In vitro adhesion of Acanthamoeba castellanii to soft contact lenses depends on water content and disinfection procedure

PurposeTo compare the potential of different soft contact lenses to be contaminated with Acanthamoeba castellanii as a function of material parameters and cleaning procedures.MethodsDifferent unworn soft hydrogel and silicone hydrogel contact lenses were incubated with human pathogenic A. castellanii. The adhesion of the acanthamoebae was investigated on the contact lenses and put into relation to their material parameters. The efficacy of a recommended contact lens cleaning procedure in reducing A. castellanii adhesion was investigated.ResultsWe found that material parameters such as elastic modulus, silicone content, ionic properties and swelling do not influence the adhesion of acanthamoebae to soft contact lenses. A material parameter that influenced adhesion significantly was the water content of the lens. With increasing water content, the adhesion of acanthamoebae increased. By following the cleaning instructions of the manufacturer the contamination of the lenses with A. castellanii could be reduced to a minimum, as shown both on contact lenses and in control experiments.ConclusionWith this study we show that for the tested lenses, the adhesion of A. castellanii to contact lenses is independent of the silicone content of the lens, but depends nonlinearly on the water content of the lens. Furthermore, we demonstrate that applying proper lens cleaning procedures minimizes the risk of acanthamoebae adhesion to contact lenses.     

Sustainable extraction of proteins and bioactive substances from pomegranate peel (Punica granatum L.) using pressurized liquids and deep eutectic solvents

Pomegranate peel is a source of proteins, bioactive peptides, and phenolic compounds. The simultaneous extraction of these compounds required the use of polluting solvents and reagents that are non-suitable. This work targets the development of green methodologies based on pressurized liquids (PLE) or deep eutectic solvents (DES) for the extraction of these compounds. Extracts were digested with different proteolytic enzymes and different functionalities (antioxidant, hypocholesterolemia, and antihypertensive capacities) were evaluated. Highly antioxidant and hypocholesterolemic extracts and hydrolysates were obtained using PLE while high antihypertensive capacity was observed in the hydrolysates from proteins extracted using DES. Peptides and polyphenols were identified by HPLC-ESI-Q-TOF/MS. Higher amounts of peptides were shown in hydrolysates from DES extracts while hydrolysates from PLE extracts presented higher amounts of phenolic compounds. Some peptides were assigned to proteins from Punica granatum. Both green methods improved the extraction of bioactive compounds from pomegranate peel compared to the non-sustainable method.Industrial relevanceThe development of green methodologies which employ sustainable solvents such as pressurized liquids (PLE) and deep eutectic solvents (DES) allows extracting proteins and bioactive compounds from pomegranate peel. In addition, these solvents improve the extraction of health beneficial compounds compared to the non-sustainable and polluting solvents. Therefore, they could be used for the development of nutraceuticals and functional foods or even in medicinal, cosmetic, and pharmaceutical preparations.     

Efficacy of spherical aberration correction based on contact lens power

PurposeTo investigate the efficacy of spherical aberration (SA) correction with aspheric contact lenses (aspheric lenses) based on lens power, and compare the results with those of spherical contact lenses (spherical lenses).MethodsOcular higher-order aberrations were measured with a wavefront sensor, in 11 myopic subjects wearing an aspheric lens (Medalist Fresh fit (PUREVISION 2 HD); Bausch + Lomb) or a spherical lens (ACUVUE Oasys; Johnson & Johnson). Six different lens powers (−7.00 diopters (D), −5.00 D, −3.00 D, −1.00 D, +1.00 D, +3.00 D) were used for all subjects. The amount of SA correction from the contact lens at each power was calculated as the difference between SA with the contact lens on-eye and SA of the eye alone.ResultsFor the spherical lenses, SA correction was close to 0.00 μm for the +1.00 D lens, became more positive as the labeled lens power increased and became more negative as the labeled lens power decreased. For the aspheric lenses, SA correction was consistent, from −0.15 to −0.05 μm, for all lens powers except for the −1.00 D lens. SA correction for the spherical and aspheric lenses was significantly different at −7.00 D (p = 0.040), −3.00 D (p = 0.015), −1.00 D (p < 0.001), +1.00 D (p = 0.006), and +3.00 D (p < 0.001) powers.ConclusionAn aspheric lens is capable of correcting SA at different lens powers, and has SA correction in the range of −0.15 to −0.05 μm over a 6 mm aperture.     

