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PubMed1992

Transverse astigmatic keratotomy. An integral part of small incision cataract surgery.

Transverse astigmatic keratotomy (TAK) is used with an astigmatically neutral wound to control against-the-rule astigmatism. Previously both wound manipulation and TAK have been used to alter astigmatism, but with the advent of astigmatically neutral small incision surgery, astigmatism control involves TAK alone. This paper discusses the TAK approach to astigmatism control and includes a nomogram for incision size.

Astigmatism↗
PubMed1996

Astigmatism after phacoemulsification with adjusted and unadjusted sutured versus sutureless 5.2 mm superior scleral incisions.

PURPOSE: To evaluate changes in astigmatism in the first 6 months after 5.2 mm superior scleral incision phacoemulsification using three different closures. SETTING: Department of Ophthalmology, Vejle Hospital, Denmark. METHODS: This study comprised 75 consecutive patients who had 5.2 mm superior scleral incision phacoemulsification. Patients were randomly assigned to one of three groups based on type of incision closure: Group 1, one intraoperatively adjusted cross suture; Group 2, one unadjusted cross suture; Group 3, no suture. Inclusion criteria were preoperative astigmatism of 2.00 diopters (D) or less (range of median 0.74 to 0.81 D) and no eye disease except cataract. Postoperative astigmatism was evaluated by keratometric cylinder, induced astigmatism (Naeser), and induced cylinder (Jaffe) on the first day and after 1 week and 1, 3, and 6 months. Time before stability was estimated. RESULTS: All groups had the same level of postoperative keratometric cylinder with no significant change between 1 week and 6 months (range of median 0.81 to 1.06 D). The groups reached the same level of induced astigmatism (Naeser) 3 to 6 months after surgery (range of median -0.44 to -0.64 D). Group 3 (sutureless) reached that value after 1 week, and induced astigmatism was stable thereafter. Both sutured groups (Groups 1 and 2) had a highly significant change between the first week and third month (P < .01). There were no significant intergroup differences in induced cylinder (Jaffe), which stabilized after 1 week in Groups 1 and 2 and after 1 month in Group 3 (range of median 0.61 to 0.87 D). During the early postoperative period, variation was highest in Group 2. CONCLUSIONS: Keratometric cylinder, induced astigmatism, and induced cylinder 3 to 6 months postoperatively were similar among the three groups, but early stability was only seen in the sutureless group. If a suture is used, intraoperative adjustment seems to result in lower variations in the early postoperative period.

Aged↗
PubMed1996

Excimer laser correction of high astigmatism after keratoplasty.

PURPOSE: To assess the effectiveness of excimer laser correction of high astigmatism after keratoplasty. SETTING: Kiel University Eye Hospital, Kiel, Germany. METHODS: In a prospective study, we treated high astigmatism in 16 patients using a 193 nm excimer laser with a rotating mask system to make a toric ablation. Thirteen patients had postkeratoplasty astigmatism, 3, idiopathic natural astigmatism. Preoperative refractive cylinder ranged from 3.0 to 9.0 diopters (D). Minimum follow-up was 6 months. RESULTS: Mean uncorrected visual acuity increased by 3.3 lines in 13 patients. Best corrected visual acuity decreased by no more than two lines in 6 patients and improved by at least one line in 6 patients. Mean cylindrical reduction was 2.8 D. Haze was classified from 0.5 to 2.0. CONCLUSIONS: In this study, the excimer laser technique effectively reduced high corneal astigmatism. The main problems incurred were development of a hyperopic shift and, in some patients, an uncertain refractive outcome. Reasons for inadequate correction of postkeratoplasty astigmatism included a slightly decentered mask and irregular astigmatism from the circular scar.

Adolescent↗
PubMed1997

Noncorneal astigmatism related to poly(methyl methacrylate) and plate-haptic silicone intraocular lenses.

