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PubMed1993

Changes in keratometric astigmatism after suture removal more than one year after penetrating keratoplasty.

BACKGROUND/PURPOSE: Selective removal of interrupted sutures and adjustment of a running suture can minimize astigmatism after penetrating keratoplasty, but the long-term effects of early suture manipulations remain largely unknown. The authors tested the hypothesis that the cornea becomes "fixed" more than 1 year after keratoplasty so that desirable refractive results will remain when all sutures are eventually removed. METHODS: The authors reviewed retrospectively the changes in astigmatism that occurred when all remaining sutures were removed from 162 eyes 1 to 6 years after penetrating keratoplasty. Single-running sutures were used in 130 eyes, double-running sutures in 20 eyes, and a combination of interrupted and running sutures in 12 eyes. RESULTS: Removal of single-running sutures caused an average decrease in astigmatism of 0.52 diopters (D) from 6.10 +/- 4.41 D to 5.57 +/- 3.14 D. However, the astigmatism in 62% of eyes changed 2 or more D (range, 11.94 to -17.87 D), and the range changed more than 20 degrees in 55% of eyes. The average vectorial change was 6.5 +/- 4.3 D (range, 0.59 to 19.8 D). There was no decrease in the amount of astigmatic change with increasing time between surgery and suture removal. Graft size and diagnosis had no effect on the amount of astigmatic change. Astigmatic errors became stable, with less than 1 D of change between successive examinations within 6 months after suture removal. Similar results were obtained for eyes with double-running and interrupted-running sutures. CONCLUSIONS: Corneal astigmatism may change unpredictably and by large amounts when all remaining sutures are removed 1 to 6 years after penetrating keratoplasty.

Astigmatism↗
PubMed1999

Photorefractive keratectomy for low-to-moderate myopia and astigmatism with a small-beam, tracker-directed excimer laser.

OBJECTIVE: To assess the safety and effectiveness of the Autonomous Technologies Corporation LADARVision excimer laser system for photorefractive keratectomy correction of myopia and astigmatism. DESIGN: A multicenter, prospective, noncomparative case series. PARTICIPANTS: The cohort consisted of 467 eyes corrected for spherical myopia and 211 eyes corrected for myopia with astigmatism. INTERVENTION: Treatments were performed at six sites in the United States using a 6-mm ablation zone for spherical myopes and a 5.5-mm zone with a 1.0-mm blend for astigmats. MAIN OUTCOME MEASURES: Visual acuity, subjective refraction, corneal haze, intraocular pressure, complications, adverse reactions, patient satisfaction, and corneal endothelial changes. RESULTS: Twelve-month follow-up was available on 414 spherical eyes and 175 astigmatic eyes. The results for spherical eyes with correction between -1 and -5.99 diopters (D) were: uncorrected visual acuity (UCVA) of 20/40 or better achieved by 98.1%, 20/20 or better by 72%, 1.8% lost 2 lines and 0.3% lost greater than 2 lines of best spectacle-corrected visual acuity (BSCVA); 76.4% were within 0.50 D of the target correction and 94.4% were within 1.00 D. The results for myopia with astigmatism with spherical equivalent correction between -1 and -5.99 D were: UCVA of 20/40 or better in 97.4%, 20/20 or better in 61.7%, 2.5% lost 2 lines and no eyes lost greater than 2 lines BSCVA; 73.9% were within 0.50 D of the target correction and 95% were within 1.00 D. For spherical myopes combined with myopic astigmats corrected for 6 to 10 D, results were: UCVA of 20/40 or better in 93.4%, 20/20 or better in 61.2%, 2.3% lost 2 lines and no eyes lost greater than 2 lines of BSCVA; 67.2% were within 0.50 D of the desired correction and 87.8% were within 1.00 D. Refractive stability was achieved between 3 and 6 months for the spherical and astigmatic groups. No eyes had corneal haze graded as moderate or greater, and there was no significant decrease in endothelial cell density. CONCLUSIONS: Patients treated for 1 to 10 D of spherical equivalent myopia, with or without astigmatism, showed early refractive stability, excellent UCVA, no significant loss of BSCVA, no loss of endothelial cell density, and very low levels of corneal haze to 12 months after surgery.

