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PubMed2001

[Current state of knowledge on the subject of astigmatism etiopathogenesis].

PURPOSE: To present current state of knowledge on the subject of astigmatism etiopathogenesis. MATERIAL AND METHODS: A review of contemporary literature concerning pathomechanism of astigmatism. RESULTS: The optical, morphological and functional changes taking place in the visual pathway during the astigmatism are described. Special attention was focused on the functional modifications in the neuronal system of Brodmann's 17th area. The frequency of occurrence as well as the forms of astigmatism among children and adults are characterized. The results of papers indicating environmental and genetic reasons of astigmatism as well as the possible pathomechanism of astigmatism creation are presented. The necessity of astigmatism treatment before the end of visual cortex plasticity has been pointed out. The attitude towards some surgical methods of astigmatism treatment is expressed.

Adult↗
PubMed2002

Refractive astigmatism and size of pterygium.

The study evaluates the relationship between varying sizes of pterygium and refractive astigmatism. All patients with pterygium seen at the eye clinic of the University College Hospital within a six months period were included. The length, width and area of pterygium were measured. Refractive astigmatism in the subjects were measured. The findings showed that the length of pterygium on the cornea has a statistically significant relationship with the amount of refractive astigmatism. The amount of astigmatism increases with increase in the length of pterygia. A linear regression analysis showed that 38% of the total variability in astigmatism could be explained by the length of pterygium. The width and area of pterygium on cornea had no significant association with amount of refractive astigmatism. Size of pterygia could be an important predictor of the amount of astigmatism in an eye. However, a larger study need to be done to find other possible factors associating refractive astigmatism in eyes with pterygium.

Adult↗
PubMed2003

The effect of pterygium on corneal astigmatism.

OBJECTIVE: To determine the effect of pterygium on corneal astigmatism. METHOD: Two hundred and forty three eyes of 173 patients with primary pterygium were included in the present study. The extension of pterygium was measured by slit lamp and corneal astigmatism was measured by corneal topography. Correlation of the data was discussed. RESULTS: The size of pterygium extended from 0.50 mm to 8.10 mm (2.11 +/- 1.10). The diopter of corneal astigmatism ranged from 0.10 diopter to 14.60 diopter (1.86 +/- 2.39). The axis of corneal astigmatism was found in vertical axis 156 eyes (64.2%), oblique axis 36 eyes (14.8%) and horizontal axis 51 eyes (21.0%). The degree of corneal astigmatism significantly correlated with the extension of pterygium on the cornea (R Square = 0.45, p < 0.001). When the extension of pterygium exceeded 2.25 mm, there was a chance of developing corneal astigmatism of 2 diopter or more (86.21% of sensitivity and 80% of specificity). CONCLUSION: The extension of pterygium is significantly correlated with the degree of corneal astigmatism in the positive direction, with the highest percentage of with-the-rule astigmatism. Pterygium exceeding 2.25 mm of length should be considered within the limits of surgery.

Adult↗
PubMed2003

[Evaluation of early postoperative astigmatism with respect to anterior chamber opening].

UNLABELLED: The study evaluates amount and direction of postoperative astigmatism after usually performed techniques of cataract surgery. MATERIAL AND METHODS: 90 consecutive patients (120 eyes) mean aged 74.5 years, who underwent cataract surgery with clear corneal superior (Group 1) or temporal incision (Group 2), sclero-corneal tunnel sutureless incision (Group 3) or limbal ECCE incision with x sutures (Group 4), were examined with respect to postoperative astigmatism. Anterior chamber opening was determined by primary astigmatism and nucleus hardness. All measurements were performed based on keratometry. RESULTS: The highest mean value of with the rule astigmatism was assessed in Group 4. From the other hand, the least value were determined in group 2--95% with the rule and 5% oblique and in group 1--40% with the rule, 40% against the rule 20% oblique. In group 3, the value of postoperative astigmatism was higher, as compared with Group 1 and 2. It was assessed with similar proportion as in Group 1. CONCLUSIONS: At present cataract surgery techniques are not free of induced astigmatism. Study demonstrates significance of preoperative primary astigmatism assessment, with respect to surgery technique, to avoid postoperative astigmatism.

