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PubMed1998

How to calculate surgically induced astigmatism after cataract surgery?

Corneal astigmatism is a complex entity with a power and an axis. The purpose of this article is to give a summary of the most popular methods to calculate surgically induced astigmatism, and to discuss their differences. Various methods exist, but we will only discuss the most popular ones. The interested surgeon can use these methods on his patients to calculate and compare the surgically induced astigmatism of each of his surgical techniques. Doing so, he will be able to use the ideal technique in each individual case. Astigmatism-neutral as well as astigmatism-inducing techniques should be used. A correct pre- and postoperative keratometry is of course very important.

Astigmatism↗
PubMed1980

Astigmatism in visually immature child with strabismus.

Astigmatic refractive errors may develop late in the visual maturity period of strabismic children. Seventeen strabismic children who had surgery and ten strabismic children who did not have surgery are discussed; none had astigmatic error at the initial refraction. Significant astigmatism developed in both groups at age 4 years and two years after the initial refraction. The ophthalmologist should be aware that late-developing astigmatism can cause a recurrence or deterioration of strabismus. The best response is serial refractions and appropriate correction of all strabismus patients during the visual maturity period.

Aging↗
PubMed1986

Dynamic shifts in corneal topography during the modified Ruiz procedure for astigmatism.

We utilized ten eye bank eyes to evaluate and quantitate the immediate corneal topographic shifts that occur after each stage of a modified Ruiz procedure for astigmatism. Computer digitization of photokeratoscope (Corneascope) photographs revealed that the initial two central paired tangential incisions induced an average of 5.10 diopters (D) of central astigmatism by flattening the meridian perpendicular to the incisions and by steepening the meridian 90 degrees away. Additional tangential incisions did not significantly alter the topography after placement of the first two central incisions. Addition of corridor incisions produced an additional 5.25 D of induced astigmatism by further extensive flattening of the incised meridian. The completed procedure produced an average of 11.03 D of astigmatic shift, but with a wide range of effect (7.15 to 12.96 D). With modification, the Ruiz procedure is a powerful keratorefractive surgical technique.

Astigmatism↗
PubMed1987

Astigmatism associated with adnexal masses in infancy.

High degrees of astigmatism are common in infants with hemangiomas but have not been well documented with other adnexal masses. We reviewed records of 65 patients (69 eyes) with chalazions, epibulbar or orbital dermoids, hemangiomas, and dacryoceles. Astigmatism greater than +1.25 diopters (as high as +5.50 diopters) was most commonly associated with dacryoceles (eight of 12 eyes) and with hemangiomas (14 of 17 eyes). Plus cylinder axes were consistently oriented toward the lesion, and astigmatism tended to resolve with resolution of the lesions. Only one of the 17 eyes with dermoids and two of the 23 eyes with chalazions had astigmatism. Anisometropic amblyopia has been a prominent concern in the treatment of infants with hemangiomas. Patients with dacryoceles may be at similar risk. Repeated cycloplegic refractions are important in determining appropriate treatment of adnexal masses.

Amblyopia↗
PubMed1991

Prospective corneal topographic analysis in surgery for postkeratoplasty astigmatism.

Computer-assisted photokeratoscopy was used to evaluate the topographic characteristics of corneas preoperatively and postoperatively in seven patients who underwent surgery for correction of postkeratoplasty astigmatism. The steep hemimeridians were typically separated by an angle other than 180 degrees (mean, 162.5 degrees) and the flat hemimeridians were often not orthogonal to the steep hemimeridians. Asymmetry of power (1.5 or more diopters) between these two major hemimeridians was also observed in three patients. Relaxing incisions were placed in the two steep hemimeridians and compression sutures were placed in the flat hemimeridians. The mean percent of reduction of astigmatism (vector-corrected) was 81.1%. The amount of keratometric astigmatism, and the degree of asymmetry of the hemimeridians were not correlated with the percent of reduction of astigmatism after placement of the relaxing and compression sutures. Computer-assisted topographic analysis may prove useful in planning transverse keratotomies centered on the steep hemimeridians and in placement of compression sutures in flat hemimeridians.

