Peripheral corneal relaxing incisions combined with cataract surgery1

Peripheral corneal relaxing incisions combined with cataract surgery Li Wang, MD, Manjula Misra, MD, Douglas D. Koch, MD 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. J Cataract Refract Surg 2003; 29:712–722 © 2003 ASCRS and ESCRS

T

he advent of phacoemulsification, foldable intraocular lenses (IOLs), and improved incision designs has decreased the incidence and amount of surgically induced astigmatism (SIA) in cataract patients. However, approximately 15% to 20% of cataract patients have more than 1.5 diopters (D) of keratometric astigmatism, refractive astigmatism, or both.1,2 Interest in reducing preexisting astigmatism simultaneously with cataract surgery has grown in recent years. Available options include a clear corneal cataract incision along the steep meridian,3–5 astigmatic keratotomy (AK),6 –13 Accepted for publication September 19, 2002. Reprint requests to Douglas D. Koch, MD, Cullen Eye Institute, Baylor College of Medicine, Department of Ophthalmology, 6565 Fannin, NC205, Houston, Texas 77030, USA. © 2003 ASCRS and ESCRS Published by Elsevier Science Inc.

toric IOL implantation,14 –18 opposite clear corneal incisions,19 and limbal relaxing incisions (LRIs) or peripheral corneal relaxing incisions (PCRIs).20 –22 In a previous study,21 we evaluated the effectiveness of PCRIs in 12 eyes of 11 patients. Preliminary results show that PCRIs are a practical, simple approach to correcting astigmatism during cataract surgery. In this study, we analyzed the effectiveness of PCRIs in a larger group of patients. An improved nomogram is proposed.

Patients and Methods The records of all eyes of all patients who had combined clear corneal phacoemulsification and PCRIs between October 1996 and December 2001 were retrospectively reviewed. The criteria for performing PCRIs were preexisting with-therule (WTR) keratometric astigmatism of ⱖ0.75 D or preex0886-3350/03/$–see front matter doi:10.1016/S0884-3350(02)01838-2

CORNEAL RELAXING INCISIONS WITH CATARACT SURGERY

isting against-the-rule (ATR) keratometric astigmatism of ⱖ1.00 D. Exclusion criteria were a follow-up of less than 1 month and preexisting irregular astigmatism as determined by irregular keratometric rings. One hundred fifteen eyes of 94 patients met the study criteria. Phacoemulsification and foldable IOL implantation were performed through a 3.2 to 3.5 mm temporal clear corneal incision. The clear corneal incision was placed along the 180-degree meridian in right eyes and the 30-degree meridian in left eyes. The PCRIs were done at the conclusion of the cataract procedure after the IOL was implanted. The length and number of PCRIs were decided according to a nomogram based on age and preoperative corneal astigmatism measured by keratometry (Bausch & Lomb, Inc.). The PCRIs were made just inside the limbal vessels with a guarded diamond knife set at a depth of 600 ␮m and were centered along the steep corneal meridian. The location of the steep meridian was determined by keratometry. In eyes receiving paired incisions along the horizontal meridian, the PCRI incorporated the clear corneal incision. To minimize the effect of eye rotation on surgical accuracy, a drawing noting the location of prominent landmarks on the conjunctiva or limbus relative to the 3, 6, 9, or 12 o’clock semimeridians was made for each patient. If a clear landmark was not evident preoperatively, the 6 o’clock semimeridian was marked while the patient was sitting upright on the surgical gurney. In some patients, the landmarks or dye was not visible intraoperatively, and the 6 o’clock and 12 o’clock positions were marked by the surgeon while sitting at the head of the gurney viewing the eye without the use of the microscope. All procedures were done by 1 surgeon (D.D.K.). A control group was included to explore the effect of a 3.2 to 3.5 mm temporal clear corneal cataract incision on the change in keratometric astigmatism. This group consisted of 26 eyes of 19 patients (mean age 75 years ⫾ 8 [SD]) with preoperative keratometric WTR or ATR astigmatism ranging from 0.25 to 1.13 D. Postoperative medications consisted of prenisolone acetate and ketorolac 0.5% 4 times a day for 1 week, 3 times a day for 1 week, 2 times a day for 1 week, and 1 time a day for 1 week. Patients also were instructed to use ofloxacin 4 times a day for the first week postoperatively. Postoperative keratometric astigmatism was measured at 1 day and 1 and 4 months. Patients were divided into subgroups according to the preexisting keratometric astigmatism (WTR or ATR) and the length and number of PCRIs. Methods of analyses included the following: 1. Mean arithmetic changes in keratometric astigmatism. 2. Determination of with-the-wound (WTW) and againstthe-wound (ATW) changes using the Holladay-CravyKoch (HCK) formula23; for these calculations, the steep corneal meridian at which the PCRI(s) was placed was used as the reference (ie, the “wound”).

3. Analysis of aggregate keratometric astigmatism.24 4. Calculation of the coefficient of adjustment (CA) and index of success (IOS) as described by Alpins; the CA was calculated by dividing the target induced astigmatism vector by the vector for SIA. Its value was preferably 1.0. The IOS was calculated by dividing the difference vector by the vector for target induced astigmatism. It is a relative measure of success and is preferably zero.25 5. Complications including overcorrection, which was defined as postoperative astigmatism ⱖ0.50 D along a meridian 60 to 120 degrees from the original steep meridian. An analysis of covariance (ANCOVA) and multiple regression were used to evaluate the effects of sex, eye (right or left), age, and magnitude of preoperative keratometric astigmatism on the changes in WTW–ATW in each group. A 1-factor, within-subjects analysis of variance (ANOVA) and a between-subjects ANOVA were performed to compare the differences between the averages of the preoperative and postoperative values and the averages of the values in the control group and treatment group, respectively. The McNemar test was used to compare the differences in frequency in different groups. A probability of less than 5% was considered statistically significant.

