusis (LASIK). Many techniques exist to calculate corneal power with varying results and require the clinician to be aware of the pitfalls of IOL power calculation in post-refractive eyes. The AS biometry method proposed here is a simple method which does not rely on the calculation of corneal power. This new method is compared to the current gold standard the clinical history method (CHM). Twenty-nine eyes of 15 patients had routine biometry prior to LASIK, LASEK or PRK. The range of pre-operative spherical equivalent refractive error was -5.37 to +4.00diopters. The post-operative refraction was measured at 3-6 months. The IOL power calculation was calculated using the AS biometry method and the CHM. The two methods were compared using the Student's paired t-test and the Bland Altman technique. There was no statistical difference between the AS biometry method and the CHM. The paired Student's t-test comparing the AS biometry method and the CHM showed no statistical difference, t=0.33 with a p-value of 0.75, at a 95% confidence interval. The authors conclude that the AS biometry technique is as accurate as the CHM. The former is a simpler method which avoids many of the pitfalls and confounding factors involved in IOL power calculation following corneal excimer laser surgery. However, like the CHM it requires measurements prior to laser surgery.

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Broken Eyes

"The price good men pay for indifference to public affairs is to be ruled by evil men." Plato


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PostPosted: Sat May 06, 2006 4:37 pm 
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J Cataract Refract Surg. 2006 Mar;32(3):425-9.


Accurate intraocular lens power calculation after myopic laser in situ keratomileusis, bypassing corneal power.

Walter KA, Gagnon MR, Hoopes PC Jr, Dickinson PJ.

Department of Ophthalmology, Wake Forest University Eye Center, Wake Forest University School of Medicine, Winston Salem, North Carolina 27157-1033, USA. kwalter@wfubmc.edu

PURPOSE: To describe a novel method for calculating intraocular lens (IOL) power after myopic laser in situ keratomileusis (LASIK) without using the inaccuracies of the post-LASIK corneal power.

SETTING: Department of Ophthalmology, Wake Forest University Eye Center, Wake Forest University School of Medicine, Winston Salem, North Carolina, USA.

METHODS: This retrospective chart review comprised 9 eyes of 9 patients who had phacoemulsification after LASIK using our method for IOL calculation. This new method assumes the patient never had myopic LASIK to calculate IOL power and then targets the IOL at the pre-LASIK amount of myopia. The pre-LASIK keratometry values, pre-LASIK manifest refraction, and the current axial length are placed in the Holladay formula, bypassing the post-LASIK corneal power. In theory, assuming that the patient had satisfactory LASIK results, the correct IOL can then be determined.

RESULTS: The mean spherical equivalent postoperative refraction was +0.03 diopter (D) +/- 0.42 (SD) (range -0.625 to +0.75 D). In all 9 eyes, our method consistently chose the most accurate and precise IOL compared with other methods.

CONCLUSIONS: The new method of calculating IOL power after LASIK provided excellent results and the most accurate and precise results to date.

_________________
Broken Eyes

"The price good men pay for indifference to public affairs is to be ruled by evil men." Plato


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 Post subject: All patients need their charts from their original surgery
PostPosted: Sun May 07, 2006 1:52 am 
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Notice the success of this method requires pre-op information that can only be obtained from your original LASIK surgeon's office. Go to your original surgeon and request a copy of your complete chart with COLOR copies of your scans for your medical records. You want to do this ASAP before your doctor moves or goes out of business.

You will NEED the pre-op information contained in these records when it is time to have cataract surgery. Having copies of your charts at home can also be educational - learn how to evaluate your own charts... for starters, see 'TAKE THE WAVEFRONT CHALLENGE' for tips on how to see how much corneal permanent, distortion (uncorrectable with glasses) that you acquired as a result of your surgery!

You may want to ask your surgeon why increased corneal distortions were not in your informed consent - doctors know that these distortions are induced by corneal refractive surgery NOT REDUCED, but they don't tell patients.


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PostPosted: Sat Sep 23, 2006 2:53 pm 
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Trans Am Ophthalmol Soc. 2004 December; 102: 189?198.

COMPARISON OF INTRAOCULAR LENS POWER CALCULATION METHODS IN EYES THAT HAVE UNDERGONE LASER-ASSISTED IN-SITU KERATOMILEUSIS

Li Wang, MD PhD, Marc A Booth, MD, and Douglas D Koch, MD*?

From the Cullen Eye Institute, Baylor College of Medicine, Houston, Texas.

