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PubMed2004

[Influence of incision parameters on astigmatism during implantation of phakic-6-mm-iris-claw intraocular lenses].

BACKGROUND: The implantation of a phakic 6-mm-iris-claw intraocular lens requires a 6.1-6.2 mm incision. This induces a variable amount of corneal astigmatism depending on the location and the type of the incision used. The aim of the current study is to investigate the surgically induced astigmatism (SIA) of different incision types and locations. This should help to achieve nearly spherical postoperative refraction. PATIENTS AND METHOD: 28 eyes of 16 patients with a 1-year follow-up after an implantation of a 6-mm-non-foldable iris-claw phakic IOL were studied. 5 different incision techniques were used. These were a superior corneal incision alone (8 eyes) or in combination with a 60 degrees limbal relaxing incision (LRI) at the same axis (8 eyes), a superior sclerocorneal tunnel incision (6 eyes) and the two-incisional approach either with a sclerocorneal (4 eyes) or a pure corneal (2 eyes) main temporal incision. The SIA was calculated for each incision used. RESULTS: The superior corneal incision had a mean SIA of 1.2 D cyl. This SIA was enhanced by an opposite LRI by another 1 D cyl. The sclerocorneal tunnel induced 0.75 D cyl, while the two-incisional techniques delivered nearly astigmatismus neutral results. CONCLUSION: A proper selection of an appropriate incision site and type allows to correct the preexisting astigmatism or to keep a spherical refraction after an implantation of a 6-mm-rigid phakic iris-claw IOL.

Adult↗
PubMed2005

[LASEK: results after 1 year. Retrospective analysis based on the dioptric power matrix for moderate myopic and astigmatic correction].

PURPOSE: The aim of this study was to assess astigmatism magnitude and axis changes based on the dioptric power matrix in low to moderate levels of myopia and astigmatism treated with LASEK. PATIENTS AND METHODS: This retrospective analysis included 54 myopic eyes treated with LASEK with a minimum follow-up of 12 months. An epithelial flap was created by 25-45 s of 20% alcohol exposure. The corneal surface was ablated using two different excimer lasers and nomogram adjustment. The flap was repositioned and a bandage applied to the contact lens. Main outcome measures were manifest refraction as calculated with the dioptric power matrix, UCVA, BSVCA, and retreatment rate. RESULTS: Mean manifest refraction is shown in table 2 (Tabelle 2). UCVAs of 20/20 or better were found in 33% of eyes at 1 week and in more than 53% at 3 months to 1 year. The safety index remained > or =0.98 after postoperative week 4. The efficacy index varied between 0.91 and 0.98 after 1 month. CONCLUSION: LASEK for correction of low to moderate myopia and astigmatism seems to be a safe, effective, and stable option.

Astigmatism↗
PubMed2002

[Implantation of toric intraocular lenses for correction of high post-keratoplasty astigmatism].

BACKGROUND: High postkeratoplasty astigmatism remains a challenge for the surgeon. First experiences after implantation of a toric PMMA IOL in three eyes from patients with cataracts are reported. MATERIALS AND METHODS: After routine phacoemulsification we implanted an individually manufactured toric PMMA posterior chamber IOL via a sclerocorneal 6-mm tunnel incision in three postkeratoplasty eyes with high, topographically relatively regular astigmatism. One eye with the intraoperative aspect of circular zonular instability also received a capsular tension ring. A complete standard ocular examination was performed pre- and postoperatively including corneal topography, evaluation of anterior chamber depth, ultrasonic biomicroscopy and perimetry. RESULTS: Implantation and intraoperative alignment of the toric IOL were uneventful. The refractive astigmatisms of 5.0, 6.0 and 7.5 cyl D preoperatively, were reduced to 2.0, 1.75 and 3.0 cyl D, 10 and 12 months postoperation, respectively. The eye with the capsular tension ring showed no morphological or refractive changes during follow-up. In the other two eyes we observed IOL rotation of 20 and 30, respectively after 6 months. There were no posterior capsule opacification or capsular folds in the optical centre. CONCLUSION: Toric IOL technology allows enhancement of IOL surgery with improved refractive outcome. Simultaneous implantation of a capsular tension ring may improve long-term stability.

Aged↗
PubMed1998

Holmium:YAG thermokeratoplasty: treatment parameters for astigmatism induction based upon spherical enucleated human eyes.

