|Year : 1992 | Volume
| Issue : 3 | Page : 71-73
Selective suture cutting for control of astigmatism following cataract surgery
RK Bansal, Amod Gupta, SPS Grewal
Department of Ophthalmology, Postgraduate Institute of Medical Education & Research, Chandigarh 160 012, India
Department of Ophthalmology, Postgraduate Institute of Medical Education & Research, Chandigarh 160 012
Source of Support: None, Conflict of Interest: None
Use of 10-0 monofilament nylon in ECCE cataract surgery leads to high with the rule astigmatism. Many intraoperative and post operative methods have been used to minimise post operative astigmatism. We did selective suture cutting in 38 consecutive patients. Mean keratometric astigmatism at three and six weeks post operative was 5.76 and 5.42 dioptres (D) respectively. 77.5% of eyes had astigmatism above 2 D. Selective suture cutting along the axis of the plus high cylinder was done after six weeks of surgery. Mean post suture cutting keratometric astigmatism was 3.3 D and 70% of the eyes had astigmatism below 2 D. After 3 months of surgery mean keratometric astigmatism was reduced to 1.84 D. Axis of the astigmatism also changed following suture cutting. 40% of the eyes showed improvement in their Snellen acuity following reduction in the cylindrical power.
Keywords: Astigmatism, Cataract surgery, Monofilament, Suture cutting
|How to cite this article:|
Bansal R K, Gupta A, Grewal S. Selective suture cutting for control of astigmatism following cataract surgery. Indian J Ophthalmol 1992;40:71-3
A high with the rule (plus cylinder with axis between 70 0 - 110 0) suture induced astigmatism has been reported following the use of 10 o monofilament nylon suture for wound closure in cataract surgery . The astigmatism adversely affects the quality of visual acuity with glasses, contact lenses or intraocular lenses, besides giving aesthenopic symptoms to the patient  Many operative (intraoperative keratometry) and post operative (suture cutting) methods have been used to minimise postoperative astigmatism . Variable and unpredictable astigmatism has resulted with the use of intraoperative keratometry . Post operative suture adjustment or suture cutting has been used to reduce astigmatism and has given favourable results ,,,. We report our experience of selective and controlled suture cutting, on post operative astigmatism, in 38 consecutive patients undergoing cataract surgery.
| Material and methods|| |
Forty consecutive patients, who had undergone extracapsular cataract extraction (ECCE) without intraocular lens implantation were enrolled in the study. Preoperative keratometry (Zeiss) was done 24 hours before surgery. In all patients, a mid limbal, two step incision ranged from 10-11 mm. Following aspiration of the lens matter, the anterior chamber was formed with air and wound was closed with seven 10 o monofilament interrupted sutures. The knots were buried in the track on the corneal side. Keratometry and retinoscopy were done three and six weeks after the surgery. If the keratometeric cylinder was more than 1.5 dioptres (D) at six weeks, the suture along the axis of maximum plus cylinder and two adjoining sutures were cut. The patient was seated on the slit lamp and a razor blade was used to cut the corneal end of the suture. The corneal end of the suture got retracted into the stroma and the other end remained buried under the conjunctiva. If high plus cylinder ( 1.5 D) persisted after one week of suture cutting, two additional sutures on either side of the previously cut sutures were cut. A total of 38 patients required suture cutting. Keratometry and retinoscopy were done again after one week of suture cutting. Final keratometry and retinoscopy was done 12 weeks after the surgery. Statistical analysis was done by using Student's `t' test.
| Results|| |
There were 22 female and 16 male patients in the age range of 30-76 years (mean 57.1 years). Mean preoperative keratometric astigmatism was 0.99 D (range 0-5.92 D). Mean preoperative astigmatism after three and six weeks of surgery was 5.76 D and 5.42 D (range 0.47-11.60 D) respectively and the retinoscopic astigmatism was 3.32 D and 3.43 D respectively [Figure - 1]. Twenty four eyes (63.2%) had keratometric astigmatism of more than 5 D, seven eyes (18.4%) between 2-5 D and nine eyes (23.9%) had less than 2 D of astigmatism.