Aged↗
PubMedDate not supplied

Selective suture cutting for control of astigmatism following cataract surgery.

Use of 10-0 monofilament nylon in ECCE cataract surgery leads to high with the rule astigmatism. Many intraoperative and post operative methods have been used to minimise post operative astigmatism. We did selective suture cutting in 38 consecutive patients. Mean keratometric astigmatism at three and six weeks post operative was 5.76 and 5.42 dioptres (D) respectively. 77.5% of eyes had astigmatism above 2 D. Selective suture cutting along the axis of the plus high cylinder was done after six weeks of surgery. Mean post suture cutting keratometric astigmatism was 3.3 D and 70% of the eyes had astigmatism below 2 D. After 3 months of surgery mean keratometric astigmatism was reduced to 1.84 D. Axis of the astigmatism also changed following suture cutting. 40% of the eyes showed improvement in their Snellen acuity following reduction in the cylindrical power.

Adult↗
PubMedDate not supplied

Combined transverse and interrupted radial keratotomy for compound myopic astigmatism.

BACKGROUND: A variety of patterns of keratotomy are used to correct naturally occurring astigmatism. We evaluated straight transverse incisions with interrupted radial incisions (jump radials). METHODS: In 32 human eyes with naturally occurring astigmatism, we used straight transverse incisions with interrupted radial incisions, with or without additional radial keratotomy, to correct compound myopic astigmatism. The range of preoperative refractive astigmatism was 1.00 to 3.50 D. RESULTS: The mean follow-up time was 15 months (range, 12 to 18 months). The average surgically corrected astigmatism was 1.55 +/- 0.29 D. Eighty-seven percent of the eyes achieved less than 1.00 D of astigmatism, and the remaining four eyes retained 1.00 to 1.25 D of astigmatism. CONCLUSION: Combined transverse and interrupted radial incisions are effective in correcting naturally occurring astigmatism.

Adult↗
PubMed2004

LASIK and arcuate incisions for the treatment of post-penetrating keratoplasty anisometropia and/or astigmatism.

PURPOSE: To study the efficacy of Laser In Situ Keratomileusis (LASIK) and Arcuate Keratotomy (AK) for the treatment of anisometropia and/or astigmatism after Penetrating Keratoplasty (PKP) in an attempt to optimize binocular vision. MATERIAL AND METHODS: Correction of post-PKP anisometropia and/or astigmatism was considered only when stable refraction was achieved for at least 6 months. Four eyes were treated for anisometropia and astigmatism using the LASIK technique (IN-PRO Gauss Excimer Laser and SKBM Microkeratome). Five eyes were treated with AK to correct post-PKP astigmatism only. The results were evaluated using the following parameters: uncorrected visual acuity (UCVA), best subjective spectacle correction (BSC-VA), corneal uniformity (CU) index and predictive corneal (PC) acuity from the Holladay Diagnostic Summary (HDS) analysis. RESULTS: Post-PKP anisometropia and astigmatism were treated successfully after primary LASIK in three out of the four cases. One eye needed an additional diode thermal keratoplasty (DTK). Astigmatism post-PKP was treated successfully after primary AK in four of the five cases. One eye needed an additional LASIK. CONCLUSION: AK can be used successfully in cases of low-grade post-PKP astigmatism. LASIK gives better results in cases of post-PKP anisometropia and astigmatism. In order to affine the final results a combination with other refractive techniques such as DTK can be proposed. CU index and PC acuity (EyeSys-HDS analysis) are poor predictive parameters for visual outcome in cases of irregular corneal surfaces as it is often the case after PKP.

Adult↗
PubMed2004

[Reduction of astigmatism after perforating keratoplasty by adjustment of single running sutures and its influence on visual acuity].

