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At least 811 records · Page 45Linked to original sources
PubMed1996

Excimer laser photorefractive keratectomy to correct astigmatism.

PURPOSE: To evaluate the efficacy of excimer laser photorefractive keratectomy (PRK) to correct astigmatism. SETTING: Hôpital Morvan, Brest, France. METHODS: A 193 nm excimer laser was used to perform toric ablation with an expanding slit to flatten the cornea in the steeper meridian and/or to correct myopia with an iris diaphragm in 72 eyes (55 patients): 68 eyes for compound myopic astigmatism and 4 for astigmatism only. RESULTS: Preoperative cylinder was -2.14 diopters (D) +/- 1.99 (SD) (range -0.50 to -5.50 D); 6 months postoperatively, it was -1.75 +/- 1.34 D (range -0.25 to -5.25 D). Preoperative spherical equivalent was -5.33 +/- 3.22 D (range -0.25 to -14.50 D); 6 months postoperatively, it was -0.86 +/- 2.32 D (range 2.50 to -9.75 D). The axial error was within 30 degrees. Uncorrected visual acuity was 0.50 or better in 64.5% of patients. CONCLUSIONS: Overall patient satisfaction seemed the result of the myopic correction; cylindrical correction was incomplete. Future software refinements should improve the results. In particular, single elliptical ablation seems to offer theoretical advantages.

Adolescent↗
PubMed1996

Evaluation of bidirectional radial and astigmatic keratotomy.

PURPOSE: To analyze the outcome of incisional radial and astigmatic keratotomy using a bidirectional keratome. METHODS: We used a bidirectional cutting diamond keratome on 100 consecutive eyes (mean patient age 38 years, range 18 to 67 years) whose mean preoperative cycloplegic refraction was -4.64 (range of sphere -1.50 to -15.25) and +1.25 of cylinder (range of cylinder +0.50 to +5.00). RESULTS: Mean postoperative cycloplegic refraction was -0.31 (range +0.50 to -1.25) and +0.25 cylinder (range 0 to +1.00). At the end of 1 year, 97% of eyes had an uncorrected visual acuity of 20/40 or better. The rate of enhancement of the original keratotomy was 10%; all of these eyes had more than -6.25 diopters (D) of sphere or +2.00 D of cylinder preoperatively. Side effects were minimal, and no sight-threatening complications occurred. CONCLUSION: In this study, bidirectional incisional radial and astigmatic keratotomy was an accurate and predictable technique for myopia and astigmatism; all patients were satisfied with the procedure.

Adolescent↗
PubMed1996

Lenticular astigmatism after penetrating eye injury.

Lenticular astigmatism of 5.00 diopters developed after penetrating injury in the eye of a 16-year-old boy. Full visual acuity, refraction, and crystalline lens clarity remained stable for more than 2 years. The high astigmatism, in conjunction with a spherical cornea and posterior lens capsule striae, indicates the lenticular origin of the astigmatism.

Adolescent↗
PubMed1997

Refractive outcome following radial keratotomy and combined radial and astigmatic keratotomy.

PURPOSE: To determine whether the visual and refractive outcomes of combined astigmatic and radial keratotomy (AK/RK) procedures was different from that following RK for the correction of naturally occurring compound myopic astigmatism and spherical myopia. SETTING: Private professional practice, San Diego, California, USA. METHODS: The computer database of all incisional procedures performed by one surgeon over 10 years was reviewed to compare the visual acuity outcome of AK/RK and RK procedures. Enhancement procedures were excluded. Only data from the last office visits were analyzed to establish the relationship between visual acuity and type of keratotomy procedure performed. A multiple regression model was constructed, which included covariates of age, postoperative keratometric cylinder, and postoperative refraction. RESULTS: After controlling for covariates, the AK/RK population had significantly lower postoperative uncorrected visual acuity levels than the RK population (P < .03) after one operation (prior to enhancement surgery). CONCLUSIONS: Using the nomograms for myopia correction for unenhanced RK cases, combined AK and RK procedures appeared to reduce the expected visual results. Surgeons may consider modifying surgical nomograms to account for the expected spherical undercorrection that can occur when myopia and astigmatism are corrected simultaneously.

