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Purpose: To describe 7 patients who developed ectasia following laser in situ kerato-mileusis (LASIK)., Setting: Instituto de la Visión, Buenos Aires, Argentina., Methods: In this retrospective study of 7 patients, visual acuity, refraction, pachymetry, and corneal topography were examined before and after the refractive procedure and the occurrence of ectasia., Results: Two of the 7 patients required penetrating keratoplasty. Ectasia developed within a mean of 1.02 years +/- 0.31 (SD). The clinical evolution of ectasia and the potential physiopathogenic causes of ectasia are described., Conclusion: Ectasia should be considered a potential complication of LASIK that is closely related to corneal thickness, but another variable, the optical zone diameter, should also be considered.

Purpose: To evaluate laser in situ keratomileusis (LASIK) cases in which a customized ablation assisted by corneal topography was performed., Setting: Instituto de la Visión, Buenos Aires, Argentina., Methods: The study group comprised 23 cases with asymmetrical corneas; 17 had myopia and 6, hyperopia. Visual acuity, spherical equivalent (SE), and cylinder vectorial change measurements, along with keratometry and corneal topography, were performed in all cases preoperatively and postoperatively., Results: In the myopic cases, the mean preoperative SE was -4.92 diopters (D) +/- 2.46 (SD); it was -0.38 +/- 0.66 D after a mean follow-up of 4.41 +/- 2.32 months. In the hyperopic cases, the preoperative SE was +3.54 +/- 1.57 D; it was +0.33 +/- 0.50 D after a mean follow-up of 3.42 +/- 3.23 months. Cylinder vectorial change, visual acuity, and the number of visual acuity lines gained or lost were also evaluated in both groups., Conclusion: Although some features of our algorithm for corneal-topography-assisted customized ablations should be modified, the results of our treatment of cases with asymmetrical astigmatism were encouraging.

Purpose: To compare the results of hyperopic laser in situ keratomileusis (LASIK) with a 5.9 mm optical zone (OZ) with those with smaller zones (4.4 to 5.5 mm)., Setting: Instituto de la Visión, Buenos Aires, Argentina., Methods: The results of LASIK with a 5.9 mm OZ (147 cases) were compared with those in a previously reported group treated with OZs of 4.4 to 5.5 mm (679 cases). In the 5.9 mm group, 31.3% (46 eyes) had low hyperopia, 46.9% (69 eyes) had moderate hyperopia, and 21.8% (32 eyes) had high hyperopia. In the smaller OZ group, follow-up was 1 month in 79.4% (539 eyes), 3 months in 75.5% (501 eyes), 6 months in 68.5% (465 eyes), and 1 year in 38.3% (260 eyes). The hyperopic population studied was divided into 3 subgroups based on the preoperative spherical equivalents of the manifest refraction: subgroup A, low hyperopia: < or = +2.0 diopters (D); subgroup B, moderate hyperopia: +2.0 to +3.0 D; and subgroup C, high hyperopia: > +3.0 D. The following parameters were measured postoperatively: uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), refraction (evolution and distribution), and visual acuity lines gained and lost., Results: The preoperative mean spherical equivalents in the 5.9 mm OZ group were +1.47 +/- 0.41 (SD) (subgroup A); +2.98 +/- 0.41 (subgroup B); and +5.13 +/- 0.61 (subgroup C). In the smaller OZ group, they were +1.31 +/- 0.74, +2.56 +/- 0.28, and +5.28 +/- 0. 69, respectively. At 12 months, the distribution of eyes in the 5.9 mm OZ group with refractions within +/-1.0 D were as follows: subgroup A, 100%; subgroup B, 100%; and subgroup C, 94.2%. In the smaller OZ group, the distributions were 100%, 95.3%, and 71.4%. In the 5.9 mm and the smaller OZ groups, the UCVA was 20/40 or better in 92.0% and 81.8% of eyes, respectively, in subgroup A; 94.6% and 100%, respectively, in subgroup B; and 76.5% and 77.9%, respectively, in subgroup C. The percentage of eyes with 0 +/- 1 line of BCVA 12 months after the procedure was also determined in the 5.9 mm OZ group and compared with the percentages in the smaller OZ group., Conclusion: Results of hyperopic LASIK with a 5.9 mm OZ in eyes with low, moderate, and high hyperopia are more stable, predictable, and safe than those in eyes with OZs smaller than 5.9 mm.

