- Email: [email protected]
Optimal incision sites to obtain an astigmatism-free cornea after cataract surgery with a 3.2 mm sutureless incision
Optimal incision sites to obtain an astigmatism-free cornea after cataract surgery with a 3.2 mm sutureless incision Yukihiro Matsumoto, MD, Tsutomu Hara, MD, Keizo Chiba, MD, Makoto Chikuda, MD ABSTRACT Purpose: To determine the optimal incision to eliminate astigmatism after cataract extraction. Setting: Hara Eye Hospital, Utsunomiya, Japan. Methods: Patients having cataract extraction through a 3.2 mm corneal limbal incision without limbal sutures were divided into 2 groups. Group 1 comprised 98 eyes of 80 patients without preoperative astigmatism and Group 2, 72 eyes of 62 patients with no astigmatism postoperatively. In Group 1, the incisions that caused postoperative corneal changes were retrospectively evaluated. In Group 2, the types of incisions that induced an astigmatismfree cornea postoperatively were retrospectively studied. Patients were examined preoperatively and 6 months postoperatively. Results: In Group 1, 23 of 40 eyes (57.5%) with an incision between 9 and 12 o’clock (BENT incision) and 10 of 58 eyes (17.2%) with an incision at 12 o’clock remained astigmatism free postoperatively (P ⬍ .0001). One eye (2.5%) with a BENT incision and 17 (29.3%) with a 12 o’clock incision had astigmatism greater than 1.0 diopter (D) postoperatively (P ⬍ .001). In Group 2, 72 eyes had less than 1.2 D of preoperative astigmatism. No eye with more than 1.2 D of astigmatism was astigmatism free postoperatively, even when the incision was made at the steepest meridian. Conclusions: The results indicate that to reduce astigmatism in eyes with preoperative astigmatism of 0.5 D or more, a limbal 3.2 mm BENT incision should be placed at 10:30 o’clock. To prevent astigmatism postoperatively, the incision should be placed at the steepest meridian in eyes with preoperative astigmatism greater than 0.5 D; for preoperative astigmatism greater than 1.2 D, a 3.2 mm incision at the corneal limbus is insufficient and a wider incision or an additional incision is required. J Cataract Refract Surg 2001; 27:1615–1619 © 2001 ASCRS and ESCRS
T
he popularity of cataract surgery as a refractive procedure has been increasing. Regardless of the preoperative refraction, obtaining an astigmatism-free eye Accepted for publication February 19, 2001. Reprint requests to Yukihiro Matsumoto, MD, Room 5-65, MSTF, 10 South Pine Street, Baltimore, Maryland 21201, USA. E-mail: [email protected]. © 2001 ASCRS and ESCRS Published by Elsevier Science Inc.
postoperatively is the objective.1–3 Many reports of incision types and surgically induced astigmatism (SIA) have appeared in the literature. Incision types include the 12 o’clock, between 9 and 12 o’clock (BENT),4 temporal,5 and steep meridian.6 –10 Some studies of incision site address the presence and type of suture,11 use of a wider incision,7 and use of a narrower incision.5,6,8,12,13 In several studies, to reduce 0886-3350/01/$–see front matter PII S0886-3350(01)00876-8
INCISION SITES TO LIMIT ASTIGMATISM AFTER CATARACT SURGERY
the SIA,8,14,15 the incision was shortened to 3.2 mm.12,13,15–17 Reports of 3.2 mm incisions indicate that the 12 o’clock,12,13 BENT,15,16 temporal,17 and steep meridian incision should be used. In addition, some authors describe a corneoscleral incision,12,13 a corneal incision,17 or a method of calculating SIA.18 –23 To determine the effective incision site and direction, it is necessary to eliminate the effect of suturing, incision width, and operative method and to choose eyes with certain preoperative corneal conditions.24,25 These studies compared groups of patients differently; that is, by incision site, incision width, surgical method, suture method, presence of a suture, or incision type. Thus, the authors reached different conclusions that were not always consistent with the results in other studies. To clarify the relation between incisions and SIA, we studied the effect of a 3.2 mm incision without sutures placed at the limbus in patients with no preoperative astigmatism and in another group with no postoperative astigmatism. In the former group, we evaluated the effect of incision type on postoperative corneal changes. In the latter, we retrospectively evaluated the preoperative corneal condition and the incision type and site.
