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PubMedDate not supplied

Artisan toric phakic intraocular lens for correction of astigmatism.

PURPOSE: To assess the safety and efficacy of implanting Artisan toric phakic intraocular lenses (PIOLs) (Ophtec BV, Groningen, The Netherlands) in eyes with high degrees of compound myopic, hyperopic, and mixed astigmatism. METHODS: Twenty-five eyes (20 patients) presenting with high astigmatism were implanted with Artisan toric PIOLs and followed for 1 year. Group 1 included 8 eyes (myopic astigmatism), group 2 included 9 eyes (hyperopic astigmatism), and group 3 included 8 eyes (mixed astigmatism). RESULTS: In the myopic astigmatism group, 8 (100%) of 8 eyes had preoperative uncorrected visual acuity (UCVA) of < or = 20/50, and at 6-month follow-up, 5 (62.5%) of 8 eyes had UCVA of > or = 20/40 (P = .005). In this group, 75% of eyes were within +/- 1.00 diopter (D) of the intended correction. In the hyperopic astigmatism group, 8 (88.9%) of 9 eyes had preoperative UCVA of < or = 20/40, and at 6-month follow-up, 6 (66.6%) of 9 eyes had UCVA of > or = 20/32 (P = .199). Approximately 77.8% of eyes were within +/- 1.00 D of the intended correction. In the mixed astigmatism group, 8 (100%) of 8 eyes had preoperative UCVA of < or = 20/50, and at 6-month follow-up, 6 (87.5%) of 8 eyes had UCVA of > or = 20/40 (P = .007). In this group, 87.5% of eyes were within +/- 1.00 D of the intended correction. The safety index of the procedure was 1.6, 1.3, and 1.3 in the myopic, hyperopic, and mixed astigmatism groups, respectively. The efficacy index of the procedure was 1.2, 1.0, and 1.0 in the myopic, hyperopic, and mixed astigmatism groups, respectively. CONCLUSIONS: Artisan toric PIOLs are safe for the correction of high degrees of astigmatism associated with myopic or hyperopic spherical refractive defect.

Adult↗
PubMedDate not supplied

Standardized analyses of correction of astigmatism by laser systems that reshape the cornea.

PURPOSE: To develop a minimum set of analyses and a format for presentation of outcomes of astigmatism correction by laser systems that reshape the cornea. METHODS: An Astigmatism Project group was created under the auspices of the American National Standards Institute (ANSI) Z80.11 Working Group on Laser Systems for Corneal Reshaping. The Astigmatism Project Group was made up of experts in astigmatism analyses from academia, government, and industry. An extensive literature review was conducted to identify all currently available methodologies for the evaluation of astigmatic outcomes. Project Group members discussed the utility of each method and its specific parameters for evaluating the effectiveness of astigmatism-correcting devices. They gave consideration to unique terminology and analyses required for evaluation of correction of astigmatism by laser systems that reshape the comea. RESULTS: The Project Group defined a comprehensive list of analysis variables needed for the evaluation of astigmatism-correcting devices and generated a mathematical definition for each term. They developed a minimum set of analyses needed for evaluation of astigmatism treatments by laser systems that reshape the cornea. They established methods for calculating the refractive error analysis variables and constructed recommended table and graph formats for data presentation. CONCLUSIONS: This article contains the recommendations of the Astigmatism Project Group of the American National Standards Institute. We propose it as a standard reference for astigmatic refractive error analyses for the evaluation of safety and effectiveness of laser systems that reshape the cornea.

Astigmatism↗
PubMed2000

Pterygium-induced corneal astigmatism.