Purpose: To analyze the effectiveness of laser in situ keratomileusis (LASIK) and arcuate keratotomy (AK) to treat simple myopic, compound myopic, and mixed astigmatism., Setting: Instituto de la Visión, Buenos Aires, Argentina., Methods: This retrospective nonrandomized study comprised 821 cases treated with LASIK and 46 cases treated with AK. Patients were divided into 4 groups, which had the following preoperative cylinder corrections: simple myopic astigmatism (Group 1) (LASIK: n = 76, -3.91 diopters [D] +/- 1.29 [SD]; AK: n = 5, -3.85 +/- 0.65 D); compound myopic astigmatism up to 2.00 D (Group 2) (LASIK: n = 401, -1.69 +/- 0.76 D; AK: n = 14, -1.48 +/- 0.41 D); compound myopic astigmatism over 2.00 D (Group 3) (LASIK: n = 253, -3.61 +/- 0.89 D; AK: n = 16, -3.09 +/- 0.84 D); mixed astigmatism (Group 4) (LASIK: n = 91, +3.65 +/- 1.62 D; AK: n = 11, 4.39 +/- 0.92 D)., Results: Six months postoperatively, the cylinder's vector-corrected change was as follows: Group 1, LASIK 3.75 +/- 1.08 D, AK 3.16 +/- 0.84 D; Group 2, LASIK 1.55 +/- 1.12 D, AK 1.34 +/- 0.44 D; Group 3, LASIK 3.39 +/- 0.98 D, AK 2.70 +/- 1.21 D; Group 4, LASIK 3.77 +/- 1.43 D, AK 3.75 +/- 0.89 D. Respective mean uncorrected visual acuities in each group were as follows: Group 1, 0.71 +/- 0.12 and 0.60 +/- 0.12; Group 2, 0.83 +/- 0.12 and 0.78 +/- 0.24; Group 3, 0.78 +/- 0.18 and 0.48 +/- 0.24; Group 4, 0.69 +/- 0.21 and 0.55 +/- 0.18., Conclusions: The vector-corrected change and visual acuity achieved with LASIK were better, although not significantly, than those attained with AK except for the UCVA obtained with LASIK in eyes with compound myopic astigmatism over 2.00 D. Both methods proved to be safe.

Purpose: To analyze the results after laser-assisted in situ keratomileusis (LASIK) treatment for positive cylinder at the flattest meridian., Setting: Instituto de la Visión, Buenos Aires, Argentina., Methods: A prospective, nonrandomized study was conducted. Patients were divided into three groups: (1) simple hyperopic astigmatism (SHA); 15 eyes with a mean preoperative cylinder of +3.37 diopters (D) +/- 1.62 (SD); compound hyperopic astigmatism (CHA); 75 eyes with a mean preoperative cylinder of +3.34 +/- 1.39 D; (3) mixed astigmatism (MA); 73 eyes with a mean preoperative cylinder of +3.45 +/- 2.15 D. In all eyes, treatment of the cylinder was performed at the flattest meridian by LASIK using the Chiron-Technolas Keracor 116/117 laser. The following parameters were analyzed over time: uncorrected visual acuity; best corrected visual acuity; correction of the spherical equivalent and the cylinder; lines of visual acuity gained and lost., Results: Six months after the procedure, refractive cylinder was reduced to +0.58 +/- 1.22 D in the SHA group, +0.12 +/- 1.23 D in the CHA group, and -0.11 +/- 1.28 D in the MA group. Uncorrected visual acuities were 20/20 or 20/25 in 66.7, 60.4, and 76.5% of the groups, respectively., Conclusions: Use of the LASIK technique with the Keracor laser to treat positive cylinder at the flattest meridian corrected simple and compound hyperopic astigmatism and mixed astigmatism with good predictability and safety. This treatment has not produced a hyperopic refractive change at the opposite meridian.