Extraction of bioactive compounds from Curcuma longa L. using deep eutectic solvents: In vitro and in vivo biological activities

In this work, deep eutectic solvents (DES-based menthol and cholinium chloride) and the ethanol, temperature, and times were selected to extract bioactive compounds from the rhizome, leaves, and flowers Curcuma longa L., using ultrasound-assisted extraction. Analyzes antioxidant, flavonoids, antimicrobial, chelation Fe²⁺, inhibition of the cholinesterase's enzymes, cytotoxicity, and genotoxicity in Allium cepa cells were performed. The extracts showed results of iron chelation and antibacterial. Curcuma flowers and leaves' extracts inhibited food spoilage bacteria with values above 45%, with substantial iron-chelating activity above 50%. Extracts obtained by DES based on menthol and lactic acid exhibited a high percentage of inhibition of acetyl and butyryl cholinesterase. In contrast, flower extracts obtained by menthol and acetic acid showed low inhibition of cholinesterase enzyme activity. No extract showed cytotoxicity and genotoxicity. Biological activities showed a high potential for the application of these extracts in the food and pharmaceutical industries.     

Lens parameter changes under in vitro and ex vivo conditions and their effect on the conjunctiva

PurposeTo quantify changes in contact lens parameters induced by lens wear and determine whether these changes are associated with contact lens-induced conjunctival staining (CLICS).MethodsIn vitro: Lens diameter, sag, edge shape, base curve of six contact lens brands (balafilcon, comfilcon, etafilcon, lotrafilcon B, omafilcon and senofilcon) measured at 21 °C and 35 °C (eye temperature). Ex vivo: Diameter of lenses collected from a prospective, randomised, contra-lateral, cross-over clinical trial from 36 subjects wearing all lens types for 1 week daily wear, measured in 35 °C PBS after removal. Ocular surface was examined for lens-induced conjunctival staining by masked examiner.ResultsIn vitro: Changes in diameter and base curve outside ISO tolerance were found with etafilcon A and omafilcon A. Ex vivo: Comfilcon A and etafilcon A had greatest shrinkage in diameter (0.18 mm) and base curve (0.11 mm steeper) with temperature increase from 21 °C to 35 °C. Senofilcon A, lotrafilcon B and balafilcon A maintained most stable parameters between 21 °C and 35 °C. Changes in diameter and base curve from lens wear were not correlated with CLICS (p > 0.49). Multivariate analysis showed significantly greater levels of lens induced staining were associated with lens modulus (p < 0.001) and knife (p < 0.001) and chisel (p < 0.001) edge shapes.ConclusionsParameter changes induced by lens wear were associated with increasing temperature, but these changes in lens diameter and base curve did not induce CLICS. Modulus and edge shape were associated with increased CLICS. The susceptibility of etafilcon A and omafilcon A lenses to parameter changes might be related to their high water content.     