PURPOSE: To evaluate noncorneal astigmatism after implantation of a one-piece, plate-haptic silicone or one-piece poly(methyl methacrylate) PMMA intraocular lens (IOL). SETTING: Klinik und Poliklinik für Augenheilkunde der Universität Regensburg, Germany. METHODS: After a follow-up of at least 3 months, the degree of postoperative noncorneal astigmatism was calculated using the data from an auto refractometer. Sixty patients were evaluated: 30 with silicone IOLs (Group A) and 30 with PMMA lenses (Group B). RESULTS: Mean noncorneal astigmatism in Group A was 0.78 diopter (D) +/- 0.51 (SD), which was statistically significantly higher than that in Group B (0.51 +/- 0.27 D) (P = .013). The highest noncorneal astigmatism, 2.32 D, occurred in Group A. CONCLUSIONS: Based on these findings, we recommend noncorneal astigmatism be considered in eyes with a one-piece, plate-haptic silicone IOL and postoperative astigmatism. A prospective study with a standardized capsulorhexis size is needed to ascertain whether this IOL-related noncorneal astigmatism is caused by capsular shrinkage, which may then be treatable with a laser capsulotomy of the anterior capsule.

Aged↗
PubMedDate not supplied

Benefit of against-the-rule astigmatism to uncorrected near acuity.

PURPOSE: To determine whether with-the-rule (WTR) or against-the-rule (ATR) astigmatism gives a better visual outcome after cataract and intraocular lens (IOL) implantation surgery by comparing the uncorrected distance and near visual acuities in eyes with low, simple, myopic residual astigmatism. SETTING: S. Geraldo Eye Hospital, Federal University of Minas Gerais, Belo Horizonte, Brazil. METHODS: Two groups of 10 eyes each, one with WTR and the other with ATR simple, myopic astigmatism, were studied after uneventful cataract and IOL implantation surgery. All patients had an uncorrected distance visual acuity of 20/40 or better. The negative cylinder ranged from 1.00 to 1.50 diopters (D). The uncorrected distance and near visual acuities of the two groups were compared. RESULTS: There was no statistically significant between-group difference in uncorrected distance visual acuity. However, for uncorrected near, the difference between groups was highly statistically significant (P < .001). Patients with ATR astigmatism had much better uncorrected near acuity than those with WTR astigmatism. CONCLUSION: In pseudophakia, low, simple, ATR myopic astigmatism is better than WTR astigmatism because it provides superior uncorrected near visual acuity.

Aged↗
PubMed1997

Effect of incision location on preoperative oblique astigmatism after scleral tunnel incision.

PURPOSE: To evaluate the effect of incision location or clinically relevant preoperative oblique astigmatism. SETTING: Department of Ophthalmology, Virchow Medical Center, Humboldt-University, Berlin, Germany. METHODS: This prospective study included 68 patients who had phacoemulsification and posterior chamber lens implantation using a standardized 7.0 mm self-sealing trapezoidal scleral tunnel incision. Each patient was randomly assigned to one of three incision locations: Group A, conventional superior incision; Group B, temporal incision; Group C, oblique incision centered on the steeper meridian (modified BENT incision). Astigmatism analysis was performed by manual keratometry and corneal topography. RESULTS: A significant mean reduction in astigmatism of 0.58 diopter (D) (P < .01) was achieved in only the modified BENT incision group. Postoperatively, significant flattening of 0.27 D (P < .01) in the steeper meridian as well as steepening of 0.29 D (P < .01) in the flatter meridian occurred. No decrease in astigmatism was noted in the superior or temporal incision groups. Five months postoperatively, vector analysis showed that surgically induced astigmatism was significantly higher in the superior incision group (1.16 D +/- 0.44 [SD]) than in the temporal incision group (0.66 +/- 0.32 D) or modified BENT incision group (0.82 +/- 0.50 D). Corneal topographic analysis confirmed these results within +/- 0.3 D. CONCLUSIONS: Only the oblique incision centered on the steeper meridian (modified BENT incision) effectively and predictably reduced preoperative oblique astigmatism. In eyes with clinically relevant oblique astigmatism, we recommend using a modified BENT incision.

Aged↗
PubMed1998

Two year follow-up of astigmatism after phacoemulsification with adjusted and unadjusted sutured versus sutureless 5.2 mm superior scleral incisions.