BACKGROUND: The refractive outcome of thermokeratoplasty for astigmatism correction depends upon the optical zone diameter (OZD) and coagulation angle (CA; distance between two coagulation spots around the flat meridian). METHODS: Astigmatism was induced in 36 spherical human eye-bank eyes (Ho:YAG laser, 15 Hz, 20 mJ/pulse, 25 pulses per coagulation spot) with different OZDs and CAs. Thirty eyes received free-hand laser application (marked positions). Six eyes were treated using a suction mask, providing a constant OZD of 8.1 mm and an angle of 22.5 degrees between the laser spots. To compare the results, silicone replicas of the eyes were made pre- and postoperatively and analyzed by video-topometery. RESULTS: With an average decrease of 4 D/mm the refractive change is inversely linear to the OZD. Changes of the CA showed significant variations between 22.5 degrees and 45 degrees, only. Mask guidance leads to the same amount of average refractive change. The deviation is +/- 3.4 D for the freehand application but only +/- 0.8 D for mask guidance. CONCLUSION: The data obtained in this in vitro study are transferred to a treatment nomogram describing the immediate postoperative refractive change, not identical with the final refraction. The results of the study are limited by the fact that astigmatism was induced in spherical corneas, rather than correcting preexisting ones.

Astigmatism↗
PubMed1985

Infant astigmatism and meridional amblyopia.

The orientation preferences of 70 infants aged 7 to 53 weeks with significant astigmatism [1.0 or more diopters (D)] were measured using a preferential looking procedure with paired gratings. The preference data show the consequences of the blurring effects of astigmatism when these are not compensatable by accommodation. Data from infant astigmats tested with optical correction look like those of nonastigmats. We have found no evidence for the development of meridional amblyopia during the first year of life.

Accommodation, Ocular↗
PubMed2005

Comparison of two techniques of marking the horizontal axis during excimer laser keratorefractive surgery for myopic astigmatism.

PURPOSE: To compare two methods of limbal marking used during laser refractive surgery for myopic astigmatism. DESIGN: Retrospective chart review. METHODS: Forty-two eyes of 42 patients who underwent photorefractive keratectomy (PRK) or laser-assisted in-situ keratomileusis (LASIK) for myopic astigmatism were marked preoperatively to identify the horizontal axis. In 18 eyes, marks were placed at the slit lamp (SL) with the slit beam set at 180 degrees as a reference. In 24 eyes, marks were placed in the laser room (LR) immediately before reclining under the laser. All treatments were performed with the Alcon LADARVision excimer laser system. Vector analysis of postoperative cylinder and reduction in cylinder and uncorrected and best-corrected visual acuity were evaluated for both groups. RESULTS: The mean postoperative magnitude of error was -0.19 +/- 0.44 diopters for the LR group and -0.09 +/- 0.42 diopters for the SL group (P = .439, NS). Both groups had a mean angle of error indicating an overall counterclockwise rotation of axis with an angle of error of 6.3 +/- 8.7 degrees for the LR group and 8.0 +/- 10.2 degrees for the SL group (P = .562, NS). CONCLUSIONS: We found no significant difference in outcomes with an overall trend toward undercorrection of cylinder in both groups, leaving room for improvement after refractive surgery for myopic astigmatism.

Astigmatism↗
PubMed2005

Spontaneous long-term changes of corneal power and astigmatism after suture removal after penetrating keratoplasty using a regression model.

PURPOSE: To assess the diagnosis-based spontaneous long-term changes in corneal power and refraction with a regression model in the all-sutures-out time period following non-mechanical penetrating keratoplasty (PK). DESIGN: Retrospective non-randomized clinical trial. METHODS: setting: Clinical practice. study population: 147 eyes [47 Fuchs dystrophy (FD); 100 keratoconus (KC)] were studied after suture removal in this retrospective longitudinal study. main outcome measures: Zeiss keratometry [equivalent power (KEQ) and astigmatism (KAST)], corneal topography analysis [equivalent power (TEQ) and astigmatism (TAST)], and subjective refractometry [spherical equivalent (SEQ) and refractive cylinder (RAST)] were assessed in at least three up to 16 ophthalmologic examinations in the all-sutures-out time period. observation procedure: The time course of each target variable was analyzed in a longitudinal manner (time interval > or = 12 months) separately for each patient with a linear regression model. RESULTS: Post-keratoplasty follow-up ranged from 31 months to 10.3 years. In the linear regression model, the annual change in FD/KC showed an increase/a decrease in KEQ (0.29 +/- 0.50/-0.63 +/- 0.46 diopters, P = .02) and an increase/a decrease in TEQ (0.37 +/- 0.54/-0.69 +/- 0.49 diopters, P = .04) corresponding to a decrease/an increase in SEQ (-0.31 +/- 0.47/0.63 +/- 0.43 diopters, P = .02). KAST/TAST/RAST showed a minimal annual decrease (-0.06 +/- 0.41/-0.05 +/- 0.45/-0.06 +/- 0.41 diopters) in FD but an increase in KC (0.46 +/- 0.41/0.51 +/- 0.43/0.46 +/- 0.38 diopters) (P = .05/0.06/0.12). CONCLUSIONS: In the follow-up after post-keratoplasty suture removal, patients with FD/KC tend to develop a spontaneous myopic shift (steepening of the cornea)/hyperopic shift (flattening of the cornea). In contrast with those with FD, patients with KC should be counseled on the fact that astigmatism may increase again over time after suture removal.