Predicting estimates of oxygen transmissibility for scleral lenses

Background/PurposeAlthough scleral contact lenses are prescribed with increasing frequency, little is known about their long-term effects on ocular physiology. The main goal of this paper is to predict values of oxygen transmissibility of scleral lens systems by applying the concept of resistors in series to parameters characteristic of current scleral lenses. A second aim is to find the maximal lens and post-lens tear layer thickness combinations above which hypoxia-induced corneal swelling would be found.MethodsTheoretical calculations were used to predict the oxygen transmissibility of scleral lens systems, considering several material permeabilities (Dks 100–170), varying lens thicknesses (250–500 μm), the known tear permeability (Dk of 80) and expected post-lens tear layer thicknesses (100–400 μm). The Holden–Mertz Dk/t criteria of 24 Fatt units for the central cornea and the Harvitt–Bonanno criteria of 35 Fatt units for the limbal area were used as reference points.ResultsOur calculations of oxygen transmissibility, with varying tear layer and lens thicknesses, ranged from 10 to 36.7 at the scleral lens centers and from 17.4 to 62.6 at the peripheries. Our calculations of maximum central lens thicknesses show a practical range of 250–495 μm, in conjunction with a post-lens tear layer thickness of 100–250 μm.ConclusionOur computations show that most modern scleral lenses, with recommended fitting techniques, should lead to some level of hypoxia-induced corneal swelling. Recommendations are made to minimize hypoxia-induced corneal swelling: highest Dk available (>150) lens with a maximal central thickness of 250 μm and fitted with a clearance that does not exceed 200 μm.     

A pilot study investigating the effect of extended contact lens wear on limbal and central corneal morphology

PurposeTo investigate the effect of long-term extended soft contact lens wear on limbal and central corneal cell morphology, and limbal architecture.MethodsEach participant attended a study visit involving in vivo confocal microscopy of central corneal and limbal epithelium. Scans were graded by five masked graders for three features: central epithelial irregularity, limbal epithelial irregularity and the prominence of palisades of Vogt. The variability of grades between different graders and the difference of grades between extended wearers and daily soft/non-contact lens wearers were assessed.ResultsNineteen participants (9 extended soft contact lens wearers and 10 daily soft/non-contact lens wearers) aged 31–65 years were enrolled in this study. Scans from 37 eyes were included in the analysis. Agreement between graders for each feature was moderate to good with inter class correlation >0.7. While there were no significant differences in central epithelial cell irregularity (p = 0.527) and the prominence of palisade of Vogt (p = 0.182) between extended or daily soft/non-contact lens wearers, limbal epithelial cell irregularity showed a trend with increased irregularity in extended soft contact lens wearers (p = 0.091).ConclusionsWhile no differences in limbal cell morphology and structure or central epithelial cell was found in this subjective grading study of extended wearers compared to daily soft/non-contact lens wearers, further studies using a larger sample size or a longitudinal study design are warranted.     

Comparison of conventional method of contact lens fitting and software based contact lens fitting with Medmont corneal topographer in eyes with corneal scar

PurposeTo compare conventional method of contact lens fitting with software based contact lens fitting using Medmont corneal topographer in eyes with nebular and macular corneal scars.MethodsFifteen participants who were diagnosed with nebular and macular scars were fitted with rigid gas permeable lenses using conventional method of contact lens fitting. During the lens dispensing visit, participants underwent Medmont corneal topography. Agreement between the two methods of contact lens fitting was studied.ResultsParameters of contact lenses which were concluded using conventional method was compared to that of software based fitting. Mean difference in base curve of contact lens between the two methods was 0.094 mm ± 0.147 mm (95% CI: +0.383 to −0.194). Mean difference in diameter of contact lens between the two methods was 0.16 mm ± 0.172 mm (95% CI: +0.497 to −0.177). Contact lens parameters that were achieved using two different methods of fitting showed good correlation. Correlation coefficients, as comparison of two methods in base curve and diameter were 0.96 (P < 0.05) and 0.94 (P < 0.05), respectively.ConclusionSoftware based contact lens fitting would be useful for contact lens practitioners to predict initial base curve of contact lens in corneal scars.     

