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PubMed2004

[The combination of positive cylinders with negative cylinders in the detection of mixed astigmatism].

OBJECTIVE: To study clinical retinoscopy combined positive cylinders with negative cylinders in the detection of mixed astigmatisms. METHOD: 189 cases (340 eyes) with mixed astigmatism were divided into three groups (< 3.00 D; 3.00 approximately 6.00 D; > 6.00 D). There are 156 eyes with mixed astigmatism less than 3.00 D (76 eyes in experiment group, 80 eyes in control group); 132 eyes with mixed astigmatism between 3.00 D to 6.00 D (68 eyes in experiment group, 64 eyes in control group) and 53 eyes with mixed astigmatism over 6.00 D (29 eyes in experiment group, 24 eyes in control group). They were examined with cycloplegic retinoscopy. Retinoscopy of combined positive cylinders with negative cylinders was applied in experiment group, while conventional retinoscopy was used in control group. According to the shape of neutralized image, the accuracy and facility of the axis judgement, operating time and the number of combined lens, the result of retinoscopy was classified into three grades. Grade I: The shape of neutralized image is well distributed. The axis is easy to be evaluated precisely. Operating time is less than five minutes and only need one or two piece of lens. Grade II: The shape of neutralized image is not so well distributed. The axis is not difficult to be evaluated. Operating time is from five to ten minutes and needs two or three piece of lens to combine with. Grade III: The shape of neutralized image is not so well distributed and would be interfered by the combined lens or other factors easily. The axis is difficult to be evaluated precisely. Operating time is more than ten minutes and needs more than three piece of lens to combine with. RESULT: In the group of mixed astigmatism less than 3.00 D, no significant difference was found between experiment group and control group. (chi(2) = 0.094, P = 0.759). However, significant difference (chi(2) = 5.546, P = 0.019) was found between the groups with mixed astigmatisms from 3.00 D to 6.00 D and very significant difference (chi(2) = 8.509, P = 0.004) was found between the groups with mixed astigmatisms over 6.00 D. CONCLUSION: Retinoscopy of combined positive cylinders with negative cylinders is an effective, convenient and precise method for detection higher degree mixed astigmatisms. It's an additional assistance for the conventional retinoscopy.

Adolescent↗
PubMedDate not supplied

Simultaneous and sequential selective suture removal to reduce astigmatism after penetrating keratoplasty.

We studied two separate groups of consecutive eyes with penetrating keratoplasty in avascular corneas in which we performed selective interrupted suture removal to decrease postoperative astigmatism, describing the time course of change in astigmatism. In the first group (29 eyes), multiple interrupted sutures were selectively removed at a single visit in an attempt to reduce the astigmatism to less than or equal to 3 diopters; the patients were followed for 30 months. In the second group (24 eyes), one interrupted suture was removed at each visit every 2 weeks until the astigmatism was less than or equal to 3 D; the patients were followed for 15 months. Surgical techniques were different in the two groups. Both techniques reduced postoperative astigmatism. Larger changes in astigmatism occurred between the first suture removal visit and the subsequent visit in the first group. At 1 year, the multiple-suture-removal-at-a-single-visit group averaged 3.1 D of astigmatism, with 50% of eyes less than or equal to 3 D, whereas the single-suture-removal-at-multiple-visits group had a mean astigmatism of 1.9 D with 88% of eyes less than or equal to 3 D. The two groups we studied were not directly comparable, because surgical techniques differed, because they were operated at different times, and because the cases were not randomized. Nevertheless, we think that selective suture removal to reduce astigmatism after penetrating keratoplasty is best done by removing only one (or sometimes two) sutures per examination.

Astigmatism↗
PubMed1986

A computerized analysis of astigmatism after cataract surgery.

We have performed a computerized analysis of postoperative changes in corneal astigmatism in 203 consecutive cases of extracapsular cataract extraction with posterior chamber intraocular lens implantation performed by one surgeon. Surgical technique was standardized consisting of a 140 degree posterior limbal incision with preplaced 9-0 silk and postplaced 10-0 nylon sutures. The average postoperative astigmatism was 1.60 D and the average surgically induced change in astigmatism 0.51 D after a mean follow-up of 5.4 months. When the axis of astigmatism was considered, cataract surgery on the average initially induced 2.2 D of with-the-rule astigmatism which gradually declined, stabilizing at 0.35 D against-the-rule 19 weeks postoperatively. An analysis of the natural history of astigmatism after cataract surgery helps to optimize the timing of spectacle prescription and postoperative intervention to correct excessive astigmatism. A computerized astigmatism analysis also provides rapid feedback to guide changes in surgical technique to minimize astigmatism.

