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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 33  |  Issue : 1  |  Page : 51-55

Prevalence of corneal astigmatism in patients undergoing cataract surgery in a tertiary care hospital of Malwa region of Northern India


Department of Ophthalmology, Adesh Institute of Medical Sciences and Research, Bathinda, Punjab, India

Date of Submission21-May-2020
Date of Decision27-May-2020
Date of Acceptance29-May-2020
Date of Web Publication19-Apr-2021

Correspondence Address:
Dr. Priyanka S Gupta
Department of Ophthalmology, Adesh Institute of Medical Sciences and Research, Bathinda . 151 001, Punjab
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/kjo.kjo_62_20

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  Abstract 


Context: Preoperative corneal astigmatism plays a pivotal role in deciding the outcome of cataract surgery. If the values of biometry prevalent in a particular region are known, it will help the cataract surgeons locally even in the remote areas to optimize the postoperative visual outcome. Aims: The aim was to study the prevalence and distribution of different types of corneal astigmatism among the patients in Malwa region of Punjab and its variations according to age. Settings and Design: This was a hospital-based retrospective study conducted on 370 patients of Malwa who underwent cataract surgery between December 1, 2017, and July 31, 2018, in a medical college situated in North India. Subjects and Methods: The records of the patients were reviewed, and biometric data – K1 and K2 – measured by IOLMaster™ 700 (Carl Zeiss Meditec AG, Jena, Germany) were collected. The data were categorized based on demographic variables, type of astigmatism, and extent of astigmatism. Statistical Analysis: The data were subjected to descriptive statistical analysis to yield frequencies, percentages, and means. Results: A total of 370 eyes of 370 patients were studied. The mean age of the studied population was 60.43 ± 9.9 years. Nearly 50.54% were males and the rest were females. The mean of K, K1, and K2 was 44.23 ± 1.65 D, 43.75 ± 1.68 D, and 44.71 ± 1.74 D, respectively. Almost 82.16% of the studied population had mean corneal astigmatism <1.5 D. The corneal astigmatism was against the rule (ATR) in 52.16%, with the rule (WTR) in 27.29%, and oblique in 17.83%. With increasing age, there is a gradual shift of astigmatism from WTR to ATR, in both males and females, which peaks in the sixth decade of life. Conclusions: Majority of patients in Malwa region of Punjab have corneal astigmatism less than 1.5 D. Against-the-rule astigmatism is more common than other types of astigmatism.

Keywords: Cataract surgery, corneal astigmatism, IOLMaster 700


How to cite this article:
Gupta PS, Sidhu NK, Verma PV, Singla IJ. Prevalence of corneal astigmatism in patients undergoing cataract surgery in a tertiary care hospital of Malwa region of Northern India. Kerala J Ophthalmol 2021;33:51-5

How to cite this URL:
Gupta PS, Sidhu NK, Verma PV, Singla IJ. Prevalence of corneal astigmatism in patients undergoing cataract surgery in a tertiary care hospital of Malwa region of Northern India. Kerala J Ophthalmol [serial online] 2021 [cited 2021 Jun 18];33:51-5. Available from: http://www.kjophthal.com/text.asp?2021/33/1/51/314101




  Introduction Top


The technique of cataract surgery has seen drastic changes during the past few decades. Phacoemulsification is now the preferred modality of cataract surgery. Intraocular lens designs have also evolved tremendously during this time. These advancements have led to a significant decrease in the postoperative spherical refractory error. However, the cylindrical refractory error continues to hinder the achievement of full visual potential.[1],[2],[3],[4],[5]

Postoperative astigmatism can be either surgery induced or residual of preoperative corneal astigmatism. Surgically induced astigmatism has greatly been reduced by the use of small phacotips and smaller incisions. However, the presence of preoperative corneal astigmatism continues to challenge the final visual outcome. This astigmatism can be addressed by placing an incision on steep axis, use of toric intraocular lens, or limbal relaxing incision.[6]

Corneal astigmatism depends on the anatomy of cornea, which has regional influences apart from changes based on age and sex. Knowledge of the prevalence and distribution of corneal astigmatism can be helpful to the operating surgeon in deciding among the fore-mentioned techniques for optimizing the postoperative visual outcome. Preoperative corneal astigmatism of population of different ethnicities has been studied in the past.[5],[7],[8],[9],[10],[11],[12],[13] However, no such study has been conducted for the Malwa region of Punjabi population. We intend to study the preoperative corneal astigmatism in patients who have undergone cataract surgery in our institute. This would help in designing efficient and cost-effective cataract surgery techniques for achieving a better postoperative visual outcome in an area where agriculture is the main occupation and accessibility to gadgets such as IOLMaster™ 700 is not easy.


