About MEAJO | Editorial board | Search | Ahead of print | Current Issue | Archives | Instructions to authors | Online submission | Subscribe | Advertise | Contact | Login 
Middle East African Journal of Ophthalmology Middle East African Journal of Ophthalmology
Users Online: 2519   Home Print this page Email this page Small font sizeDefault font sizeIncrease font size


 
  Table of Contents 
ORIGINAL ARTICLE
Year : 2020  |  Volume : 27  |  Issue : 3  |  Page : 156-159  

Prevalence of keratoconus in refractive surgery cases in Western India


1 Department of Cornea and Refractive Surgery, C. H. Nagri Eye Hospital, Ahmedabad, Gujarat, India
2 Department of Refractive Surgery, C. H. Nagri Eye Hospital, Ahmedabad, Gujarat, India
3 Department of Ophthalmology, AMC MET Medical College, Ahmedabad, Gujarat, India

Date of Submission20-Jul-2019
Date of Acceptance07-Jun-2020
Date of Web Publication30-Oct-2020

Correspondence Address:
Ms. Zalak Shah
Department of Refractive Surgery, C. H. Nagri Eye Hospital, Ahmedabad - 380 006, Gujarat
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/meajo.MEAJO_182_19

Rights and Permissions
   Abstract 


Purpose: To report the prevalence of keratoconus (KCN) in patients presenting for refractive surgery in western India.
METHODS: A cross-sectional, observational, retrospective study performed at a tertiary eye care center. A total of 2902 cases, aged 18–40 years who presented in the refractive surgery department between January 2014 and December 2018 were included. Records of all the included cases were reviewed. Patients showing KCN pattern on topography were noted and divided into KCN and KCN suspects. Annual and overall 5-year prevalence were calculated at 95% confidence interval (CI). Demographic details of KCN and non-KCN participants were compared.
RESULTS: Of the 2902 cases, 25 (0.86%) had clinical KCN and 22 (0.76%) were KCN suspects. The combined 5-year prevalence of all these 47 KCN cases was 1.61% (95% CI: 1.15%-2.07%), with an annual prevalence range of 0.97%–2.43%. The mean age of non-KCN cases was 24.60 ± 4.91 years and KCN cases was 24.62 ± 5.37 years (P = 0.98). Among the KCN cases, there were more females (30; 63.83%), and the gender ratio was significantly different than non-KCN cases (P = 0.004).
CONCLUSION: The prevalence of KCN in refractive surgery cases was 1.61% which is higher than those found in the western population and lower than those found in the Middle East (Saudi Arabia and Iran). Furthermore, topographic examination performed during the routine screening of patients for refractive surgery can be a useful tool to diagnose new cases of KCN in asymptomatic patients.

Keywords: Keratoconus, prevalence, refractive surgery


How to cite this article:
Shilpy N, Shah Z, Singh S, Purohit D. Prevalence of keratoconus in refractive surgery cases in Western India. Middle East Afr J Ophthalmol 2020;27:156-9

How to cite this URL:
Shilpy N, Shah Z, Singh S, Purohit D. Prevalence of keratoconus in refractive surgery cases in Western India. Middle East Afr J Ophthalmol [serial online] 2020 [cited 2021 Jan 18];27:156-9. Available from: http://www.meajo.org/text.asp?2020/27/3/156/299640




   Introduction Top


Keratoconus (KCN) is a bilateral, progressive, noninflammatory corneal disorder characterized by ectasia and thinning of the central or paracentral cornea.[1] Patients usually present with decrease in visual quality or quantity or both. There are well-defined biomicroscopic, ophthalmoscopic, and retinoscopic signs, but topography is the gold standard for diagnosis of early disease.[1]

Another area in ophthalmology where topography plays a key role is the field of refractive surgery.[2],[3] Aiming for a spectacle-free vision, the surgeon and the patient both have high expectations following the laser vision corrective procedures. To avoid the risk of postoperative complications and achieve a good visual outcome (early and late), proper patient selection is of paramount importance. Topography is an indispensable tool for preoperative workup and decision-making.[2],[3] Patients with topographic abnormalities suggestive of KCN or suspect KCN are excluded from the procedure, as these abnormalities increase the risk of postoperative corneal ectasia.[4]

The prevalence of KCN varies widely with geographical location and ranges from 0.0003% to 4%.[5],[6],[7],[8],[9],[10],[11] It also depends on the diagnostic method and criteria used in the study. The study done on KCN prevalence from India has reported a prevalence of 2.3% in general population.[7] Their study is not based on topography, and instead, they have used keratometry >48 diopters (D) as criteria for labeling as KCN. The paucity of data prompted us for this study which we conducted to find the prevalence of KCN in patients who presented for refractive surgery at a tertiary care center in western India.