Adult↗
PubMed1993

Comparison of excimer laser treatment of astigmatism and myopia. The Excimer Laser and Research Group.

OBJECTIVE: To assess the safety and efficacy of excimer laser treatment of myopic astigmatism and to compare this with the excimer laser treatment of myopia. DESIGN: A prospective, open study of consecutive patients having excimer laser treatment of myopic astigmatism or myopia. SETTINGS: Patients were recruited from 18 private ophthalmic practices. PATIENTS: Fifty-four eyes received treatment for astigmatism and 66 eyes for myopia. One patient was lost to follow-up, and another underwent an ineffective ablation. INTERVENTIONS: A VISX Twenty/Twenty excimer laser was used to perform either photoastigmatic refractive keratectomy or photorefractive keratectomy. MAIN OUTCOME MEASURES: Refraction and visual acuity with and without correction were assessed preoperatively and postoperatively. RESULTS: At 6 months, 17 (85%) of the 20 patients receiving photoastigmatic refractive keratectomy were within 1 diopter of plano refraction, and 19 (95%) of 20 had uncorrected visual acuity of 6/12 (20/40) or better. For patients receiving photorefractive keratectomy, these figures were 28 (88%) of 32 patients and 28 (88%) of 32 patients, respectively. CONCLUSIONS: Excimer laser surgery offers an effective option in the treatment of myopic astigmatism.

Adult↗
PubMed1977

Astigmatism of the mammalian cornea: evolutionary and perceptive significance.

Astigmatism enables spatial, linear and directional discrimination. These faculties are demonstrated by astigmatic photographic experiments. Comparative anatomic deductions lead to the assumption that the eyes of early mammals were astigmatic. Thereby these animals, lacking binocularity and accommodation, could achieve visual spatial information. This assumption is supported by the fact that features of astigmatic refraction, specially straight linearity, have been adopted by various intra-ocular structures, and by the neuronal structuralisation of receptive fields in the visual cortex of mammals.

Animals↗
PubMed1992

Astigmatism following cataract surgery: comparison of a scleral and a corneal incision in a mixed group of patients with and without glaucoma.

We retrospectively analysed the course of postoperative corneal astigmatism and corrected visual acuity after extracapsular cataract extraction and posterior chamber lens implantation with either a corneal or a scleral incision in 170 eyes of 155 patients with and without glaucoma. A continuous 10/0 nylon shoelace suture was used for wound closure in two groups. In a third group, corneal wound closure was performed with a shorter shoelace suture in combination with two vicryl wing sutures at 11 and 1 o'clock. Although early postoperative mean astigmatism in eyes operated through a corneal incision was high (range 2.92-6.67 diopters at 1 month postoperatively) and significantly different when compared to eyes operated through a scleral incision (1.96 diopters), final mean astigmatism did not differ significantly between those two groups. Moreover, in 27% of eyes operated through a corneal incision, mean astigmatism at 2 months postoperatively was not significantly different from the scleral group and suture removal was not necessary. There was no statistically significant difference in corrected visual acuity over the entire study period between groups. Since safety and functional results of the corneal incision were not different from the scleral incision, we prefer a corneal incision in cataract surgery because of its surgical advantages, especially in patients with cataract and coexisting glaucoma.

Astigmatism↗
PubMed1994

Astigmatism after penetrating keratoplasty. Role of the suture technique.

The Authors retrospectively evaluated the evolution of corneal astigmatism 6, 12 and 24 months after penetrating keratoplasty in 75 eyes by comparing 2 suture techniques: running suture (RS) in 14 cases vs interrupted suture (IS) in 61 cases. The mean keratometric astigmatism in patients with RS was 7.75 +/- 3.10 D at 6 months, 5.89 +/- 2.50 D at 12 months and 3.90 +/- 1.70 D at 24 months. In patients with IS these values were 4.82 +/- 4.00 D at 6 months, 2.81 +/- 1.60 D at 12 months and 2.77 +/- 1.34 D at 24 months. A significant lower astigmatism (P < 0.05) was noted after using IS at 6 and 12 months. At 24 months, however, this difference was no longer statistically significant (P > 0.3). The IS suture allowed a better control of the post-surgical astigmatism, and a more rapid recovery of the visual acuity.

