Implantation of spheric phakic posterior chamber intraocular lenses in astigmatic eyes

Implantation of spheric phakic posterior chamber intraocular lenses in astigmatic eyes Heinrich Bleckmann, MD, Richard John Keuch, MD Purpose: To evaluate the simultaneous correction of spherical and cylindrical ametropia through implantation of phakic posterior chamber (PC) intraocular lenses (IOLs) combined with a limbal incision. Setting: Eye Department, Schlosspark-Klinik, Charite´ University Berlin, Berlin, Germany. Methods: In 5 hyperopic and 7 myopic eyes with varying astigmatic measurements, a refractive correction was achieved by implanting phakic PC IOLs (Staar Surgical Co.) and performing limbal incisions of different lengths. The incisions were placed approximately 1.0 mm from the limbus with a mean depth of 600 ␮m and a length of 6.0 mm ⫾ 0.9 (SD). The phakic PC IOLs were implanted after the limbal incisions were placed. Results: In the 5 hyperopic eyes, the astigmatism decreased from 2.7 diopters (D) preoperatively to 0.5 D at a mean of 7.5 ⫾ 1.7 months without alteration of the axis of highest bowing. In the 7 myopic eyes, it decreased from 2.2 D preoperatively to 0.7 D at 7.2 ⫾ 2.6 months. In 3 hyperopic eyes and 1 myopic eye, the limbal incisions were repeated. Conclusions: The observed mean postoperative spherical equivalent was close to emmetropia. Repeat incisions were necessary in eyes exhibiting astigmatism greater than 2.5 D. The advantage of limbal incisions in combination with phakic PC IOL implantation is demonstrated not only by the astigmatic reduction but also by the axis stability. It will be interesting to see whether toric phakic lenses can achieve the same postoperative results, especially in axis stability and reduction of higher degrees of astigmatism. J Cataract Refract Surg 2002; 28:805– 809 © 2002 ASCRS and ESCRS

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n recent years, implantation of intraocular lenses (IOL) in the cornea, anterior chamber, and posterior chamber has become an increasingly popular alternative to subtractive keratorefractive surgery for the treatment of ametropia. Modern phakic posterior chamber (PC) IOLs have distinguished themselves among the therapeutic methods currently available for high degrees of Accepted for publication August 14, 2001. From the Eye Department of Schlosspark-Klinik Berlin, Berlin, Germany. Neither author has a financial interest in any product mentioned. Reprint requests to Prof. Dr. H. Bleckmann, MD, Eye Department of Schlosspark-Klinik Berlin, Heubnerweg 2, 14059 Berlin, Germany. E-mail: [email protected]. © 2002 ASCRS and ESCRS Published by Elsevier Science Inc.

myopia1 and hyperopia.2 Phakic PC IOLs have even been used to treat children with high degrees of myopic amblyopia.3 Therefore, the idea of correcting astigmatic errors during phakic IOL surgery, as is often performed during radial keratotomy (RK), appeared to be a logical step.4 Simultaneous procedures to correct astigmatism errors during RK surgery have been shown to reduce a mean preoperative astigmatism of 2.07 diopters (D) to 0.19 D.5 Similar reductions were obtained through placement of paired T-incisions. Relaxing incisions, placed within the transition zone of the perforating keratoplasty, result in a significantly high rate of regression, reaching 5.5 D in extreme cases.6,7 Yet, the simultaneous correction of preoperative astigmatism during perforating keratoplastic sur0886-3350/02/$–see front matter PII S0886-3350(01)01126-9

PHAKIC IOLS IN ASTIGMATIC EYES

gery using laser in situ keratomileusis appears slightly less effective than the placement of curved incisions.8,9 A comparison of photorefractive keratectomy using T-incisions with photoastigmatic refractive keratectomy for the treatment of myopic astigmatism demonstrates that the former provides more satisfactory results.10 It has also been shown that the placement of T-incisions in a heterogeneous patient population reduces the mean preoperative astigmatism by more than 50%.11

