Journal of Refractive Surgery Vol. 22 No. 2 February 2006
Manuel Ramírez, MD; Everardo Hernández-Quintela, MD, MSc; Valeria Sánchez-Huerta, MD; Ramón Naranjo-Tackman, MD
PURPOSE: To describe the morphological characteristics of microfolds that appear at the corneal flap after LASIK, as seen under confocal microscopy.
METHODS: Twenty-one eyes that had undergone LASIK were examined, all within 3 weeks to 1 month after surgery. A central scan of the total corneal thickness was obtained by using confocal microscopy in vivo. Confocal images were captured and digitized. The longitudinal orientation (vertical, horizontal, and oblique) and morphological characteristics of the microfolds were described and recorded.
RESULTS: Six eyes had folds at the central corneal flap, visible as linear distortions in the confocal images: one fold had a vertical orientation, two were horizontal, and three were oblique. The folds were visible from the epithelial basal cell layer to the stromal portion of the flap and were deeper than Bowman’s layer.
CONCLUSIONS: Confocal microscopy allowed visualization of microfolds after LASIK. With the appropriate software, it is possible to analyze the morphological characteristics of these folds. Flap microfolds after LASIK are deeper than Bowman’s layer.
Graefes Arch Clin Exp Ophthalmol. 2001 Jul;239(6):416-23.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11561789&query_hl=11&itool=pubmed_docsum
Luna JD, Artal MN, Reviglio VE, Pelizzari M, Diaz H, Juarez CP. Fundacion Ver, Cordoba, Argentina
BACKGROUND: The presence of vitreoretinal changes following laser in situ keratomileusis in myopia is evaluated.
METHODS: Clinically, 50 patients (100 eyes) with marked anisometropic myopia, 50 low-myopic eyes (<4.00 D) and 50 high-myopic eyes (>7.00 D) were prospectively evaluated pre- and postoperatively for the presence of newly recognized entoptic phenomena (vitreous floaters, light flashes, or both), and for vitreoretinal changes using indirect depressed fundus examination, a +90 D preset lens, Goldman three-mirror contact lens, and kinetic ultrasound (KU) before and after bilateral LASIK. Patients with previous partial or total posterior vitreous cortex detachment (PVD) were excluded. Experimentally, groups of adult pigs underwent KU, retinal fluorescein angiography (FA), and electroretinography (ERG) before and after applying the microkeratome suction ring for 30 s.
RESULTS: Clinically, 8% (4 eyes) had positive perception of postoperative vitreous floaters in the low myopia group, and 32% (16 eyes) in the high myopia group. Postoperative light flashes were noted only in the high myopia group, in 12% of cases. Partial or total posterior vitreous cortex detachment was detected by biomicroscopy in 2% (1 eye) of the low and in 10% (5 eyes) of the high myopia group and by KU in 4% (2 eyes) of the low and in 24% (12 eyes) of the high myopia group. Experimentally, 2 pig eyes out of 12 developed partial PVD by KU, immediately after microkeratome suction ring application. All pig eyes showed significantly diminished ERG amplitudes during and immediately after suction ring application. No FA changes or delays in retinal circulation time were noted during or immediately after removal of the suction ring.
CONCLUSIONS: Vitreoretinal alterations after LASIK were demonstrated clinically mainly by KU in high myopes. Experimentally, PVD were also demonstrated. Diminished ERG recordings with normal retinal circulation following suction ring application may suggest some transient choroidal circulation abnormalities.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12498850&query_hl=1
J Cataract Refract Surg. 2002 Dec;28(12):2146-52.
Charman WN.
Department of Optometry and Neuroscience, UMIST, PO Box 88, Manchester M60 1QD, United Kingdom. neil.charman@umist.ac.uk
PURPOSE: To calculate theoretically the magnitude of the excess area between the lower surface of the flap and the underlying ablated stroma.
METHODS: On the initial assumptions of a nonextensible flap and a spherical cornea, flap and ablated stromal areas were determined as a function of myopic correction in the range of 0 to -12 diopters (D) for typical values of corneal radius (7.8 mm) and flap thickness (160 microm), together with a range of ablation zone diameters (4.0 mm, 6.0 mm, 8.0 mm, and 10.0 mm).
RESULTS: Excess flap area increases with the magnitude of the refractive correction and the diameter of the ablated zone. For a -6.0 D correction and an 8.0 mm ablation zone, the excess area is nominally about 1.0 mm(2), giving a potential overlap of the flap at the edge opposite the hinge of about 100 microm.
CONCLUSIONS; Excess flap area may cause striae because of wrinkling. Although a nonextensible flap is assumed in the model, any stretching or contraction due to cutting the flap will be independent of the refractive correction. Hence, a mismatch in areas must still occur. This geometric effect may have clinical consequences in optical aberration, refractive regression, or impaired wound healing.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15506491&query_hl=1&itool=pubmed_docsum
Nippon Ganka Gakkai Zasshi. 2004 Sep;108(9):566-71.
Bilateral retinal detachment after laser in situ keratomileusis
Kohzaki K, Sano Y, Toda K, Mitooka K, Nakamura Y, Kitahara K. Department of Ophthalmology, Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105 8461, Japan.
BACKGROUND: We report a case of bilateral retinal detachment after laser in situ keratomileusis(LASIK).