Patients and Methods Patients had extraction of a senile cataract at the Hara Eye Hospital from November 1996 to March 1998. The mean age of the patients was 69.0 years ⫾ 7.4 (SD) (range 47 to 90 years).
One surgeon (T.H.) performed all surgeries using the same technique. Anesthesia was induced using tetracaine 0.5% eyedrops. The cataract was removed by phacoemulsification (Cavitron 20000, Alcon Japan Ltd.) through a 3.2 mm incision made with a diamond blade at the corneal limbus. The incision was not sutured. A 3-piece acrylic intraocular lens (Alcon Japan Ltd.) with a 5.5 mm optic and an overall length of 13.0 mm was implanted in the capsular bag with the loops in a horizontal position. An astigmatism-free eye was defined as one in which the difference between the steep simulated K-reading and flat simulated K-reading and the difference between the steepest corneal curvature (refractive power) and the flattest corneal curvature were within ⫾0.5 diopter (D). The corneal curvature was obtained using numeric analysis in 3.0 mm increments from the center measured by a corneal shape analyzer (CAS model 2, EyeSys Technologies Inc.) In addition, a concentric pattern with good symmetry was observed by corneal topographic analysis (Figure 1). The presence of astigmatism was measured preoperatively and 6 months postoperatively. The astigmatism changes were presented as the difference between the steep simulated K-reading and the flat simulated K-reading. The patients were divided into 2 groups. Group 1 comprised 98 eyes (80 patients) that were free of corneal astigmatism preoperatively. The mean age in Group 1 was 70.1 ⫾ 8.4 years (range 47 to 90 years). To determine which type of incision induced postoperative astigmatism less frequently, a BENT incision (placed around
Figure 1. (Matsumoto) An astigmatism-free cornea. Left: Color map analysis. Right: Numeric analysis. 1616
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Figure 2. (Matsumoto) Postoperative corneal changes resulting from the use of a BENT incision. Left: Astigmatism-free cornea preoperatively. Right: A BENT incision 6 months postoperatively in a case in which a 3.2 mm wide incision was placed at the 10:30 position on the corneal limbus. The changes in corneal shape from preoperatively were minimal.
10:30 o’clock in 40 eyes of 33 patients) or a 12 o’clock incision (58 eyes, 47 patients) was used. Group 2 comprised 72 eyes (62 patients) that were free of corneal astigmatism postoperatively. The mean age in Group 2 was 68.2 ⫾ 9.3 years (range 47 to 90 years). In Group 2, patients were placed into 1 of 2 subgroups based on the severity of the preoperative corneal astigmatism: less than 0.5 D (33 patients, 36 eyes) or 0.5 D and greater (29 patients, 36 eyes). Patients were also placed in subgroups according to incision type: at the steepest meridian (within 30 degrees around the incision site) or in the direction of the nonsteep meridian. Excluded were eyes with myopia of –10.0 D or higher, keratoconjunctival disease, glaucoma, or a history of intraocular surgery. Statistical analysis was by the chi-square test. The types of incisions and the results are shown in ascending order of frequency of SIA.
Results Figure 2 shows topography of postoperative corneal changes in an eye with a BENT incision. Figure 3 shows topography of postoperative corneal changes in an eye with an incision at the 12 o’clock position.
