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Friday, November 11, 2011
Saturday, February 3, 2007
Post-laser in-situ keratomileusis ectasia: current understanding and future directions.
- Randleman JB.
Emory University Department of Ophthalmology and Emory Vision, Atlanta, Georgia 30322, USA. Jrandle@emory.edu
PURPOSE OF REVIEW: The aim of this article is to review the causes, risk factors, management, and future research directions for corneal ectasia after laser in situ keratomileusis. RECENT FINDINGS: Complex corneal biomechanical processes influence the integrity of the normal and postoperative cornea, and developing an understanding of these processes facilitates recognition of risk factors for ectasia after laser in-situ keratomileusis. Currently identified risk factors include keratoconus, high myopia, low residual stromal bed thickness from excessive ablation or thick flap creation, and defined topographic abnormalities such as forme fruste keratoconus and pellucid marginal corneal degeneration. Ectasia can also rarely occur in patients without currently identifiable risk factors, and future identification of at-risk patients may be facilitated by corneal interferometry and corneal hysteresis measurements. Utilization of intraoperative pachymetry measurements at the time of surgery and confocal microscopy prior to enhancement to measure residual stromal bed thickness should avoid unanticipated low residual stromal bed thickness. Management options for ectasia after laser in situ keratomileusis include intraocular pressure reduction, rigid gas permeable contact lenses, and intracorneal ring segments, in addition to corneal transplantation. In the future, collagen cross-linking may reduce corneal steepening and improve refractive error. SUMMARY: When ectasia develops, early recognition and proper management are essential to prevent progression, to promote visual rehabilitation, and to reduce the need for corneal transplantation for these patients.
PMID: 16900036 [PubMed - in process]
Tuesday, January 30, 2007
Customized LASIK treatment for myopia: relationship between preoperative higher order aberrations and refractive outcome.
J Refract Surg. 2006 Oct;22(8):746-53.
University of Rochester, Rochester, NY, USA. venkitms@bausch.com
PURPOSE: To analyze the effect of preoperative higher order aberrations on postoperative sphere and cylinder outcome. METHODS: Three hundred thirty myopic eyes (mean: -3.32 +/- 1.54 diopters [D], range: -1.0 to -7.0 D) treated with customized ablation using the Technolas 217z laser (Bausch & Lomb) were followed through 6 months after LASIK. Pre- and postoperative visual acuity, higher order root mean square (RMS), third order RMS, and spherical aberration were compared to study the safety and efficacy of the treatment. The relationship between preoperative higher order aberrations and manifest refraction after LASIK was analyzed. RESULTS: Following LASIK, 91.5% of eyes obtained an uncorrected visual acuity of > or = 20/20 and 70.3% of eyes obtained 20/16 without retreatment; 99% had a best spectacle-corrected visual acuity of > or = 20/20 (75.9% of eyes were within +/- 0.50 D). Mean value of significant increase in postoperative higher order aberrations was 0.12 +/- 0.18 microm (P<.0001). Increased spherical aberration was associated with increased myopia treatment (P<.0001). Greater positive spherical aberration after LASIK was significantly correlated to postoperative hyperopia (overcorrection). Change in third order RMS was significantly correlated to change in spherical equivalent refraction among eyes with postoperative astigmatism (P<.0001). CONCLUSIONS: With the Bausch & Lomb Technolas 217z Zyoptix software, treatment of higher order aberrations, especially third order (coma and trefoil) and spherical aberration, significantly improved postoperative refractive status.
PMID: 17061711 [PubMed - indexed for MEDLINE]
Refractive eye surgery in treating functional amblyopia in children.
Binocul Vis Strabismus Q. 2006;21(4):231-4.
Saclker School of Medicine, Tel Aviv University, Kfar Saba, Israel.