PURPOSE: To evaluate changes in astigmatism 6 months to 2 years after 5.2 mm superior scleral incision phacoemulsification using 3 closures. SETTING: Department of Ophthalmology, Vejle Hospital, Vejle, Denmark. METHODS: This long-term follow-up study included 75 consecutive phacoemulsification patients who were randomly allocated to 1 of 3 incision closures: 1 intraoperatively adjusted cross suture, 1 unadjusted cross suture, no suture. Postoperative astigmatism after 1 and 2 years was evaluated by keratometric cylinder, induced astigmatism (Naeser's polar values), induced cylinder (Jaffe's vector analysis), and vector decomposition (Olsen). The data were compared with 1 week values. RESULTS: In the previous study, median astigmatism after 6 months was similar in all 3 groups, but only the sutureless group showed early stability. Significant against-the-rule (ATR) changes were seen in the sutured cases (P < .01). The 1 and 2 year follow-up showed continued stability in the sutureless cases. The adjusted-suture group exhibited stability after 6 months, while the unadjusted-suture group showed a further tendency to change ATR. At 2 years, median ranges of astigmatism were -0.49 to -0.90 diopter (D) (Naeser), 0.77 to 1.02 D (Jaffe), and 96% to 98% ATR (Olsen). The intergroup differences were not statistically significant. CONCLUSION: Two year follow-up confirmed that sutureless closure led to early astigmatism stability. Using a suture prolonged the postoperative period of astigmatism instability, and if used without intraoperative adjustment, a tendency toward a less predictable outcome persisted after 2 years.

Aged↗
PubMed1999

Effect of astigmatism on multifocal intraocular lenses.

PURPOSE: To study the effect of astigmatism on multifocal intraocular lens (MIOL) function. SETTING: Laser Laboratory, Department of Electronics, Electrotechnics and Informatics, University of Trieste, Italy. METHODS: Using an experimental optical system, this study compared the division of a laser beam in the focal spots of 1 monofocal IOL (Pharmacia 722A), 1 bifocal IOL (Pharmacia 811E), and 2 MIOLs (AMO Array MPC25NB and Domilens Progress 1). The model consists of a helium-neon laser and an optical system: a triangular optical bench with a precision collimator, a micropositionable immersion stage to support the IOL, and a digital image-processing system. Astigmatism was induced by interposing a +1.0 diopter (D) cylinder lens between the IOL and the television camera. Astigmatism was corrected by adding a -1.0 D cylinder lens in front of the IOL on the same axis. RESULTS: Astigmatism creates pairs of focal lines, 1 for each focal spot in the IOL. In the multifocal IOL, the posterior focal line of the nearest focus interfered with the anterior line of the next focus. Correcting the astigmatism led to a significant reduction (mean 20%) in light intensity. CONCLUSIONS: Astigmatically neutral surgery or surgical correction of pre-existing astigmatism is essential in MIOL implantation to minimize the decrease in contrast sensitivity.

Astigmatism↗
PubMed1999

Corneal astigmatism after cataract surgery with 4.1 mm BENT scleral and 4.1 mm plus meridian corneal incisions.

PURPOSE: To determine whether the 4.1 mm BENT (between 9 and 12 o'clock) scleral incision or the 4.1 mm plus meridian corneal incision (PMCI) is better at minimizing postoperative astigmatism. SETTING: Department of Ophthalmology, Kobe City General Hospital, Kobe, Japan. METHODS: This prospective study comprised 58 eyes of 29 consecutive patients with bilateral cataract. One eye was randomly assigned to have cataract surgery with a 4.1 mm BENT scleral incision and the other eye, with a 4.1 mm PMCI. Corneal astigmatism was measured before surgery and 1, 3, 10, 30, and 100 days after surgery. RESULTS: Mean astigmatism preoperatively and on postoperative days 1, 3, 10, 30, and 100 in the BENT scleral incision group was 0.99 +/- 0.66, 1.53 +/- 1.11, 1.12 +/- 0.72, 1.26 +/- 0.81, 1.16 +/- 0.73, and 1.09 +/- 0.64 diopters (D), respectively. Means in the PMCI group were 1.14 +/- 0.79, 1.38 +/- 0.98, 1.17 +/- 0.88, 1.31 +/- 0.77, 1.01 +/- 0.70, and 1.00 +/- 0.60 D. respectively. Astigmatism on days 1 and 10 postoperatively was significantly greater than preoperatively in the BENT group (P < .03) but not in the PMCI group. The changes in astigmatism were less in the PMCI group at every examination and were significantly different 30 days postoperatively (P < .05). The negative correlation between preoperative astigmatism and the final postoperative change was significant in both groups (P < .032); the value of x-intercept of the regression line was 1.37 D in the BENT scleral incision group and 0.82 D in the PMCI group. CONCLUSION: In cataract surgery using a 4.1 mm incision, the PMCI surpassed the BENT scleral incision in minimizing postoperative corneal astigmatism.

