Microbial keratitis in Hong Kong: relationship to climate, environment andcontact-lens disinfection

Microbial keratitis has been studied in Hong Kong as a representative sub-t ropical climate of south China. An 18-month investigation in 1997/98 of 223 cases of ulcerative keratitis (presumed microbial) was conducted in the 2 million population of Shatin and Kowloon at the Prince of Wales and Hong Ko ng Eye Hospitals respectively with comprehensive microbiology. A case-contr ol study was pursued at the same time between 45 contact-lens wearers (CLW) developing microbial keratitis and 135 lens-wearing volunteers matched for age, sex, educational status and visual acuity. Home water supplies were s ampled for Acanthamoeba. Previous ocular surface disease and trauma (preven table by wearing goggles for grinding) were common predisposing causes whil e cosmetic wear of contact lenses was responsible for 26% of cases overall. Pseudomonas aeruginosa was the commonest bacterium isolated, from both CLW and non-CLW, with infection being acquired within the community. These 28 pseudomonads remained fully sensitive to the third-generation cephalosporin s, aminoglycosides and quinolone antibiotics, which is very encouraging. Fu ngi were isolated, predominantly Fusarium sp., but less commonly than expec ted. A fungal/bacterial ratio was obtained of 1/17, while in comparison, th e expected ratio for a tropical climate ranges from 1/5 (Singapore) to 1/2 (South India). Acanthamoeba was the second commonest microbe isolated from keratitis of CLW. The domestic water environment of 8% of homes of both pat ients and controls wearing contact lenses was colonized with Acanthamoeba. Lack of hygiene, use of tap water for storing lenses, failure to air-dry le ns-storage cases or use of one-step hydrogen peroxide disinfectant were ide ntified as risk factors for keratitis in CLW. The study results commend use of multipurpose solutions by CLW in Hong Kong to achieve the lowest expect ed rates of infection.