PURPOSE: While excimer laser refractive surgery is recommended and highly successful for correcting refractive errors in adults, its use in children has not been extensively exercised or studied. We report our experience treating children with amblyopia due to high anisometropia, high astigmatism, high myopia and with associated developmental delay. SETTING: Review of patient records of our refractive clinic. METHODS: A retrospective review was made of all 11 children with stable refractive errors who were unsuccessfully treated non-surgically and then underwent corneal refractive surgery and in one case, lenticular surgery. Seven had high myopic anisometropia, 2 had high astigmatism, and two had high myopia--one with Down's Syndrome and one with agenesis of the corpus callosum. RESULTS: The surgical refractive treatment eliminated or reduced the anisometropia, reduced the astigmatic error, improved vision and improved the daily function of the children with developmental delay. There were no complications or untoward results. CONCLUSIONS: Refractive surgery is safe and effective in treating children with high myopic anisometropia, high astigmatism, high myopia and developmental delay due to the resulting poor vision. Surgery can improve visual acuity in amblyopia not responding to routine treatment by correcting the refractive error and refractive aberrations.
PMID: 17069560 [PubMed - indexed for MEDLINE]
Femtosecond laser versus mechanical keratome LASIK for myopia.
Ophthalmology. 2007 Jan;114(1):62-8. Epub 2006 Oct 27.
Optics Department, Faculty of Physics, University of Valencia, Valencia, Spain. roberto.montes@uv.es
OBJECTIVE: To assess efficacy, safety, predictability, stability, and changes in corneal higher-order aberrations (CHOAs) and contrast sensitivity (CS) after a femtosecond laser for LASIK and standard LASIK for myopia. DESIGN: Prospective, randomized, comparative clinical study. PARTICIPANTS: Two hundred eyes of 100 consecutive patients who underwent LASIK treatment using the VISX S2 laser system. A femtosecond laser for flap creation was used in 100 eyes (50 patients; spherical equivalent [SE], -2.85+/-1.79 diopters [D]), and a mechanical microkeratome was used in 100 eyes (50 patients; SE, -2.90+/-1.63 D). METHODS: Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, CS by means of the Functional Acuity Contrast Test, and CHOAs by means of custom software linked to topography were evaluated preoperatively and 6 months after treatment. MAIN OUTCOME MEASURES: Efficacy, safety, predictability, stability, CHOAs, and CS were evaluated before and after surgery at 6 months' follow-up. RESULTS: At 6 months postoperatively, UCVA was 1.0 or better in 100% of the eyes. Efficacy indexes were 1.07 for the femtosecond laser for LASIK patients and 1.00 for LASIK patients. No eye lost > or =1 lines of BCVA; for the femtosecond laser for LASIK group, 24 eyes gained 1 line, and 18 eyes gained > or =2 lines; for the LASIK group, 18 eyes gained 1 line. The femtosecond laser for LASIK group showed a percentage of eyes (98%) within the 0.5-D range in SE higher than that of the LASIK group (92%). For a 3.5-mm pupil, CHOAs' root-mean-square (RMS) increased for both the femtosecond laser for LASIK (2.21-fold) and LASIK (2.81-fold) groups. For a 6-mm pupil, CHOA RMSs were increased significantly after femtosecond laser for LASIK (4.18-fold) and LASIK (5.07-fold) surgeries (P<0.01).>
PMID: 17070593 [PubMed - indexed for MEDLINE]
Evidence for superior efficacy and safety of LASIK over photorefractive keratectomy for correction of myopia.
Ophthalmology. 2006 Nov;113(11):1897-908.
