Efficacy of multipurpose solutions for rigid gas permeable lenses

The efficacy of a device-based approach to microorganism disinfection and protein removal for orthokeratology lenses in varied clinical circumstances

PURPOSE

RigidCare is an electrolysis-based device that recently obtained approval from the US's FDA to sterilise microorganisms and remove proteins for orthokeratology (O-K) lenses. The study was conducted to investigate the device's performance in varied clinical circumstances.

METHODS

Trial lenses and private lenses were employed by O-K lens wearers from five hospitals for an evaluation of disinfection and sterilisation and an assessment of protein removal, respectively. Menicon multipurpose solution and protein remover were selected for use with the control group. Following the instructions, pre-cleaning lens samples, post-cleaning lens samples and residual solution samples of trial lenses of the experimental and control groups were collected for microorganism examinations by an experienced third-party testing organisation. The levels of protein deposition for these two approaches were rated by senior O-K experts. Categorical variables were analysed using statistical tests, such as the chi-squared test and Fisher's exact test.

RESULTS

The microbial positive rate detected from the pre-cleaning and post-cleaning lens samples and the residual solution of the trial lenses for the experimental and control group was 4/76 vs 1/74 (P = 0.37), 1/76 vs 0/74 (P = 1.00) and 0/76 vs 8/74 (P = 0.006), respectively. Following protein removal, the experimental group exhibited a significantly higher overall proportion of lenses rated as 'clean' or with a 'mild deposit' (96.4 %, 79/82) compared to the control group (85.7 %, 66/77), with a significant difference (P < 0.05).

CONCLUSION

This multi-center study demonstrated that RigidCare exhibited superior efficacy in disinfection, sterilisation and protein removal as compared to Menicon multipurpose solution and protein remover.

Activity of multipurpose contact lens solutions against Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcescens and Candida albicans biofilms

INTRODUCTION

The use of contact lenses has progressively increased around the world, thereby increasing the risk of complications. The most serious complication is microbial keratitis (corneal infection) that can progress to a corneal ulcer.

METHODS

Fourteen multipurpose contact lens solutions were tested on mature biofilms comprising Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcescens and Candida albicans, using the minimum disinfection times recommended by the manufacturers. The biofilm was induced in the lens case, and 24 h later, the solutions were added. Activity against planktonic and sessile cells was evaluated and quantified as colony forming units per millilitre. The minimum concentration for biofilm eradication was defined as a 99.9% reduction in viable cells.

RESULTS

Although most solutions exhibited activity against planktonic cells, only five of the 14 solutions produced a significant reduction in the S. marcescens biofilm. No solution achieved the minimal biofilm eradication of S. aureus, P. aeruginosa and C. albicans.

CONCLUSION

Multipurpose contact lens solutions provide greater bactericidal and/or fungicidal activity on planktonic cells than biofilms. The minimal eradication biofilm concentration was only achieved for S. marcescens.

A novel quantitative evaluation of deposits adhered to worn orthokeratology contact lenses

PURPOSE

Total deposition and deposition along the reverse curve of heavily deposited worn orthokeratology (OK) lenses were quantitatively evaluated using two novel imaging methods. In addition, the cleaning efficacies of a contact lens cleaning solution for daily use and an intensive cleaner and protein remover solution were evaluated using the same two methods.

STUDY DESIGN

Experimental study.

METHODS

Twenty-six worn reverse-geometry OK lenses (MY Emerald, Technopia) were photographed for use in three experiments: (1) total deposition was assessed before and after cleaning with two cleaning solutions; (2) in addition to assessing total lens deposition, the feasibility of measuring the thickness of lens deposits along the reverse curve was assessed; and (3) after confirming it was possible to assess the thickness of lens deposits, the thickness of deposits was assessed before and after cleaning with a daily contact lens cleaning solution (O₂ Care^®, Menicon Co., Ltd.) and an intensive cleaner and protein remover (Progent^®, Menicon Co., Ltd.). Total lens deposition was assessed as the total volume of cloudiness over the lens surface in terms of volume per unit pixel. Cross-sectional images were taken from worn OK lenses to assess the thickness of lens deposits on the reverse curve as the area of deposits/horizontal length.

