Clinical results of arcuate incisions to correct astigmatism

Long-term outcomes of limbal relaxing incisions during cataract surgery: aberrometric analysis

PURPOSE

To compare the final changes in corneal wavefront aberration by limbal relaxing incisions (LRIs) after cataract surgery.

METHODS

This prospective cumulative interventional nonrandomized case study included cataract and astigmatic patients undergoing LRIs and phaco with intraocular lens implantation. LRIs were planned using Donnenfeld nomogram. The root mean square of corneal wave aberration for total Z(n,i)(1≤n≤8), astigmatism Z(2,±1), coma Z(3-5-7,±1), trefoil Z(3-5-7,±2), spherical Z(4-6-8,0), and higher-order aberration (HOA) Z(3≤n≤8) was examined before and 3 years after surgery (optical path difference-Scan II [OPD-Scan II)]. Uncorrected distance visual acuity and best-corrected distance visual acuity (CDVA) for distance, keratometric cylinder, and variations in average corneal power were also analyzed.

RESULTS

Sixty-four eyes of 48 patients were included in the study. Age ranged from 42 to 92 years (70.6±8.4 years). After LRIs, uncorrected distance visual acuity and best-corrected distance visual acuity improved statistically (P<0.01). The keratometric cylinder value decreased by 40.1%, but analysis of KP90 and KP135 polar values did not show any decrease that could be statistically confirmed (P=0.22 and P=0.24). No significant changes were detected in root mean square of total (P=0.61) and HOAs (P=0.13) aberrations. LRIs did not induce alteration in central corneal power confirming a 1:1 coupling ratio.

CONCLUSION

LRIs determined a nonsignificant alteration of corneal HOA. Therefore, LRIs can be still considered a qualitatively viable mean in those cases where toric intraocular lenses are contraindicated or not available. Yet, the authors raise the question of nonpersonalized nomograms, as in the present study, LRIs did not reach the preset target cylinder.

The evolution of corneal and refractive surgery with the femtosecond laser

The use of femtosecond lasers has created an evolution in modern corneal and refractive surgery. With accuracy, safety, and repeatability, eye surgeons can utilize the femtosecond laser in almost all anterior refractive procedures; laser in situ keratomileusis (LASIK), small incision lenticule extraction (SMILE), penetrating keratoplasty (PKP), insertion of intracorneal ring segments, anterior and posterior lamellar keratoplasty (Deep anterior lamellar keratoplasty (DALK) and Descemet's stripping endothelial keratoplasty (DSEK)), insertion of corneal inlays and cataract surgery. As the technology matures, it will push surgical limits and open new avenues for ophthalmic intervention in areas not yet explored. As we witness the transition from femto-LASIK to femto-cataract surgery it becomes obvious that this innovation is here to stay. This article presents some of the most relevant advances of femtosecond lasers to modern corneal and refractive surgery.

Long-term refractive stability following combined astigmatic keratotomy and phakoemulsification

BACKGROUND

To determine whether combined astigmatic keratotomy and cataract surgery induces a sustained reduction in astigmatism.

METHODS

Patients who had previously undergone combined cataract surgery and astigmatic keratotomy for naturally occurring astigmatism were identified and their notes reviewed. Mean final follow-up was 34 months (30-42 months). Fourteen eyes of 11 patients were eligible for study. Arcuate corneal incisions had been employed using the Buzard nomogram. Using power vector analysis, the post-operative refractive change at 6 months and final follow-up was determined.

RESULTS

The mean preoperative manifest cylindrical refractive error was 2.88 D (1.50-5.50 D). The mean postoperative manifest cylindrical refractive error was 1.89 and 1.79 D at 6 months and final follow-up, respectively. Power vector analysis demonstrated a significant postoperative reduction in refractive blur at 6 months and final follow-up (P = 0.006, P = 0.004, respectively): mean preoperative blur strength was 2.90 D and mean postoperative blur strength was 1.33 and 1.25 D at 6 months and final follow-up, respectively. Sustained postoperative reduction in astigmatism was noted in 12 of 14 eyes at final follow-up.

CONCLUSIONS

Astigmatic keratotomy is a well-established treatment for astigmatism. In this series, the refractive benefit from combined astigmatic keratotomy and cataract surgery is maintained for several years. No surgical complications were observed.