BACKGROUND: Previous work has suggested an association between increasing size of pterygium and increasing degrees of induced corneal astigmatism. OBJECTIVES: To assess the quantitative relation between pterygium size and induced corneal astigmatism using a computerized corneal analysis system (TMS II) and slit-lamp beam evaluation of pterygium size, and to conclude whether corneal astigmatism is an early indication for surgical intervention. METHODS: We evaluated 94 eyes of 94 patients with unilateral primary pterygium of different sizes, using TMS II and slit-lamp beam measurements of the size of the pterygium (in millimeters) from the limbus to assess parameters of pterygium size with induced corneal astigmatism. Best corrected visual Snellen acuity was performed. RESULTS: Primary pterygium induced with-the-rule astigmatism. Pterygium extending > 16% of the corneal radius or 1.1 mm or less from the limbus produced increasing degrees of induced astigmatism of more than 1.0 diopter. Significant astigmatism was found in 16.16% of 24 eyes with pterygium of 0.2 up to 1.0 mm in size, in 45.45% of 22 eyes with pterygium of 1.1 up to 3.0 mm in size (P < or = 0.0004), and in 100% of 3 eyes with pterygium of 5.1 up to 6.7 mm in size (P = 0.0005). We found that visual acuity was decreased when topographic astigmatism was increased. CONCLUSIONS: When primary pterygium reaches more than 1.0 mm in size from the limbus it induces with-the-rule significant astigmatism (> or = 1.0 diopter). This significant astigmatism tends to increase with the increasing size of the lesion. Topographic astigmatism tends to be improved by successful removal of the pterygium. These findings suggest that early surgical intervention in the pterygium may be indicated when the lesion is more than 1.0 mm in size from the limbus.

Astigmatism↗
PubMed2006

Clinical evaluation of corneal astigmatism in non diabetic and diabetic patients.

This study aimed to measurement of corneal astigmatism in non diabetic and diabetic patient with Keratometry. This perspective study was conducted at Nepal Medical College Teaching Hospital from March to June 2004 to find out clinical evaluation of corneal astigmatism in non diabetic and diabetic patients. A total 224 patients were include. Corneal astigmatism readings with the Takagi KM-1 Sutcliff type Keratometry was obtained by single examiners on 130 non diabetic patients (where as 112 right eye and 109 left eye) and 94 diabetic patients (both eyes) corneas. Corneal dioptric and magnitude of astigmatism were assessed. Average corneal diopters were 43.88 and 43.81 in non diabetic and diabetic cases. Average corneal astigmatism was 0.30 D and 0.07D in non diabetic and diabetic cases. Less astigmatism present on diabetic patient to compare non diabetic patients in total and both sex. Chances of diabetes mellitus are more visible in non astigmatism patient compare to astigmatism patients in both sexes (Table-1 and 2). No difference in astigmatic rule i.e. with the rule astigmatism in both diabetic and non diabetic patients but less astigmatism present in diabetic one.

Adolescent↗
PubMed1993

[Effect of pterygium operation on preoperative astigmatism. Prospective study].

High-grade corneal astigmatism is considered to be an indication for pterygium surgery. However, no prospective studies have been carried out to determine whether a pterygium operation really reduces preoperative astigmatism. Therefore, we prospectively examined 23 patients who were operated on for pterygia at the University Eye Clinic in Freiburg in 1991. Pre- and postoperative corneal astigmatism was measured by ophthalmometry or retinoscopy. Preoperative astigmatism after pterygium surgery was reduced or unaltered in 19 patients. In 4 patients, the postoperative astigmatism was increased. The mean preoperative astigmatism was 2.41 D in the horizontal meridian, the postoperative astigmatism 1.29 D. The reduction was statistically significant (P < 0.0001, Wilcoxon test). The higher the preoperative astigmatism, the higher the difference between pre- and postoperative astigmatism (r2 = 0.88, P = 0.0001). Our technique of pterygium surgery (free conjunctival transplant after polishing the cornea, limbus, and sclera) reduces preoperative astigmatism. Thus, high-grade astigmatism can be regarded as an indication for pterygium surgery.

Astigmatism↗
PubMed1989

Long-term evolution of astigmatism following planned extracapsular cataract extraction.

Sixty-six eyes of 66 patients undergoing planned extracapsular cataract extraction with interrupted 10-0 nylon suture wound closure were followed up prospectively for three years following surgery to evaluate the long-term evolution of postoperative astigmatism. The study examined the period beginning three months postoperatively, well after all suture cutting was completed, a point often considered to represent "final postoperative astigmatism." For the group as a whole, the induced astigmatism measured at three months was not stable, but gradually shifted 0.69 diopter toward against-the-rule astigmatism. Three specific patterns of evolution of postoperative astigmatism were identified, depending on the amount of induced astigmatism found at three months. The data revealed that it was not possible to consistently induce with-the-rule astigmatism, although permanent against-the-rule induced astigmatism could be produced. The long-term evolution of postoperative cataract wounds toward more against-the-rule astigmatism seen in this study was not affected by the number of intact nylon sutures. Proper evaluation of any technique to modify postoperative astigmatism must consider the long-term evolution of the cataract wound.

