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PubMed1987

Longitudinal study of postoperative astigmatism.

A prospective longitudinal study of 503 eyes that had extracapsular cataract extraction with posterior chamber intraocular lens implantation was conducted. Each patient was followed for a minimum of one year. Data were collected, analyzed, and the following information ascertained: temporal behavior of induced keratometric and cylindrical changes, induced with-the-rule, against-the-rule, and oblique astigmatism, comparison of keratometric and refractive astigmatism, and the effect of cutting sutures upon induced astigmatism. Though a large amount of with-the-rule astigmatism was immediately induced after surgery, by the end of one year over 60% of patients shifted toward against-the-rule.

Astigmatism↗
PubMed1989

Analysis of astigmatic keratotomy.

Eighty-two keratotomy procedures were performed for both idiopathic and postsurgical astigmatism or myopic astigmatism and analyzed for efficacy using vector and linear regression analysis. Delta keratometry values (delta K) were computed for each case as delta K in the desired axis of effect using vector analysis. Six different procedures were compared including both intersecting and nonintersecting trapezoidal keratotomy, relaxing incisions with compression sutures, T cuts with radial keratotomy, T cuts alone, and RK with elliptical optical zones. Our results showed that the greatest shifts occurred in the trapezoidal groups, whereas the most predictable effects occurred in the relaxing incision/compression suture group. Astigmatic keratotomy is capable of producing large shifts in corneal astigmatism; however, the accuracy of these procedures remains highly variable.

Adult↗
PubMed1989

Refractive evaluation of astigmatic keratotomy procedures.

We evaluated the efficacy of three transverse incision astigmatic keratotomy procedures using a vector analysis that enabled us to determine the magnitude of the effect and the axis in which it occurred. These procedures were used for low levels of astigmatism (0.5 diopter [D] to 3.75 D): (1) staggered, radial-touching transverse (T) incisions, (2) non-radial-touching T incisions, and (3) T incisions with interrupted radial. Most procedures were performed in conjunction with radial keratotomy for spherical correction of myopia. The non-radial-touching T procedure was the least effective method of reducing astigmatism. The staggered, radial-touching T and T with interrupted radial procedures were equally effective in reducing over 93% (on the average) of the preoperative astigmatism. Of these two procedures, the T with interrupted radial procedure was the most accurate, with the effect of the surgery deviating less than ten degrees from the desired axis in over 70% of the eyes.

Adult↗
PubMed1996

Multivariate analysis versus vector analysis to assess surgically induced astigmatism.

PURPOSE: To present a multivariate probability computation method for assessing surgically induced astigmatism. SETTING: Department of Ophthalmology, Rennes University Hospital, Rennes School of Medicine, France. METHODS: The multivariate method was used to evaluate 100 patients who had cataract surgery by phacoemulsification. Keratometry was recorded on the day before and 12 days after surgery. Surgically induced astigmatism was assessed by the multivariate method as well as by most of the published vector analysis methods. RESULTS: The mean surgical induced astigmatism (+/- SD) with the multivariate analysis was 1.18 +/- 0.36 diopters (D) for the cylinder power and 25.00 +/- 5.50 degrees for the cylinder axis. With the vector analysis, the mean surgically induced astigmatism was 1.67 +/- 0.54 D with the Naylor, Jaffe, and Holladay methods; 0.45 +/- 0.30 D with the latest Naeser method; 1.34 +/- 0.38 D with the Cravy method (Cravy's vector); and -0.05 +/- 0.42 D for Cravy's delta K. CONCLUSION: Although vector methods constitute interesting geometrical models, their number and their lack of linearity and explicit expression of results make them unsuitable for statistical analysis. Instead, a reliable, easily programmable method that uses existing software is recommended.

Astigmatism↗
PubMed1996

Transverse keratotomy to correct high corneal astigmatism after cataract surgery.

