María José Cosentino

Corneal ectasia after laser in situ keratomileusis

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.

Intraocular lens power calculation after refractive surgery

Purpose: To analyze the results of phacoemulsification cataract surgery in eyes that had had refractive surgery and to compare the predictability of various methods of intraocular lens (IOL) power calculation. Setting: Instituto de la Visión, Buenos Aires, Argentina. Methods: The study involved 7 cases that had phacoemulsification after radial keratotomy or laser in situ keratomileusis. The spherical equivalent (SE) and visual acuity were evaluated preoperatively and postoperatively to assess the changes before cataract development. The IOL power calculated with conventional keratometry (CK), adjusted keratometry, the clinical history method (CHM), corneal topography (CT), and the contact lens method (CLM) was compared with the final refractive and keratometric results measured with the BackCalcs (Holladay® IOL Consultant Program, Holladay Consulting, Inc.) to assess the accuracy and predictability of each method. Results: The mean SE was –4.82 diopters (D) ± 5.13 (SD) before phacoemulsification and +0.19 ± 1.01 D after phacoemulsification, and the mean best corrected visual acuity was 0.39 ± 0.07 (20/50) and 0.80 ± 0.06 (20/25), respectively. Conclusions: Post‐phacoemulsification refraction in cases with previous refractive surgery appeared to be predictable when the appropriate calculation method was applied. When all the data were available, the CHM provided the best results. Adjusted keratometry and CT seemed to be more accurate than CK and the CLM.

Laser in situ keratomileusis for hyperopia.

Purpose: To evaluate the results of laser in situ keratomileusis (LASIK) to treat hyperopia. Setting: Instituto de la Visión, Buenos Aires, Argentina. Methods: This nonrandomized study comprised 679 eyes of 321 patients having LASIK. Patients were divided into three groups based on preoperative spherical equivalent: Group A (low hyperopia, 2.00 diopters [D] or less); Group B (moderate hyperopia, between 2.00 and 3.00 D); Group C (high hyperopia, more than 3.00 D). The following were measured postoperatively: uncorrected visual acuity (UCVA); best spectacle‐corrected visual acuity (BSCVA); refraction (evolution and distribution); lines of visual acuity gained and lost. Follow‐up was 1 month in 79.4% of cases, 3 months in 75.5%, 6 months in 68.5%, and 1 year in 38.3%. Results: Six months after LASIK, 100% of cases in Group A, 95.3% in Group B, and 71.4% in Group C were within ± 1.00 D of emmetropia; UCVA was 20/40 or better in 94.1, 100, and 87.8%, respectively. The percentage losing or gaining 0 ± 1 line of BSCVA was 100, 97.6, and 100, respectively. Conclusions: Laser in situ keratomileusis was predictable and safe in the treatment of low and moderate hyperopia.

Comparison of laser epithelial keratomileusis with and without the use of mitomycin C.

PURPOSE To analyze the results of prophylactic intraoperative use of mitomycin C (MMC) in laser epithelial keratomileusis (LASEK). METHODS A retrospective analysis of 30 LASEK cases that received MMC 0.02% intraoperatively (MMC group) was performed and compared to the results obtained in 28 LASEK cases not receiving MMC (no MMC group). Mitomycin C was placed in contact with the ablation zone for 75 seconds with an imbibed microsponge. Both groups received postoperative fluorometholone for 3 months. Preoperative spherical equivalent refraction was -5.72 +/- 2.82 diopters (D) in the MMC group and -5.81 +/- 2.74 D in the no MMC group. Best spectacle-corrected visual acuity was 0.88 +/- 0.12 in the MMC group and 0.88 +/- 0.13 in the no MMC group. RESULTS Spherical equivalent refraction at 6 months postoperatively was +0.11 +/- 0.13 D in the MMC group and +0.09 +/- 0.37 D in the no MMC group. Best spectacle-corrected visual acuity was 0.90 +/- 0.13 in the MMC group and 0.88 +/- 0.13 in the no MMC group. Uncorrected visual acuity (UCVA) > or = 20/40 was obtained in 93.3% of cases in the MMC group and in 89.3% of cases in the no MMC group; UCVA > or = 20/25 was achieved in 76.6% of cases in the MMC group and in 71.4% of cases in the no MMC group. Haze incidence for the MMC group was: trace: 0%, Grades I: 0%, II: 0%, III 0%, IV: 0%, and for the no MMC group: trace: 17.9%, Grades I: 3.6%, II: 0%, III: 0%, IV: 0%. A statistically significant difference (P<.001) was noted in haze intensity between the MMC group and no MMC group. CONCLUSIONS Prophylactic use of intraoperative MMC in LASEK significantly decreases haze incidence.

Treatment of hyperopic astigmatism

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.

Comparison of optical zones in hyperopic laser in situ keratomileusis: 5.9 mm versus smaller optical zones.

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.

Treatment of advanced acanthamoeba keratitis with deep lamellar keratectomy and conjunctival flap.

