Comparative study of surgically induced astigmatism in superior versus temporal incision in small incision cataract surgery cases.

Background: Location of incision has a significant impact on surgical outcome. It has been reported that temporal incisions induce less astigmatism than superior incisions indicating the importance of incision location. The objective of the present study was to study the effect of surgical induced astigmatism in superior versus temporal incision in small incision cataract surgery cases. Methods: 100 patients of cataract attending to Sarojini Devi eye hospital with the rule and against the rule astigmatism were included in the study. The astigmatic profile and the effect of surgical incision on astigmatism were studied. A prospective study was done in which patients were divided into two groups. MSICS was performed with superiorly located incision in group I and temporally located incision in group II. Results: Out of the total 100 patients undergoing MSICS, 59 patients had ATR, 36 patients had WTR and 5 patients had no astigmatism. Thus the pre-operative astigmatic profile shows that ATR is more common type of astigmatism in this group. Among 50 patients in superior incision group, 18 had pre-operative WTR, 29 had ATR and 3 did not have astigmatism. Postoperatively the no. of patients with WTR decreased to 10, the no. of patients with ATR increased to 35 showing that superior incision flattens vertical meridian and steepens the horizontal meridian causing ATR shift. Among 50 patients in temporal incision group, 18 had pre-operative WTR, 30 had ATR and 2 did not have astigmatism. Post operatively the no of patients with WTR increased to 25, the no of patients with ATR decreased to 20. Conclusions: Placement of incision on steep axis reduces pre-existing astigmatism. Thus in ATR astigmatism it is placed temporally and in WTR astigmatism it is placed superiorly. Thus a simple modification in incision placement can minimize surgically induced astigmatism and reduce pre-existing astigmatism.

The Changes of With-the-rule Astigmatism After Clear Corneal Temporal Incision Cataract Surgery

PURPOSE: The effect of suture presence or position of intraocular lens was evaluated on the astigmatic changes in cataract patients suffering from with-the-rule astigmatism who underwent temporal clear corneal incision cataract surgeries. METHODS: According to the presence or absence of suture and the lens position (either 180degrees or 90degrees), 49 eyes of 47 patients were divided into four groups. Astigmatism was determined using an autorefractor and by topography before surgery, and at one day, one week, one month, and two months after surgery. RESULTS: The suture group showed significant reduction in astigmatism at postoperative day 1 and week 1 by autorefractor and topography compared with the non-suture group. The group with intraocular lens insertion axis at 180degrees did not show significant reduction of astigmatism by autorefractor evaluation. Astigmatism determination by topography in this group was 1.00+/-0.73D, 1.01+/-0.77D and 1.01+/-0.81D at postoperative week 1, month 1, and month 2, respectively, and this showed significant reduction of astigmatism compared with preoperative astigmatism (1.32+/-1.17D) and group with intraocular lens insertion axis at 90degrees. In particular, the group with the sutured temporal incision and with an inserted intraocular lens axis at 180degrees showed significant reduction of astigmatism by autorefraction. CONCLUSIONS: When performing cataract surgery in with-the-rule astigmatism patients, suturing the temporal incision and inserting the intraocular lens axis at 180degrees can reduce astigmatism and minimize the effect of surgically-induced astigmatism.

The Location of Scleral Incision for Decrease of corneal Astigmatism in Sutureless Cataract Surgery

We analysed postoperative corneal astigmatic changes to know that preoperative astigmatism was able to decreased according to the location of incision in sutureless cataract surgeries. We divided 70 patients, 81 eyes that scleral pocket incision, phacoemulsification, and posterior chamber intraocular lens implantation was performed into two groups. The one is the preoperative with-the-rule(WTR)astigmatism more than 1 diopter(D) with superior incision, and the other is the preoperative WTR less than 1D or against-the-rule (ATR) astigmatism with temporal incision. We followed up the corneal astigmatic chnges until six months postoperatively. According to the results of algebraic analysis, in the superior incision group, postoperative astigmatic changes showed WTR decrease of 0.43D immediately, which advanced toward ATR decrease of 0.41D immediately, which keep up ATR decrease and showed ATR decrease of 0.44D at 6 months. According to the results of vector analysis, surgical inducced corneal astigmatism was o.69D in superior incision group and 0.50D in temporal incision group at postoperative 1day. It was 0.98D in superior incision group and 0.57D in temporal incision group at postoperative 6 months. We could decrease preoperative corneal astigmatism with performing incision at the position of greater corneal curvature. Temporal incision group showed less surgical induced astigamatic changes than superior incision.

The Changes of Refractive Error and Corneal Astigmatism after Horizontal Strabismus Surgery

We performed a prospective study of evaluating preoperative and postoperative refractive error and corneal curvature in cycloplegic refraction and keratometry in 25 eyes of 25 patients undergoing horizontal recession and resection procedure. At 4 months after operation, the change of refractive error by cycloplegic refraction was +0.12D in average in horizontal meridian, which was a significant shift toward 'with-the-rule astigmatism' direction(p0.05). In horizontal meridian, the with-the-rule astigmatic changes of +0.5D or more were present in 7 eyes(28%) and the against-the-rule astigmatic changes of -0.5D or more were present only in 2 eyes(8%). In vertical meridian, we found that 3 eyes(12%) had the changes of +0.5D or more and 6 eyes(24%) had the changes of -0.5D or more. The change of corneal curvature in keratometry amounted to average -0.50D in horizontal meridian(that means the flattening of cornea)(p0.05) at postoperative 4 months, showing the results similar to those of cycloplegic refraction. Futhermore, the astigmatic change by cycloplegic refraction and keratometry at postoperative 2 weeks and 1 month were similar to those at postoperative 4 months. These data suggest that there may be significant changes in astigmatism(more commonly in with-the-rule astigmatism) after strabismus surgery, and this astigmatic change appears due to the corneal change resulting from the variation in the force that the muscles exert on the globe.