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PubMed1997

Corneal astigmatism in preschool Native Americans.

BACKGROUND: Native Americans tend to have high amounts of corneal and refractive with-the-rule astigmatism. This condition is reported to be of recent onset. Astigmatism has been shown to be prevalent in preschool-age children but, because of the process of emmetropization, this condition generally disappears by school age. Navajo children have been shown, however, to enter first grade with high mean amounts and high prevalence of with-the-rule astigmatism. This study was undertaken to ascertain whether with-the-rule astigmatism decreased in Navajo preschool children as they grew older. METHODS: Cross-sectional keratometric data were gathered on 250 preschool Navajo children from three states in the four corners district of the Navajo nation. RESULTS: High mean amounts of with-the-rule corneal astigmatism are prevalent at each age represented in this study. Girls have steeper corneas and more astigmatism than boys. Although the steepness of the corneal curve generally decreases slightly but significantly with age, the calculated astigmatism does not. The steepness of corneas also appears to vary by geographical area of residence within the Navajo nation. CONCLUSIONS: Emmetropization, with respect to the disappearance of astigmatism, does not appear to take place among the Navajo as it does in either Caucasian or Asian preschool-age children.

Astigmatism↗

PubMed1997

Distribution of astigmatism among Sioux Indians in South Dakota.

BACKGROUND: Previous studies have reported a greater prevalence of high astigmatism and vision disorders among Native Americans than occurs in the general U.S. population. The majority of these studies, however, have focused on Native American schoolchildren. This study assessed the distribution of astigmatism in a general clinic population at the Rosebud Indian Reservation in South Dakota. METHODS: From examination of 174 patients, demographic information, visual acuities, refractive error, binocular vision status, and eye health were recorded. RESULTS: The data showed more high astigmatism than would be expected in a general U.S. population. Three or more diopters of astigmatism were found in 9.2% of the right eyes and 10.8% of the left eyes in the study population. High astigmatism was noted less frequently among those ages 40 years and older (3.3% right eyes, 6.3% left eyes). Most of the astigmatism was with-the-rule, but a shift toward against-the-rule and oblique astigmatism was found in older individuals. No significant gender differences were noted. CONCLUSIONS: The results suggest an ethnic difference in astigmatism and emphasize thee need for continued and expanded vision services for Native American populations.

Adolescent↗

PubMed1997

[Surgery in myopic astigmatism: arciform keratotomy and PKR versus PARK].

UNLABELLED: Two surgical techniques for treatment of myopic astigmatism are compared: One technique is a combined procedure with relaxing incision and photorefractive keratectomy (RI PRK), the other one is photoreactive keratectomy done for correction of myopia and astigmatism (PARK). Fifty-nine eyes (42 patients) were operated by IR PRK. The preoperative myopia was between -1.5 and -14 D and the astigmatism between -0.75 and -6 diopters. Thirty-two eyes (20 patients) were treated with the PARK. The preoperative myopia was between -1 and -15 D and the astigmatism between -0.5 and -4. In 38 cases, relaxing incisions allowed to correct astigmatism entirely. The mean preoperative sphere of -6.8 D before PRK was 1.4 D and the spheres between -1 and -15 D. Twelve months after treatment, 26 eyes on 30 were spherical. The spherical equivalent varied between +0.75 and -1.50 D. Relaxing arciform incision presents the advantage to correct high asymmetric astigmatism without corneal thinning, as well as mixed astigmatism. At the present time, the PARK allows to correct only symmetrical myopic astigmatism. CONCLUSION: The predictability of the results is high if the cylinder is less than 3 D and the sphere less than 6 D. Beyond this limit, there is a higher risk of regression, and haze related with the depth of photo-ablation and we prefer RI-PRK.

Adult↗

PubMed1998

[Astigmatism after extracapsular cataract extraction with intraocular posterior lens implantation].