Results Control Group In 11 control eyes with preexisting WTR astigmatism, keratometric astigmatism 4 months postoperatively was significantly increased by a mean of 0.63 ⫾ 0.23 D in right eyes (P ⫽ .01) and 0.04 ⫾ 0.73 D in left eyes. Combining right and left eyes, astigmatism increased by a mean of 0.26 ⫾ 0.65 D. In the 15 control eyes with ATR astigmatism, the mean keratometric astigmatism decreased by 0.27 ⫾ 0.54 D in right eyes and 0.02 ⫾ 0.39 D in left eyes. The total astigmatism in both right and left eyes decreased by 0.15 ⫾ 0.47 D. At 4 months, the mean WTW–ATW change was ⫺0.31 ⫾ 0.39 D in right eyes along the 180-degree meridian (12 eyes). In left eyes (n ⫽ 14), the mean WTW–ATW change was ⫺0.05 ⫾ 0.53 D along the 30-degree meridian and ⫺0.07 ⫾ 0.65 D along the 180-degree meridian (P ⬎ .05 compared with right eyes). The mean WTW–ATW change in the whole group was ⫺0.17 ⫾ 0.48 D. Treatment Groups In eyes having PCRIs, the mean age of the patients was 69 ⫾ 12 years (P ⫽ .04 compared with control group) and the preexisting WTR or ATR astigmatism

J CATARACT REFRACT SURG—VOL 29, APRIL 2003

713

CORNEAL RELAXING INCISIONS WITH CATARACT SURGERY

ranged from 0.75 to 3.75 D. These patients were divided into subgroups according to the preexisting WTR or ATR astigmatism and the length and number of PCRIs created (Table 1). Mean arithmetic changes in keratometric astigmatism. In eyes with preexisting WTR astigmatism (Tables 2 and 3), the mean keratometric astigmatism was reduced by 0.44 D 1 month postoperatively in the group with single 6.0 mm PCRIs (P ⬍.05); the percentage of eyes with keratometric astigmatism of 1.00 D or less increased from 25% preoperatively to 69% at 1 month (P ⬍ .001). In 18 eyes followed for 4 months, the mean preoperative astigmatism of 1.38 D was reduced to 1.11 D and the percentage of eyes with keratometric astigmatism ⱕ1.00 D increased from 17% preoperatively to 50% (P ⬍ .05). In eyes with WTR astigmatism, paired 6.0 PCRIs reduced preoperative keratometric astigmatism by 0.76 D and 0.91 D at 1 and 4 months, respectively (both P ⬍ .05). The percentage of eyes with keratometric astigmatism ⱕ1.00 D increased from 0% preoperatively to 44% at 4 months (P ⬍ .05). The reductions in astigmatism at 4 months in both the single 6.0 mm and paired 6.0 mm PRCI groups with WTR astigmatism were significantly different from the increase in astigmatism in the control group (P ⬍ .05). In 19 eyes with preexisting ATR astigmatism that received single 4.5 mm PCRIs (Tables 4 and 5), the mean keratometric astigmatism was reduced by 0.85 D at 1 month and by 1.53 D at 4 months (both P ⬍ .05). In 18 eyes followed for 1 month, the percentage with keratometric astigmatism ⱕ1.00 D increased from 17% preoperatively to 83% (P ⬍ .001) and in 4 eyes followed for 4 months, from 0% to 75%. Table 1. Demographic summary of subgroups that received PCRIs. Preop Keratometric Astigmatism

PCRIs

Eyes

Mean Age (Y) ⴞ SD

WTR

Single 6.0 mm

38

66 ⫾ 13

Paired 6.0 mm

42

64 ⫾ 12

Single 4.5 mm

19

73 ⫾ 5

ATR

Single 6.0 mm

6

77 ⫾ 8

Paired 6.0 mm

7

80 ⫾ 6

WTR ⫽ with the rule; ATR ⫽ against the rule

714

Table 2. Mean keratometric astigmatism over time in the WTR groups.

Eyes

Mean K Astig (D)

Range (D)

Preop

38

1.42 ⫾ 0.60

0.75–3.25

1 day

38

0.95 ⫾ 0.79*

0.00–3.00

1 month

36

0.98 ⫾ 0.58*

0.25–2.50

4 months

18

1.11 ⫾ 0.74

0.00–2.75

42

2.09 ⫾ 0.62

1.12–3.75

Group Single 6.0 mm

Paired 6.0 mm Preop 1 day

39

1.47 ⫾ 0.89*

0.00–3.63

1 month

38

1.33 ⫾ 0.71*

0.00–3.13

4 months

25

1.18 ⫾ 0.48*

0.38–2.00

Means ⫾ SD K Astig ⫽ keratometric astigmatism *Statistically significant compared with preoperative keratometric astigmatism (P ⬍ .05)