CASE: A 49-year-old man received multiple laser photocoagulation for retinal lattice degeneration in both eyes and retinal tears in the left eye. He underwent bilateral LASIK in another country about 6 months after the laser photocoagulation. After the LASIK his eyes showed bilateral retinal detachment, 2 weeks later in the right eye and 5 months later in the left eye. We had to perform retinal detachment surgery four times, scleral buckling, vitrectomy, silicone oil tamponade, and removal of the silicone oil for the right eye, and one scleral buckling procedure for the left eye to achieve retinal attachment. Soon after each retinal surgery, we recognized diffuse flap edema and interface haze, three times in the right cornea and one time in the left, although this corneal flap edema subsided without any sequel.
CONCLUSION: In this case, laser photocoagulation had been done several times to prevent retinal detachment in both eyes. However, retinal detachment occurred 2 weeks after LASIK in the right eye, and therefore, the LASIK procedure was considered to be the main factor influencing the development of the retinal detachment. The left eye showed retinal detachment 5 months after LASIK and we thought it possible that this retinal detachment occurred as a natural consequence of myopia. We believe it is important to hava a thorough funduscopic examination done before LASIK and it is necessary to pay attention to corneal edema and interface haze after retinal detachment surgery for post-LASIK patients.
J Cataract Refract Surg. 2005 Dec;31(12):2356-62.
Brown SM, Freedman KA. Cabarrus Eye Center, Concord, North Carolina 28025, USA. sbrownmd@carolina.rr.com
PURPOSE: To determine whether the currently accepted method of selecting a minimum optical zone diameter for laser refractive surgery that is equal to or slightly greater than the dark-adapted pupil diameter provides a sufficient diameter of corneal surface to focus light arising from objects in the paracentral and peripheral visual field.
SETTING: Department of Ophthalmology and Visual Sciences, Texas Tech University Health Sciences Center, Lubbock, Texas, USA.
METHODS: An optical model of the anterior segment was developed to calculate the effective corneal refractive diameter (ECRD), which is the diameter of the area of cornea that refracts all incident light rays arising from an object through the physical pupil (PP). This model incorporates the patient variables of central anterior chamber depth (ACD), central corneal curvature (K(c)), and the diameter of the apparent entrance pupil (EP). The model was expanded to incorporate distant objects off the line of sight (LOS), described by their angular displacement from the fixation object in visual space (the object tangent angle delta(ob)). Results were calculated for the 360 meridian degree visual field (ie, for all objects in visual space perceptually displaced from the fixation object by angle delta(ob)). The effect of the prolate nature of the cornea was also investigated.
RESULTS: The ECRD expanded rapidly as a function of PP and delta(ob) but was minimally influenced by K(c). Beyond a critical object tangent angle delta(c), light rays striking the corneal vertex were not refracted through the PP, and the ECRD became an annular surface centered on the corneal vertex. The delta(c) was not a function of K, but increased as the PP increased and decreased as the ACD increased. The prolate nature of the cornea had little influence on the ECRD, even for very peripheral light rays.
CONCLUSIONS: The ECRD expands rapidly when considering distant objects only slightly displaced from the LOS. A patient treated with an optical zone equal to or slightly greater than the dark-adapted pupil diameter may experience vision quality loss for paracentral and midperipheral objects even under conditions of ambient indoor lighting.
J Cataract Refract Surg 2003; 29:250–256
Joseph K.W. Hsu, MD, W. Todd Johnston, MD, Russell W. Read, MD, Peter J. McDonnell, MD, Rey Pangalinan, MD, Narsing Rao, MD Ronald E. Smith, MD
Purpose: To describe the histopathology of the cornea in 3 cases of corneal melting associated with diclofenac therapy after refractive surgery procedures.
Setting: Clinic and pathology laboratory.
Methods: Three cases of corneal melting associated with diclofenac therapy (2 after laser in situ keratomileusis [LASIK] and 1 after mini-radial keratectomy enhancement of a LASIK undercorrection) were studied using patient and referring physician interviews, chart reviews, and histopathologic examination of the corneal tissue.
Results: In all 3 cases, the flaps were dislocated and the stromal corneal bed was exposed. Diclofenac, generic or brand name, was used in all cases; in 1 case, both generic and brand name were used. Dosing and duration varied, but in all 3 cases diclofenac was used at least 4 times a day for at least 3 days after LASIK. Topical steroids were also prescribed, but 1 patient did not use them. Preoperative medical conditions were present in 2 cases. Histologic analysis showed evidence of an inflammatory response in advanced cases and keratolysis and lack of inflammatory cells in the flaps that were amputated early.
Conclusions: The use of generic or brand-name diclofenac with or without adjunctive topical steroids after LASIK can be associated with corneal melting when the LASIK flap is dislodged and the corneal stromal bed exposed. Caution is recommended with diclofenac use after LASIK in such cases.
Cataract Refract Surg. 2002 Mar;28(3):407-16.
Huang D, Arif M.
Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA. huangd@ccf.org
PURPOSE: To investigate the effect of laser spot size on the outcome of aberration correction with scanning laser corneal ablation.
SETTING: Cleveland Clinic Foundation, Cleveland, Ohio, USA.