PURPOSE: To evaluate early and late astigmatism appearing after extracapsular cataract extraction with PC IOL implantation. MATERIAL AND METHODS: Astigmatism was examined in one hundred consecutive patients before operation and one week, 6 months and 12 months postoperatively. RESULTS: During the first week after surgery most patients (82%) had with the rule astigmatism, which decreased gradually from 3.95 D cyl (mean value) to 0.08 D cyl after a year. Against the rule astigmatism was present in 14% of cases and increased from 2.40 D cyl (mean value) to 3.07 D cyl in the same period of time. On the last examination 35% of patients didn't use any astigmatic correction. CONCLUSIONS: Traditional ECCE with PC IOLs causes postoperative astigmatism in most patients. Majority of them has with the rule astigmatism, which decreases gradually during the first postoperative year and may change into against the rule astigmatism.

Aged↗

PubMed1988

The effect of removing running sutures on astigmatism after penetrating keratoplasty.

To evaluate astigmatic change after removal of the double running sutures used in penetrating keratoplasty, all patients (N = 131) in the Michigan Corneal Transplantation Patient Registry, Ann Arbor, whose eyes were phakic after penetrating keratoplasty were evaluated. The primary reasons for surgery in this group were keratoconus (n = 44, 34%) and Fuchs' corneal dystrophy (n = 19, 15%). The average effect of 10-0 suture removal in 58 eyes with documented keratometry readings was a 0.30-diopter (D) decrease in astigmatism, with 59% showing 2 D or less of astigmatic change. In 83 eyes with keratometry readings before and after 11-0 suture removal, an average increase of 0.37 D of astigmatism was observed, with 81% showing less than 2 D of astigmatic change. In eyes that were highly astigmatic (greater than 6 D) before suture removal, a reduction in astigmatism exceeding 2 D was observed in 39% and 11% after 10-0 and 11-0 suture removal, respectively.

Astigmatism↗

PubMed1991

Trapezoidal keratotomy for the correction of naturally occurring astigmatism.

We performed trapezoidal keratotomy, consisting of combined nonintersecting semiradial and transverse incisions, in 64 eyes of 45 consecutive patients with naturally occurring astigmatism. The central clear zone diameter and number and length of transverse incisions were determined by the refractive error. Mean preoperative refractive astigmatism was 3.18 +/- 1.16 diopters (D) (range, 2.25 to 7.00 D). At the 1-year follow-up examination, the mean surgically corrected astigmatism determined by vector analysis was 3.70 +/- 1.50 D (range, 0.75 to 8.5 D), and the mean residual refractive astigmatism was 0.85 +/- 0.72 D (range, 0 to 4.0 D), with 64% of eyes having 1.00 D or less. The smaller the clear zone diameter, the greater the astigmatic correction. Longer transverse incisions produced more steepening of the secondary meridian. The operative complications included microperforation (5%), misalignment of surgical meridian (6%), encroachment on clear zone (5%), and inadvertent crossed incisions (11%). Trapezoidal keratotomy reduced naturally occurring astigmatism, but with only fair predictability and with some irregular astigmatism due to irregular wound healing.

Adolescent↗

PubMed1998

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

BACKGROUND: 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. PATIENTS AND METHODS: In a prospective study in 342 eyes the results of myopic PRK were compared to those of correction of compound myopic astigmatism (PARK). RESULTS: 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. CONCLUSIONS: 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.

Adult↗

PubMed1988

The effect of suture removal on postkeratoplasty astigmatism.

I followed up for a minimum of six months 439 eyes that had undergone corneal transplantation using a suturing technique consisting of eight interrupted 10-0 and a single, continuous, 16-bite 11-0 nylon suture. All sutures were removed from 188 eyes an average of 20 months after surgery. After suture removal, 64 corneas had an increase of astigmatism greater than 0.5 diopter, 79 eyes showed a decrease in astigmatism greater than 0.5 diopter, and 42 corneas had no change in astigmatism. The mean astigmatism before suture removal was 3.7 diopters, and the mean astigmatism after suture removal was 3.5 diopters. There was no apparent difference in postkeratoplasty astigmatism with donor corneal diameters 0.25 to 0.75 mm greater in diameter than the recipient diameters, or with different host diseases. The longer the sutures were left in place after surgery, the smaller the quantitative change in astigmatism after suture removal. The complications of this technique were no different from other currently used suture techniques.