Astigmatism↗
PubMed1995

[Modification of the no-stitch technique in extracapsular cataract extraction by a single radial suture. Effect on postoperative astigmatism].

Self-sealing intrascleral wound construction with a trapezoidal 12-mm incision for extracapsular cataract extraction and implantation of a standard PMMA IOL with a 6.5-mm optical diameter using the no-stitch technique has been well established at our clinic since 1991. This technique allows cataract surgery in a nearly closed system. In consideration of our earlier results, the no-stitch technique was modified by a single perpendicular suture in the middle of the 12-mm incision to reduce postoperative induced astigmatism further. We examined 200 consecutive patients 6 months after surgery (no-stitch vs one-stitch wound closure). The preoperative average astigmatism was 0.86 +/- 0.68 D (1.01 +/- 0.95 D). Preoperatively 37% (47%) of the eyes had With the Rule Astigmatism and 47% (39%) Against the Rule Astigmatism. Six months after surgery 10% (8%) of the cases showed With the Rule Astigmatism and 72% (65%) Against the Rule Astigmatism. Induced astigmatism was stabilized to 1.43 +/- 0.87 D (2.11 +/- 1.43 D). Compared with sutureless wound closure, the one-stitch technique had no long-term effect on the axes of astigmatism but significantly diminished induced astigmatism about 0.5 D.

Astigmatism↗
PubMed1996

[A clinical report on mixed astigmatism].

OBJECTIVE: This study was designed to analyze the common cause of asthenopia, mixed astigmatism. METHODS: The types and characters of mixed astigmatism in 356 eyes (207 patients) were analyzed and their naked and corrected visual acuities were investigated. Some problems of mixed astigmatism were discussed. RESULTS: Most of the patients had evident visual defects, the average naked visual acuity being 0.3 (20/60). However, all the patients had better corrected visual acuities with an average of 0.6 (20/30). CONCLUSIONS: Due to the presence of accommodation during the examination, an incorrect lens may be prescribed. Three mistakes might occur, (1) A mixed astigmatism is not detected, and a simple myopic lens is prescribed; (2) An eye with mixed astigmatism is diagnosed as simple or compound myopic astigmatism; (3) A hyperopic astigmatism is diagnosed as mixed astigmatism. The visual defects caused by mixed astigmatism can be satisfactorily corrected by spectacles.

Adolescent↗
PubMed1997

A comparison of two selective interrupted suture removal techniques for control of post keratoplasty astigmatism.

PURPOSE: Two selective interrupted suture removal techniques were compared to determine which technique resulted in earliest, best visual acuity and least postoperative astigmatism. METHODS: Sixty-five consecutive optical penetrating keratoplasties were performed using 12 interrupted 10-0 nylon sutures and a 12-bite continuous 10-0 nylon suture, and were alternately assigned to 1 of 2 selective suture removal groups. All patients had refraction, keratometry, and videokeratoscopy postoperatively, starting at 6 weeks. Six weeks postoperatively, Group I underwent simultaneous removal of six alternate sutures, with the first of the 6 sutures removed at the steepest meridian, while Group II had selective sutures removed only at the steepest meridian, if associated with greater than 2 diopters of astigmatism in that meridian. Subsequently, interrupted sutures were then selectively removed until the resultant astigmatism approached 3.0 diopters or less. Measurements of resultant astigmatism are reported prior to selective suture removal, following selective suture removal, at 6 months postoperatively, at the completion of all selective suture removal, and at the final visit. RESULTS: At 6 months, residual astigmatism after the 2 techniques of selective suture removal, as measured by refraction, keratometry, and computer-assisted videokeratoscopy, was 2.8, 3.0 and 3.4 diopters for Group I, and 2.2, 2.6 and 3.7 diopters for Group II. At 1 year, the average final visit, astigmatism was 2.5, 2.4 and 2.7 diopters for Group I, and 2.1, 2.0 and 2.3 diopters for Group II. By the final visit, a best corrected vision of 20/50 or better was achieved in 86% of eyes in Group I and in 65% of eyes in Group II, and there was a significant difference in average keratometry of 47.4 diopters in Group I compared to 46.0 diopters in Group II and, as measured by videokeratoscopy, 47.9 diopters in Group I compared to 45.8 diopters in Group II. CONCLUSIONS: Selective suture removal by either technique reduces keratoplasty astigmatism with residual interrupted and continuous sutures in place. The combined use of refraction, keratometry, and videokeratoscopy probably provides more reliable and reproducible quantitative measurements of astigmatism. Minimizing astigmatism by selective suture removal is a major factor in the attempt to achieve excellent and visual function in the majority of patients who have undergone penetrating keratoplasty.