METHODS: Corrections of wavefront aberrations of Zernike modes from the second to eighth order were simulated. Gaussian and top-hat beams of 0.6 to 2.0 mm full-width-half-maximum diameters were modeled. The fractional correction and secondary aberration (distortion) were evaluated.
RESULTS: Using a distortion/correction ratio of less than 0.5 as a cutoff for adequate performance, a 2.0 mm or smaller beam was adequate for spherocylindrical correction (Zernike second order), a 1.0 mm or smaller beam was adequate for correction of up to fourth-order Zernike modes, and a 0.6 mm or smaller beam was adequate for correction of up to sixth-order Zernike modes.
CONCLUSIONS: Since ocular aberrations above the Zernike fourth order are relatively insignificant in normal eyes, current scanning lasers with a beam diameter of 1.0 mm or less are theoretically capable of eliminating most higher-order aberrations.
Optometry & Vision Science. 82(5):428-431, May 2005.
BY William I. Bond, MD; Jack T. Holladay, MD, MSEE, FACS; Steven J. Dell, MD; James Schumer, MD; and Sam Omar, MD
I don’t think that customized LASIK will replace standard LASIK for at least the next 2 or 3 years. The first reason is that the technology simply isn’t there yet. We talk about customized LASIK technology a lot, but I don’t feel that it is accomplishing what it promises. We are only beginning to be able to measure higher-order aberrations with time-consuming and cumbersome technology, and we are unable to measure aberrations with any real sense of confidence or consistency.
The desire for surgeons to be able to say that they possess “customized” or “wavefront” technology pervades the refractive industry and currently far outstrips our ability to deliver concrete results to patients. There are so many treatments currently available that we refer to as “customized,” “wavefront,” “tailor-made,” or “individualized.” Abraham Lincoln said, “If you call a tail a leg, how many legs does a dog have? Well, the answer is four, because calling a tail a leg doesn’t make it a leg.”More importantly, however, I feel that we are unsure of what we are trying to accomplish in correcting aberrations. I remember believing that a cornea free of aberrations was a desirable state of affairs, but that was just an assumption. Now, we are finding that 20/10 and 20/8 vision can exist with fairly large aberrations, and we aren’t certain what to make of that. Until we determine what the desired refractive state really is, the great hope for customized LASIK is to be able to address previously induced refractive surgical problems. This indication could be a godsend for long-suffering patients and their long-suffering surgeons.
In order to perform customized ablations effectively, the laser must be able to do what we ask it to do. Specifically, there is not a single laser on the US market today that delivers the appropriate overall energy for the ablations we perform. The reason is that the lasers are calibrated on a flat surface, so their energy is always delivered perpendicular to the treatment site. Because the cornea is not flat, the lasers today only deliver the appropriate amount of energy to the central point of the treatment site, where it is perpendicular. As the beam moves farther out, regardless of the type of beam it is, it strikes the periphery of the treatment zone obliquely, so its energy diminishes from what is necessary for the proper ablation. Our data show that the lasers are actually undertreating in the periphery—at 6.0 mm, it is about 25% reduced from its designated calculation—and in doing so, they make the cornea more oblate, rather than preserve its natural prolate shape.
I recognized this problem with excimer lasers about 3 years ago, and I have since added a new algorithm to the software of the LaserScan LSX excimer laser (LaserSight Technologies, Inc., Winter Park, FL) that increases the amount of laser energy to compensate for hitting the cornea obliquely. Of the 20 patients I have treated with this new software, all have postoperative corneas that are shaped exactly like virgin corneas. They do not have a shrinking optical zone such as those induced by current standard treatments, and these patients’ contrast sensitivity and wavefront measurements are as good as those of patients who have never undergone surgery. Moreover, these treatments were standard—not what we would normally refer to as a customized ablation.1 Correcting the systematic calibration errors in the lasers will produce better results than the wavefront-guided ablations performed today.From my perspective, there will not be significant differences between the outcomes of customized over conventional ablations, but there will be a noticeable improvement if we calibrate all laser systems to compensate for their error when they hit the cornea obliquely. I believe that correcting the calibration error will account for approximately 99% of the improvement that patients will then receive from corneal laser surgery, and the other 1% will be attributable to customized wavefront technology. The aberrations that wavefront technology corrects are minute compared with the spherical aberrations induced by the calibration error of the lasers. I also feel that we currently understand too little about wavefront technology to significantly benefit patients who see well with glasses and contact lenses; I think that patients with more difficult visual problems will benefit most from customized ablations.
With the widespread use of customized ablation just around the corner, are we about to witness the technological obsolescence of standard LASIK? The answer is more complex than it may seem on the surface. The concept of customized treatment is very appealing, both to patients and surgeons. We obtain a unique map of each individual eye and custom tailor the treatment accordingly. This obviously will be better than an “off-the-rack” treatment, right?
Some early studies with wavefront treatments have demonstrated better UCVA and BCVA as compared with standard treatments, with fewer induced higher-order aberrations. In many cases, wavefront treatments have reduced spherical aberration in particular and improved night vision. These are remarkable achievements, but which specific aberrations should we eliminate? In a very interesting study presented at the 2001 AAO meeting in Orlando, Florida, Steven Schallhorn, MD, examined aviators at the Navy’s Top Gun school in Nevada. He looked at higher-order aberrations in individuals who had not undergone any type of refractive surgery. Surprisingly, he found that individuals with the very best UCVA had more higher-order aberrations than those with worse UCVA. Should we aim to leave some higher-order aberrations on the cornea, and if so, which ones? This question obviously warrants further study.
