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Analysis of the risk factors predisposing to fungal, bacterial & Acanthamoeba keratitis in south India.

Corneal diseases, especially infective keratitis, are a major cause of vision loss and blindness second only to cataract (1). A study from south India reported that the incidence of corneal infections in India is almost 10 times that reported in the United States (2). This is likely to be the case in other developing countries as well (3-5).

Infective keratitis may be caused by bacteria, fungi, protozoa and virus, and the spectrum of microbial pathogens causing keratitis varies according to the geographical locations and climate (6-9). Infective keratitis rarely occur in normal eyes without any predisposing factors. The ocular surface is normally protected from microbial invasion through an intricate biochemical and anatomic relationship between the cornea, conjunctiva, lacrimal secretory apparatus and precorneal tear film, and the eye lids. Any disruption of the same may results in less effective defense against infection and such risk factors may vary with occupation. An association has been shown between the type of risk factor and the microbial aetiology for infection (10). Corneal injury due to vegetative matter predispose mainly to fungal keratitis (8), while use of contact lenses and other nontraumatic risk factors to bacterial keratitis (11,12). Thus, the analysis of such associated risk factors and the isolated microbial aetiology will help in understanding the relationship between risk factors and microbial keratitis, and is essential for initiation of empirical antimicrobial therapy with subjective interpretation of presenting clinical features for practicing ophthalmologist. The purpose of this study was to identify the specific risk factor predisposing to infective keratitis (non viral) and an attempt was also made to determine the association between the risk factors identified and the microbial aetiology of the infective keratitis (non viral) in south India.

Material & Methods

Patients: This retrospective study included all patients with clinically diagnosed infective keratitis (non viral) presenting at Aravind Eye Hospital & Postgraduate Institute of Ophthalmology, Tirunelveli, Tamil Nadu, India from September 1999 to September2002. Infective keratitis was defined as a suppurative infection of the corneal stroma with an associated overlaying epithelial defect and sign of inflammation, and is characterized by the presence of a white or yellowish stromal infiltrate or infiltrates with an associated epithelial defect, with or without hypopyon (8,9,13) All patients with infective keratitis presenting to this referral centre undergo detailed investigations that include: (i) the documentation of the demographic features, duration of symptoms, therapy received prior to presentation and use of traditional eye medicines, (ii) information pertaining to the predisposing factors: history of injury, injurious agents, associated ocular diseases, associated ocular conditions, use of contact lens (CL), use of topical steroids and presence of systemic diseases, (iii) ocular examination using a slit-lamp biomicroscope, and (iv) microbiologic workup includes direct microscopy and culture of corneal scrapes (8,9,13). A total of 12, 644 new cases of corneal ulcers were referred to the study centre during the study period, of which 7057 patients were clinically diagnosed as viral keratitis, 2292 patients were diagnosed as non infectious corneal inflammation and the remaining 3295 patients were clinically diagnosed as infective keratitis (non viral) and were enrolled in the study (Table I).

Clinical procedures: After detailed ocular examination, using standard techniques (9,13,14), corneal scrape was performed under magnification of a slit-lamp or operating microscope following instillation of 0.5 per cent proparacaine hydrochloride (Aurolab, Madurai, India) by using flame sterilized Kimura's spatula or a sterile Bard-Parker blade #15. The material obtained was initially smeared onto clean sterile labelled glass slides for 10 per cent KOH wet mount, Gramstain, Giemsa-stain and Kinyoun's acid-fast stain for suscepted actinomycete keratitis. The material obtained by next scrape was inoculated directly onto the surface of solid media such as sheep's blood agar, chocolate agar, Sabouraud's dextrose agar, potato dextrose agar, non-nutrient agar in rows of C- shaped streaks and also inoculated into the depth of liquid media such as brain heart infusion broth and thioglycollate medium.

Laboratory procedures: All inoculated media were incubated aerobically. The inoculated Sabouraud's dextrose agar was incubated at 27[degrees]C, examined daily, and discarded at 3 wk if no growth was seen. The inoculated blood agar, chocolate agar, thioglycollate broth, brain heart infusion broth were incubated at 37[degrees]C, examined daily, and discarded at 7 days if growth was not seen. The inoculated non nutrient agar plates were incubated at 37[degrees]C after overlaying with Escherichia coli broth culture and were examined daily for the presence of Acanthamoeba species and discarded at 3 wk, if there were no signs of growth. The numbers of colonies were counted, and the numbers per C streak and the number of streak yielding growth were recorded. The positive bacterial growth was categorized as scanty (if the number of colonies are [less than or equal to] 10), light or 1+ growth (if growth on half of inoculum), moderate or 2+ (if growth on half of inoculum but all streaks) and heavy or 3+ (if growth on all inoculum) (13,14). Microbial cultures were considered significant if growth of the same organisms was demonstrated on more than one solid phase medium, and/or if growth of one medium was consistent with direct microscopy findings (i.e. appropriate staining and morphology with Gram stain). The isolated bacterial strains were identified by using standard biochemical tests and fungal strains were by macroscopic observation of fungal colonies and microscopic identification of conidia and sporangiospores in Lactophenol Cotton Blue staining method (15,16). All culture media, biochemical test reagents and stains utilized in this study were brought from Hi-media Laboratories Private Limited, Mumbai, India.