Correction of astigmatism with short arc-length intrastromal corneal ring segments: preliminary results

OBJECTIVE

To evaluate the refractive effect of 130 degrees short arc length intrastromal corneal ring segments (ICRS) designed to correct myopia concurrent with astigmatism.

DESIGN

Prospective, nonrandomized, comparative (self-controlled) trial.

PARTICIPANTS

Ten eyes of 6 patients from one surgical center with manifest refraction spherical equivalent between -1.00 and -6.00 diopters (D), manifest cylinder correction between 1.00 and 6.00 D, and best spectacle-corrected visual acuity of 20/20 or better.

INTERVENTION

The patients were assigned to receive 1 of 6 ICRS thicknesses, ranging from 0.25 to 0.50 mm by 0.05 mm increments, with an arc length of 130 degrees.

MAIN OUTCOME MEASURES

Vector analysis of astigmatic correction. Efficacy was assessed by uncorrected visual acuity and by deviation of postoperative spherical and cylindrical refractive error from predicted correction. Safety was assessed by maintenance or loss of preoperative best spectacle-corrected visual acuity. Measurements were made before surgery and after surgery at days 1 and 7 and months 1, 2, 3, and 6.

RESULTS

At 6 months, uncorrected visual acuity was 20/20 or better in 80% of eyes (8/10) and 20/40 or better in all eyes. Eight of 10 eyes (80%) were within +/-0.25 D of plano spherical equivalent manifest refraction. There was no loss of best spectacle-corrected visual acuity, and 6 of 10 eyes (60%) gained a line. Reduction of keratometric cylinder by ICRS thickness was statistically significant (P = 0.039).

CONCLUSIONS

Preliminary results of visual and refractive performance after correction of compound myopic astigmatism using short arc length ICRS are promising.

Toric intraocular lenses for correcting astigmatism in 130 eyes

OBJECTIVE

This study evaluated the results after implantation of toric intraocular lenses (IOLs) to correct preexisting corneal astigmatism in patients undergoing either cataract or clear lens extraction surgery.

DESIGN

Retrospective, noncomparative case series.

PARTICIPANTS

One hundred thirty eyes of 99 patients who underwent phacoemulsification and posterior chamber toric IOL implantation from January 1997 through February 1998 were included in the study.

INTERVENTION

Implantation of a toric IOL was performed after cataract surgery (122 eyes) or clear lens extraction surgery (eight eyes). Both preoperative corneal cylinder and refractive cylinder powers were more than 1.50 diopters (D) for all the eyes included in this study. To provide a comparison, we also studied 51 eyes of 45 patients meeting the same preoperative criteria for degree of corneal and refractive cylinder who underwent implantation of a spherical (nontoric) IOL combined with limbal relaxing incisions. The data for both study and comparison groups were analyzed retrospectively. The selection for the two groups was arbitrary.

MAIN OUTCOME MEASURES

Uncorrected visual acuity (UCVA), mean spherical equivalent, residual refractive cylinder, and toric IOL axis.

RESULTS

In the toric IOL group, 84% of eyes achieved 20/40 or better UCVA. In the spherical IOL group, 76% achieved 20/40 or better UCVA. The mean postoperative refractive cylinder was -1.03 +/- 0.79 D in the toric IOL group and -1.49 +/- 0.75 D in the spherical IOL group.

CONCLUSIONS

Our results indicate that phacoemulsification and posterior chamber toric IOL implantation is a largely predictable new surgical option to correct preexisting corneal astigmatism in cataract or clear lens extraction surgery.

Transconjunctival corneoscleral tunnel "blue line" cataract incision

PURPOSE

To report the technique and astigmatic results of the blue line cataract incision.

SETTING

The Buzzard Eye Institute, Las Vegas, Nevada, USA.

METHODS

This prospective study included 411 eyes of 271 patients who had cataract extraction by phacoemulsification with a self-sealing 3.0 mm blue line cataract incision. The blue line incision is performed with a diamond knife transconjunctively, 2.0 mm behind the surgical limbus.