Adult↗
PubMed1994

Management of astigmatic keratotomy overcorrections by corneal sutures.

Astigmatic overcorrection is a significant possible complication of refractive surgical procedures such as radial keratotomy, astigmatic keratotomy, and combined radial and astigmatic keratotomy. We present the results of a study in which astigmatic overcorrection was reversed by suturing the astigmatic incisions. Videokeratoscopic studies of 15 patients showed that this technique induced a wide range of central corneal steepness, thus correcting variable amounts of astigmatic overcorrection. Mean preoperative uncorrected visual acuity was 20/100 while the mean postoperative uncorrected visual acuity was 20/40. One year after surgery, 13 patients had gained two or more Snellen lines of uncorrected vision; the remaining two had no improvement. Refraction was stable in all cases. No significant complications were observed at one year postoperatively. Corneal sutures may be used safely to manage overcorrections after astigmatic keratotomy or combined radial and astigmatic keratotomy with satisfactory results, even though the predictive value of the technique is limited.

Adult↗
PubMed1996

Excimer photorefractive keratectomy for low myopia and astigmatism with the Coherent-Schwind Keratom.

PURPOSE: To summarize the initial results of excimer laser photorefractive keratectomy (PRK) in 114 eyes of 89 patients using the Coherent-Schwind system and assess its safety, efficacy, and predictability. SETTING: Hospital San Jose de Monterrey-ITESM, Mexico. METHODS: The Coherent-Schwind Keratom excimer laser was used to correct low myopia (manifest spherical equivalent from -1.00 to -6.00 diopters [D], with manifest cylinder of -1.00 D or less) or myopic astigmatism (manifest spherical equivalent from -2.75 to -6.75 D, with manifest cylinder from -1.00 to -4.50 D) with standard settings. Ablation zone diameters were from 5.9 to 6.3 mm (low myopia) and 5.9 to 8.2 mm (astigmatism) with a repetition rate of 12 Hz. Follow-up was from 1 month (low myopia, n = 71; astigmatism, n = 35) to 6 months (low myopia, n = 36; astigmatism, n = 17). RESULTS: Six months after PRK, uncorrected visual acuity was 20/40 or better in 94% of the low myopia eyes (n = 36) and 77% of the astigmatism eyes (n = 17). Intended correction was within 1.00 D of the target spherical equivalent in 81 and 88% of eyes, respectively. No eyes in the low myopia group lost two lines of best corrected visual acuity, although 12% in the astigmatism group did. CONCLUSION: The Coherent-Schwind excimer laser appears to be effective in the treatment of low myopia and astigmatism, with results comparable to those of other laser systems after 6 months of follow-up. Further study of best corrected visual acuity loss after treatment of compound myopic astigmatism with this laser is warranted.

Adolescent↗
PubMed1997

Prospective, randomized vector analysis of astigmatism after three-, one-, and no-suture phacoemulsification.

