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PubMed1998

Paradoxical response to photorefractive treatment for postkeratoplasty astigmatism.

A 42-year-old woman with functionally disabling postkeratoplasty astigmatism in her right eye 3 years after corneal transplantation for keratoconus received photorefractive keratectomy for high astigmatism in that eye. This did not reduce her astigmatism. The procedure was repeated and corneal astigmatism paradoxically increased. The forces within the pseudo-optical ring that cause and maintain astigmatism in corneal transplants may be a significant factor in the unpredictable response of some corneal transplants to excimer photorefractive astigmatism correction.

Adult↗
PubMed1998

Effect of superior and temporal clear corneal incisions on astigmatism after sutureless phacoemulsification.

PURPOSE: To evaluate the effect of superior and temporal clear corneal incisions on astigmatism after sutureless, small incision phacoemulsification. SETTING: World Eye Hospital, Istanbul, Turkey. METHODS: This prospective study evaluated 40 eyes of 20 patients with cataract having bilateral, sutureless, small incision phacoemulsification by the same surgeon. A superior clear corneal incision was used in all right eyes and a temporal clear corneal incision in all left eyes. Mean preoperative astigmatism was 0.63 diopter (D) +/- 0.21 (SD) and 0.65 +/- 0.20 D, respectively. Mean patient age was 66.45 years. Patients were examined preoperatively and 1 day, 1 week, and 1 and 3 months postoperatively. RESULTS: Three months postoperatively, mean astigmatism was 1.60 +/- 0.37 D in the superior incision group and 0.83 +/- 0.19 D in the temporal incision group. Induced astigmatism calculated by vector analysis was 1.44 +/- 0.31 D and 0.62 +/- 0.28 D, respectively. The temporal incision group had significantly lower astigmatism at all follow-ups (P = .000). CONCLUSION: Upper lid pressure on the superior corneal incisions led to fluctuating, against-the-rule astigmatism that was significantly higher than that induced by temporal incisions.

Aged↗
PubMed1999

Laser in situ keratomileusis versus arcuate keratotomy to treat astigmatism.

PURPOSE: To analyze the effectiveness of laser in situ keratomileusis (LASIK) and arcuate keratotomy (AK) to treat simple myopic, compound myopic, and mixed astigmatism. SETTING: Instituto de la Visión, Buenos Aires, Argentina. METHODS: This retrospective nonrandomized study comprised 821 cases treated with LASIK and 46 cases treated with AK. Patients were divided into 4 groups, which had the following preoperative cylinder corrections: simple myopic astigmatism (Group 1) (LASIK: n = 76, -3.91 diopters [D] +/- 1.29 [SD]; AK: n = 5, -3.85 +/- 0.65 D); compound myopic astigmatism up to 2.00 D (Group 2) (LASIK: n = 401, -1.69 +/- 0.76 D; AK: n = 14, -1.48 +/- 0.41 D); compound myopic astigmatism over 2.00 D (Group 3) (LASIK: n = 253, -3.61 +/- 0.89 D; AK: n = 16, -3.09 +/- 0.84 D); mixed astigmatism (Group 4) (LASIK: n = 91, +3.65 +/- 1.62 D; AK: n = 11, 4.39 +/- 0.92 D). RESULTS: Six months postoperatively, the cylinder's vector-corrected change was as follows: Group 1, LASIK 3.75 +/- 1.08 D, AK 3.16 +/- 0.84 D; Group 2, LASIK 1.55 +/- 1.12 D, AK 1.34 +/- 0.44 D; Group 3, LASIK 3.39 +/- 0.98 D, AK 2.70 +/- 1.21 D; Group 4, LASIK 3.77 +/- 1.43 D, AK 3.75 +/- 0.89 D. Respective mean uncorrected visual acuities in each group were as follows: Group 1, 0.71 +/- 0.12 and 0.60 +/- 0.12; Group 2, 0.83 +/- 0.12 and 0.78 +/- 0.24; Group 3, 0.78 +/- 0.18 and 0.48 +/- 0.24; Group 4, 0.69 +/- 0.21 and 0.55 +/- 0.18. CONCLUSIONS: The vector-corrected change and visual acuity achieved with LASIK were better, although not significantly, than those attained with AK except for the UCVA obtained with LASIK in eyes with compound myopic astigmatism over 2.00 D. Both methods proved to be safe.