Analysis of data: Statistical software, STATA 8.1, (Stata Corporation, Dexas) was used for statistical analysis. Correlation between the microbial aetiology and the identified risk factors were determined. Pearson's chi-square test and Fisher exact test were used for analysis and P<0.05 was considered to be statistically significant.

Results

Microbiological findings: Of the 12, 644 new cases of corneal ulcers referred to the study centre, 3295 patients were clinically diagnosed as infective keratitis (non viral). Of these 1138 (34.5%) patients had fungal growth alone, 1066 (32.4%) had bacterial growth alone, 33 (1%) had Acanthamoeba growth alone, 83 (2.5%) had mixed microbial growth and the remaining 975 (29.6%) had no growth (Table I). A total of 1226 fungal isolates were recovered, Fusarium spp. (41.7%) followed by Aspergillus spp. (24.9%) were found to be the predominant fungal pathogens causing corneal infection (Table II). A total of 1216 bacterial pathogens Streptococcus pneumoniae (36%) followed by Pseudomonas spp. 19.7%) and coagulase negative staphylococci (18.3%) were found to be the predominant bacterial pathogens causing cornea infection (Table II). Pseudomonas aeruginosa was more frequently isolated from corneal scrapes obtained from CL wears than other microorganisms in this study (P<0.0001) (OR: 11.54; 95% CI: 5.81-22.92).

Predisposing risk factors: Corneal injury (71.5%) was identified as the predominant predisposing factor followed by co-existing ocular diseases (26.7%) and the association between corneal injury and culture-proven microbial keratitis was significant (P<0.0001)(OR:70.0; 95% CI:69.0-72.0). Corneal injury predisposing to fungal keratitis (91.9%; 1046 of 1138) was significantly higher, compared to other predisposing risk factors (8.1%; 92 of 1046) (P<0.0001) (OR: 73.5; 95% CI: 61.3-98.5). Corneal injury with vegetative matter (61.2%) resulting in fungal keratitis was significantly (P<0.0001) (OR: 15.73; 95% CI: 12.7-19.49) higher than fungal keratitis due to other traumatizing agents (30.8%). Co-existing ocular diseases predisposing to bacterial keratitis were identified in 724 (68%) patients, compared to other predisposing risk factors in 342(32%) patients and the difference was statistically significant (P<0.0001) (OR:33.31; 95% CI:26.98-41.12). Bacterial pathogens alone were recovered from all 35 patients with contact lens associated keratitis (100%). A history of corneal injury was recorded in 300 (28.1%) patients with bacterial keratitis and the percentage of patients who reported a history of corneal injury with sand/ soil/ stone/ dirt (19.8%) was significantly higher than the percentage of patients reporting injury due to other traumatizing agents (8.4%) (P<0.0001) (OR: 6.07; 95% CI:4.7-7.83). All 33 culture-proven Acanthamoeba keratitis had a history of corneal injury and the association between corneal injury and Acanthamoeba keratitis was significant (P<0.0001). Patients who reported a history of corneal injury with mud (84.6%) was significantly higher than the patients reporting injury due to other traumatizing agents (15.2%) in Acanthamoeba keratitis (P<0.0001) (OR: 16.52; 95% CI: 6.35-42.99). Corneal ulceration associated with contact lenses usage was documented in 35 (1.1%) patients, of which 32 had corneal infection in one eye and remaining 3 had infection in both eyes, and thus a total of 38 (1.2%) of 3298 eyes had corneal ulceration due to use of contact lenses (Table III).

Co-existing ocular diseases were frequently documented among patients older than 50 yr (78.3%; 687 of 878), compared to the patients younger than 51 yr (21.8%; 191 of 878) and the difference was statistically significant (P<0.0001) (OR: 27.0; 95% CI: 25.0-28.0). While a history of corneal injury was frequently recorded among patients younger than 51 yr (89.7%: 1983 of 2210), compared to those aged more than 50 yr (34.4%; 373 of 1085) (P<0.0001) (OR:72.0; 95% CI:70.0-73.0) (Table IV), co-existing ocular diseases predisposing to bacterial keratitis were significantly higher among patients more than 50 yr (93.4%; 604 of 647) of age than those younger than 50 yr (28.6%; 120 of 419) (P<0.0001) (OR:35.0; 95% CI:24.06-50.92). Corneal injury predisposing to fungal keratitis was significantly higher among patients less than 51 yr (98.2%; 912 of 929) of age as compared to corneal injury predisposing to fungal keratitis among patients those more than 50 yr (64.1%; 134 of 209) (P<0.0001) (OR:30.0; 95% CI: 20.0-60.0).

Co-existing ocular diseases predisposing to bacterial keratitis were frequently recorded among non agricultural workers (84.3%; 522 of 619), compared to agricultural workers (45.2%; 202 of 447) and the difference was statistically significant (P<0.0001) (OR: 65.3; 95% CI: 49.0-86.9). History of corneal injury predisposing to fungal keratitis was frequently recorded among agricultural worker (95.3%; 707 of 742), compared to non-agricultural workers (P<0.0001) (OR: 29.0; 95% CI: 19.0-46.0) (Table V). Of the 1066 bacterial keratitis, 571 (54%) patients were from rural area and 495 (46%) from urban area, whereas in case of fungal keratitis, of the 1138, 917 (80.6%) were from rural area and the remaining 221 (19.4%) from urban areas. Among Acanthamoeba keratitis all 33 (100%) came from rural areas.