Astigmatism↗

PubMed2005

Repeat keratoplasty for correction of high or irregular postkeratoplasty astigmatism in clear corneal grafts.

PURPOSE: To evaluate the functional results of repeat penetrating keratoplasty in clear corneal grafts with high/irregular postkeratoplasty astigmatism. DESIGN: Retrospective, longitudinal, single-center, consecutive clinical case series. METHODS: We studied 17 eyes (16 keratoconus, 1 Fuchs' dystrophy) of 16 patients (age, 54.9 +/- 12.6 years). They were treated with repeat PK, performed using the 193-nm Zeiss-Meditec MEL-60 excimer laser using round metal masks (diameter, 7.5-8.0 mm), and employing double running sutures. main outcome measures: Subjective refractometry, standard keratometry, and corneal topography (Tomey TMS-1) were used to assess best-corrected visual acuity (BCVA), spherical equivalent (SEQ), keratometric and topographic central corneal power (CP), refractive, keratometric and topographic astigmatism, surface regularity index (SRI), surface asymmetry index (SAI), and potential visual acuity (PVA) preoperatively, before and after first suture removal (1.1 year), and after second suture removal (1.8 years). RESULTS: Visual acuity improved significantly (BCVA from 0.2-0.5, P = .04 or better) for all postoperative measurements. CP decreased significantly, but SEQ did not change. All measures of astigmatism and SRI and SAI values showed postoperative improvement with sutures in place; however, astigmatism increased significantly after second suture removal. CONCLUSIONS: With all-sutures-in, BCVA and astigmatism improve significantly after repeat PK for high/irregular astigmatism. However, to present significant increase in astigmatism, final suture removal should be postponed as long as possible in such eyes.

Adult↗

PubMed2004

Corneal aberrations after astigmatic keratotomy combined with laser in situ keratomileusis.

PURPOSE: To evaluate the optical aberrations in the cornea before and after astigmatic keratotomy (AK) combined with laser in situ keratomileusis (LASIK) in a group of patients with high myopic astigmatism. SETTING: Refractive Surgery Unit, NISA Hospital Virgen del Consuelo, Valencia, Spain. METHODS: Twelve patients (24 eyes) with high myopic astigmatism (from 3.50 to 6.00 diopters) participated in the study. Astigmatic keratotomy was performed as the first step to reduce astigmatism; after 2 months, the residual refractive error was corrected with LASIK. Videokeratography measurements were conducted before and after each procedure. Topography maps were used to calculate the wavefront corneal aberrations for a 6.0 mm pupil diameter. RESULTS: Total, coma-like, and spherical-like aberrations increased significantly from preoperatively to post LASIK (x6.34, x2.52, and x10.50, respectively; P<.01). Astigmatic keratotomy significantly increased coma-like (x4.04; P<.01) and spherical-like (x5.66; P<.01) aberrations. After LASIK, the coma-like aberration was significantly reduced (x0.62; P =.008) and the spherical-like aberration was significantly increased (x1.86; P<.01). CONCLUSION: Astigmatic keratotomy increased higher-order corneal aberrations, both coma-like and spherical-like, whereas LASIK performed after AK increased the spherical-like aberration and reduced the coma-like aberration.

Adult↗

PubMed2005

Paired opposite clear corneal incisions to correct preexisting astigmatism in cataract patients.

