The role of sideport incision in astigmatism change after cataract surgery

Figures & data

Table 1 Distribution of the left and right eyes according to the distance between the tunnel and sideport incision

Distance between tunnel and sideport incisions	Left eyes (N=158)	Right eyes (N=150)
	N (%)	N (%)
Group A: <90°	43 (27.2)	54 (36.0)
Group B: 90°–110°	75 (47.5)	60 (40.0)
Group C: >110°	40 (25.3)	36 (24.0)

Table 2 Differences in preoperative and postoperative measures of corneal astigmatic power between the left and right eyes

	Left eyes		Right eyes		P*
	Mean	SD	Mean	SD
Preoperative astigmatism	1.04	0.86	1.12	0.78	0.359
Postoperative astigmatism (1 month)	1.31	0.92	1.23	0.77	0.408
Postoperative astigmatism (6 months)	1.14	0.90	1.20	0.80	0.545

Note:

* Student’s t-test.

Table 3 Changes in SIA measures according to distance between tunnel and sideport incision

	SIA		P**
	1st month†	6th month†
	Mean (SD)	Mean (SD)
Left eyes
Distance between the tunnel and sideport incisions
Group A: <90°	0.81 (0.53)	0.73 (0.52)	0.004
Group B: 100°–110°	0.64 (0.36)	0.62 (0.38)	0.218
Group C: >110°	0.79 (0.39)	0.72 (0.46)	0.020
P* (A versus B)	0.114	0.569
P* (A versus C)	1.000	1.000
P* (B versus C)	0.225	0.686
Right eyes
Distance between the tunnel and sideport incisions
Group A: <90°	0.8 (0.53)	0.72 (0.52)	0.005
Group B: 100°–110°	0.58 (0.36)	0.6 (0.37)	0.440
Group C: >110°	0.73 (0.36)	0.7 (0.31)	0.370
P* (A versus B)	0.020	0.353
P* (A versus C)	1.000	1.000
P* (B versus C)	0.290	0.761

Notes:

* Group effect;

** time effect.

† Changes at 1st and 6th postoperative months. Bold type indicates values with statistical significance.

Abbreviation: SIA, surgically induced astigmatism.

Table 4 Corneal astigmatic power measures preoperatively at the 1st and 6th month according to the distance between the tunnel and sideport incisions

	Preoperative corneal astigmatic power	Postoperative corneal astigmatic power		P**
		1st month	6th month
	Mean (SD)	Mean (SD)	Mean (SD)
Left eyes
Distance between tunnel and sideport incisions
Group A: <90°	1.01 (0.79)	1.30 (0.76)	1.05 (0.79)	0.004
Group B: 100°–110°	0.96 (0.72)	1.19 (0.84)	1.07 (0.74)	0.084
Group C: >110°	1.12 (0.99)	1.55 (1.17)	1.36 (1.22)	0.041
P* (A versus B)		1.000	1.000
P* (A versus C)		0.638	0.322
P* (B versus C)		0.138	0.301
Right eyes
Distance between tunnel and sideport incisions
Group A: <90°	1.13 (0.78)	1.24 (0.84)	1.15 (0.76)	0.179
Group B: 100°–110°	1.17 (0.81)	1.26 (0.78)	1.28 (0.84)	0.690
Group C: >110°	1.03 (0.72)	1.16 (0.69)	1.13 (0.83)	0.695
P* (A versus B)		1.000	1.000
P* (A versus C)		1.000	1.000
P* (B versus C)		1.000	1.000

Notes:

* P-value for group effect;

** P-value for time effect. Bold type indicates values with statistical significance.

Table 5 Changes over 0.5 D in astigmatic power and over 20° on the astigmatic axis according to the distance between the tunnel and sideport incisions, separately for the left and right eyes

	Change in astigmatic power/axis	Distance between tunnel and sideport incisions
		Group A: <90°	Group B: 90°–110°	Group C: >110°
		N (%)	N (%)	N (%)
Left eyes
Change over 0.5 D in astigmatic power (preoperative to the 1st month)	No	28 (65.1)	61 (81.3)	23 (57.5)
	Yes	15 (34.9)B	14 (18.7)A,C	17 (42.5)B
Change over 0.5 D in astigmatic power (preoperative to the 6th month)	No	43 (100.0)	70 (93.3)	34 (85.0)
	Yes	0 (0.0)C	5 (6.7)	6 (15.0)A
Change over 20° on astigmatic axis (preoperative to the 1st month)	No	31 (72.1)	64 (85.3)	33 (82.5)
	Yes	12 (27.9)	11 (14.7)	7 (17.5)
Change over 20° on the astigmatic axis (preoperative to the 6th month)	No	31 (72.1)	56 (74.7)	33 (82.5)
	Yes	12 (27.9)	19 (25.3)	7 (17.5)
Right eyes
Change over 0.5 D in astigmatic power (preoperative to the 1st month)	No	42 (77.8)	50 (83.3)	30 (83.3)
	Yes	12 (22.2)	10 (16.7)	6 (16.7)
Change over 0.5 D in astigmatic power (preoperative to the 6th month)	No	49 (90.7)	56 (93.3)	31 (86.1)
	Yes	5 (9.3)	4 (6.7)	5 (13.9)
Change over 20° in the astigmatic axis (preoperative to the 1st month)	No	42 (77.8)	60 (100.0)	32 (88.9)
	Yes	12 (22.2)B	0 (0.0)A,C	4 (11.1)B
Change over 20° in the astigmatic axis (preoperative to the 6th month)	No	44 (81.5)	46 (76.7)	27 (75)
	Yes	10 (18.5)	14 (23.3)	9 (25)

Notes:

A,B,C Significant differences in astigmatic power and axis can be found in groups A, B, and C (P<0.05).