Aged↗
PubMed2001

Topographic analysis of astigmatism induced by scleral shortening in pig eyes.

BACKGROUND: Corneal astigmatism is a severe postoperative problem in foveal translocation surgery. We evaluated the corneal astigmatism induced by scleral shortening in pig eyes in vitro. METHODS: We created three sizes of scleral shortening in pig eyes and examined the preoperative and postoperative corneal astigmatism. The three sizes of scleral shortening were; 6 mm x 12 mm, 9 mm x 12 mm, and 6 mm x 16 mm (radial x circumferential). The shortenings were created 11 mm from the limbus with 10 eyes in each group. Videokeratographic measurements were performed using the CAS System 2000, preoperatively and postoperatively, and the astigmatism caused by the scleral shortening was evaluated. RESULTS: The surgically-induced astigmatism was 2.1 +/- 1.2 diopters (D) in the 6 mm x 12 mm group, 5.2+/-1.5 D in the 9 mm x 12 mm group, and 3.7+/-1.0 D in the 6 mm x 16 mm group. Corneal astigmatism caused by scleral shortening depended on both the radial and circumferential shortening. Pre- and postoperative topographic corneal maps showed an irregular astigmatism pattern (lazy bowtie pattern). Because the central zone of the cornea showed a relatively regular astigmatism, the corneal astigmatism induced by scleral shortening did not affect the predicted corneal acuity. CONCLUSIONS: In foveal translocation surgery with scleral shortening, an excessive scleral resection in the radial direction can cause clinically intolerable regular and irregular astigmatism. Minimal scleral shortening that will satisfy the required translocated distance is recommended to reduce the risk/benefit ratio.

Animals↗
PubMedDate not supplied

Relationship between astigmatism and aging in middle-aged and elderly Japanese.

PURPOSE: To study the effect of aging on astigmatism in adult Japanese. METHODS: Measurements of refractive errors and keratometry were performed on 2161 randomly selected subjects (aged 40-79 years). The relation between age and the net value in diopters (D) of astigmatism was evaluated with a trend test. The relation between age and the polar value was also examined by linear regression analysis. RESULTS: The mean (+/-SD) value of total and corneal astigmatism was -0.97 +/- 0.72 D and -0.86 +/- 0.63 D, respectively, and the net value of both increased with age (P trend < 0.001). The prevalence of either type of astigmatism also increased with age, according to the Cochran-Mantel-Haenzel test (P < 0.0001 for total and P < 0.01 for corneal astigmatism). The prevalence of against-the-rule astigmatism increased with age for either type of astigmatism (P < 0.0001 for total, P < 0.0001 for corneal). According to the analysis of polar values by age, the regression coefficient (+/-SE) for total and corneal astigmatism was -0.024 +/- 0.002 (P < 0.0001) and -0.028 +/- 0.002 (P < 0.0001), respectively. There was no statistical difference between these two regression coefficients. CONCLUSIONS: The prevalence of astigmatism increases and the axis turns to against-the-rule with age. The result of the linear regression analysis indicates that the age-related change in astigmatism is mainly associated with changes in the cornea.

Adult↗
PubMed2005

Standardized arcuate keratotomy for postkeratoplasty astigmatism.

PURPOSE: To assess the effect of standardized, paired arcuate keratotomy (AK) on the change in astigmatism in postkeratoplasty eyes. SETTING: Moorfields Eye Hospital, London, United Kingdom. METHODS: A retrospective review was conducted of 20 eyes of 19 patients having the same AK procedure regardless of the magnitude of the preoperative astigmatism. Each eye had a pair of 60-degree arc length incisions placed in the corneal stroma. The incisions were 600 mum deep and 6.0 mm apart. The preoperative and postoperative refractions and complications were analyzed. Astigmatic change was analyzed without regard to axis, as surgically induced refractive change, and using a modified polar plot of change in astigmatism. RESULTS: The mean cylinder was reduced from -10.99 diopters (D) +/- 4.26 (SD) to -3.33 +/- 2.18 D. There was no significant change in the mean spherical equivalent. There was a strong correlation between the magnitude of the preoperative cylinder and the magnitude of the change in astigmatism (R2 = 0.76). In 3 eyes, the surgically induced axis of astigmatism was more than 15 degrees from that expected. CONCLUSIONS: In postkeratoplasty eyes, the change in the magnitude of astigmatism induced by standardized AK was proportional to the preoperative magnitude of astigmatism. Arcuate nomograms for congenital astigmatism have no role in the management of astigmatism in postkeratoplasty eyes.