Adult↗
PubMed1998

Quantitative evaluation of irregular astigmatism by fourier series harmonic analysis of videokeratography data.

PURPOSE: To assess quantitatively corneal irregular astigmatism in association with best spectacle-corrected visual acuity. METHODS: Refractive powers on a mire ring measured with computerized videokeratography were decomposed, using the Fourier series harmonic analysis. Extracting spherical and regular astigmatic components, the remaining irregular astigmatic component was quantified on rings 2 through 9. A weighted average was calculated by using the Stiles-Crawford effect on the basis of the radius of each ring of each eye and was used as an index of the irregular astigmatic component. Data analyses were carried out in 108 eyes, including 53 normal eyes, 34 eyes with keratoconus, and 21 eyes that had undergone penetrating keratoplasty for keratoconus. Keratoconic eyes and eyes after keratoplasty were included in the study only if visual acuity, corrected with a hard contact lens, was 20/20 or better. Logarithm of best spectacle-corrected visual acuity, age, type of disease, refractive astigmatism, irregular astigmatic component, surface regularity index, and surface asymmetry index were analyzed. RESULTS: In results of multiple regression analysis, the irregular astigmatic component was significantly correlated with best spectacle-corrected visual acuity (r = -0.744; adjusted R2 = 0.549; P < 0.001), whereas other explanatory variables showed no correlation with best spectacle-corrected visual acuity. CONCLUSIONS: This model of the irregular astigmatic component seems to be an efficient, quantitative means of describing corneal irregular astigmatism.

Adolescent↗
PubMed1998

The effect of mitomycin-C on postoperative corneal astigmatism in trabeculectomy and a triple procedure.

BACKGROUND AND OBJECTIVE: The authors attempted to determine the effect of mitomycin-C (MMC) on postoperative corneal astigmatism in patients who underwent trabeculectomy or a triple procedure (trabeculectomy, extracapsular cataract extraction, and intraocular lens implantation). PATIENTS AND METHODS: Using the vector analysis method, the authors measured the postoperative induced astigmatism of 76 eyes in 59 patients who underwent trabeculectomy or a triple procedure with or without the application of MMC. Postoperative induced astigmatism corresponding to the 180 degrees axis was compared between the two groups. RESULTS: The patients who underwent trabeculectomy with or without MMC showed a mean induced astigmatism of -1.01 D and -2.63 D, respectively, after 1 month (P < .05), and 0.34 D and -1.42 D after 12 months (P < .05). Those who underwent a triple procedure with or without MMC showed a mean induced astigmatism of -1.81 D and -4.50 D, respectively, after 7 days (P < .05), and 1.73 D and -0.13 D, respectively, after 12 months (P < .05). The entire amount of postoperative against-the-rule astigmatic shift was similar between the with-MMC group and the without-MMC group. The against-the-rule astigmatic shift of the group without MMC reached a plateau after 3 months. However, the group with MMC showed continuous against-the-rule astigmatic shift until 12 months. CONCLUSION: This study suggests that MMC induces less with-the-rule astigmatism in early postoperative periods and continuous against-the-rule shift after 3 months following a trabeculectomy or a triple procedure.

Administration, Topical↗
PubMed1997

A corneal topographic analysis of astigmatism after excimer laser photorefractive keratectomy.