PURPOSE: To assess the outcome of transverse keratotomy to correct high corneal astigmatism after cataract surgery. SETTING: Vall d'Hebron Hospital, Department of Ophthalmology, Cornea and Refractive Surgery Unit, Barcelona Autónoma University, Spain. METHODS: Thirty-two eyes with regular corneal astigmatism between 2.50 and 5.00 diopters (D) after previous cataract surgery had two transverse incisions with an optical zone of 5.0 or 7.0 mm, a depth of 80 or 90%, and a length of 3.0 or 4.0 mm, depending on the amount of astigmatism and based on a personal nomogram we developed. RESULTS: From 80 to 100% of the desired correction was achieved in 38.7% of eyes and from 60 to 80% in 38.9%. At 6 months, only 9.1% had a keratometric change of more than 0.50 D. Best corrected visual acuity was the same or better in 85.2% of patients; no patient lost more than one Snellen line. CONCLUSION: This easy, safe technique had low anatomical and refractive morbidity and high efficacy, making it an excellent option for eyes with high astigmatism after cataract surgery. More research is required in view of the considerable unpredictability of our results and the disparity in methods and results of other published studies.

Astigmatism↗
PubMed1997

Using a reference point and videokeratography for intraoperative identification of astigmatism axis.

PURPOSE: To estimate the misalignment of the astigmatism axis caused by intraoperative identification of the axis without using reference points. SETTINGS: Osaka University Medical School, Suita, Japan. METHODS: This study included 38 eyes of 19 patients with no ocular pathology except refractive error and 32 eyes of 16 patients with cataract. A point was marked on the nasal conjunctiva, on the "intraoperative" horizontal axis as estimated by the examiner using a surgical microscope while the patient lay on the operating table in the supine position. Videokeratography was performed with the patient seated, and the degree of axial misalignment was determined by measuring the angle between the conjunctival mark and the horizontal axis identified on the video image. RESULTS: Mean axial misalignment for all patients was 4.4 degrees +/- 2.8 (SD), which could theoretically cause about a 15% loss of surgical effect. The maximal misalignment was 14 degrees, which would correspond to a 48% loss of astigmatic correction. CONCLUSION: The results of this study suggest that intraoperative identification of the astigmatism axis without using reference points may reduce the surgical effect because of axis misalignment. The use of a reference point and preoperative videokeratography may increase the accuracy of identification of the astigmatism axis.

Adult↗
PubMed1997

Effect of nylon suture diameter on induced astigmatism after phacoemulsification.

PURPOSE: To prospectively compare the clinical results of 10-0 and 9-0 monofilament nylon sutures after phacoemulsification with poly(methyl methacrylate) intraocular lens implantation through a 4.0 mm cruciate incision. SETTING: Department of Ophthalmology, Ramón y Cajal Hospital, Madrid, Spain. METHODS: One hundred eyes with cataract were randomly assigned to have surgery using a 10-0 or a 9-0 nylon suture. Except for suture diameter, identical surgical methods were used in every case. Data on uncorrected visual acuity, keratometry and postoperative astigmatism were analyzed up to 12 months after surgery. RESULTS: Both groups had similar uncorrected visual acuity. Mean postoperative corneal astigmatism was against the rule in the 10-0 nylon suture group and with the rule in the 9-0 nylon suture group. Significant differences were found between groups (P < .05). CONCLUSION: Both suture diameters offered satisfactory clinical results. Patients with preoperative with-the-rule astigmatism might benefit from 10-0 nylon sutures and those with preoperative against-the-rule astigmatism, from 9-0 nylon sutures.

Aged↗
PubMed1997

Correcting postoperative astigmatism using curved lamellating keratotomy.

