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PubMed2000

Excimer laser photorefractive keratectomy and laser in situ keratomileusis for myopia and astigmatism.

The efficacy, predictability, safety, and short-term stability of excimer laser photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) for treatment of myopia and astigmatism were determined. The preoperative myopia ranged from -1.50 to -15.75 D and the astigmatism was less than 4.0 D. Of the 147 eyes, 73 and 74 underwent PRK and LASIK, respectively. Mean preoperative spherical equivalent refraction (SE) was -3.72 +/- 1.69 D in the PRK group and -7.66 +/- 2.30 D in the LASIK group. Mean postoperative SE at the last examination (3 to 6 months) was -0.13 +/- 0.82 D and -0.38 +/- 1.19 D in the PRK and LASIK groups, respectively. Eighty six percent in the PRK group and 77 per cent in the LASIK group achieved a SE within +/- 1.0 D and the refractions were stable between 1 month and 3-6 months. Uncorrected visual acuity of 20/40 or better was noted in 91 per cent in the PRK group and 97 per cent in the LASIK group. No eyes lost one or more lines of best spectacle-corrected visual acuity in both groups. PRK and LASIK appear to be effective, safe, predictable, and short-term stable in treating myopia and astigmatism. Longer follow-up studies will help evaluate the long-term stability of the procedure and possibility of later complications.

Adult↗

PubMed2001

Keratometric astigmatism after cataract surgery using small self-sealing scleral incision.

BACKGROUND: To evaluate the corneal refractive changes after a small self-sealing scleral wound. METHODS: A 4 mm self-sealing scleral tunnel incision and implantation of a foldable intraocular lens were adopted during phacoemulsification. A retrospective review of 48 consecutive isolated eyes in 48 patients was performed to assess the postoperative corneal refractive change. Keratometric readings were recorded for 3 months following surgery. RESULTS: At one week postoperatively there was a -0.29 +/- 1.02 (standard deviation) change of Naeser's polar value (against-the-rule shift) in the cylinder keratometry. The cylinder had with-the-rule shift and recovered to the preoperative state at one month postoperatively. The change of Naeser's polar value at the third postoperative month was 0.05 +/- 0.80 (with-the-rule shift) compared with the preoperative polar value. The change of astigmatism at the third postoperative month was -0.38 +/- 0.74 (Diopters) using simple subtraction and -1.01 +/- 0.58 (Diopters) using the Jaffe vector analysis. The axis of astigmatism exhibited a mild against-the-wound shift at 1 week and a gradual with-the-wound shift afterwards. CONCLUSION: The low induced astigmatism, early recovery of corneal curvature and no direct damage to the cornea support the concept and justify the use of a small self-sealing scleral tunnel incision during cataract surgery.

Adult↗

PubMed2002

Results of combined myopic astigmatic LASIK treatment and retreatments.

PURPOSE: A study of combined LASIK treatment and retreatment results for both myopia and myopic-astigmatic correction. METHODS: Three hundred fifty-three consecutive eyes underwent LASIK surgery using the VISX Star excimer laser. Preoperative mean sphere was -6.37 +/- 2.93 D with mean cylinder of +1.01 +/- 0.9 D. The initial refraction of the 40 patients needing retreatment was -7.42 +/- 2.49 D with a mean cylinder of +1.0 +/- 0.61 D. RESULTS: Data were analyzed in the following way: Group I: Primary treatment (all); Group II: Group I excluding retreatment; Group III: Retreatment; and Group IV: Groups II and III combined. Postoperative uncorrected visual acuity (UCVA) data at 1, 3, and 6 months were: Group I: 20/40 or better 90.5%, 87.2%, and 89.5%; 20/20 or better 52.0%, 48.9% and 59.6%; Group II: 20/40 or better 95.0%, 95.2%, and 95.7%: 20/20 or better 52.0%, 62.6% and 63.8%; Group III: 20/40 or better 97.5%, 97.5%, and 100%; 20/20 or better 80%, 76% and 77%; and Group IV. 20/40 or better 97%; 20/20 or better 63% at six months. Pretreatment degree-of-myopia comparison in Group I was (0-3 D) 90% 20/20 UCVA after 6 months; (-6 - -9 D) 60% 20/20; and (> -12 D) 44% 20/20. Complications included 1 free flap, 1 partial flap, and 4 epithelial ingrowths. CONCLUSIONS: These results demonstrate myopic-astigmatic LASIK treatment to be safe, effective, and predictable in correcting myopia and associated astigmatisms. For patients requiring retreatment, results are excellent. Results should be reviewed after all treatments have been completed. The success rate for LASIK surgery seems to be directly related to the degree of myopia. As myopia increases, the chance of achieving 20/20 vision decreases.