The authors assess the outcomes of postkeratoplasty single running suture adjustment in 14 eyes (16 adjustments) of 14 patients (4 women, 10 men). The average age of patients was 39.68 year (ranging from 19 to 70 years). The suture adjustment was done in time span 2 to 39 weeks following after perforating keratoplasty (PKP), average 7.5 weeks. Follow up time was from 1 to 12 months, average 10.8 months. The value of keratometric and topographic astigmatism before suture adjustment were compared to the value of keratometric and topographic astigmatism 1, 6 and 12 months after suture adjustment. The changes of corneal refractive power and changes of uncorrected and best-corrected visual acuity were noticed as well. The mean value of keratometric astigmatism 7.47 +/- 2.69 D and mean topographic astigmatism 7.75 +/- 3.25 D before suture adjustment was decreased to 4.92 +/- 2.41 D and 4.83 +/- 1.46 D respectively one month after suture adjustment. These reductions of keratometric and topographic astigmatism (2.55 D and 2.92 D respectively) were statistically significant (p = 0.0416, and p = 0.0211 respectively). The mean keratometric astigmatism was still significantly lower (p < 0.05) after 6 and 12 months after suture adjustment in comparison to status before suture adjustment. In assessment of topographic changes we noticed small continuous increasing of astigmatism (1.27 D after 6 months and 0.2 D after 12 months after suture adjustment). These changes of topographic astigmatism were not statistically significant. The changes of mean corneal refractive power were not statistically significant as well. The mean uncorrected visual acuity increased significantly (from 0.13 to 0.34, p < 0.05) 1 month after suture adjustment. This improvement of uncorrected visual acuity was not significant after 6 and 12 months after suture adjustment. The best-corrected visual acuity improved from 0.37 to 0.61 after one month after suture adjustment but was not statistically significant and stayed still at the same level with minimal changes during follow up time.

Adult↗
PubMed2006

[Correction of the astigmatism with the Artisan phakic toric lens].

The implantation of the intraocular anterior chamber phakic toric lens (PTIOL) Artisan, a product of the Ophtec company, is one of the most up-to-date methods of the correction of higher degree of myopic as well as hyperopic astigmatism. The authors refer about the results of PTIOL Artisan implantation in 6 patients (10 eyes). The major indication was the hyperopic astigmatism--in 5 patients (8 eyes); in one patient the indication was myopic astigmatism. In the followed up group of patients, there is the preponderance of men (5), and one woman only. The patients were divided into two subgroups: one with myopic astigmatism (1 patient, 2 eyes) and other with hyperopic astigmatism (5 patients, 8 eyes). The average age of the whole group at the time of the surgery was 27.7 +/- 2.8 years (range 23-38 years) and the average follow up period was 13.0 +/- 6.9 months (range 6-22 months). In the group the patients with follow up period shorter than 6 months were not included. The average preoperative spherical refractive error was +4.8 +/- 2.25 dioptres (D) and the average astigmatic error was -5.15 +/- 2.82 cylinders (Dcyl). In one case of myopia, the preoperative refractive error in both eyes was -7.0 D and -3.5 Dcyl. The target refraction was emetropia +/- 1.0 D. The authors evaluate the final uncorrected and best-corrected visual acuity (UCVA, BCVA), final postoperative refractive error, presence of intra- as well as postoperative complications, and changes of endothelial cells' density over time. The average final postoperative error in patients with hyperopic astigmatism was +0.72 +/- 0.93 D and -1.08 +/- 0.60 Dcyl. In the only patient with myopic astigmatism the final postoperative error of both eyes was +0.5 D and -0.5 Dcyl. The advantage of the PTIOL implantation is fast visual recovery, potential reversibility of the procedure, maintaining of the accommodation, and stability of the postoperative refraction.

Adult↗
PubMed2006

[The relationship between corneal astigmatism with a vector-based method and whole eye second order wavefront aberrations].