  Subjects and Methods Top


A retrospective study was conducted in a tertiary care medical college of Malwa region, Punjab. Research and ethical clearance was obtained from the institutional research and ethical committee. The demographic and biometric data of patients who had undergone cataract surgery from December 1, 2017, to July 31, 2018, were collected. Exclusion criteria were patient's age <21 years and a history of previous ocular surgery, ocular trauma, and ocular diseases such as pterygium, keratoconus, corneal ectasia, and inflammation. Patients in whom biometric data could not be measured by IOLMaster 700 due to dense cataract were also excluded from the study to avoid any bias due to the usage of different examination tools. IOLMaster 700 was used in our study for biometric measurements because of its ultra-high precision (5 mm or less) and good resolution (12 mm).[14] Patients not belonging to Malwa region were also excluded from the study as we intend to prepare a local database to be used by local cataract surgeons.

Precataract surgery examination included visual acuity assessment, tonometry, refraction, slit-lamp examination, and fundus examination. IOLMaster biometric data were collected prior to dilatation of pupils. The parameters measured were axial length of eyeball and keratometry values (K1 and K2). Herein, K1 represents flat corneal curvature, whereas K2 represents steep corneal curvature. K value was calculated as the mean of K1 and K2.

Corneal astigmatism was categorized as with the rule (WTR) when the meridian of maximum curvature was within 30° of vertical 90°, against the rule (ATR) when the meridian of maximum curvature was within 30° of horizontal 180°, and oblique (OBL) if it was neither WTR nor ATR. The patients were divided into groups on the basis of age – 21–30 years, 31–40 years, 41–50 years, 51–60 years, 61–70 years, 71–80 years, and ≥80 years. The data were compiled in Microsoft Excel Spreadsheets. They were categorized by demographic variables and were subjected to descriptive statistical analysis to yield frequencies, percentages, and means.


  Results Top


A total of 370 eyes of 370 patients with cataract were studied. The mean age of the studied population was 60.43 ± 9.9 years (range 21–90). Maximum number of patients were in the age group of 61–70 years (42.16%) followed by the age group of 51–60 years (28.9%). A least number of patients were in the extremes of age groups. There were 187 (50.54%) males and 183 (49.46%) females.

Corneal astigmatism among the studied population ranged from 0 D to 8.48 D, with a mean of 0.96 ± 0.93 D. Majority of the patients had corneal astigmatism of <1.5 D (82.16%) and only 3.51% of the patients had corneal astigmatism of ≥3 D [Figure 1]. The mean K value obtained was 44.23 ± 1.65 D, with mean K1 value being 43.75 ± 1.68 D (range 37.79–49.18) and mean K2 value being 44.71 ± 1.74 D (range 39.85–52.32). The age-wise distribution of mean values of K1, K2 and K are detailed in [Table 1].
Table 1: Mean values of K1, K2, and mean astigmatism among different age groups

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Of the population studied, 27.29% (n = 101) had WTR astigmatism, 52.16% (n = 193) had ATR astigmatism, 17.83% (n = 66) had oblique astigmatism, and 2.7% (n = 10) had no astigmatism. As the age advances, there was a shift from WTR to ATR astigmatism, in both males and females, with a peak in the sixth decade of life [Figure 2],[Figure 3],[Figure 4].
Figure 1: Distribution of amount of astigmatism among the studied population

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Figure 2: Distribution of different types of astigmatism according to age group

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Figure 3: Distribution of different types of astigmatism according to age group in females

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Figure 4: Distribution of different types of astigmatism according to age group in males

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  Discussion Top


The main components contributing to ocular astigmatism are cornea and lens. Lenticular astigmatism is taken care of and eliminated in patients undergoing uncomplicated cataract surgery, but the persistence of preexisting corneal astigmatism leads to patient dissatisfaction because of some amount of residual unaided blurring or distortion of vision. Studies showing the prevalence and type of corneal astigmatism in patients undergoing cataract surgery are well documented in several countries, but such data are lacking for population belonging to the Malwa region of Punjab.