An unfortunate consequence of corneal refractive surgery is difficulty in accurately calculating intraocular lens (IOL) power in eyes undergoing cataract surgery.1?3 These IOL power errors can be attributed primarily to three factors: (1) inaccurate measurement of anterior corneal curvature by standard keratometry or computerized videokeratography; (2) inaccurate calculation of corneal power from the anterior corneal measurement by using the standardized value for refractive index of the cornea (1.3375); this occurs because procedures that remove corneal tissue (eg, excimer laser photorefractive keratectomy [PRK] or laser-assisted in-situ keratomileusis [LASIK]) change the relationship between the front and back surfaces of the cornea; and (3) incorrect estimation of effective lens position (ELP) by the third- or fourth-generation formulas when the postoperative corneal power values are used;4,5 the Haigis formula is an exception because it does not use the K-reading for ELP prediction.6

Several methods have been proposed to improve the accuracy of estimating corneal power in eyes that have undergone LASIK. These approaches can be categorized according to whether or not they require knowledge of data acquired before LASIK was performed. Those that depend upon pre-LASIK data and the specific values that are needed include the clinical history method7 (manifest refraction and corneal power values), Feiz-Mannis method8 (manifest refraction and corneal power values), and a topographical method based on adjusting the measured EffRP (EffRPadj)9 (manifest refraction) method. Methods that do not require knowledge of any of the pre-LASIK data include contact lens overrefraction, adjusting corneal power using a correcting factor,10 direct measurement using Orbscan topography,11 and a method proposed by Maloney (Robert K. Maloney, MD, personal communication, October 2002).

Briefly, the calculations in methods evaluated in this study are as follows:

Read the entire article at:
http://www.pubmedcentral.nih.gov/articl ... id=1280099

_________________
Broken Eyes

"The price good men pay for indifference to public affairs is to be ruled by evil men." Plato


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PostPosted: Sun Oct 08, 2006 12:54 am 
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Clin Experiment Ophthalmol. 2006 Sep;34(7):640-4.

Calculation of intraocular lens power after corneal refractive surgery.

Chan CC, Hodge C, Lawless M.

Department of Ophthalmology, Royal North Shore Hospital, Sydney, NSW, Australia.

Purpose: Underestimation of required intraocular lens (IOL) power with resultant hyperopia is common in post-corneal refractive surgery eyes. A number of methods to minimize error have been proposed but most studies have been small and theoretical.

Methods: We retrospectively reviewed 34 eyes that had undergone routine phacoemulsification and IOL implantation after photorefractive keratectomy or laser in situ keratomileusis. Sixteen eyes were included in the final analysis. Using known pre- and postoperative data, four methods were used to obtain keratometric values combined with three common IOL formulae (Holladay 2, SRK/T and Hoffer Q) and Koch's published Double-K nomogram. The Double-K method was also used in conjunction with the Holladay 2 formula. Target refractions were calculated and then compared to actual postoperative results.

Results: The Clinical History method at the spectacle plane produced the lowest mean K-values. Shammas adjustment formula combined with the Holladay 2 and Hoffer Q produced results closest to emmetropia. The Double-K methods produced the least number of hyperopic results. Overall, all methods would have resulted in unacceptably high rates of hyperopia and deviation from target refraction.

Conclusions: No method produces acceptably consistent results because modern IOL formulae were designed for presurgical eyes. Accuracy will only be improved when new IOL formulae based on the anatomy of postrefractive eyes become available. Shammas adjustment formula and regression formulae are viable alternatives especially when there is a lack of preoperative data. The Double-K methods are best suited to avoiding a hyperopic surprise.

_________________
Broken Eyes

"The price good men pay for indifference to public affairs is to be ruled by evil men." Plato


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PostPosted: Mon Dec 04, 2006 12:41 am 
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J Cataract Refract Surg. 2006 Dec;32(12):2004-14.

Estimation of true corneal power after keratorefractive surgery in eyes requiring cataract surgery: BESSt formula.

Borasio E, Stevens J, Smith GT.
From the Moorfields Eye Hospital, London, United Kingdom.

PURPOSE: To describe a new formula, BESSt, to estimate true corneal power after keratorefractive surgery in eyes requiring cataract surgery.

SETTING: Moorfields Eye Hospital, London, United Kingdom.

METHODS: The BESSt formula, based on the Gaussian optics formula, was developed using data from 143 eyes that had keratorefractive surgery. The formula takes into account anterior and posterior corneal radii and pachymetry (Pentacam, Oculus) and does not require pre-keratorefractive surgery information. A software program was developed (BESSt Corneal Power Calculator), and corneal power was calculated in 13 eyes that had keratorefractive surgery and required cataract surgery.

RESULTS: In the eyes having phacoemulsification, target refractions calculated with the BESSt formula were statistically significantly closer to the postoperative manifest refraction (mean deviation 0.08 diopters [D] +/- 0.62 [SD]) than those calculated with other methods as follows: history technique (-0.07 +/- 1.92 D; P = .05); history technique with double-K adjustment (0.13 +/- 2.39 D; P = .05); Holladay 2 with K-values estimated with the contact lens method (-0.76 +/- 1.36 D; P = .03); Holladay 2 with K-values from Atlas topographer (Humphrey) (-0.55 +/- 0.61 D; P<.01). Using the BESSt formula, 46% of eyes were within +/-0.50 D of the intended refraction and 100% were within +/-1.00 D.

CONCLUSIONS: The BESSt formula was statistically significantly more accurate than the other techniques tested. Thus, it could significantly improve intraocular lens power calculation accuracy after keratorefractive surgery, especially when pre-refractive surgery data are unavailable.

_________________
Broken Eyes

"The price good men pay for indifference to public affairs is to be ruled by evil men." Plato


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 Post subject: more on post refractive iol calculations
PostPosted: Mon Dec 04, 2006 2:44 am 
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I have designed a web based refractive surgery database website called

www.safeguardyoursight.com.