Astigmatism↗
PubMed1993

The management of post-keratoplasty astigmatism by post-operative adjustment of a single continuous suture.

Penetrating keratoplasty was performed in 39 consecutive patients. A 16 bite 10-0 nylon continuous suture was used. Post-operatively, the suture was adjusted to reduce astigmatism, as determined by refraction, keratoscopy and keratometry. Suture adjustment was performed if astigmatism was over 4 dioptres (D). The suture was tightened in the flatter meridian and loosened in the steeper meridian. Twenty-one patients had suture adjustment performed. Prior to adjustment, mean (+/- standard deviation) astigmatism measured 6.33 +/- 1.38 D. Following adjustment, mean astigmatism was significantly reduced to 2.69 +/- 1.14 D (p < 0.0001). The average final astigmatism for the entire group was 2.66 +/- 1.12 D. The use of a continuous adjustable suture in penetrating keratoplasty significantly reduced the post-operative astigmatism in a group of patients undergoing penetrating keratoplasty.

Adolescent↗
PubMed1996

Post-operative astigmatism control by selective suture removal.

Fifty eyes in 50 patients with > 2.5 dioptres (D) of with-the-rule astigmatism (refraction) following uncomplicated extracapsular cataract extraction were recruited for this prospective study. Selected single sutures were removed and both the amount of astigmatic loss and the change in axis were measured at intervals. After removal of the first suture the mean astigmatic loss at 1 week was 2.9 D by keratometry and the mean change in the axis was 23 degrees (74% occurred within the first hour). The astigmatic loss was greater with subsequent suture removal. Timing of suture removal (before or after 8 weeks) and the amount of initial post-operative astigmatism (more than or less than 5 D) had a minimal effect on the total astigmatic loss. We suggest selective single suture removal can be performed safely at 5-6 weeks post-operatively with removal of a second suture, if necessary, in the steepest axis after 1 hour. The prescription of spectacles should be delayed for 1 week after the final suture has been removed.

Astigmatism↗
PubMed1999

Changes in astigmatism after cataract extraction and intraocular lens implantation in children.

PURPOSE: To evaluate the post-operative changes in astigmatism in pseudophakic eyes in children. METHODS: The charts of children who had undergone surgery for non-traumatic cataract were retrospectively reviewed. In 10 eyes with astigmatism of 3.0 D or more, the refraction was tested and recorded at 1 week, 3 months and 5 months post-operatively. RESULTS: Mean astigmatism 1 week post-operatively was 6.2 +/- 2.7 D (range 3.0-11.0 D). Thereafter, the astigmatic component of the refractive error underwent a spontaneous steady decline, reaching a mean value of 1.2 +/- 1.1 D (range 0-3.0 D) 5 months after surgery. The change in the difference between the mean values at 1 week and at 5 months was statistically significant (p = 0.0002). CONCLUSIONS: Children who underwent cataract extraction and intraocular lens implantation showed a significant spontaneous reduction in astigmatism post-operatively. This finding suggests that there is no need to remove sutures in order to achieve reduction of post-operative astigmatism in these children.

Astigmatism↗
PubMed2002

Changes in astigmatism after congenital cataract surgery and intraocular lens implantation using scleral tunnel incision.

PURPOSE: To evaluate the post-operative changes in astigmatism in pseudophakic eyes in children. Only eyes with astigmatism of 3.0 D or more were included in the study. METHODS: The charts of children who had undergone surgery for non-traumatic cataract, using a scleral tunnel method were retrospectively reviewed. In 11 eyes with astigmatism of 3.0 D or more, the refraction was tested and recorded at 1 week, 3 months and 5 months post-operatively. The paired t-test was used to compare between the variables. RESULTS: Mean astigmatism 1 week post-operatively was 5.8 +/- 3.6 D (range 3.0-14.0 D). Thereafter, the astigmatic component of the refractive error underwent a spontaneous steady decline, reaching a mean value of 2.1 +/- 1.3 D (range 1-4.0 D) 5 months after surgery. The change in the difference between the mean values at 1 week and at 5 months was statistically significant (P < 0.005). CONCLUSION: Children who underwent congenital cataract surgery and intraocular lens implantation showed a significant spontaneous reduction in astigmatism post-operatively.