One week post suture cutting, mean keratometric astigmatism was 3.30 D (range 0-12.65 D) and refractive astigmatism was 1.96 D (range 0-6.0 D). Twenty eight eyes (73.7%) now had less than 2 D of keratometric astigmatism, 11 eyes (28.9%) between 2-5 and only one eye had more than 5 D of astigmatism. After twelve weeks of surgery, mean keratometric astigmatism was 1.84 D (range 0-3.25 D) and retinoscopic astigmatism was 1.03 D (range 0-3 D). The resultant change in the dioptric power of the astigmatism following suture cutting is shown in [Table - 2].
The axis of the cylinder shifted following suture cutting. Before suture cutting 77.5% of the eyes had with the rule astigmatism and 22.5% of the eyes had oblique astigmatism. One week after suture cutting, 10% of the eyes had no astigmatism, 41% had oblique, 31% with the rule and 18% had against the rule astigmatism [Table - 2].
Forty percent of the eyes showed improvement in their best corrected Snellen acuity following suture cutting. Three Snellen line improvement occurred in 5%, two line in 12.5% and one line improvement in 22.5% of the eyes.
| Discussion|| |
High corneal astigmatism following cataract surgery prevents an aphakic patient from enjoying rapid visual recovery with glasses, contact lenses and intraocular lenses .There are a large number of variables which contribute to the resultant postoperative astigmatism. The subject has been reviewed by Swinger (1987). Type of suture material and technique of suturing play an important role in causing suture induced astigmatism . Use of 10-0 monofilament nylon in continuous or interrupted form leads to with the rule astigmatism and resultant astiqmatism can be as high as 12 D or more .The suture induced astigmatism with nylon sutures, changes very little with time (unless manipulated) after an initial period of stabilization within first two weeks of surgery ,,.
Surgical keratometers were developed to control astigmatism by manipulating sutures at the end of surgery and hence eliminating the need for cutting or removing sutures during postoperative period and decreasing the patient follow up visits , but a number of studies have found it to be of limited success . Samples et a1  even found a poor correlation between keratometric readings taken introperative and shortly after the surgery.
Suture cutting with laser or blade after six weeks of surgery for continuous and interrupted sutures has shown favourable results as far as reduction of 'the cylindrical power is concerned . In the present study, the mean keratometric cylindrical power was reduced significantly (upto 6 D) in 80% of the eyes Figure 2 following selective sutures cutting. Similar results have been reported in the literature .
Majority of the eyes show with the rule astigmatism with nylon sutures . In the present study, 77.5% of the eyes had with the rule astigmatism before suture cutting. It persisted in 31% of the eyes after suture cutting and changed to oblique in 41% of the eyes. 18% of the patients also showed a change in axis from with the rule to against the rule. This change in axis results from change in vector forces after suture cutting. , The change in the axis from with the rule to oblique was not associated with poor vision as 62.5% of the patients with oblique astigmatism had 6/12 or better vision similar to the patients with, with the rule astigmatism and they tolerated glasses well. A similar change in the axis of the cylinder has been reported following suture removal or cutting with laser or blade ,. Atkins and Ropar Hall  reported shift in the axis of the cylinder in 64% of the cases following suture cutting. Similarly 40% of the cases by Luntz et al  showed change in the axis from horizontal to oblique following suture cutting but there was no change from with the rule to against the rule.
Improvement in Snellen visual acuity occurred in 40% of our patients following reduction in the cylinderical power. Fifty six percent of the eyes in a series by Atkins and Ropar Hall  showed some improvement in visual acuity following suture adjustment.
None of the 38 patients where sutures were cut showed any complication resulting from suture cutting though bacterial endophthalmitis has been reported .
Suture cutting along the axis of plus cylinder, after six weeks of surgery has been found to be an effective and safe method for minimising post operative suture induced astigmatism. We recommend cutting at least three sutures along the axis of the plus cylinder in patients with high postoperative astigmatism and rarely there will be need to cut additional two sutures to reduce post operative astigmatism.
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[Figure - 1]
[Table - 1], [Table - 2]