PURPOSE: To compare surgically induced astigmatism and visual outcomes after three-, one-, and no-suture phacoemulsification. SETTING: Johns Hopkins Hospital, Baltimore, Maryland and Manhattan Eye, Ear, and Throat Hospital, New York, New York, USA. METHODS: This prospective, randomized study followed 131 patients treated with phacoemulsification with a 5.5 mm self-sealing scleral tunnel and implantation of a 5.5 mm poly(methyl methacrylate) posterior chamber lens. Radial 10-0 nylon sutures were used in the three- and one-suture groups. RESULTS: Mean astigmatism was greatest in the first postoperative week in all groups and stabilized after 8 weeks. The percentage of patients with with-the-rule (WTR) astigmatism increased from baseline in the one- and three-suture groups and decreased in the sutureless group. Mean uncorrected Snellen acuity was significantly better in the no- and one-suture groups than in the three-suture group at 1 week. There were no significant differences in uncorrected acuity at other times. No statistically significant differences in the surgically induced spherical equivalent were noted among the three groups during the 1 year follow-up. There was significantly less surgically induced keratometric astigmatism in the one-suture group at 4 (P = .03) and 8 (P = .007) weeks postoperatively. At all follow-ups, the sutureless group had the greatest proportion of patients, with significant ATR astigmatic shift (1 week, 17%; 4 weeks, 32%); and the lowest proportion of patients with significant WTR astigmatic shift (10% after 1 week). At 4 weeks, the percentage of patients with significant WTR shift in the one-suture group dropped to that in the sutureless group (10%); however, those in the one-suture group had less ATR astigmatic shift (16%). CONCLUSION: Sutureless and one-suture surgery resulted in a low percentage of WTR induced astigmatism 4 weeks postoperatively. Compared with sutureless surgery, the one-suture surgery resulted in less ATR shift.

Adult↗
PubMed1998

Astigmatic keratotomy effect of single-hinge, clear corneal incisions using various preincision lengths.

PURPOSE: To investigate the astigmatic keratotomy effect of a modified single-hinge cataract incision. SETTING: Department of Ophthalmology, San Juan de Dios Hospital, Tenerife, Spain. METHODS: This prospective study evaluated the astigmatic changes resulting from preincision grooves of less than 40, 45, and 55 degrees in arc length used with a single-hinge, self-sealing cataract incision in 144 eyes that had against-the-rule corneal astigmatism preoperatively. The intended 90% depth preincision was centered on the steep meridian and lengthened according to the amount of preoperative astigmatism. Outcome measurements were obtained by calculating the surgically induced astigmatism vectors and the postoperative keratometry changes 1 day, 1 week, and 1, 3, and 6 months after surgery. RESULTS: Three months postoperatively, astigmatism decreased by 0.03, 0.30, and 0.68 diopter in the less than 40, 45, and 55 degree incision length groups, respectively. The differences between the 45 and 55 degree groups and the less than 40 degree group was statistically significant (P < .05). Similar results were observed 6 months after surgery. CONCLUSION: The astigmatic preincision modification produced statistically significant increasing reductions in preoperative astigmatism according to preincision length.

Aged↗
PubMed1998

Photorefractive keratectomy for astigmatism greater than -2.00 diopters in eyes with low, high, or extreme myopia.

PURPOSE: To assess the efficacy of excimer laser photorefractive astigmatic keratectomy (PARK) in correcting astigmatism of more than -2.00 diopters (D) in eyes with low, high, and extreme myopia. SETTING: Pusan National University Hospital, Pusan, Korea. METHODS: Eighty-five patients (110 eyes) whose spherical error ranged from -3.00 to -13.00 D and cylinder ranged from -2.00 to -5.50 D had PARK with a VISX Twenty-Twenty excimer laser; follow-up was 6 months. All cases of myopic astigmatism were treated using the elliptical method and multizone ablation technique. Eyes were divided into 3 groups: low myopia, less than 6.00 D (n = 47); high myopia, from 6.25 to 10.00 D (n = 43); extreme myopia, over 10.25 D (n = 20). Alpins vector analysis was used to calculate the astigmatic change. RESULTS: By vector analysis, the success rate of astigmatic correction was more predictable in the low and high myopia groups than in the extreme myopia group (P < .05). There was little improvement in astigmatism in the extreme myopia group. CONCLUSION: Using PARK to correct astigmatism greater than -2.00 D in eyes with myopia less than -10.00 D tended to result in undercorrection; astigmatic correction in eyes with myopia over 10.25 D was minimal.

Adult↗
PubMed1998

Comparison of surgically induced astigmatism after sutureless temporal clear corneal and scleral frown incisions.