Astigmatism↗
PubMed1999

Refractive error changes in mixed astigmatism.

The purpose of this note is to examine refractive error changes in children who change from mixed astigmatism to myopic astigmatism. Data were collected for 16 children who changed from mixed astigmatism to simple myopic or compound myopic astigmatism. Children with mixed astigmatism showed minimal refractive changes until they converted to myopic astigmatism, at which time refractive changes increased.

Adolescent↗
PubMed2000

[Para-limbic relaxing incisions for reduction of astigmatism within the scope of catarct surgery].

PURPOSE: Limbal relaxing incision (LRI) is an easy and safe procedure to reduce astigmatism. It should be clarified, whether the effect is discussed controversely, because the varying corneal diameter and consequently the varying LRI position was not considered. PATIENTS AND METHODS: 56 patients aged 76 +/- 9 years with preoperative astigmatism of 1.6 D (0.6 to 7.0 D) underwent an almost astigmatically neutral cataract procedure (3.2 mm temporal clear corneal phacoemulsification with foldable lens implantation) and received independently from the given corneal diameter limbus related relaxing incisions of 80 degrees length and 0.6 mm depth. We performed the paired LRI in 4.5 mm, 5 mm and 5.5 mm distance from the corneal center on the steeper meridian. RESULTS: 4.3 months postoperatively we observed an astigmatic reduction of -1.0 D (-0.1 to -3.2 D) following LRI with a 9 mm optical zone, LRI with 10 mm diameter led to an astigmatic reduction of -0.4 D (-0.1 to -2.9 D) and LRI with 11 mm diameter were followed by an astigmatic reduction of -0.3 D (+0.5 to -1.1 D). Undercorrections were more frequently observed in younger patients, overcorrections more in elderly people. CONCLUSION: The application of three different kinds of limbus related relaxing incisions, with 4.5, 5 and 5.5 mm distance from the corneal center or 9, 10 and 11 mm optical zone respectively, corresponds to the variable anatomic situation of the limbus, therefore leading to nearly predictable data and explaining the divergent results of previous reports. The nearer the LRI is applied to the corneal center, the stronger is the relaxing effect.

Aged↗
PubMed2006

[Astigmatism in ocular neuromuscular nystagmus].

BACKGROUND: Data on refraction of patients with congenital nystagmus are not available in the literature. PATIENTS AND METHODS: We have analysed the refractive errors in a cohort of 224 consecutive patients with congenital nystagmus, aged 1-57 years. RESULTS: Refractive errors, i. e., myopia, hyperopia (> 0.50 dioptres) and astigmatism (> 1.25 dioptres), were found in 179 patients (79.91 %). Of them 8 were myopic (4.46 %), 19 were hyperopic (10.61 %) and 152 were astigmatic (84.91 %). Mean astigmatism was of 2.44 dioptres for right eyes and 2.74 dioptres for left eyes. CONCLUSIONS: Astigmatism is extremely common in congenital nystagmus. Its presence is much higher than that found in normal populations. The amount of astigmatism found in nystagmus patients is noticeable. When considering he visual difficulties of patients with nystagmus, the astigmatic component should be taken in greatest consideration. Its presence should favour early surgery for anomalous head posture. Furthermore, refractive surgery should be considered as early as possible, for improving visual potential.

Adolescent↗
PubMed1996

[Early correction of hyperopia and astigmatism in children leads to better development of visual acuity].

