Correction Of Compound Myopic Astigmatism Research Articles

A comparative fellow-eye prospective study evaluating the efficacy of wavefront-guided VSS VISX CustomVue STAR S4 IR versus the wavefront-optimized WaveLight Allegretto in correction of compound myopic astigmatism

Aim The aim of the present study was to compare the differences in visual outcomes, higher-order aberrations and corneal asphericity, as measured by Q values, in patients undergoing laser in-situ keratomileusis using wavefront-guided variable-spot size VISX CustomVue and wavefront-optimized small-spot size WaveLight Allegretto platforms. Type of study This study was designed as a randomized, prospective, single-blinded, double-armed, fellow-eye comparative study. Patients and methods A total of 100 eyes of 50 patients undergoing customized laser in-situ keratomileusis for compound myopic astigmatism were enrolled and randomly divided into two groups. Each patient underwent full ophthalmological examination; aberrometry was performed on either eye by using VISX CustomVue aberrometer and Allegretto WaveLight aberrometer. Each patient had one eye examined using the Allegretto Wave eye Q system (small-spot scanning), and the fellow eye by using VISX Star CustomVue S4 system (variable-spot scanning). All patients were given postoperative steroids, antibiotic drops and artificial tears. First day postoperative visit was scheduled to check for flap stability, and to exclude complications. Clinical examination and best corrected visual acuity, corneal imaging and aberrometry were scheduled at 1 month and 1 year later. Results Final best corrected visual acuity showed insignificant difference between the two groups ( P = 0.712). The final differences between the groups were insignificant in all other parameters. Conclusion The two ablation profiles are highly comparable in treating compound myopic astigmatism.

Geometric Customization of Optical and Transition Zone Parameters for Treatment of Compound Myopic Astigmatism With the NIDEK EC-5000 Excimer Laser

To compare the refractive outcome of two ablation zone designs using LASIK for the correction of compound myopic astigmatism. This retrospective study compared refractive outcomes in two groups of patients undergoing LASIK. In the circular treatment group, 45 eyes were corrected with circular optical and transition zones of 6 mm and 6.5 mm, respectively. In the customized treatment group, 45 eyes were corrected with optical and transition zones enlarged along the flat axis to 6.5 mm and 7.5 mm, respectively. P values <.05 were considered statistically significant. Mean preoperative spherical equivalent refraction was -5.36+/-2.02 diopters (D) and -5.36+/- 2.13 D for the circular and customized treatment groups, respectively. Mean postoperative spherical equivalent refraction was -0.09+/-0.74 D and -0.11+/-0.42 D for the circular and customized treatment groups, respectively. Mean cylinder was 0.49+/-0.39 D and 0.22+/-0.43 D for the circular and customized treatment groups, respectively (P<.001). Postoperative blur strength index was 0.68+/-0.44 D and 0.39+/-0.27 D in the circular and customized treatment groups, respectively (P<.001). Uncorrected visual acuity was significantly better in the customized treatment group compared with the circular treatment group (P<.05). The gain in lines of best spectacle-corrected visual acuity was significantly greater in the customized treatment group compared with the circular treatment group (P<.001). An elliptical ablation zone for treating compound myopic astigmatism results in better efficacy, safety, and lower tissue removal than a circular treatment zone. This may be due to the geometric optimization provided by the enlargement of the optical and transition zones along the flat meridian.

Keratectasia After LASIK But Not After PRK in One Patient

To report a case of keratectasia in a patient who underwent LASIK in the right eye and photorefractive keratectomy (PRK) in the left eye for correction of compound myopic astigmatism. A 30-year-old man underwent LASIK in the right eye and PRK in left eye for refraction of -1.75 -1.50 x 48 degrees and -1.00 -1.75 x 100 degrees, respectively. Preoperative corneal thickness was 447 microm in the right eye and 446 microm in the left eye. Postoperative corneal thickness decreased to 341 microm and 384 microm in the right and left eye, respectively. Uncorrected visual acuity in the left eye was 20/20, but the right eye developed keratectasia, which led to severe visual loss (20/400). Photorefractive keratectomy may be better than LASIK for ablative refractive surgery for low myopic astigmatism in eyes with low central corneal thickness.