Discussion

In south India, corneal injury was an overwhelming risk factor followed by chronic dacryocystitis, spheroidal degeneration of the cornea, blepharitis, conjunctivitis, pre-existing viral keratitis, bullous keratopathy, dry eyes and exposure keratitis (8,9,17). In this study also, corneal injury was responsible for 71.5 per cent cases of corneal ulcer as a risk factor. This figure is supported by a higher incidence of microbial keratitis following corneal injury in developing countries (65.4% in south India (9), 82.9% in East India (18), 55 per cent in north India (19), 52.8% in Nepal (3), 39.2 per cent in Ghana5 and 23.8 in Taiwan4) as against 8.33 per cent in Phailadelphia (20), 23.5 per cent in New Zealand (21), 15 per cent in Perth (22), and 3.7 per cent in Sydney (23). This difference is primarily due to differences in occupation, agriculture being the primary occupation in the developing countries (9).

In this study corneal trauma was found to be the major risk factor for the development of fungal and Acanthamoeba keratitis. In case of Acanthamoeba keratitis, all 33 culture proven cases had history of corneal trauma with mud (injury with wet sand) or vegetative matter. Contact lens wear does not emerge as an important risk factor, though it is a predominant cause for Acanthamoeba keratitis in developed countries (24). This difference can be attributed to the difference in prevalence of contact lens wear between developed (24) and developing countries (25), and the care of CL and environmental factors (7,24). History of corneal injury was noted in 92 per cent cases of fungal keratitis, the most common agent being vegetative matter. This is consistent with similar predominance of corneal injury reported in Hyderabad (54%) (26), Calcutta (72%) (27), Sri Lanka (55%) (28), Florida (44%) (29) and Singapore (55%) (12).

In contrast, corneal injury was a predisposing factor in 28 per cent of all bacterial keratitis, consistent with studies in Paris (15%, third most common factor) (12), Switzerland (11) and Hong Kong (7), Co-existing ocular disease predisposing to corneal ulceration accounted for 26 per cent of all cases, 82.5 per cent being bacterial infection and 9 per cent fungal infection. This is consistent with the earlier studies (12).

Contact lenses predisposed to 1 per cent of all corneal ulcers evaluated in this study and all cases had bacterial keratitis. This is in contrast to the predisposition to Acanthamoeba keratitis in contact lens wearers in developed countries (6). In developing countries predisposition to bacterial keratitis may be attributed to bacterial contamination and formation of slimy bio-film on the posterior surface of the contact lens leading to spoilage of CL and risk of subsequent bacterial infection (24). Topical steroids predisposed to microbial keratitis in 26 cases, of whom 50 per cent had fungal aetiology. Other studies reported 10-25 per cent cases of mycotic keratitis due to topical steroid usage (30). Diabetes mellitus was identified as the predominant systemic disease associated with fungal and bacterial keratitis similar to a study from Hyderabad (26). However, several other large series of mycotic keratitis reported from tropical countries do not support diabetes as a risk factor for the development of mycotic keratitis (9).

Fungal and Acanthamoeba keratitis was found to be higher in the younger age group while bacterial keratitis was frequent among elderly patients. This can be explained by more chances of corneal injury in the young as an occupational hazard and more chances of co-existing ocular diseases in the elder population. Also, fungal Acanthamoeba keratits were more common in agricultural workers and rural population as against bacterial keratitis among non-agricultural workers. This can also be explained by the greater incidence of vegetative corneal injury among the young rural population engaged in agriculture thus predisposing to fungal ulceration and Acanthamoeba keratits.

In conclusion, our study highlighted the fact that corneal injury was the principal risk factor for fungal and Acanthamoeba keratitis, while co-existing ocular diseases and CL wears, the major risk factors for bacterial keratitis. Corneal injury with vegetative matter was more often associated with fungal keratits and injury with mud with Acanthamoeba keratits.

Acknowledgment

The authors acknowledge Ms. V. Nithya, and P. R. Viji, (Microbiology Research Centre, Aravind Eye Hospital & Postgraduate Institute of Ophthalmology, Tirunelveli, India) and Ms. R. Mahalakshmi, Lions Aravind Institute of Community Ophthalmology, Madurai, India for their laboratory and statistical assistance.

Received June 2, 2008

References

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Reprint requests: Dr Jayahar Bharathi, Microbiology Research Centre, Aravind Eye Hospital & Postgraduate Institute of Ophthalmology Tirunelveli 627 001, Tamil Nadu, India e-mail: jayahar@tvl.aravind.org

M. Jayahar Bharathi, R. Ramakrishnan, R. Meenakshi, C. Shivakumar & D. Lional Raj

Microbiology Research Centre, Aravind Eye Hospital & Postgraduate Institute of Ophthalmology, Tirunelveli, India
Table I. Microbial growth pattern of corneal scrapes obtained from
3295 consecutive patients with infective keratitis (non-viral) in
south India

Microbial growth pattern Number of eyes
 (%)

Pure fungal growth 1138 (34.5)
(single species of fungi) 1132 (34.4)
(two species of fungi) 6 (0.2)

Pure bacterial growth 1066 (32.4)
(single species of bacteria) 1004 (30.5)
(two species of bacteria) 62 (1.9)