PURPOSE: To evaluate the astigmatic correcting effect of paired opposite clear corneal incisions on steep axis in cataract patients. SETTING: Sligo General Hospital, Sligo, Ireland. METHODS: Fifteen eyes of 14 cataract patients with a mean age of 78.4 years +/- 6.38 (SD) (range 69 to 90 years) were recruited for the study. Inclusion criterion was topographic astigmatism of more than 2 diopters (D) in the cataractous eye. Preoperative refraction, autokeratometry, and topography were performed. The steep axis was marked before sub-Tenon's anesthesia was given. Paired 3-step self-sealing opposite clear corneal incisions were made 1 mm anterior to limbus on the steep axis with a 3.2 mm keratome. One incision was used for standard phacoemulsification, and the other was left unused for astigmatic correction. All the patients had day-case surgery. The first follow-up was at 1 month. Postoperative topography, keratometry, and refraction were performed on all patients. RESULTS: Mean preoperative and postoperative topographic corneal astigmatism were 3.26 +/- 1.03 D (range 2.30 to 5.80 D) and 2.02 +/- 1.04 D (range 0.20 to 4.00 D), respectively. Mean astigmatic correction was 1.23 +/- 0.49 D (range 0.30 to 2.20 D). Mean surgically induced astigmatism by vector analysis was 2.10 +/- 0.79 D (range 0.80 to 3.36 D). There were no incision-related complications. CONCLUSION: Paired opposite clear corneal incisions on the steep axis is a useful way to correct astigmatism in cataract patients, requiring no extra skill or instrumentation.

Aged↗

PubMed2006

Toric phakic intraocular lens for the correction of hyperopia and astigmatism.

PURPOSE: To evaluate the Artisan toric phakic intraocular lens (pIOL) for the correction of hyperopia and astigmatism. SETTING: Department of Ophthalmology, Erasmus MC, Rotterdam, The Netherlands, and Department of Ophthalmology, Sint Truiden, Belgium. METHODS: In this prospective study of 47 eyes of 28 patients with hyperopia and astigmatism, Artisan toric pIOLs were implanted between April 1999 and June 2004. Uncorrected visual acuity (UCVA), best corrected visual acuity, refraction, astigmatism, safety, and predictability were analyzed. Change in astigmatism was analyzed with vector analysis. Refractive cylinders are expressed in minus form. RESULTS: Mean preoperative spherical equivalent was +4.33 diopters (D) +/- 2.26 (SD). Mean follow-up was 11.1 months (range 6 to 36 months). A gain of 1 or more lines in best spectacle-corrected visual acuity (BSCVA) was seen in 36.2%. Safety index and efficacy index after 6 months were 1.06 and 0.87, respectively. The mean postoperative astigmatism at 6 months was 0.19 D at an axis of 144 degrees. At 6 months, about three quarters (76.6%) of the eyes had a UCVA of 20/40 or better. One eye lost 2 lines of BSCVA. In 1 eye, the lens position had to be changed because of a large axis misalignment. No serious complications developed in any of the treated eyes during follow-up. CONCLUSIONS: Artisan toric pIOLs can correct moderate to high hyperopia combined with astigmatism with good refractive results. In this study, there were no serious complications. However, the predictability of the refractive results appeared to be lower than those in the correction of myopia and astigmatism with toric Artisan lenses.

Adult↗

PubMed2006

Correction of post-keratoplasty astigmatism with keratotomies in the host cornea.

We evaluated the effects of astigmatic keratotomy performed in the host cornea to treat astigmatism after penetrating keratoplasty. In 11 patients with high post-keratoplasty astigmatisms (mean 9.02 diopters [D]; range 5.5 to 17.4 D), an arcuate keratotomy was performed in the host cornea. The mean incision depth was 575 mum (range 500 to 600 mum). The refractive data were analyzed using the Alpins method for vector analysis. The mean keratometric cylinder decreased to 3.41 D (range 0.9 to 5.3 D). The mean surgically induced astigmatism achieved was 7.3 +/- 3.89, with a mean correction index of 0.82 +/- 0.34. No microperforations were observed, and neither graft decompensation nor rejection occurred. Astigmatic keratotomy performed in the host cornea was a safe procedure to reduce post-keratoplasty astigmatism. The procedure offers the potential for correction of the astigmatism and has satisfactory predictability.

Astigmatism↗

PubMed2001

The effects of astigmatism and working distance on optic nerve head images using a Heidelberg Retina Tomograph scanning laser ophthalmoscope.

