Home About us Editorial board Ahead of print Current issue Search Archives Submit article Instructions Subscribe Contacts Login 
  • Users Online: 1087
  • Home
  • Print this page
  • Email this page

   Table of Contents      
Year : 2005  |  Volume : 53  |  Issue : 3  |  Page : 201-203

Reduction in astigmatism in manual small incision cataract surgery through change of incision site

Gokhale Eye Hospital and Eye bank, Anant building, Gokhale Road, Dadar, Mumbai - 400 028, India

Date of Submission12-May-2003
Date of Acceptance23-Nov-2003

Correspondence Address:
Nikhil S Gokhale
Gokhale Eye Hospital and Eye bank, Anant building, Gokhale Road, Dadar, Mumbai - 400 028
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0301-4738.16684

Rights and Permissions

To compare the astigmatism induced by a superior, supero-temporal and temporal incision in manual small incision cataract surgery. Induced astigmatism was analysed by Cartesian coordinates based analysis, using Holladay's system. Mean astigmatism induced by surgery was 1.28 D x 2.9 degrees for superior incision, 0.20 D x 23.7 degrees for supero-temporal incision and 0.37 D x 90 degrees for temporal incision. The study found that induced astigmatism was lower in the temporal and superotemporal groups compared to that in the superior group.

Keywords: Cataract surgery, Astigmatism, Small incision cataract surgery

How to cite this article:
Gokhale NS, Sawhney S. Reduction in astigmatism in manual small incision cataract surgery through change of incision site. Indian J Ophthalmol 2005;53:201-3

How to cite this URL:
Gokhale NS, Sawhney S. Reduction in astigmatism in manual small incision cataract surgery through change of incision site. Indian J Ophthalmol [serial online] 2005 [cited 2021 Apr 11];53:201-3. Available from: https://www.ijo.in/text.asp?2005/53/3/201/16684

Click here to view

Click here to view

Click here to view

Click here to view
Phacoemulsification has become a routine procedure for cataract extraction in most parts of the world. In order to obtain the advantages of a self-sealing sutureless incision at a low cost, ophthalmologists in the developing world are performing manual small incision cataract surgery (SICS) as an alternative. High astigmatism is an important cause of poor uncorrected visual acuity after cataract surgery.[1],[2] The aim of the study is to compare the astigmatism induced by a superior, supero-temporal and temporal incision in manual SICS.

  Materials and Methods Top

Forty-five eyes of 42 patients (24 Male / 18 Female) with a mean age of 55.4 years (range 29 - 72 years) were included in the study. The inclusion criteria were patients with keratometric astigmatism of 1.5 D or less, good fixation and cataract upto grade 4 nuclear sclerosis. The higher grades of nuclear sclerosis cases were excluded to keep the uniformity in size and architecture of the incision. They were subdivided randomly into three groups of 15 eyes each. Group A received superior incision, group B received superotemporal incision and group C eyes received a temporal incision. Preoperatively, a full ophthalmic examination including keratometry and 'A' scan biometry was done by the surgeon (NG). Keratometry was performed using a manual keratometer (Bausch and Lomb). All surgeries were done by one surgeon (NG) under peribulbar anaesthesia. Manual SICS with viscoexpression technique was used. The incision architecture was similar in all three groups. A 6 mm scleral frown incision, 1.5 mm from the limbus was made with a 15 number Bard Parker blade. A funnel shaped sclerocorneal pocket incision was created with a diamond crescent knife. Two side ports were made 180 degrees apart on either side of the scleral tunnel with a diamond knife. With a diamond keratome, the anterior chamber was entered 1.5 mm into the clear cornea and the internal incision was enlarged sideways to 8 mm. A single piece PMMA intraocular lens of 6mm optic size and 12.5 mm total size was implanted into the capsular bag. Patients were examined on days 1, 4, 10, 40 and 90. Betamethasone 0.1% eye drops were administered six times a day in the first postoperative week and gradually tapered every week over six weeks. Ofloxacin eye drops 0.3% were administered four times a day for the first ten days and then discontinued. Uncorrected and best-corrected visual acuity and keratometry were recorded on each visit. All postoperative work including refraction was done by the surgeon (NG). There were no intraoperative or postoperative complications. All patients were followed up without any dropout.