Additionally, it has been shown that creating a LASIK flap induces aberrations that are unpredictable. Does this fact steer us more in the direction of surface ablation for customized work? Perhaps, but the epithelial remodeling that occurs for months following surface ablation creates its own constellation of aberrations. Even after LASIK, we see substantial epithelial changes for many months. It will also be interesting to see how lenticular changes affect the situation. In my practice, the average patient requesting refractive surgery is 41 years old, and many individuals are in their 50s. How will these patients fare in the long term, and how will we deal with their residual aberrations when we extract a substantial component of the aberration equation at the time of cataract surgery? Pupil size is another factor that dramatically affects the wavefront profile of any given eye. As this variable changes from moment to moment and in general shrinks with time, how will this influence matter?
Customized ablations hold huge potential in refractive surgery. There are many patients with irregular corneas resulting from problems with prior refractive surgeries who may benefit substantially from this technology. Applying customized ablation to the mainstream refractive surgery patients will require careful consideration of all these issues. The analogy of a “made-to-measure” suit versus an “off-the-rack” suit certainly applies, but we should bear in mind that, if we gain or lose 5 pounds in a few years, or styles change, we can simply buy another suit. Customized ablation is for the duration.
Wavefront technology and customized ablations are in their infancy. However, the tremendous impact these advances will have on our surgical strategies and treatment options is quickly becoming clear. In order to answer the question of whether customized treatments will replace standard LASIK procedures, we first have to agree on the definition of customized ablation. Does it mean simply wavefront-guided ablations, or does it mean reducing the higher-order aberrations of an eye using wavefront technology? This distinction is not a subtle one and is very important to understand for the following reasons. Alcon’s LADARVision 4000 is the first excimer laser in the US approved for customized ablation. However, the pre- and postoperative wavefronts taken of the participants in the study show that their average higher-order aberrations increased after treatment. Although the LADARVision’s customized-ablation approval will allow surgeons to treat eyes using wavefront technology, we are not yet able to reduce pre-existing higher-order aberrations. In fact, we are still increasing higher-order aberrations with our current treatments.
Clinical diagnostic wavefront analysis is teaching us that visually significant higher-order aberrations measured preoperatively are not the norm in our refractive surgery population. In other words, completely correcting sphere and cylinder surgically, without inducing visually significant higher-order aberrations, will delight nearly 100% of our refractive surgery patients. However, it is the atypical refractive surgery patient who complains of higher-order aberrations preoperatively, while most postoperative complaints are due to surgically induced higher-order aberrations (ie, spherical aberration).
Therefore, I feel that wavefront-guided customized ablations will eventually supplant the phoropter-guided LASIK procedures surgeons currently perform. The phoropter, manifest, and cycloplegic refractions will become safety checks included in preoperative evaluations, but they will no longer be the driving parameters of the excimer laser treatment. However, customized ablation (ie, treating the higher-order aberrations of an eye) will not be the typical treatment objective in the refractive surgery population, due to the ocular demographics that show that the number of lower-order aberrations far exceed higher-order aberrations in terms of visual significance. Formulating treatment parameters that eliminate and prevent the induction of higher-order aberrations remains elusive, but the journey will be stimulating and provide us with true customized-ablation (ie, treatment of higher-order aberrations) potential.
"New-and-improved" is a marketing tactic employed by companies in order to boost their corporate bottom line. Physicans need to cautiously evaluate any revolutionary or evolutionary refractive technology. The refractive surgery industry is extremely motivated to promote new-and-improved technologies, particularly in the form of wavefront-guided refractive surgery, which may supplant current, “conventional” LASIK surgery. Unfortunately for the industry, wavefront technology is still in its infancy, and conventional treatments now feature improved ablation algorithms, smoother ablations, blend zones, and optimized optical zones, which all eliminate many differences between conventional and wavefront-guided LASIK treatments. This comparison has been well demonstrated in countries that are 12 to 18 months ahead of the US in developing refractive technology, and thus far, customized LASIK procedures have not displaced conventional LASIK in these advanced, foreign settings.
Until our understanding of wavefront technology improves, refined conventional refractive treatments may actually outpace wavefront treatments for consistent, effective, and stable refractive results. The potential of conventional treatments can be seen when comparing the postoperative results from specific excimer platforms with the wavefront-guided postoperative results of competing excimer laser platforms. Prior to achieving “supervision” for virgin eyes, the refractive industry needs to develop additional treatments to re-treat postrefractive surgery patients who manifest suboptimal outcomes with decreased BSCVA and decreased-quality mesopic/scotopic vision. Once refractive surgeons develop more effective methods for treating irregular astigmatism and safer microkeratome technology, refractive surgery’s penetration into the general population will tremendously enhance the industry's perceived and actual safety rate.
