The Prevalence of Bacterial Keratitis Among Female Students of The Faculty of Medical Sciences at The National University Who Wear Contact Lenses, Sana'a, Yemen

Background: Contact lens wearing is a critical risk factor for microbial keratitis in developing countries, representing a major cause of corneal blindness. In Yemen, there are no reliable statistics documenting bacterial keratitis prevalence among contact lens wearing. 

Aims: To find the prevalence of bacterial keratitis among medical sciences female students at The National University who wear contact lenses, Sana'a, Yemen.

Methods: A cross-sectional structured questionnaire survey of 50 elements was conducted to evaluate the sociodemographic data. Corneal specimens were collected and cultured to bacterial keratitis diagnosis.

Results: The prevalence rate of bacterial keratitis was 72%. Staphylococcus aurous was the most common agent of bacterial keratitis. There were significant differences between bacterial keratitis and age, sharing contact lens and contact lens cleaning.

Conclusion: This study indicated that the magnitude of bacterial keratitis among contact lenses females’ wearers was high level. Age, sharing contact lenses and contact lenses cleaning were identified as risk factors.

from approximately 32 million in 2002 to 40.9 million adult (>18 years old) wearers in 2014 only in the USA, and this number was 140 million worldwide [1, 2]. It is estimated that, the contact lens global market is approximately 19.45 billion US dollars in 2024 expended globally in contact lens market [1]. Contact lens wearing is the main risk factor for microbial keratitis with an incident rate of approximately 2-20 cases per 10,000 wearers each year and sometimes resulting in permanent vision loss [1,2]. A study conducted in UK revealed that, contact lens wearers are 80 times more likely to develop microbial keratitis than a non-contact lens wearer and another study carried out in northern California showed that, the incidence of microbial (ulcerative) keratitis was 2.8 per 10,000 noncontact lens-wearing individuals per year compared with 13.0 per 10,000 contact lens wearers [3]. Microbial keratitis is an infection of the cornea and represents a major cause of corneal blindness and visual disability [4]. Infectious keratitis can be classified as microbial keratitis (bacteria, fungi or parasites), or viral keratitis (herpes viruses) [5]. Bacterial keratitis is the most common cause of microbial keratitis, which accounts for about 90% of cases [1, 6] and strongly associated with vision loss in working age adults [5]. Bacterial keratitis is most commonly caused by Pseudomonas spp. and Staphylococci spp. [6, 7] and it is a sight-threatening contact lens complication [6]. Globally, infectious keratitis is the fifth leading cause of blindness [8] and represents a major cause of corneal blindness globally, accounting for over 5% of all blindness [9]. It has also been estimated to cause 1.5–2.0 million monocular blindness each year [10]. Microbial keratitis incidence differs worldwide. In developed countries, the incidence has been reported at 3.3–52.1 per 100,000 in the UK and 3.3% of attendees to ophthalmic emergency services were suffering from this condition [11], however 40.3 per 100 000 in England, and 6.6 per 100 000 in Australia [5], as well as, 11 cases per 100.000 inhabitants in the United States [12]. Whereas in developing countries, because of poor health care systems [5]. Infectious keratitis represents a public health threat, in which, the incidence rates are as high as 113 per 100,000 in Madurai, India, 35 339 per 100,000 in Bhutan, 121 710 per 100,000 in Burma,121 and 799 per 100,000 in Nepal [12, 13]. Yemen is a Middle Eastern developing country at the southern end of the Arabian Peninsula, southwest of Asia (14). The Human Development Index in Yemen reached its lowest value (0.452) in 2017, putting Yemen among the 12 lowest countries in the world [15]. The national poverty rate was last reported in 2014 and estimated to be 48.6% of the population, and recent welfare analysis suggests that poverty has increased to an estimated 78% as Yemen’s gross domestic product (GDP) has contracted [14]. The prevalence of blindness in Yemen is 1.5% [15]. Contact lens wearing is the main risk factor for microbial keratitis [1,2]. Microbial keratitis represents a major cause of corneal blindness and visual disability [4, 10]. The National University is a private university established in Yemen in 1994. It is considered one of the most important Yemeni universities that receive thousands of students especially in the faculty of medical sciences and has branches in most Yemeni cities. To our best knowledge, there is paucity of data on the bacterial etiologic agents of eye infection among contact lens wearers in Sana'a city, Yemen. Therefore, this study aims to study the prevalence of bacterial corneal infection and the risk factors among students of the faculty of medical sciences at The National University who wear contact lenses.

A cross-sectional structured study was conducted on 50 female students from faculty of medical sciences selected randomly at The National University, Sana'a city, Yemen. Consent of participants in this study, including any student who has ever worn contact lens for whatever reason and for any period, was taken before starting collection of data. Two methods were used in this study, epidemiology work and laboratory work.

Epidemiology Work

It was done to assist major risk factors associated with bacterial keratitis. Structured questionnaire was prepared and distributed among the students from February 2023 to April 2023. The questionnaire consisted of single-response questions and one multiple-response question. The following data were collected: age, social status, use of contact lens, hygiene practice, complication of contact lens use and others variables.