PURPOSE: To compare the corneal astigmatic changes induced by clear corneal incisions with those induced by scleral tunnel frown incisions., both from a temporal approach, in sutureless cataract surgery. SETTING: Department of Ophthalmology, College of Medicine, National Cheng Kung University, Tainan, Taiwan, Republic of China. METHODS: This prospective study comprised 120 eyes divided into two groups of 60 each based on incision type. All patients had examinations with an autokeratometer preoperatively and 1 week and 1, 3, and 6 months postoperatively. RESULTS: Simple subtraction of the scalar analysis in each group showed minimal astigmatic changes; however, the standard deviation of astigmatic change was greater in the clear corneal incision group. The mean vector analysis of surgically induced astigmatism in the scleral frown incision group was 0.;69, 0.75, 0.72, and 0.61 diopter (D) at 1 week and 1, 3, and 6 months, respectively. In the clear corneal incision group, it was 1.55, 1.12, 0.93, and 0.92 D at the same intervals. In the scleral frown incision group, Naeser's polar value also showed minimal changes in polar astigmatism throughout the study; in the clear corneal incision group, it showed a mean with-the-rule (WTR) astigmatic shift of +0.73, +0.22, +0.13, and +0.08 D at 1 week and 1, 3, and 6 months, respectively. CONCLUSION: Corneal stability was achieved with minimal astigmatic change 1 week after scleral frown incisions, while clear corneal incisions induced greater WTR astigmatism with delayed stabilization 1 to 3 months postoperatively.

Aged↗
PubMed1999

Effect of collagen implants in the reduction of high astigmatism induced by penetrating keratoplasty.

PURPOSE: To evaluate the insertion of EagleVision collagen plugs as spacers between corneal relaxing incisions to correct significant residual astigmatism after penetrating keratoplasty (PKP). SETTING: Ambulatory Clinic of the Department of Ophthalmology, Rhode Island Hospital, and Rhode Island Eye Institute, Providence, Rhode Island, USA. METHODS: This study comprised 8 patients meeting the following criteria: had previous PKP, had at least 5.0 diopters of residual keratometric astigmatism with all the sutures removed, were free from eye infection, and were at least 21 years old. All 8 patients had unilateral high astigmatism after PKP. Four eyes were randomly assigned to the control group of astigmatic keratectomy (AK) incisions without the collagen implants and 4 eyes to the experimental group of AK incisions with collagen implants. RESULTS: Best corrected visual acuity 1 day, 3 weeks, and 1, 2, and 6 months after AK showed decreased astigmatism in all the patients who had the relaxing incisions. The amount of astigmatism was lower in patients who received AK incisions with collagen implants (P < .28). Minimal adverse effects were noted. CONCLUSION: Implanting a biocompatible material into AK incisions to correct post-PKP astigmatism appears to be safe and may enhance astigmatic correction.

Adult↗
PubMed2003

Astigmatic axis and amblyopia in childhood.

PURPOSE: This study is part of a larger project whose aim is to evaluate the relationship between refractive errors and amblyopia. In an earlier study, we showed that there is a substantial increase in the prevalence of amblyopia among children with oblique astigmatism. To further evaluate this relationship, we examined children with astigmatisms of 1 dioptre or more and varying directions of the astigmatic axes. METHODS: Two groups of astigmatic children, with oblique and orthogonal astigmatism, respectively, were selected for the study at 1 year of age via a general health screening programme. The most emmetropic axis was identified in each child and used in the study. Visual acuity (VA) was tested when the children were between 4 and 4.5 years of age. The presence of amblyopia, defined as difference in VA between the eyes of 0.1 log unit or more, and any increase in acuity following occlusion therapy were noted. RESULTS: The angle of the astigmatic axis strongly relates to the risk of developing amblyopia. Axes +/- 15 degrees from the main axes did not affect the risk of amblyopia but oblique astigmatism significantly increased the risk of developing amblyopia (p = 0.0024). CONCLUSIONS: The results accord with earlier findings that oblique astigmatism increases the risk of developing amblyopia.