Ours is the study conducted in a tertiary care medical college of this area which analyzes the prevalence and type of corneal astigmatism in the region. This study will help in enhancing the postcataract surgery satisfaction rate as it will help the surgeons to adopt suitable corrective procedures for elimination of corneal astigmatism, even if costly equipment such as IOLMaster 700 are not handy.

Our study included 370 eyes of 370 patients with a mean age of 60.43 ± 9.9 years, which is similar to the studies done by Rashid et al,[15] Chaudhary and Dahal,[16] and Prasher and Sandhu.,[17] which had mean ages of 61.9 ± 8.1, 64.45 ± 12.89, and 59.54 ± 10.96 years, respectively, but much lower from studies conducted by Chen et al.,[8] Khan and Muhtsaheb,[5] Ante Ercegovic et al.,[10] and Yuan et al.[18] This variation for mean age among studies could be attributed to the difference in sample size and racial and ethnic differences in the age of developing cataract. Males and females included in our study were 51% and 49%, respectively, which correspond to the study conducted by Prasher and Sandhu[17] with 49% of males and 51% of females and Yuan et al.[18] with 46% of males and 54% of females. This represents equal cataract surgery-seeking behavior in both the genders in the Malwa belt.

The mean corneal astigmatism in our study came out to be 0.96 ± 0.93 D, which is marginally lower as compared to studies done by Prasher and Sandhu[17] Chen et al.,[8] and Khan and Muhtsaheb,[5] which reported the mean corneal astigmatism values of 1.04 ± 1.04, 1.01 ± 0.69, and 1.03 ± 0.73 D, respectively. It was much lower than the study conducted by Rashid et al,[15] Yuan et al.,[18] and Isyaku et al.[19]

The range of corneal astigmatism in our study was 0–8.48 D, which is slightly lower than the study conducted by Prasher and Sandhu,[17] with range being 0–9.75 D, but significantly higher than studies conducted in other countries.[5],[8],[15],[16],[18],[19]

Majority of population (82.16%) in our study had corneal astigmatism <1.5 D, which outnumbers the results reported by Prasher and Sandhu[17] of corneal astigmatism <1 D in 59.3% of population. Another study reported astigmatism ≥1 D in 66.9% of the eyes.[19] These values of astigmatism of our study, however, correlate well with a study conducted by Rashid et al.[15] in Nepal. The study by Miyake et al.[20] observed a prevalence of <1 D of corneal astigmatism to be 63.6%.

More than half of the population under our study had ATR astigmatism (52.16%), with WTR astigmatism being the second largest category comprising of 27.2% population and only 17.83% of population had oblique astigmatism. The percentage of ATR astigmatism in our study was higher as compared to the study by Chaudhary and Dahal[16] (43.6%) and lower as compared to the study by Isyaku et al.[19] (56.66%). There are studies by De Bernardo et al.[13] and Hoffman and Hutz,[12] which have reported higher prevalence of WTR as compared to ATR.

The variation of results between studies on the Indian population and foreign population and even between different regions of India can be attributed to various factors including difference of sample sizes, geographical and ethical distribution of populations, variation of ocular anatomy according to race, different environmental and lifestyle practices of different races, and the socioeconomic status of the included population. Variations in inclusion and exclusion criteria for populations under different studies and difference in instruments used for taking measurements are also important factors affecting the studies, thus leading to differences in results among different studies.

There are some limitations to our study which include (1) our retrospective study was based on clinical data which may lead to some selection bias, (2) the ocular biometric data were drawn retrospectively from the patients who underwent cataract surgery, and (3) the relationship between biometric parameters and genetics, diet, education, occupation, and severity of cataract could not be established due to lack of relevant data.