PURPOSE: To determine effects of astigmatism and working distance on optic nerve head images in normal patients using the Heidelberg Retina Tomograph. METHODS: The optic disks of 51 normal healthy subjects, aged 19 to 44 years, were imaged through dilated pupils. Subjects with 0.75 DC or less of astigmatism were imaged without correction at a working distance of 15 mm. They were then re-imaged with a cylindrical correction of +3.00 DC at 90 degrees axis (n = 20). Naturally astigmatic subjects with more than 1.00 DC were imaged without correction and then re-imaged once this was neutralized with their appropriate spectacle prescription (n = 15). The effects of working distance were studied using subjects with 0.75 DC or less (n = 16). Two working distances were used, 15 and 25 mm. At each session the means of three topographic images were taken from which standard deviations and parameters were recorded. Parameters analyzed included cup shape measure, rim area, and inferior temporal rim volume. Z-profile full width at half maximum was calculated from one image per subject for each condition. RESULTS: No significant difference was found in the measured parameters of the optic disk for any astigmatic condition or changes in working distance (P >.05), (paired t test). Both the standard deviation of the mean topographic images and the Z-profile half-maximum width of the axial intensity profile were significantly greater with induced astigmatism of +3.00 DC (P values 0.3 and.00, respectively). CONCLUSIONS: Optic disk parameters are not significantly affected by uncorrected astigmatism (up to 2.50 DC) or working distance. The algorithm used by the Heidelberg Retina Tomograph to generate topographic maps is sufficiently robust that astigmatism up to 2.50 DC does not require correction.

Adult↗

PubMed1994

Randomized clinical trial comparing astigmatism and visual rehabilitation after penetrating keratoplasty with and without intraoperative suture adjustment.

PURPOSE: The authors performed a prospective, randomized clinical trial to compare postoperative astigmatism and visual rehabilitation after penetrating keratoplasty with and without intraoperative suture adjustment. METHODS: Twenty-five patients undergoing penetrating keratoplasty for avascular corneal pathology randomly were assigned to two groups. All surgery was performed by one surgeon (ONS) using the same technique (except for intraoperative suture adjustment) with Hanna trephination (8 mm) and a running 10-0 nylon suture. Postoperative suture adjustment was done during the first postoperative month in all patients who had more than 3.5 diopters of astigmatism. Refraction and computerized topographic analysis were performed at 1 and 6 months postoperatively. RESULTS: Intraoperative suture adjustment significantly decreased postkeratoplasty topographic (P = 0.0001) and refractive (P = 0.0001) astigmatism and improved best spectacle-corrected visual acuity (P = 0.0019) during the first postoperative month. Seventy-seven percent of control patients (mean topographic astigmatism, 4.89 +/- 1.99 D at 1 month), but no patients who underwent intraoperative suture adjustment (mean topographic astigmatism, 1.50 +/- 0.74 D at 1 month), required at least one postoperative suture adjustment that delayed optical stability and increased postoperative complications. At 6 months postoperatively, mean topographic (P = 0.06) and refractive (P = 0.0001) astigmatism were smaller in the intraoperatively adjusted group than in the control group with postoperative suture adjustments. After intraoperative adjustment, best spectacle-corrected visual acuity was better (P = 0.0168, P = 0.0434) and corneal topography was more regular (P = 0.02, P = 0.07, NS) at 1 and 6 months, respectively, than after postoperative adjustment. CONCLUSION: Visual rehabilitation with decreased postkeratoplasty astigmatism and more regular corneal topography was attained more rapidly and safely with intraoperative suture adjustment.

Adult↗

PubMed2001

Surgically induced astigmatism after implantation of intacs intrastromal corneal ring segments.