OBJECTIVE: To identify the astigmatism changes after excimer laser photorefractive keratectomy (PRK) and the visual influence of astigmatism. METHODS: 109 myopic eyes followed up for more than 1 year were analyzed by videokeratography, and their visual acuities were examined. Before the operation, the astigmatic errors with cycloplegic refractive examination were -1.00 approximately -2.00 D. RESULTS: The position of astigmatism axis was basically consistent with that in corneal topography, but in astigmatism diopter there were some differences between the cycloplegic examination and topographic analysis. A stigmatism was found in 62% of the eyes, asymmetrical in 33% and against-the-rule in 5% by using topographic analysis. There was little change observed in the position of astigmatism axis after PRK observed. Some changes of postoperative astigmatism diopter were seen in different periods. It increased in the postoperative 10 days or 1 month, and afterwards gradually decreased and became stable in 6 months to 1 year. The postoperative residual astigmatism was low in degree, and did not affect the visual acuity. The actually corrected diopter was within the anticipated corrected diopter range of +/- 1.00 D. accounting for 97.4%. CONCLUSION: By using spherical equivalent method of calculation in PRK, the refractive correction of the operation cases with myopia and low degree of astigmatism (< -2.00 D) was satisfactory.

Astigmatism↗
PubMed1987

Control of corneal astigmatism following cataract extraction by selective suture cutting.

We evaluated the ability of selective suture cutting to reduce postoperative corneal astigmatism in 75 eyes of 68 patients who underwent extracapsular cataract extraction with posterior chamber intraocular lens implantation. Keratometric and refractive measurements were obtained before and at selected intervals (3, 6, 10, 26, and 52 weeks) after surgery. The number of sutures cut during the sixth week after surgery was based on the degree of astigmatism (0.00 to 2.00 diopters (D), no sutures cut; 2.25 to 3.00 D, one suture cut; 3.25 to 4.00 D, two sutures cut; greater than or equal to 4.25 D, three sutures cut). Our analysis demonstrated the following: (1) a spontaneous reduction of 0.5 D in surgically induced astigmatism in eyes without suture cutting, (2) an additional reduction of 1.2 D in postoperative astigmatism for each suture cut, and (3) attainment of 75% to 93% of the total effect of suture cutting within four weeks. The final astigmatism one year after surgery had increased by a mean of 0.9 D, exhibited predominantly with-the-rule properties, and showed no significant difference among the four groups of patients. Vector analysis revealed that only small shifts in the axis of astigmatism occurred after suture cutting. A strong correlation between the keratometric and subjective refractive measurements during all postoperative examinations indicated that corneal astigmatism is primarily responsible for postoperative astigmatism.

Astigmatism↗
PubMed1993

Causes of high astigmatism after penetrating keratoplasty.

We retrospectively evaluated the factors which might have caused excessive corneal astigmatism after penetrating keratoplasty (PKP) in 29 eyes, in which surgical correction of astigmatism was indicated. In 18 eyes high astigmatism (5 diopters or more) existed before suture removal probably due to graft elevation (3x), wound dehiscence (3x), wound configuration abnormalities such as ovality/overcut (8x), and a thin recipient cornea (2x). The cause was unknown in 2 eyes. In 19 eyes the astigmatism considerably increased after all sutures were removed; astigmatism increased an average of 8.8 diopters (range, 5 to 16.5 D). Ten of these 19 patients showed graft elevation, despite the fact that the sutures were only removed after an average 22.9 months. In 3 other patients the astigmatism gradually increased over the years, long after suture removal; two of these showed graft elevation. The study demonstrates the possible instability of keratoplasty wounds, the change in astigmatism after suture removal, and the late apparently spontaneous changes in astigmatism after PKP in some eyes.

Adult↗
PubMed1997

[Corneal topography after cataract surgery with tunnel incision on a steeper meridian in inverse and oblique astigmatism].

Scleral tunnel incision at the 12 o'clock-position for no-stitch cataract surgery can increase preexisting against-the-rule astigmatism by flattening the vertical corneal meridian. An oblique axis can change by operative induction. We investigated, in a prospective study, whether reduction of such a preoperative astigmatism could be induced by locating the tunnel incision on the steeper meridian. Eighteen eyes with senile cataract and against-the-rule or oblique astigmatism of at least 0.7 diopters were operated with a standardized 5 x 6 mm scleral tunnel incision and a 6 mm PMMA posterior chamber lens. We evaluated the astigmatism with a videokeratoscopy TMS-I preoperatively and about 6 months after the surgery. The mean corneal astigmatism was 1.8 diopters pre- and 1.5 diopters postoperatively. A reduction of keratometric astigmatism was reached in 72% of cases; 17% remained unchanged. The surgically induced astigmatism calculated by Jaffer's and Clayman's vector analysis was 0.68 diopters. The technique of scleral tunnel incision with lateral or oblique approach can reduce a preexisting against-the-rule or oblique astigmatism.