Table 6 Changes over 0.5 D in astigmatic power and over 20° in the astigmatic axis according to the distance between tunnel and sideport incisions and the type of astigmatism, separately for the left and right eyes

	Change in astigmatic power/axis	Distance between tunnel and sideport incisions
		<90°		90°–110°		>110°
		N	%	N	%	N	%
Left eyes (ATR)
Change over 0.5 D in astigmatic power (preoperative to the 1st month)	No	15	57.7	29	76.3	6	35.3
	Yes	11	42.3	9	23.7	11	64.7
Change over 0.5 D in astigmatic power (preoperative to the 6th month)	No	26	100	35	92.1	12	70.6
	Yes	0	0	3	7.9	5	29.4
Change over 20° in the astigmatic axis (preoperative to the 1st month)	No	20	76.9	33	86.8	16	94.1
	Yes	6	23.1	5	13.2	1	5.9
Change over 20° in the astigmatic axis (preoperative to the 6th month)	No	18	69.2	26	68.4	15	88.2
	Yes	8	30.8	12	31.6	2	11.8
Left eyes (WTR)
Change over 0.5 D in astigmatic power (preoperative to the 1st month)	No	13	76.5	32	86.5	17	73.9
	Yes	4	23.5	5	13.5	6	26.1
Change over 0.5 D in astigmatic power (preoperative to the 6th month)	No	17	100	35	94.6	22	95.7
	Yes	0	0	2	5.4	1	4.3
Change over 20° in the astigmatic axis (preoperative to the 1st month)	No	11	64.7	31	83.8	17	73.9
	Yes	6	35.3	6	16.2	6	26.1
Change over 20° in the astigmatic axis (preoperative to the 6th month)	No	13	76.5	30	81.1	18	78.3
	Yes	4	23.5	7	18.9	5	21.7
Right eyes (ATR)
Change over 0.5 D in astigmatic power (preoperative to the 1st month)	No	29	76.3	30	85.7	14	82.4
	Yes	9	23.7	5	14.3	3	17.6
Change over 0.5 D in astigmatic power	No	34	89.5	34	97.1	15	88.2
(preoperative to the 6th month)	Yes	4	10.5	1	2.9	2	11.8
Change over 20° in the astigmatic axis (preoperative to the 1st month)	No	26	68.4	35	100	15	88.2
	Yes	12	31.6	0	0	2	11.8
Change over 20° in the astigmatic axis (preoperative to the 6th month)	No	28	73.7	21	60	9	52.9
	Yes	10	26.3	14	40	8	47.1
Right eyes (WTR)
Change over 0.5 D in astigmatic power (preoperative to the 1st month)	No	13	81.3	20	80	16	84.2
	Yes	3	18.8	5	20	3	15.8
Change over 0.5 D in astigmatic power (preoperative to the 6th month)	No	15	93.8	22	88	16	84.2
	Yes	1	6.3	3	12	3	15.8
Change over 20° in the astigmatic axis (preoperative to the 1st month)	No	16	100	25	100	17	89.5
	Yes	0	0	0	0	2	10.5
Change over 20° in the astigmatic axis (preoperative to the 6th month)	No	16	100	25	100	18	94.7
	Yes	0	0	0	0	1	5.3

Abbreviations: ATR, against the rule; D, diopters; WTR, with the rule.

Table 7 Results from multiple logistic regression analysis with the dependent variables presented as changes of over 0.5 D in astigmatic power and over 20° in the astigmatic axis

	OR (95% CI)*	P-value**
Change over 0.5 D in astigmatic power (preoperative to the 1st month)
Type of astigmatism
ATR	1.00
WTR	0.55 (0.31–0.96)	0.037
Distance between the tunnel and sideport incisions
<90°	1.84 (0.97–3.49)	0.064
90°–110°	1.00
>110°	2.22 (1.13–4.35)	0.021
Change over 0.5 D in astigmatic power (preoperative to the 6th month)
Type of astigmatism
ATR	1.00
WTR	0.72 (0.30–1.69)	0.447
Distance between the tunnel and sideport incisions
<90°	1.00
90°–110°	1.42 (0.46–4.42)	0.545
>110°	3.45 (1.12–10.63)	0.031
Change over 20° in the astigmatic axis (preoperative to the 1st month)
Type of astigmatism
ATR	1.00
WTR	1.01 (0.52–1.97)	0.972
Distance between the tunnel and sideport incisions
<90°	4.18 (1.9–9.2)	<0.001
90°–110°	1.00
>110°	1.97 (0.8–4.83)	0.139
Change over 20° in the astigmatic axis (preoperative to the 6th month)
Type of astigmatism
ATR	1.00
WTR	0.30 (0.16–0.54)	<0.001
Distance between the tunnel and sideport incisions
<90°	0.81 (0.43–1.53)	0.509
90°–110°	1.00
>110°	0.92 (0.46–1.85)	0.811

Notes:

* OR (95% CI) adjusted for the eye (right or left);

** indicates the reference category.

Abbreviations: D, diopters; OR, odds ratio; CI, confidence interval; ATR, against the rule; WTR, with the rule.

Figure 1 Proper location of the tunnel and sideport incisions for the right-handed superior position surgeon preserving corneal enantiomorphism.