PURPOSE: To analyze surgically induced astigmatism (SIA) after implantation of Intacs intrastromal corneal ring segments. SETTING: Multicenter clinical trials in the United States. METHODS: Data from 11 investigational sites involved in the Phase II and III trials of Intacs for the United States Food and Drug Administration were retrospectively analyzed. The distribution of Intacs thicknesses implanted in 449 eyes was 0.25 mm in 148 eyes, 0.30 mm in 151 eyes, and 0.35 mm in 150 eyes. Refractive astigmatism was measured by subjective manifest refraction preoperatively and 1 week and 1, 2, 3, 6, 9, and 12 months postoperatively. The mean simple change in astigmatism and the surgically induced refractive change were determined by vector analysis. RESULTS: Mean induced astigmatism at 12 months was 0.13 diopter (D) +/- 0.52 (SD). Induced astigmatism was more frequently with the rule (44%) than against the rule (26%) or oblique (30%). Maximal mean astigmatism was 0.50 +/- 1.09 D and occurred at 7 days. Mean induced astigmatism increased with segment thickness (0.01 D, 0.17 D, and 0.21 D for the 0.25 mm, 0.30 mm, and 0.35 mm segments, respectively). Mean surgically induced refractive change in cylinder power in all eyes at 12 months by vector analysis was 0.17 D x 92. CONCLUSION: Mean SIA was not clinically meaningful 12 months after Intacs implantation.

Adult↗

PubMed2003

Postoperative astigmatism and rotational stability after artisan toric phakic intraocular lens implantation.

PURPOSE: To evaluate deviations in the axis (intended versus achieved) and postoperative astigmatism after implantation of an Artisan toric phakic intraocular lens (IOL). SETTING: University Eye Hospital, Mainz, Germany. METHODS: This prospective study comprised 29 eyes with high ametropia and astigmatism. All eyes had uneventful implantation of a toric phakic IOL through a superior scleral tunnel incision at 12 o'clock. After a minimum of 6 months, the uncorrected visual acuity (UCVA), best correct visual acuity, refraction, and astigmatism were analyzed in all eyes. A multivariate analysis of postoperative astigmatism was performed. RESULTS: After a follow-up of at least 6 months, 95% of eyes were within +/-1.00 diopter (D) of emmetropia and 85% of eyes has a UCVA of 20/30 or better. The difference between the mean intended cylinder axis and achieved cylinder axis was 3.9 degrees (median 3 degrees; range to 13 degrees). The difference between the mean intended axis and the achieved axis between miosis and mydriasis was 1.8 degrees (median 1.5 degrees; range 0 to 5 degrees). The mean postoperative astigmatism after 6 months was 0.56 D with an axis of 31 degrees. Doubled-angle scatterplot analysis showed a tendency toward more flattening in the vertical meridian. CONCLUSIONS: During the 6-month follow-up, no significant rotation was observed after implantation of Artisan toric phakic IOLs to correct high ametropia. A sutureless sclerocorneal superior approach for phakic IOL insertion resulted in moderate to low astigmatism. Induced astigmatism should be taken into consideration during preoperative planning.

Adult↗

PubMed1991

Natural history of corneal astigmatism after cataract surgery.

Little information on the natural course of corneal astigmatism following cataract surgery exists. We report a prospective, computerized analysis of postoperative astigmatism, based on keratometry measurements, of 137 cases of extracapsular cataract extraction with intraocular lens implantation performed by one surgeon. No sutures were cut postoperatively. Surgery induced 1.44 diopters (D) of with-the-rule astigmatism at one month, which declined at a rate of 0.77 D and 0.35 D per month for the next two months, respectively, with a more gradual decline thereafter. The mean surgically induced astigmatism at the last postoperative visit ranged from 0.29 D at six months (minimum follow-up) to 1.23 D at 48 months; both were against-the-rule. Mean follow-up was 28.92 months. These findings may be technique specific and suggest that (1) corneal curvature continues to change slowly even two to four years postoperatively; (2) most patients develop against-the-rule astigmatism, thus more with-the-rule astigmatism is desirable in the early postoperative period; (3) selective suture removal is necessary only when significantly more than 3.00 D of surgically induced with-the-rule astigmatism is present.

Aged↗