PURPOSE: To ascertain whether the change in refraction caused by paired lamellating corneal incisions in cadaver eyes could be achieved in living eyes and whether wound healing influences this effect. SETTING: Virchow Hospital Eye Clinic, Humboldt University, Berlin, Germany. METHODS: This prospective study included 45 patients who had a follow-up of 15 months. All had astigmatism of at least 2.00 diopters (D) induced by previous cataract surgery. Optical zones of 7.0 and 8.0 mm and chordal lengths of 3.0 and 5.0 mm were used. All incisions were paired. RESULTS: Mean preoperative astigmatism measured with a keratometer was 3.64 D +/- 0.89 (SD). After 15 months, it was 1.00 +/- 0.76 D, and mean induced astigmatism was 3.18 +/- 1.30 D. The 7.0 mm group had a mean induced astigmatism of 3.93 +/- 1.52 D, which was significantly higher than that in the 8.0 mm group (mean 2.60 +/- 0.74 D) at a uniform chordal length of 3.0 mm. Mean uncorrected visual acuity was 0.26 +/- 0.14 preoperatively and 0.50 +/- 0.28 after 15 months; mean corrected visual acuity improved from 0.58 +/- 0.21 to 0.76 +/- 0.21. Mean endothelial cell count was 1799 +/- 595 cells/mm2 preoperatively and 1784 +/- 589 cells/mm2 after 6 months; the difference was not significant. CONCLUSION: Curved lamellating keratotomy gives stable postoperative refractive results without significantly affecting endothelial cell count or visual acuity.

Aged↗
PubMed1999

One year clinical results of photoastigmatic refractive keratectomy for compound myopic astigmatism.

PURPOSE: To evaluate the efficacy, predictability, and safety of excimer laser photoastigmatic refractive keratectomy (PARK) to correct compound myopic astigmatism. SETTING: Departments of Ophthalmology, Robert Debré Hospital and Rothschild Foundation, Paris, France. METHODS: This retrospective study included 27 eyes with compound myopic astigmatism treated with a Nidek EC 5000 excimer laser. The refractive results were measured at 1 year, and the cylindrical component was analyzed by the Alpins method. Mean preoperative myopia was -4.50 diopters (D) (range -0.75 to -4.00 D) and mean preoperative cylinder, -1.64 D (range -0.75 to -4.00 D). RESULTS: At 1 year, the spherical equivalent was -0.47 D (range +1.00 to -3.00 D) and residual subjective astigmatism, -0.40 (range -0.25 to -1.50 D). Uncorrected visual acuity of 20/40 or better was obtained in 22 of the 27 eyes; 21 eyes were within +/- 1.0 D of emmetropia. Vector analysis showed a mean coefficient adjustment of 1.50 D +/- 0.53 (SD), a mean axis shift of 2.64 +/- 12.10 degrees, and a mean magnitude of error of 0.45 +/- 0.56 D. Haze was absent in 22 eyes and grade 1+ in 5 eyes. Five eyes gained 1 line of best corrected visual acuity and 3 lost 1 line. No patient lost more than 1 line. CONCLUSION: Excimer laser PARK successfully corrected low and moderate myopia combined with up to 4.0 D of astigmatism with a low mean angle of error. To increase the accuracy of toric ablation, specific algorithms for the cylinder component are needed.

Adolescent↗
PubMed2000

Excimer laser retreatment of residual myopia following photoastigmatic refractive keratectomy for compound myopic astigmatism.

