The role of multi-purpose solutions in prevention and removal of lipid depositions on contact lenses

Multi-purpose Disinfecting Solutions only Partially Inhibit the Development of Ocular Microbes Biofilms in Contact Lens Storage Cases

PURPOSE

Certain ocular resident or pathogenic microbes may remain viable in the presence of multi-purpose disinfectant solutions (MPDSs), subsequently developing biofilms inside contact lens storage cases (CLSCs) which pose a risk of infection to wearers. This study evaluated the formation of ocular microbiota biofilms exposed to three top selling MPDS.

METHODS

Crystal violet assay was carried out for the verification of biofilm formation. The in vitro assays evaluated Pseudomonas aeruginosa UFPEDA 416 and Staphylococcus aureus UFPEDA 02 exposure of 48 h to MPDS, as well as the use of 40 KHz ultrasound at the beginning and with 24 h immersion in the MPDS. Subsequently, in vivo assays evaluated the formation of microbial biofilms on the CLSC walls containing silicone-hydrogel contact lenses immersed in MPDS from 15 healthy volunteer patients, who had been wearing the lenses for 7 days.

RESULTS

Biofilms were inhibited by 26%-98% in the in vitro assays, with a statistically significant difference only for P. aeruginosa UFPEDA 416 exposed to diluted MPDS. Most inhibitions occurred moderately and weakly. In addition, adherent cells were detected in more than 90% of the tests. Biofilm was not inhibited in more than one third of the results, nor was it disturbed, especially with the ultrasound treatments. The average of obtained optical densities at 590 nm was between 0.6 and 0.8 in the in vivo assays. The results were similar between the CLSC right and left wells. There was a correlation between microbial biofilm formation and the type of MPDS tested, with statistical difference between the three treatments.

CONCLUSION

MPDS promoted a partial inhibition of microbial biofilm formation but only one MPDS proved to be more effective in vitro and in vivo. This study, however, could not distinguish the effect of possible errors in the good hygiene practices of the users.

Uptake and Release of a Multipurpose Solution Biocide (MAP-D) From Hydrogel and Silicone Hydrogel Contact Lenses Using a Radiolabel Methodology

PURPOSE

The purpose of this study was to evaluate the uptake and release of radiolabelled myristamidopropyl dimethylamine (MAP-D) on reusable daily wear contact lenses (CLs) over 7 days.

METHODS

Three silicone hydrogel (SH) CL materials (lotrafilcon B, balafilcon A, senofilcon A) and two conventional hydrogel (CH) materials (etafilcon A, omafilcon A) were tested. A short-term (experiment 1, N=4) and a longer-term (experiment 2, N=3) study was conducted. In experiment 1, the CLs were incubated in 2 mL of phosphate buffered solution (PBS) containing 14C MAP-D (5 μg/mL) for 8 hrs. The release of 14C MAP-D was measured at t=0.25, 0.5, 1, 2, 4, 8, and 24 hr in PBS. In experiment 2, the CLs were incubated in the 14C MAP-D solution for 8 hrs followed by a 16-hr release in PBS. This cycle was repeated daily for 7 days. At the end of both experiments, lenses were extracted to determine the total uptake of MAP-D. The radioactivity was measured using a beta scintillation counter.

RESULTS

In experiment 1, all three SH lenses sorbed similar amounts of MAP-D (P=0.99), all of which were higher than the two CH materials (P<0.01). However, the CH materials released a greater amount of MAP-D than the SH materials (P<0.01). In experiment 2, the uptake of MAP-D in SH materials increased over 7 days, whereas the amount of MAP-D remained constant in the CH materials (P=0.99). Similar to experiment 1, the CH lenses released more MAP-D than SH lenses after 7 days (P<0.01).

CONCLUSION

The SH materials absorbed greater amounts of MAP-D compared to CH materials. However, the CH materials released the greatest amount of MAP-D. Radioactive labelling of MAP-D offers a highly sensitive method of assessing the uptake and release profiles of biocides to CL materials.