Adult↗
PubMed2004

Artisan toric lens implantation for correction of postkeratoplasty astigmatism.

PURPOSE: To determine the efficacy of Artisan toric iris-fixated lens implantation after penetrating keratoplasty to correct high ametropia and astigmatism. DESIGN: Prospective, noncomparative case series. PARTICIPANTS: Artisan toric lens implantation was performed in 16 eyes of 16 patients who were contact lens intolerant or were unable to wear glasses because of anisometropia, high astigmatism, or both. INTERVENTION: Sixteen eyes of 16 patients received Artisan toric lenses for postkeratoplasty astigmatism, anisometropia, or both. MAIN OUTCOME MEASURES: Manifest refraction, uncorrected and spectacle-corrected visual acuity, and corneal topography were performed before surgery and 1, 3, 6, 12, and 18 months after surgery. Efficacy, percent reduction of refractive astigmatism, topographical astigmatism, anisometropia of defocus, and the astigmatism correction index were determined. A patient satisfaction questionnaire and specular microscopy results were assessed. RESULTS: The mean +/- standard deviation of the preoperative refractive cylinder was -6.66+/-1.93 diopters (D; range, -4.0 to -10.0 D), which was reduced to -2.08+/-1.33 D, -2.14+/-1.76 D, -1.98+/-1.65 D, -1.84+/-0.77 D, and -1.42+/-0.78 D at 1 month, 3 months, 6 months, 12 months, and the final follow-up examination (8.4+/-4.9 months), respectively. Spherical equivalent was reduced from -4.90+/-5.50 D before surgery to -0.96+/-0.86 D at the final follow-up. The uncorrected and best-corrected visual acuities were >/=20/40 in 42% and 100% of eyes, respectively. There was no loss of best-corrected visual acuity and a gain of at least 2 lines in 50% of eyes. The percent reduction in refractive astigmatism, topographical astigmatism, and anisometropia of defocus were 78.0+/-11.5%, 20.3+/-34.9%, and 77.0+/-12.0%, respectively. The astigmatism correction index was 102.8+/-18.6%. Satisfaction increased from 3.2 to 8.3 after implantation. The endothelial cell loss was 7.6+/-18.9% at 3 months and 16.6+/-20.4% at the last follow-up. In 1 patient, a reversible graft rejection occurred. CONCLUSIONS: Artisan toric lens implantation after penetrating keratoplasty was effective for reduction of refractive astigmatism and ametropia. All patients were suitable for spectacle correction after implantation. A longer follow-up and a larger number of patients are needed to assess the safety and the effect of the lens on the corneal graft endothelium.

Adult↗
PubMed1996

Corneal astigmatism after phacoemulsification and lens implantation through unsutured scleral and corneal tunnel incisions.

PURPOSE: We compared the changes in corneal astigmatism after phacoemulsification and intraocular lens implantation in 93 consecutive eyes with unsutured 4-mm superior scleral tunnel incisions to those through 105 consecutive eyes with unsutured 3.2- to 3.5-mm temporal corneal tunnel incisions. METHODS: Keratometry measurements were obtained preoperatively and at postoperative day 1, week 1, and week 6. Group differences in scalar and vector astigmatism were compared by using analysis of variance methods. RESULTS: Mean scalar astigmatism in the scleral incision group changed from preoperative astigmatism by 0.65 diopter at postoperative day 1, 0.37 diopter at postoperative week 1, and 0.13 diopter at postoperative week 6. Mean scalar astigmatism in the corneal incision group changed from preoperative astigmatism by 0.39 diopter at postoperative astigmatism by 0.39 diopter at postoperative day 1, 0.21 diopter at postoperative week 1, and 0.13 diopter at postoperative week 6. Mean vector astigmatism in the scleral incision group changed 1.26 diopters at 80 degrees at postoperative day 1, 1.05 diopters at 83 degrees at postoperative week 1, and 0.42 diopter at 103 degrees at postoperative week 6. Mean vector astigmatism in the corneal incision group changed 0.77 diopter at 90 degrees at postoperative week 1, and 0.61 diopter at 89 degrees at postoperative week 6. The differences were statistically significant (P = .003) only by vector analysis at the postoperative day 1 examination. CONCLUSIONS: We found significantly greater with-the-rule change in astigmatism in the scleral incision group than in the corneal incision group on the first postoperative day. The effect disappeared by the sixth postoperative week.