In 6 eyes with ATR astigmatism that received single 6.0 mm PCRIs, the mean keratometric astigmatism was reduced by 0.61 D at 1 month and by 1.30 D (P ⬍ .05) at 4 months. In 4 eyes followed for 4 months, the percentage with keratometric astigmatism ⱕ1.00 D increased from 0% preoperatively to 75%. In 7 eyes with ATR astigmatism that received paired 6.0 mm PCRIs, the mean keratometric astigmatism significantly decreased at 1 and 4 months (both P ⬍ .05). In 6 eyes followed for 4 months, the percentage with keratometric astigmatism ⱕ1.00 D increased from 0% preoperatively to 67%. The reductions in astigmatism at 4 months in the groups treated by single 4.5 mm, single 6.0 mm, and paired 6.0 mm PRCIs were significantly greater than the decrease in astigmatism in the control group (P ⬍ .05). Changes in WTW and ATW astigmatism by the HCK formula. In patients with preexisting WTR keratometric astigmatism (Table 6), single 6.0 mm PCRIs induced WTW–ATW changes of ⫺0.78 D and ⫺0.55 D at 1 month and 4 months, respectively, indicating net flattening along the vertical (steeper) meridian. At 4 months, the mean WTW–ATW change was – 0.63 D in right eyes and ⫺0.41 D in left eyes. An ANCOVA revealed that the WTW–ATW values decreased with increasing age—F1,13 ⫽ 25.31 (P ⬍ .001)—and with increasing magnitude of preoperative astigmatism—

J CATARACT REFRACT SURG—VOL 29, APRIL 2003

CORNEAL RELAXING INCISIONS WITH CATARACT SURGERY

Table 3. Distribution of keratometric astigmatism as percentage of eyes preoperatively and 1 and 4 months postoperatively in the WTR groups. Single 6.0 mm

Paired 6.0 mm

Preop (n ⴝ 36)

1 Month (n ⴝ 36)

Preop (n ⴝ 18)

4 Months (n ⴝ 18)

Preop (n ⴝ 38)

1 Month (n ⴝ 38)

ⱕ0.5

0

22

0

22

0

11

0

12

ⱕ1.0

25

69

17

50

0

39

0

44

ⱕ1.5

72

89

78

78

16

66

24

80

ⱕ2.0

86

92

89

89

55

84

60

100

ⱕ3.0

97

100

94

100

95

97

100

—

Diopters

Table 4. Mean keratometric astigmatism over time in the ATR groups.

Eyes

Mean K Astig (D)

Range (D)

Preop

19

1.76 ⫾ 0.64

1.00–3.13

1 day

17

0.93 ⫾ 0.85*

0.00–3.00

1 month

18

0.90 ⫾ 0.92*

0.00–3.25

4 months

4

0.44 ⫾ 0.80*

0.00–1.63

Preop

6

2.11 ⫾ 0.58

1.50–2.88

1 day

6

2.11 ⫾ 1.99

0.50–6.00

1 month

6

1.50 ⫾ 0.55

0.75–2.25

4 months

4

0.81 ⫾ 0.55*

0.25–1.50

Group Single 4.5 mm

Single 6.0 mm

Paired 6.0 mm Preop

7

2.30 ⫾ 0.57

1.75–3.50

1 day

7

1.52 ⫾ 1.26

0.37–3.75

1 month

6

0.93 ⫾ 0.39*

0.25–1.37

4 months

6

1.06 ⫾ 0.38*

0.62–1.63

Means ⫾ SD K Astig ⫽ keratometric astigmatism *Statistically significant compared with preoperative keratometric astigmatism (P ⬍ .05)

F1,13 ⫽ 4.958 (P ⫽ .044). Multiple regression for age and magnitude of preoperative astigmatism showed a multiple correlation coefficient (r value) of 0.806 (P ⬍ .001); the regression equation was predicted WTW– ATW ⫽ – 0.037 ⫻ (age) – 0.347 ⫻ (magnitude of preoperative astigmatism) ⫹ 2.287. In eyes with preexisting WTR astigmatism, paired 6.0 mm PCRIs induced WTW–ATW changes of

Preop (n ⴝ 25)

4 Months (n ⴝ 25)

⫺1.09 D and ⫺1.18 D at 1 month and 4 months, respectively. At 4 months, the mean WTW–ATW change was ⫺1.20 D in right eyes and ⫺1.15 D in left eyes. An ANCOVA revealed that the WTW–ATW values decreased with increasing age—F1,20 ⫽ 6.166 (P ⫽ .022)—and with increasing magnitude of preoperative astigmatism—F1,20 ⫽ 5.039 (P ⫽ .036). Multiple regression for age and magnitude of preoperative astigmatism showed an r value of 0.545 (P ⫽ .021); the regression equation was predicted WTW–ATW ⫽ ⫺0.031 ⫻ (age) – 0.573 ⫻ (magnitude of preoperative astigmatism) ⫹ 2.011. The WTW–ATW changes at 4 months in both groups were significantly different from the change in the control group (P ⬍ .05). There were no significant differences in WTW–ATW changes among 1-day, 1-month, and 4-month values. In patients with preexisting ATR keratometric astigmatism (Table 7), single 4.5 mm PCRIs induced WTW–ATW changes of ⫺1.20 D and ⫺2.18 D at 1 month and 4 months, respectively, indicating net flattening along the horizontal (steeper) meridian. At 4 months, the mean WTW–ATW change was ⫺1.86 D in right eyes and ⫺2.28 D in left eyes. There were no significant effects of age, sex, or magnitude of astigmatism on the WTW–ATW changes at 1 month. In patients with preexisting ATR keratometric astigmatism, single 6.0 mm PCRIs induced WTW– ATW changes of ⫺1.88 D and ⫺2.02 D at 1 month and 4 months, respectively, indicating net flattening along the horizontal (steeper) meridian. At 4 months, the mean WTW–ATW change was ⫺1.56 D in right eyes and ⫺2.17 D in left eyes.