BACKGROUND: From the investigations of Wiesel and Hubel an influence of early spectacle correction of refractive errors on visual development is to be expected. Nevertheless the benefit of early spectacle correction in young children is being discussed controversially. PATIENTS AND METHODS: In a retrospective study the records of 103 strabismic children were analyzed. Myopic children and those with hypermetropia less than 2.0 diopters without astigmatism were excluded from this study. Visual acuity of the dominant eye only was compared between the following subgroups: early spectacle correction (A) not later than at the age of 30 months; "early" spectacle correction (B) between 30 months and 4 years; late spectacle correction (S) after the age of 8 years. In further subgroups we analyzed hypermetropia of more than 3.0 diopters and the combination of hypermetropia and astigmatism of 1.0 diopter or more. Visual acuity was determined using commercially available target projectors 2 times with an interval of at least 3 months. For analysis, the mean of these two examinations was calculated. In all children visual acuity after the age of 8 years was analyzed, the children of group S wore their glasses at least 6 months before the first determination of visual acuity included in this study. The dominant eye was analyzed only. RESULTS: Early corrected eyes developed better visual acuity than late corrected ones: 45% of the early corrected children (A + B) had a visual acuity exceeding 1.0 (20/20) versus 22% in the late corrected (S) subgroup (p = 0.046). 53% of the children corrected within the first 30 months (A) developed a visual acuity exceeding 1.0 (20/20) compared with 22% in the late corrected subgroup (p = 0.019). In hypermetropia exceeding 3.0 diopters (without astigmatism) the difference of early correction (A + B) compared with late correction (S) was even more significant: 72% of early corrected children developed a visual acuity of better than 1.0 (20/20), but no child corrected late did so (p = 0.0015). On the other hand, no child in these 2 subgroups developed a visual acuity of below 1.0 (20/20). Astigmatic eyes had a worse visual acuity: 13% of the early corrected subgroup (A) developed a visual acuity below 1.0 (20/20) versus 55% in the late corrected (S) subgroup (p = 0.024). CONCLUSION: Early correction of hypermetropia (3.0 diopters or more) and of hypermetropic astigmatism (1.0 diopter or more) results in better development of visual acuity as measured at the age of 8 years or later. Since visual acuity of better than 1.0 (20/20) is "normal", late corrected children often did not develop "normal", visual acuity. By early correction of relevant hypermetropia and hypermetropic astigmatism this "refractive amblyopia" at least in part could be avoided.

Astigmatism↗
PubMedDate not supplied

[Comparison of classical keratometry and computer-assisted corneal topography in high grade postoperative astigmatism after perforating keratoplasty].

UNLABELLED: The standard keratometry measures the central corneal refractive power by only four sample points. there is a risk for poor or incorrect measurements in high irregular postoperative astigmatism following penetrating keratoplasty. Therefore we compared the standard keratometry with the computer assisted corneal topography. METHOD: In the study 43 consecutive measurements after penetrating keratoplasty, with an astigmatism > 4 dpt measured with standard keratometry (Zeiss Ophthalmometer), were analyzed. A computer assisted corneal topography (Eye Sys) was performed simultaneously. 22 measurements were received before, 21 measurements after T-incisions. The astigmatism value and axis measured by keratometry and corneal topography were compared and the correlation coefficient were calculated. As a simple index for the asymmetry of the resulting corneal cylinder measured by corneal topography, the frequency and the axis difference of both steep hemimeridians within the 3 mm zone were determined. RESULTS: The astigmatism values measured by standard keratometry (8.1 +/- 2.7 dpt) were significantly higher than the values measured by the computer assisted corneal topography (6.1 +/- 2.2 dpt). The difference of the cylinder axis measured by standard keratometry and corneal topography was 19 +/- 23 degrees; 10 +/- 15 degrees before and 29 degrees +/- 26 degrees after T-incision. The comparison of the astigmatism values showed a correlation coefficient of 0.82 in the total group, of 0.84 before and of 0.83 after T-incisions. In 26% of all measurements the axis difference of both steep hemimeridians (3-mm zone) was more than 30 degrees. After T-incisions this difference increased. CONCLUSIONS: Based on the results of this study, it seems reliable to identificate patients with high postoperative astigmatism following penetrating keratoplasty by standard keratometry.

Adult↗
PubMed2001

Reduction of astigmatism after infancy in children who did and did not wear glasses and have strabismus.

The purpose of this study was to record and explain the changes in astigmatism as normal and strabismic infants grew. Two-hundred-and-eighty-nine hypermetropic infants were randomly allocated to wear glasses from the age of six months. Changes in astigmatism and in hypermetropia of the horizontal and vertical meridia were compared in those who did and did not wear glasses and have strabismus. Mean astigmatism decreased significantly (p < 0.001) in both eyes of normal and strabismic children, but the 'last' astigmatism was significantly (p < 0.001) larger in both eyes of those who had strabismus. There was a similar progressive decrease of hypermetropia in both meridia of both eyes within each diagnostic group, but with the exception of the vertical meridian of the non-fixating eyes (in which the difference approached statistical significance), this was significantly (p < 0.01) larger in the normal children. The consistent wear of glasses was not associated with change in both meridia of both eyes in the normal children (p < 0.005), but had no significant effect on the changes in astigmatism. Since the changes in the two meridia were proportional to the starting level, hypermetropia decreased more in the meridian which was, initially, the more hypermetropic one, and the difference between them, i.e. astigmatism, tended to disappear whether or not the child eventually had strabismus.