Pure protozoa (Acanthamoeba) growth 33 (1)

Mixed fungal and bacterial growth) 81 (2.5)
(single species of fungi and
single species of bacteria)

Mixed Acanthamoeba and single 1 (0.03)
species of fungal growth

Mixed Acanthamoeba and single 1 (0.03)
species of bacterial growth

Patients with microbial keratitis 2320 (70.4)
showed positive cultures

Patients with microbial keratitis 975 (29.6)
showed negative cultures

Table II. Bacterial and fungal pathogens recovered from corneal
scrapes of 2290 eyes (bacteria from 1151 * eyes and fungi from
1220 ** eyes) with infective keratitis (non-viral) treated at
a tertiary eye care referral centre in south India

Name of isolates Total
 number of
 isolates

Total number of bacterial isolates recovered 1216
(i) Gram-positive cocci 780
 Streptococcus pneumoniae 438
 Streptococcus epidermidis 222
 Staphylococcus aureus 46
 Miccrococcus spp. 6
 Alpha haemolytic streptococci 53
 Beta haemolytic streptococci 6
 Non haemolytic streptococci 9
(ii) Gram positive bacilli 57
 Bacillus spp. 27
 Corynebacterium spp. 30
(ii) Gram negative cocci and coccobacilli 12
 Moraxella spp. 9
 Neisseria spp. 3
(iv) Aerobic actinomycetes 46
 Nocardia spp. 46
(v) Gram-negative bacilli 321
 Pseudomonas spp. 239
 Enterobacter spp. 34
 Klebsiella spp. 12
 Proteus spp. 6
 Alcaligens spp. 6
 Haemophilus spp. 6
 Acinetobacter spp. 6
 Escherichia coli 4
 Serratia spp. 3
 Citrobacter spp. 5
Total number of fungal isolates recovered 1226
(i) Hyaline fungi 891
 Fusarium spp. 511
 Aspergillus spp. 305
 Mucor spp. 6
 Rhizopus spp. 4
 Penicillium spp. 4
 Unidentified hyaline fungal species 61
(ii) Dematiaceous fungi 335
 Cladosporium spp. 81
 Botryodiploidia spp. 57
 Curvularia spp. 52
 Biopolaris spp. 29
 Exserohilum spp. 24
 Alternaria spp. 13
Unidentified dematiacious fungal species 79

Name of isolates Percentage

Total number of bacterial isolates recovered 100
(i) Gram-positive cocci 64.1
 Streptococcus pneumoniae 36
 Streptococcus epidermidis 18.3
 Staphylococcus aureus 3.8
 Miccrococcus spp. 0.5
 Alpha haemolytic streptococci 4.4
 Beta haemolytic streptococci 0.5
 Non haemolytic streptococci 0.7
(ii) Gram positive bacilli 4.7
 Bacillus spp. 2.2
 Corynebacterium spp. 2.5
(ii) Gram negative cocci and coccobacilli 1
 Moraxella spp. 0.7
 Neisseria spp. 0.3
(iv) Aerobic actinomycetes 3.8
 Nocardia spp. 3.8
(v) Gram-negative bacilli 26.4
 Pseudomonas spp. 19.7
 Enterobacter spp. 2.8
 Klebsiella spp. 1
 Proteus spp. 0.5
 Alcaligens spp. 0.5
 Haemophilus spp. 0.5
 Acinetobacter spp. 0.5
 Escherichia coli 0.3
 Serratia spp. 0.3
 Citrobacter spp. 0.4
Total number of fungal isolates recovered 100
(i) Hyaline fungi 72.7
 Fusarium spp. 41.7
 Aspergillus spp. 24.9
 Mucor spp. 5
 Rhizopus spp. 0.3
 Penicillium spp. 0.3
 Unidentified hyaline fungal species 5
(ii) Dematiaceous fungi 27.3
 Cladosporium spp. 6.6
 Botryodiploidia spp. 4.7
 Curvularia spp. 4.2
 Biopolaris spp. 2.4
 Exserohilum spp. 2
 Alternaria spp. 1
Unidentified dematiacious fungal species 6.4

* Of the 1551 eyes, 1069 eyes had bacterial growth alone, 81 eyes
had both bacterial and fungal growth and 1 eye had both bacterial
and acanthamoebic growth. ** Of the 1220 eyes, 1138 eyes had
fungal growth alone, 81 had both fungal and bacterial growth and 1
eye had both fungal and acanthamoebic growth

Table III. Association between the identified predisposing risk factors
and the causative microorganisms isolated from corneal scrapes obtained
from patients (n=3295) with infective keratitis (non-viral) treated
at a tertiary eye care referral centre in south India

Predisposing Total number of
risk factors cases (%)