Adult↗

PubMedDate not supplied

[Comparative results of sub-flap intrastromal photokeratectomy in correcting astigmatism by bitoric and monotoric keratoablation].

The paper discusses the results of 28 laser operations carried out by bitoric nomograms and 18 operations carried out by monotoric nomograms for correction of high astigmatism (3 and more diopters) by laser in situ keratomileusis (LASIK). The patients' ages varied from 21 to 38 years. Eximer photokeratectomy was carried on a EC 5000 Nidek laser, lamellar section of the cornea was made with a Hansatome microkeratome. Bitoric keratoablation was carried out by an original method. Clinical refraction, visual acuity, and incidence of reoparations were evaluated in both groups 6 months postoperation. Differences in refraction and visual acuity were negligible. The incidence of reoparations in bitoric keratoablation was 25%, in monotic one 44%. Visual acuity with correction was higher after bitoric keratoablation of astigmatism. Hence, bitoric keratoablation is preferable for correction of high astigmatism by LASIK.

Adult↗

PubMed2003

[Lasik correction of compound myopic astigmatism with positive versus negative cylinder ablations].

PURPOSE: To compare the predictability, efficacy, and safety of two methods of Lasik correction of compound myopic astigmatism: positive cylinder ablation versus negative cylinder ablation. METHODS: Twenty nine eyes of 19 patients were retrospectively analyzed. They had undergone Hansatome or ALK-e flap keratectomy, and a Technolas Keracor 217c laser ablation. Group 1 (14 eyes) was corrected with the positive cylinder program, group 2 (15 eyes) with the negative cylinder program. Spherical equivalent (SE), cylinder, vector analysis, and best corrected and uncorrected visual acuities (BCVA, UVA) were compared in the two groups. Minimum follow-up was 6 months. RESULTS: The preoperative mean SEs for groups 1 and 2 were, respectively, - 7.09+/-3.36 D and - 8.05+/-2.27 D (NS). Mean cylinders were 1.73+/-0.88 (group 1) and +/-0.74 (group 2) D. Visual acuities were not statistically different in the two groups. Postoperative mean SEs were, respectively, - 0.57+/-1.58 D and - 0.68+/-0.88 D. Mean cylinder was, respectively, 0.57 +/- 0.54 D and 0.7 +/- 0.46 D in groups 1 and 2. Astigmatism induced by surgery, calculated by vector analyses was, respectively, 1.36 +/- 0.66 D and 1.54 +/- 0.56 D. Percentages of UVA above 20/25 were, respectively, 50% and 35%. None of those differences was statistically significant. One eye lost one line of BCVA. CONCLUSION: The positive cylinder ablation method makes a larger optical zone of ablation possible with the same central deepness of ablation. We found that the predictability, efficacy, and safety of this technique compares well with the negative cylinder ablation in compound myopic astigmatism.

Astigmatism↗

PubMed2003

[Reasons of postoperative astigmatism].

At present, cataract extraction offers great improvement for uncorrected and best corrected visual acuity and rapid postoperative rehabilitation. Cataract surgery is now treated as refractive surgery. Postoperative astigmatism has remained the only obstacle to the achievement of good, uncorrected visual acuity after cataract surgery. Postoperative astigmatism is a very complex clinical problem. The main influence on its appearance has preoperative astigmatism as well as shape and length of anterior chamber opening, suturing technique and wound healing.

Astigmatism↗

PubMed1992

[Early postoperative corneal astigmatism. Comparison of various suture techniques].