Astigmatism↗
PubMed1998

Changes in astigmatism after ptosis surgery measured by corneal topography.

A computerized topographic analysis system (EyeSys [EyeSys Technologies, Houston, TX, U.S.A.]) was used to evaluate corneal astigmatic changes (central corneal power and astigmatic axis) after blepharoptosis surgery on 29 eyelids (22 patients). Fifteen nonoperated eyelids of study patients undergoing unilateral ptosis repair were used as controls. All patients were evaluated preoperatively and again 6 weeks after surgery. Fifteen operated eyelids and five controls were also examined 12 months after surgery to evaluate the stability of these measurements. In 72.4% of operated eyes, corneal topography demonstrated increased with-the-rule astigmatism 6 weeks after surgery, 13.8% of surgical eyes showed increasing against-the-rule astigmatism, and in 13.8%, no change was noted from preoperative measurements. None of the 15 control eyes demonstrated any change in corneal astigmatic axis or significant change in central corneal power. By 12 months after surgery, all of the operated eyes showed a regression toward the amount and pattern of preoperative astigmatism. Only two of 15 eyes maintained a difference of > 0.3 D of central corneal power greater than their preoperative measurement at 1 year. These data suggest that corneal topography may be altered by changes in eyelid position, although the changes appear to be temporary in most patients.

Adult↗
PubMed1998

Correlation between pterygium size and induced corneal astigmatism.

PURPOSE: Before invasion of the visual axis, pterygia typically induce with-the-rule astigmatism, which can be visually significant. In this study, we attempted to assess the quantitative relation between pterygium size and induced corneal astigmatism using corneal topography and digital imaging. METHODS: Thirty-three eyes of 25 patients with primary pterygia were evaluated using corneal topography (TMS), slit-lamp photography, and digital imaging to correlate parameters of pterygium size with induced corneal astigmatism at the 3- and 6-mm optical zones. RESULTS: Pterygia induce asymmetric with-the-rule astigmatism. Lesions extending >45% of the corneal radius or within 3.2 mm of the visual axis produce increasing degrees of induced astigmatism. CONCLUSION: Once pterygia reach a critical size, they induce visually significant central with-the-rule astigmatic changes that may not be apparent by subjective refraction. This finding helps to identify those patients who may benefit from surgical intervention.

Astigmatism↗
PubMed2002

Changes of posterior corneal astigmatism and tilt after myopic laser in situ keratomileusis.

PURPOSE: The purpose of this study was to assess the changes of posterior corneal astigmatism and tilt after laser in situ keratomileusis (LASIK) and to correlate these changes with the amount of correction and the residual stromal bed thickness. METHODS: This prospective nonrandomized (self-controlled) comparative trial included 57 eyes from 14 females and 15 males, whose mean age (+/- standard deviation [SD]) at the time of surgery was 33 +/- 9 years (range, 19-53), with a spherical equivalent (SEQ) of -1.00 to -15.50 (mean, -5.07 +/- 2.81) diopters (D). All LASIK procedures were accomplished with the Keratom II Coherent-Schwind excimer laser and the Moria Model One microkeratome (150-microm head). Subjective refractometry, Orbscan slit-scanning corneal topography analysis, and pachymetry were performed before and 3 months after LASIK for myopia (n= 35; -1.00 to -15.50 D [mean, -4.75 +/- 3.07]) or myopic astigmatism (n= 22; sphere, 0.00 to -9.75 D [mean, -4.75 +/- 2.36]; cylinder, -0.75 to -3.50 D [-1.68 +/- 0.86]). Intended ablation depth ranged from 12 to 108 (mean, 48 +/- 22) microm. Topographic raw data were decomposed into a set of Zernike polynomials as published in detail previously, and parameters for detection of asymmetric mechanical deformation of the cornea were derived. Posterior corneal astigmatism and tilt before and after LASIK were compared, and changes in these variables were correlated with the SEQ change (DeltaSEQ) and the residual corneal bed thickness (RBT). RESULTS: The RBT after LASIK ranged from 186 to 373 (mean, 280 +/- 42) microm. Overall, astigmatism (0.19 +/- 0.07 D/0.22 +/- 0.13 D; p= 0.80) and tilt (3.58 +/- 0.35 degrees /3.65 +/- 0.48 degrees; p= 0.61) did not change significantly by 3 months after LASIK. In eyes with RBT < or =250 microm, the average change in astigmatism (0.05 +/- 0.11 versus 0.01 +/- 0.13 D; p= 0.46) and tilt (0.21 +/- 0.45 degrees versus 0.04 +/- 0.55 degrees; p= 0.30) was not greater than in eyes with RBT > 250 microm. Change in astigmatism (p= 0.19) and tilt (p= 0.56) did not correlate with the RBT during LASIK. CONCLUSIONS: Zernike decomposition of topographic height data discloses that no significant asymmetric mechanical deformation of the posterior corneal curvature occurs after myopic LASIK. Further studies with long-term follow-up are needed to clarify whether this symmetry of the posterior corneal surface can indeed be preserved over time after LASIK if the RBT is < 250 microm.