J CATARACT REFRACT SURG—VOL 29, APRIL 2003

715

CORNEAL RELAXING INCISIONS WITH CATARACT SURGERY

Table 5. Distribution of keratometric astigmatism as percentage of eyes preoperatively and 1 and 4 months postoperatively in the ATR groups. Single 4.5 mm

Single 6.0 mm

Preop (n ⴝ 18)

1 Month (n ⴝ 18)

ⱕ0.5

0

44

0

75

0

0

ⱕ1.0

17

83

0

75

0

ⱕ1.5

50

83

25

75

17

Diopters

Preop (n ⴝ 4)

4 Months (n ⴝ 4)

Preop (n ⴝ 6)

1 Month (n ⴝ 6)

Paired 6.0 mm 4 Months (n ⴝ 4)

Preop (n ⴝ 6)

1 Month (n ⴝ 6)

Preop (n ⴝ 6)

0

50

0

17

0

0

17

0

75

0

50

0

67

67

25

100

0

100

0

83

Preop (n ⴝ 4)

4 Months (n ⴝ 6)

ⱕ2.0

72

83

75

100

67

83

50

—

50

—

50

100

ⱕ3.0

94

94

100

—

100

100

100

—

83

—

83

—

Table 6. The WTW and ATW change (Holladay-Cravy-Koch formula) along the peripheral corneal relaxing incision meridian at postoperative follow-ups in the WTR groups. Mean ⴞ SD (D) Group

Eyes

WTW

ATW

WTW–ATW

Single 6.0 mm 1 day

38

⫺0.68 ⫾ 0.80

0.22 ⫾ 0.61

⫺0.90 ⫾ 0.85

1 month

36

⫺0.51 ⫾ 0.51

0.28 ⫾ 0.58

⫺0.78 ⫾ 0.65

4 months

18

⫺0.20 ⫾ 0.47

0.33 ⫾ 0.58

⫺0.55 ⫾ 0.67

Paired 6.0 mm 1 day

39

⫺1.11 ⫾ 0.88

0.30 ⫾ 0.81

⫺1.41 ⫾ 1.17

1 month

38

⫺0.70 ⫾ 0.65

0.38 ⫾ 0.74

⫺1.09 ⫾ 0.99

4 months

25

⫺0.90 ⫾ 0.66

0.28 ⫾ 0.56

⫺1.18 ⫾ 0.91

WTW ⫽ with the wound; ATW ⫽ against the wound

In patients with preexisting ATR keratometric astigmatism, paired 6.0 mm PCRIs induced mean WTW–ATW changes of ⫺2.86 D and –2.72 D at 1 and 4 months, respectively. The mean WTW–ATW change was ⫺2.57 D in right eyes and ⫺2.80 D in left eyes at 4 months. The WTW–ATW change at 4 months in all groups was significantly different from the change in the control group (P ⬍ .05). There were no significant differences in WTW–ATW changes among 1-day, 1-month, and 4-month values. Analysis of aggregate keratometric astigmatism. In eyes with preexisting WTR astigmatism, single 6.0 mm PCRIs reduced the preoperative mean astigmatism of 1.37 ⫾ 0.57 D @ 90° to 0.99 ⫾ 0.63 D @ 89° at 4 months (Figure 1). Paired 6.0 mm PCRIs reduced the mean preoperative astigmatism of 1.94 ⫾ 0.61 D @ 88° to 0.80 ⫾ 0.66 D @ 87° at 4 months (Figure 2) 716

In eyes with preexisting ATR astigmatism, single 4.5 mm PCRIs reduced the mean preoperative astigmatism of 1.59 ⫾ 0.70 D @178° to 0.48 ⫾ 0.85 D @ 175° at 1 month (Figure 3). Single 6.0 mm PCRIs reduced the mean preoperative astigmatism of 2.15 ⫾ 0.71 D @ 178° to 0.54 ⫾ 0.61 D @ 141° at 4 months (Figure 4). Paired 6.0 mm PCRIs reduced the mean preoperative astigmatism of 2.20 ⫾ 0.72 D @ 1° to 0.78 ⫾ 0.62 D @ 131° at 4 months (Figure 5). All centroids of postoperative keratometric astigmatism moved toward the origin, indicating a reduction in preoperative keratometric astigmatism after PCRIs combined with cataract surgery. Mild undercorrection was observed in the WTR astigmatism group after single 6.0 mm PCRIs, and the axis changes in the postoperative centroid compared with preoperatively in the ATR groups after single 6.0 mm and paired 6.0 mm PCRIs indicated astigmatic axis shift in some eyes.