PURPOSE: To prospectively evaluate the safety, efficacy, and visual performance of excimer laser enhancement following photoastigmatic refractive keratectomy (PARK) with the Summit Apex Plus. SETTING: Stanford University School of Medicine Eye Laser Clinic, Stanford, California, USA. METHODS: As part of a Food and Drug Administration clinical trial, 93 eyes of 56 patients with a mean spherical equivalent (SE) of -4.98 diopters (D) +/- 1.80 (SD) (range -1.75 to -8.50 D) had PARK for compound myopic astigmatism using the Summit Apex Plus excimer laser and a poly(methyl methacrylate) erodible mask. Seventeen eyes with a mean SE of -2.08 +/- 0.76 D required excimer laser refractive keratectomy for residual spherical myopia or compound myopic astigmatism. Patients were prospectively followed 1, 3, 6, 9, and 12+ months after the enhancement procedure. Primary outcome variables included uncorrected visual acuity (UCVA), refraction, vector analysis, best spectacle-corrected visual acuity (BSCVA) under standard ambient conditions (photopic, scotopic, and glare), corneal clarity, and contrast sensitivity function curve under photopic and scotopic conditions. RESULTS: At the last postoperative visit, the mean sphere had been corrected 82% to a residual of -0.29 +/- 1.23 D and mean SE had been corrected 65% to a residual of -0.74 +/- 1.27 D. Eighty-two percent of eyes were within +/-1.0 D of attempted correction. Eighty-eight percent had a UCVA of 20/40 or better. Vector analysis demonstrated a difference vector of within +/-1.0 D in 75% of eyes that had PARK retreatment. There was no significant loss in the contrast sensitivity curve. Late regression associated with corneal haze and loss of BSCVA occurred in 2 eyes (11.7%). CONCLUSIONS: Retreatment following PARK for compound myopic astigmatism results in effective reduction in residual spherical myopia and compound myopic astigmatism. An improvement in UCVA without loss of contrast sensitivity can be expected in most eyes. However, regression, corneal haze, and loss of BSCVA may occur. Further studies are indicated to predict risk factors for these complications.

Astigmatism↗
PubMed1992

Keratometry and post-operative astigmatism.

Total post-operative refractive astigmatism and keratometric corneal astigmatism were determined in patients following cataract surgery. By comparing the results of the two methods, the value of keratometry as a simple and quick procedure for identification of surgically induced astigmatic errors was established. It is proposed that this method should be used before final refraction in an attempt to increase clinic efficiency and reduce further appointments resulting from surgically induced astigmatism.

Astigmatism↗
PubMed2006

Risk factors for postoperative cylindrical prediction error after laser in situ keratomileusis for myopia and myopic astigmatism.

PURPOSE: To study the risk factors for the occurrence of cylindrical prediction error (PE) after laser in situkeratomileusis (LASIK) for myopia and myopic astigmatism. METHODS: The study was a nested case-control study. Five hundred eyes of 252 consecutive patients who underwent LASIK for myopia and myopic astigmatism on the Chiron Technolas 217C laser and completed 6 months of follow-up. There were 435 controls and 65 cases based on the postoperative refractive cylindrical PE. The probable risk factors studied included preoperative sphere and cylinder, keratometry, pachymetry, suction ring used, flap thickness, hinge centeration, optic zone, ablation depth, and intraoperative complications. RESULTS: By univariate analysis, the cylindrical PE was found to be associated with preoperative spherical equivalent higher than -6 D (chi(2)=10.83; P=0.001), preoperative sphere higher than -6 D (chi(2)=6.15, P=0.013), preoperative cylinder more than -0.75 D (chi(2)=6.61; P-value=0.010), and an optic zone less than 5.5 mm (chi(2)=19.3; P=0.001). Risk factors for postoperative astigmatism by stepwise multivariate logistic regression analysis were an optic zone of less than 5.5 mm with an odds ratio (OR) of 2.81 (95% confidence interval (CI)=1.62-4.86) and preoperative cylinder more than -0.75 D with an OR of 1.60 (95% CI=0.92-2.77). CONCLUSION: Postoperative astigmatism (as indicated by the cylindrical PE) is more likely to occur with an optic zone of less than 5.5 mm and a higher preoperative cylindrical error.

Adult↗
PubMedDate not supplied

[Visual acuity and astigmatism after eccentric penetrating keratoplasty - a retrospective study on 117 patients].