We compared two suture techniques after phacoemulsification and implantation of a standard PMMA posterior chamber lens with a 7 mm intrascleral lamellar incision: the cross-stitch (double running) suture closure and the one-stitch technique. Two series with 100 patients each were examined. In the early postoperative period the astigmatism induced was 1.9 +/- 1.4 D in the cross-stitch group and 1.5 +/- 1.0 in the one-stitch group (P = 0.01). In the latter group, 20% more of the patients were found to have a moderate amount of astigmatism. Four weeks after surgery, however, there were no differences between the two groups. The induced astigmatism in both groups was 1.0 D.

Astigmatism↗

PubMedDate not supplied

[Corneal astigmatism after cataract extraction: differences between the continuous x-shaped suture and the single knot stitch].

The author examined the postoperative astigmatism in 70 eyes of patients subjected to an extracapsular extraction with implantation of a posterior chamber lens in postoperative periods of 14 days, 3, 6 and 12 months. Compared were 2 groups of eyes with different methods of wound closure: by single knot stitches and by a continuous x-shaped suture. The degree of astigmatism showed to be higher in the 6 first postoperative months in the group of single knot stitches but after 6 months it became levelled with the degree of astigmatism detected in the group of continuous x-shaped suture.

Adult↗

PubMed1992

The use of the SoftPerm lens for the correction of irregular astigmatism.

We evaluated the performance of the SoftPerm combined rigid gas permeable (RGP) and hydrogel lens for the visual correction of 49 eyes (30 patients) with irregular astigmatism. Follow-up was up to 15 months. An attempt was also made to compare the SoftPerm lens to its predecessor, the Saturn II lens. The most common etiology for irregular astigmatism was keratoconus. Others etiologies were penetrating keratoplasty and refractive surgery. Visual acuity improved significantly. Only two eyes were best corrected to 20/20 before fitting whereas, 13 eyes saw 20/20 after fitting. The rate of lens replacement was 0.22 lenses per eye per month. A variety of complications occurred, including corneal staining, abrasions, and edema. Complications also reflected the relative difficulty of handling of the lens, yet no vision threatening complications occurred. Overall, the SoftPerm lens is a vast improvement over the Saturn II and is a reasonable means of correction of irregular astigmatism.

Adolescent↗

PubMed2004

[Efficacy of rigid gas permeable contact lens for the correction of mixed astigmatism].

PURPOSE: To evaluate the efficacy of rigid gas permeable contact lens (RGPCL) for the correction of mixed astigmatism. METHODS: Patients with mixed astigmatism by mydriasis refraction were selected as subjects. Routine eye check was performed to exclude contraindication of contact lens. Investigation included visual acuity, keratometry and corneal topography. Average keratometry value was chose as base curve of the first trial lens. Final base curve, diameter, material and edge of lens were prescribed according to the centralized position, movement and fluorescence pattern of trial lens. After over refraction, final refractive power of lens was prescribed. Corrective visual acuity with spectacle and rigid gas permeable contact lens were compared in 24 patients (31 eyes). RESULTS: Corrective visual acuity of patients with RGPCL was much better than those with spectacle. CONCLUSIONS: RGPCL is safe and effective to correct mixed astigmatism.

Adolescent↗

PubMedDate not supplied

Computer simulation of arcuate keratotomy for astigmatism.

BACKGROUND: The development of refractive corneal surgery involves numerous attempts to isolate the effect of individual factors on surgical outcome. Computer simulation of refractive keratotomy allows the surgeon to alter variables of the technique and to isolate the effect of specific factors independent of other factors, something that cannot easily be done in any of the currently available experimental models. METHODS: We used the finite element numerical method to construct a mathematical model of the eye. The model analyzed stress-strain relationships in the normal corneoscleral shell and after astigmatic surgery. The model made the following assumptions: an axisymmetric eye, an idealized aspheric anterior corneal surface, transversal isotropy of the cornea, nonlinear strain tensor for large displacements, and near incompressibility of the corneoscleral shell. The eye was assumed to be fixed at the level of the optic nerve. The model described the acute elastic response of the eye to corneal surgery. RESULTS: We analyzed the effect of paired transverse arcuate corneal incisions for the correction of astigmatism. We evaluated the following incision variables and their effect on change in curvature of the incised and unincised meridians: length (longer, more steepening of unincised meridian), distance from the center of the cornea (farther, less flattening of incised meridian), depth (deeper, more effect), and the initial amount of astigmatism (small effect). CONCLUSIONS: Our finite element computer model gives reasonably accurate information about the relative effects of different surgical variables, and demonstrates the feasibility of using nonlinear, anisotropic assumptions in the construction of such a computer model. Comparison of these computer-generated results to clinically achieved results may help refine the computer model.