Adult↗
PubMed2001

Treatment of post-keratoplasty astigmatism by topography supported customized laser ablation.

PURPOSE: To evaluate the clinical and optical efficiency of topography modulated customized corneal ablations for irregular corneal astigmatism. MATERIAL & METHODS: Sixteen eyes of 16 patients with iatrogenic corneal astigmatism (post keratoplasty) were consecutively included. Based on preoperative corneal topographic measurements height deviations from a spherical corneal shape were calculated and transferred to a flying-spot excimer laser. Photo-refractive keratectomy of the topographic irregularities was then performed. Clinical and optical efficiency was evaluated by best corrected visual acuity and by computation of corneal wavefront aberrations before and up to one year after treatment. Wavefront aberrations were decomposed by Zernike polynomial analysis. RESULTS: Before treatment the average best-corrected visual acuity was 0.23. Three and 12 months after PRK the average best-corrected visual acuity had increased to 0.37 (p<0.05) and 0.45 (p<0.05), respectively. Corneal wavefront aberrations (root-mean-square) were 3.35 before surgery and 1.88 (p<0.05) and 1.51 (p<0.05) at three and 12 months after treatment. Zernike polynomial decomposition of the wavefront aberrations revealed that regular corneal astigmatism was the most important aberration component before and after surgery. Regular astigmatism was significantly decreased by the procedure, whereas coma, spherical aberrations, and higher-order aberrations were not reduced significantly. CONCLUSION: Topography modulated photorefractive keratectomy of highly astigmatic corneal grafts can improve best corrected visual acuity and reduce corneal wavefront aberrations. Even in apparently irregular topographic astigmatism, regular astigmatic wavefront aberration may be the most important contributor to wavefront errors.

Astigmatism↗
PubMed2006

Corneal astigmatism in Graves' ophthalmopathy.

PURPOSE: To describe corneal astigmatism in patients under the age of 55 years with Graves' ophthalmopathy and to compare it to a control group. METHODS: Retrospective, nonrandomized comparative observational case series. A total of 109 patients with inactive Graves' ophthalmopathy and 109 age- and gender-matched control individuals without Graves' ophthalmopathy were examined with manual corneal keratometry. In the Graves' patients, 52% had a CT scan available for review, and 41% underwent orbital, strabismus, and/or eyelid surgery with a follow-up of keratometry over a mean period of 1.7 years after surgery. RESULTS: For the dioptres, there was a statistically significant difference between the Graves' and the control eyes at 3-3.25 dioptres in both eyes (t-test, right eyes, P=0.042; left eyes, P=0.041). For the meridians, the astigmatism was found to be greater at the meridians 95-100 degrees (t-test, P=0.044) and 105 degrees -110 degrees (t-test, P=0.017) in the right eyes only. In 10 (9%) Graves' patients, the astigmatism had caused newly acquired reduced visual acuity. Greater astigmatism in dioptres did not correlate with specific CT scan findings (chi(2)-test, df=2, P=0.187). Following orbital, strabismus, and eyelid surgery, the dioptres and meridians of the astigmatism did not change in 56 (68%) and 66 (81%) eyes, respectively. CONCLUSIONS: Graves' ophthalmopathy may be associated with greater with-the-rule corneal astigmatism, which, overall, is not influenced by orbital, strabismus, or eyelid surgery. The astigmatism may possibly be caused by soft-tissue fibrosis in the superolateral orbital region.

Adult↗
PubMed1999

[Photoastigmatic refractive keratectomy for low, moderate, and high astigmatism using a broad beam excimer laser: evaluataion according to new international criteria].