Astigmatism↗
PubMed2004

Astigmatism after small-incision clear corneal cataract extraction and intraocular lens implantation in children.

PURPOSE: To investigate the magnitude of postoperative astigmatism in children having cataract extraction with intraocular lens (IOL) implantation through a 3.0 mm superior clear corneal incision. SETTING: Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, USA. METHODS: This retrospective chart review comprised all pediatric patients having cataract surgery with IOL implantation through a 3.0 mm clear corneal incision from 1997 to 2002. One hundred two eyes of 75 patients were included. All refractions were performed manually by an experienced pediatric ophthalmologist. RESULTS: The mean postoperative retinoscopic cylinder in all patients was 0.63 diopter (D) (range 0.0 to 4.50 D) at 1 month, 0.40 D (range 0.0 to 1.75 D) at 6 months, and 0.51 D (range 0.0 to 2.50 D) at 1 year. Patients aged 0 to 36 months at the time of surgery had a mean postoperative cylinder of 0.22 D at 1 month, 0.03 D at 6 months, and 0.21 D at 1 year. Patients between 36 months and 6 years of age at surgery had a mean refractive cylinder of 0.50 D, 0.38 D, and 0.75 D, respectively. Patients older than 6 years at surgery had a mean refractive cylinder of 0.94 D, 0.75 D, and 0.76 D, respectively. CONCLUSIONS: Small-incision clear corneal cataract extraction with IOL implantation in children led to minimal postoperative astigmatism that remained stable over time. Less astigmatism was observed in children having surgery before they were 36 months old.

Adolescent↗
PubMed2006

CustomVue laser in situ keratomileusis for myopia and myopic astigmatism using the Visx S4 excimer laser: Efficacy, predictability, and safety.

PURPOSE: To evaluate the efficacy, predictability, and safety of custom laser in situ keratomileusis (LASIK) using the Visx wavefront platform CustomVue for the treatment of myopia and myopic astigmatism. SETTING: Stanford University Eye Laser Center, Stanford, California, USA. METHODS: This retrospective analysis was of the initial 140 eyes of 78 patients treated consecutively with LASIK for myopia using the Visx Star S4 excimer laser. Primary outcome variables, including uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, and complications, were evaluated at 1 week and 1 and 3 months. Vector analysis was performed on eyes that received astigmatic correction. RESULTS: Mean preoperative spherical equivalent (SE) was reduced from -3.89 diopters +/- 1.48 (SD) to an SE of -0.21 +/- 0.36 D at 1 month and -0.28 +/- 0.36 D at 3 months (P < .001). At 1 and 3 months, UCVA was 20/20 or better in 84.3% and 87.9%, respectively. Eighty-six percent of eyes at 1 month and 81.4% of eyes at 3 months were within +/-0.5 D of emmetropia. No eyes lost more than 2 lines of BSCVA. Vector analysis yielded an index of success of 0.39, indicating a 61% success rate in achieving the astigmatic surgical correction at 3 months. The preoperative root-mean-square value of 0.28 +/- 0.08 microm increased slightly to 0.33 +/- 0.11 microm at 1 month and 0.34 +/- 0.11 microm at 3 months. CONCLUSION: Wavefront-guided LASIK using the Visx CustomVue system was effective, predictable, and safe for correction of low to moderate myopic refractive error.

Adult↗
PubMed2006

Topography-guided customized laser-assisted subepithelial keratectomy for the treatment of postkeratoplasty astigmatism.