Astigmatism↗
PubMed1987

Relaxing incisions with augmentation sutures for the correction of postkeratoplasty astigmatism.

We performed a prospective study of relaxing incisions with augmentation sutures in 21 patients who were unable to wear spectacles or contact lenses after penetrating keratoplasty because of high astigmatism. The mean preoperative astigmatism was 9.37 diopters (range, 4.50 to 14.50 diopters), and the mean postoperative astigmatism was 3.73 diopters (range, 0.00 to 7.00 diopters). The net decrease in astigmatism was 6.56 diopters (range, 1.00 to 11.00 diopters), which represents a 67% decrease in astigmatism. The mean vector corrected change in astigmatism was 8.40 diopters (86%). These results were compared with those of our previous study of relaxing incisions without sutures. Overall, there was a significantly greater decrease in astigmatism (67% vs 47%, P = .009) when augmentation sutures were placed 90 degrees away from the relaxing incisions. Furthermore, in patients with more than 8.50 diopters of astigmatism, relaxing incisions with sutures yielded a much greater reduction in astigmatism compared with relaxing incisions without sutures (70% with sutures vs 39% without sutures, P = .002). We recommend relaxing incisions with augmentation sutures as the initial surgical procedure in eyes with more than 8.50 diopters of astigmatism.

Astigmatism↗
PubMedDate not supplied

Does a tilted retina cause astigmatism? The ocular imagery and the retinoscopic reflex resulting from a tilted retina.

An astigmatic dial viewed by a tilted retina will have only one line in focus, simulating astigmatic blur. We compare and contrast this optical situation to actual astigmatism. Photographs were taken of an astigmatic dial blurred with a cylindrical lens, and also of the same astigmatic dial tilted, simulating tilted retinal imagery. A model eye for retinoscopy practice was provided with a retina tilted 30 degrees and was retinoscoped repeatedly with and without added confounding cylinder by five skilled retinoscopists. Photographs of the astigmatically blurred and tilted astigmatic dials were similar but not identical, as expected. The model eye with tilted retina showed no astigmatism by retinoscopy in 14/15 measurements and 0.25 D of astigmatism in one measurement. When confounding cylinder was present, the retinoscopic measurement was always within 0.25 D of the added cylinder. The ocular imagery resulting from a tilted retina can simulate astigmatic blur, but this is actually due to a type of curvature of field. Only a minute area of the tilted retina is viewed during retinoscopy, so the tilt has essentially no influence on the retinoscopic reflex.

Adult↗
PubMed1997

Optic disc shape, corneal astigmatism, and amblyopia.

OBJECTIVE: The cornea and the optic disc form the anteroposterior opening of the sclera. This study evaluated whether an abnormal shape of the optic disc is associated with an abnormal configuration of the cornea measured as corneal astigmatism. DESIGN: The study design was a cross-sectional one. PARTICIPANTS: The study included 882 subjects (430 women, 452 men) with a mean age of 45.9 +/- 13.6 years (mean +/- standard deviation; range, 8-87 years) and a mean refractive error of -1.09 +/- 2.76 diopters (range, -21.0 diopters to +7.0 diopters). INTERVENTION: Corneal astigmatism was determined by keratometry, and the optic disc was analyzed morphometrically by planimetric evaluation of optic disc photographs. MAIN OUTCOME MEASURES: Corneal astigmatism, ratio of minimal-to-maximal disc diameter, and optic disc form factor were measured. RESULTS: The amount of corneal astigmatism was significantly (P < 0.001) correlated with an increasingly elongated optic disc shape. Corneal astigmatism was significantly (P < 0.01) higher in eyes with tilted discs. It was significantly (P = 0.006) smaller in eyes with an almost circular disc shape. Amblyopia was significantly (P < 0.05) associated with an elongated optic disc shape and high corneal astigmatism. The axis of corneal astigmatism was correlated with the orientation of the longest disc diameter. The optic disc was significantly (P < 0.05; chi-square test) more often horizontally oval in eyes with a steeper horizontal corneal meridian than in eyes with a steeper vertical corneal meridian. Correspondingly, the disc was significantly (P < 0.05) more often vertically oval in eyes with a steeper vertical corneal meridian than in eyes with a steeper horizontal corneal meridian. CONCLUSIONS: An abnormal optic disc shape is significantly correlated with corneal astigmatism. Especially in young children, if an abnormal optic disc shape is found on routine ophthalmoscopy, refractometry should be performed to rule out corneal astigmatism and to prevent amblyopia. The direction of the longest optic disc diameter can indicate the axis of corneal astigmatism.