In Group 1, of the 40 eyes (29 right, 11 left) with a BENT incision, 23 (57.5%; 18 right, 5 left) remained astigmatism free postoperatively. Ten of 58 eyes (17.2%) with a 12 o’clock incision remained astigmatism free. The difference was significant (P ⬍ .0001). The percentage of eyes in which 1.0 D or more of corneal astigmatism was induced was significantly higher in the 12 o’clock incision group (17 eyes, 29.3%) than in the BENT incision group (1 eye, 2.5%) (P ⬍ .001). When the 12 o’clock incision was used, a maximum of 1.78 D of astigmatism remained between 41 and 131 degrees. In Group 2, of the 36 eyes with preoperative astigmatism of less than 0.5 D, the incision was at the steepest meridian in 18 eyes (BENT in 11, 12 o’clock in 4, temporal in 2, and other in 1) and at the nonsteep meridian in 18 eyes (BENT in 12 and 12 o’clock in 6). In eyes with preoperative astigmatism of 0.5 D or greater (n ⫽ 36), the incision was at the steepest meridian in 29 eyes (BENT in 6, 12 o’clock in 16, temporal in 5, and other in 2) and at the nonsteep meridian in 7 eyes (BENT in 2, 12 o’clock in 3, and temporal in 2). The incision was at the steepest meridian in 18 of 36 eyes (50.0%) with a preoperative astigmatism less than 0.5 D and in 29 of 36 eyes (80.6%) with a preoperative astig-
Figure 3. (Matsumoto) Postoperative corneal changes caused by an incision placed at the 12 o’clock position. Left: Astigmatism-free cornea preoperatively. Right: A 12 o’clock incision 6 months postoperatively in a case in which a 3.2 mm wide incision was placed at the 12 o’clock position on the corneal limbus. The wound-related flattening and steepening to the upper central cornea persisted.
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matism of 0.5 D or higher (P ⬍ .01). No eye with a preoperative astigmatism of 1.2 D or greater was astigmatism free postoperatively, even when the incision was at the steepest meridian.
Discussion Most studies of SIA make comparisons based on different factors including the suturing method, presence of a suture, incision type, type of operation, and incision width. Because of the different parameters, the result do not agree among studies. One reason is the complicated calculations required for correction to make a comparison because the incisions are made in eyes with various degrees of preoperative astigmatism.18 –23 In our study, the patient selection process enabled us to observe the changes caused by the incisions without performing complicated calculations. To the best of our knowledge, no reported study has used this method. Postoperative astigmatism developed less frequently in the patients with a BENT (10:30 o’clock) incision than in those with a 12 o’clock incision. In addition, the BENT incision had less of an effect on the central and paracentral corneal zones than the 12 o’clock incision in eyes with a preoperative astigmatism of less than 0.5 D. Compared with the 12 o’clock incision, these results were consistent with those in previous reports.4,9,10,16,25–27 However, although an incision at the steepest meridian effectively minimized the chances of inducing and relieving astigmatism, there seemed to be a limitation.11 In conclusion, to avoid postoperative astigmatism, we recommend making the incision on the steepest meridian in eyes with a preoperative astigmatism of 0.5 D or higher. However, astigmatism higher than 1.2 D cannot be eliminated by a 3.2 mm wide incision made at the corneal limbus and a wider incision27 or an additional incision2,3,28 is required. To avoid postoperative astigmatism in eyes with a preoperative astigmatism of 0.5 D or lower, we recommend placing the incision at approximately 10:30 o’clock rather than at 12 o’clock in cases in which a 3.2 mm wide incision is placed at the limbus. Although a large number of studies in the literature report incisions and postoperative astigmatism data, the present study provides simpler and clearer results based on proper patient selection. 1618