Amblyopia↗
PubMed2001

Peripheral astigmatism in emmetropic eyes.

The long-term aim of the work introduced here is to investigate the influence of off-axis aberrations on human vision, especially for subjects with a large central scotoma. The latter use their peripheral vision in spite of its poor off-axis optical quality, and a correction of the off-axis aberrations might be of great assistance. The eccentric fixation angles used by these subjects can be up to 20-30 degrees. In this initial study we have measured oblique astigmatism, the major off-axis aberration, in 20 emmetropic eyes in 10 degrees steps out to 60 degrees nasally and temporally using a 'double pass' setup. The results show very large individual differences and the oblique astigmatism also varies from nasal to temporal side. In an off-axis measurement angle of 30 degrees the astigmatism varied between subjects from 1 to 7-D, with a mean astigmatism of about 4-D on the nasal side and about 1.5-D lower on the temporal side. At 60 degrees temporally, the mean astigmatism was 7-D. At 60 degrees nasally, all subjects had astigmatism larger than 8-D and the mean astigmatism was 11-D. The results indicate that any attempt to correct the off axis astigmatism in an eye with central scotoma cannot be based on central refraction; instead, individual measurements are necessary.

Adult↗
PubMed2004

[Cataract surgery with implantation of toric silicone lenses for severe astigmatism after keratoplasty].

BACKGROUND: The treatment of high astigmatism after keratoplasty is often not possible with glasses or refractive corneal surgery, particularly in patients with anisometropia and contact lens incompatibility. METHODS: In 3 patients with cataract and high astigmatism after penetrating keratoplasty, phacoemulsification was performed via a 4 mm sclerocorneal tunnel incision. A toric silicone lens with Z-haptic was implanted in the bag (Type MS 6116 TU, Dr. Schmidt). All patients had high anisometropia and contact lens incompatibility. The follow-up was ten weeks, uncorrected and corrected visual acuity, corneal and total astigmatism were evaluated. RESULTS: A 68-year-old female presented with corneal astigmatism of 10 dpt. Keratoplasty was performed two years earlier. After implantation of a toric lens (+ 22.5 + 11.0 dpt.) uncorrected visual acuity increased from 1/50 to 20/40, corrected visual acuity increased from 20/30 to 20/25. A 78-year-old male presented with irregular corneal astigmatism of 6.5 dpt. Keratoplasty was performed 25 years previously. Due to high myopia (corneal radii 5.3/5.9 mm), implantation of a toric lens (- 3.0 + 7.0 dpt.) in the bag was combined with implantation of a spheric lens (- 6.0 dpt., Type MS 614, Dr. Schmidt) in the sulcus. Uncorrected visual acuity increased from light perception to 1/20, corrected visual acuity increased to 1/10. An 84-year-old female presented with irregular corneal astigmatism of 8.6 dpt. Keratoplasty was performed two years earlier. After implantation of a toric lens (+ 16.0 + 11.0 dpt.) uncorrected visual acuity increased to 20/50, corrected visual acuity increased from 20/100 to 20/25. During the follow-up all implanted lenses were well-centered and no significant IOL rotation was observed. CONCLUSION: Implantation of foldable toric silicone lenses during cataract surgery may improve considerably the uncorrected visual acuity by reducing the total astigmatism in patients with high astigmatism after keratoplasty. Preoperatively, a reliable keratometry is important.

Aged↗
PubMed2003

Relationship between the axis and degree of high astigmatism and obliquity of palpebral fissure.