Correction of astigmatism with short arc- length intrastromal corneal ring segments: Preliminary results

Objective To evaluate the refractive effect of 130° short arc length intrastromal corneal ring segments (ICRS) designed to correct myopia concurrent with astigmatism. Design Prospective, nonrandomized, comparative (self-controlled) trial. Participants Ten eyes of 6 patients from one surgical center with manifest refraction spherical equivalent between −1.00 and −6.00 diopters (D), manifest cylinder correction between 1.00 and 6.00 D, and best spectacle-corrected visual acuity of 20/20 or better. Intervention The patients were assigned to receive 1 of 6 ICRS thicknesses, ranging from 0.25 to 0.50 mm by 0.05 mm increments, with an arc length of 130°. Main outcome measures Vector analysis of astigmatic correction. Efficacy was assessed by uncorrected visual acuity and by deviation of postoperative spherical and cylindrical refractive error from predicted correction. Safety was assessed by maintenance or loss of preoperative best spectacle-corrected visual acuity. Measurements were made before surgery and after surgery at days 1 and 7 and months 1, 2, 3, and 6. Results At 6 months, uncorrected visual acuity was 20/20 or better in 80% of eyes (8/10) and 20/40 or better in all eyes. Eight of 10 eyes (80%) were within ±0.25 D of plano spherical equivalent manifest refraction. There was no loss of best spectacle-corrected visual acuity, and 6 of 10 eyes (60%) gained a line. Reduction of keratometric cylinder by ICRS thickness was statistically significant ( P = 0.039). Conclusions Preliminary results of visual and refractive performance after correction of compound myopic astigmatism using short arc length ICRS are promising.

Combined myopia-astigmatism correction. A comparison with pure myopia correction

Myopic PRK up to 6 D is an approved and safe procedure. The efficacy and safety of combined treatment of myopia and astigmatism in compound myopic astigmatism (PARK) have not yet been demonstrated. In a prospective study in 342 eyes the results of myopic PRK were compared to those of correction of compound myopic astigmatism (PARK). Regarding spherical refraction achieved there was no significant difference between groups. Best corrected visual acuity only improved in the group with high astigmatism; this group also showed the least number of Central Islands. Permanent haze and steroid-induced glaucoma or cataract were not observed after treatment up to 6 D. Average astigmatism of 2.24 D was be reduced to 0.53 D 1 year post-operatively. Correction of astigmatism resulted in undercorrection of approximately 30%. Our experience with the keracor shows PRK up to 6 D with or without additional correction of astigmatism (PARK) to be comparatively safe in terms of regression and complications and equally accurate in reaching spherical target refraction.

Excimer laser in situ keratomileusis to correct compound myopic astigmatism.

We studied the efficacy, predictability, stability, and safety of excimer laser in situ keratomileusis (LASIK) to correct myopia and astigmatism. We prospectively studied 87 consecutive eyes of 56 patients who received LASIK, divided into two groups: the myopic group included eyes with myopia more than -2.00 diopters (D) and astigmatism less than 0.50 D and the astigmatism group included eyes with myopia of more than -2.00 D and astigmatism of 0.50 D or more. The Chiron automated corneal shaper and the Nidek EC-5000 excimer laser were used in all eyes. A modified personal nomogram was used in all eyes. The changes in refractive sphere and cylinder, and complications were studied at 2 and 6 weeks, 3, 6, and 12 months after surgery. Preoperatively, the mean spherical equivalent refraction was -4.41 D (range, -2.25 to -7.25; SD, 1.74) in the myopia group and -5.79 D (range, -2.25 to -15.50 D; SD, 2.45) in the astigmatism group. The mean spherical component of the refraction was -4.39 D (range, -2.25 to -7.25; SD, 1.74) in the myopia group and -5.19 D (range, -2.00 to -14.00; SD, 2.32) in the astigmatism group. The mean refractive cylinder was 1.19 D (range, 0.5 to 3.00 D; SD, 0.62) in the astigmatism group. At 12 months, 81 eyes (93.6%) of 51 patients were examined; the mean spherical equivalent refraction was -0.43 D (range, +0.50 to -1.25 D; SD, 0.35) in the myopia group and -0.33 D (range, +1.25 to -2.13 D; SD, 0.52) in the astigmatism group. The mean spherical component of the refraction at 12 months was -0.33 D (range, +0.50 to -1.25 D; SD, 0.33) in the myopia group and -0.17 D (range, +1.50 to -1.50; SD, 0.48) in the astigmatism group. The mean refractive cylinder was 0.19 D (range, 0 to 0.75 D; SD, 0.25) in the myopia group and 0.32 D (range, 0 to 1.25 D; SD, 0.30) in the astigmatism group. The mean change in spherical equivalent refraction between 6 weeks and 12 months after surgery was -0.08 D toward myopia (range, -0.50 to -0.75 D; SD, 0.23) in both groups. No eyes lost two or more lines of spectacle-corrected visual acuity. Patient satisfaction was high in both groups. Complications included undercorrection that necessitated reoperation (three eyes), overcorrection (two eyes), and small disc diameter (one eye). No vision threatening complications were observed. LASIK with the Nidek EC5000 laser is effective, reasonably predictable, stable, and safe for correction of compound myopic astigmatism with a spherical component between -2.00 and -14.00 D, and a cylindrical component between 0.50 and 3.00 D using the techniques in this study. Astigmatism is undercorrected with the current algorithm. Correction of higher amounts of astigmatism requires further study.