Patients and Methods From January 1999 to February 2000, 12 patients were enrolled in a prospective study to determine the effects of a simultaneous surgical procedure designed to correct preexisting astigmatism. Before implantation of a phakic PC IOL, a curved incision was placed in close proximity to the limbus. Of the 12 patients, 5 were hyperopic and 7 myopic; each had existing astigmatism of varying degrees. In the myopic group, the male to female ratio was 5:2 and in the hyperopic group, 4:1 The mean age of the myopic patients was 37.5 years and of the hyperopic patients, 32.6 years. Follow-up examinations of all patients were performed monthly. The mean follow-up was 7.2 months ⫾ 2.6 (SD) in the myopic group and 7.5 ⫾ 1.7 months in the hyperopic group. The ratio of left to right eyes was 4:3 and 2:3, respectively. All refractive power and visual results are those at the final examination. Patients qualifying for phakic PC IOL implantation with simultaneous correction of preexisting astigmatism demonstrated contact lens incompatibility, dry-eye syndrome, or a wish to improve uncorrected visual acuity (UCVA). All patients were informed of the possibilities and risks involved with phakic PC IOL implantation as well as with the limbal incision and were required to sign a written consent form after reading an information pamphlet. Preoperative and postoperative examinations included subjective and objective miotic/cycloplegic refractions, keratometry, measurement of anterior chamber depth (Nidek biometry), and measurement of the intraocular pressure (IOP) using Goldmann applanation. Gonioscopic examination of the anterior chamber angle and peripheral retina was performed in all patients before surgery. The horizontal whiteto-white length (⫾0.5 mm) was determined with a corneal gauge and used to calculate the proper sized PC IOL. Other parameters affecting the lens calculation included anterior chamber depth, keratometric measurements, and the cycloplegic refraction. The Staar ICL-M version 4 PC IOL was implanted in the myopic patients and the Staar ICL-H version 3, in the hyperopic patients. These foldable IOLs are composed of a 0.1% porcine collagen/hydroxyethyl methacrylate copolymer with 806

a refractive index of 1.45 at 35°C. They can be inserted into the eye through a 3.2 mm incision placed at 12 o’clock or at the axis of the greatest astigmatism. Currently, phakic PC IOLs are available in powers ranging from ⫹9.0 to –17.0 D. The lens power calculation is performed by Staar Surgical Co. The calculation formula variables include the manifest refraction spherical equivalent, the keratometric measurements (D), the corneal thickness (mm), as well as the central anterior chamber depth. Patients were administered topical phenylephrine 10% (Neosynephrin-POS威) and tropicamide 0.5% (Mydraticum Stulln威) approximately 1 hour before surgery. The limbal incision was placed 1.0 mm from the limbus toward the center of the cornea with a 600 ␮m stationary knife (Feather) in the radius of greatest keratometric curvature before the eye was opened for IOL implantation. The length of the limbal incision was chosen according to the Gills method, which requires a single 6.0 mm incision for astigmatism of 2.0 D, 2 6.0 mm incisions for 3.0 D, 2 8.0 mm incisions for 4.0 D, and 2 incisions of 10.0 to 12.0 mm for astigmatic errors greater than 4.0 D (J.P. Gills, MD, D.E. Johnson, MD, “Limbal Relaxing Incisions Help Reduce Astigmatism,” Ophthalmology Times, November 1, 1996, page 27). Patients had local anesthesia by parabulbar injection of 2.5 mL of mepivacaine 2% (Scandicain威) and hyaluronidase (Hylase威). The eye was prepared for phakic PC IOL implantation by placement of a 3.2 mm corneoscleral incision at 12 o’clock using a diamond knife. Two surgical iridotomies 90 degrees apart were performed using a Weckers scissors (Geuder) to prevent angle-closure glaucoma. The anterior chamber was then filled with hypromellose 2% (Acrivisc威), and the lens was inserted into the eye with a microinjector system. Placing the IOL in the injector cartridge was facilitated by a silicone sponge and a mixture of hypromellose 2% and balanced salt solution (BSS威) as a lubricant. Statistical analysis of the results was performed. Median ⫾ standard deviation of the refraction and visual acuity was calculated. Calculation of the induced astigmatism was performed using the vector analysis method developed by Jaffe and Clayman.12

Results Table 1 summarizes the refractive data before and after IOL implantation with simultaneous correction of preexisting astigmatism. It also gives the autorefraction values in both groups. Figure 1 depicts the calculated median values of the preoperative and postoperative spherical equivalents. In the hyperopic group, the median value was ⫹2.65 ⫾ 0.51 before implantation and ⫹0.30 ⫾ 0.24 after implantation; in the hyperopic group, it was ⫺8.14 ⫾ 3.15 and – 0.13 ⫾ 0.32, respectively.