Adolescent↗
PubMed1997

Astigmatism induced by spherical photorefractive keratectomy corrections.

PURPOSE: The purpose of the study is to evaluate the induced astigmatism after spherical photorefractive keratectomy on the Summit Omnimed (Summit Instruments, Waltham, MA) and the Nidek EC-5000 (Nidek Co. Ltd, Aichi, Japan) excimer lasers. METHODS: A total of 4269 eyes of 3289 patients were treated with a 5-mm optical zone using the Summit Omnimed excimer laser and 1825 eyes of 1303 patients treated with the Nidek EC-5000 excimer laser. The final astigmatic refractive outcome was compared with the initial refraction by vector analysis (Alpin and Jaffe method). RESULTS: Subjective astigmatic refraction for the Summit laser reduced from a mean of -0.39 diopter (D) +/- standard deviation (SD) 0.33 D (range, 0 to -2.50 D) to -0.33 D +/- SD 0.41 D (range, 0 to -3.00 D). Surgically induced astigmatism (SIA) had a mean of 0.42 +/- SD 0.34 D (range, 0 to 2.89 D). Mean SIA increased with increasing preoperative astigmatism by 0.60 D SIA for every 1.00 D of preoperative cylinder. For the Nidek laser, subjective astigmatic refraction changed from a mean of -0.18 D +/- SD 0.21 D (range, 0 to -1.25 D) to -0.30 D +/- SD 0.33 D (range, 0 to -3.00 D). Surgically induced astigmatism had a mean of -0.32 D +/- SD 0.29 (range, 0 to 3.05 D). Mean SIA increased with increasing preoperative astigmatism by 0.47 D SIA for every 1.00 D of preoperative cylinder. CONCLUSIONS: The authors show that spherical photorefractive keratectomy corrections can induce significant astigmatic change, particularly if a large amount of preoperative astigmatism is present.

Astigmatism↗
PubMed1997

Association between total astigmatism and myopia.

PURPOSE: To determine whether there is an association between degree of myopia and total astigmatism. SETTING: St. Paul's Eye Unit, Royal Liverpool University Hospitals, Liverpool, United Kingdom. METHODS: Refractive and keratometric data for 105 eyes of 105 patients with myopia and astigmatism who attended a photorefractive keratectomy (PRK) assessment clinic were analyzed. The refractive data of the patients having PRK were also analyzed before and after treatment. RESULTS: There was a strong correlation between total astigmatism (A) and degree of myopia. This could be represented by a linear regression line in the form A = -0.13 x myopia + 0.86 (at the corneal plane). Although there were trends, there was no significant correlation between the degree of corneal (keratometric) astigmatism and myopia. Data of 35 patients who had PRK were analyzed to determine whether the observed effect on astigmatism could have been predicted from the relationship between myopia and astigmatism. Forty-nine percent of patients with myopia and astigmatism were overcorrected by 0.6 diopter (D) (0.2 to 2.0 D), resulting in a preoperative to postoperative axis shift of 73 degrees; 40% were undercorrected by 1.2 D (0.5 to 3.1 D). Both over- and undercorrections could have been predicted from the relationship between myopia and astigmatism. CONCLUSIONS: The total amount of astigmatism in the myopic eye is proportional to the degree of myopia. The amount that one intends to treat should, therefore, be modified according to the amount of myopia to be treated, as determined by the relationship between the degree of astigmatism and myopia.

Adult↗
PubMed1997

Postoperative astigmatism and relative strength of tunnel incisions: a prospective clinical trial.