Adult↗
PubMed1997

Induced astigmatism after near-clear hinge incision.

PURPOSE: To evaluate astigmatism induced by the near-clear hinge incision. SETTING: Casa di Cura Villa Toniolo, Bologna, and Day Hospital Nuova Ricerca, Rimini, Italy. METHODS: The results in 100 eyes having phacoemulsification with a 3.2 or 4.1 mm temporal near-clear hinge incision were evaluated for a maximum of 6 months. Corneal curvature was measured using computerized videokeratography, and surgically induced astigmatism was computed by vector analysis. Surgically induced corneal topographic changes were also evaluated. RESULTS: Mean induced cylinder in the 3.2 mm incision group was 0.4 diopter (D) +/- 0.2 (SD) 6 months after surgery; there was no significant difference in the values at 4 days and 6 months. Mean induced cylinder in the 4.1 mm incision group was similar at 1 and 6 months (0.47 and 0.45 D, respectively). However, it was significantly higher at 4 days (0.56 D). Vector decomposition analysis showed that the with-the-rule component was prevalent and remained constant over 6 months. Topographic analysis showed localized wound-related flattening with minimal central corneal changes. CONCLUSION: The near-clear hinge incision was almost astigmatically neutral and resulted in self-sealing incisions that did not leak.

Astigmatism↗
PubMed1998

Evaluation of axis alignment system for correction of myopic astigmatism with the excimer laser.

PURPOSE: To evaluate the efficacy of in situ axis alignment for the treatment of myopic astigmatism with an excimer laser. METHODS: In this prospective clinical trial, 71 eyes with stable astigmatism of -1.00 to -6.00 diopters (D) with or without stable myopia of up to 10.00 D were randomized to receive excimer treatment of their astigmatic component aligned to the axis determined by subjective refraction (control group) or to have the alignment verified and altered is necessary by in situ alignment (axis alignment group). A VISX Twenty-Twenty excimer laser was used for the treatment. Patients were followed for 6 months. RESULTS: In 85% of eyes in the axis alignment group, the axis of cylinder was different from that calculated by routine refraction. Pretreatment mean cylinder was -1.81 D +/- 0.91 (SD) in the axis alignment group and -1.75 +/- 0.60 D in the control group. At 6 months, an undercorrection of cylinder was seen in both groups; the mean residual cylinder was -0.70 +2- 0.56 D in the axis alignment group and -0.59 +/- 0.50 D in the control group. More than 80% of all eyes were within +/- 1.00 D of plano and achieved an uncorrected visual acuity of 6/12 or better. A loss of two or more lines of best corrected visual acuity was recorded in three eyes. CONCLUSION: The in situ alignment technique did not produce better results of photoastigmatic refractive keratectomy than the routine axis alignment technique.

Adult↗
PubMed1998

Topographic assessment of irregular astigmatism after photorefractive keratectomy.

OBJECTIVE: To correlate new quantitative topographic indexes of corneal irregular astigmatism to best spectacle-corrected visual acuity (BSCVA) following excimer laser photorefractive keratectomy (PRK). SETTING: Department of Ophthalmology, LSU Eye Center, and Refractive Surgery Center of the South, Ear, Nose & Throat Hospital, New Orleans, Louisiana; Manhattan Eye, Ear and Throat Hospital, New York, New York, USA. METHODS: Videokeratography data (TMS-1) were obtained preoperatively and 1, 3, 6, 12, 18, and 24 months postoperatively from 100 eyes having PRK for low to mild myopia. Algorithms measured fine local irregularity with the surface regularity index (SRIp), varifocality with the coefficient of variation of corneal power (CVPp), and central islands with the elevation/depression magnitude (EDM). RESULTS: The SRIp and CVPp increased after surgery and remained significantly higher than the preoperative levels throughout the 24 month follow-up (P < .05). The increase in EDM was significant from 1 to 6 months (P < .05) but not thereafter. Multiple regression analysis revealed that variables having a statistically significant relationship with postoperative BSCVA were CVPp and EDM at 1 month, CVPp at 3 months, and CVPp, haze, and age at 6 months. No statistically significant correlation between any measures of irregular astigmatism and BSCVA was found after 1 year of follow-up. CONCLUSION: The quantitative measures used in this study are sensitive methods by which irregular astigmatism after keratorefractive procedures can be classified, evaluated, and compared.