In order for wavefront-driven excimer treatments to displace conventional LASIK, a number of philosophic and technological hurdles must be overcome. Due to the pioneering work of Cynthia Roberts, PhD, of Columbus, Ohio, and Dan Reinstein, MD, of Cambridge, England, wavefront researchers have begun to comprehend the effect of biomechanical changes in the cornea induced during the lamellar surgical portion of LASIK. The fact that so few wavefront investigations include standardized microkeratome variability partially demonstrates the limits of current refractive surgery knowledge. Because wavefront treatments require micron and submicron resolution, a greater working knowledge of the factors involved with epithelial and stromal wound-healing responses will be critical to maximizing successful customized ablations. Elevation-based topography data must be incorporated into these treatments in order to provide the highest-probability “best fit” for a customized ablation. Current excimer laser beam delivery and tracking technology is rapidly improving, but it still lags behind what is theoretically required to perform wavefront-driven customized ablations. Additionally, adaptive optics, which introduce virtually any desired aberration profile into a subject's eye, must be refined to evaluate a patient’s vision for each controlled aberration profile. This “wavefront phoropter” or “visual simulator” would allow surgeons to determine the exact relationships between specific aberrations and visual quality.
Despite the best designs of current wavefront investigational trials, until the issues described previously are rigorously developed and applied, any significant visual improvement via customized wavefront ablations will be entirely accidental and difficult to reproduce. Therefore, it is unlikely that in the near future customized LASIK will unseat conventional LASIK as king of the refractive marketplace.
William I. Bond, MD, is Director of Bond Eye Associates in Pekin, Illinois. He holds no financial interest in any technology discussed herein. Dr. Bond may be reached at (309) 353-6660; bondeye@bondeye.com.
Jack T. Holladay, MD, MSEE, FACS, is Clinical Professor of Ophthalmology at Baylor College of Medicine in Houston, as well as Medical Director of LaserSight Technologies, Inc., in Winter Park, Florida. Dr. Holladay may be reached at (713) 668-7337; docholladay@docholladay.com.
Steven J. Dell, MD, is Director, Refractive and Corneal Surgery at Texan Eye Care in Austin, Texas. He holds no financial interest in any product or technology mentioned herein. Dr. Dell may be reached at (512) 327-7000; sdell@austin.rr.com.
James Schumer, MD, is in private practice at Eye Surgery Consultants in Mansfield, Ohio. He holds no financial interest in any product or technology mentioned herein. Dr. Schumer may be reached at (419) 525-3737; schumer@revisioneyes.com.
Sam Omar, MD, is from Advanced Vision Institute in Orlando, Florida. He holds no financial interest in any product or technology mentioned herein. Dr. Omar may be reached at (407) 389-0800; omar_eye@yahoo.com.
Indian J Ophthalmol. 2004 Dec;52(4):327-8. Related Articles, Links
Late dislocation of LASIK flap following fingernail injury.
Srinivasan M, Prasad S, Prajna NV.
Aravind Eye Hospital & Postgraduate Institute of Ophthalmology, Madurai, India.
A case of traumatic flap displacement with a fingernail injury four years after LASIK is reported.
Late traumatic dislocation of LASIK flaps (2)
J Cataract Refract Surg. 2004 Jan;30(1):253-6. Related Articles, Links
Late traumatic dislocation of laser in situ keratomileusis flaps.
Heickell AG, Vesaluoma MH, Tervo TM, Vannas A, Krootila K.
Helsinki University Eye Hospital, Helsinki, Finland.
Excerpt:
We present 2 patients with late traumatic laser in situ keratomileusis flap dislocation 8 months and 17 months after surgery. One patient had a sharp trauma that caused a partial laceration and the second patient had a blunt trauma that caused a dislocation of the flap. The corneas were examined with slitlamp microscopy, computed corneal topography, and confocal microscopy. One flap was repositioned surgically; the other was treated conservatively with an eye patch.
Journal of Refractive Surgery Volume 21 November/December 2005
Keratoconus and Corneal Ectasia After LASIK
Perry S. Binder, MS, MD; Richard L. Lindstrom, MD; R. Doyle Stulting,MD, PhD; Eric Donnenfeld, MD; Helen Wu, MD; Peter McDonnell, MD; YaronRabinowitz, MDExcerpt: Ectasia is a known risk of laser vision correction, and if ectasiaoccurs in a patient following laser vision correction it does notnecessarily mean that the patient was a poor candidate for surgery, that the surgery was contraindicated, or that there was a violation of thestandard of care.
More Studies & Articles - Click Read More
DESIGN: Prospective, noncomparative case series.
MAIN OUTCOME MEASURES: Components of the integrated ocular surface/lacrimal gland unit.
J Refract Surg. 2000 Nov-Dec;16(6):739-43.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11110315&query_hl=1&itool=pubmed_docsum
Comment in: J Refract Surg. 2001 Mar-Apr;17(2):153-4.
Farah ME, Hofling-Lima AL, Nascimento E. Federal University of Sao Paulo, Paulista School of Medicine, Brazil. mefarah@uol.com.br
PURPOSE: Four eyes had early rhegmatogenous retinal detachment within 3 months of laser in situ keratomileusis (LASIK) for correction of high myopia using the microkeratome, Clear Corneal Molder.