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Table 1. Refractive data before and after IOL implantation with simultaneous astigmatism correction. Measurement

Hyperopia

Myopia

Keratometry

Table 2. Uncorrected visual acuity and BCVA before and after IOL implantation with simultaneous astigmatism correction. Visual Acuity

Hyperopia

Myopia

UCVA

Preop astig

2.70 cyl ⫾ 1.01

2.18 cyl ⫾ 0.87

Preop

0.48 ⫾ 1.50

0.16 ⫾ 0.26

Postop astig

0.50 cyl ⫾ 0.52

0.17 cyl ⫾ 0.41

Postop

0.88 ⫾ 1.16

0.68 ⫾ 0.16

Manifest refraction Preop

Postop

BCVA ⫹3.60 sph ⫾ 4.90

⫺7.29 sph ⫾ 3.16

Preop

0.92 ⫾ 0.37

0.67 ⫾ 0.22

⫺2.10 cyl ⫾ 0.97

⫺1.86 cyl ⫾ 0.52

Postop

0.97 ⫾ 0.35

0.96 ⫾ 0.16

⫹0.65 sph ⫾ 0.20

⫹0.50 sph ⫾ 0.41

⫺0.65 cyl ⫾ 0.21

⫺0.87 cyl ⫾ 0.51

⫹4.55 sph ⫾ 0.19

⫺7.29 sph ⫾ 3.58

⫺2.40 cyl ⫾ 0.92

⫺3.25 cyl ⫾ 2.02

⫹1.50 sph ⫾ 0.10

⫺1.66 sph ⫾ 0.82

⫺0.90 cyl ⫾ 0.25

⫺1.25 cyl ⫾ 0.81

Autorefraction Preop

Postop

All values are median ⫾ SD.

Table 2 shows the best corrected visual acuity (BCVA) and the UCVA after implantation and correction of the astigmatic error. The postoperative BCVA reflects the magnification of the optical image and the reduction of astigmatic power after implantation of the phakic PC IOL in combination with the limbal incision. The astigmatic reduction, achieved through the limbal incisions, was calculated using vector analysis of the median astigmatic values. In the hyperopic group, a significant reduction in the preexisting astigmatism was

UCVA ⫽ uncorrected visual acuity; BCVA ⫽ best corrected visual acuity All values are median ⫾ SD.

achieved, although in some cases multiple treatments were necessary. The surgically reduced astigmatism was not able to completely eliminate the preexisting astigmatism, as shown by the residual astigmatic error in all patients (Figure 2, left). The reduction by the limbal incisions did not change the intended axis and did not exceed the preexisting astigmatism at the perpendicular axis. Keratometric measurements of the 7 myopic patients showed high preoperative and postoperative axis stability, which suggests that no deviation from the intended astigmatic axis occurred as a result of the surgical procedure. The induced astigmatism was positioned approximately 90 degrees to the postoperative astigmatism. The surgical correction was not able to completely compensate for the initial astigmatism among the myo-

Figure 1. (Bleckmann) Spherical equivalent in diopters in hyperopic (left) and myopic (right) eyes before and after implantation of phakic PC IOLs combined with limbal incisions. J CATARACT REFRACT SURG—VOL 28, MAY 2002

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Figure 2. (Bleckmann) Vector analysis (Jaffe and Clayman) of astigmatism in hyperopic (left) and myopic (right) eyes before and after implantation of phakic PC IOLs combined with limbal incisions.

Table 3. Retreatment of limbal incisions. Treatment

Hyperopia

Myopia

1⫻

3

6

2⫻

1

1

3⫻

1

0

pic patients, leaving a minor astigmatic error (Figure 2, right). The induction of the preexisting astigmatism by limbal incisions revealed no major shift compared to the original axis but left a minor part uncorrected. During the study, the limbal incisions were repeated because of redevelopment of the initial astigmatism (Table 3). Topographic analysis was performed monthly, and the decision to repeat limbal incisions was made according to patient availability. The last hyperopic eye had to be retreated 3 times—after 3.5 months and again after 5 months. All repeated incisions were performed with the same length and depth within the original scars. Among the myopic patients, 6 eyes required no follow-up procedures after the initial surgery. One eye needed a second limbal incision equivalent to the hyperopic corrections again after 3.5 months. No myopic eye required more than 2 consecutive incisions.

Discussion The aim of refractive surgery is correction of not only the spherical refractive errors but also the cylindri808

cal component. Toric intraocular contact lenses have become available, leaving little alternative to limbal keratotomy for the treatment of cylindrical errors. Studies show that the success of this procedure depends primarily on the depth of the limbal incision and IOP, which, when increased, may lead to a reduction in corneal refraction. The mechanism of the limbal keratotomy is thought to result from the increase in tensile force, which is distributed along the remaining intact corneal tissue. According to this theory, a corneal separation of 95% can induce a 20-fold increase in the tensile force.13,14 Studies comparing limbal incisions to photoablation for the treatment of myopic astigmatism show that photoablative keratectomy produces less effective and more unpredictable results, especially in cases in which the cylindrical component is greater than 3.0 D,15 although this might not be the case with advanced laser devices. Similarly, the simultaneous treatment of myopic and astigmatic errors using RK was less effective than surgical procedures in which only radial incisions were performed.16 In these cases, the UCVA was significantly lower than the reference values. Another method that affects corneal tensile strength is corneal thermoplasty.17 This, however, has exhibited significant variations in corneal tension in eyes with preexisting T-incisions, as well as RKs, especially when compared to eyes with intact corneal tissue. The most important factor influencing the correction of an astigmatic error using keratotomy incisions is