J CATARACT REFRACT SURG—VOL 29, APRIL 2003

CORNEAL RELAXING INCISIONS WITH CATARACT SURGERY

Table 7. The WTW and ATW change (Holladay-Cravy-Koch formula) along the peripheral corneal relaxing incision meridian at postoperative follow-ups in the ATR groups. Mean ⴞ SD (D) Group

Eyes

WTW

ATW

WTW–ATW

Single 4.5 mm 1 day

17

⫺0.96 ⫾ 0.76

0.34 ⫾ 0.58

⫺1.29 ⫾ 0.83

1 month

18

⫺0.75 ⫾ 0.63

0.45 ⫾ 0.54

⫺1.20 ⫾ 0.81

4 months

4

⫺1.32 ⫾ 0.47

0.85 ⫾ 0.83

⫺2.18 ⫾ 0.91

Single 6.0 mm 1 day

6

⫺0.83 ⫾ 2.13

1.50 ⫾ 1.05

⫺2.33 ⫾ 2.74

1 month

6

⫺0.93 ⫾ 0.85

0.95 ⫾ 0.61

⫺1.88 ⫾ 1.24

4 months

4

⫺0.35 ⫾ 0.52

1.66 ⫾ 1.05

⫺2.02 ⫾ 0.60

Paired 6.0 mm 1 day

7

⫺1.79 ⫾ 1.00

1.54 ⫾ 0.95

⫺3.33 ⫾ 1.32

1 month

6

⫺1.51 ⫾ 0.50

1.35 ⫾ 0.52

⫺2.86 ⫾ 0.57

4 months

6

⫺1.36 ⫾ 0.62

1.36 ⫾ 0.45

⫺2.72 ⫾ 0.61

WTW ⫽ with the wound; ATW ⫽ against the wound

Figure 1. (Wang) Aggregate vector analysis of keratometric astig-

Figure 2. (Wang) Aggregate vector analysis of keratometric astig-

matism preoperatively and 4 months postoperatively in corneas with WTR astigmatism treated with single 6.0 mm PCRIs. The black dots represent centroids or means, and the elliptical areas surrounding the centroids represent the standard deviation.

matism preoperatively and 4 months postoperatively in corneas with WTR astigmatism treated with paired 6.0 mm PCRIs. The black dots represent centroids or means, and the elliptical areas surrounding the centroids represent the standard deviation.

Coefficient of adjustment and IOS. In patients with preexisting WTR astigmatism, the mean CA and IOS was 2.17 and 0.82, respectively, after single 6.0 mm PCRIs and 2.23 and 0.60, respectively, after paired 6.0 mm PCRIs at 4 months (Table 8). The CA and IOS values indicate a net undercorrection in these eyes. In patients with preexisting ATR astigmatism, the mean CA and IOS was 1.63 and 0.49, respec-

tively, after single 4.5 mm PCRIs at 1 month; 1.14 and 0.39, respectively, after single 6.0 mm PCRIs at 4 months; and 0.83 and 0.47, respectively, after paired 6.0 mm PCRIs at 4 months (Table 9). A CA value less than 1 in eyes with paired 6.0 mm PCRIs indicates a mean overcorrection. Overcorrection and complications. In the WTR astigmatism groups with 4 months of follow-up, the

J CATARACT REFRACT SURG—VOL 29, APRIL 2003

717

CORNEAL RELAXING INCISIONS WITH CATARACT SURGERY

Figure 3. (Wang) Aggregate vector analysis of keratometric astig-

Figure 4. (Wang) Aggregate vector analysis of keratometric astig-

matism preoperatively and 1 month postoperatively in corneas with ATR astigmatism treated with single 4.5 mm PCRIs. The black dots represent centroids or means, and the elliptical areas surrounding the centroids represent the standard deviation.

matism preoperatively and 4 months postoperatively in corneas with ATR astigmatism treated with single 6.0 mm PCRIs. The black dots represent centroids or means, and the elliptical areas surrounding the centroids represent the standard deviation.

following overcorrections occurred: (1) single 6.0 mm PCRIs, 1 of 18 eyes overcorrected by 0.87 D; (2) paired 6.0 mm PCRIs, 4 of 25 eyes overcorrected by 0.50 to 0.63 D and 1 of 25, by 1.50 D. In the ATR astigmatism groups, the following overcorrections occurred: (1) single 4.5 mm PCRIs, 1 of 18 eyes followed for 1 month overcorrected by 0.75 D; (2) single 6.0 mm PCRIs, 1 of 4 eyes followed for 4 months overcorrected by 2.13 D; (3) paired 6.0 mm

PCRIs, 3 of 6 eyes followed for 4 months overcorrected by 0.62 to 1.00 D. The eye overcorrected by 2.00 D was in an 87-yearold woman with a corneal diameter of 10.5 mm and keratometric astigmatism of 2.00 @ 176 preoperatively. A single 6.0 mm PCRI was placed at the 175-degree meridian. Keratometric astigmatism was 6.37 @ 97 1 week postoperatively and regressed to 2.25 @ 90 at 1 month and 2.13 @ 87 at 21 months. Gape of the PCRIs occurred in 1 eye of a patient with Fuchs’ dystrophy who had penetrating keratoplasty (PKP) 10 weeks after cataract and PCRI surgery. The Table 8. Vector analysis using the Alpins method in the WTR groups. Mean ⴞ SD Group

Eyes

CA

IOS

1 day

38

1.59 ⫾ 1.02

0.71 ⫾ 0.56

1 month

36

1.97 ⫾ 2.00

0.72 ⫾ 0.41

4 months

18

2.17 ⫾ 1.43

0.82 ⫾ 0.46 0.74 ⫾ 0.47

Single 6.0 mm

Paired 6.0 mm

Figure 5. (Wang) Aggregate vector analysis of keratometric astig-

1 day

39

1.53 ⫾ 0.98

matism preoperatively and 4 months postoperatively in corneas with ATR astigmatism treated with paired 6.0 mm PCRIs. The black dots represent centroids or means, and the elliptical areas surrounding the centroids represent the standard deviation.