Preoperative and postoperative (day 90) keratometric readings and refraction (day 90) were used for analysis. All calculations were performed using the surgically induced astigmatism (SIA) Calculator Version 1.0 a free software programme. Amplitude of preoperative and postoperative astigmatism was calculated from the difference in the keratometric value in the steeper and flatter meridian, using the plus cylinder notation. Astigmatism was considered a vector with a magnitude equal to this value, directed towards the steeper meridian. For example, keratometry values of 43.5 x 900 and 44 x 1800 would imply astigmatism of 0.5 D 1800. The amplitude of SIA was also calculated for each eye from the preoperative and postoperative amplitudes using the SIA software programme. Mean and standard deviation was calculated for all the individual values obtained in each group [Table - 1] - Amplitude of astigmatism).

The data were also analysed using Cartesian coordinates based analysis using Holladay's system,[3] whereby each of the astigmatic vectors was converted into x and y values. These x and y values were independently averaged and reconverted into the astigmatic vector form, producing mean pre- and postoperative astigmatic values for the group. This mean astigmatism, called the centroid, represents the true mean of the data set, which takes into consideration all elements forming the data. From the pre- and postoperative x and y values, SIA x and y values were also calculated for each eye. These were averaged and converted into a vector form which gives the SIA centroid [Table - 2]. These data were also displayed and analysed using double angle plots (DAP) as depicted in [Figure - 1], [Figure - 2], [Figure - 3]. A highly localised clustering of points on the DAP indicated a homogeneous group with true representative of its centroid with a high predictive value.

  Results Top

The amplitude of preoperative astigmatism was similar and around 0.5 D in the three groups [Table - 1]. The amplitude of postoperative astigmatism [Table - 1] was higher in group A (1.45 + 0.94) than in group B (0.43 + 0.27) and in group C (0.67 + 0.65). The amplitude of surgically induced astigmatism [Table - 1] was also higher in group A (1.36 + 1.03) than in group B (0.51 + 0.49) and in group C (0.40 + 0.40).

Analysis of the SIA centroids [Table - 2] shows that 1.28 D of horizontal steepening (or vertical flattening) was induced by making a superior incision. Surgically induced astigmatism in the supero-temporal group was 0.20 D at 23.7° whereas the temporal incision induced an average horizontal flattening (or vertical steepening) of about 0.37 D.

The SIA vectors in the superior group on the DAP [Figure - 1] show clustering, implying a high predictive value of the centroid obtained,that is, 1.28 D x 2.9. This indicates that making a superior incision consistently induced an average of 1.28 D of horizontal steepening. The SIA vectors in the superotemporal group were well spread out on the DAP [Figure - 2] implying a low predictive value. The SIA vectors of the temporal group were also well clustered [Figure - 3] implying a high predictive value and a temporal incision consistently induced an average horizontal flattening of about 0.37 D.

  Discussion Top

Manual SICS is an alternative for phacoemulsification but the astigmatism is higher due to the larger size of incision. Burgansky et al[4] have shown an increase in astigmatism with an increase in incision size. In their study by vector analysis, the mean induced astigmatism was 0.6 + 0.3 D for 6 mm incision, 0.75 + 0.67 D for a 6.5 mm incision and 1.36 + 0.77 D for a 7 mm incision. Kimura et al[5] have shown by vector analysis that surgically induced astigmatism is less with an oblique incision (1.02 + 0.66 D) than with a superior incision (1.41 + 0.72 D).

The temporal location is farthest from the visual axis and any flattening due to the wound is less likely to affect the corneal curvature at the visual axis. When the incision is located superiorly, both gravity and eyelid blink tend to create a drag on the incision.

These forces are neutralised better with temporally placed incisions because the incision is parallel to the vector of the forces. With the rule astigmatism induced by a temporal incision is advantageous because most elderly cataract patients have preoperative against the rule astigmatism. The superotemporal incision also, is probably free from effect of gravity and eyelid pressure and tends to induce less astigmatism.

Astigmatism induced in manual SICS done with a superior, superotemporal and temporal scleral tunnel incision have been compared. Modern methods of astigmatic data handling require that both amount and axis of astigmatism be given equal importance, using a mathematically validated method.[6] Accordingly, the method described by Holladay et al was employed.[3] Holladay's method is more difficult to comprehend than vector analysis, but it has been chosen over the latter as it gives more accurate results.[7] The study found that induced astigmatism was lower in the temporal and superotemporal groups compared to that in the superior group. Astigmatism in the superotemporal and temporal groups was comparable.

The superior incision is likely to induce about 1.28 D of astigmatism as suggested by the centroid (1.28 D x 2.9 degrees). This is a definite clinical gain, as one can aim to neutralise a pre-existing astigmatism of, say, 1.25 D x 90 degrees. In conclusion, a shift in the incision site to the superotemporal or temporal sclera is recommended except in patients with a pre-existing 'with the rule' astigmatism of about 1D. Small sample size is a weakness of this study. Our conclusions need to be validated with a larger study.

