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Year : 2004  |  Volume : 22  |  Issue : 4  |  Page : 226-230

Acanthamoeba keratitis - A six year epidemiological review from a tertiary care eye hospital in South India

Department of Microbiology, Aravind Eye Care System, Aravind Eye Hospital and Post Graduate Institute of Ophthalmology, Avinashi Road, Coimbatore- 641 014, India

Date of Submission20-Mar-2004
Date of Acceptance02-Jul-2004

Correspondence Address:
Department of Microbiology, Aravind Eye Care System, Aravind Eye Hospital and Post Graduate Institute of Ophthalmology, Avinashi Road, Coimbatore- 641 014, India

 ~ Abstract 

PURPOSE: This study analyses the prevalence, demography, predisposing factors and seasonal variation of Acanthamoeba keratitis. METHODS: A retrospective review of all cases presenting with keratitis at the cornea clinic, Aravind Eye Hospital, Coimbatore, from August 1997 to July 2003, was done for screening patients with a provisional diagnosis of Acanthamoeba keratitis. Their records were further analyzed for microbiological details. Cases with culture proven Acanthamoeba keratitis were included for epidemiological analysis. RESULTS: From a total of 4519 patients who attended cornea clinic 32 (33 eyes) patients were confirmed to be positive for Acanthamoeba keratitis. Twenty cases (62.5%) were males. Majority (18; 54.2%) of the Acanthamoeba keratitis eyes reported corneal trauma by solid objects. No peak period was observed in a year, as the number of cases was almost uniform in all months. CONCLUSION: This study indicates the increasing prevalence of Acanthamoeba keratitis among non-contact lens users in this region during the 6-year period.

How to cite this article:
Manikandan P, Bhaskar M, Revathy R, John R K, Narendran V, Panneerselvam K. Acanthamoeba keratitis - A six year epidemiological review from a tertiary care eye hospital in South India. Indian J Med Microbiol 2004;22:226-30

How to cite this URL:
Manikandan P, Bhaskar M, Revathy R, John R K, Narendran V, Panneerselvam K. Acanthamoeba keratitis - A six year epidemiological review from a tertiary care eye hospital in South India. Indian J Med Microbiol [serial online] 2004 [cited 2021 Jan 23];22:226-30. Available from:

Acanthamoeba species are ubiquitous, free-living protozoan parasites that can be isolated from diverse habitats like soil, stagnant water and fresh water ponds etc.[1] They can infect immunocompromised as well as healthy persons. Keratitis is the most common human infection caused by Acanthamoeba. Acanthamoeba keratitis is severe, progressive and sight threatening infection of cornea. Even after improved diagnostic techniques and applying novel treatment modalities Acanthamoeba keratitis accounts for profound morbidity and significant loss in visual acuity in about 16% of infected corneal ulcer patients.[2]
Though various risk factors are being quoted, none of them received due attention except "contact lens wearers" as this is the single most important risk factor deciding the prevalence of Acanthamoeba keratitis in developed countries. They are associated with 75 - 93% cases of Acanthamoeba keratitis in various studies.[3],[4] In developing countries the major risk factors differ from those found in developed countries, as there is no widespread use of contact lenses in these countries. Now, it has been identified that even non-contact lens wearers are prone to this infection.[5],[6],[7],[8] Therefore, this disease is gaining momentum like other common microbial eye infections. Fall of dust particles, trauma due to vegetable matter, contact with contaminated water etc., have been found to be the predominant risk factors of Acanthamoeba keratitis.[9],[10]
Against this background, we have analyzed the prevalence data of patients who attended the cornea clinic of Aravind Eye Hospital, Coimbatore, with the clinical diagnosis and culture confirmation of Acanthamoeba keratitis for a period of six years spanning from August 1997 to July 2003. The conventional microbiological techniques such as microscopic analysis and cultural methods have been identified to be the easier methods of diagnosing this infection. The major objective of this study is to analyze the epidemiological details of Acanthamoeba keratitis, which may be of help in early diagnosis leading to effective management.

 ~ Materials and Methods Top

A retrospective review of all cases who presented with keratitis at the cornea clinic Aravind Eye Hospital, Coimbatore, from August 1997 to July 2003, was done for screening patients with a provisional diagnosis of Acanthamoeba keratitis. Their records were further analyzed for microbiological details. Cases with culture proven Acanthamoeba keratitis were included for epidemiological analysis. Besides demographic details (age, sex), occupation, predisposing factors and seasonal variation were also recorded and analyzed. Microbiological investigations were noted from case records of patients. The corneal scrapings of all patients were subjected to Gram stain, Giemsa stain and 10% KOH wet mount. Culture of specimens involved inoculation of non-nutrient agar seeded with  Escherichia More Details coli. Culture plates showing amoebal migration tracks and amoebal trophozoites or cysts were considered to be positive for Acanthamoeba keratitis. Specimens were also inoculated in to sheep blood agar, chocolate agar, thioglycollate broth, brain-heart infusion broth, potato dextrose agar for isolation of bacteria and fungi.[14] In addition to these, the details of presenting complaints, time of diagnosis, treatment protocol and follow up details were analyzed. Once confirmed as Acanthamoeba keratitis, the treatment was initiated with polyhexamethylene biguanide 0.02% drops hourly for three days, 2 hourly for one week and 4 to 6 hourly during subsequent weeks. Flucomet drops were instilled in 25 cases. Ciprofloxacin, cefotaxime and ofloxacin were also used in ten, two and three cases respectively. Cyclopegics (homide drops) and analgesics were used whenever indicated.