1 month

38

2.13 ⫾ 1.27

0.65 ⫾ 0.32

4 months

25

2.23 ⫾ 1.58

0.60 ⫾ 0.25

718

CA ⫽ coefficient of adjustment; IOS ⫽ index of success

J CATARACT REFRACT SURG—VOL 29, APRIL 2003

CORNEAL RELAXING INCISIONS WITH CATARACT SURGERY

Table 9. Vector analysis using the Alpins method in the ATR

Table 10. Current nomogram for PCRIs to correct keratometric

groups.

astigmatism during cataract surgery. Mean ⴞ SD

Group

Eyes

CA

IOS

Preop Astigmatism (D)

Age (Y)

Number

Length (Degrees)

⬍65

2

45

ⱖ65

1

45

⬍65

2

60

ⱖ65

2

45 (or 1 ⫻ 60)

⬍65

2

80

ⱖ65

2

60

1.00–1.25†

—

1

35

1.26–2.00

—

1

45

⬎2.00

—

2

45

WTR*

Single 4.5 mm 1 day

17

1.36 ⫾ 0.84

0.51 ⫾ 0.38

1 month

18

1.63 ⫾ 1.38

0.49 ⫾ 0.36

4 months

4

0.94 ⫾ 0.17

0.18 ⫾ 0.32

0.75–1.00

1.01–1.50

Single 6.0 mm 1 day

6

1.50 ⫾ 1.16

1.01 ⫾ 1.00

1 month

6

1.25 ⫾ 0.53

0.74 ⫾ 0.28

4 months

4

1.14 ⫾ 0.44

0.39 ⫾ 0.26

Paired 6.0 mm 1 day

7

0.72 ⫾ 0.22

0.65 ⫾ 0.48

1 month

6

0.84 ⫾ 0.18

0.40 ⫾ 0.18

4 months

6

0.83 ⫾ 0.17

0.47 ⫾ 0.19

CA ⫽ coefficient of adjustment; IOS ⫽ index of success

PCRIs were sutured with interrupted 10-0 nylon sutures, and no further complications occurred with the sutures still in place after 2 years of follow-up. No other eye had complications related to the placement of the PCRIs. New Nomogram These results were used to develop a nomogram based on age and preexisting keratometric astigmatism (Table 10).

Discussion There are several approaches for reducing preexisting astigmatism during cataract surgery. Perhaps the most basic is placement of the incision along the steep corneal meridian, taking advantage of wound-induced flattening.3–5 There are 2 major limitations of this approach. First, with small incisions, the WTW flattening is insufficient to correct existing astigmatism in excess of approximately 1.00 D.26 Second, centering the incision on certain meridians is technically difficult (eg, superonasal or inferotemporal in the left eye). Astigmatic keratotomy has been used to correct preexisting keratometric astigmatism during cataract sur-

⬎1.50

ATR/oblique*

WTR ⫽ with the rule; ATR ⫽ against the rule *Combined with temporal corneal incision † Especially if cataract incision is not directly centered on steep meridian

gery.6 –13 The AK incisions are placed within 3.0 to 3.5 mm of the center of the cornea, which increases the risk of inducing irregular astigmatism and postoperative glare. Torsional diplopia may be induced by meridional aniseikonia, which alters spatial sense.27 The results of AK may vary, and fluctuation in refraction may occur.28 Another incisional approach is the use of opposite clear corneal incisions.19 In this technique, 2 standard cataract incisions are made 180 degrees apart along the steep meridian. Lever and Dahan19 report that the mean astigmatism correction was 2.06 D with incisions ranging from 2.8 to 3.5 mm. However, the standard deviation for the mean astigmatism correction was not reported. Because the second incision enters the anterior chamber, this approach is more invasive than using PCRIs. Toric IOL implantation has recently become available as a means of correcting preexisting astigmatism.14 –18 This approach has the advantage of excellent optical quality, but postoperative rotation of the toric IOL is a main concern. Leyland and coauthors18 report that 18% of IOLs (4 of 22) rotated more than 30 degrees. Sun and coauthors17 report that 18% rotated between 20 degrees and 40 degrees and 7% had more than 40 degrees of rotation. Modifications of toric IOL de-