OBJECTIVE: To investigate the relationship between corneal astigmatism and second order wavefront aberration in myopic eyes. METHODS: The corneal astigmatism and the whole eye wavefront aberrations of both eyes of 246 subjects were measured using the Humphrey corneal topography and the WASCA wavefront analyzer. According to axial of the corneal astigmatism, the subjects were divided into five groups (WR(0), WR(180), AR, OA(45) and OA(135)). The corneal astigmatism was decomposed into J(45) and J(0) with a Vector-based method, and correlated with the 2nd order Zernike aberrations (C(3) and C(5)). RESULTS: The mean corneal astigmatisms for the five groups were -1.34 D x 6.87 degrees, -1.03 D x 23.15 degrees, -0.48 D x 89.55 degrees, -0.91 D x 156.87 degrees and -1.02 D x 176.74 degrees respectively. Most of the corneal J(45) and J(0) components were correlated significantly with the C(3) and the C(5) aberrations in the whole eye. While the correlation coefficients (R(2)) between the J(45) and the C(3) were 0.138, 0.119, 0.090, 0.526 and 0.501, the R(2) between the J(0) and the C(5) were 0.711, 0.736, 0.864, 0.866 and 0.785 for the five groups respectively. CONCLUSIONS: The corneal astigmatism plays an important role in determining the 2nd order wavefront aberration in the whole eye, and the combination processes between the corneal and internal astigmatism (compensation and/or addition) change with the axial of the corneal astigmatism.

Adolescent↗
PubMed1991

[Correction of astigmatism by controlled bipolar scleral diathermy. Initial clinical experience].

Twelve eyes (9 patients with an average age of 35.3 years) were treated for astigmatism using temperature-directed bipolar scleral diathermy applied either directly to the limbus or 1 mm from it. The patients were then followed up for a period of 3 to 15 months. Using an electrode distance of 1 mm, diathermy was applied for 2.5-4.5 s until a scleral temperature of 60-65 degrees C was reached. A decrease in astigmatism from 9.5 dpt (s = 5.55) preoperatively to 1.7 dpt (s = 0.98) postoperatively was achieved as the final result. A further increase in astigmatism was noted up to the 3rd postoperative months of up to 5.4 dpt (s = 1.26). The refractive status achieved after this period proved to be stable. Retrogression of the initial effect varied according to the initial condition. Partial recurrence of astigmatism up to 5.16 dpt (s = 1.26) was observed within 6 months in cases of congenital astigmatism. In contrast, following IOL implantation. A further reduction of astigmatism up to 2.5 dpt 3 months postoperatively was noted after an initial reduction from 6.3 dpt (s = 0.25) preoperatively to 3.5 dpt (s = 1.08) postoperatively. Following perforating keratoplasty, one eye that had not been fitted with a contact lens showed a reduction in astigmatism of from 18 preoperatively to 1.2 dpt post-operatively after treatment. Nevertheless, an increase in astigmatism of up to 10.7 dpt was observed after 3 months. In cases with permanent contact lenses after keratoplasty, the situation was different.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Prevalence and variation of astigmatism in a military population.

Astigmatism is a common refractive anomaly. Observations on 1112 consecutive patients from a military optometric clinical population were taken to establish the prevalence of astigmatism and the incidence of its different variations. Astigmatism was found to exist in about 63% of the eyes. It was found that with-the-rule (WTR) and against-the-rule (ATR) astigmatism were the predominant types of astigmatism, and that approximately 70% of astigmatism found required 1.00D of correcting cylinder power or less. One objective of the study was to discover if a statistically significant difference existed between right and left eyes when comparing the mean correcting minus cylinder axes for WTR, ATR, and oblique types of astigmatism. This was shown to exist for WTR and ATR astigmatism. Further studies to determine the etiology of this difference are indicated.

Adult↗
PubMed1994

[Effect of incision form and tunnel length on induced astigmatism with the no-stitch technique].

The frown incision with horizontal suture can induce minimal astigmatism. This method is also currently used with the no-stitch technique. We assess whether it is better than other incisions. Two prospective studies were conducted, altogether including 95 operations in 95 patients. Entry criterion was preoperative astigmatism < 0.75 D. Astigmatism was assessed at 1 week and 4 weeks postoperatively. First study: induced astigmatism with three incision types--frown (A), horizontal arc (B) and limbus-based (C). Second study: induced astigmatism with trapezoid incision--2-mm or 4-mm tunnel. The induced astigmatism did not differ significantly in the three incision types: A 0.82, B 0.67, C 0.8 D. Using the trapezoid incision with 2-mm and 4-mm tunnel the induced astigmatism was 0.3 and 0.38 D, respectively. This difference was also not significant. Thus, neither incision type nor preparation of a longer tunnel has any influence on postoperative induced astigmatism.