Adult↗
PubMed2003

Long-term progression of astigmatism after penetrating keratoplasty for keratoconus: evidence of late recurrence.

PURPOSE: To study changes in astigmatism throughout a 20-year period using keratometry and refraction in patients who underwent penetrating keratoplasty (PKP) for keratoconus. METHODS: We reviewed the charts of patients who underwent PKP for keratoconus from 1975 to 1979 and recorded preoperative refraction, stage of keratoconus, laterality of surgery, graft size, suture technique, time of suture removal, keratometry, subjective refraction at 1, 3, 5, 7, 10, 15, 20, and 25 years after suture removal, and slit-lamp findings. RESULTS: Eighty eyes with a mean follow-up of 20 years (range, 15-25) were included in the study. Graft size, suture technique, and time of suture removal had no significant influence on the astigmatism at the last examination. We observed a stabilization of keratometric astigmatism in the first 7 years (4.05 +/- 2.29 D 1 year after suture removal, 3.90 +/- 2.28 D at year 3, 4.03 +/- 2.49 D at year 5, 4.39 +/- 2.48 D at year 7) followed by a progressive increase from 10 years after suture removal until the last follow-up visit (5.48 +/- 3.11 D at year 10, 6.43 +/- 4.11 D at year 15; 7.28 +/- 4.21 D at year 20, and 7.25 +/- 4.27 D at year 25). The mean absolute value of the difference vector (DV) calculated by vector analysis was 7.17 +/- 4.35 D (0-18.33). In 70% of cases, progression of the astigmatism was evident with mean absolute DV of 9.10 +/- 3.65 D. There was a significant correlation between the preoperative and final axis of astigmatism (Pearson r = 0.39, p = 0.0008). There was also a slight positive correlation coefficient between the DV of the eyes in bilateral cases, but it was not significant (Spearman's r = 0.2226, p = 0.34). The major late slit-lamp finding was a peripheral crescent-shaped thinning at the graft-host junction with absence of Bowman's layer on histopathology. CONCLUSION: In spite of refractive stability obtained during the first years after PKP for keratoconus, increasing astigmatism thereafter suggests that there is a progression of the disease in the host cornea.

Adult↗
PubMed1994

Accuracy of Javal's rule in the determination of spectacle astigmatism.

Javal's rule and Grosvenor's simplification of it are commonly used formulas for predicting spectacle astigmatism from keratometric measurements. We assessed the accuracy of these two rules. Spectacle astigmatism was estimated using both rules from measurements of corneal astigmatism on 100 eyes of 100 subjects. These estimates were then compared to the subjectively determined spectacle astigmatism. Grosvenor's simplification of Javal's rule gave slightly more accurate assessments than the original rule. However, only 66% of results gave estimates within 0.50 D, and 7% differed by more than 1.00 D. This can be compared to previous reports on the accuracy of autorefractors, where approximately 95% of cylinder results were within 0.50 D of the spectacle astigmatism. These results indicate that using Javal's rule or Grosvenor's simplification of it to determine spectacle astigmatism from corneal cylinder readings is of limited clinical value.

Adult↗