Against-the-rule Astigmatism Research Articles

Peripheral corneal relaxing incisions combined with cataract surgery

Purpose To analyze the effectiveness of peripheral corneal relaxing incisions (PCRIs) in correcting corneal astigmatism during cataract surgery. Setting Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. Methods In 115 eyes of 94 patients (mean age 69 years ± 12 [SD]), cataract surgery was combined with PCRIs. The PCRIs were created according to a nomogram based on age and preoperative keratometric astigmatism. Postoperative keratometric astigmatism was measured at 1 day and 1 and 4 months. Vector analyses using the Holladay-Cravy-Koch formula and Alpins method were performed. Results The PCRIs significantly decreased keratometric astigmatism in patients with preexisting with-the rule (WTR) or against-the-rule (ATR) astigmatism and increased the percentage of the eyes with lower keratometric astigmatism in each group. Four months postoperatively in patients with WTR astigmatism, single and paired 6.0 mm PCRIs induced mean with-the-wound minus against-the-wound changes (WTW–ATW) of −0.55 diopter (D) and −1.18 D, respectively. In eyes with ATR astigmatism, the mean WTW–ATW changes induced by single 4.5 mm, single 6.0 mm, and paired 6.0 mm PCRIs were −2.18 D, −2.02 D, and −2.72 D, respectively. These mean WTW–ATW changes did not significantly regress from 1 day to 4 months postoperatively. Conclusions Peripheral corneal relaxing incisions were effective in reducing preexisting astigmatism during cataract surgery. A modified nomogram is proposed. The long-term effect of PCRIs should be evaluated.

Against-the-rule (ATR) astigmatism as a predicting factor for the outcome of amblyopia treatment

PURPOSE: To evaluate whether with-the-rule (WTR) or against-the-rule (ATR) astigmatism influences the treatment outcome of anisometropic amblyopia. DESIGN: A cohort study. METHODS: Retrospective study of patients with unilateral amblyopia due to anisometropia without strabismus. Ninety-eight patients with simple, compound, mixed, oblique myopic, and hyperopic astigmatism were divided into seven groups based on the type of astigmatism. The groups were reviewed as to the amount of anisometropia, duration of occlusion, and best-corrected visual acuity (BCVA) before and after treatment. RESULTS: There was statistically significant longer duration of occlusion and less lines gain of BCVA among patients with hyperopic ATR astigmatism compared with patients with hyperopic WTR astigmatism ( P = .0143 and P = .0000, respectively) and myopic ATR patients compared with myopic WTR patients ( P = .0392 and P = .0192, respectively). For the same parameters, group differences were also statistically significant when all hyperopic or myopic simple/compound/mixed ATR patients were compared with all hyperopic or myopic simple/compound/mixed WTR patients ( P = .0015 and P = .0000, respectively). CONCLUSION: The outcome of amblyopia treatment seems to be less favorable in patients with either hyperopic or myopic ATR astigmatism. Near vision impairment may be more amblyogenic than distance vision impairment during visual development.

Management of corneal epithelial defects following laser in situ keratomileusis.

To determine the main principles of postoperative management in patients with epithelial defects following LASIK. Patients with myopia and myopic astigmatism (N=2,972; refraction from -1.25 to -15.50 D) were treated with the Nidek EC-5000 excimer laser, using the Chiron Vision HT-230 Hansatome microkeratome. We observed 95 cases with intraoperative epithelial damage among 5,896 operations (1.6%) . Patients received traditional topical medical treatment (Tobramycin 0.3%, five times a day; Lacrisifi, six to eight times a day). In eyes with an epithelial defect less then 3 mm, no additional medical care was needed. In eyes with epithelial defects more then 3 mm, soft therapeutic contact lenses were used until total re-epithelialization occurred. Total re-epithelialization was observed the day following surgery in patients with small defects (less then 3 mm). Visual acuity achieved preoperative level 4 to 7 days after surgery. Total re-epithelialization in patients with soft contact lenses occurred 1 to 3 days after LASIK. On the next day examination, Solcoseryl 20% eye gel was added to topical therapy for corneal healing. In these patients visual acuity achieved preoperative level 10 to 14 days after surgery. In three eyes with large epithelial defects (4 to 5 mm), irregular astigmatism (one eye; 0.02%) or against-the-rule astigmatism (two eyes; 0.03%) occurred. Patients complained of blurred and double vision. Transepithelial phototherapeutic keratectomy was performed after 3 months for epithelial smoothing, with good visual results. Management of epithelial defects following LASIK can be concentrated on avoiding epithelial hyperplasia. Epithelial defects less than 3 mm do not appear to produce epithelial hyperplasia. Irregular astigmatism induced by LASIK can result in reduced best spectacle-corrected visual acuity. A common cause of irregular astigmatism is corneal epithelial remodeling and corneal thickening secondary to corneal epithelial defects created at the time of the LASIK procedure.