RESULTS

Significant differences in total deposition were found between the three cleaning conditions for the twenty worn OK lenses (mean total deposition ± SD for pre-cleaning = 0.209 ± 0.076; post-daily cleaning = 0.124 ± 0.078; and post-intensive cleaning = 0.045 ± 0.046) (p < 0.001). Mean total deposition and thickness of the deposits along the reverse curve for the three lenses from the second experiment were 0.310 and 6.0 mm, respectively. The mean thicknesses of lens deposits found in the third experiment under the 3 conditions were as follows: pre-cleaning = 3.4 µm; post-daily cleaning = 2.3 µm; and post-intensive cleaning = 0.0 µm.

CONCLUSION

The two novel imaging methods used in this study detected significant amounts of deposits attached to worn OK lenses and were sensitive enough to detect a reduction in deposition following the use of the two cleaning solutions tested. Furthermore, these methods could visualize and quantify the thickness of lens deposits along the reverse curve.

To rub or not to rub? - effective rigid contact lens cleaning

PURPOSE

To compare the efficacy of cleaning of rigid contact lenses using two care solutions with and without rubbing.

METHODS

A masked randomised trial was conducted. The cleaning efficacy of two solutions recommended for rigid contact lenses, a one-step hydrogen peroxide solution (HP) and a povidone iodine-based solution (PI), were evaluated on 64 unworn orthokeratology (ortho-k) lenses subsequent to cleaning with rubbing (R) with a surfactant cleaner or without rubbing (NR). Either mascara or hand cream was applied as a contaminant to the lenses to simulate stubborn and loosely bounded deposits, respectively. For each type of deposit, the lenses were randomly assigned to four cleaning treatments: R with HP, NR with HP, R with PI, and NR with PI (n = 8 for each group). Each lens surface was assessed on site by a masked examiner under a low-magnification slit-lamp and with photo-documentation. Lenses were graded according to the deposit coverage area using a pre-set five-point scale [0 (<20% coverage) - 4 (>80% coverage)].

RESULTS

For stubborn deposits (mascara), NR failed to remove deposits from 94% of lenses, whilst R removed more than 80% of deposits from 63% of the lenses. For oily deposits, 25% of NR lenses had >80% coverage, whilst only one R lens had 60-80% coverage, with 19% having 40-60% coverage, and 38% with either 20-40% or <20%. Rubbing improved lens cleanliness for both types of deposits, but only reached statistical significance for the stubborn deposit group. There were no significant differences between the solutions.

CONCLUSION

Not Rubbing and using either HP or PI solutions, is not effective in removing stubborn deposits from ortho-k lenses. It is essential to rub lenses when cleaning rigid lenses to ensure optimal lens hygiene for ocular health, especially as rigid gas permeable (RGP) lenses are intended to be reused for at least a year before replacement. Rubbing with a daily cleaner should be included in the instructions for use of the solutions tested for rigid lenses and practitioners should be encouraged to emphasise the importance of rubbing in lens care.

Bacterial Bioburden Decrease in Orthokeratology Lens Storage Cases After Forewarning: Assessment by the DNA Dot Hybridization Assay

Background:

The aim of this study was to measure the changes in the bacterial bioburden in orthokeratology (OK) lens storage cases using the DNA dot hybridization assay (DHA) after forewarning patients about their bacterial contamination severity.

Methods:

Thirty-one OK lens wearers were prospectively enrolled in this study. Dot hybridization assay was used for serial measurements of bacterial bioburden in OK storage cases after lenses had been soaked for approximately 6 hr. After the first assessment, the lens wearers were informed of the extent of case contamination and the possible risk of microbial keratitis (MK), and best practices for lens care and lens case hygiene were reviewed and reinforced. A second assessment by the same DHA method was performed after approximately 6 months.