J CATARACT REFRACT SURG—VOL 29, APRIL 2003

719

CORNEAL RELAXING INCISIONS WITH CATARACT SURGERY

signs are needed to address this problem. An additional drawback to the use of toric IOLs is that cylindrical adds of only 2.00 D and 3.50 D are currently available, which correct 1.40 D and 2.30 D of astigmatism at the corneal plane, respectively. In light of the disadvantages described, LRIs or PCRIs seem to be excellent alternatives for reducing preexisting keratometric astigmatism at the time of cataract surgery.20 –22 A previous study of 12 eyes of 11 patients found that the reduction in keratometric astigmatism (HCK vector analysis) by combined LRIs was 1.47 D on average 1 month postoperatively; the mean WTW change at 1 month was ⫺0.70 D.21 Preoperative keratometric astigmatism was greater than 1.50 D in 83% of eyes compared with 25% postoperatively. There were no overcorrections or other complications. In the current retrospective study, we evaluated the effect of PCRIs in a large series of cases. Our results demonstrated that PCRIs significantly decreased keratometric astigmatism in patients with preexisting WTR or ATR astigmatism compared with the astigmatic changes in the control group. The percentage of eyes with keratometric astigmatism ⱕ1.00 D increased by 33% to 75% 4 months postoperatively. The incision length has been the main factor manipulated in controlling the degree of astigmatic correction. In this study, an ANCOVA showed no significant effects of sex and eye (right or left) on WTW–ATW changes, whereas older patients and eyes with higher preoperative WTR astigmatism had a greater response to the same length and number of PCRIs. We did not detect significant effects of age and magnitude of preoperative astigmatism in the ATR group with single 4.5 mm PCRIs. This might be the result of the smaller range of patient age in this group. (The standard deviation was 5 years compared to 13 years and 12 years in the 2 WTR groups.) It might also be because the postoperative follow-up was shorter (1 month). We found marked differences in the effect of vertical versus horizontal PCRIs. Four months postoperatively, the mean WTW–ATW change was ⫺0.55 D and ⫺1.18 D by vertical single 6.0 mm and paired 6.0 mm PCRIs, respectively, compared with a mean WTW– ATW change of ⫺2.02 D and ⫺2.72 D by horizontal single and paired 6.0 mm PCRIs, respectively. Part of this is the result of the presence of the cataract incision, which tended to induce WTR change, especially in right 720

eyes. However, one might expect less effect with incisions in the horizontal meridian because if they are made just inside the insertion of the conjunctival vessels, they will be located more peripherally than those made in the vertical meridian. Our data suggest, therefore, that the cornea responds differently to incisions in different meridians. Mu¨ ller-Jensen and coauthors22 report that temporal clear corneal incisions in a preoperative spherical control group induced a mean increase in astigmatism of 0.48 ⫾ 0.70 D. To counteract this, the authors added paired 6.0 mm LRIs (550 ␮m depth) and found a mean decrease in astigmatism of 0.08 ⫾ 0.52 D (P ⫽ .009) (HCK vector analysis). In the control group with preoperative WTR astigmatism, they observed an increase in astigmatism of 0.39 ⫾ 0.71 D and in the relaxing incision group (paired 8.0 mm LRIs), a decrease of 0.09 ⫾ 0.45 D at 6 months (P ⫽ .003). Our findings are consistent but showed a greater effect of PCRIs, perhaps because we made slightly deeper incisions (600 ␮m). We found that single 6.0 mm PCRIs reduced mean arithmetic astigmatism by 0.27 D and produced a mean WTW–ATW change of ⫺0.53 D 4 months postoperatively. Paired 6.0 mm PCRIs induced a mean WTW–ATW change of –1.18 D at 4 months. In our experience, paired 8.0 mm PCRIs produce an even greater effect. In our study, 2 eyes were overcorrected more than 1.00 D. In patients with preexisting WTR astigmatism, PCRIs corrected astigmatism effectively, with a tendency toward mild undercorrection in younger patients. Paired 6.0 mm PCRIs produced a greater effect in older patients with preoperative astigmatism of 1.50 D or less. In eyes with preexisting ATR astigmatism, single 6.0 mm and paired 6.0 mm PCRIs tended to overcorrect the astigmatism. Based on these findings, our nomogram has been modified with reduced number and/or length of PCRIs (Table 10). The eye overcorrected by 2.00 D had a corneal diameter of 10.5 mm, which might have contributed to the overcorrection because of the shorter distance between the PCRI and the center of the cornea and the longer arc length relative to the corneal circumference. As a result, we changed our new nomogram to measure the PCRI length by degrees rather than millimeters. The conversion from millimeters to degrees was calculated using a corneal diameter of 11.5 mm.

J CATARACT REFRACT SURG—VOL 29, APRIL 2003

CORNEAL RELAXING INCISIONS WITH CATARACT SURGERY

There were no ocular perforations in our series, suggesting a good safety profile for using a guarded diamond knife set at a depth of 600 ␮m when PCRIs are performed at the conclusion of cataract surgery. Also, the only problem with wound healing occurred in a patient with Fuchs’ dystrophy who had PKP; the wound gape in this eye was presumably a result of traction from the graft sutures. In our series, all PRCIs were placed at the conclusion of surgery. We did this because we had good success with this approach in our early cases and had developed our first nomogram based on the results in these eyes. An advantage of performing the incisions at the conclusion of surgery is that the incisions can be omitted if there is a need to enlarge or change the site of the cataract incision. An obvious disadvantage of performing incisions at the conclusion of surgery is that there might be greater variability in corneal thickness from intraoperative corneal swelling. In addition, there might be more variability in the intraocular pressure, which could affect the depth of the incisions. We presume that incisions placed early in the surgery might have a greater effect and pose a greater risk of corneal perforation, particularly in older eyes with thinner corneas in the region of the limbus. Advantages of PCRIs include technical ease, minimal instrument requirements, preservation of the optical qualities of the cornea with no complaints of postoperative glare and no apparent loss of vision, little or no postoperative discomfort, and infrequent overcorrections. Disadvantages include possible weakening of the integrity of the globe and moderate variability in accuracy, presumably resulting from variations in surgical technique and individual healing patterns. Also, our treatment tended to undercorrect most patients. A limitation of this study was that manual keratometry rather than computerized videokeratography was used for keratometric astigmatism measurement and only 1 keratometry reading was recorded at each visit. In conclusion, PCRIs are a practical, simple, effective method to reduce preexisting astigmatism during cataract surgery. We believe that more effective results can be expected under the guidance of our improved nomogram. The long-term effect of PCRIs should be investigated.