Algorithms↗
PubMed1998

Laser in situ keratomileusis for myopia and myopic astigmatism.

PURPOSE: To evaluate the precision and safety of myopia and astigmatism correction using laser in situ keratomileusis (LASIK). SETTING: Augenchirurgie und Laserzentrum Hoch-Rum (Sanatorium der Kreuzsch-western), Innsbruck, Austria. METHODS: In this prospective study, LASIK was performed on 66 eyes of 39 patients with myopia ranging from 1.50 to 16.00 diopters (D). Astigmatism, ranging from -0.00 to -3.00 D, was treated simultaneously. Surgery was performed with the Chiron Keracor 117 excimer laser and the Chiron Automated Corneal Shaper microkeratome. During the 6 month follow-up, manifest refraction as well as best corrected and uncorrected visual acuities were measured; corneal topographies were produced and slitlamp biomicroscopy was performed. Changes in visual acuity and corneal topography were evaluated. RESULTS: After 6 months, mean myopia had decreased from 6.78 D +/- 3.48 (SD) to 0.40 +/- 0.98 D. Fifty-one of 63 eyes (81.0%) were within +/- 1.00 D of spherical emmetropia and 61 of 63 (96.8%) within +/- 1.00 D of cylindrical emmetropia. Uncorrected visual acuity improved in all eyes; it was 20/40 or better in 82.5% 6 months postoperatively. Best corrected visual acuity did not change in most eyes; 9.5% lost two or more Snellen lines. No central islands or corneal scars were detected postoperatively. Haze was noted in only 6 eyes (9.1%); it was transient and less than grade 1. No sight-threatening complications occurred intraoperatively. CONCLUSION: Laser in situ keratomileusis was an exact and predictable procedure for correcting low, moderate, and high myopia and myopic astigmatism.

Adult↗
PubMed1998

Astigmatism induced by intrastromal corneal suture after small incision phacoemulsification.

PURPOSE: To evaluate the course of astigmatic evolution and complications after clear corneal incisions using an intrastromal corneal suture. SETTING: Instituto Oftalmologico de Alicante, University of Alicante, Spain. METHODS: Eighty eyes of 62 patients had endocapsular phacoemulsification. A foldable intraocular lens was implanted through a 4.0 mm clear corneal incision. A 10-0 nylon intrastromal corneal suture was used in all eyes. Change sin corneal astigmatism were calculated by vector analysis; follow-up was 6 months. Early and late suture-related complications were also evaluated. RESULTS: Mean induced cylinder was 1.25 diopters (D) +/- 1.24 (SD) with the wound 1 day postoperatively and 0.19 +/- 0.81 D against the wound at 6 months. There were no incision- or suture-related complications postoperatively. CONCLUSION: Use of the intrastromal corneal suture led to astigmatically neutral closure of multiplanar corneal incisions.

Acrylates↗
PubMed1998

Long-term course of surgically induced astigmatism after a 5.0 mm sclerocorneal valve incision.