PURPOSE: To investigate the influence of incision depth and site on wound strength and postoperative astigmatism. SETTING: Virchow Memorial Hospital Eye Clinic, Berlin, Germany. METHODS: In this prospective, randomized study, 180 patients with a 7.0 mm tunnel incision depth of 300 and 500 microns; limbal incision and scleral incision; temporal scleral incision and scleral incision at the 12 o'clock position; temporal limbal incision and limbal incision at the 12 o'clock position. Postoperative astigmatism was measured by keratometry and videokeratoscopy 1 day, 1 and 4 weeks, and 8 months postoperatively. Wound strength was measured with an ophthalmodynamometer on the first postoperative day and after 1 week at the site with the least mechanical stability adjacent and posterior to the primary incision. RESULTS: The temporal incision, which was performed 1.0 mm behind the surgical limbus, led to induced astigmatism of 0.65 diopters (D) +/- 0.23 (SD) after 8 months. When incision was at the 12 o'clock position, the induced astigmatism was 0.97 +/- 0.41 D. Induced astigmatism was highest following a limbal incision in the 12 o'clock position (1.33 +/- 0.63 D). This effect was less pronounced with a temporal incision. Incision depth did not significantly influence induced astigmatism. An incision depth of 500 microns led to induced astigmatism of 0.94 +/- 0.50 D; a depth of 300 microns led to induced astigmatism of 0.78 +/- 0.64 D. After 1 week, wound strength was highest with temporal scleral incisions (38.6 +/- 2.1 kPa by ophthalmodynamometer) and lowest with limbal incisions in the 12 o'clock position (30.8 +/- 7.7 kPa). CONCLUSIONS: Incisions site significantly influenced mechanical wound strength and induced astigmatism; incision depth influenced neither. In general, incisions in the 12 o'clock position induced more astigmatism than temporal incisions.

Aged↗
PubMed1997

[Limbus-parallel keratotomies with compression sutures in treatment of high astigmatism after perforating keratoplasty: a vector analysis and topographic study].

BACKGROUND: Visual acuity following penetrating keratoplasty is frequently limited by excessive astigmatism which cannot be compensated for with spectacles or contact lenses. The purpose of the study was to determine the effects of arcuate keratotomies and compression sutures on the amount and regularity of corneal astigmatism and on the visual acuity. PATIENTS AND METHODS: Between June 1989 and August 1995, 56 eyes from 56 patients (30 women, 26 men, average age 53 +/- 16 years) with excessive post-penetrating keratoplasty astigmatism were treated with paired arcuate cuts and compression sutures 4.8 +/- 3.5 years after suture removal (45% keratoconus, 30% scars, 20% dystrophies). The incisions were made along the meridian of maximum dioptric power in a sector extending for 60 +/- 15 degrees (6 mm diameter). Incision depth was standardized at 450 microns. Compression sutures were placed 90 degrees away in the flat meridian. Eight patients required more than one procedure to obtain the desired effect. Best corrected visual acuity (VA), keratometric readings and topographic power maps were analyzed pre- and postoperatively. We categorized the topographic maps into six groups: from group 1 (regular) to group 6 (irregular). For description of the astigmatic change after surgery, the formulas by Naylor and Jaffe (vector-corrected astigmatism) were applied. RESULTS: The mean preoperative astigmatism was 10.8 +/- 3.1 (4.2 to 19.2) diopters (D). After a mean follow-up of 1.1 years, the mean net astigmatism was 5.8 +/- 3.2 (0 to 16) D. The mean preoperative visual acuity (VA) was 0.38 +/- 0.31 (from 0.03 to 1.0). At the end of follow-up, the mean VA was 0.43 +/- 0.25. Non-refractive reasons for poor visual acuity included amblyopia (n = 5), macular degeneration (n = 4), glaucoma (n = 4), cataract (n = 2), and others (n = 5). Twenty-seven percent of the preoperative topographic maps were categorized into groups 1 and 2 and only 10% into groups 5 and 6. At the end of the follow-up, none of the 53 available topographic maps was categorized into group 1, 7.5% into group 2 and 30% into groups 5 and 6. The mean astigmatic change (vector-corrected astigmatism) was 12.3 +/- 5.2 (1.0 to 29.8) D with a turn of the axes ranging from -39 to 44 degrees. CONCLUSIONS: Arcuate incisions with compression sutures are easily performed and hold a low complication rate in comparison with other refractive operations. Definition of successful surgery is even broader when a significant reduction of astigmatism that usually allows the use of spectacles or contact lenses is considered. A disadvantage is that each particular case is unpredictable because of the tendency of the topography to irregularity and possible regression of the effect.

Adult↗