References 1. Nordan LT, Lusby FW. Refractive aspects of cataract surgery. Curr Opin Ophthalmol 1995; 6(1):36 – 40 2. Kershner RM. Keratolenticuloplasty: arcuate keratotomy for cataract surgery and astigmatism. J Cataract Refract Surg 1995; 21:274 –277 3. Kershner RM. Clear corneal cataract surgery and the correction of myopia, hyperopia, and astigmatism. Ophthalmology 1997; 104:381–389 4. Kawano K. Modified corneoscleral incision to reduce postoperative astigmatism after 6 mm diameter intraocular lens implantation. J Cataract Refract Surg 1993; 19: 387–398 5. Kohnen T, Dick B, Jacobi KW. Comparison of the induced astigmatism after temporal clear corneal tunnel incisions of different sizes. J Cataract Refract Surg 1995; 21:417– 424 6. Neumann AC, McCarty GR, Sanders DR, Raanan MG. Small incisions to control astigmatism during cataract surgery. J Cataract Refract Surg 1989; 15:78 – 84 7. Koch DD, Lindstrom RL. Controlling astigmatism in cataract surgery. Semin Ophthalmol 1992; 7:224 –233 8. Kohnen T, Koch DD. Methods to control astigmatism in cataract surgery. Curr Opin Ophthalmol 1996; 7(1): 75– 80 9. Mu¨ ller-Jensen K, Buchholz A, Barlinn B. Stability of astigmatism over 3 years after corneal stretch incision. J Refract Surg 1998; 14:455– 459 10. Mu¨ ller-Jensen K, Schuler M. Astigmatismus reduktion durch 4 mm langen nahtfreien kornealen starschnitt (stretch-Inzision) mit Phakoemulsifikation by 4 mm und 5 mm PMMA-Linsen-Implantation. Klin Monatsbl Augenheilkd 1998; 212:428 – 432 11. Jaffe NS, Jaffe MS, Jaffe GF. Cataract Surgery and Its Complications, 5th ed. St Louis, MO, CV Mosby, 1990; 109 –127 12. Oshika T, Nagahara K, Yaguchi S, et al. Three year prospective, randomized evaluation of intraocular lens implantation through 3.2 and 5.5 mm incisions. J Cataract Refract Surg 1998; 24:509 –514 13. Olson RJ, Crandall AS. Prospective randomized comparison of phacoemulsification cataract surgery with a 3.2-mm vs a 5.5-mm sutureless incision. Am J Ophthalmol 1998; 125:612– 620 14. Levy JH, Pisacano AM, Chadwick K. Astigmatic changes after cataract surgery with 5.1 mm and 3.5 mm sutureless incisions. J Cataract Refract Surg 1994; 20:630 – 633 15. Hayashi K, Hayashi H, Nakao F, Hayashi F. The correlation between incision size and corneal shape changes in sutureless cataract surgery. Ophthalmology 1995; 102: 550 –556 16. Hayashi K, Nakao F, Hayashi F. Corneal topographic analysis of superolateral incision cataract surgery. J Cataract Refract Surg 1994; 20:392–399
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17. Pfleger T, Skorpik C, Menapace R, et al. Long-term course of induced astigmatism after clear corneal incision cataract surgery. J Cataract Refract Surg 1996; 22:72–77 18. Naylor EJ. Astigmatic difference in refractive errors. Br J Ophthalmol 1968; 52:422– 425 19. Jaffe NS, Clayman HM. The pathophysiology of corneal astigmatism after cataract extraction. Trans Am Acad Ophthalmol Otolaryngol 1975; 79:OP615–OP630 20. Cravy TV. Calculation of the change in corneal astigmatism following cataract extraction. Ophthalmic Surg 1979; 10(1):38 – 49 21. Naeser K. Conversion of keratometer readings to polar values. J Cataract Refract Surg 1990; 16:741–745 22. Holladay JT, Cravy TV, Koch DD. Calculating the surgically induced refractive change following ocular surgery. J Cataract Refract Surg 1992; 18:429 – 443 23. Olsen T, Dam-Johansen M, Bek T, Hjortdal JØ. Evaluating surgically induced astigmatism by Fourier analysis of corneal topography data. J Cataract Refract Surg 1996; 22:318 –323 24. Wirbelauer C, Anders N, Pham DT, Wollensak J. Effect of incision location on preoperative oblique astigmatism after scleral tunnel incision. J Cataract Refract Surg 1997; 23:365–371 25. Roman SJ, Auclin FX, Chong-Sit DA, Ullern J. Surgically induced astigmatism with superior and temporal
incisions in cases of with-the-rule preoperative astigmatism. J Cataract Refract Surg 1998; 24:1636 –1641 26. Kohnen T, Mann PM, Husain SE, et al. Corneal topographic changes and induced astigmatism resulting from superior and temporal scleral pocket incisions. Ophthalmic Surg Lasers 1996; 27:263–269 27. Akura J, Kaneda S, Hatta S, Matsuura K. Controlling astigmatism in cataract surgery requiring relatively large self-sealing incisions. J Cataract Refract Surg 2000; 26: 1650 –1659 28. Lever J, Dahan E. Opposite clear corneal incisions to correct pre-existing astigmatism in cataract surgery. J Cataract Refract Surg 2000; 26:803– 805
From the Department of Ophthalmology, School of Medicine, University of Maryland at Baltimore, Baltimore, Maryland, USA (Matsumoto); Department of Ophthalmology, Koshigaya Hospital, School of Medicine, Dokkyo University, Saitama (Matsumoto, Chikuda), Hara Eye Hospital, Utsunomiya (Hara), and Department of Ophthalmology, School of Medicine, Dokkyo University, Tochigi (Chiba), Japan. Presented in part at the Symposium on Cataract, IOL and Refractive Surgery, Seattle, Washington, USA, April 1999. None of the authors has a financial or proprietary interest in any material or method mentioned.