Animals↗

PubMed2005

[Vector analysis of surgically induced astigmatism after combined operation of phacoemulsification, intraocular lens implantation and pars plana vitrectomy].

BACKGROUND: To evaluate the changes in corneal shape after phacoemulsification, PC IOL implantation and pars plana vitrectomy. MATERIAL AND METHODS: This study comprised 25 eyes of 25 patients who received phacoemulsification, 5.5 mm PMMA IOL implantation through 6 mm clear cornea incision with one single suture, and pars plana vitrectomy in one step - group A. To unique and compare the differences in surgical induced astigmatism (SIA) between combined procedures and two steps procedures, 2 control groups in one step surgery (only phacoemulsification with PCIOL--group B or only pars plana vitrectomy--group C) with the same shape and location of incision in cataract surgery and sclerotomy sites were analyzed. RESULTS: The highest value of SIA was in group A which was not statistic significant different than group B (p = 0.97). In-group C, SIA was the lowest, and there was also not significant difference between groups A (p = 0.063). The differences in SIA between group B and C were statistic irrelevant too. (P = 0.09) Shifts in axis to with the rule component were noted in 43.9 % of cases in-group A, 40.79% in-group B, and 58.96% in-group C. The highest shift in axis to against the rule meridian was observed in-group B (tab. 2) and in direction with the rule in-group C. CONCLUSIONS: No statistical significance was observed in the amounts of the induced astigmatism and refractive cylinder among the group of combined phacoemulsification, IOL implantation and pars plana vitrectomy. However, optical rehabilitation can be delayed by a postoperative astigmatism.

Aged↗

PubMed2006

Corneal astigmatic effects of conventional recession vs suspension recession ("hang-back") strabismus surgery: a pilot study.

INTRODUCTION: Changes in refractive error after strabismus surgery occur secondary to changes in corneal curvature. The change in refractive error is usually transient but may lead to a temporary decrease in vision. We compared the change in corneal curvature following strabismus surgery in eyes utilizing a suspension (so-called "hang-back") recession technique to eyes undergoing conventional recession surgery. METHODS: Sixteen patients undergoing bilateral medial or lateral rectus recessions were prospectively entered into the study. One eye was randomly selected to undergo conventional strabismus surgery and the other eye underwent strabismus surgery using the suspension technique. Keratometry measurements were taken in the operating room immediately prior to and immediately after surgery. The change in corneal curvature was calculated and analyzed for each technique. RESULTS: The mean change in corneal curvature was -0.06 diopters (D) for the suspension group and +0.18 D for the conventional group, confirming prior reports. However, all eyes undergoing suspension surgery had a change within 1 D whereas only 75% of those eyes undergoing conventional surgery fell within the same range. Overall there was twice the variation in the degree of astigmatism in the conventional group when compared with the suspension group. CONCLUSIONS: No eye undergoing suspension surgery experienced a change in corneal curvature greater than 1 D while 25% of those undergoing conventional surgery did. Therefore, possible benefits to the suspension recession technique might include less overall variability of astigmatism change and decreased amounts of induced astigmatism. Patients undergoing strabismus surgery using a suspension technique may be less likely to notice a change in their vision in the immediate postoperative period.

Astigmatism↗

PubMed1991

Maintaining nearly physiologic intraocular pressure levels prior to tying the sutures during cataract surgery reduces surgically-induced astigmatism.

We sought to determine whether maintaining nearly physiologic levels of intraocular pressure (IOP) before the final tying of sutures in cataract surgery can help minimize postoperative-induced astigmatism. We compared the postoperative astigmatic decay curves of two similar groups of 18 patients who had undergone cataract surgery, in one of which IOP had been maintained at 17 mm Hg prior to the final tying of sutures, and in the other of which the eyes were hypotonus (3 mm Hg) at this point. Initial with-the-rule cylinder change was significantly less and astigmatic decay occurred earlier in the former group.