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the number of incisions performed, followed by the length of the incision and patient age.18 Correction of preexisting astigmatism is also possible using a trapezoidal keratotomy technique19 in which semiradial and transverse keratotomies are used to reduce the refractive error. This method can achieve a mean correction of approximately 2.5 D. In the studies investigating this technique, a correlation between small optical zones and large astigmatic reductions was established. It is not surprising that during the course of the current study, multiple consecutive limbal incisions were occasionally necessary to reduce preexisting astigmatism. It may be assumed that healing processes were partly responsible for closing the primary incisions. Similar observations have been reported by others.20,21 Although the actual depth of the incision does not appear to be affected, general experience shows that a tissue adaptation of 20% already reduces the corrective properties of the incision by 50%.13 In the future, toric lenses will also be able to correct preoperative astigmatism. However, as observed with aphakic IOLs, implanted lenses often shift their axial position, thus reducing the corrective effect of the toric lens or, by rotating 90 degrees, leading to an increase in the astigmatic error.22,23

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8. Webber SK, Lawless MA, Sutton GL, Rogers CM. LASIK for post penetrating keratoplasty astigmatism and myopia. Br J Ophthalmol 1999; 83:1013–1018 9. Donnenfeld ED, Kornstein HS, Amin A, et al. Laser in situ keratomileusis for correction of myopia and astigmatism after penetrating keratoplasty. Ophthalmology 1999; 106:1966 –1974; discussion by JH Talamo, 1974⫺1975 10. Alkara N, Genth U, Seiler T. Astigmatismuskorrektur mittels PRK kombiniert mit T-Inzision und photoastigmatischer Keratektomie; Einjahresergebnisse einer prospektiven klinischen Studie. Ophthalmologe 1998; 95:677– 683 11. Mester U, Grewing R. Operative Korrektur des hochgradigen Hornhautastigmatismus. Ophthalmologe 1993; 90:163–165 12. Jaffe NS, Clayman HM. The pathophysiology of corneal astigmatism after cataract extraction. Trans Am Acad Ophthalmol Otolaryngol 1975; 79:OP615⫺OP630 13. Seiler T, Wollensak J. Zur Theorie der T-Inzision der Kornea. Klin Monatsbl Augenheilkd 1987; 191:120–124 14. Sanders DR, Deitz MR. Factors affecting predictability of radial keratotomy. In: Sanders DR, Hoffmann RF, eds, Refractive Surgery: a Text of Radial Keratotomy. Thorofare, NJ, Slack, 1985; 61⫺66 15. Ganem S, Berbache Sidhoum S. Chirurgie d’astigmatisme myopique: keratotomies arciformes et PRK versus PARK. Bull Soc Belge Ophtalmol 1997; 266:87–90 16. Flanagan GW, Binder PS. Refractive outcome following radial keratotomy and combined radial and astigmatic keratotomy. J Cataract Refract Surg 1997; 23:1057–1063 17. Hargrave SL, Husseini ZM, McCulley JP. Complications of combined radial thermokeratoplasty and incisional keratotomy. CLAO J 1997; 23:205–208 18. Price FW, Grene RB, Marks RG, Gonzales JS. Astigmatism reduction clinical trial: a multicenter prospective evaluation of the predictability of arcuate keratotomy; evaluation of surgical nomogram predictability, the ARC-T Study Group. Arch Ophthalmol 1995; 113:277–282; correction, 577 19. Ibrahim O, Hussein HA, El-Sahn MF, et al. Trapezoidal keratotomy for the correction of naturally occurring astigmatism. Arch Ophthalmol 1991; 109:1374 –1381 20. Chen T-T, Liang Y-S, Tsai J-F, Wu F-J. Surgical results of second-attempt radial keratotomy. Ann Ophthalmol 1985; 17:618 – 620 21. Rowsey JJ, Balyeat HD, Rabinovitch B, et al. Complications of radial keratotomy. In: Henkind P, ed, Acta XXIV International Congress of Ophthalmology. Philadelphia, PA, Lippincott, 1983; 1223⫺1229 22. Mamalis N, Omar O, Veiga J, et al. Comparison of two plate-haptic intraocular lenses in a rabbit model. J Cataract Refract Surg 1996; 22:1291–1295 23. Hwang IP, Clinch TE, Moshifar M, et al. Decentration of 3-piece versus plate-haptic silicone intraocular lenses. J Cataract Refract Surg 1998; 24:1505–1508

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