METHODS: In two eyes, retinal detachment resulted from horseshoe tears, one occurring in an otherwise normal region of the retina and the other at the margin of an area of lattice degeneration detected during preoperative examination. The first eye was treated with retinopexy using a 287 encircling scleral exoplant, drainage of subretinal fluid, and laser photocoagulation by indirect ophthalmoscopy. The other eye was treated with pneumatic retinopexy and cryotherapy. In the other eyes, retinal detachment was the result of giant tears with no evidence of prior retinal degeneration. These eyes were treated with pars plana vitrectomy, fluid-gas exchange with 15% perfluoropropane (C3F8), endolaser photocoagulation, and a 42 encircling scleral exoplant.
RESULTS: After treatment, the first two eyes achieved spectacle-corrected visual acuity of 20/40. In the last two eyes, final spectacle-corrected visual acuity was 20/400 in one eye and light perception in the other.
CONCLUSIONS: Although no cause-effect relationship between LASIK and retinal detachment can be stated, these cases suggest that LASIK may be associated with retinal detachment, particularly in highly myopic eyes. Further studies are necessary to determine high-risk patient characteristics.
J Cataract Refract Surg. 2005 May;31(5):922-9.
Loh RS, Hardten DR. Minnesota Eye Consultants, Minneapolis, Minnesota, USA.
PURPOSE: To report persistent unilateral flap edema following laser in situ keratomileusis (LASIK) in patients with asymmetrical central corneal thickness.
SETTING: Minnesota Eye Consultants, Minneapolis, Minnesota.
METHODS: Retrospective, noncomparative interventional case series.
RESULTS: We examined 6 eyes of 3 patients with asymmetrical preoperative pachymetry who developed persistent unilateral flap edema after uneventful myopic LASIK in the eye with thicker preoperative pachymetry. All cases had asymmetrical preoperative pachymetry with flap edema developing in the eye with higher preoperative mean central corneal thickness (CCT) values, preoperative mean CCT subject eye 622 microm (range 556-664 microm) versus fellow eye 583 microm (range 510-621 microm). There was no associated ocular inflammation or rise in intraocular pressure. Significant flap edema resolved on a combination treatment of topical steroid and hypertonic saline.
CONCLUSIONS: Laser in situ keratomileusis can cause temporary endothelial cell dysfunction or stress, which manifests as temporary flap edema and subclinical corneal thickening. The edema appears to be limited to the actual flap and there was no loss of epithelial integrity in these eyes and no clinically noticeable interface fluid. This new clinical entity appears to occur in patients with asymmetrical preoperative corneal pachymetry and is associated with postoperative specular microscopy abnormalities. In cases with unexplained asymmetrical corneal thickness, preoperative evaluation should include specular microscopy to evaluate for risk features that may increase the chances of a slower postoperative recovery.
J Refract Surg. 2006 Nov;22(9):884-9.Landau D, Levy J, Solomon A, Lifshitz T, Orucov F, Strassman E, Frucht-Pery J.
Cornea and Refractive Surgery Unit, Dept of Ophthalmology, Hadassah University Hospital, P.O.B. 12000, Jerusalem 91120, Israel. dvl_eyes@netvision.net.il
PURPOSE: To report our experience treating eye trauma after LASIK refractive surgery.
METHODS: Nine eyes of eight patients (one woman and seven men) were treated for ocular trauma: blunt trauma (n=5), sharp instrument trauma (n=2,) and trauma from inflation of automobile air bags during a traffic accident (n=2). The time from LASIK varied between 3 months and 6 years. All patients were hospitalized as a result of severe decrease in visual acuity and pain.
RESULTS: Seven of nine LASIK flaps had some degree of dislocation and were lifted, irrigated, and repositioned. Two flaps were edematous without dislocation. Intensive topical steroids and antibiotics were used in all patients up to 3 weeks after trauma. Three months after trauma, five eyes regained their pre-trauma visual acuity (between 20/20 and 20/40), and three eyes lost one line of best spectacle-corrected visual acuity.
CONCLUSIONS: Trauma occurring several months or years after LASIK may cause flap injury. Adequate and prompt treatment usually is successful.
Volume 31, Issue 2 , February 2005, Pages 379-384
"Glare is induced by rays of light that enter the pupil through the portion of the cornea outside the ablation area. A larger pupil allows more errant light rays to reach the retina and degrade the perceived image. For this reason, a larger ablation zone is required in patients with large pupils and high myopic corrections".
EyeWorld Weekly News Volume 10, Number 44 November 28, 2005 http://www.eyeworld.org/ewweek.php?id=395#2 The optical zone/pupil ratio (fractional clearance, FC) has a significant impact on HOA induction after wavefront-guided LASIK, according to a study to be published in the December issue of the Journal of Cataract & Refractive Surgery. The study, “Influence of pupil and optical zone diameter on higher order aberrations after wavefront-guided myopic LASIK,” examined 27 myopic eyes of 19 patients. It was authored by Jens Bühren, M.D.; Christoph Kühne, M.D.; and Thomas Kohnen, M.D. Goethe University, Frankfurt am Main, Germany. They wrote that the ratio of optical zone to pupil was higher correlated with HOA induction after wavefront-guided LASIK than pupil diameter alone. The change in HOA root mean square and primary spherical aberration (Z 4, 0) was significantly correlated with FC, according to the study. If the optical zone [OZ] was 16.5% larger than the pupil (FC=1.17), only half of the amount of HOA is expected to be induced as if the OZ equaled the pupil, Dr. Bühren wrote. In contrast, an OZ that was 9% smaller than the pupil (FC=0.91) resulted in an HOA induction of 50% higher as at FC=1, according to the study. All patients underwent uneventful wavefront-guided LASIK using a Zyopix laser (Bausch & Lomb, Rochester, N.Y.).
http://www.crstodayarchive.com/03_archive/0503/17.html
Cataract & Refractive Surgery Today May, 2003
Spherical Aberration and Its Symptoms Theories on why it occurs and how new technology may address the problem.