Ocular injuries 2356 (71.5)
 vegetative matters 843 (25.6)
 dirt/ soil/ stone/ sand 1191 (36.1)

 animal matters 166 (5)
 miscellaneous items: 156 (4.7)
Co-existing ocular diseases 878 (26.7)
(i) Lacrimal disorders:
 chronic dacryocystitis 251 (7.6)
(ii) Corneal disorders:
 spheroidal degeneration 279 (8.5)
 pre-existing viral keratitis 35 (1.1)
 bullous keratopathy 26 (0.8)
 corneal scar 9 (0.3)
(iii) Lid disorders:
 blepharitis 97 (2.9)
 lid abnormalities 33 (1)
 lagophthalmos 29 (0.9)
(iv) Suture-infiltration
 Trauma-related 49 (1.5)
(v) Conjunctival disorders:
 dry eye syndrome 40 (1.2)
 conjunctivitis 30 (0.9)
Contact lens usage 35 (1.1)
Usage of steroids (topical) 26 (0.8)
systemic diseases 239 (7.3)
 diabetes mellitus 216 (6.6)
 leprosy 9 (0.3)
 tuberculosis 8 (0.2)
 Stevens-Johnson syndrome 6 (0.2)
Total 3295 (100)

Predisposing Bacterial growth
risk factors (%)

Ocular injuries 300 (28.1)
 vegetative matters 26 (2.4)
 dirt/ soil/ stone/ sand 211 (19.8)

 animal matters 42 (3.9)
 miscellaneous items: 21 (2)
Co-existing ocular diseases 724 (67.9)
(i) Lacrimal disorders:
 chronic dacryocystitis 251 (23.6)
(ii) Corneal disorders:
 spheroidal degeneration 241 (22.6)
 pre-existing viral keratitis 13 (1.2)
 bullous keratopathy 20 (1.9)
 corneal scar 5 (0.5)
(iii) Lid disorders:
 blepharitis 75 (7)
 lid abnormalities 19 (1.8)
 lagophthalmos 18 (1.7)
(iv) Suture-infiltration
 Trauma-related 30 (2.8)
(v) Conjunctival disorders:
 dry eye syndrome 26 (2.4)
 conjunctivitis 26 (2.4)
Contact lens usage 35 (3.3)
Usage of steroids (topical) 7 (0.7)
systemic diseases 51 (4.8)
 diabetes mellitus 37 (3.5)
 leprosy 6 (0.6)
 tuberculosis 6 (0.6)
 Stevens-Johnson syndrome 2 (0.2)
Total 1066 (100)

Predisposing Fungal growth
risk factors (%)

Ocular injuries 1046 (91.9)
 vegetative matters 696 (61.2)
 dirt/ soil/ stone/ sand 246 (21.6)

 animal matters 69 (6.1)
 miscellaneous items: 35 (3.1)
Co-existing ocular diseases 79 (6.9)
(i) Lacrimal disorders:
 chronic dacryocystitis 0
(ii) Corneal disorders:
 spheroidal degeneration 26 (2.3)
 pre-existing viral keratitis 15 (1.3)
 bullous keratopathy 0
 corneal scar 2 (0.2)
(iii) Lid disorders:
 blepharitis 0
 lid abnormalities 8 (0.7)
 lagophthalmos 9 (0.8)
(iv) Suture-infiltration
 Trauma-related 19 (1.7)
(v) Conjunctival disorders:
 dry eye syndrome 0
 conjunctivitis 0
Contact lens usage 0
Usage of steroids (topical) 13 (1.1)
systemic diseases 183 (16.1)
 diabetes mellitus 179 (15.7)
 leprosy 2 (0.2)
 tuberculosis 2 (0.2)
 Stevens-Johnson syndrome 0
Total 1138 (100)

Predisposing Acanthamoeba Bacterial &
risk factors growth (%) fungal (%)

Ocular injuries 33 (100) 81 (100)
 vegetative matters 3 (9.1) 17 (21)
 dirt/ soil/ stone/ sand 30 (90.9)[28 had 27 (33.3)
 mud injury]
 animal matters 0 35 (43.2)
 miscellaneous items: 0 2 (2.5)
Co-existing ocular diseases 0 0
(i) Lacrimal disorders:
 chronic dacryocystitis 0 0
(ii) Corneal disorders:
 spheroidal degeneration 0 0
 pre-existing viral keratitis 0 0
 bullous keratopathy 0 0
 corneal scar 0 0
(iii) Lid disorders:
 blepharitis 0 0
 lid abnormalities 0 0
 lagophthalmos 0 0
(iv) Suture-infiltration
 Trauma-related 0 0
(v) Conjunctival disorders:
 dry eye syndrome 0 0
 conjunctivitis 0 0
Contact lens usage 0 0
Usage of steroids (topical) 0 0
systemic diseases 0 0
 diabetes mellitus 0 0
 leprosy 0 0
 tuberculosis 0 0
 Stevens-Johnson syndrome 0 0
Total 33 (100) 81 (100)

Predisposing Acanthamoeba & Acanthamoeba &
risk factors fungal (%) bacterial

Ocular injuries 1 (100) 1 (100)
 vegetative matters 0 0
 dirt/ soil/ stone/ sand 1 (100) 1 (100)

 animal matters 0 0
 miscellaneous items: 0 0
Co-existing ocular diseases 0 0
(i) Lacrimal disorders:
 chronic dacryocystitis 0 0
(ii) Corneal disorders:
 spheroidal degeneration 0 0
 pre-existing viral keratitis 0 0
 bullous keratopathy 0 0
 corneal scar 0 0
(iii) Lid disorders:
 blepharitis 0 0
 lid abnormalities 0 0
 lagophthalmos 0 0
(iv) Suture-infiltration
 Trauma-related 0 0
(v) Conjunctival disorders:
 dry eye syndrome 0 0
 conjunctivitis 0 0
Contact lens usage 0 0
Usage of steroids (topical) 0 0
systemic diseases 0 0
 diabetes mellitus 0 0
 leprosy 0 0
 tuberculosis 0 0
 Stevens-Johnson syndrome 0 0
Total 1 (100) 1 (100)