Induced astigmatismafter photorefractive keratectomy

Purpose: To retrospectively analyze a group of patients to determine whether their induced astigmatism was caused by asymmetry in the laser beam, asymmetry in ablation rates, or wound healing in different corneal meridians. Setting: Single-center physician office. Methods: In this study, 146 eyes of 116 patients who had photorefractivakeratectomy(PRK) for myopia with the Apex laser (Summit Technology) were retrospectively identified. In 28 eyes, the patient's chair had been rotated 90 degrees from its usual position under the laser. The vector-summated mean change in astigmatism in eyes with the chair rotated 90 degrees was compared with that in a group of control eyes in which the chair was in the usual position. Results: The vector-summated mean change in the control eyes was 0.30 diopter (D)at 83 degrees. Forty-eight of 113 eyes (42.5%) had induced with-the-rule (WTR) astigmatism, and 14 of 113 eyes (12.4%) had induced against-the-rule (ATR) astigmatism. In the eyes in which the chair was rotated 90 degrees, vector-summated mean change was 0.10 D at 13 degrees ( P < .0005). One of 27 eyes (3.7%) had induced WTR astigmatism, and 13 of 27 eyes (48.1%) had induced ATR astigmatism ( P < .001, chi-square). Conclusion: Astigmatism induced by myopic PRK with the Apex laser was small. The axis of induced astigmatism rotated 90 degrees when the patient's chair was rotated, implying that it is inhomogeneities in the beam rather than meridional asymmetry in ablation rates or wound healing that are responsible for induced astigmatism.[]

Benefit of against-the-rule astigmatism to uncorrected near acuity

Purpose: To determine whether with-the-rule (WTR) or against-the-rule (ATR) astigmatism gives a better visual outcome after cataract and intraocular lens (IOL) implantation surgery by comparing the uncorrected distance and near visual acuities in eyes with low, simple, myopic residual astigmatism.Setting: S. Geraldo Eye Hospital, Federal University of Minas Gerais, Belo Horizonte, Brazil.Methods: Two groups of 10 eyes each, one with WTR and the other with ATR simple, myopic astigmatism, were studied after uneventful cataract and IOL implantation surgery. All patients had an uncorrected distance visual acuity of 20/40 or better. The negative cylinder ranged from 1.00 to 1.50 diopters (D). The uncorrected distance and near visual acuities of the two groups were compared.Results: There was no statistically significant between-group difference in uncorrected distance visual acuity. However, for uncorrected near, the difference between groups was highly statistically significant (P < .001). Patients with ATR astigmatism had much better uncorrected near acuity than those with WTR astigmatism.Conclusion: In pseudophakia, low, simple, ATR myopic astigmatism is better than WTR astigmatism because it provides superior uncorrected near visual acuity.

Radial Suture Stabilized by Fibrin Glue to Correct Preoperative Against-the-Rule Astigmatism During Cataract Surgery

We evaluated the efficacy of using a modified wound-closure technique in cataract surgery to reduce presurgical against-the-rule (ATR) astigmatism. Seventy-seven eyes received a radial 10-0 nylon suture in the axis of the preexisting ATR cylinder, combined with an application of fibrin glue to stabilize the wound. A control group of 76 patients with comparable preoperative ATR astigmatism was operated on in the same manner, but only fibrin glue and no suture was used for wound closure. The mean induced astigmatism in these two groups differed by 0.42 diopters, a significant difference (P < .05). In the cases with preoperative astigmatism greater than 1.00 D, the difference between the two groups, again a significant one, was 0.73 (P < .05).

Against-the-rule astigmatism judged at one week after phacoemulsification and aspiration procedures.

To determine the characteristics of astigmatism 1 week postoperatively or whether the final astigmatism is predictable from that present 1 week postoperatively, we analyzed 544 postcataract against-the-rule (AR) cases of astigmatism among 1,649 standard phacoemulsification cataract operations, all utilizing 10-0 Mersilene in double-running fashion. Postoperative AR astigmatism < or = 1.0 dpt increased markedly 1 week postoperatively (2.72 +/- 0.09 dpt) but decreased 6 months postoperatively. However, in postoperative AR astigmatism > 2.0 dpt, the increase 1 week postoperatively was not as great (2.16 +/- 0.13 dpt) but tended to continue to increase even 6 months postoperatively, with a flatter corneal curvature being the responsible factor. Eyes with less astigmatism 1 week postoperatively showed exacerbation of final astigmatism 6 months postoperatively. This course was different from that of small incision cataract surgery.

Reduction of postoperative against-the-rule astigmatism by lateral incision technique

A group of 80 preoperative against-the-rule (AR) eyes had cataract removal and intraocular lens implantation with lateral (temporal) incision and suturing. Fifty-six of the 80 eyes had extracapsular cataract extraction (ECCE) and 24 had phacoemulsification (KPE) with capsulorhexis. For both procedures, subgroups (21 of ECCE, ten of KPE) with high preoperative AR astigmatism (≥ -2.0 D) were evaluated. Analysis of the postoperative data provided the following: (1) induced postoperative cylinder decrease, (2) effect of cutting and not cutting sutures, (3) induced axial shift, (4) postoperative astigmatic change as a function of time, and (5) comparative effectiveness of ECCE and KPE lateral incision procedures in reducing postoperative AR astigmatism.