 ~ Results Top

During the study period, 4519 patients (4541 eyes) underwent corneal scraping in one or both (0.48%) eyes. On processing, Acanthamoeba grew in 33 (32 cases) cultures among 3008 culture positive scrapings. (prevalence - 1.1%; 95% CI: 0.8-0.15). Five cases (15.1%) had coexisting microorganisms [Table - 1].
Among the 32 cases 20 (62.5%) were males. Majority (10, 31.2%) of the cases were in the 31-40 years age group [Table - 2]. No case was reported among children below 10 years of age. Half of the cases (16, 50.0%) were agricultural farmers and 8 (25.0%) of them were construction workers. Injury by an object was the major predisposing factor (18, 54.2%) [Table - 3]. The others had washed the eyes with stagnant water and had applied medications. The clinical features of the cases are described in [Table - 4]. The number of cases were more or less the same through out the year [Table - 5].
The keratitis (central/subtotal) was the major presenting feature in all cases [Table - 4]. One patient presented with bilateral keratitis and features of Reiter's syndrome. The interval between onset of symptoms and diagnosis ranged from 2 days to 90 days. Medical treatment was initiated in all patients. Complete healing of the corneal ulcer was recorded in 13 patients (14 eyes; 39.3%) with visual acuity ranging from 6/6 to 6/60. One patient regained full vision (6/9) after keratoplasty followed by cataract surgery. Total evisceration was done on a diabetic patient who had a secondary infection with unidentified hyaline fungus. Prior to diagnosing Acanthamoeba keratitis 6(18.1%) patients were treated with antibiotic. One patient (3.1%) was treated with steroid and 2(6.2%) were treated with antimycotics. Combination of antivirals and steroid treatment was given to 7(21.2%) patients. Follow up was not available for 9(27.2%) patients.

 ~ Discussion Top

Acanthamoeba keratitis is a growing clinical problem both in developed and developing countries. Indian studies show that prevalence rate varies from 1 to 3% among culture positive corneal ulcers.[9],[10] The prevalence is on the rise due to increased awareness of its clinical features and easy diagnostic techniques. The isolation rate in our hospital is 1.1% (33 eyes) among clinically suspected cases, which is similar to other Indian studies on Acanthamoeba keratitis.[5],[10],[11] This study shows increasing prevalence of Acanthamoeba keratitis over the years (from 3 cases in 1997 to 10 cases in 2001 and 8 cases in 2002). This may be due to increased awareness and increased number of specimens processed in our laboratory or due to an actual increase in the number of keratitis cases caused by Acanthamoeba. Illingworth et al reported an increase in the prevalence of Acanthamoeba keratitis in recent times.[12] They reported an increase from three (before 1990) to 21 cases (1990-1995) in Acanthamoeba keratitis prevalence, out of which 11 cases were reported after January 1994. Jeanette et al also reported a similar increase in prevalence in their study.[3] Most of the previous studies have indicated a strong association between contact lens wear and Acanthamoeba keratitis.[3],[4],[12] In contrast to this, the clinical history of all 32 cases in this study shows that either corneal injury (42.4%) or fall of foreign body (24.2%) from various sources were the predisposing factors and no person using contact lens was either suspected or diagnosed as Acanthamoeba keratitis. This can be considered as one of the significant findings of the study revealing the increasing occurrence of this disease at a significant rate among the non contact lens users. This has also been indicated in a study conducted by Srinivasan et al from Madurai analyzing various risk factors of Acanthamoeba keratitis.[6],[7] The marked absence of Acanthamoeba keratitis even among contact lens users attending our cornea clinic may be due to the increased awareness in handling the contact lens. They use commercial contact lens solutions instead of home made saline solution and do not have the habit of swimming with contact lens as seen in western countries.
The distribution of Acanthamoeba keratitis between males and females was not equal. Nearly, two third (62.5%) of the 32 cases were males and the rest were females. However, the exact reason behind male preponderance is not known. Males between 31 and 50 years and females from 31 to 60 years have been found to be more prone to Acanthamoeba keratitis. This is usually the working group and most of them are agriculture workers who are exposed to wet soil and stick injuries. Instead of seeking medical attention they resort to washing eyes with probably stagnant water. In a similar geographical background the bacterial and fungal keratitis occur among people who are non-agriculture workers and who are above 50 years of age as described by Bharathi et al.[13] Radford et al had described in their study a significant increase in prevalence of Acanthamoeba keratitis during July to October.[4] In contrast to this we have not found any seasonal variation in our study. The prevalence is more or less same through out the year.
In our study we have found no distinctive clinical feature suggestive of Acanthamoeba keratitis. In most of the cases the features mimic viral keratitis and empirical treatment was started with analgesics and antivirals like acyclovir. This may also be a reason for delay in diagnosis in earlier period of our study. The delay in diagnosis did not lead to complications in Acanthamoeba keratitis. Evisceration was reported in one diabetic patient who had a concurrent fungal infection. Chronic course without major complications is an important feature, which may distinguish Acanthamoeba keratitis from other suppurative keratitis.
From our study, it is clear that Acanthamoeba keratitis is uncommon when the risk factors are absent and it is commonly seen among people who are exposed to Acanthamoeba through various predisposing factors. A knowledge of epidemiology and early diagnosis may prove vital for effective management of Acanthamoeba keratitis. Although the clinical resolution and reduction of subjective symptoms are achieved in some cases with appropriate management, the vision outcome in others after treatment was not improved markedly owing to scar formation. Hence, prevention of Acanthamoeba keratitis by creating awareness about predisposing factors among public, is the prime responsibility of clinicians and microbiologists. 