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T
he popularity of cataract surgery as a refractive procedure has been increasing. Regardless of the preoperative refraction, obtaining an astigmatism-free eye Accepted for publication February 19, 2001. Reprint requests to Yukihiro Matsumoto, MD, Room 5-65, MSTF, 10 South Pine Street, Baltimore, Maryland 21201, USA. E-mail: [email protected]. © 2001 ASCRS and ESCRS Published by Elsevier Science Inc.
postoperatively is the objective.1–3 Many reports of incision types and surgically induced astigmatism (SIA) have appeared in the literature. Incision types include the 12 o’clock, between 9 and 12 o’clock (BENT),4 temporal,5 and steep meridian.6 –10 Some studies of incision site address the presence and type of suture,11 use of a wider incision,7 and use of a narrower incision.5,6,8,12,13 In several studies, to reduce 0886-3350/01/$–see front matter PII S0886-3350(01)00876-8
INCISION SITES TO LIMIT ASTIGMATISM AFTER CATARACT SURGERY
the SIA,8,14,15 the incision was shortened to 3.2 mm.12,13,15–17 Reports of 3.2 mm incisions indicate that the 12 o’clock,12,13 BENT,15,16 temporal,17 and steep meridian incision should be used. In addition, some authors describe a corneoscleral incision,12,13 a corneal incision,17 or a method of calculating SIA.18 –23 To determine the effective incision site and direction, it is necessary to eliminate the effect of suturing, incision width, and operative method and to choose eyes with certain preoperative corneal conditions.24,25 These studies compared groups of patients differently; that is, by incision site, incision width, surgical method, suture method, presence of a suture, or incision type. Thus, the authors reached different conclusions that were not always consistent with the results in other studies. To clarify the relation between incisions and SIA, we studied the effect of a 3.2 mm incision without sutures placed at the limbus in patients with no preoperative astigmatism and in another group with no postoperative astigmatism. In the former group, we evaluated the effect of incision type on postoperative corneal changes. In the latter, we retrospectively evaluated the preoperative corneal condition and the incision type and site.
Patients and Methods Patients had extraction of a senile cataract at the Hara Eye Hospital from November 1996 to March 1998. The mean age of the patients was 69.0 years ⫾ 7.4 (SD) (range 47 to 90 years).