Predisposing No growth (%)
risk factors

Ocular injuries 894 (91.7)
 vegetative matters 101 (10.4)
 dirt/ soil/ stone/ sand 675 (69.2)

 animal matters 20 (2.1)
 miscellaneous items: 98 (10.1)
Co-existing ocular diseases 75 (7.7)
(i) Lacrimal disorders:
 chronic dacryocystitis 0
(ii) Corneal disorders:
 spheroidal degeneration 12 (1.2)
 pre-existing viral keratitis 7 (0.7)
 bullous keratopathy 6 (0.6)
 corneal scar 2 (0.2)
(iii) Lid disorders:
 blepharitis 22 (2.3)
 lid abnormalities 6 (0.6)
 lagophthalmos 2 (0.2)
(iv) Suture-infiltration
 Trauma-related 0
(v) Conjunctival disorders:
 dry eye syndrome 14 (1.4)
 conjunctivitis 4 (0.4)
Contact lens usage 0
Usage of steroids (topical) 6 (0.6)
systemic diseases 5 (0.5)
 diabetes mellitus 0
 leprosy 1 (0.1)
 tuberculosis 0
 Stevens-Johnson syndrome 4 (0.4)
Total 975 (100)

Table IV. Age-wise distribution of risk factors predisposing to
microbial keratitis according to the causative microorganisms
isolated from corneal scrapes obtained from patients (n=3295)
with infective keratitis (non-viral)

 Bacterial
Predisposing risk factors Total no. of growth (%)
identified cases (%) Total no.

Ocular injuries 2356 300 (12.7)
 vegetative matters 843 26
 dirt/ soil/ stone/ sand 1191 211
 animal matters 166 42
 miscellaneous items: 156 21
Co-existing ocular diseases 878 724 (82.5)
(i) Lacrimal disorders:
 chronic dacryocystitis 251 251
(ii) Corneal disorders:
 spheroidal degeneration 279 241
 pre-existing viral 35 13
 keratitis
 bullous keratopathy 26 20
 corneal scar 9 5
(iii) Lid disorders:
 blepharitis 97 75
 lid abnormalities 33 19
 lagophthalmos 29 18
(iv) Suture-infiltration
 Trauma-related 49 30
(v) Conjunctival disorders:
 dry eye syndrome 40 26
 conjunctivitis 30 26
Contact lens usage 35 35 (100)
Usage of steroids (topical) 26 7 (26.9)
Systemic diseases 239 51 (21.3)
 diabetes mellitus 216 37
 leprosy 9 6
 tuberculosis 8 6
 Stevens-Johnson syndrome 6 2
Total number (%) 3295 (100) 1066 172
 (32.4)

Predisposing risk factors Bacterial growth (%)
identified <21 yr 21-50 yr

Ocular injuries 107 (4.5) 157 (6.7)
 vegetative matters 11 11
 dirt/ soil/ stone/ sand 87 96
 animal matters 3 37
 miscellaneous items: 6 13
Co-existing ocular diseases 47 (5.4) 73 (8.3)
(i) Lacrimal disorders:
 chronic dacryocystitis 0 14
(ii) Corneal disorders:
 spheroidal degeneration 0 11
 pre-existing viral 6 2
 keratitis
 bullous keratopathy 0 2
 corneal scar 0 0
(iii) Lid disorders:
 blepharitis 19 22
 lid abnormalities 5 5
 lagophthalmos 1 2
(iv) Suture-infiltration
 Trauma-related 0 3
(v) Conjunctival disorders:
 dry eye syndrome 2 3
 conjunctivitis 14 9
Contact lens usage 18 (51.4) 17 (48.6)
Usage of steroids (topical) 0 0
Systemic diseases 3 (1.3) 12 (5)
 diabetes mellitus 1 9
 leprosy 0 1
 tuberculosis 0 2
 Stevens-Johnson syndrome 2 0
Total number (%) (5.2) 247 (7.5)

 Bacterial Fungal
Predisposing risk factors growth (%) growth (%)
identified >50 yr Total no.

Ocular injuries 36 (1.5) 1046 (44.4)
 vegetative matters 4 696
 dirt/ soil/ stone/ sand 28 246
 animal matters 2 69
 miscellaneous items: 2 35
Co-existing ocular diseases 604 (68.8) 79 (9)
(i) Lacrimal disorders:
 chronic dacryocystitis 237 0
(ii) Corneal disorders:
 spheroidal degeneration 230 26
 pre-existing viral 5 15
 keratitis
 bullous keratopathy 18 0
 corneal scar 5 2
(iii) Lid disorders:
 blepharitis 34 0
 lid abnormalities 9 8
 lagophthalmos 15 9
(iv) Suture-infiltration
 Trauma-related 27 19
(v) Conjunctival disorders:
 dry eye syndrome 21 0
 conjunctivitis 3 0
Contact lens usage 0 0
Usage of steroids (topical) 7 (26.9) 13 (50)
Systemic diseases 36 (15.1) 183 (76.6)
 diabetes mellitus 27 179
 leprosy 5 2
 tuberculosis 4 2
 Stevens-Johnson syndrome 0 0
Total number (%) 647 (19.6) 1138
 (34.5)