PURPOSE: To assess topography-assisted corneal wavefront excimer laser surface ablation for the correction of ametropia and irregular astigmatism after keratoplasty. SETTING: Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom. METHODS: In this pilot study, 15 patients (16 eyes) who were intolerant of spectacle and contact lens correction due to astigmatic anisometropia after keratoplasty (15 penetrating and 1 lamellar) had topography-assisted customized excimer laser treatments. Corneal topographic data using a Keratron Scout, Placido disk system allowed for preoperative analysis of wavefront anomalies of the anterior corneal surface from which a customized excimer laser correction of both lower-order aberrations (LOAs) and higher-order aberrations (HOAs) was prepared (ORK software) for treatment with a Schwind Esiris flying-spot laser. All eyes had laser-assisted subepithelial keratectomy (LASEK) using 15% alcohol with a 20-second to 30-second application. Four eyes received an application of mitomycin-C (MMC) 0.2 mg/mL for 1 minute after stromal ablation. RESULTS: The mean preoperative spherical equivalent (SE) was -3.50 diopters (D) +/- 3.97 (SD) (range +1.625 to -9.25 D). The preoperative cylindrical error was -7.2 D (range -2.75 to -13.5 D). The programmed laser correction was -3.14 D (range +1.62 to -9 D) with a maximum attempted cylindrical correction of -7 D. Adherent LASEK epithelial flaps along suture lines and the graft-host junction were noted in 9 eyes (56%), although it was possible to obtain and replace a partial flap. A follow-up of 18 months was achieved in all eyes. At the final follow-up visit, the mean postoperative SE was -1.08 +/- 1.85 D (range +3 to -4.78 D) (P<.01, F<.01). Ten eyes (62.5%) were within +/-1 D of the intended correction. The mean postoperative cylindrical error was -2.72 D (range -0.5 to -6.5 D) (P<.001), with vector analysis demonstrating a mean 6.23 D correction. Analysis of HOAs using a 6.0 mm pupil size demonstrated a significant reduction of higher-order root mean square (RMS) (P<.002), trefoil (P<.005), and 4th-order spherical aberration (P<.02) at 18 months compared with preoperative values. Uncorrected visual acuity improved in all eyes (P<.0001). Best spectacle-corrected visual acuity was unchanged or improved in 13 eyes (81%) and worse in 2 eyes by 1 line; 1 eye lost 3 lines due to an increase in preexisting cataract. In eyes that did not receive MMC, corneal haze (grade II to IV) was encountered in 3 eyes (27%). One eye required phototherapeutic keratectomy with MMC application at 12 months. Of the 4 eyes treated with MMC, 1 had trace haze and 3 had no detectable haze. There were no reported cases of epithelial instability, ectasia, or graft rejection. CONCLUSIONS: Topography-assisted customized LASEK was effective in the correction of postkeratoplasty astigmatism. A significant improvement of both LOAs and HOAs was obtained with good refractive stability for over 18 months. Iatrogenic haze typically occurred but appeared to be minimized with adjunctive use of intraoperative MMC.

Adult↗
PubMed2006

Two-step laser in situ keratomileusis to correct high astigmatism after corneal autograft.

We report a case in which significant anisometropia and astigmatism after an autograft by rotation was treated by a 2-step laser in situ keratomileusis (LASIK) procedure. Six weeks after the lamellar keratotomy, photoablation was performed using the LADARVision 4000 excimer laser. The ablation depth was 87.2 mum on a 6.0 mm optical zone. One day postoperatively, the uncorrected visual acuity (UCVA) was 7/10 and the refractive error was -0.25 -0.25 x 67. Two months later, the UCVA was 5/10 and the best corrected visual acuity, 8/10 Parinaud 2 with a refractive error of +1.75 -1.25 x 16. The case demonstrates the effectiveness of 2-step LASIK for the correction of astigmatism induced by a corneal autograft. The significant reduction in autograft-induced astigmatism, together with stabilization of the higher-order aberrations, resulted in restoration of satisfactory functional vision.

Anisometropia↗
PubMed2006

Astigmatism control.

Refractive cataract surgery has become a reality for the modern phacosurgeon, and control of astigmatism plays a vital role in this quest for optical refractive outcomes. Fortunately, a number of effective options exist to minimize postoperative cylinder. These include placing the cataract incision on the steep corneal meridians; use of adjunctive corneal or limbal relaxing incisions; or even using advanced technology, such as the excimer laser. Careful attention must be directed to the measurement of pre-existing astigmatism, and a detailed surgical strategy must then be formulated. Finally, one must be able to avail themselves of enhancement techniques to address residual astigmatism.

Astigmatism↗
PubMed2004

Wavefront-guided LASIK with the Zyoptix 3.1 system for the correction of myopia and compound myopic astigmatism with 1-year follow-up: clinical outcome and change in higher order aberrations.