Astigmatism↗
PubMed1993

[Surgical correction of high degree corneal astigmatism].

Many patients with high-grade corneal astigmatism cannot tolerate correction with spectacles or contact lenses. In contrast to myopic patients, in these cases visual rehabilitation can only be achieved surgically. In 1990 we started to perform modified corneal T-incisions in cases with high-grade astigmatism and intolerance to glasses or contact lenses. According to the eligibility criteria for selection of patients only 12 eyes were operated on in 1990: 9 eyes were affected by congenital high-grade astigmatism (mean 5.25 D); 1 had 8.5 D astigmatism after perforating injury, keratoplasty and cataract operation; 1 had 2.5 D astigmatism after perforating injury; and 1 eye showed 5.0 D astigmatism following cataract surgery. Without exception, the astigmatism was significantly reduced, from a preoperative mean of 5.25 D to a mean of 2.0 D postoperatively. The most impressive change was the improvement of uncorrected visual acuity. No complications were observed and none of the patients complained of postoperative glare. These results have encouraged us to continue with surgical correction of high-grade corneal astigmatism.

Adult↗
PubMedDate not supplied

Effects of wound architecture and suture technique on postoperative astigmatism.

BACKGROUND AND OBJECTIVE: A prospective randomized investigation was performed to evaluate the effects of wound architecture and suture techniques on postoperative astigmatism after phacoemulsification and intraocular lens implantation. PATIENTS AND METHODS: Two hundred eyes with preexisting with-the-rule astigmatism were randomized into four groups: (1) sutureless scleral tunnel frown incision, (2) scleral tunnel frown incision with a horizontal suture, (3) scleral tunnel frown incision with both a horizontal and a running suture, and (4) posterior limbal acute beveled cataract incision with a running suture. All the incisions were placed in the vertical steep meridian. RESULTS: Data were analyzed from 128 cases with 1-year follow-up. The results revealed that at the 2-month postoperative visit, preexisting astigmatism was significantly reduced in group 1 (P = .029) and significantly increased in groups 3 (P = .020) and 4 (P = .005). There was no significant change in group 2 (P = .06). By the 1-year postoperative visit, there was no significant difference in astigmatism from preoperative levels for all four groups. Vector analysis revealed no significant difference in the mean surgically induced cylinder at 1 year in all four groups. The number of eyes with induced against-the-rule astigmatism, however, was significantly higher than the number of eyes with induced with-the-rule astigmatism in all four groups (P <.01). CONCLUSION: The authors found that sutured wounds placed in the vertical steep meridian may initially increase with-the-rule astigmatism, whereas nonsutured wounds placed in the vertical steep meridian may initially reduce with-the-rule astigmatism. By 1 year, however, a mean flattening of the vertical steep meridian was observed in the three groups with sutures as well as in the group without sutures.

Aged↗
PubMed1996

[Curved lamellar keratotomy for correction of astigmatism. Experimental and initial clinical results].