Astigmatism↗
PubMed1999

[Long-term stability of astigmatism outcome after arcuate lamellar keratotomy. 3-year results of a prospective study].

INTRODUCTION: The correction of low to moderate astigmatism is possible today by means of photoablation (PRK), while the treatment of moderate and higher astigmatism still involves refractive keratotomy. Experience has shown that cataract surgery, using modern tunnel techniques with self-healing incisions, results in earlier stability in both the refractive outcome and wound healing. In this study, we attempted to combine the advantages of lamellar keratotomy with those of a pair-wise T-incision as arcuate lamellar keratotomy (ALK). PATIENTS AND METHODS: The clinical outcome of 41 patients who underwent ALK was investigate in a prospective study over a period of 3 years. The pre- and postoperative investigations undertaken included the measurement of astigmatism using a Zeiss keratometer, uncorrected visual acuity, and corrected glare vision using a Humphrey autorefractor. All patients had astigmatism between 2.0 and 7.0 D. Together with a uniform arcuate incision, we used 7 mm (n = 26) and 8 mm (n = 15) mm zones for correction. RESULTS: The average preoperative astigmatism was 4.01 +/- 1.90 (median, 3.50) D. After a 3-year follow-up the average postoperative astigmatism was 1.59 +/- 1.29 (median, 1.38) D. The astigmatic change induced (Jaffé) after 3 years was about 3.23 +/- 2.23 (median, 3.16) D. The average uncorrected visual acuity (log MAR) before ALK was 0.20 +/- 0.12 (median, 0.22) and after follow-up, 0.41 +/- 0.14 (median, 0.39). Corrected glare vision before surgery was 0.23 +/- 0.19 (median, 0.10) and afterwards, 0.25 +/- 0.22 (median, 0.14). CONCLUSIONS: Arcuate lamellar keratomy (ALK) stood the test as a routine clinical procedure for correction of moderate astigmatism with stable postoperative functional outcomes. We did not find impairment of glare vision following this procedure.

Aged↗
PubMed2002

[Astigmatism after trans-scleral posterior chamber lens implantation in young children].

BACKGROUND: The purpose of this study was to evaluate the postoperative astigmatism after trans-scleral fixation of intraocular lenses in children and to develop a strategy for amblyopia prophylaxis. PATIENTS AND METHODS: In eight eyes with lentectomy, posterior chamber intraocular lenses were fixed in the ciliary sulcus by trans-scleral sutures. The postoperative astigmatism was measured by retinoscopy every 1 to 2 weeks in the first 2 months, followed by monthly intervals thereafter. Keratometry was performed with an automated hand keratometer. RESULTS: Postoperative astigmatism was 2.5 to 8.0 D. The astigmatism regressed to 0.75 D in half the eyes within 4 weeks and in five of the eyes within 16 weeks. In one of the eight eyes, the astigmatism decreased to 2.0 D and in two it remained unchanged. The astigmatism did not change any more after 16 weeks postoperatively. Visual acuity was 0.016 to 1.0. CONCLUSIONS: Our study shows that the postoperative astigmatism regresses soon and does not seriously interfere with amblyopia therapy. If greater than 2 D, half of the astigmatism should be corrected with glasses, even in the early postoperative period. After 16 weeks, full correction is recommended.

Amblyopia↗
PubMed2004

Lamellar keratotomy to correct astigmatism in cataract surgery.

BACKGROUND: For the correction of astigmatism in cataract surgery, several incisional procedures have been developed. In this study, a modification of lamellar keratotomy was evaluated to correct astigmatism in cataract surgery. METHODS: Prospectively 32 eyes of 25 patients with a preoperative astigmatism greater than 1.5 D were studied. All patients were treated with lamellar keratotomy with an incision width of 6 mm and a radial length of 1.5 mm placed at the limbus in the steep meridian. Phacoemulsification and IOL implantation were then performed through a 3.2-mm corneal tunnel incision. After 4 weeks, mean astigmatism, mean corneal power changes, and mean surgically-induced astigmatism derived from vector analysis in the central 3-mm optical zone were determined. RESULTS: The mean astigmatism decreased from 2.75 +/- 0.80 D preoperatively to 1.58 +/- 0.91 D after 4 weeks (P < 0.001). There were no significant changes (P=0.614) of the mean corneal power. The mean surgically-induced astigmatism was 2.59 +/- 1.50 D. The induced changes were more accentuated in superior incisions. In corneal topography, 78% of the treated eyes revealed a characteristic threefold pattern of the mid-peripheral cornea postoperatively, which impaired the corneal optical performance in ray-tracing analysis. CONCLUSIONS: Lamellar keratotomy effectively reduced high preoperative astigmatism in cataract surgery. This surgical approach was combined with a superior, temporal, or oblique corneal incision.