PURPOSE: To investigate a possible relationship between the slanting of palpebral fissures and the magnitude and axis of astigmatism in children with astigmatism. METHODS: Cross-sectional study at a referral center of 53 children with astigmatism of more than +1.50 D in at least 1 eye. Visual acuity testing, cycloplegic refraction, slit-lamp biomicroscopy, and ophthalmoscopy were done on every patient. Corneal topography was obtained in 40 cooperative patients. External photographs of the midface were taken in 45 children. The degree of slanting of the palpebral fissures was evaluated based on the photographs. The statistical analysis tool used was repeated measures analysis of variance. Patients in whom photographic analysis was not available were excluded from the part of the statistical analysis dealing with eyelid slant. RESULTS: Palpebral fissure slant (P =.013) and gender (P =.0005) were highly correlated with the obliquity of cylinder axis. There was a possible correlation between gender and eyelid slant (P =.0594), with females having slightly larger degrees of upward palpebral fissure slanting and male more downward slanting of their fissures compared to published angles in an age-matched population. We found a statistically significant correlation between the degree of total astigmatism and a larger abnormal slant (P =.0192) and between the axis and magnitude of corneal astigmatism and abnormal slant (P =.0092). Higher degrees of eyelid slant (> 8 degrees or < -4 degrees ) increased the risk of high cylinder magnitude (> 3.00 D) by an odds ratio of 4.17 (95% CI: 1.03, 19.95). CONCLUSIONS: Children with astigmatism with large degrees of slanting of their palpebral fissures are at higher risk for high astigmatism (> 3.00 D). The axis of the astigmatism is highly correlated with the slanting of the palpebral fissure.

Adolescent↗
PubMed1993

Clinical and anatomical study of the effect of transscleral fixation of posterior chamber lenses on early postkeratoplasty astigmatism.

We reviewed the pattern of astigmatism after penetrating keratoplasty and transsclerally sutured posterior chamber lens (TSPCL) placement in 73 patients. Thirty-five patients (48%) had an axis of astigmatism oriented perpendicularly to the haptics of the TSPCL. Twenty-seven patients (37%) had an orientation of astigmatism that was in the same meridian of the haptics of the TSPCL. Eleven patients (15%) had an axis of astigmatism oriented obliquely to the meridian of the haptics of the TSPCL. The distance the haptic fixation sutures were placed behind the limbus appeared to be correlated with the orientation of astigmatism. Patients having the lens fixated within 0.75 mm of the limbus were more likely to have astigmatism oriented perpendicular to the meridian of the haptics of the posterior chamber lens in the early postoperative period. Patients having the lens fixated 2-3 mm posterior to the limbus were more likely to have astigmatism oriented in the same meridian as the haptics of the posterior chamber lens in the early postoperative period. In an eye bank model of TSPCLs during penetrating keratoplasty, the placement of a posterior chamber lens with haptics fixated within 0.75 mm of the limbus significantly widens the recipient bed an average of 0.3 mm in the meridian of the haptics of lens placement (p = 0.02). When the posterior chamber lens haptics were fixated 3 mm posterior to the limbus, the recipient bed was significantly narrowed in the meridian of lens placement an average of 0.2 mm (p = 0.02). It appears that the TSPCLs may have an effect on early postkeratoplasty astigmatism by distorting the corneal wound at the time of keratoplasty.

Aged↗
PubMed1999

Quantitative analysis of regular and irregular astigmatism induced by pterygium.

PURPOSE: To quantitatively evaluate the influence of pterygium and its removal surgery on both regular and irregular corneal astigmatism. METHODS: In 19 eyes of 19 patients undergoing pterygium surgery, videokeratographic measurements were taken before and 1 month after surgery. Using Fourier harmonic analysis, dioptric data on mire rings were decomposed into spherical, regular astigmatism, and irregular astigmatism (decentration and higher order irregularity) components. The distance between the line of sight and the advancing edge of pterygium was measured, and the eyes were classified into two groups: large pterygium group (the distance <2.0 mm, n = 7) and small pterygium group (> or =2.0 mm, n = 12). Fifteen eyes of 15 subjects served as age-matched normal control eyes. RESULTS: Before surgery, the magnitudes of regular astigmatism and higher order irregular astigmatism showed significant correlation with the size of pterygium. Regular astigmatism, asymmetry, and higher order irregularity in the large pterygium group were significantly greater than those of normal control eyes. The pterygium removal surgery significantly improved these changes, but regular astigmatism and higher order irregularity in the large pterygium group still remained significantly greater than those in the normal control eyes. CONCLUSION: Pterygium induces a significant amount of regular and irregular astigmatism in proportion to its size. The removal surgery can improve these changes, but corneal distortion does not normalize completely in eyes with advanced pterygium.

