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

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

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

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

Results There were no significant differences between patients in the 3-plane incision and 2- plane incision groups Mean age of the patients was 68.3 ± 8.2 years (range, 50 - 95 ) 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

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

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)

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

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

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

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

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