Adolescent↗
PubMed1994

Normalisation of asymmetric astigmatism after intralesional steroid injection for upper eye lid hemangioma in childhood.

Infantile hemangiomas affect about 5% (3%-8%) of the population, showing a predilection for the face. After a phase of rapid enlargement between the 3rd and the 9th month of life, 70% regress by the age of six after a period of stability. 43%-60% of the children with eye lid hemangiomas develop strabismic, anisometropic, or deprivation amblyopia. Previous studies found the majority of cases resulting from anisometropia (especially asymmetric astigmatism) rather than strabism or occlusion of the visual axis. Several methods of treatment--surgical excision, irradiation, sclerosing agents, systemic steroids, ligation, cryotherapy--have been used but all with a risk of local or systemic complications. Local injections of steroids are a simple method of therapy with a high rate of resolution of hemangiomas, but still with a high degree of bad visual output because of persistent astigmatism. In four children with asymmetric astigmatism (axis of astigmatism towards the hemangioma) in which the injection was given at the beginning of the phase of enlargement, amblyopia could be avoided by preventing corneal steepening from becoming permanent.

Anti-Inflammatory Agents↗
PubMed1981

Myopic astigmatism a substitute for accommodation in pseudophakia.

The power of an intraocular lens can be calculated before surgery to make the eye emmetropic or ametropic. The physiological mechanism of accommodation however, cannot be restored with an inelastic lens. An increased depth of focus in the implanted eye can be predicted through optical principles alone, if the postoperative ametropia of the implanted eye is a simple myopic astigmatism. This increased depth of focus without accommodation was tested in artificial ametropia and found to be used in nature by the seal. To increase the precision of intraocular lens calculation the average change in corneal power induced at surgery is used to predict the postoperative corneal power. By controlled suture release in the postoperative phase, the amount of induced corneal astigmatism is adjusted to obtain a simple myopic astigmatism. Patients with an intraocular lens and a simple myopic astigmatism as a residual ametropia, are spectacle independent most of the time. They need their glasses only for driving or prolonged reading. The methods used to calculate the postoperative cornea, the postoperative anterior chamber depth and the intraocular lens are described with the corresponding calculator programs for the HP 41C calculator. Clinical results and measurements of the depth of focus are shown in a series of 50 successive implant cases.

Accommodation, Ocular↗
PubMed2006

[Optical quality of the cornea following incisional correction of astigmatism].

BACKGROUND: Unilateral lamellar keratotomy (LKT) and curved dual lamellar keratotomy (BLK) were compared to evaluate the influence of incisional correction of astigmatism on the optical quality of the cornea. PATIENTS AND METHODS: Forty-six patients with a preoperative astigmatism greater than 1.5 D were studied. LKT was performed on 30 eyes during cataract surgery and 20 eyes were treated with a BLK. Preoperatively and 4 weeks after surgery the corneal topographical data were analyzed with ray tracing in a 3-mm optical zone. The potential visual acuity (PVA) and the optical distortion (OD), which is represented by the width of the point spread in the optical center, were calculated as parameters for the optical quality. RESULTS: The mean surgically induced astigmatism was 2.6+/-1.5 D for the LKT group and 3.5+/-1.4 D for the BLK group. The PVA decreased significantly in the LKT group from 1.2+/-0.2 to 1.0+/-0.3 (p=0.008), whereas in the BLK group the PVA remained unchanged (p=0.916). The OD increased from 6.6+/-0.9 microm to 7.9+/-2.0 microm (p=0.007) in the LKT group. In the BLK group the values were stable (p=0.843). CONCLUSIONS: The optical quality of the cornea decreased after unilateral keratotomy in the early postoperative period. Thus, optical quality values should also be considered in incisional correction of astigmatism.

Adult↗
PubMed1999

[Sutureless corneal cataract surgery. Limbal release incisions for correcting astigmatism].