Aged↗
PubMed1986

Astigmatism occurring in association with pediatric eye disease.

Retrospective clinical data from 496 eyes of 256 children attending a low vision clinic were analyzed to determine the relation between different classes of disease that involve visual image degradation and astigmatism. Control data comprised refractions from 79 normal vision children. Children were classified into groups according to the category of disease (14 groups) and the reported age-of-onset of their visual disability (0 to 13 years, 5 groups). The mean astigmatism for all groups of children with low vision was larger than that of the normals and in most cases the difference was significant at the 95% level. Astigmatism was highest in children with albinism, retinitis pigmentosa, and idiopathic nystagmus. Increased prevalence of astigmatism compared to normals was noted in children having their onset of low vision as late as 13 years of age. In the low vision subjects with-the-rule astigmatism occurred more frequently than oblique or against-the-rule astigmatism and oblique astigmatism more frequently than against-the-rule astigmatism.

Adolescent↗
PubMed2002

Astigmatism and LASIK.

Although laser in situ keratomileusis (LASIK) enjoys a high success rate, postoperative residual or induced astigmatism may limit uncorrected visual acuity and cause starbursts and glare at night. Irregular astigmatism can also cause loss of best-corrected visual acuity, monocular diplopia, and ghosting of images. Astigmatism may be measured by keratometry and refraction, while corneal topographic techniques help to define irregular astigmatism, in particular. Further information may be obtained regarding induced higher-order aberrations with aberrometry. Because astigmatism has both direction and magnitude, its analysis is more complex than that of the spherical component of the treatment. There are multiple approaches to the analysis of surgically induced astigmatism, including vector analysis, conversion to a Cartesian coordinate system, matrix formalism, and linear optics. Both excimer laser and incisional techniques may be used to correct astigmatism after LASIK, but the treatment of irregular astigmatism requires selective zonal ablation techniques or customized corneal ablations, using topographic or wavefront derived data.

Astigmatism↗
PubMed2006

Prevalence of high astigmatism, eyeglass wear, and poor visual acuity among Native American grade school children.

PURPOSE: The purpose of this study was to examine the prevalence of astigmatism and poor visual acuity and rate of eyeglass wear in grade school children who are members of a Native American tribe reported to have a high prevalence of large amounts of astigmatism. METHODS: Vision screening was conducted on 1,327 first through eighth grade children attending school on the Tohono O'odham Reservation. Noncycloplegic autorefraction was conducted on the right and left eye of each child using the Nikon Retinomax K+ autorefractor, and monocular recognition acuity was tested using ETDRS logarithm of the minimum angle of resolution (logMAR) letter charts. RESULTS: Tohono O'odham children had a high prevalence of high astigmatism (42% had > or = 1.00 D in the right or left eye) and the axis of astigmatism was uniformly with-the-rule. However, only a small percentage of children arrived at the vision screening wearing glasses, and the prevalence of poor visual acuity (20/40 or worse in either eye) was high (35%). There was a significant relation between amount of astigmatism and uncorrected visual acuity with each additional diopter of astigmatism resulting in an additional 1 logMAR line reduction in visual acuity. CONCLUSIONS: Uncorrected astigmatism and poor visual acuity are prevalent among Tohono O'odham children. The results highlight the importance of improving glasses-wearing compliance, determining barriers to receiving eye care, and initiating public education programs regarding the importance of early identification and correction of astigmatism in Tohono O'odham children.

Adolescent↗