Photorefractive keratectomy for compound myopic astigmatism with an eye cup erodible mask delivery system.

The erodible mask is a new energy delivery system for the 193-nm argon fluoride excimer laser. It consists of a polymethyl-methacrylate button, whose profile is transferred by photoablation onto the corneal surface. We present the 6- and 12-month results of this technique in the correction of compound myopic astigmatism. We performed the mask procedure on 21 eyes of 16 subjects (mean age, 30.7 years; range, 24 to 46) to correct combined myopia and astigmatism. Attempted myopic correction ranged between -1.50 diopters (D) and -10.00 D (mean, -7.07 D). Attempted astigmatic correction ranged between -1.50 D and -4.00 D (mean, -2.46 D). Mean procedure error was: sphere +0.74 D (range, -3.00/+5.00), cylinder -1.41 D (range, -3.50/0.00) at 1 month after surgery; sphere +0.18 D (range, -2.50/+ 3.50), cylinder -1.56 D (range, -4.00/0.00) at 6 months; and sphere -1.30 D (range, -3.00/0.00), cylinder was -1.25 D (range, -2.00/-0.50) at 12 months (10 eyes). During follow up, haze values were never higher than 1, except for one case of haze 2 that regressed to 0 during follow up. Postoperative uncorrected visual acuity improved in all eyes where emmetropia was envisaged; none of the eyes lost spectacle-corrected visual acuity lines 6 or 12 months after surgery. The erodible mask proved effective and fairly predictable mainly in the correction of the spherical component of refractive error, while the correction of astigmatism revealed greater unpredictability, with a constant trend to undercorrection.

Indications, results, and complications of refractive corneal surgery with lasers.

The applications of the current laser technology in refractive surgery have developed during the past year. Several techniques to correct ametropia with various laser sources have been proposed and investigated. To date, using the myopic photorefractive keratectomy excimer laser is the most common technique; it has already been performed on more than 100,000 eyes worldwide. Refractive results on large series of patients with long-term follow-up indicate that the technique is safe, effective, and highly predictable in the correction of low to moderate myopia. Concerns about the treatment of high myopia still arise, especially regarding regression toward myopia and stability of achieved refraction; multizone treatments have been proposed to reach better results. The correction of compound myopic astigmatism with the excimer laser seems to be promising, although long-term results on large series are still pending. Among the patients treated, very few complications occurred. We believe that laser technology will play the most important role in refractive surgery in the future.

Photorefraktive Keratektomie zur Korrektur von myopem Astigmatismus

Nine eyes underwent superficial ablation with excimer laser for treatment of compound myopic astigmatism. In eight of the eyes, corneal cylinder was naturally-occurring, and in one eye the astigmatism had developed following retinal detachment surgery. All patients have been followed for 9 months. The pre- and postoperative cylinder was -2.7 +/- 0.4 diopters and -1.3 +/- 0.4 diopters, respectively, while the pre- and postoperative spherical equivalent was -4.7 +/- 0.4 diopters and -1.3 +/- 0.4 diopters, respectively. Uncorrected acuity improved from a preoperative mean of 20/300 to a postoperative mean of 20/40. Patients with a residual refractive error often demonstrated reasonably good unaided acuity. Toric ablations with the excimer laser can be performed at the same time as ablations for myopia, and appear to represent a promising strategy for correction of compound myopic astigmatism; the relative safety and efficacy of this procedure, and of combined radial and astigmatic keratotomy remain to be determined.

Photorefractive Keratectomy for Astigmatism

Excimer laser photorefractive keratectomy, developed to perform radially symmetric ablations to correct myopic or hyperopic refractive errors, was used to perform toric ablations designed to correct cylindrical errors. An expanding slit was used to flatten the cornea in the steep meridian. Four contact lens-intolerant patients underwent this procedure for correction of astigmatism (two patients after penetrating keratoplasty, one patient after corneal ulcer, and one patient with naturally occurring high astigmatism). In each patient, surgery reduced the regular component of the astigmatism; residual irregular astigmatism limited spectacle-corrected acuity in one patient. All patients experienced a shift in spherical equivalent toward hyperopia. Toric ablations with the excimer laser appear to represent a promising strategy for the correction of compound myopic astigmatism that does not rely on creation of deep corneal incisions, excisions, or compression sutures.