The website is designed to store preoperative,operative and postoperative information for refractive surgery patients. This information is important in glaucoma screening and management as well as in calculating intraocular lenses in cataract surgery in post refractive surgery patients.

I think people who visit your site may be interested in the information/services on my site.

please see "new solutions to long term problems with LRS" in the general discussion section for more information on this topic


Last edited by craigbergermd on Fri Dec 15, 2006 5:12 am, edited 1 time in total.

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 Post subject: We do not endorse this for-pay medical records site
PostPosted: Wed Dec 06, 2006 12:52 am 
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If Dr. Craig Berger MD were genuinely interested in saving your sight he would be out preventing his colleagues from performing harmful surgeries, and would refrain from performing them himself. Instead he's trying to make a buck off known damage related to corneal refractive surgery that will cause you future medical concerns.

Keep your money out of the pockets of those involved with the LASIK industry, and store a copy of your own medical records at HOME.


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PostPosted: Sat Dec 09, 2006 1:57 pm 
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Compr Ophthalmol Update. 2006 Sep-Oct;7(5):243-51.

Refractive power of the cornea.

Ayres BD, Rapuano CJ.

Cornea Service, Wills Eye Institute, Thomas Jefferson University, Philadelphia, PA.

Corneal refractive surgeries, such as laser in situ keratomileusis and photorefractive keratectomy, have become some of the most commonly performed elective surgical procedures today. Many of the patients undergoing these surgeries are beginning to show signs of cataract formation and are in need of surgical correction. A common problem in the postrefractive patient is accurate prediction of the corneal power for use in intraocular lens calculation. The purpose of this article is to review the literature and to discuss why it is difficult to determine the power of the postkeratorefractive cornea, and to describe the multiple techniques used to assist in calculation of the power of the cornea. We will also examine some of the current technological advances that may aid in power calculation. With proper patient history, examination, and careful calculation(s), it is possible to closely estimate the refractive power of the postkeratorefractive cornea.

_________________
Broken Eyes

"The price good men pay for indifference to public affairs is to be ruled by evil men." Plato


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PostPosted: Wed Jul 04, 2007 2:39 am 
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Calculating Intraocular Lens Geometry by Real Ray Tracing

Journal of Refractive Surgery Vol. 23 No. 4 April 2007

Jens Einighammer, Dipl-Inform; Theo Oltrup, Dipl-Ing; Thomas Bende, PhD; Benedikt Jean, MD


Quote:
These IOL calculation formulae are easy to use and produce satisfying results for normal eyes. The performance of the classical formulae is getting worse for corneas with an abnormal shape (eg, those with previous refractive surgery). Implanting IOLs calculated with standard formulae for a patient with previous correction of myopia by laser in situ keratomileusis (LASIK), laser epithelial keratomileusis (LASEK), or photorefractive keratectomy (PRK) typically results in a hyperopic shift compared to the target refraction.


Quote:
The theoretical optical IOL calculation formulae rely on paraxial optics. This in only an approximation of Snell?s law for small angles and therefore results in considering only paraxial rays (only rays near the optical axis) and is only valid for spherical surfaces. A sphere has an asphericity of zero. A negative asphericity stands for a prolate shape, a positive for an oblate shape. An average cornea is prolate; a cornea after LASIK/LASEK/PRK correction of myopia is typically oblate. Having equal central corneal power but different asphericity leads to a different focus when analyzed with real ray tracing. Two problems arise when calculating an IOL for a cornea with unusual asphericity: 1) the measurement by keratometry introduces an error by under- or overestimating the central corneal power16 and 2) the IOL calculation introduces an error because the formulae are assuming the asphericity of an average cornea because the lens constants are optimized for normal corneas having an average asphericity. There is another challenge concerning corneas with previous refractive surgery (LASIK/LASEK/PRK). The cornea principally consists of two refracting surfaces: the anterior and posterior surface.


Quote:
In refractive surgery, the anterior corneal surface is modified without affecting the posterior surface. As a result, the back-to-front ratio for normal eyes is no longer valid for refractive treated eyes.

_________________
Broken Eyes

"The price good men pay for indifference to public affairs is to be ruled by evil men." Plato


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PostPosted: Mon Sep 03, 2007 1:53 pm 
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Correlation Between Attempted Correction and Keratometric Refractive Index of the Cornea After Myopic Excimer Laser Surgery
Journal of Refractive Surgery Vol. 23 No. 5 May 2007
Giacomo Savini, MD; Piero Barboni, MD; Maurizio Zanini, MD

Quote:
Inaccurate calculation of intraocular lens (IOL) power after refractive surgery has been the subject of considerable attention in the past decade. It is widely recognized that using videokeratography underestimates corneal flattening after myopic excimer laser surgery. As a consequence, standard keratometric values lead to IOL power underestimation (with subsequent hyperopia) in eyes that have previously undergone myopic photorefractive keratectomy (PRK) or LASIK.1,2

_________________
Broken Eyes

"The price good men pay for indifference to public affairs is to be ruled by evil men." Plato


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