Acanthamoeba keratitis in patients wearing scleral contact lenses

Purpose

To report a series of cases of Acanthamoeba keratitis (AK) in scleral lens wearers with keratoconus to determine whether this type of contact lens presents a greater risk for development of infection. Methods: This study reports three patients who wore scleral contact lenses to correct keratoconus and developed AK. The diagnoses of AK were established based on cultures of the cornea, scleral contact lenses, and contact lens paraphernalia. This study investigated the risk factors for infections. Results: The possible risks for AK in scleral contact lens wearers are hypoxic changes in the corneal epithelium because of the large diameter and minimal tear exchange, use of large amounts of saline solution necessary for scleral lens fitting, storing the scleral lens overnight in saline solution rather than contact lens multipurpose solutions, not rubbing the contact lens during cleaning, and the space between the cornea and the back surface of the scleral lens that might serve as a fluid reservoir and environment for Acanthamoeba multiplication. Two patients responded well to medical treatment of AK; one is still being treated. Conclusions: The recommendations for use and care of scleral contact lenses should be emphasized, especially regarding use of sterile saline (preferably single use), attention to rubbing the lens during cleaning, cleaning of the plunger, and overnight storage in fresh contact lens multipurpose solutions without topping off the lens solution in the case.     

Preparation,characterization and antimicrobial study of a hydrogel (soft contact lens) material impregnated with silver nanoparticles

PurposeContact lenses that incorporate antimicrobial properties may reduce the risk for microbial-associated adverse events for lens wearers. The aim of this study was to assess the antimicrobial effects of silver nanoparticles (NP) when impregnated in a hydrogel material.MethodsHydrogel disks, used as a proxy for soft contact lenses, were prepared with silver NPs to add an antimicrobial effect to the polymer. Six groups of disks were created, each with a different concentration of silver NPs. The antimicrobial effect of the hydrogels against Pseudomonas aeruginosa (ATCC15442) and Staphylococcus aureus (ATCC6538) was evaluated at 6, 24, 48 and 72 h.ResultsSilver NP concentrations ranged from 20.71 to 98.06 μg/disk. All groups demonstrated excellent antibacterial effects against P. aeruginosa at each time point. After 6 h all disks didn’t exhibit desirable antibacterial activity against S. aureus; whereas except those with 20.71 μg silver NPs showed antibacterial activity at 24 h and only the disks with 57.13 and 98.06 μg silver NPs showed antimicrobial activity at 48 and 72 h.ConclusionsThe development of contact lenses made of a silver NP-impregnated hydrogel material may bring antimicrobial effects sufficient to decrease the risk of microbial-related adverse events for lens wearers.     

Randomized crossover trial of silicone hydrogel contact lenses

PurposeThe aim of the current study is to assess, using new technologies, the interaction of four monthly silicone hydrogel contact lenses on the ocular surface and the comfort over 15 days of use.MethodsProspective cross-over, randomized and double-masked study including four materials (lotrafilcon-B, samfilcon-A , comfilcon-A and filcom-V3). Clinical examination was performed in the following order: tear meniscus height, first break-up of the tear film, the average time of all tear film breakup incidents, bulbar redness, limbal redness (Keratograph 5M ,Oculus, Germany); central corneal thickness (Pentacam, Oculus, Germany), thermography values (FLIR A325; FLIR Systems Inc., USA), and slit-lamp evaluations, including ocular surface staining. Finally, subjective comfort was obtained from Contact Lens Dry Eye Questionnaire-8.ResultsThe impact of contact lens wear on the ocular surface didn’t show statistically significant changes over time except for corneal and conjunctival staining grades on day 15 compared to day 1 for the comfilcon A group (P = .003 and P = .01, respectively). Contact lens stability and impact on the ocular surface during contact lens wear didn’t show statistically significant changes over time except in the case of the comfilcon A material with respect to the irritation item (P = .01).ConclusionsThese results suggest that the impact of monthly silicone hydrogel contact lens materials on the ocular surface after and during contact lens wear, contact lens stability over time, and subjective comfort did not reveal any significant changes over 15 days of use for any of the materials.     