   Methods Top


This was a cross-sectional, retrospective, observational study conducted at a tertiary eye care center in western India. Ethical clearance was obtained from the institutional review board (NHL Institutional Review Board), and the study adhered to the tenets of the Declaration of Helsinki. We included all individuals aged 18–40 years who presented in the refractive surgery department of our hospital from January 2014 to December 2018. Patients who had previously undergone any ocular surgery, those with any known ocular or systemic disorder, and pregnant or lactating females were excluded. A total of 2902 individuals were included in the study. Records of all these 2902 individuals were reviewed which included history, anterior and posterior segment examination, manifest and cycloplegic refraction with postmydriatic testing results, thinnest pachymetry, and topography. Contact lens users were asked to discontinue the lens use for 2 weeks before the examination. Pachymetry data were taken from Galilei dual Scheimpflug system (Ziemer Ophthalmic Systems AG, Port, Switzerland), and topography data were taken from  Atlas More Details 9000 Corneal Topography System, a Placido-based topographer (software version 3.0.0.39. Carl Zeiss Meditec AG, Jena, Germany).

Atlas topographer has optional software known as Pathfinder II Corneal Analysis Software that classifies the cornea into normal, abnormal, and pathologic based on anterior corneal topography. The software analyzes 12 different corneal parameters and compares them to a comprehensive clinical database that contains reference values for normal, KCN pattern, and myopic or hyperopic laser vision correction. KCN pattern category includes established KCN, suspect KCN, and pellucid marginal degeneration (PMD).

All those patients whose topography analysis by Pathfinder II showed a KCN pattern in either eye were noted and divided into clinical KCN and KCN suspects based on topographic and clinical findings. Patients who had at least one of the biomicroscopic signs consistent with KCN (Vogt's striae, Fleischer's ring, or corneal scarring), distorted keratometric mires, or distortion of the retinoscopic or ophthalmoscopic red reflex along with the topographic abnormalities were classified as clinical KCN. Others with a least one or more of the following signs: inferior or central steepening on topography with inferior-superior asymmetry ≥1.4 D, keratometry >48 D, corneal thinning corresponding to the area of steepening, distorted keratometric mires, or distortion of the retinoscopic or ophthalmoscopic red reflex, but without any biomicroscopic signs, were classified as KCN suspects. Patients with clinical KCN in one eye and suspect KCN in the other were kept in the clinical KCN group. Patients with isolated steep cornea or thinnest pachymetry <500 μwithout any KCN pattern on topography were not taken into consideration. The demographic details of all the patients were recorded.

Statistical analysis was done using SPSS software (version 20.0, SPSS Inc. Armonk, NY: IBM corp.). Quantitative data were analyzed using Student's t-test. P < 0.05 was considered statistically significant. The prevalence of KCN in patients for refractive surgery was calculated annually from 2014 to 2018 and overall for 5 years and assessed within 95% confidence interval (CI).


   Results Top


In our study, of a total of 2902 individuals who were included, 25 cases (0.86%; 95% CI: 0.52%–1.2%) had clinical KCN and 22 cases (0.76%; 95% CI: 0.44%–1.08%) were KCN suspects. Hence, the combined 5-year prevalence of all these 47 KCN cases (clinical and suspect) was 1.61% (95% CI: 1.15%–2.07%). The annual prevalence ranged from 0.97% in 2015 to 2.43% in 2017 [Table 1].
Table 1: Annual and overall 5-year prevalence of keratoconus in patients presenting for refractive surgery

Click here to view


The mean age of non-KCN cases was 24.60 ± 4.91 years and that of KCN cases was 24.62 ± 5.37 years (P = 0.98). Among the total KCN cases, there were 17 (36.17%) males and 30 (63.83%) females. The gender ratio was significantly different than non-KCN cases (P = 0.004) [Table 2].
Table 2: Age and gender distribution of nonkeratoconus cases and total keratoconus (clinical and suspect) cases

Click here to view



   Discussion Top


Topographic abnormalities such as KCN and suspect KCN are absolute contraindications for refractive surgery. Proper diagnosis of these cases is a must during evaluation of patients keen for spectacle-free vision. We conducted this study to find the prevalence of these cases in patients presenting for refractive surgery in India.