 ~ References Top

1.Acanthamoeba keratitis, chapter 78. In: Ocular infection and immunity. Pepose JS, Holland HN, Wilhelmus KR, Eds. (Mosby) 1996:1062-1071.  Back to cited text no. 1    
2.Duguid IGM, Dart JK, Morlet N, Allan BD, Matheson M, Ficker L, Tuft S. Outcome of Acanthamoeba keratitis treated with Polyhexamethyl Biguanide and Propamidine. Ophthalmol 1997;104:1587-1592.  Back to cited text no. 2    
3.Jeanette JS, Theodore MB, Visvesvara GS. The epidemiology of Acanthamoeba keratitis in the United States. Am J Ophthalmol 1989;107:331- 336.  Back to cited text no. 3    
4.Cherry FR, Ordan JL, John KG. Acanthamoeba keratitis: multicenter survey in England 1992-6. Br J Ophthalmol 1998;82:1387-1392.   Back to cited text no. 4    
5.Sharma S, Garg P, Rao GN. Patient characteristics, diagnosis, and treatment of non-contact lens related Acanthamoeba keratitis. Br J Ophthalmol 2000;84:1103-1108.  Back to cited text no. 5    
6.Srinivasan M, Sanghamitra B, Celine G, Praveen KN. Non contact lens related Acanthamoeba keratitis at a tertiary eye care center in south India: Implications for eye care programs in the region. Med Sci Monit 2003;9(4):177-181.  Back to cited text no. 6    
7.Sharma S, Srinivasan M, Celine G. Acanthamoeba keratitis in non-contact lens wearers. Arch Ophthalmol 1990;108:676-678.  Back to cited text no. 7    
8.Davamani F, Gnanaselvan J, Anandakannan K, Sridhar N, Sundararaj T. Studies on the prevalence of Acanthamoeba keratitis in and around Chennai. Indian J Med Microbiol 1998;16(4):152-153.  Back to cited text no. 8    
9.Radford CF, Minassion DC, Dart JKG. Acanthamoeba keratitis in England and Wales: incidence, outcome, and risk factors. Br J Ophthalmol 2002;86:536-542.  Back to cited text no. 9    
10.Kunimoto DY, Sharma S, Garg P, Gopinathan U, Miller D, Rao GN. Corneal ulceration in the elderly in Hyderabad, south India. Br J Ophthalmol 2000;84:54-59.  Back to cited text no. 10    
11.Srinivasn M, Gonazales CA, George C, Cevallos V, Mascarenhas JM, Asokan B, Wilkins J, Smolin G, Witcher JP. Epidemiology and aetiological diagnosis of corneal ulceration in Madurai, south India. Br J Ophthalmol 1997;8:965-971.   Back to cited text no. 11    
12.Illingworth CD, Cook SD, Karabatsas CH, Easty DL. Acanthamoeba keratitis: risk factors and outcome. Br J Ophthalmol 1995;79:1078-1082.  Back to cited text no. 12    
13.Bharathi MJ, Ramakrishnan R, Vasu S, Meenakshi R, Shivkumar C, Palaniappan R. Epidemiology of bacterial keratitis in a referral center in south India. Indian J Med Microbiol 2003;21(4):239-245.   Back to cited text no. 13    
14.Sharma S, Athmanathan S. Diagnostic procedures in infectious keratitis. In: Diagnostic Procedure in Ophthalmology, 1st ed. Nema HV, ed. (Jaypee brothers Medical Publishers Pvt. Ltd.) 2000, Vol. I: 232-253.  Back to cited text no. 14    
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