RESULTS

Mean patient age was 68 years (range 40 to 94 years) and mean preoperative astigmatism, 0.96 diopter (D) +/- 0.78 (SD). Uncorrected visual acuity at 1 day was 20/40 or better in 47% of patients. Mean spherical equivalent was -0.57 +/- 0.78 D at 6 months. Mean postoperative astigmatism measured with a subtraction method was 1.00 +/- 0.84 D at 6 months. Vector analysis showed an induced astigmatism of -0.47 +/- 1.00 D at 1 month, -0.58 +/- 0.81 D at 3 months, and -0.57 +/- 0.99 D at 6 months. No complications such as wound leakage or hyphema occurred.

CONCLUSION

The blue line incision combines the efficiency of the clear corneal with the safety of the scleral tunnel cataract incision and appears to be relatively astigmatically neutral.

Effect of astigmatic keratotomy on spherical equivalent: results of the Astigmatism Reduction Clinical Trial

PURPOSE

To determine the effect of astigmatic keratotomy on spherical equivalent, as measured by the coupling ratio and a new quantity, coupling constant.

METHODS

In a prospective multicenter study, subjects underwent arcuate keratotomy at a 7-mm optical zone by means of the Lindstrom nomogram for correction of astigmatism. One hundred fifty-seven eyes of 95 patients who had a follow-up examination 1 month postoperatively were studied. Mean preoperative refractive cylinder +/- SEM was 2.82 +/- 1.17 diopters. Coupling ratio was defined as the ratio of the flattening of the incised meridian to the steepening of the opposite meridian. Coupling constant was defined as the ratio of the change in spherical equivalent to the magnitude of the vector change in astigmatism. Coupling ratio, coupling constant, and change in spherical equivalent were calculated on the basis of change in refraction and keratometry.

RESULTS

On the basis of change in refraction, coupling ratio was 0.95 +/- 0.10 (mean +/- SEM) and coupling constant was -0.01 +/- 0.03, consistent with a minor shift in the spherical equivalent of -0.03 +/- 0.07 diopter. On the basis of change in keratometry, coupling ratio was 0.84 +/- 0.05 and coupling constant was -0.04 +/- 0.02, consistent with minor postoperative keratometric steepening of -0.10 +/- 0.04 diopter. Coupling ratio based on change in refraction was not statistically different from the coupling ratio predicted by the Gauss' law for inelastic domes (P = .370). Incision length and number, amount of achieved cylinder correction, age, and sex had no statistically significant effect on coupling ratio, coupling constant, and change in spherical equivalent.

CONCLUSIONS

Cornea behaved as an inelastic surface in response to arcuate keratotomy performed with the Astigmatism Reduction Clinical Trial study nomogram. On average, astigmatic keratotomy had a minimal effect on spherical equivalent refraction. There was variability, however, in coupling ratio, coupling constant, and change in spherical equivalent from eye to eye after astigmatic keratotomy. Caution is therefore advised when simultaneous correction of cylinder and spherical equivalent is planned.

Arcuate keratotomy to treat corneal astigmatism after cataract surgery: a prospective evaluation of predictability and effectiveness

OBJECTIVE

Although several nomograms are available for the incisional keratotomy to correct naturally occurring astigmatism, astigmatic keratotomy in eyes after cataract surgery has not been well analyzed. The predictability and effectiveness of arcuate keratotomy in pseudophakic eyes were studied.

DESIGN

A prospective, multicenter study.

PARTICIPANTS

One hundred four eyes of 86 patients with residual corneal astigmatism of 1.5 diopters (D) or more after cataract surgery were examined.

INTERVENTION

Arcuate keratotomy was performed in nine centers by nine surgeons.

MAIN OUTCOME MEASURES

The amount of astigmatic correction was calculated using the vector analysis of preoperative and 6-month postoperative refractive cylinder results.

RESULTS

Multiple regression analysis showed that optical zone size, number of incisions, and incision length had significant correlations with the amount of astigmatic correction. The regression equation was expressed as effects = (-0.643 x optical zone size) + (0.998 x incision number) + (0.057 x incision length) + 2.356. The parameter of predictability (r2: 35%) was lower than that reported for congenital astigmatism (48 to approximately 56%). A new nomogram was derived based on the multiple regression equation.

CONCLUSIONS

Astigmatic keratotomy in pseudophakic eyes is less predictable than that in eyes with idiopathic astigmatism, but the procedure is sufficiently effective in reducing the residual astigmatism after cataract surgery. Individual nomograms are necessary for astigmatic keratotomy in eyes with naturally occurring and postsurgical astigmatism.