Kinetic Deposition of Polar and Non-polar Lipids on Silicone Hydrogel Contact Lenses

Purpose: This study investigated kinetic lipid uptake to four silicone hydrogel (SiHy) lenses over a period of four weeks, using an in-vitro radiolabel method. Methods: Four contemporary monthly replacement SiHy lenses (lotrafilcon B, senofilcon C, comfilcon A, samfilcon A) were incubated in three different solutions: 1) An artificial tear solution (ATS) containing ¹⁴C-labeled phosphatidylcholine (PC), 2) an ATS containing ¹⁴C-cholesteryl oleate (CO) and 3) an ATS containing four ¹⁴C-radiolabeled lipids (PC, phosphatidylethanolamine, CO, and cholesterol (total lipid)). After 16 hours, lipids were extracted twice from the lenses with chloroform:methanol and the radioactive counts determined the lipid quantities to simulate 1 day of wear. OPTI-FREE PureMoist (Alcon) was used to clean and disinfect the remaining lenses daily and the lipid quantities were further determined after 2 weeks and 4 weeks. Results: The amount of total lipid increased for all lenses over time (p < .01). After four weeks, total lipid accumulated was 20.26 ± 0.15 µg/lens for senofilcon C, which was significantly higher (p < .01) than all other lens materials (samfilcon A - 17.84 ± 0.21; comfilcon A - 16.65 ± 0.12; lotrafilcon B - 7.41 ± 0.56 µg/lens). CO was highest on lotrafilcon B (1.26 ± 0.13 µg/lens) and senofilcon C attracted the most PC (3.95 ± 0.12 µg/lens) compared to the other materials. Conclusion: The amount of both polar and non-polar lipid deposition on monthly replacement SiHy lenses increased over 4 weeks, with significant differences being seen between lens materials.

Efficacy of Contact Lens Care Solutions in Removing Cholesterol Deposits From Silicone Hydrogel Contact Lenses

PURPOSE

To determine the efficacy of multipurpose solutions (MPSs) on the removal of cholesterol deposits from silicone hydrogel (SH) contact lens materials using an in vitro model.

MATERIALS AND METHODS

Five SH lens materials: senofilcon A, comfilcon A, balafilcon A, lotrafilcon A, and lotrafilcon B were removed from the blister pack (n=4 for each lens type), incubated for 7 days at 37°C in an artificial tear solution containing C radiolabeled cholesterol. Thereafter, lenses were stored in a preserved saline solution control (Sensitive Eyes Saline Plus) or cleaned with 1 of the 5 MPSs incorporating different preservatives (POLYQUAD/ALDOX, polyquaternium-1/alexidine, polyquaternium-1/PHMB, and 2 based on PHMB alone) using a rub and rinse technique, according to the manufacturer's recommendations, and stored in the MPS for a minimum of 6 hr. Lenses were then extracted with 2:1 chloroform:methanol, analyzed in a beta counter, and μg/lens of cholesterol was determined.

RESULTS

Balafilcon A and senofilcon A lens materials showed the highest amounts of accumulated cholesterol (0.93±0.02 μg/lens; 0.95±0.01 μg/lens, respectively), whereas lotrafilcon A and lotrafilcon B deposited the lowest amounts (0.37±0.03 μg/lens; 0.47±0.12 μg/lens, respectively). For all lens materials, the MPS preserved with POLYQUAD/ALDOX removed more deposited cholesterol than any other test solution; however, the amount of removed cholesterol contamination from the individual contact lenses was only statistically significant for balafilcon A and senofilcon A (P=0.006 and P=0.042, respectively). Sensitive eyes and the other evaluated MPSs showed no significant effect on cholesterol removal (P>0.05).

CONCLUSION

Cholesterol-removal efficacy varies depending on the combination of lens material and solution. Only 1 MPS showed a statistically significant reduction of cholesterol deposit for only 2 of the 5 tested lens materials.