BACKGROUND: The first experiments for surgical correction of higher astigmatism were reported more than 100 years ago. A lot of different procedures were strongly recommended at the beginning but then abandoned later on because they could not fulfill the expectations regarding the postoperative results and the complications. On the other hand, lamellar preparation of the cataract incision has been considered a major advance in ophthalmology. The main advantage of this incision is that it yields stable postoperative refraction as well as high mechanical stability very early (postoperatively). These findings prompted us to combine the advantages mentioned above with those of the arcuate transverse incision. In this report we present our experimental and clinical results with arcuate lamellar keratotomy. MATERIALS AND METHODS: Experiments were carried out on 22 cadaver bulbi. The optical zones ranged from 6 to 8 mm and the length of the arcuate incisions was between 2 and 7 mm. The clinical data presented here were obtained from 20 patients with a 4-week follow-up. These 20 patients had undergone cataract surgery previously with an induced astigmatism ranging from 2.5 to 5 D. Patients were treated with an optical zone of 7 mm or 8 mm. The length of the arcuate incision was 3 mm. All incisions were paired. RESULTS: Our experiments (cadaver bulbi) showed an approximately linear decrease of the effect with increasing width of the optical zone and increasing are length. Our clinical results demonstrate that the astigmatism induced by our procedure (including potential overcorrection) was 3.41 +/- 1.33 D on the the first day postoperatively. All astigmatism was measured with the Zeiss keratometer. After 1 and 4 weeks the results were 3.98 +/- 1.35 and 3.71 +/- 1.29 D, respectively. The induced astigmatism also depended on the width of the optical zone. In the group with a 7 mm optical zone the induced astigmatism was 4.5 +/- 1.56 D after 4 weeks. This effect was remarkably higher than in the 8 mm group with an average of 3.35 +/- 0.94 D of induced astigmatism. There were no significant differences between visual acuity under glare conditions and the number of endothelial cells preoperatively and at 4 weeks follow-up, nor were there variations in refraction, depending on the time of day. CONCLUSIONS: Due to the relatively high standard deviation of the induced astigmatism we must keep trying to make the results of our procedure more predictable.

Aged↗
PubMed1996

[Outcome of corneal astigmatism after pars plana vitrectomy with or without simultaneous cataract extraction].

Changes in corneal astigmatism induced by pars plana vitrectomy (PPV) (group I, 44 eyes) and PPV combined with no-stitch cataract surgery (group II, 20 eyes) were studied prospectively for a period of at least 3 months. The amount and orientation of the keratometric cylinder and the surgically induced astigmatism (according to the methods of Jaffe and Clayman or Naeser) were analysed. In the first postoperative week both groups exhibited a marked against-the-rule to oblique astigmatism (in group I up to 3.65 +/- 1.40 D, in group II up to 3.05 +/- 1.60 D, according to Jaffe). After 3 months this had declined in group I to 0.40 +/- 0.27 D, whereas a slight induced astigmatism (0.97 +/- 0.41 D) persisted in group II. Gas endotamponade did not significantly aggravate the postoperative astigmatism in either group. Computerized video-keratography generally revealed an asymmetric bowtie pattern during the first week. Our results show that PPV alone induces no appreciable long-term corneal astigmatism. Optical rehabilitation, however, can be delayed by a marked short-term postoperative astigmatism. PPV with simultaneous no-stitch cataract surgery, by contrast, was found to induce a persisting slight astigmatism against the rule.

Adult↗
PubMed1996

The efficacy of a single continuous nylon suture for control of post keratoplasty astigmatism.

PURPOSE: Post operative adjustment of a single continuous suture is an effective means of reducing post keratoplasty astigmatism. This study evaluates post keratoplasty keratometry following suture adjustment with an adjusted suture in place and after the suture is removed. METHODS: Average keratometric astigmatism was measured over 24 months time in 26 patients with an adjusted continuous suture and 24 patients with a continuous suture that was not adjusted. Average keratometry in 43 patients with an adjusted continuous suture was compared with 37 patients with combined continuous and interrupted sutures. Finally, suture out astigmatism in 19 adjusted patients was compared to six patients with no adjustment. RESULTS: There was an increase in average corneal astigmatism over two years of 2.2 diopters in the adjusted group and 1.7 diopters in the non-adjusted group with sutures in place. One year following surgery, average keratometry flattened from 47.5 to 42.9 diopters in the adjusted continuous group and from 47.0 to 46.0 diopters in the group with combined continuous and interrupted sutures. Following suture removal, average astigmatism in patients who had suture adjustment was 4.4 diopters +/- 2.5 diopters (range 1-10 diopters), and 6.01 diopters (range 4-7) in the non-adjusted group. CONCLUSIONS: Average post keratoplasty astigmatism increases after a continuous suture is adjusted but the increase is comparable to patients with acceptable astigmatism who do not require adjustment. More progressive corneal flattening over 12 months time is seen with a continuous suture than which combined sutures. Average suture out astigmatism was 4.0 diopters following suture adjustment, compared to an average of 8.4 diopters prior to adjustment.

Astigmatism↗