BY MARIA REGINA CHALITA, MD, AND RONALD R. KRUEGER, MD, MSE
SYMPTOMS CORRELATED WITH SPHERICAL ABERRATIONS: Standard laser refractive surgery performed on patients with large scotopic pupil sizes is associated with nighttime vision problems such as halos.12 The increased amount of higher-order aberrations after standard LASIK is consistent with the relatively common patient comment, “I can read 20/20, but my vision is not as good as it was before.”13 We analyzed 105 eyes that underwent LASIK correction and correlated their symptoms with higher-order aberrations. Our analysis of optical symptoms and measured aberrations for a scotopic pupil size showed a statistically significant correlation between higher-order aberrations and glare (P=.041) as well as starburst (P=.004). When we broke down these aberrations into individual Zernike components, spherical aberration was the predominant cause, with a statistically significant correlation to glare (P=.010) and starburst (P=.014). Halos seemed to be associated with spherical aberration for the scotopic pupil size (P=.053). Table 1 shows the relationship of spherical aberration and coma with patients’ symptoms.
SPHERICAL ABERRATION PREVENTION AND CORRECTION: Surgeons must exercise care when treating eyes with larger scotopic pupils, especially if the procedure is expected to induce higher levels of spherical aberration (patients with large pupils will experience more symptoms with higher levels of spherical aberration). Customized laser ablations attempt to minimize these symptoms by more effectively avoiding laser-induced spherical aberrations. The ideal ablation profile for correcting refractive error without generating spherical aberration is to reshape the cornea with a lesser radius of curvature in the midperiphery rather than in the center. This difference in asphericity corrects the spherical aberration of the eye, because the flatter surface will cause less refraction of the peripheral rays.14
OPTOMETRIST SPECIALIZING IN POST-REFRACTIVE SURGERY DISASTERS CLAIMS THAT FAILED LASIK EYE SURGERY IS DEPLETING SUPPLY OF DONOR CORNEAS...
Dr. Greg Gemoules, OD of Coppell, TX, an Optometrist who specializes in repairing the vision of patients damaged by refractive surgery by fitting them with hard contact lenses, claims that hard contact lenses, known as RGP’s or ‘rigid gas permeable’ lenses are the best option for those with laser-ruined eyesight. One reason he cites to promote RGP use for these visually compromised patients is a lack of availability of donor corneas due to the widespread practice of LASIK eye surgery.
Gemoules also claims that many corneal transplant recipients have worse vision than those with “LASIK difficulties”.
Gemoules stated:
“Many patients with corneal grafts have worse problems than patients with post-LASIK difficulties, and STILL require RGP contact lenses afterwards. Besides, the donor pool for donor corneas is being reduced by the number of patients who are getting LASIK.”
Posted Here
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16129288&query_hl=26
J Cataract Refract Surg. 2005 Aug;31(:1537-43.
Garamendi E, Pesudovs K, Elliott DB.
Department of Optometry, University of Bradford, Richmond Road, Bradford, West Yorkshire, United Kingdom. e.garamendi2@bradford.ac.uk
PURPOSE: To measure quality of life (QoL) outcome in prepresbyopic myopic patients having laser in situ keratomileusis (LASIK) refractive surgery using the Quality of Life Impact of Refractive Correction (QIRC) questionnaire and to compare the QoL of preoperative patients with a sample of spectacle and contact lens wearers not considering refractive surgery.
SETTING: Department of Optometry, University of Bradford, Bradford, and Ultralase, Leeds, West Yorkshire, United Kingdom.
METHODS: The validated QIRC questionnaire was prospectively completed by 66 patients before and 3 months after LASIK. Patients had myopia greater than 0.50 diopters (D) (range --0.75 to --10.50 D) and were aged 16 to 39 years. Patients were also directly asked to evaluate their QoL after surgery.
RESULTS: Overall QIRC scores improved after LASIK from a mean of 40.07+/- 4.30 (SD) to 53.09+/- 5.25 (F(1,130)=172.65, P<.001). Greater improvements occurred in women (53.83+/- 5.46) than in men (49.39+/- 5.94; F(1,64)=9.37, P<.005). Overall, 15 of the 20 questions (especially convenience, health concerns, and well-being questions) showed significantly improved scores (P<.05). Patients who "strongly agreed" (53.96+/- 4.91, n=33) or "agreed" (51.78+/- 6.19, n=23) had improved QoL and had significantly higher QIRC scores than those who "neither agreed nor disagreed" (44.36+/- 4.97, n=5) or "strongly disagreed" (42.82, n=1) (F(1,60)=11.24, P<.001). The matched group not contemplating LASIK scored 42.41 +/- 3.89 on QIRC overall.