One surgeon (T.H.) performed all surgeries using the same technique. Anesthesia was induced using tetracaine 0.5% eyedrops. The cataract was removed by phacoemulsification (Cavitron 20000, Alcon Japan Ltd.) through a 3.2 mm incision made with a diamond blade at the corneal limbus. The incision was not sutured. A 3-piece acrylic intraocular lens (Alcon Japan Ltd.) with a 5.5 mm optic and an overall length of 13.0 mm was implanted in the capsular bag with the loops in a horizontal position. An astigmatism-free eye was defined as one in which the difference between the steep simulated K-reading and flat simulated K-reading and the difference between the steepest corneal curvature (refractive power) and the flattest corneal curvature were within ⫾0.5 diopter (D). The corneal curvature was obtained using numeric analysis in 3.0 mm increments from the center measured by a corneal shape analyzer (CAS model 2, EyeSys Technologies Inc.) In addition, a concentric pattern with good symmetry was observed by corneal topographic analysis (Figure 1). The presence of astigmatism was measured preoperatively and 6 months postoperatively. The astigmatism changes were presented as the difference between the steep simulated K-reading and the flat simulated K-reading. The patients were divided into 2 groups. Group 1 comprised 98 eyes (80 patients) that were free of corneal astigmatism preoperatively. The mean age in Group 1 was 70.1 ⫾ 8.4 years (range 47 to 90 years). To determine which type of incision induced postoperative astigmatism less frequently, a BENT incision (placed around
Figure 1. (Matsumoto) An astigmatism-free cornea. Left: Color map analysis. Right: Numeric analysis. 1616
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Figure 2. (Matsumoto) Postoperative corneal changes resulting from the use of a BENT incision. Left: Astigmatism-free cornea preoperatively. Right: A BENT incision 6 months postoperatively in a case in which a 3.2 mm wide incision was placed at the 10:30 position on the corneal limbus. The changes in corneal shape from preoperatively were minimal.
10:30 o’clock in 40 eyes of 33 patients) or a 12 o’clock incision (58 eyes, 47 patients) was used. Group 2 comprised 72 eyes (62 patients) that were free of corneal astigmatism postoperatively. The mean age in Group 2 was 68.2 ⫾ 9.3 years (range 47 to 90 years). In Group 2, patients were placed into 1 of 2 subgroups based on the severity of the preoperative corneal astigmatism: less than 0.5 D (33 patients, 36 eyes) or 0.5 D and greater (29 patients, 36 eyes). Patients were also placed in subgroups according to incision type: at the steepest meridian (within 30 degrees around the incision site) or in the direction of the nonsteep meridian. Excluded were eyes with myopia of –10.0 D or higher, keratoconjunctival disease, glaucoma, or a history of intraocular surgery. Statistical analysis was by the chi-square test. The types of incisions and the results are shown in ascending order of frequency of SIA.
Results Figure 2 shows topography of postoperative corneal changes in an eye with a BENT incision. Figure 3 shows topography of postoperative corneal changes in an eye with an incision at the 12 o’clock position.
In Group 1, of the 40 eyes (29 right, 11 left) with a BENT incision, 23 (57.5%; 18 right, 5 left) remained astigmatism free postoperatively. Ten of 58 eyes (17.2%) with a 12 o’clock incision remained astigmatism free. The difference was significant (P ⬍ .0001). The percentage of eyes in which 1.0 D or more of corneal astigmatism was induced was significantly higher in the 12 o’clock incision group (17 eyes, 29.3%) than in the BENT incision group (1 eye, 2.5%) (P ⬍ .001). When the 12 o’clock incision was used, a maximum of 1.78 D of astigmatism remained between 41 and 131 degrees. In Group 2, of the 36 eyes with preoperative astigmatism of less than 0.5 D, the incision was at the steepest meridian in 18 eyes (BENT in 11, 12 o’clock in 4, temporal in 2, and other in 1) and at the nonsteep meridian in 18 eyes (BENT in 12 and 12 o’clock in 6). In eyes with preoperative astigmatism of 0.5 D or greater (n ⫽ 36), the incision was at the steepest meridian in 29 eyes (BENT in 6, 12 o’clock in 16, temporal in 5, and other in 2) and at the nonsteep meridian in 7 eyes (BENT in 2, 12 o’clock in 3, and temporal in 2). The incision was at the steepest meridian in 18 of 36 eyes (50.0%) with a preoperative astigmatism less than 0.5 D and in 29 of 36 eyes (80.6%) with a preoperative astig-
Figure 3. (Matsumoto) Postoperative corneal changes caused by an incision placed at the 12 o’clock position. Left: Astigmatism-free cornea preoperatively. Right: A 12 o’clock incision 6 months postoperatively in a case in which a 3.2 mm wide incision was placed at the 12 o’clock position on the corneal limbus. The wound-related flattening and steepening to the upper central cornea persisted.
