1. Comparing Factors Affecting Surgically Induced Astigmatism
After Phacoemulsfication
Colin SH Tan1,2, Francine P. Yang1, Hon Kiat Wong1
1Department of Ophthalmology, Tan Tock Seng Hospital, Singapore
2 Doheny Eye Institute, University of Southern California, USA
The authors have no financial interest in the subject matter of this e-poster

2. Introduction
With continuous advances in cataract surgery, patients’ have higher expectations of surgical and visual outcomes
Astigmatism has considerable impact on quality of vision and has been shown to significantly affect patients’ satisfaction with the postoperative outcome
Astigmatism is affected by surgical technique, the type and size of the corneal incision, and wound location
Some surgeons perform a 3-plane clear corneal incision during phacoemulsification as it is believed to have a greater impact on astigmatic correction and also wound stability compared to the standard phaco incision

3. Objectives
Our study aimed to review the surgically-induced astigmatism during phacoemulsification and correlate it the following factors:
Wound type – 3-plane vs. 2-plane incisions
Wound location – along the steep axis of astigmatism or elsewhere
The use of sutures to close the wound

4. Methods
A review of 53 consecutive cases of phacoemulsification performed by a single surgeon at the National Healthcare Group Eye Institute, Singapore.
A 3-plane incision was performed using a microkeratome to make a 50% corneal thickness incision, followed by a shelving incision similar to the 2-plane incision
In all surgeries, the following were standardized:
2.65 mm clear corneal wound
Phacoemulsification system (Signature, Abbott Medical Optics, USA)
3-piece Acrylic lens (Sensar AR40e, Abbott Medical Optics, USA)
Surgically induced astigmatism was calculated using vector analysis

5. Results
There were no significant differences between patients in the 3-plane incision and 2- plane incision groups
Mean age of the patients was ± 8.2 years (range, )
3-plane incision
2-plane incision
p value
Mean age (yrs)
69.4 (± 7.4)
66.6 (± 9.4)
0.230
Gender
Male
Female
19 (57.6%)
14 (42.4%)
10 (50.0%
10 (50.0%)
0.776
The overall mean surgically-induced astigmatism was 0.72D ± 0.61
There were no cases of post-operative wound leak in either the 2- or 3-plane incision groups

6. Comparison of astigmatism between 2- and 3-plane incisions
Surgically-induced astigmatism was lower in 3-plane compared to 2-plane corneal incisions
The trend was seen in patients with both low and high pre- operative astigmatism
P=0.81
P=0.003

7. Wound sutures and axis of astigmatism
Sutures significantly affected post-operative astigmatism:
In eyes where the corneal wound was sutured, the mean surgically-induced astigmatism was significantly higher compared to eyes without sutures (1.61D vs. 0.68D, P=0.01)
There was no significant difference in astigmatism between incisions made along the steep meridian (25/53 eyes) or incisions made elsewhere (28/53 eyes) (0.71D vs. 0.73D, P=0.91)

8. Effects of demographics on astigmatism
There was no significant difference in surgically induced astigmatism between males and females
P=0.15
SIA was higher in the left eye compared to the right eye, although the results were not statistically significant.
P=0.08

9. Discussion
Some surgeons perform a 3-plane corneal incision because they feel that it is structurally more stable and reduces the risk of postoperative wound leak.
Our results show an additional advantage of a 3-plane incision: significantly lower surgically-induced astigmatism vs. a 2-plane incision.
This was especially evident in patients with lower pre-operative astigmatism (0.49D vs. 1.07D, p=0.03)
Although phacoemulsification incisions are normally self sealing, a surgeon may sometimes elect to use a suture if there is doubt about wound stability or if the patient requires laser photocoagulation soon after surgery. Our study demonstrates that a suture placed at the wound has a significant effect on post-operative astigmatism
The effect of sutures should be considered in terms of astigmatic control 9

10. Discussion
There is limited information in the current ophthalmic literature on the factors affecting post-operative astigmatism in phacoemulsification.
In a review, Batlan1 stated that, “Decreasing SIA has been a major goal in the advancement of cataract surgery” and recommended the selection of incision type and location, and consideration of preoperative astigmatism to minimize postoperative astigmatism
Studies have reported factors affecting surgically-induced astigmatism (SIA):
SIA is higher in clear corneal incision vs corneoscleral incision2
Smaller incisions cause less SIA compared to larger incisions2,3,4
Temporal placed incisions have lesser SIA versus superiorly placed incisions2 (for preoperative against the rule astigmatism)
1. Batlan et al, Curr Opin Ophthal 1996
2. Nielsen PJ et al, JCRS 1995
3. Kohnen T et al, JCRS 1995
4. Pfleger T et al, JCRS 1996

11. Discussion
Additional studies have shown that:
Clear corneal incision results in higher SIA only in larger incisions (3 mm vs. 2 mm) compared to scleral incisions (Hayashi et al)
2.2 mm micro-coaxial incisions have lower SIA compared to traditional 3 mm clear-corneal incisions (Masket et al)
There was no significant differences in resultant astigmatism when comparing phaco vs. vitrectomy vs. both procedures together (Yuen et al)
In a study evaluating factors affecting postoperative astigmatism, Cho et al concluded that different strategies were required for different groups of patients (classified by pre-operative astigmatism)
To our knowledge, the effect of a 3- vs. 2-plane corneal incision have not previously been reported, demonstrating the myriad factors which impact surgically-induced astigmatism
5. Hayashi et al, Ophthalmol 2010
6. Masket et al, JCRS 2009
7. Yuen et al, Eye 2009
8. Cho et al, Kor J Oph 1996

12. Conclusion Our study has demonstrated that:
A 3-plane cornea wound incision results in significantly lower surgically-induced astigmatism compared to a 2-plane wound.
Wound sutures result in significantly higher astigmatism
Taking into account our review of previously established risk factors, it is clear that further research is required to design models to determine best individualized management to reduce postoperative astigmatism 12