Outcome of preoperative against-the-rule astigmatism after phacoemulsification: characteristic changes over time. Part II.

To determine the outcome of preoperative against-the rule (AR) astigmatism among 1,648 phacoemulsification and aspiration (PEA) procedures, we analyzed the post-cataract time course of astigmatism over 6 months in 618 eyes divided into three groups. In preoperative AR astigmatism less than 0.75 dptr (n = 208), the astigmatism increase 1 week postoperatively was rapid. In preoperative AR astigmatism greater than or equal to 1.5 dptr (n = 185), no difference in the power of astigmatism was apparent between 1 and 3 months postoperatively. The third group (0.75 less than or equal to preoperative AR astigmatism less than 1.5 dptr, n = 143) showed intermediate characteristics. The eyes with preoperative low AR astigmatism showed exacerbation of astigmatism after the PEA procedure, whereas the degree of astigmatism, corneal curvatures and the rate of AR astigmatism became lower in the eyes with higher preoperative AR astigmatism.

Sudden Against-the-Rule Astigmatism 6 Months after Intraocular Lens Implantation with the Kelman Phacoemulsification Procedure: 4 of 809 Cases

Of 809 eyes that underwent the Kelman phacoemulsification and aspiration (KPE) procedure, we report on 4 patients (0.49%) who developed sudden against-the-rule (AR) astigmatism after intraocular lens implantation. These patients had had with-the-rule astigmatism preoperatively to 3 months postoperatively and suddenly developed AR astigmatism 6 months after surgery. To study the development and progression of AR astigmatism in these patients (group A), we compared their 6-month time course with that of 257 patients (group B) with postoperative AR astigmatism. In group A, the degree of astigmatism was not significantly different from group B astigmatism preoperatively (1.03 +/- 0.16 vs. 1.04 +/- 0.04 dptr) and 6 months postoperatively (1.32 +/- 0.13 vs. 1.26 +/- 0.05 dptr). However, 1 week postoperatively, the astigmatism of the 4 cases was much greater (5.72 +/- 0.14 dptr) than that of the others (2.32 +/- 0.07 dptr). These rare 4 cases, which had no other unusual characteristics, are indicative of the importance of a careful follow-up even if the post-KPE course seems uneventful.

Effect of suture material on postoperative astigmatism

Two hundred patients were enrolled in a randomized, prospective clinical trial comparing the use of 10-0 nylon, 10-0 polypropylene (Prolene®), 11-0 polyester (Mersilene®), and 10-0 polyethylene (Novafil®) suture materials on the amount and decay curves of surgically induced astigmatism following intraocular lens (IOL) surgery. Patients with Mersilene and nylon sutures had the highest amounts of induced with-the-rule (WTR) cylinder (significantly more than Prolene) at one day after surgery. However, the WTR cylinder decayed rapidly for nylon during the first three months but more slowly for Mersilene because of its lack of stretchability. The Prolene group had the lowest level of induced WTR cylinder at one day, but against-the-rule (ATR) drift occurred, leaving cases with ATR astigmatism by a year. The nylon group had the second highest amount of induced WTR cylinder at one day, which had decayed to ATR cylinder by five months. Between one and two years postoperatively, the nylon group experienced a significant ATR shift. The amount of early induced WTR cylinder seemed to be related to the knot-tying technique and tissue gripping characteristics, whereas the shape of the decay curve was related to the material characteristics of the suture.

Paired transverse relaxing keratotomy: A combined technique for reducing astigmatism

Phacoemulsification, posterior chamber intraocular lens implantation, and corneal relaxing incisions were performed as a combined procedure in 75 eyes with preexisting with-the-rule or against-therule astigmatism. The results of this study confirm that this technique can safely- reduce preexisting low and moderate astigmatism with a greater likelihood of achieving excellent uncorrected visual acuity.

Astigmatism occurring in association with pediatric eye disease.

Retrospective clinical data from 496 eyes of 256 children attending a low vision clinic were analyzed to determine the relation between different classes of disease that involve visual image degradation and astigmatism. Control data comprised refractions from 79 normal vision children. Children were classified into groups according to the category of disease (14 groups) and the reported age-of-onset of their visual disability (0 to 13 years, 5 groups). The mean astigmatism for all groups of children with low vision was larger than that of the normals and in most cases the difference was significant at the 95% level. Astigmatism was highest in children with albinism, retinitis pigmentosa, and idiopathic nystagmus. Increased prevalence of astigmatism compared to normals was noted in children having their onset of low vision as late as 13 years of age. In the low vision subjects with-the-rule astigmatism occurred more frequently than oblique or against-the-rule astigmatism and oblique astigmatism more frequently than against-the-rule astigmatism.