The incidence and prevalence of KCN varies with the geographical distribution. Studies have reported incidence ranging from 1.3 cases/100,000 in Denmark [12] to 22.3-24.9 cases/100,000 in Iran.[13] The prevalence of KCN also varies widely ranging from 0.3/100,000 (0.0003%) in Russia [5] to 4000/100,000 (4%) in Iran.[6] Countries with hotter climate such as Iran,[6] India,[7] and Lebanon [8] have reported higher prevalence than countries with cooler climate such as Denmark,[12] the United Kingdom,[9] the United States,[10] and The Netherlands.[11] A possible explanation could be the ultraviolet light-induced oxidative stress in hotter countries that increases the risk of KCN.

The prevalence of KCN in patients presenting for refractive surgery is reported to be higher than in the general population because these patients are often dissatisfied with glasses and contact lenses and seek refractive treatment. Studies from Saudi Arabia (KCN: 18.7% and suspect KCN: 17.5%)[14] and Yemen (KCN: 17.9% and suspect KCN: 10.4%)[15] have reported a much higher prevalence and incidence, respectively. Ambrósio and Klyce have reported a combined prevalence of 0.9% for KCN, KCN suspects, and PMD in the United States.[2] El-Sayed and Ali found an incidence of 1.7% for KCN and 2.1% for KCN suspects in Egypt.[16] In our study, the combined prevalence of all KCN cases was 1.61%, with 0.86% for clinical KCN and 0.76% for KCN suspects. The prevalence in our study is less than the studies on refractive surgery patients from Saudi Arabia and Yemen. This may be because of the fact that the mean age of KCN patients is younger in India as reported by Saini et al. (20.2 ± 6.4 years)[17] and Agrawal (20.1 ± 3.5 years),[18] and therefore, many cases of KCN would have been diagnosed at an earlier age (<18 years) because of visual symptoms. Another possible explanation of higher prevalence in those countries compared to India could be the increased incidence of consanguineous marriage in the Middle East countries. The lesser prevalence in our study compared to previous Indian study can be explained by the fact that the previous study has used only keratometry >48 D as a criterion for KCN which might have led to an overdiagnosis of KCN.[7] Furthermore, the age group is not similar to our study as they have included patients aged 30 years and above.

The mean age of KCN patients in our study was 24.62 ± 5.37 years. This was similar to the previous studies from India.[17],[18] There was no significant difference in age between the KCN and non-KCN cases. In our study, we found a female preponderance in the KCN cases with 63.83% of females. Previous studies have shown varied results with few reporting greater prevalence in females [19] and few in males.[9],[20],[21] Some studies have reported no gender predisposition.[10],[22] Studies from India also report male preponderance in some [23],[24] and female preponderance in others.[17],[18] The female preponderance in our study could be because of the small number of KCN patients.


   Conclusion Top


We found a KCN prevalence of 1.61% in refractive surgery population in western India. This prevalence is higher than that found in the western world and lower than that found in the countries in the Middle East (Saudi Arabia and Iran). Furthermore, topographic examination performed during the routine screening of patients for refractive surgery can be a useful tool to diagnose new cases of KCN in asymptomatic patients. Further studies with a larger sample size can be done in the future.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Rabinowitz YS. Keratoconus. Surv Ophthalmol 1998;42:297-319.  Back to cited text no. 1
    
2.
Ambrósio R Jr., Klyce SD, Wilson SE Corneal topographic and pachymetric screening of keratorefractive patients. J Refract Surg 2003;19:24-9.  Back to cited text no. 2
    
3.
Wilson SE, Klyce SD. Screening for corneal topographic abnormalities before refractive surgery. Ophthalmology 1994;101:147-52.  Back to cited text no. 3
    
4.
Randleman JB, Trattler WB, Stulting RD. Validation of the Ectasia Risk Score System for preoperative laser in situ keratomileusis screening. Am J Ophthalmol 2008;145:813-8.  Back to cited text no. 4
    
5.
Gorskova EN, Sevost'ianov EN. Epidemiology of keratoconus in the Urals. Vestn Oftalmol 1998;114:38-40.  Back to cited text no. 5
    
6.
Hashemi H, Heydarian S, Yekta A, Ostadimoghaddam H, Aghamirsalim M, Derakhshan A, et al. High prevalence and familial aggregation of keratoconus in an Iranian rural population: A population-based study. Ophthalmic Physiol Opt 2018;38:447-55.  Back to cited text no. 6
    