Laboratory work

It is carried out to identify most bacterial causes of keratitis. Sterilize cotton swab was used to collect corneal specimen from target subjects and placed in sterile tubes containing Amies transport media. Amies transport media was used to keep the collected specimens at 2-8°C and transport it to the microbiology laboratory for culturing in the same day. Blood agar and Chocolate agar were used to culture collected samples and to isolate pathogenic bacteria. All bacterial cultures were incubated aerobically at 37°C and assessed at 24 hours and at 48 hours and then discarded if there was no growth. Specific identification of bacterial pathogens was based on bacterial colonies characteristics, hemolysis, swarming, and fermentation on cultured media and based on staining properties, and biochemical properties using standard laboratory methods.

Statistical analyzes were performed using the Statistical Package for the Social Science (SPSS: Version 16.0). Chi-square test for qualitative data were used to compare differences between subjects of study where appropriate. P less then 0.05 was regarded as significant.

A total of 50 females’ students, from faculty of medical sciences in The National University, were enrolled in this study. From figure 1, the prevalence rate of bacterial keratitis among participants was 72%. Figure 2 reported that Staphylococcus aurous represented the most common isolated bacteria from collected specimens 42% followed by 22% were coagulase negative staphylococci and 6% Streptococcus species, however only 2% were Pseudomonas spp. Regarding to risk factors related to bacterial keratitis, table 1 revealed that, the participants ranged in age from 18 to 42 years with mean subjects age of 24.22. Target students aged between 23-27 years represented 58% of study population and just 2% of subjects were aged between 38-42 years. Bacterial keratitis prevalence was higher with elder age groups, and there was statistically significant (P value 0.001). Majority of the participants were unmarried 74% and no relationship estimated. Concerning about medical prescription for wear contact lenses, 90% of participating females wore contact lenses without medical prescription and for cosmetic purpose and 100% of them were using makeup while wearing contact lenses. About 42% of study sample reported that the period of wearing contact lenses extended for more than 2 hours to 5 hours daily and 40% of them extend to more than 5 hours daily and statistics association was reported (P value 0.02). With regard to daily practice while wearing contact lenses, all participants in this study indicated that they did not wear contact lens while sleeping and there was relationship between bacterial keratitis and sharing the lenses (P value 0.027) in which 52% of subjects shared their contact lenses with others from them 76.92% were infected with keratitis.  Of 80% were cleaned their hand before wearing lenses and 70% of them were infected but there was statistically insignificant between bacterial keratitis and cleaning of hands (P value 0.594). However, there was statistically significant (P value 0.027) regarding to cleaning contact lenses by using sterile solution. In relation to the side effects of wearing contact lens, 74% of targeted subjects felt pains and 34% itching in their eyes and no association established. Although there was margin correlation between bacterial keratitis and feeling with blurred vision while wearing contact lenses (P value 0.036), 83.33% of the sample study who felt blurred vision were non infected with bacterial keratitis. About 83.33% of participants who used eye drops were infected and there was statistically significant (P value 0.018).

Figure 1: Prevalence of bacterial keratitis among target female students.

Figure 2: The percentage of distribution of the different microorganisms isolated from specimen.

Table 1: Risk factors for the development of bacterial keratitis in females students contact lens wear (n=50).

*Statistically significant at p less then 0.05, **C.L.: Contact Lenses

Contact lens wearing is considered as a burden on human health in both developed and developing countries and it has been recognized as one of the most common risk factors of Microbial keratitis [16]. Infectious keratitis and its sequelae are important causes of ocular morbidity and blindness in developing countries [17]. Microbial keratitis affects approximately 5 in 10,000 wearers [6]. The present study reported the prevalence of bacterial keratitis among females’ students of faculty of medical sciences who wore contact lenses was 72%. In 2016, Ashjan Y. B. and her colleagues showed in their study conducted in Saudi Arabia, that about 52.2% students who wore contact lenses had ocular complaints [18]. In the current study, of the 72% pathogenic bacteria which isolated from corneal specimens collected from target students, 42% were Staphylococcus aurous, 22% coagulase negative staphylococci, 6% Streptococcus species and 2% were Pseudomonas spp. The results of this present study were similar to other studies conducted in Sana'a and Taiz cities in Yemen in which these studies revealed that, Gram positive cocci were the predominant and Staphylococcus aurous should always be considered as the most likely cause of bacterial corneal ulceration in Yemen [19, 20]. Darren S. et al., 2021 documented that, coagulase negative staphylococci were shown to be the most commonly isolated organisms in about half of the included studies and other common bacteria implicated in infectious keratitis included Staphylococcus aurous, Streptococci spp. [16]. Other studies reported dissimilar results, Hossein Hatam et al., 2021 and F Stapleton et al, 2012 showed that, the most common isolated bacteria were Pseudomonas aeruginosa and the next common organism was Staphylococcus spp. especially coagulase-negative spp. [1, 21, 22]. Regarding to the age and the incidence of bacterial keratitis, there was strong association between bacterial keratitis and age (P < 0>P < 0>P < 0>P < 0>P < 0>

The findings of this study indicated that the magnitude of bacterial keratitis among contact lenses females’ wearers was very high level. Modifiable risk factors, age, daily using of contact lenses, sharing contact lenses with others and cleaning of contact lenses were identified. Bacterial eye infections can be preventable diseases through promote public health education and raise awareness about dangers of wearing contact lenses which can lead to blindness.

Acknowledgements 

We thank Dr. Abdullah Almatri, the President of Jiblah University of Medical and Health Sciences, for cooperation in this study. Our thanks to Dr.  Mohammed Kashafa for his cooperation in this study

Conflict of interest

The authors declare that they have no conflict of interest.