Aged↗

PubMed1991

Suture adjustment for postkeratoplasty astigmatism.

Excessive corneal astigmatism following penetrating keratoplasty is a frequent problem. A technique that adjusts a single running 10-0 nylon suture after keratoplasty was used in this series of patients. The procedure requires a keratometer, slitlamp, topical anesthesia, and tying forceps. In 52 eyes, with an average of 10.0 diopters of keratometric astigmatism, we adjusted the suture to flatten the steep corneal axis. We were able to reduce astigmatism an average of 7.2 diopters and this remained stable three months post wound revision.

Adult↗

PubMedDate not supplied

Analysis of the effects of astigmatism and misalignment on corneal surface reconstruction from photokeratoscopic data.

This article presents a general method of error analysis for reconstruction algorithms employed by corneal topography systems and applies this method to assess the accuracy of the Wang reconstruction algorithms. Using mathematical surface reconstructions, the method detects artifacts introduced in topographic analysis by astigmatism and misalignment. For the Wang algorithms, error introduced by astigmatism was less than 1% of the true value for surfaces with more than 10.00 diopters of astigmatism. A 1-mm translational misalignment of the analyzed surface introduced error of no more than 1.3%. Errors caused by rotational misalignment were less than 3% for misalignments of 5 degrees or less. It is concluded from the error analysis method that the Wang algorithms are sufficiently accurate for use in the analysis of corneal topography. Similar analyses need to be accomplished for the validation of commercially available corneal topography systems.

Algorithms↗

PubMed1991

Astigmatism after small incision cataract surgery. A prospective, randomized, multicenter comparison of 4- and 6.5-mm incisions.

Four surgeons evaluated induced astigmatism and postoperative wound stability in a randomized prospective study of 130 patients undergoing cataract extraction. After phacoemulsification through a scleral pocket, patients received either a 6.5-mm diameter silicone optic posterior chamber intraocular lens (PC IOL) folded for insertion through a 4-mm small incision or a 6.0-mm diameter polymethylmethacrylate (PMMA) optic PC IOL placed through an approximately 6.5-mm conventional incision. Vector analysis calculations of prism diopters (D) of mean postoperative-induced keratometric astigmatism for the small incision versus conventional incision groups were, at day 1, 1.54 D versus 3.07 D (P less than 0.0001); at weeks 1 to 2, 1.00 D versus 2.43 D (P less than 0.0001); at 1 month, 0.98 D versus 1.44 D (P = 0.004); and at 3 months, 0.82 D versus 1.03 D (P = 0.089). Subgroup analysis of the suturing technique for the 6.5-mm incision showed that the technique of wound closure, as well as the wound size, influenced the induced astigmatism. For all four surgeons using three methods of suturing the 6.5-mm wound, however, the variability in the amount of induced cylinder was least with the 4.0-mm wound closed with a horizontal mattress suture. Complications in the two groups were comparable.

Aged↗

PubMed1990

Inadequacy of a polyester (Mersilene) suture for the reduction of astigmatism after penetrating keratoplasty.

Through two prospective studies, we evaluated the use of polyester (Mersilene) sutures in penetrating keratoplasty. Study 1 was a randomized comparison of combined running and interrupted Mersilene and nylon sutures (n = 45). Study 2 was a case series of single running Mersilene with postoperative adjustment of suture tension to manage astigmatism (n = 23). Study 1 demonstrated that Mersilene interrupted sutures were 5.5 times more likely to have handling-related complications compared to nylon (P = 0.01); in addition, they were 3 times as likely to have tissue-related complications as nylon interrupted sutures (P = 0.16). Study 2 demonstrated a complication rate of 69% when Mersilene was used as a single adjustable running suture. At 6 months postoperatively, the median refractive astigmatism for the adjustable cases was 3.37 D (mean, 4.03 +/- 2.37 D). Eyes in Study 2 with significant suture-related complications were 2.85 times more likely to have greater than 4 D of refractive astigmatism than were eyes without suture-related complications. We concluded that Mersilene is an undesirable suture for use in penetrating keratoplasty.

Adult↗