CONCLUSIONS: Large improvements in QIRC QoL scores were found after LASIK for myopia in the majority of patients, with greater improvements in women. A small number of patients (4.5%) had decreased QIRC QoL scores, and these were associated with complications. People presenting for LASIK scored measurably poorer than matched patients not contemplating refractive surgery.
"the optical zone was at least 6.0 mm, increased to 0.5 mm greater than the scotopic pupil for pupils over 5.5 mm".
"... other factors, such as the Hawthorne effect and cognitive dissonance, should be considered. Participating in a clinical trial or study can make patients report a significant positive effect of the surgery due to the added attention being made toward them (the Hawthorne effect)."
"Cognitive dissonance states that a change in attitude or belief occurs in an attempt to be consistent with the choice taken. Patients who have chosen to have surgery could justify this choice by indicating that the outcome was successful".
http://www.fda.gov/foi/warning_letters/g5316d.htm
RETURN RECEIPT REQUESTED
FLA-05-27
Dear Mr. Woodrell :
The above-stated inspection revealed that this device is adulterated under section 501(h) of the Act, in that the methods used in, or the facilities or controls used for, the manufacture, packing, storage, or installation are not in conformance with the Current Good Manufacturing Practice (CGMP) requirements for medical devices which are set forth in the Quality System regulation, as specified in Title 21, Code of Federal Regulations (CFR), Part 820. Significant deviations include, but are not limited to, the following:
Data downloaded from LADARVision systems currently in use in the U.S. showed significant differences in the retreatment requirements between patients treated prior to 15 minutes after calibration of the device as opposed to patients who were treated after 15 minutes following calibration of the device. Another table was provided that used the points of < 30 minutes from calibration to treatment and > 30 minutes or more from calibration to treatment.
Your response to this data has been inadequate. There is a note to a warning to the device user manual, which states, "WARNING: System calibration must be done between patients and within 15 minutes of surgery, failure to perform calibration in the time frame indicated may result in improper orientation of the ablation. " However, there was no reason provided to explain the use of these times. Moreover, the note to warning is not by itself sufficient to address the seriousness of this problem . (FDA 483, Item #1)
Class code - 801: Laser not firing,
Class code - 802A: Loss of tracking, and
Complaint records associated with these complaint class codes are not adequately reviewed, evaluated, and investigated to determine the root-cause of the system and/or sub-assembly component malfunction (FDA 483, Item #2).
a . Complaint Record RS030392 received on April 14, 2003, involving the LADARVision® 4000 Beta, lot number L4B1023S references the laser stopped firing during surgery at 92% complete. The Field Service Engineer (FSE) found arcing in the laser chassis assembly. The FSE adjusted components to prevent future arcing. The complaint record does not document and confirm that an investigation was conducted to determine the root cause of the reported problem. The record also fails to document the justification for not conducting an investigation and is not signed and dated by responsible personnel.
c. Complaint Record RS041047 received on August 11, 2004, involving a refurbished LADARVision® 4000 Beta, lot number L4B1090S referencing noise from the laser with a system failed error message. A similar complaint, RS030392 referenced a malfunctioning translator, which was replaced because of faulty/defective bearings. The complaint was classified as complaint class 823- Noise Coming from system. The complaint was more appropriately determined a translator malfunction, which is complaint class 833. The malfunction causes the laser to stop operating or firing resulting in surgery being terminated, causing under correction, which is not considered by your firm to be an injury.
e. Complaint Record RS031262 received on November 14, 2003, involving LADARVision® 4000 Beta, lot number L4B1022S references a laser unable to track. The FSE confirmed the failure mode and replaced the zoom motor. The Manufacturing Engineer (ME) confirmed that the motor performed erratically when operating under a torque and will not reverse direction when prompted by software. A similar complaint FS030539 (noted above) does not document that an investigation was conducted to determine the root cause for the zoom motor failure or the justification for not conducting an investigation into the malfunction.
4. Failure to establish and maintain procedures that define the responsibility for review and the authority for the disposition of nonconforming product as required by 21 CFR 820.90(b)(1). (FDA 483, Item #4). Your own procedures, specifically, SOP 7501-00.38, Field Returns, and SOP 7003-0909, Evaluation of Non-Conforming Parts Returned from Field Service, are not followed:
b. Complaint Record RS040031 - Per the referenced SOPs gas filters were not returned for evaluation and an evaluation was not performed. This report was evaluated by Product Safety (PS) and classified as a "Malfunction". Personnel experienced headache, dry tight throat, and nausea resulting in an emergency room (ER) visit.
The above-stated inspection also revealed that your device is misbranded under section 502(t)(2) of the Act, in that your firm failed or refused to furnish any material or information required by or under section 519 respecting the device. Specifically, your firm failed to report within 30 days whenever the manufacturer receives or otherwise becomes aware of information, from any sources, that reasonably suggests that a device marketed by the manufacturer has caused or contributed to a death or serious injury, as required by 21 CFR 803.50(a)(1).
a. Complaint Record RS041329
Your firm also failed to investigate adverse event reports and to evaluate the cause of the reported event as required by 21 CFR 803.50(b)(2). The following adverse event reports have
