Microbial contamination of hydrogel contact lenses

Abstract

1997. Bacterial contamination of contact lenses (CLs) may contribute to CL-related corneal infection and inflammation. T h i s study reports CL biota over time during daily and extended wear. Microbial contamination of a 58Oio water,ionic hydrogel CL and a 38%o water, non-ionic hydrogel CL was evaluated in an Australian and an Indian population. Fifty wearers were repeatedly sampled over 18 months. Overnight CL use did not alter the frequency of positive cultures, nor the spectrum of organisms compared with daily CL wear. T h e r e were no differences in type and frequency of CL contamination between the CL types. Positive cultures were more frequently recovered from the Indian population compared with the Australian population.Streptococcus spp. and Propionihacteriurn spp. were more frequently isolated from the Australian population. Fungi and B a d u s spp. were more frequently isolated from the Indian population. Normal CL biota alone cannot explain the increased rate of infection and inflammation in extended wear.

Microbial Keratitis in Prospective Studies of Extended Wear With Disposable Hydrogel Contact Lenses

“…Previously we have reported that the rates of more common adverse events seen with soft contact lens wear are greater in the Indian population compared with other sites, 16 and this difference is attributed to the increased microbial load and other contaminant loads that are prevalent in the environment in the area. 19 It is possible that an increased contaminant load may have impacted on the number of events of microbial keratitis seen in India. However, the overlap in the survival curves for each site indicated that there was a greater likelihood that the rate of this adverse event in the 2 populations was not different.…”

Hydrogels porosity and bacteria penetration: Where is the pore size threshold?

“…The concern about contamination of hydrogels with microorganisms is particularly relevant when hydrogels are intended to be exposed to the environment, such as in the case of the wound dressings and the contact lenses [1,2]. Hydrogels used as wound dressings are intended to be permeable to water vapour, gases and small protein molecules, but impermeable to microorganisms [3].…”

Corneal Erosions, Bacterial Contamination of Contact Lenses, and Microbial Keratitis

“…Indeed, there seems to be some other factor(s) involved in the increase in the rate of MK during extended wear other than simply an increase in bacterial colonization of lenses. It has been established that there is only a slight increase in the number of bacteria that colonize lenses during asymptomatic wear if lenses are worn on an extended wear basis compared to daily wear basis 22 ; an increase of between 1.1 and 2.4 times, whereas the rate of MK is five times as high. 6 Contact lenses can cause several forms of trauma to the eye, including trauma as a result of entrapment of foreign bodies between the lens and the cornea, and conditions such as corneal erosions, superior epithelial arcuate lesions and perhaps contact lens-induced peripheral ulcers.…”