Adult↗
PubMed2000

Influence of astigmatism on multifocal and monofocal intraocular lenses.

PURPOSE: To examine the influence of astigmatism on the visual acuity of patients with multifocal and monofocal intraocular lenses. METHODS: Thirty eyes of 30 patients who underwent five-zone refractive multifocal intraocular lens implantation and 30 eyes of 30 age-matched patients who had monofocal intraocular lens implantation were included. The visual acuities of these patients at 5.0, 3.0, 2.0, 1.0, 0.7, 0.5, and 0.3 m were measured by means of an all-distance vision tester after addition of a cylindrical lens of 0, 0.5, 1.0, 1.5, 2.0, and 2.5 diopters. RESULTS: Mean visual acuity at all distances decreased in proportion to the diopters of astigmatism in both the multifocal and monofocal intraocular lens groups. When astigmatism was 0.5, 1.0, or 1.5 diopters, distance visual acuity in the multifocal group was significantly worse than that in the monofocal group; with astigmatism of 2.0 diopters or more, intermediate visual acuity was also worse in the multifocal group. In contrast, near visual acuity in the multifocal group was significantly better than that in the monofocal group at all astigmatic diopters. When astigmatism was within 1.0 diopter, visual acuity in the multifocal group reached 20/29 at distance and 20/50 at near. Mean contrast sensitivity was also worse in the multifocal group than in the monofocal group. CONCLUSIONS: Both distance and intermediate visual acuity deterioration caused by astigmatism was greater with a multifocal intraocular lens than with a monofocal intraocular lens, whereas near visual acuity was better with the multifocal intraocular lens. When astigmatism was within 1.0 diopter, eyes with a multifocal intraocular lens achieved good visual acuity at both distance and near.

Accommodation, Ocular↗
PubMed2003

Astigmatism in infant monkeys reared with cylindrical lenses.

To determine whether developing primate eyes are capable of growing in a manner that eliminates astigmatism, we reared infant monkeys with cylindrical spectacle lenses in front of one or both eyes that optically simulated with-the-rule, against-the-rule, or oblique astigmatism (+1.50-3.00x90, x180, x45 or x135). Refractive development was assessed by retinoscopy, keratometry and A-scan ultrasonography. In contrast to control monkeys, the cylinder-lens-reared monkeys developed significant amounts of astigmatism. The astigmatism was corneal in nature, bilaterally mirror symmetric and oblique in axis, and reversible. The ocular astigmatism appeared to be due to a reduction in the rate of corneal flattening along the steeper meridian while the other principal meridian appeared to flatten at a more normal rate. However, regardless of the orientation of the optically imposed astigmatism, the axis of the ocular astigmatism was not appropriate to compensate for the astigmatic error imposed by the treatment lenses. Our results indicate that visual experience can alter corneal shape, but there was no evidence that primates have an active, visually regulated "sphericalization" mechanism.

Adaptation, Physiological↗
PubMed1985

Postoperative corneal astigmatism in cataract extraction: diamond knife versus Beaver blade.

Postoperative corneal astigmatism was studied in two groups of patients who had cataract extraction. The technique in both groups was identical except for the knife used for the partial-thickness limbal incision. In 49 patients the incision was performed with a Beaver blade and in 35 patients, with a diamond knife. Six weeks postoperatively the astigmatism was 1.27 +/- 0.90 diopters (D) in the diamond knife group, and 2.85 +/- 1.78 D in the Beaver blade group (P less than 0.0001). Sixty-one percent of the Beaver blade cases had with-the-rule astigmatism and 8% had no astigmatism. Thirty-one percent of the diamond knife cases had with-the-rule astigmatism and 26% had no astigmatism. At six months, the astigmatism was equal in both groups and practically identical to that found six weeks postoperatively in the diamond knife group. We conclude that incision of the limbal tissue with a diamond knife is associated with lower postoperative astigmatism and a more stable refractive state than incision with a Beaver blade.

Astigmatism↗