PURPOSE: To study surgically induced astigmatism (SIA) after a sutureless 5.0 mm sclerocorneal valve incision. SETTING: Department of Ophthalmology, University of Vienna, Vienna, Austria. METHODS: This study evaluated SIA in 34 cases of sutureless cataract surgery with a 5.0 mm superior sclerocorneal valve incision and implantation of a poly(methyl methacrylate) intraocular lens. Keratometry was measured with a Zeiss keratometer in all cases preoperatively, and 1 day, 1 week, 1 and 3 months, and 1 and 5 years postoperatively. RESULTS: Surgically induced astigmatism, calculated by Cravy's vector analysis, showed an initial mean with-the-rule shift of 0.35 diopter (D), followed by an against-the-rule shift to a mean of -0.30 D after 1 month. One year postoperatively, mean SIA was -0.46 D. Between 1 and 5 years postoperatively, there was a statistically significant increase in mean SIA calculated by Cravy's vector analysis; SIA increased from -0.46 D after 1 year to -0.76 D after 5 years postoperatively. CONCLUSIONS: A small, although statistically significant, amount of postoperatively induced astigmatism occurred 5 years after a sutureless 5.0 mm sclerocorneal valve incision.

Aged↗
PubMed1999

Refractive astigmatism after oblique clear corneal phacoemulsification cataract incision.

PURPOSE: To determine the astigmatic effect of a supero-oblique clear corneal phacoemulsification cataract incision. SETTING: A university-based general ophthalmology practice. METHODS: All eyes having supero-oblique phacoemulsification cataract surgery using the right hand of a single surgeon between April 17, 1997, and July 24, 1997, were prospectively included. There were 52 eyes of 52 consecutive patients. Manifest refraction was performed preoperatively and 1, 3, and at least 6 months postoperatively. A Fourier method of vector analysis was used. RESULTS: Mean refractive error (Fourier corrected) for all eyes and all ages preoperatively was -1.422 + 0.085 x 35.85. At 6 months, it was -0.620 + 0.190 x 14.2. There was little difference between right and left eyes. Patients older than 80 years had greater induced astigmatism. CONCLUSION: This study provides evidence that making a supero-oblique clear corneal phacoemulsification incision while sitting in the more natural superior position does not induce a clinically important amount of oblique astigmatism.

Adult↗
PubMed1999

Results of laser in situ keratomileusis in hyperopic compound astigmatism.

PURPOSE: To evaluate the efficacy and safety of steepening the flatter meridian with laser in situ keratomileusis (LASIK) to correct hyperopic compound astigmatism using the Schwind-Keratom laser with the MultiScan System and the active tracking system for centering the ablation. SETTING: Instituto Barraquer de América, Bogotá, Colombia. METHODS: From June to December 1997, LASIK was performed in 111 eyes to correct congenital hyperopic compound astigmatism. Preoperatively, the mean spherical equivalent was +2.58 diopters (D) (range +1.50 to +3.50 D) in 37 eyes (low dioptric group), with a mean sphere of +3.66 D (range +1.75 to +5.50 D) and a mean cylinder of -2.11 D (range -0.50 to -5.00 D); +4.71 D (range +3.51 to +6.00 D) in 50 eyes (middle dioptric group), with a mean sphere of +5.58 D (range +4.00 to +7.00 D) and a mean cylinder of -1.83 D (range -0.50 to -4.50 D); and +7.26 D (range +6.01 to +10.00 D) in 24 eyes (high dioptric group), with a mean sphere of +8.25 D (range +6.50 to +10.00 D) and a mean cylinder of -1.98 D (range -0.50 to -4.00 D) in 24 eyes. Postoperative results were measured at 10 days and 6 months. RESULTS: At 6 months, the mean residual subjective spherical defect was +0.32 D (range -0.50 to +1.00 D) in the low dioptric group, with a mean cylinder of -0.61 D (range 0.00 to -1.75 D); all eyes were within +/- 1.00 D of emmetropia. The mean defect was +0.82 D (range 0.00 to +2.50 D) in the middle dioptric group, with a mean cylinder of -0.61 D (range 0.00 to -2.50 D); 80% of eyes were within +/- 1.00 D of emmetropia. The mean defect was +1.10 D (range -0.50 to +3.00 D) in the high dioptric group, with a mean cylinder of -1.39 D (range 0.00 to -3.25 D); 77% of eyes were within +/- 1.00 D of emmetropia. In the study group as a whole, 90% of eyes had a cylinder correction within +/- 1.00 D of emmetropia. Uncorrected visual acuity (UCVA) was 0.50 (20/40) or better in 23.4% of eyes preoperatively and 0.50 (20/40) or better in 71.0% 6 months postoperatively. CONCLUSIONS: Steepening the flatter meridian with the MultiScan System safely and effectively corrected hyperopic astigmatism. The rapid recovery of UCVA was due not only to correction of the ametropia, but also to the centering provided by the active tracking system.

