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| | ORIGINAL ARTICLE | | | | | Year : 1988 | Volume : 36 | Issue : 2 | Page : 92-94 | | | Sterilization potential of contact lens solutions
Vijay Kumar Dada, Manoj Rai Mehta
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi-110 029,
Correspondence Address:
Vijay Kumar Dada
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi-110 029.
PMID: 3148554 In a dynamic field of Contact Lens Solutions maintenance of high standards of anti-microbial activity is a must Resterilization Activity Time' is a universally accepted yardstick for such an evaluation. In this study eight brands of indigenous popular solutions alongwith two FDA approved solutions were tested for their sterilization efficacy: Standardized suspensions of Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans and Aspergillus fumigatus were used for the purpose. It was observed that the contact lens solutions available ir, the domestic market were not upto the mark Suggestions for improvement have also been made.
How to cite this article:
Dada VK, Mehta MR. Sterilization potential of contact lens solutions. Indian J Ophthalmol 1988;36:92-4 |
| Introduction | |  |
In an everchanging and expanding field of Contact Lens Solutions, it is imperative that high standards of sterilizing activity be ensured by the manufactured of these solutions. A good sterilization potential avoids the dreaded corneal and conjunctival complications arising out of infection [1]. One of the parameters, which is universally accepted for such an evaluation, is Resterilization Activity Time [2].
In this study a few popular brands of contact lens solutions marketed in India were subjected to this test alongwith the two brands approved by the FDA of the United States of America.
| Material & Methods | | |
Eight popular brands were picked up from the home market Five of these comprised of hydrogel soaking solutions and three hard lens solutions. These solutions were coded as - A,B,C,D,E,F and H Besides these eight solutions two solutions approved by the FDA were also included code T 1 & T 2 . Composition of these solutions alongwith their respective pH is shown in [Table - 1]. Standardized suspensions of common contaminants namely, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans and Aspergillus fumigatus were for the purpose. pH of these solutions was determined using a digital meter based on Radox principle.
| Resterilization activity time | | |
As defined in the United States Pharmacopia, when 0.9 ml of a solution is inoculated with 0.9 ml of 1:100 dilution of a 24 hours culture in nutrient broth of the pathogenic strains of Pseudomonas aeruginosa, Staphylococcus aureus  and Candida albicans and a seven day culture in Sabourad's broth of Aspergillus fumigatus, no viable organism should be found after a contact time of ten minutes. The strains chosen have resistant to the routinely used antibiotics.
The test was quantified by matching the density of broths against Nephlometer tubes The number of organisms in the diluted broth was between 10 7 to 10 8 per ml This has been substantiated later by the authors using pour - plate dilution technique.
In our experiment, we took subcultures every two, five and ten minutes on blood agar plates Sterile test tubes and pipettes were used for inoculation. Direct plating was carried out at the specified intervals The organisms chosen were resistant to most antibiotics and isolated from outpatients coming to our centre.
| Observations | | |
It was found that the test solutions failed to kill the requisite bolus of micro organisms within the stipulated time limit of ten minutes Moreover two bottles were found to be already contaminated on being opened The contaminant was found to be Pseudomonas aeruginosa.
The FDA approved solutions achieved the same task in a ten minutes time. The two and five minute cultures were however positive in this case also.
| Discussion | | |
It is imperative for a contact lens fitter to have an idea about the sterilization potential of the available contact lens solutions because he or she ultimately owns the responsibility for the safe handling of the contact lenses in the hands of the patients Contact lens accessories, including solutions deserve more attention than accorded to them by an Ophthalmologist
It is the duty of the fitter to not only provide a lens with a good fit but also instruct a patient regarding the choice of an appropriate solution system.
The microbiological safeguards in the manufacture of a solution are very important These have to be adhered to strictly irrespective of the composition or the function of a solution The Indian Pharmacopia is silent regarding contact lens solutions We had to follow the United States Pharmacopia for the stringent requirements imposed by the FDA.
The tested local solutions were not upto the mark in their Resterilization Activity, while the FDA approved solutions were. The reasons for this failure could be manifold.
a) Lack of optimum pH and a poor buffering capacity
b) Decontamination activity getting lost during the process of manufacture due to bad formulation
c) Decontamination activity getting exhausted due to gradual biological, microbial contamination due to imperfect sealing of the containers. This leads to a shortened shelf life.
d) A considerable lag between manufacture and marketing leading to deactivation.
e) Suboptimal concentration of the active ingredients
The contact lens solution bottles should be suited to their rugged use. Once the bottles are opened, they are liable to contamination from the environment A solution should be able to resterilize itself within a shortwhile or else it would become a store house of infection. In order to achieve good resterilization activity the following steps may be observed
a) Increase the proportion of the active constituents. This may be possible only to a certain limit as the optimum antimicrobial concentrations may be highly toxic to the corneal epithelium. A suitable compromise is made and concentrations mildly damaging to the corneal epithelium and having a significant antimicrobial action are used'.
b) Manufacture under sterile conditions and sterilization in the final container to reduce the microbial load attained during manufacture.
c) Quality of the dispensing bottles must be improved, they should be hermetically sealed
d) Expiry date should be mentioned in bold letters as also the date of manufacture.
It may be argued that the ten minutes contact time is a bit_ short and that the most resistant varieties of organisms have been utilized But then the standards cannot be dropped in view of the potentially serious complications arising out of the use of contaminated solutions Besides a significant reserve of sterilization potential ought to be maintained in view of the careless handling of the containers In a concurrent study the authors found that fifteen (29.21%) bottles got contaminated within 7 days; 77.5 2% within thirty days and 100% within forty five days of opening the seal The commonest contaminant was Pseudomonas aeruginosa counting for 70.78% of the isolates The low incidence of reported infections leads the practitioners to assume a false sense of security. The low reporting however may be spurious as several instances never reach the stage of publicity and remain anecdotal only. Other infections may not be of a serious nature. One must remember that the possibility of a dangerous contamination is always lurking[4].
| References | | |
| 1. | Wilson LA Schlitzer R L: Pseudomonas Corneal Ulccers Associated with Soft contact lens wear. Am. J. Ophthalmol9,2 : 546-554,198 1.  | | 2. | Hales, Robert H. Contact lenses A clinical Approach to Fitting Williams and Wilkins, 1982. | | 3. | Dada V.K, Mehta M.R, Mohan M: Microbiological Hazards of Contact Lens Solutions Acta Roma, Kugler Publications/Ghedini Editor, Amsterdom, Berkely, Milano, 1986. | | 4. | Mehta M.P. Dada V K, Mohan M : Epitheliotoxicity of contact lens solutions An Experimental study on rabbit cornea using SEM. Acta Roma Kugler Publications/Ghedini Editore, Amsterdam, Berkely, Milano, 1986. |
Tables [Table - 1] |