PURPOSE: The purpose of this study was to asses the functional results of eccentric homologous penetrating keratoplasty in respect of diagnosis as well as position and size of the corneal graft. PATIENTS AND METHODS: In this retrospective study, visual acuity and astigmatism of 117 cases of a round eccentric homologous penetrating keratoplasty in 91 eyes of 91 patients were analysed. The PK became necessary because of a corneal ulcer (104), 6 eyes with corneal scars and 7 eyes with ectatic corneal diseases. Using 84 postoperative slides the following parameters were quantified: graft diameter and transparency, distance of the geometric centre of the cornea from the central trephination margin (distance) as well as from the geometric centre of the graft (decentration). Seventeen grafts were classified as eccentric peripheral keratoplasty (mean diameter 5.0 +/- 1.7 mm) with the optical axis through the host cornea and 67 as eccentric central keratoplasty (7.0 +/- 1.3 mm) with the optical axis through the graft. RESULTS: The average follow-up period was 25 months. The astigmatism after 3/12/24 months was 6.7/6.3/5.5 D, but was irregular and not measurable in 74 %/52 %/49 %. The astigmatism increased with increasing decentration (24 months, p = 0.04). After 3/12/24 months, the VA in ulcers was 0.1/0.16/0.16, in scars 0.2/0.6/0.5 and in ectatic diseases 0.3/0.5/0.6. The position of graft and the visual acuity did not correlate significantly. After 24 months, larger the graft size was associated with better visual acuity. With increasing decentration the visual acuity decreased (p = 0.02) and was significantly lower (0.15) in the case of - 2.0 < distance < 2.0 mm than in the case of distance > 2.0 mm (0.4; p = 0.01). CONCLUSION: The diagnosis resulting in eccentric penetrating keratoplasty seems to have a major impact on the long-term functional prognosis of visual acuity. In addition, visual acuity is limited by high and often irregular astigmatism. Our results indicate that an increasing decentration of the graft is not invariably associated with decreasing visual acuity, provided the graft-host junction is not located in direct proximity of the optical axis.

Adolescent↗
PubMed1993

[Photorefractive keratectomy for correction of myopic astigmatism].

Nine eyes underwent superficial ablation with excimer laser for treatment of compound myopic astigmatism. In eight of the eyes, corneal cylinder was naturally-occurring, and in one eye the astigmatism had developed following retinal detachment surgery. All patients have been followed for 9 months. The pre- and postoperative cylinder was -2.7 +/- 0.4 diopters and -1.3 +/- 0.4 diopters, respectively, while the pre- and postoperative spherical equivalent was -4.7 +/- 0.4 diopters and -1.3 +/- 0.4 diopters, respectively. Uncorrected acuity improved from a preoperative mean of 20/300 to a postoperative mean of 20/40. Patients with a residual refractive error often demonstrated reasonably good unaided acuity. Toric ablations with the excimer laser can be performed at the same time as ablations for myopia, and appear to represent a promising strategy for correction of compound myopic astigmatism; the relative safety and efficacy of this procedure, and of combined radial and astigmatic keratotomy remain to be determined.

Astigmatism↗
PubMed1993

[Mathematical presentation of postoperative regular corneal astigmatism].

BACKGROUND: There are several contradictory approaches to describe a change in corneal astigmatism induced by operations. METHODS: Assuming a rotational ellipsoid for the outer surface of the cornea we derived formulas that represent the change in astigmatism. Also, the change of the corneal power in the axis of the intervention (e.g. operation) has been determined. RESULTS: The exact derivation yield formulas for the absolute value of the astigmatism change identical to those of Naylor and Jaffe but includes, in addition, algorithms for "with-the-rule" and "against-the-rule" components. The spherical change of the cornea is also obtained. The models of Cravy and Naeser are mathematically inconsistent and should be avoided. CONCLUSION: The presentation of the change in astigmatism should depend on the primary question. In many cases, the complicated non-linear vector calculation is not necessary since the actual changes in corneal shape may be demonstrated by simpler formulas. The results of these formulas are much easier to interpret.

Astigmatism↗
PubMed2002

Up-slanting palpebral fissures and oblique astigmatism associated with A-pattern strabismus and overdepression in adduction in spina bifida.