BACKGROUND: Photorefractive keratectomy (PRK) is an accepted procedure to correct myopia in Germany. The purpose of this study was to evaluate photoastigmatic refractive keratectomy (PARK) for myopic astigmatism. MATERIAL AND METHODS: PARK using the VISX 20/20 excimer laser was performed in 50 eyes of 36 patients (25 female, 16 male) aged 22 to 68 years (mean 38 +/- 10 years) in the period of 1995 to 1996. Retrospective evaluation was done after dividing the patients into three astigmatic groups between -0.5 diopters (D) and -1.5 D (group I, n = 28), between -1.75 D and -3.0 D (group II, n = 16) und between -3.25 D and -5.5 D (group III, n = 6). The correction of myopic astigmatism was assessed concerning the criteria safety, efficacy, predictability and stability. Mean follow-up was 12 months (8-15 months). RESULTS: Seventy-eight % of all eyes achieved an uncorrected visual acuity of > 0.5. Sixty-eight % of the eyes were within +/- 1.0 D of the desired correction. Loss of 2 or more lines of best corrected visual acuity occurred in 6 eyes (12.0%). We observed in group I an astigmatic reduction of 36.0%, in group II of 66.5% and in group III of 68.0%. The surgically induced astigmatism was calculated with 1.29 +/- 1.0 D. Mean axis rotation of the refractive cylinder was 22.12 +/- 23.05 degrees. CONCLUSIONS: PARK using the VISX 20/20 excimer laser is an acceptable procedure to correct myopic astigmatism. However, the study revealed that astigmatic reduction with a broad beam laser is not yet perfect in terms of efficacy, predictability and safety.

Adult↗
PubMed1995

[Lens astigmatism in connection with implantation of a foldable one-piece silicone lens in a patient].

BACKGROUND: The use of one-piece plate-haptic Silicon lenses has become more frequent especially in combination with small incision cataract surgery. Different complications as before are to be expected. CASE REPORT: Six weeks after cataract surgery and implantation of a one-piece plate-haptic Silicon lens a lens astigmatism of 3.5 dpt was noted. The astigmatism occurred after successfully performed retinal detachment surgery in this eye. The development of the astigmatism was considered to be due to a capsular shrinkage of the anterior capsular ring. The retinal detachment surgery was performed with the use of SF6 gas, which is known as a factor for increasing inflammation. After a Nd: YAG incision of the anterior capsule the astigmatism disappeared immediately. CONCLUSION: Capsular shrinkage can induce a significant lens astigmatism in combination with soft one-piece plate-haptic Silicon lenses. Intraocular inflammation seems to play an important role. Astigmatism after implantation of one-piece plate-haptic Silicon lenses in combination with signs of capsular shrinkage can be explained by lens astigmatism only.

Aged↗
PubMed1994

[Astigmatism against the rule after small incision cataract surgery. A multifactorial, multivariate study].

BACKGROUND: Small-incision cataract surgery has been further developed by the introduction of the sutureless technique. This procedure has reduced operation time and the surgically induced astigmatism compared to closure technique. PATIENTS AND METHODS: We evaluated 426 patients operated by the same surgeon using the same intraoperative approach. Patients were monitored for postoperative induced astigmatism and postoperative complications. RESULTS: Our results demonstrated small induced astigmatism after one week and one month. The no-stitch technique showed the smallest postoperative astigmatism with the least variation. With multivariate methods we also analysed several factors influencing the axis of the induced astigmatism. CONCLUSION: The most important factor for a postoperative astigmatism against the rule is using the no-stitch-technique and the existence of a preoperative astigmatism against the rule.

Astigmatism↗
PubMed1989

Meridional analysis of with-the-rule astigmatism in Oklahoma Indians.

Refraction and keratometry records were obtained for 142 consecutive with-the-rule astigmats and for 100 consecutive nonastigmats from W. W. Hastings Indian Health Service Hospital in Tahlequah, Oklahoma. Patients were 5 to 40 years of age. Patients with higher degrees of Indian ancestry were more common in the astigmatic group than in the spherical refraction group. An analysis of refractive error and keratometry by principal meridian was performed. The horizontal meridian refractive error in astigmats was most often near emmetropia. Compound myopic astigmatism and mixed astigmatism accounted for over 3/4 of the cases. The astigmats as a group had flatter corneas in the horizontal and steeper corneas in the vertical than the nonastigmats. Horizontal refractive errors and horizontal keratometry readings showed a weak but significant correlation in astigmats but not in nonastigmats.

Adolescent↗
PubMed1991

Changes in ocular astigmatism over the whole range of accommodation.