7.
Jonas JB, Nangia V, Matin A, Kulkarni M, Bhojwani K. Prevalence and associations of keratoconus in rural Maharashtra in central India: The central India eye and medical study. Am J Ophthalmol 2009;148:760-5.  Back to cited text no. 7
    
8.
Waked N, Fayad AM, Fadlallah A, El Rami H. Keratoconus screening in a Lebanese students' population. J Fr Ophtalmol 2012;35:23-9.  Back to cited text no. 8
    
9.
Pearson AR, Soneji B, Sarvananthan N, Sandford-Smith JH. Does ethnic origin influence the incidence or severity of keratoconus? Eye (Lond) 2000;14 (Pt 4):625-8.  Back to cited text no. 9
    
10.
Kennedy RH, Bourne WM, Dyer JA. A 48-year clinical and epidemiologic study of keratoconus. Am J Ophthalmol 1986;101:267-73.  Back to cited text no. 10
    
11.
Godefrooij DA, de Wit GA, Uiterwaal CS, Imhof SM, Wisse RP. Age-specific incidence and prevalence of keratoconus: A nationwide registration study. Am J Ophthalmol 2017;175:169-72.  Back to cited text no. 11
    
12.
Nielsen K, Hjortdal J, Aagaard Nohr E, Ehlers N. Incidence and prevalence of keratoconus in Denmark. Acta Ophthalmol Scand 2007;85:890-2.  Back to cited text no. 12
    
13.
Ziaei H, Jafarinasab MR, Javadi MA, Karimian F, Poorsalman H, Mahdavi M, et al. Epidemiology of keratoconus in an Iranian population. Cornea 2012;31:1044-7.  Back to cited text no. 13
    
14.
Al-Amri AM. Prevalence of keratoconus in a refractive surgery population. J Ophthalmol 2018;2018:5983530.  Back to cited text no. 14
    
15.
Bamashmus M, Saleh MF, Abdulrahman M, Al-Kershy N. Reasons for not performing LASIK in refractive surgery candidates in Yemen. Eur J Ophthalmol 2010;20:858-64.  Back to cited text no. 15
    
16.
El-Sayed OA, Ali M. Incidence and indices of keratoconus in patients presenting for LASIK in Egypt. Int J Keratoconus Ectatic Corneal Dis 2017;6:17-22.  Back to cited text no. 16
    
17.
Saini JS, Saroha V, Singh P, Sukhija JS, Jain AK. Keratoconus in Asian eyes at a tertiary eye care facility. Clin Exp Optom 2004;87:97-101.  Back to cited text no. 17
    
18.
Agrawal VB. Characteristics of keratoconus patients at a tertiary eye center in India. J Ophthalmic Vis Res 2011;6:87-91.  Back to cited text no. 18
  [Full text]  
19.
Krachmer JH, Feder RS, Belin MW. Keratoconus and related noninflammatory corneal thinning disorders. Surv Ophthalmol 1984;28:293-322.  Back to cited text no. 19
    
20.
Owens H, Gamble G. A profile of keratoconus in New Zealand. Cornea 2003;22:122-5.  Back to cited text no. 20
    
21.
Wagner H, Barr JT, Zadnik K. Collaborative longitudinal evaluation of keratoconus (CLEK) study: Methods and findings to date. Cont Lens Anterior Eye 2007;30:223-32.  Back to cited text no. 21
    
22.
Li X, Rabinowitz YS, Rasheed K, Yang H. Longitudinal study of the normal eyes in unilateral keratoconus patients. Ophthalmology 2004;111:440-6.  Back to cited text no. 22
    
23.
Fatima T, Acharya MC, Mathur U, Barua P. Demographic profile and visual rehabilitation of patients with keratoconus attending contact lens clinic at a tertiary eye care centre. Cont Lens Anterior Eye 2010;33:19-22.  Back to cited text no. 23
    
24.
Sharma R, Titiyal JS, Prakash G, Sharma N, Tandon R, Vajpayee RB. Clinical profile and risk factors for keratoplasty and development of hydrops in North Indian patients with keratoconus. Cornea 2009;28:367-70.  Back to cited text no. 24
    



 
 
    Tables

  [Table 1], [Table 2]



 

Top
  
 
  Search
 
    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
    Abstract
   Introduction
   Methods
   Results
   Discussion
   Conclusion
    References
    Article Tables

 Article Access Statistics
    Viewed1669    
    Printed88    
    Emailed0    
    PDF Downloaded50    
    Comments [Add]    

Recommend this journal