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matism of 0.5 D or higher (P ⬍ .01). No eye with a preoperative astigmatism of 1.2 D or greater was astigmatism free postoperatively, even when the incision was at the steepest meridian.
Discussion Most studies of SIA make comparisons based on different factors including the suturing method, presence of a suture, incision type, type of operation, and incision width. Because of the different parameters, the result do not agree among studies. One reason is the complicated calculations required for correction to make a comparison because the incisions are made in eyes with various degrees of preoperative astigmatism.18 –23 In our study, the patient selection process enabled us to observe the changes caused by the incisions without performing complicated calculations. To the best of our knowledge, no reported study has used this method. Postoperative astigmatism developed less frequently in the patients with a BENT (10:30 o’clock) incision than in those with a 12 o’clock incision. In addition, the BENT incision had less of an effect on the central and paracentral corneal zones than the 12 o’clock incision in eyes with a preoperative astigmatism of less than 0.5 D. Compared with the 12 o’clock incision, these results were consistent with those in previous reports.4,9,10,16,25–27 However, although an incision at the steepest meridian effectively minimized the chances of inducing and relieving astigmatism, there seemed to be a limitation.11 In conclusion, to avoid postoperative astigmatism, we recommend making the incision on the steepest meridian in eyes with a preoperative astigmatism of 0.5 D or higher. However, astigmatism higher than 1.2 D cannot be eliminated by a 3.2 mm wide incision made at the corneal limbus and a wider incision27 or an additional incision2,3,28 is required. To avoid postoperative astigmatism in eyes with a preoperative astigmatism of 0.5 D or lower, we recommend placing the incision at approximately 10:30 o’clock rather than at 12 o’clock in cases in which a 3.2 mm wide incision is placed at the limbus. Although a large number of studies in the literature report incisions and postoperative astigmatism data, the present study provides simpler and clearer results based on proper patient selection. 1618
References 1. Nordan LT, Lusby FW. Refractive aspects of cataract surgery. Curr Opin Ophthalmol 1995; 6(1):36 – 40 2. Kershner RM. Keratolenticuloplasty: arcuate keratotomy for cataract surgery and astigmatism. J Cataract Refract Surg 1995; 21:274 –277 3. Kershner RM. Clear corneal cataract surgery and the correction of myopia, hyperopia, and astigmatism. Ophthalmology 1997; 104:381–389 4. Kawano K. Modified corneoscleral incision to reduce postoperative astigmatism after 6 mm diameter intraocular lens implantation. J Cataract Refract Surg 1993; 19: 387–398 5. Kohnen T, Dick B, Jacobi KW. Comparison of the induced astigmatism after temporal clear corneal tunnel incisions of different sizes. J Cataract Refract Surg 1995; 21:417– 424 6. Neumann AC, McCarty GR, Sanders DR, Raanan MG. Small incisions to control astigmatism during cataract surgery. J Cataract Refract Surg 1989; 15:78 – 84 7. Koch DD, Lindstrom RL. Controlling astigmatism in cataract surgery. Semin Ophthalmol 1992; 7:224 –233 8. Kohnen T, Koch DD. Methods to control astigmatism in cataract surgery. Curr Opin Ophthalmol 1996; 7(1): 75– 80 9. Mu¨ ller-Jensen K, Buchholz A, Barlinn B. Stability of astigmatism over 3 years after corneal stretch incision. J Refract Surg 1998; 14:455– 459 10. Mu¨ ller-Jensen K, Schuler M. Astigmatismus reduktion durch 4 mm langen nahtfreien kornealen starschnitt (stretch-Inzision) mit Phakoemulsifikation