Moorfields Eye Hospital, London, United Kingdom. a.shortt@ucl.ac.uk
PURPOSE: To examine possible differences in efficacy and safety between LASIK and photorefractive keratectomy (PRK) for correction of myopia. DESIGN: Meta-analysis/systematic review. PARTICIPANTS: Patient data from previously reported prospective randomized controlled trials (PRCTs) and a systematic review of prospective case series in the Food and Drug Administration (FDA) clinical trials database. METHODS: A comprehensive literature search was performed using the Cochrane Collaboration methodology to identify PRCTs comparing LASIK and PRK for correction of myopia. A meta-analysis was performed on the results of PRCTs. In parallel, a systematic review of prospective data from FDA case series of LASIK and PRK for correction of myopia was undertaken. MAIN OUTCOME MEASURES: Key efficacy outcomes (uncorrected visual acuity [UCVA] > or = 20/20, +/-0.50 diopters [D] of the target mean refractive spherical equivalent) and safety outcomes (loss of > or =2 lines of best spectacle-corrected visual acuity [BSCVA], final BSCVA > or = 20/40, and final BSCVA <> or =20/20). RESULTS: Seven PRCTs were identified comparing PRK (683 eyes) and LASIK (403 eyes) for correction of myopia. More LASIK patients achieved UCVA > or = 20/20 at 6 months (odds ratio, random effects model [95% confidence interval], 1.72 [1.14-2.58]; P = 0.009) and 12 months (1.78 [1.15-2.75], P = 0.01). Loss of > or =2 lines of BSCVA at 6 months was less frequent with LASIK (2.69 [1.01-7.18], P = 0.05). Data from 14 LASIK (7810 eyes) and 10 PRK (4414 eyes) FDA laser approval case series showed that more LASIK patients achieved UCVA of 20/20 or better at 12 months (1.15 [1.03-1.29], P = 0.01), significantly more LASIK patients were within +/-0.50 D of target refraction at 6 months (1.38 [1.26-1.50], P<0.00001) p =" 0.0009)"> or =2 lines of BSCVA at 6 months was less frequent with LASIK (2.91 [2.22-3.83], P<0.00001).> or =5 years ago. It is therefore unclear how our findings relate to present-day methods and outcomes. Further trials comparing contemporary equipment and techniques are needed to reevaluate the relative merits of these procedures.
PMID: 17074559 [PubMed - indexed for MEDLINE]
A control-matched comparison of laser epithelial keratomileusis and laser in situ keratomileusis for low to moderate myopia.
Am J Ophthalmol. 2006 Dec;142(6):901-8. Epub 2006 Sep 8.
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Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA.
PURPOSE: To compare the visual and refractive outcomes of laser epithelial keratomileusis (LASEK) and laser in situ keratomileusis (LASIK) for the treatment of low to moderate myopia. DESIGN: Retrospective, nonrandomized, control-matched study. METHODS: The charts of 2257 eyes that underwent LASEK or LASIK treatment were reviewed. Patients who were 21 years of age or older having between -0.75 and -6.00 diopters (D) of myopia with up to -2.25 D of astigmatism were included. One hundred twenty-two LASEK-treated eyes were matched with 122 LASIK-treated eyes having preoperative spheres, cylinders, and spherical equivalent (SE) within +/-0.50 D. Both groups had similar preoperative best spectacle-corrected visual acuity (BSCVA), laser platform, and follow-up durations. Outcome measures were visual and refractive results. RESULTS: Preoperatively, the mean SE was -3.50 +/- 1.40 D for LASEK and -3.50 +/- 1.42 D for LASIK (P = .59). Postoperatively, the mean logarithm of minimum angle of resolution (logMAR) uncorrected visual acuity (UCVA) was 0.01 +/- 0.08 (20/21) for LASEK and 0.06 +/- 0.12 (20/23) for LASIK; the mean SE was -0.15 +/- 0.40 D for LASEK and -0.37 +/- 0.45 D for LASIK; and the mean logMAR of BSCVA was -0.03 +/- 0.06 (20/19) for LASEK and -0.02 +/- 0.05 (20/19) for LASIK. No eye lost 2 or more lines of BSCVA in both groups. CONCLUSIONS: Slight differences in the visual and refractive results between LASEK and LASIK were observed, despite the use of the same nomogram. Both procedures were safe, effective, and predictable. Nomogram adjustment may be necessary for LASIK surgeons adopting surface ablation.
PMID: 17157575 [PubMed - indexed for MEDLINE]
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