PURPOSE: To describe the spectrum of adnexal and ophthalmologic features in spina bifida. METHODS: A retrospective review of the medical records of 73 patients was conducted. Data concerning ocular motility, palpebral fissure orientation, presence and axis of astigmatism, visual acuity, amblyopia, and stereopsis were analyzed. RESULTS: Forty-three (59%) of the 73 patients had strabismus: 28 (65%) had esotropia, 12 (28%) had exotropia, and 3 (7%) had orthotropia in primary gaze and a significant A-pattern. Of the strabismic patients, 20 (47%) had an A-pattern, of which 13 (65%) demonstrated overdepression in adduction. Twenty-seven (84%) of the 32 patients with documented palpebral fissure orientation had exaggerated up-slanting palpebral fissures. Forty-nine (77%) of 64 patients exhibited astigmatism greater than 0.75 D in at least 1 eye, with a mean power of 1.6 D. The axis of cylinder was oblique in 76% of these patients. The astigmatic axis was consistently oriented perpendicular to the eyelid fissure orientation in the group of patients with up-slanting palpebral fissures, with the mean axis of cylinder being incyclorotated (OD axis, 77; OS axis, 108). Up-slanting palpebral fissures were associated with a 15-fold increased chance that the axis of cylinder would be incyclorotated (P =.07, chi-square test). An orbital computed tomographic (CT) scan of a spina bifida patient with A-pattern esotropia, overdepression in adduction, and up-slanting palpebral fissures demonstrated significant incyclorotated extraocular muscle pulley heterotopy. CONCLUSIONS: Exaggerated up-slanting palpebral fissures are a prominent feature in spina bifida. Up-slanting palpebral fissures in spina bifida patients are associated with incyclorotated oblique astigmatism, A-pattern strabismus, and overdepression in adduction. These associations might be related to an anomaly of orbital skeletal or extraocular muscle pulley development. Further prospective study is encouraged.

Adolescent↗
PubMed2003

Astigmatism induced by simultaneous recession of both horizontal rectus muscles.

PURPOSE: Changes have been reported in the refractive state of the eye after various types of strabismus surgery. This study investigates the effect of large simultaneous recession of both horizontal rectus muscles on the refractive state of the eye. METHODS: Twenty-six eyes (13 patients) were refracted 1 to 2 weeks before and 6 to 8 weeks after large horizontal rectus muscle recessions for the purpose of damping nystagmus. The preoperative refraction was mathematically subtracted from the postoperative refraction, and the induced refractive changes were averaged and statistically analyzed. The relation between the amount of recession and the induced astigmatism was also investigated. RESULTS: A statistically significant change in astigmatism in the with-the-rule direction was induced with this procedure (+ 0.70 diopter cylinder, axis 90.0 degrees, P <.0002). With the narrow range of amounts of recession performed, there was no demonstrable relation between the amount of recession and the amount of induced astigmatism. CONCLUSIONS: Recession of both horizontal rectus muscles, the same as has been reported for recession of one horizontal rectus muscle and recession-resection surgery on both horizontal rectus muscles, tends to induce a change in astigmatism in the with-the-rule direction.

Adolescent↗
PubMed2001

Surgically-induced astigmatism following single-site phacotrabeculectomy, phacotrabeculotomy and advanced non-penetrating phacotrabeculectomy.

We study surgically-induced astigmatism following three kinds of glaucoma surgeries combined with cataract surgery with 6 months of follow-up. The mean surgically-induced astigmatism at 6 months postoperatively was 1.92 +/- 1.87 diopters in phacotrabeculectomy (n = 45), 0.72 +/- 0.40 diopters in advanced non-penetrating phacotrabeculectomy (n = 40) and 0.76 +/- 0.47 diopters in phacotrabeculotomy (n = 49), which appeared to be stabilized by 3 months. Each group revealed a tendency of "with the wound" induced astigmatism. Phacotrabeculectomy could induce greater surgically-induced astigmatism than advanced non-penetrating phacotrabeculectomy and phacotrabeculotomy.

Astigmatism↗