BACKGROUND: To prevent surgically induced astigmatism following clear corneal cataract surgery. PATIENTS AND METHODS: Limbal relaxing incisions of 6 or 8 mm length respectively and 0.5 mm depth were performed in 52 patients with spheric cornea or astigmatism with the rule of 0.8 +/- 0.3 dpt after temporal corneal cataract incision. The same amount of patients, operated on with the same surgical procedure except keratotomies, served as control. RESULTS: After 6 months the with-the-wound-change (WTW) in the LRI axis using the Hollady method was -0.08 +/- 0.5 dpt in the spheric cases with limbal keratotomy and +0.5 +/- 0.7 dpt in the control cases. The patients with preoperative astigmatism with the rule showed a WTW in the LRI axis of -0.09 +/- 0.5 dpt in the keratotomy cases and +0.39 +/- 0.7 dpt in the corresponding control patients. CONCLUSION: Limbal relaxing incision is a reliable and safe procedure to reduce postoperative astigmatism after cataract surgery.

Astigmatism↗
PubMed1999

[Corneal astigmatism as a special complication after lid-loading in patients with lagophthalmos].

UNLABELLED: Lid-loading with precious metals, described by Illig in 1958, has become increasingly important. because of its good functional and cosmetic results this method is superior to tarsorrhaphy. Furthermore, lid-loading can be combined with additional surgical techniques to achieve more dynamic lid-closure. In a prospective study we examined the results after lid-loading and discuss postoperative changes of the cornea. PATIENTS AND METHODS: Between May 1994 and June 1998, 36 patients with peripheral facial paresis and lagophthalmos were treated with a pretarsally fixed upper-lid implant. We used 99.99% gold for the implants with a weight of 1.5 g on average. RESULTS: In all cases we obtained sufficient postoperative lid closure which resulted in a statistically significant reduction in lagophthalmos and improved keratopathy. Postoperative complications were: pseudoptosis, remaining lagophthalmos, bulge, extrusion, migration and corneal astigmatism. Depending on the implant pressure, an astigmatism of 1-2 D developed in the vertical meridian. In all cases the initial visual acuity was reached by an ordination of cylindrical glasses. CONCLUSIONS: So far, corneal astigmatism as a complication after lid-loading has not received much attention in the literature. In our opinion, the development of astigmatism is caused by implants that are too heavy, an incorrect implant radius and individual cofactors (consistency of lid and cornea). There has been no need for an explantation in any case.

Adult↗
PubMed2000

[Correction of myopia and astigmatism using topography-assisted laser in situ keratomileusis (TopoLink LASIK)].

PATIENTS AND METHODS: We treated 114 patients (eyes) with myopia of -1 to 6 D and astigmatism of 0 to -4 D (group 1), and 89 patients (eyes) with myopia of -6.1 to -12 D and astigmatism of 0 to -4 D (group 2). All treatments were calculated on the basis of corneal topography measured with the Orbscan II system. The Keracor 217 excimer laser and the Hansatome microkeratome were used. RESULTS: At 3 months, 51 patients in the low myopia group and 40 patients in the high myopia group were available for examination. In the low (high) myopia group, 96.1% (75.0%) were within +/- 0.50 D of emmetropia, and uncorrected visual acuity was 20/20 or better in 82.4% (62.5%), 20/25 or better in 98.0% (70.0%), and 20/40 or better in 100% (95.0%). A loss of two or more lines of spectacle-corrected visual acuity occurred in 3.9% of the low and 5.0% of the high myopia group. In low myopia, spectacle-corrected visual acuity was 20/12.5 or better in 5.9% preoperatively and in 13.7% at three months and 20/15 or better in 37.3% and 47.1%, respectively (P = 0.0002 and P = 0.01). CONCLUSIONS: LASIK based on corneal topography showed very high efficacy in low and moderate myopia with astigmatism, and maximal visual acuity could even be improved in some cases. There was somewhat less precision in high myopia with astigmatism.

Astigmatism↗
PubMed2004

Implantation of a toric phakic intraocular lens to correct high corneal astigmatism in a patient with bilateral marginal corneal degeneration.

