KARACHI: Nine contact lens disinfection solutions currently being commonly marketed in Pakistan lack the efficacy to kill specific germs that can cause a sight-threatening infection, says a recently published study.
The study titled “Inefficacy of marketed contact lens disinfection solutions against keratitis-causing Acanthamoeba castellanii belonging to the T4 genotype” has been printed in Experimental Parasitology, a journal published by Elsevier.
Dr Sahreena Lakhundi, Dr Naveed Ahmed Khan and Dr Ruqaiyyah Siddiqui of Aga Khan University’s department of biological and biomedical sciences had conducted the research. It is the first study in Pakistan that has tested different contact lens disinfecting solutions manufactured locally and internationally.
The CL disinfection solutions tested were: ReNu MultiPlus, DuraPlus, Ultimate Plus, OptiFree Replenish, OptiFree Express, Kontex Clean, Kontex Normal, Kontex Multisol extra+, Kontex Soak. Four of them are manufactured in the US. All solutions were tested within their stated expiry date.
“The results of our research are very alarming as they revealed that none of the CL disinfection solutions tested completely destroyed the germs that caused the blinding infection as per manufacturers’ instructions.
“We believe that existing contact lens disinfection solutions pose a major risk to public health and calls for urgent promotion of public awareness of eye health as well as urgent intervention measures by health department officials,” says Dr Naveed Ahmed Khan.
According to the study, none of the contact lens (CL) disinfection solutions tested had any cysticidal effects (killing or tending to kill an encysted stage of an organism) against A. castellanii keratitis isolate of the T4 genotype, which is mostly associated with Acanthamoeba keratitis (a sight-threatening ulceration of the cornea that is associated with excruciating pain).
Citing other researches, the study says that CL users are at an increased risk of contracting this infection with studies estimating that 90pc of Acanthamoeba keratitis patients are users of contact lenses.
“Contact lens wear is the most common risk factor in the development of sight-threatening ulceration of the cornea. Often, inadequate contact lens hygiene practices and noncompliance by the user are the main risk factors for the infection. Use of contaminated tap water and home-made saline solution for cleaning the lens and storage cases could also cause the infection,” it says.
Studies to evaluate the efficacy of various types of CL disinfection solutions have been performed in the US as well as Europe but no such studies have been carried out for developing countries, it points out.
“The lack of efficacy of commonly marketed CL disinfection solutions in developing countries like Pakistan is a serious concern and suggests prevalence of Acanthamoeba keratitis. However, at present there is not a single case of the disease reported from Pakistan and its burden unknown, despite the rise of contact lens wear, both for corrective and cosmetic use in the last few decades.
“Our personal communication with the consultant ophthalmologist at the Aga Khan University Hospital revealed that keratitis cases are prevalent, suggesting an urgent need for awareness,” it states.
According to the study, although some of the solutions (DuraPlus and OptiFree Replenish) did destroy more than 50pc of the specific germs within the time recommended for disinfection, this is ineffective as it leaves a significant number of viable amoebae to produce infection.
“The limited efficacy of Dura-Plus and OptiFree Replenish compared with other CL disinfection solutions is puzzling as the stated constituents of both of these solutions (such as biguanide and myristamidopropyl dimethylamine) appear to be similar to other disinfecting solutions. Thus it is imperative that routine testing of CL disinfection solutions formulations is carried out keeping in mind their shelf life, as well as regular evaluation of the efficacies of CL disinfection solutions against Acanthamoeba cysts and trophozoites.”
The researchers show concern over the finding that some of the locally formulated CL disinfection solutions (Kon-tex Clean, Kontex Normal and Kontex Multisol extra+) supported the growth of specific microorganisms, let alone exhibiting any properties to kill them.
“Additional concern is the fact that these solutions can be bought without any instructions given to the consumer, majority of whom are unaware of associated risks or they are teenagers in the case of cosmetic CL users,” points out Dr Naveed Ahmed Khan.
According to Dr Khan, contact lens for cosmetics as well as corrective use are routinely available over the counter in developing countries such as Pakistan without any instructions of proper hygiene in handling CL given to users.
“We believe that these findings should be of great concern to health officials and to the manufacturers of the CL disinfection solutions and require urgent intervention measures to address this issue,” he said.
Published in Dawn, June 2nd, 2014