OBJECTIVE: To assess safety, efficacy, predictability, stability, and change in aberrations after wavefront-guided LASIK for myopia and myopic astigmatism. DESIGN: Prospective, nonrandomized, self-controlled trial. PARTICIPANTS: Wavefront-guided LASIK was performed in 97 eyes in a 1-year trial. Treated eyes had a mean subjective manifest spherical equivalent (SE) of -5.22+/-2.07 diopters (D), with a range of -0.25 to -9.00 D of myopia and 0 to -3.25 D of astigmatism. INTERVENTION: After a microkeratome cut, a wavefront-based excimer ablation (Zyoptix 3.1) was performed. The full treatment to achieve emmetropia of an early nomogram provided by the system manufacturer was used in all procedures. MAIN OUTCOME MEASURES: Safety, efficacy, predictability, and stability were evaluated at 1, 3, and 12 months postoperatively. Wavefront changes of higher order aberrations (HOAs) at 1 year were determined for pupil sizes of 3.5 and 6 mm. RESULTS: At 1 year postoperatively, uncorrected visual acuity (VA) was 20/20 or better in 83% of the eyes, and 20/40 or better in 98%. The mean subjective manifest SE at 1 year was -0.25+/-0.43 D; it was within 0.50 D in 77% and within 1.0 D in 95%. No eye lost > or =2 lines of best spectacle-corrected VA (BSCVA) at 1 year postoperatively; 40 eyes gained 1 line of BSCVA, and 5 eyes gained 2 lines. The total HOA root mean square (RMS) increased on average by a factor of 1.23+/-0.57 with a 3.5-mm pupil; for the 6 mm pupil, the increase factor was 1.52+/-0.36. No change or reduction in the total HOA RMS was observed in 45.5% of the eyes for a 3.5-mm pupil and in 20.6% for a 6-mm pupil. There was a significant increase of primary spherical aberration (Z 4,0) by a factor of 4.11+/-10.17 for 3.5-mm pupils and 4.31+/-6.76 for 6-mm pupils. CONCLUSIONS: Wavefront-guided LASIK using Zyoptix 3.1 is an effective and safe procedure for the treatment of myopia and myopic astigmatism. Although in close to half of the eyes HOAs could be reduced, there was still undercorrection and induction of HOAs with the algorithm employed.

Adult↗
PubMed2005

Compressive C-shaped lamellar keratoplasty: a surgical alternative for the management of severe astigmatism from peripheral corneal degeneration.

OBJECTIVE: To describe a compressive lamellar surgical technique for treating severe astigmatism in peripheral corneal ectasia. DESIGN: Retrospective, noncomparative, interventional case series. PARTICIPANTS: Four eyes of 3 patients with either pellucid or Terrien's marginal corneal degeneration were included in this series. METHODS: C-shaped lamellar keratoplasty using multiple trephines of different sizes, with deliberate undersizing of the donor graft for a controlled compressive effect, was performed on these patients. MAIN OUTCOME MEASURES: Visual acuity outcome and refraction were measured at different intervals at up to 40 months of follow-up. RESULTS: All eyes achieved Snellen visual acuity of 20/40 or better and stable astigmatism ranging from 0 to -2.75 diopter cylinder within 6 months, with no recurrence of corneal thinning or peripheral corneal vascularization. CONCLUSIONS: Compressive C-shaped lamellar keratoplasty is able to reduce severe corneal astigmatism in peripheral corneal ectasia and can result in good visual and refractive outcomes with early visual rehabilitation.

Astigmatism↗
PubMedDate not supplied

Practical astigmatism analysis for refractive outcomes in cataract and refractive surgery.

The fundamental concepts underpinning the vectorial analysis of astigmatism are straightforward and intuitive, easily understood by employing a simple golf-putting analogy. The Alpins methodology utilizes three principal vectors and the various ratios between them to provide an aggregate analysis for astigmatic change with parallel indices for spherical correction. A comparative analysis employing both arithmetic and vectorial means together with necessary nomogram adjustments for refining both spherical and astigmatic treatments can also be derived. These advanced techniques, together with their suitability for statistical analysis, comprehensively address the outcome analysis requirements of the entire cornea and the eye's refractive correction, for the purpose of examining success in cataract and refractive surgery.

Astigmatism↗
PubMed2003

Artisan toric phakic intraocular lens for the correction of high astigmatism.