Predisposing risk factors Fungal growth (%)
identified <21 yr 21-50 yr

Ocular injuries 161 (6.8) 751 (31.9)
 vegetative matters 71 564
 dirt/ soil/ stone/ sand 70 121
 animal matters 9 45
 miscellaneous items: 11 21
Co-existing ocular diseases 3 (0.3) 14 (1.6)
(i) Lacrimal disorders:
 chronic dacryocystitis 0 0
(ii) Corneal disorders:
 spheroidal degeneration 0 3
 pre-existing viral 2 4
 keratitis
 bullous keratopathy 0 0
 corneal scar 0 0
(iii) Lid disorders:
 blepharitis 0 0
 lid abnormalities 1 2
 lagophthalmos 0 1
(iv) Suture-infiltration
 Trauma-related 0 4
(v) Conjunctival disorders:
 dry eye syndrome 0 0
 conjunctivitis 0 0
Contact lens usage 0 0
Usage of steroids (topical) 0 0
Systemic diseases 2 (0.8) 24 (10)
 diabetes mellitus 2 24
 leprosy 0 0
 tuberculosis 0 0
 Stevens-Johnson syndrome 0 0
Total number (%) 164 (5)765 (23.2)

 Fungal Acanthamoeba
Predisposing risk factors growth (%) growth (%)
identified >50 yr Total no.

Ocular injuries 134 (5.7) 33 (1.4)
 vegetative matters 61 3
 dirt/ soil/ stone/ sand 55 30
 animal matters 15 0
 miscellaneous items: 3 0
Co-existing ocular diseases 62 (7.1) 0
(i) Lacrimal disorders:
 chronic dacryocystitis 0 0
(ii) Corneal disorders:
 spheroidal degeneration 23 0
 pre-existing viral 9 0
 keratitis
 bullous keratopathy 0 0
 corneal scar 2 0
(iii) Lid disorders:
 blepharitis 0 0
 lid abnormalities 5 0
 lagophthalmos 8 0
(iv) Suture-infiltration
 Trauma-related 15 0
(v) Conjunctival disorders:
 dry eye syndrome 0 0
 conjunctivitis 0 0
Contact lens usage 0 0
Usage of steroids (topical) 13 (50) 0
Systemic diseases 157 (65.7) 0
 diabetes mellitus 153 0
 leprosy 2 0
 tuberculosis 2 0
 Stevens-Johnson syndrome 0 0
Total number (%) 209 (6.3) 33 (1)

Predisposing risk factors Acanthamoeba growth (%)
identified <21 yr 21-50 yr >50 yr

Ocular injuries 0 24 (1) 9 (0.4)
 vegetative matters 0 2 1
 dirt/ soil/ stone/ sand 0 22 8
 animal matters 0 0 0
 miscellaneous items: 0 0 0
Co-existing ocular diseases 0 0 0
(i) Lacrimal disorders:
 chronic dacryocystitis 0 0 0
(ii) Corneal disorders:
 spheroidal degeneration 0 0 0
 pre-existing viral 0 0 0
 keratitis
 bullous keratopathy 0 0 0
 corneal scar 0 0 0
(iii) Lid disorders:
 blepharitis 0 0 0
 lid abnormalities 0 0 0
 lagophthalmos 0 0 0
(iv) Suture-infiltration
 Trauma-related 0 0 0
(v) Conjunctival disorders:
 dry eye syndrome 0 0 0
 conjunctivitis 0 0 0
Contact lens usage 0 0 0
Usage of steroids (topical) 0 0 0
Systemic diseases 0 0 0
 diabetes mellitus 0 0 0
 leprosy 0 0 0
 tuberculosis 0 0 0
 Stevens-Johnson syndrome 0 0 0
Total number (%) 0 24 (0.7) 9 (0.3)

Table V. Occupational profiles and risk factors predisposing to
microbial keratitis according to the causative microorganisms
isolated from corneal scrapes obtained from patients (n=3295)
with infective keratitis (non-viral) treated at a tertiary eye
care referral centre in south India

 Bacterial
Predisposing risk factors Total number growth (%)
identified of cases (%) Total no.

Ocular injuries 2356 300 (12.7)
 vegetative matters 843 26
 dirt/ soil/ stone/ sand 1191 211
 animal matters 166 42
 miscellaneous items: 156 21
Co-existing ocular diseases 878 724 (82.5)
(i) Lacrimal disorders:
 chronic dacryocystitis 251 251
(ii) Corneal disorders:
 spheroidal degeneration 279 241
 Pre-existing viral keratitis 35 13
 bullous keratopathy 26 20
 corneal scar 9 5
(iii) Lid disorders:
 blepharitis 97 75
 lid abnormalities 33 19
 lagophthalmos 29 18
(iv) Suture-infiltration
 Trauma-related 49 30
(v) Conjunctival disorder:
 conjunctivitis 30 26
 dry eye syndrome 40 26
Contact lens usage 35 35 (100)
Usage of steroids 26 7 (26.9)
Systemic diseases 239 51 (21.3)
 diabetes mellitus 216 37
 leprosy 9 6
 tuberculosis 8 6
 Stevens-Johnson syndrome 6 2
Total number (%) 3295 (100) 1066 (32.4)