Adolescent↗
PubMed1999

Implantation of a toric poly(methyl methacrylate) intraocular lens to correct high astigmatism.

A 57-year-old man experienced a decrease in visual function because of cataract formation. Corneal astigmatism was 13.4 diopters (D) because he had had a penetrating keratoplasty 27 years before. Cataract surgery was planned, and biometric data for toric intraocular lens (IOL) implantation were collected for the manufacture of a custom IOL. After phacoemulsification, a toric poly(methyl methacrylate) (PMMA) IOL of +19.0 D spherical and +12.0 D cylindrical power was implanted via a sclerocorneal tunnel incision. Three months postoperatively, corneal astigmatism was 14.3 D and best corrected visual acuity (BCVA), 20/25. Postoperative refraction (+1.5 -3.0 x 90) and BCVA remained stable for 7 months. No significant IOL rotation was observed. Implantation of a toric PMMA IOL corrected high corneal astigmatism. Toric IOL technology with high cylindrical power allows enhancement of IOL surgery.

Astigmatism↗
PubMed2000

One year follow-up of astigmatism after 4.0 mm temporal clear corneal and superior scleral incisions.

PURPOSE: To compare the effect of 2 contemporary sutureless cataract surgery incisions on corneal astigmatism 1 year after surgery. SETTING: Outpatient Clinic, Department of Ophthalmology, Vejle Hospital, Denmark. METHODS: Sixty-nine patients who had cataract surgery in 1997 with a 4.0 mm temporal clear corneal (n = 32) or superior scleral (n = 37) incision were examined 1 year postoperatively. Surgically induced astigmatism was analyzed by vector analysis, vector decomposition, and polar values using preoperative and postoperative keratometric readings. RESULTS: Vector analysis revealed a slightly lower median induced cylinder in the clear corneal patients; 0.41 diopter (D) (95% confidence limits [CL] 0.24 to 0.67 D) versus 0.61 D (95% CL 0.49 to 0.73 D) (P < .05). Decomposition of the induced cylinder (against the rule/total) showed statistically significant differences in the direction of the cylinder; 0.21 (95% CL 0.03 to 0.41) versus 0.90 (95% CL 0.82 to 0.95) (P < .00001). The directional difference was confirmed by polar values. CONCLUSION: Both incisions induced low and comparable amounts of astigmatism. The directional differences were modest. Findings in previous studies of a poor outcome after clear corneal incisions were not confirmed in this long-term follow-up.

Aged↗
PubMedDate not supplied

Refractive astigmatism acts predominantly as a source of high spatial frequency image distortion: the associated lineal distortions can be overcome by using a low pass spatial filter!

PURPOSE: Surprisingly, an important characteristic of astigmatism has been overlooked by ophthalmic and clinical scientists. Apparently, refractive astigmatism is due largely to a form of high spatial frequency image distortion. METHODS: Characteristic astigmatic image distortion can be minimized or eliminated by using a low-pass spatial filter (here, a ground glass plate was employed for this purpose). The ground glass is placed a short distance in front of a visual acuity chart, or it may be used with other tests, such as vernier acuity. RESULTS: This test has been performed by us on large numbers of patients and test subjects. A clinician can try this test for himself/herself. Place a +2.00 D.C. (any axis) lens in front of the eye; the usual distortions will be observed. Locate the ground glass plate as described. The usual distortions associated with the conoid of Stürm will not be visible or will be virtually eliminated, although some image blur will remain. CONCLUSIONS: This technique has significance, e.g., in visual screening programs in developing nations, or in assessing patients with media disorders prior to ophthalmic surgery.