  Conclusions Top


Our study shall provide useful data on the corneal biometry of the region, which can help the local cataract surgeons to individualize cataract surgery in a way that it gives better visual outcomes, which are affordable especially in the population of Malwa, where the main occupation of people is farming.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Koch DD, Ali SF, Weikert MP, Shirayama M, Jenkins R, Wang L. Contribution of posterior corneal astigmatism to total corneal astigmatism. J Cataract Refract Surg 2012;38:2080-7.  Back to cited text no. 1
    
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Wang L, Hill WE, Koch DD. Evaluation of intraocular lens power prediction methods using the American Society of cataract and refractive surgeons post-keratorefractive intraocular lens power calculator. J Cataract Refract Surg 2010;36:1466-73.  Back to cited text no. 2
    
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Wang L, Mahmoud AM, Anderson BL, Koch DD, Roberts CJ. Total corneal power estimation: Ray tracing method versus Gaussian optics formula. Investig Ophthalmol Vis Sci 2011;52:1716-22.  Back to cited text no. 3
    
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Nichamin LD. Astigmatism control. Ophthalmol Clin North Am 2006;19:485-93.  Back to cited text no. 4
    
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Khan MI, Muhtaseb M. Prevalence of corneal astigmatism in patients having routine cataract surgery at a teaching hospital in the United Kingdom. J Cataract Refract Surg 2011;37:1751-5.  Back to cited text no. 5
    
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Mozayan E, Lee JK. Update on astigmatism management. Curr Opin Ophthalmol 2014;25:286-90.  Back to cited text no. 6
    
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Ferrer-Blasco T, Montés-Micó R, Peixoto-de-Matos SC, González-Méijome JM, Cerviño A. Prevalence of corneal astigmatism before cataract surgery. J Cataract Refract Surg 2009;35:70-5.  Back to cited text no. 7
    
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Chen W, Zuo C, Chen C, Su J, Luo L, Congdon N, et al. Prevalence of corneal astigmatism before cataract surgery in Chinese patients. J Cataract Refract Surg 2013;39:188-92.  Back to cited text no. 8
    
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Lekhanont K, Wuthisiri W, Chatchaipun P, Vongth-Ongsri A. Prevalence of corneal astigmatism in cataract surgery candidates in Bangkok, Thailand. J Cataract Refract Surg 2011;37:613-5.  Back to cited text no. 9
    
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Ercegović A, Brajković J, Surać IK, Haluzan MB. Prevalence, distribution and types of corneal astigmatism in cataract surgery patients in Sibenik County. Actaclinica Croatica 2012;51:275-8.  Back to cited text no. 10
    
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Fotedar R, Wang JJ, Burlutsky G, Morgan IG, Rose K, Wong TY, et al. Distribution of axial length and ocular biometry measured using partial coherence laser interferometry (IOL Master) in an older white population. Ophthalmology 2010;117:417-23.  Back to cited text no. 11
    
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Hoffmann PC, Hütz WW. Analysis of biometry and prevalence data for corneal astigmatism in 23,239 eyes. J Cataract Refract Surg 2010;36:1479-85.  Back to cited text no. 12
    
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De Bernardo M, Zeppa L, Cennamo M, Iaccarino S, Zeppa L, Rosa N. Prevalence of corneal astigmatism before cataract surgery in Caucasian patients. Eur J Ophthalmol 2014;24:494-500.  Back to cited text no. 13
    
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Karunaratne N. Comparison of the Pentacam equivalent keratometry reading and IOLMaster keratometry measurement in intraocular lens power calculations. Clin Exp Ophthalmol 2013;41:825-34.  Back to cited text no. 14
    
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Rashid MA, Hossain KA, Islam A. Prevalence of pre-existing corneal astigmatism in age related cataract patient. Faridpur Med Coll J 2013;8:2-4.  Back to cited text no. 15
    
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Chaudhary M, Dahal HN. Prevalence and types of corneal astigmatism in patients undergoing cataract surgery. J Inst Med 2017;39:22-8.  Back to cited text no. 16
    
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Prasher P, Sandhu JS. Prevalence of corneal astigmatism before cataract surgery in Indian population. Int Ophthalmol 2017;37:683-9.  Back to cited text no. 17
    
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Yuan X, Song H, Peng G, Hua X, Tang X. Prevalence of corneal astigmatism in patients before cataract surgery in Northern China. J Ophthalmol 2014;2014:536412.  Back to cited text no. 18
    
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Isyaku M, Ali SA, Hassan S. Preoperative corneal astigmatism among adult patients with cataract in Northern Nigeria. Indian J Ophthalmol 2014;62:1094-5.  Back to cited text no. 19
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Miyake T, Kamiya K, Amano R, Shimizu K. Corneal astigmatism before cataract surgery. Nihon Ganka Gakkai Zasshi 2011;115:447-53.  Back to cited text no. 20
    


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