The refraction of 20 subjects was measured over the whole range of accommodation using an objective automated refractometer in order to investigate the astigmatic change whose origin is presumed to be at the lens. For this purpose, the corneal vertex was used as the plane of reference to avoid changes in the optical effectively of a cylindrical lens at near. The change in the astigmatism with accommodation was observed in each subject. Subjects were then divided into three groups: (1) seven subjects showed an increase in astigmatism with accommodation; (2) eight subjects showed constant astigmatism up to the accommodative nearpoint; and (3) five subjects showed other types of change, such as reduced astigmatism in the intermediate accommodative state. These variations suggest that accommodative astigmatism is affected by many elements such as lens, zonule, and muscle. Two of 20 subjects could see the vertical line of the visual target composed of many directional lines clearer than the horizontal line at distance. Conversely, they could see the horizontal line clearer than the vertical line at near. We also studied the correspondence between the dark focus of accommodation and the dioptric distance where astigmatism is at a minimum, as suggested previously. The results showed that no such direct relation existed.

Accommodation, Ocular↗
PubMed2000

Management of irregular astigmatism.

Using a liberal definition of corneal irregularity, modern videokeratoscopy may define approximately 40% of normal corneas with a toric refractive error as possessing primary irregular astigmatism. The causes of secondary forms of irregular astigmatism include corneal surgery, trauma, dystrophies, and infections. Internal refractive surface and media irregularity or noncorneal astigmatism (ocular residual astigmatism) contribute to irregular astigmatism of the entire refractive path of which crystaline lenticular astigmatism is usually the principal contributing component. Treatment options have increased in recent years, particularly, though not exclusively, through the advent of tailored corneal excimer laser ablations. However, discussion continues concerning the systematic approach necessary to enable treatment to achieve an optimal optical surface for the eye. Discussion also continues as to what constitutes the optimal corneal shape. Some refractive procedures may increase higher order aberrations in the attempt to neutralize refractive astigmatism. The way to further refinement of the commonly performed refractive techniques will ultimately lie in the integrated inclusion of a trio of technologies: topographic analysis of the corneal surface, wavefront analysis of ocular refractive aberrations, and vector planning to enable the appropriate balance in emphasis between these two diagnostic modalities. For the uncommon, irregularly roughened corneas, the ablatable polymer techniques show some promise.

Animals↗
PubMed2004

Late-stage progressive corneal astigmatism after penetrating keratoplasty for keratoconus.

PURPOSE: Progressive corneal astigmatism occurring at least 10 years after penetrating keratoplasty for keratoconus is a late-phase complication of surgery. This report characterizes this condition in a series of patients from three corneal referral centers in the United States. METHODS: Charts were retrospectively reviewed which met the following criteria: penetrating keratoplasty performed for keratoconus at least 10 years ago, keratometry or simulated keratometry from topography as well as manifest refraction recorded at least 6 months after the last suture removal ("baseline"), and an increase in corneal astigmatism of at least three D over baseline recorded at least 5 years later. Patients who had any other corneal or intraocular surgery performed were excluded. RESULTS: Data from 15 patients (11 males and 4 females) who had penetrating keratoplasties performed by 8 different surgeons are included in this descriptive series. Postoperative follow-up averaged 17.27 years (range 11-24 years). The average donor button size was 7.83 mm (range 7.25-8.5 mm). Baseline corneal astigmatism was obtained an average of 5.2 years after penetrating keratoplasty (range 1.5-16 years) and was on average 3.57 +/- 1.8 D (10 with-the-rule [WTR], 3 against-the-rule [ATR], 2 oblique). Corneal astigmatism significantly increased to an average of 11.23 +/- 3.56 D (range 8.00-19.37 D, P < 0.0001) and most astigmatism was regular and WTR (9 WTR, 3 ATR, 3 oblique) 15.3 years (range 10-22 years) after surgery. Inferior steepening on topography was often noted, even those with oblique and ATR axes. CONCLUSIONS: High, late-stage, regular astigmatism after penetrating keratoplasty for keratoconus is described in a series of patients occurring at least 10 years after surgery. Possible mechanisms of this progressive astigmatism are recurrence of keratoconus in the graft, progressive corneal thinning of the host cornea, or progressive misalignment of the graft-host interface over time.

Astigmatism↗