Astigmatism↗
PubMed1997

Astigmatism decay immediately following suture removal.

In a prospective study of 34 patients with high post-operative astigmatism (mean 6.90 D, range 2.75-15.00 D) following extracapsular cataract surgery (13 limbal sections and 21 corneal sections), we used keratometry to assess the changes in corneal curvature seen within 30 minutes of suture removal and compared these with the astigmatism found 2 weeks later. The greatest change occurred within the first 5 minutes of suture removal (mean 3.63 D; 95% confidence interval (95% CI) 2.85-4.41). The rate of decay then declined so that between 15 and 30 minutes the mean change was 0.56 D (95% CI 0.43-0.69). At 2 weeks a further mean decay of 1.29 D (95% CI 0.99-1.61) occurred. Of the 6 patients exhibiting a residual astigmatism greater than 3.00 D at 30 minutes, 4 continued to do so 2 weeks later. Our study suggests that keratometry 30 minutes following suture removal is only moderately different from that seen 2 weeks later. Although not stable enough to suggest that patients could be routinely refracted within 30 minutes of suture removal, in cases where early visual recovery is essential, such as in monocular patients, it may be reasonable to offer a temporary spectacle correction immediately following suture removal. Furthermore keratometry at 30 minutes after suture removal accurately predicts the necessity for further removal of sutures and indicates which patients can be discharged to the care of their own optometrist, making a further hospital visit unnecessary.

Aged↗
PubMed2000

Effect of lens style on postoperative refractive astigmatism after small incision cataract surgery.

PURPOSE: To evaluate the astigmatic results of two popular foldable intraocular lenses when standard surgical approaches are used in rural private practice in Australia. METHODS: Four hundred consecutive cataract operations were followed in a prospective study. The refractive results of patients receiving the Alcon Acrysof MA30 lens were compared to those receiving the Allergan silicone S140 lens. All patients were over 60 years of age and had no intercurrent ocular disease. Refractive and keratometric astigmatism was analysed both by vector analysis and as an absolute measure. RESULTS AND CONCLUSION: The Acrysof lens is associated with less postoperative astigmatism (P = 0.01), than the Silicone S140 lenses.

Acrylates↗
PubMed2004

[Toric intraocular lenses for compensation of corneal astigmatism].

BACKGROUND: Besides arcuate or straight transverse keratotomies, toric intraocular lenses are of increasing popularity to enhance the visual function in cases of lens opacification for the correction of corneal astigmatism and the following ocular surgery such as penetrating keratoplasty. The purpose of this study was to present a generalized scheme for the calculation of toric intraocular lenses and to demonstrate its potential on a clinical example in a step-by-step approach. METHODS: After providing some helpful approximations for the clinicians, i. e., for a conversion of radii differences to corneal astigmatism, the calculation scheme using vergence transformation in a paraxial space and the dualism of the standard and component notation for the description of spherocylindrical vergences and spherocylindrical refractive surfaces is described. RESULTS: In a clinical example, a toric intraocular lens is calculated step-by-step using the above-mentioned calculation scheme. The methodology is designed in a matrix structure for the direct implementation in a computer language. In a second step, a toric lens similar to the calculated lens in the manufacturing grid is selected and inserted with a small angle of rotation from the ideal implantation axis to demonstrate the effect on postoperative refraction. CONCLUSIONS: The calculation scheme allows the determination of toric intraocular lenses with an astigmatic cornea and enables us to achieve a spherocylindrical target refraction with cylinder axis at random. Furthermore, the postoperative refraction at the spectacle or corneal plane can be simulated by inserting any toric intraocular lens oriented in any axis. The concept can be easily generalized to 'thick' toric intraocular lenses if the geometrical data and the refraction index of the material are known.

Astigmatism↗