We present a patient with marginal corneal degeneration and corneal astigmatism of more than 10.0 diopters (D). A toric phakic intraocular lens (IOL) of 7.0 D cylindrical power was implanted in both eyes to correct the high astigmatism. An uncorrected visual acuity of 20/40 was achieved in both eyes, and the best corrected visual acuity improved by 4 Snellen lines to 20/20 in both eyes. Refraction and visual acuity remained stable at 1.5 years postoperatively. Implantation of a toric phakic IOL can be an option to correct high corneal astigmatism even when the full corneal astigmatism cannot be treated.

Astigmatism↗
PubMed2004

Bitoric laser in situ keratomileusis for astigmatism.

PURPOSE: To evaluate the efficacy, predictability, and safety of bitoric laser in situ keratomileusis (LASIK) for the correction of mixed astigmatism. SETTING: Instituto Oftalmológico de Alicante, Alicante, Spain. METHODS: This prospective study included 28 eyes of 21 patients with mixed astigmatism who had bitoric LASIK using the Hansatome microkeratome (Bausch & Lomb Surgical) and the Chiron Technolas 217 excimer laser (Bausch & Lomb Surgical). The main outcome measures were uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), defocus equivalent, blur strength, and refraction. RESULTS: Six months after bitoric LASIK, the mean UCVA was 0.70 +/- 0.23 (SD). The percentage of eyes with a UCVA of 20/40 or better was 78.6% and of 20/20, 21.4%. There was a statistically significant increase in the mean BCVA from 0.71 +/- 0.19 before surgery to 0.83 +/- 0.15 at 6 months (P =.0004). Three eyes (10.7%) lost 1 line of BCVA; 19 eyes (67.9%) gained 1 or more lines. The mean preoperative astigmatism of -4.04 +/- 1.13 diopters (D) was reduced to -0.67 +/- 0.79 D after surgery. The defocus equivalent was less than 1.00 D in 75.0% of eyes and less than 0.50 D in 64.3%. Vector analysis showed that the mean achieved correction was 97.4% of the intended correction. CONCLUSIONS: Bitoric LASIK was a safe, effective, and predictable procedure in the treatment of mixed astigmatism. It is a means to improving BCVA in a significant percentage of patients.

Adult↗
PubMed2004

Analysis of the efficacy, predictability, and safety of LASEK for myopia and myopic astigmatism using the Technolas 217 excimer laser.

PURPOSE: To evaluate the efficacy, predictability, and safety of laser-assisted subepithelial keratectomy (LASEK) for the treatment of myopia and myopic astigmatism. SETTING: Stanford University Eye Laser Center, Stanford, California, USA. METHODS: This retrospective analysis comprised 102 eyes that had LASEK for myopia using the Bausch & Lomb Technolas 217 excimer laser. Primary outcome variables including uncorrected visual acuity (UCVA), best spectacle- corrected visual acuity (BSCVA), manifest refraction, and complications were evaluated at 3, 6, and 12 months. Vector analysis was performed on eyes that received astigmatic correction. RESULTS: The mean spherical equivalent was -7.03 diopters (D) +/- 2.61 (SD) preoperatively, +0.19 +/- 0.64 D at 3 months, +0.23 +/- 0.82 D at 6 months, and +0.03 +/- 0.63 D at 12 months (P<.001). At 3, 6, and 12 months, the UCVA was 20/20 or better in 66%, 67%, and 83% of eyes, respectively, and 20/40 or better in 98%, 99%, and 100%; 74%, 70%, and 83%, respectively, were within +/-0.5 D of emmetropia, and 89%, 86%, and 97%, respectively, were within +/-1.0 D. No eye lost more than 2 lines of BSCVA. At 3, 6, and 12 months, 10.0%, 8.7%, and 0% of eyes, respectively, had trace corneal haze. Vector analysis found a success rate of approximately 78% to 80% in achieving the astigmatic surgical correction at the 3 postoperative visits. CONCLUSIONS: Laser-assisted subepithelial keratectomy was an effective, predictable, and safe procedure for the treatment of myopia and myopic astigmatism. Further studies are needed to determine the role of LASEK in the refractive surgery spectrum.

Adult↗