Purpose. To describe whether deep lamellar keratectomy with a conjunctival flap is effective for the treatment of Acanthamoeba keratitis. Methods. Two patients (three eyes) had at least a 4-week history of painful keratitis misdiagnosed as herpetic keratitis and bacterial keratitis. Both patients were started on multiple topical antiamoebic drugs after Acanthamoeba infection was confirmed. No improvement was observed after 3–4 weeks. Surgery was then performed. Peribulbar anesthesia was given, and the infected tissue was removed by deep lamellar keratectomy. A bipediculate conjunctival flap was put in place and secured with interrupted 10–0 nylon sutures. Results. Both patients experienced immediate pain relief. The infection was controlled and all medications were tapered. There were neither necrosis nor retraction of the flap. Final examination revealed a Best-corrected visual acuity (BCVA) of 20/100 in each eye in the patient described in case number one at 30 months, and 20/100 in the patient described in case number two at 13 months. Conclusion. Deep lamellar keratectomy with a conjunctival flap is a suitable approach to help control the infection and to help relieve pain in patients with advanced Acanthamoeba keratitis.

Laser in situ keratomileusis versus arcuatekeratotomy to treat astigmatism

Abstract Purpose: To analyze the effectiveness of laser in situ keratomileusis (LASIK) andarcuate keratotomy (AK) to treat simple myopic, compound myopic, and mixed astigmatism. Setting: Instituto de la Vision, 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 cylinders 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 aeuities 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.

Intraocular Pressure Measurement Following Hyperopic LASIK

We are responding to the recent article dealing with variations in Goldmann tonometry in myopia but without reference to hyperopia. 1 Our aim is to calculate the variations observed between preoperative and postoperative intraocular pressure (lOP) measurements with Goldmann applanation tonometry following a refractive procedure such as hyperopic laser in situ keratomilensis (LASIK). Two hundred forty-eight hyperopic cases operated on at the same refractive center were examined preoperatively. In all cases, the surgical technique used to treat hyperopia was LASIK. Keratomileusis was performed with Chiron microkeratome models 600, 657, 694, and 1005. Hyperopia and hyperopic astigmatism were ablated with the Technolas Keracor 116/117 excimer laser (Chiron). This population of hyperopic cases was divided into three groups according to the amount of hyperopia: low hyperopia (:52.0 diopters [0]), moderate hyperopia (between 2.0 and 3.0 0), and high hyperopia (2:3.0 0). Of the total cases, 76 (30.7%) were under 40 years of age and 172 (69.3%), over this age; 96 (38.7%) were men and 152 (61.3%), women. The low hyperopia group consisted of 74 cases. Mean refraction was + 1.28 ± 0.85 0, uncorrected visual acuity, 8.89 ± 0.19, and lOP readings, 13.50 mm Hg ± 3.18. The moderate hyperopia group comprised 82 cases. Mean refraction was + 2.51 ± 0.36, uncorrected visual acuity, 0.28 ± 0.11, and best corrected visual acuity, 0.92 ± 0.26. The lOP readings were 14.46 mm Hg ± 1.69. The high hyperopia group comprised 92 cases. Mean refraction was +5.05 ± 0.77, uncorrected visual acuity, 0.13 ± 0.18, and best corrected visual acuity 0.84 ± 0.21. The lOP readings were 14.59 mm Hg ± 1.99. In all cases, lOP was measured with applanation tonometry preoperatively and at 1 week, 1, 3, and 6 months, and 1 year postoperatively. No exclusion criteria were used for the analysis of the sample of postoperative lOP readings. One year after surgery, mean lOP readings were 13.98 mm Hg ± 1.58 in the low hyperopia group, 14.88 mm Hg ± 3.19 in the moderate hyperopia group, and 16.08 mm Hg ± 1.62 in the high hyperopia group. In our opinion, the correction factor for each hyperopia group should be as follows: Low and moderate hyperopia (:53.0 0): 0.5 High hyperopia (2:3.0 0): 1.5 Knowledge of these correction factors is critical for periodic lOP monitoring in patients treated with this surgical technique, particularly those with associated glaucomatous pathology.

Smoothness of ablation on acrylic by four different excimer lasers.

PURPOSE There are many different excimer laser devices available for photoablative refractive surgery. Smoothness of ablation may vary with different excimer lasers systems. METHODS Ablations were performed on polymethylmethacrylate (PMMA) plates of 8 x 4 x 0.5 cm, with four different excimer lasers: VISX-Star, Coherent Schwind Keratom I/II, Chiron Technolas Keracor 117C (Plano Scan), and the Nidek EC-5000, to determine and compare the homogeneity and smoothness of the surface. Ten -3.00 D samples, ten -6.00 D samples, and ten -9.00 D samples were ablated with each laser. The PMMA discs were examined with optical microscopy, documented by photographs, and each sample was measured quantitatively using a Hommel-Werkel rugosimeter. We used the same PMMA material throughout. RESULTS Statistically significant differences in smoothness were found between the Chiron Technolas 117C and the VISX-Star, Nidek and VISX-Star, and Coherent Schwind and VISX-Star in the homogeneities achieved by ablating -3.00 D. Ablations of -6.00 D resulted in homogeneities that were statistically significantly different: Chiron Technolas 117C with the other three devices, the Nidek EC-5000 with the VISX-Star, and the Coherent-Schwind with the VISX-Star. In the ablations for -9.00 D, statistically significant differences in homogeneity were found between the Chiron Technolas 117C and Nidek, between the Chiron and VISX-Star, between the Coherent Schwind and VISX-Star, and between the Nidek and VISX-Star. The laser with the scanning spot system was smoother. CONCLUSION Scanning spot technology produced smooth ablations even up to -9.00 D.