References 1. Hoffer KJ. Biometry of 7,500 cataractous eyes. Am J Ophthalmol 1980; 90:360 –368; correction, 890 2. Grabow HB. Intraocular correction of refractive errors. In: Kershner RM, ed, Refractive Keratotomy for Cataract Surgery and the Correction of Astigmatism. Thorofare, NJ, Slack, 1994; 79 –115 3. Koch D, Lindstrom RL. Controlling astigmatism in cataract surgery. Semin Ophthalmol 1992; 7:224 –233 4. Amigo A, Giebel AW, Muin˜ os JA. Astigmatic keratotomy effect of single-hinge, clear corneal incisions using various preincision lengths. J Cataract Refract Surg 1998; 24:765–771 5. Lyhne N, Hansen TE, Corydon L. Relationship between preoperative axis of astigmatism and postoperative astigmatic change after superior scleral incision phacoemulsification. J Cataract Refract Surg 1998; 24:935–939 6. Shepherd JR. Correction of preexisting astigmatism at the time of small incision cataract surgery. J Cataract Refract Surg 1989; 15:55–57 7. Davison JA. Transverse astigmatic keratotomy combined with phacoemulsification and intraocular lens implantation. J Cataract Refract Surg 1989; 15:38 –44 8. Osher RH. Paired transverse relaxing keratotomy: a combined technique for reducing astigmatism. J Cataract Refract Surg 1989; 15:32–37 9. Maloney WF, Sanders DR, Pearcy DE. Astigmatic keratotomy to correct preexisting astigmatism in cataract patients. J Cataract Refract Surg 1990; 16:297–304 10. Hall GW, Campion M, Sorenson CM, Monthofer S. Reduction of corneal astigmatism at cataract surgery. J Cataract Refract Surg 1991; 17:407–414 11. Lindstrom RL, Agapitos PJ, Koch DD. Cataract surgery and astigmatic keratotomy. Int Ophthalmol Clin 1994; 34(2):145–164 12. Kershner RM. Keratolenticuloplasty: arcuate keratotomy for cataract surgery and astigmatism. J Cataract Refract Surg 1995; 21:274 –277; correction, 488 13. Akura J, Matsuura K, Hatta S, et al. A new concept for the correction of astigmatism: full-arc, depth-dependent astigmatic keratotomy. Ophthalmology 2000; 107:95– 104 14. Shimizu K, Misawa A, Suzuki Y. Toric intraocular lenses: correcting astigmatism while controlling axis shift. J Cataract Refract Surg 1994; 20:523–526 15. Grabow HB. Early results with foldable toric IOL implantation. Eur J Implant Refract Surg 1994; 6:177–178 16. Ruhswurm I, Scholz U, Zehetmayer M, et al. Astigmatism correction with a foldable toric intraocular lens in cataract patients. J Cataract Refract Surg 2000; 26:1022– 1027 17. Sun X-Y, Vicary D, Montgomery P, Griffiths M. Toric intraocular lenses for correcting astigmatism in 130 eyes. Ophthalmology 2000; 107:1776 –1781

J CATARACT REFRACT SURG—VOL 29, APRIL 2003

721

CORNEAL RELAXING INCISIONS WITH CATARACT SURGERY

18. Leyland M, Zinicola E, Bloom P, Lee N. Prospective evaluation of a plate haptic toric intraocular lens. Eye 2001; 15:202–205 19. Lever J, Dahan E. Opposite clear corneal incisions to correct pre-existing astigmatism in cataract surgery. J Cataract Refract Surg 2000; 26:803–805 20. Gills JP. Cataract surgery with a single relaxing incision at the steep meridian [letter]. J Cataract Refract Surg 1994; 20:368 –369 21. Budak K, Friedman NJ, Koch DD. Limbal relaxing incisions with cataract surgery. J Cataract Refract Surg 1998; 24:503–508 22. Mu¨ ller-Jensen K, Fischer P, Slepe U. Limbal relaxing incisions to correct astigmatism in clear corneal cataract surgery. J Refract Surg 1999; 15:586 –589 23. Holladay JT, Cravy TV, Koch DD. Calculating the surgically induced refractive change following ocular surgery. J Cataract Refract Surg 1992; 18:429 –443 24. Holladay JT, Moran JR, Kezirian GM. Analysis of aggregate surgically induced refractive change, prediction er-

722

25.

26.

27. 28.

ror, and intraocular astigmatism. J Cataract Refract Surg 2001; 27:61–79 Alpins NA. A new method of analyzing vectors for changes in astigmatism. J Cataract Refract Surg 1993; 19:524 –533 Matsumoto Y, Hara T, Chiba K, Chikuda M. Optimal incision sites to obtain an astigmatism-free cornea after cataract surgery with a 3.2 mm sutureless incision. J Cataract Refract Surg 2001; 27:1615–1619 Guyton DL. Prescribing cylinders postoperatively. Year Book Ophthalmol 1985; 63– 66 Lindstrom RL, Lindquist TD. Surgical correction of postoperative astigmatism. Cornea 1988; 7:138 –148

From the Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. Supported in part by an unrestricted grant from Research to Prevent Blindness, New York, New York, USA. None of the authors has a financial or proprietary interest in any material or method mentioned.

J CATARACT REFRACT SURG—VOL 29, APRIL 2003