by 4 mm und 5 mm PMMA-Linsen-Implantation. Klin Monatsbl Augenheilkd 1998; 212:428 – 432 11. Jaffe NS, Jaffe MS, Jaffe GF. Cataract Surgery and Its Complications, 5th ed. St Louis, MO, CV Mosby, 1990; 109 –127 12. Oshika T, Nagahara K, Yaguchi S, et al. Three year prospective, randomized evaluation of intraocular lens implantation through 3.2 and 5.5 mm incisions. J Cataract Refract Surg 1998; 24:509 –514 13. Olson RJ, Crandall AS. Prospective randomized comparison of phacoemulsification cataract surgery with a 3.2-mm vs a 5.5-mm sutureless incision. Am J Ophthalmol 1998; 125:612– 620 14. Levy JH, Pisacano AM, Chadwick K. Astigmatic changes after cataract surgery with 5.1 mm and 3.5 mm sutureless incisions. J Cataract Refract Surg 1994; 20:630 – 633 15. Hayashi K, Hayashi H, Nakao F, Hayashi F. The correlation between incision size and corneal shape changes in sutureless cataract surgery. Ophthalmology 1995; 102: 550 –556 16. Hayashi K, Nakao F, Hayashi F. Corneal topographic analysis of superolateral incision cataract surgery. J Cataract Refract Surg 1994; 20:392–399
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17. Pfleger T, Skorpik C, Menapace R, et al. Long-term course of induced astigmatism after clear corneal incision cataract surgery. J Cataract Refract Surg 1996; 22:72–77 18. Naylor EJ. Astigmatic difference in refractive errors. Br J Ophthalmol 1968; 52:422– 425 19. Jaffe NS, Clayman HM. The pathophysiology of corneal astigmatism after cataract extraction. Trans Am Acad Ophthalmol Otolaryngol 1975; 79:OP615–OP630 20. Cravy TV. Calculation of the change in corneal astigmatism following cataract extraction. Ophthalmic Surg 1979; 10(1):38 – 49 21. Naeser K. Conversion of keratometer readings to polar values. J Cataract Refract Surg 1990; 16:741–745 22. Holladay JT, Cravy TV, Koch DD. Calculating the surgically induced refractive change following ocular surgery. J Cataract Refract Surg 1992; 18:429 – 443 23. Olsen T, Dam-Johansen M, Bek T, Hjortdal JØ. Evaluating surgically induced astigmatism by Fourier analysis of corneal topography data. J Cataract Refract Surg 1996; 22:318 –323 24. Wirbelauer C, Anders N, Pham DT, Wollensak J. Effect of incision location on preoperative oblique astigmatism after scleral tunnel incision. J Cataract Refract Surg 1997; 23:365–371 25. Roman SJ, Auclin FX, Chong-Sit DA, Ullern J. Surgically induced astigmatism with superior and temporal
incisions in cases of with-the-rule preoperative astigmatism. J Cataract Refract Surg 1998; 24:1636 –1641 26. Kohnen T, Mann PM, Husain SE, et al. Corneal topographic changes and induced astigmatism resulting from superior and temporal scleral pocket incisions. Ophthalmic Surg Lasers 1996; 27:263–269 27. Akura J, Kaneda S, Hatta S, Matsuura K. Controlling astigmatism in cataract surgery requiring relatively large self-sealing incisions. J Cataract Refract Surg 2000; 26: 1650 –1659 28. Lever J, Dahan E. Opposite clear corneal incisions to correct pre-existing astigmatism in cataract surgery. J Cataract Refract Surg 2000; 26:803– 805
From the Department of Ophthalmology, School of Medicine, University of Maryland at Baltimore, Baltimore, Maryland, USA (Matsumoto); Department of Ophthalmology, Koshigaya Hospital, School of Medicine, Dokkyo University, Saitama (Matsumoto, Chikuda), Hara Eye Hospital, Utsunomiya (Hara), and Department of Ophthalmology, School of Medicine, Dokkyo University, Tochigi (Chiba), Japan. Presented in part at the Symposium on Cataract, IOL and Refractive Surgery, Seattle, Washington, USA, April 1999. None of the authors has a financial or proprietary interest in any material or method mentioned.
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