  References Top

Prajna NV, Chandrakanth KS, Kim R, Narendran V, Selvakumar S, Rohini G, et al . The Madurai intraocular lens study II: clinical outcomes. Am J Ophthalmol 1998;125:14-25.  Back to cited text no. 1
Yorston D, Foster A, Wood M, Foster A. Does prospective monitoring improve cataract surgery outcomes in Africa? Br J Ophthalmol 2002;86:543-7.   Back to cited text no. 2
Holladay JT, Dudeja DR, Koch DD. Evaluating and reporting astigmatism for individual and aggregate Data. J Cataract Refract Surg 1998;24:57-65.  Back to cited text no. 3
Burgansky Z, Isakov I, Avizemer H, Bartov E. Minimal astigmatism after sutureless planned extracapsular cataract extraction. J Cataract Refract Surg 2002;28:499-503.  Back to cited text no. 4
Kimura H, Kuroda S, Mizoguchi N, Terauchi H, Matsumura M, Nagata M. Extracapsular cataract extraction with a sutureless incision for dense cataracts. J Cataract Refract Surg 1999;25:1275-9.   Back to cited text no. 5
Naeser K. Popperian falsification of methods of assessing surgically induced astigmatism. J Cataract Refract Surg 2001;27:25-30.  Back to cited text no. 6
Sawhney S. Theoretical validity of vector analysis for aggregate astigmatic data. J Cataract Refract Surg 2002;28:385-6.  Back to cited text no. 7


  [Figure - 1], [Figure - 2], [Figure - 3]

  [Table - 1], [Table - 2]

This article has been cited by
1 Cirugía manual de catarata con incisión pequeña bajo anestesia tópica/intracameral por residentes
Jesús Oscar Moya Romero,Leopoldo Morfín Avilés,Edmundo Salazar López
Revista Mexicana de Oftalmología. 2014;
[Pubmed] | [DOI]
2 Combined Topical-Intracameral Anesthesia in Manual Small-Incision Cataract Surgery
Lihua Wang,Jinyang Li,Guoxing Li,Xu Xu,Hai Tao,Wei Chen
Asia-Pacific Journal of Ophthalmology. 2013; 2(1): 9
[Pubmed] | [DOI]
3 Manual Small Incision Cataract Surgery
Rengaraj Venkatesh,David F. Chang,Radhakrishnan Muralikrishnan,Kenia Hemal,Pariskshit Gogate,Sabyasachi Sengupta
Asia-Pacific Journal of Ophthalmology. 2012; 1(2): 113
[Pubmed] | [DOI]
4 Katarakt-Operationsergebnisse durch temporale Kleinschnitttechniken mit und ohne Phakoemulsifikation : Ergebnisse einer prospektiven Studie aus Kenia
S. Briesen, H. Roberts
Der Ophthalmologe. 2012; 109(5): 462
[VIEW] | [DOI]
5 The influence of corneal wound size on surgically induced corneal astigmatism after phacoemulsification
Yi-Hsuan Wei,Wei-Li Chen,Pei-Yuang Su,Elizabeth P. Shen,Fung-Rong Hu
Journal of the Formosan Medical Association. 2012; 111(5): 284
[Pubmed] | [DOI]
6 Phacoemulsification versus extracapsular cataract extraction: where do we stand? :
Suzann Pershing, Abha Kumar
Current Opinion in Ophthalmology. 2011; 22(1): 37
[VIEW] | [DOI]
7 Cataract surgery in developing countries :
Rohit Khanna, Siddharth Pujari, Virender Sangwan
Current Opinion in Ophthalmology. 2011; 22(1): 10
[VIEW] | [DOI]
8 Nucleus management in manual small incision cataract surgery by phacosection
Ravindra, M.S.
Indian Journal of Ophthalmology. 2009; 57(1): 41-43
9 Wound construction in manual small incision cataract surgery
Haldipurkar, S.S., Shikari, H.T., Gokhale, V.
Indian Journal of Ophthalmology. 2009; 57(1): 9-13
10 Small incision cataract surgery: Complications and mini-review
Gogate, P.M.
Indian Journal of Ophthalmology. 2009; 57(1): 45-49
11 SICS - A cost effective alternative to phacoemulsification for developing countries in Nepal
Nowak, R.
Klinika Oczna. 2008; 110(1-3): 92-97


    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

  In this article
Materials and Me...
Article Figures
Article Tables

 Article Access Statistics
    PDF Downloaded1427    
    Comments [Add]    
    Cited by others 11    

Recommend this journal