PURPOSE: To evaluate efficacy, predictability, and safety of Artisan toric phakic intraocular lens (Ophtec, Groningen, The Netherlands) implantation for the correction of astigmatism higher than 2 diopters. DESIGN: Interventional case series. METHODS: This prospective study included 27 eyes of 16 patients with a mean preoperative spherical equivalent of -11.78 +/- 6.24 diopters and a mean preoperative astigmatism of -3.43 +/- 0.81. The Artisan phakic intraocular lens was inserted in the anterior chamber through a posterior corneal incision; the technique is similar to the implantation of the classical Artisan lens, but in these cases it is particularly important to secure the lens accurately in the correct axis. The main parameters evaluated in this study were uncorrected visual acuity, best-corrected visual acuity, refraction, and endothelial cell count. RESULTS: Twelve months after the implantation of the Artisan toric phakic intraocular lens, 62.90% of the eyes were within +/-0.50 diopters. of emmetropia and 96.20% within +/-1.0 diopters. Seventy percent of the eyes gained 1 or more Snellen lines from their preoperative best-corrected visual acuity, and 11.11% lost 1 Snellen line. Mean endothelial cell count increased 2.9%. Mean of the parallel and orthogonal components of cylinder correction were 1.97 diopters and 0.10 diopters, respectively, of the intended cylinder change. The mean of axis alignment error was 10.53 degrees. No serious complications were observed. CONCLUSION: Artisan toric phakic intraocular lens implantation appears to be a safe and predictable method for the correction of high levels of astigmatism.

Adult↗
PubMed1984

Reducing surgically induced astigmatism by using a scleral tunnel.

We conducted a prospective study of 36 eyes undergoing pars plana lensectomy, vitrectomy, and implantation of an intraocular lens. We used a scleral tunnel begun 3 mm posterior to the corneoscleral limbus and entered the anterior chamber through clear cornea. We found that this technique produced minimal postoperative astigmatism. After follow-up periods ranging from three to 15 months, the average change in the flatter meridian was -0.07 diopter and that in the steeper meridian was +0.26 diopter. The mean induced astigmatism was -0.33 diopter. A group of nine eyes undergoing pars plana lensectomy and vitrectomy alone showed no significant changes in the postoperative astigmatism. Statistical comparisons established that there was no significant difference between eyes undergoing intraocular lens implantation in addition to pars plana lensectomy and vitrectomy and those not undergoing intraocular lens implantation.

Absorption↗
PubMed2001

Laser in situ keratomileusis to correct myopia, hypermetropia and astigmatism after penetrating keratoplasty for keratoconus: a series of 27 cases.

BACKGROUND: Excimer laser treatment has been shown to be effective and safe in correcting anisometropia following penetrating keratoplasty (PKP). In this report we review our experience with excimer laser in situ keratomileusis (LASIK) to correct refractive myopia, hypermetropia and astigmatism in patients who had undergone PKP for keratoconus. METHODS: We reviewed the records of 22 patients (27 eyes) who had undergone LASIK to correct myopia, hypermetropia or astigmatism, in simple or combined forms, following corneal transplantation for keratoconus. LASIK was performed at a hospital in Curitiba, Brazil, between September 1998 and February 2000. The eyes were classified into two groups: those with a negative spherical equivalent and those with a positive spherical equivalent. LASIK was performed using the Moria LSK microkeratome and the Nidek EC-5000 excimer laser. RESULTS: The mean length of follow-up was 9.52 months for the 23 eyes with myopia and 5.75 months for the 4 eyes with hypermetropia. The mean refractive spherical equivalent in the myopic eyes was -5.27 (standard deviation [SD] 1.91) dioptres before LASIK and -0.45 D (SD 1.68 D) at the last follow-up visit. The corresponding values in the eyes with hypermetropia were +5.18 D (SD 1.46 D) and + 1.18 D (SD 0.94 D). The rate of regression of astigmatism in the myopic eyes was 76%. After surgery 18 (78%) of the myopic eyes and all the hypermetropic eyes had an uncorrected visual acuity of 20/40 or better. The best spectacle-corrected visual acuity was better than 20/25 in 22 (95.7%) of the myopic eyes and all the hypermetropic eyes. One eye lost 1 line of best spectacle-corrected Snellen visual acuity, and one eye lost 6 lines secondary to epithelial ingrowth. Wound dehiscence, intraoperative flap complications, graft rejection or other complications did not develop in this series. INTERPRETATION: In this series, LASIK proved to be relatively safe and effective in correcting refractive errors after PKP for keratoconus.

Adult↗