Predisposing risk factors Bacterial growth (%)
identified Agricultural Non-
 workers agricultural
 workers

Ocular injuries 243 (10.3) 57 (2.4)
 vegetative matters 26 0
 dirt/ soil/ stone/ sand 172 39
 animal matters 40 2
 miscellaneous items: 5 16
Co-existing ocular diseases 202 (23) 522 (59.5)
(i) Lacrimal disorders:
 chronic dacryocystitis 103 148
(ii) Corneal disorders:
 spheroidal degeneration 61 180
 Pre-existing viral keratitis 5 8
 bullous keratopathy 0 20
 corneal scar 1 4
(iii) Lid disorders:
 blepharitis 17 58
 lid abnormalities 0 19
 lagophthalmos 0 18
(iv) Suture-infiltration
 Trauma-related 7 23
(v) Conjunctival disorder:
 conjunctivitis 0 26
 dry eye syndrome 8 18
Contact lens usage 0 35 (100)
Usage of steroids 2 (7.7) 5 (19.2)
Systemic diseases 12 (5) 39 (16.3)
 diabetes mellitus 6 31
 leprosy 4 2
 tuberculosis 2 4
 Stevens-Johnson syndrome 0 2
Total number (%) 447 (13.6) 619 (18.8)

Predisposing risk factors Fungal growth (%)
identified Total no. Agricultural
 workers

Ocular injuries 1046 (44.4) 707 (30)
 vegetative matters 696 622
 dirt/ soil/ stone/ sand 246 36
 animal matters 69 38
 miscellaneous items: 35 11
Co-existing ocular diseases 79 (9) 33 (3.8)
(i) Lacrimal disorders:
 chronic dacryocystitis 0 0
(ii) Corneal disorders:
 spheroidal degeneration 26 12
 Pre-existing viral keratitis 15 8
 bullous keratopathy 0 0
 corneal scar 2 0
(iii) Lid disorders:
 blepharitis 0 0
 lid abnormalities 8 3
 lagophthalmos 9 2
(iv) Suture-infiltration
 Trauma-related 19 8
(v) Conjunctival disorder:
 conjunctivitis 0 0
 dry eye syndrome 0 0
Contact lens usage 0 0
Usage of steroids 13 (50) 2 (7.7)
Systemic diseases 183 (76.6) 28 (11.7)
 diabetes mellitus 179 28
 leprosy 2 0
 tuberculosis 2 0
 Stevens-Johnson syndrome 0 0
Total number (%) 1138 (34.5) 742 (22.5)

Predisposing risk factors Fungal growth (%) Acanthamoeba
identified Non- growth (%)
 agricultural Total no.
 workers

Ocular injuries 339 (14.4) 33 (1.4)
 vegetative matters 74 3
 dirt/ soil/ stone/ sand 210 30
 animal matters 31 0
 miscellaneous items: 24 0
Co-existing ocular diseases 46 (5.2) 0
(i) Lacrimal disorders:
 chronic dacryocystitis 0 0
(ii) Corneal disorders:
 spheroidal degeneration 14 0
 Pre-existing viral keratitis 7 0
 bullous keratopathy 0 0
 corneal scar 2 0
(iii) Lid disorders:
 blepharitis 0 0
 lid abnormalities 5 0
 lagophthalmos 7 0
(iv) Suture-infiltration
 Trauma-related 11 0
(v) Conjunctival disorder:
 conjunctivitis 0 0
 dry eye syndrome 0 0
Contact lens usage 0 0
Usage of steroids 11 (42.3) 0
Systemic diseases 155 (64.9) 0
 diabetes mellitus 151 0
 leprosy 2 0
 tuberculosis 2 0
 Stevens-Johnson syndrome 0 0
Total number (%) 396 (12) 33 (1)

Predisposing risk factors Acanthamoeba growth (%)
identified Agricultural Non-
 workers agricultural
 workers

Ocular injuries 26 (1.1) 7 (0.3)
 vegetative matters 3 0
 dirt/ soil/ stone/ sand 23 7
 animal matters 0 0
 miscellaneous items: 0 0
Co-existing ocular diseases 0 0
(i) Lacrimal disorders:
 chronic dacryocystitis 0 0
(ii) Corneal disorders:
 spheroidal degeneration 0 0
 Pre-existing viral keratitis 0 0
 bullous keratopathy 0 0
 corneal scar 0 0
(iii) Lid disorders:
 blepharitis 0 0
 lid abnormalities 0 0
 lagophthalmos 0 0
(iv) Suture-infiltration
 Trauma-related 0 0
(v) Conjunctival disorder:
 conjunctivitis 0 0
 dry eye syndrome 0 0
Contact lens usage 0 0
Usage of steroids 0 0
Systemic diseases 0 0
 diabetes mellitus 0 0
 leprosy 0 0
 tuberculosis 0 0
 Stevens-Johnson syndrome 0 0
Total number (%) 26 (0.8) 7 (0.2)
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Author:Bharathi, M. Jayahar; Ramakrishnan, R.; Meenakshi, R.; Shivakumar, C.; Raj, D. Lional
Publication:Indian Journal of Medical Research
Article Type:Report
Geographic Code:9INDI
Date:Dec 1, 2009
Words:6457
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