Results:

Two universal bacterial probes confirmed a significant decrease in bacterial bioburden at the second assessment (P<0.01 and P<0.001). Genus-specific probes showed significant reductions in Acinetobacter and Klebsiella (P=0.02 and P=0.01), but not in Pseudomonas (P=0.42).

Conclusions:

Making OK lens wearers aware of the bacterial bioburden in their lens cases resulted in improved quality of case care and reduced bioburden. Our results suggest that a strategy of bioburden assessment with forewarning could be a useful method to decrease the incidence of OK-related MK.

Safety and comfort evaluation of a new formulation of Visine(®) lubricant eye drops containing HydroBlend™ and GentlePur™

PURPOSE

To evaluate the clinical safety and comfort of a new benzalkonium chloride-free Visine(®) lubricant eye drop formulation (Hydroblend™ and GentlePur™) in healthy and dry eye subjects.

METHODS

This was a single-site, open-label clinical study comprised of 22 healthy and 22 dry eye subjects. Subjects were instructed to instill 1-2 drops of the test product four times a day for 2 weeks and were examined at visit 1 (day 0), visit 2 (day 7), and visit 3 (day 14). Assessments at each visit included postdosing product usage comfort scores, predosing fluorescein corneal staining score, predosing visual acuity, and pre- and postdosing ocular structure change using slit-lamp biomicroscopy. Adverse events were monitored throughout the course of the study.

RESULTS

Throughout the 14 days of the trial period, subjects from both healthy and dry eye groups rated the eye drops as "very comfortable". For dry eye group, the mean product usage comfort scores for the first 3 minutes postdosing ranged from 8.5 to 8.8 at visit 1 and 9.2 to 9.6 at visit 3 on a 0-10 point scale, with 0 being very uncomfortable and 10 being very comfortable. The mean corneal staining scores over five corneal regions changed from 0.65 at visit 1 to 0.39 at visit 3 for dry eye group. The individual region corneal staining scores were also decreased from visits 1 to 3 for dry eye group. All subjects maintained pretreatment means visual acuity at visits 2 and 3. Biomicroscopic examination indicated no structural changes at all visits. There were no significant adverse events reported during the course of the study.

CONCLUSION

The study confirms that GentlePur™ is an appropriate choice as a preservative for ocular application. The new formulation was safe and comfortable when used four times a day in healthy and dry eye subjects.

Adhesion of Pseudomonas aeruginosa to orthokeratology and alignment lenses

PURPOSE

To determine whether contact lenses designed for orthokeratology (OK) are colonized by greater numbers of bacteria compared with standard (alignment fitted) design rigid gas permeable lenses before and after lens wear.

METHODS

Eighteen 1-year-old cats were randomly fitted with an OK lens in one eye and an alignment fitted (AF) lens in the other eye. Both lenses were made in the same diameter and central thickness and of the same material. Two separate wearing periods of 2 weeks and 6 weeks were used. After each wearing period, lenses were soaked in Pseudomonas aeruginosa (6294 or 6206) for 10 min. The lenses were then reinserted onto their respective corneas for a wearing period of 16 hours after which lenses were collected and remaining adhered bacteria quantified. Unworn control lenses were also soaked and bacteria enumerated for comparison.

RESULTS

There were no significant differences in the number of bacteria adherent to unworn AF and OK lenses. Analysis of lenses after wear showed OK lenses retained significantly higher numbers of viable bacteria than AF lenses in all studies.

CONCLUSIONS

OK lenses retain more bacteria than AF rigid gas permeable lenses after bacteria-loaded overnight lens wear. This may increase the risk for an infection in OK patients should suitable conditions be present. Specific education on the cleaning of OK lenses is essential.