Reduced contamination and infection via inhibition of adhesion of foodborne bacteria to abiotic polystyrene and biotic amoeba surfaces

Adhesion of foodborne pathogens to materials of industrial surfaces is an important step in their transmission through the food chain. Adhesion is also a prerequisite for bacterial colonisation within a host, to enable intracellular invasion. We define a strategy to reduce contamination and infection by Listeria monocytogenes, Campylobacter jejuni and Escherichia coli using an ethanol extract of Alpinia katsumadai seeds (AlpE) and epigallocatechin gallate (EGCG) as anti‐adhesive agents. We show for the first time that AlpE and EGCG reduce adhesion of individual cultures to polystyrene (AlpE, up to 10.6%; EGCG, up to 39.7%) and to the amoeba Acanthamoeba castellanii (AlpE, up to 52.6%; EGCG, up to 53.4%). The combination of AlpE/EGCG significantly reduced C. jejuni adherence to the abiotic (45.5%) and biotic (52.2%) surfaces. Thus, using natural agents from plants at low doses, we can potentially reduce the primary source of food contamination and a frequent source of infections.     

Uptake and release of polyhexamethylene biguanide (PHMB) from hydrogel and silicone hydrogel contact lenses using a radiolabel methodology

PurposeThe purpose of this study was to evaluate the uptake and release of radiolabelled polyhexamethylene biguanide (PHMB) on reusable daily wear contact lenses (CLs) over 7 days.MethodsThree silicone hydrogel (SH) contact lens materials (lotrafilcon B, balafilcon A, senofilcon A) and two conventional hydrogel (CH) materials (etafilcon A, omafilcon A) were examined. In experiment 1 (1-day study), CLs were soaked in 2 mL of phosphate buffered solution (PBS) containing radiolabelled ¹⁴C PHMB (1 µg/mL) for 8 h. The release kinetics of ¹⁴C PHMB from the CLs was measured at t = 0.25, 0.5, 1, 2, 4, 8, and 24 h in fresh 2 mL PBS. In experiment 2 (7-day study), the CLs were soaked in the ¹⁴C PHMB (1 µg/mL) solution for 8 h followed by a 16-hour release in 2 mL PBS. The lens cycle was repeated daily for 7 days. After both experiments, the residual amount of PHMB remaining within the lenses was extracted to determine the total uptake of PHMB.ResultsIn experiment 1, the total uptake of PHMB for etafilcon A was significantly greater than senofilcon A (p = 0.01). There were no significant differences in total uptake of PHMB between other lens materials (p > 0.05). Etafilcon A released more PHMB compared to all other lens types over a 24-hr period (p < 0.001). In experiment 2, all CL materials continued to sorb more PHMB over time (p < 0.001). By day 7, the amount of PHMB sorbed by etafilcon A was significantly greater than senofilcon A (p = 0.02). After day 2, the CH materials released significantly more PHMB than the SH materials (p < 0.01).ConclusionThe CL materials continued to sorb PHMB with no signs of saturation after 7 days. All lens materials released a consistent amount of PHMB each day. Radioactive labelling provides a sensitive method of assessing the uptake and release of PHMB from CL materials.     

Comparison of fitting stability of the different soft toric contact lenses

PurposeTo compare lens orientation and rotational recovery of five currently available soft toric lenses.MethodsTwenty subjects were recruited and trialed with each of the study lenses in a random order. Study lenses were PureVision^® Toric (B&L), Air Optix^® for Astigmatism (Alcon), Biofinity^® Toric (CooperVision), Acuvue^® Advance for Astigmatism (Vistakon), and Proclear^® Toric (CooperVision). Lens orientation in primary position to determine the lens rotation form the vertical position and rotational recovery to primary gaze orientation following a 45° manual misorientation for the different lenses was compared.ResultsThe Biofinity Toric showed the lowest rotation from the vertical position and the Proclear Toric the highest. Also, the highest and the lowest reorientation speed were related to the Biofinity Toric and the Acuvue Advance for Astigmatism, respectively. The Repeated Measures ANOVA showed a significant difference in the lens rotation (P = 0.004) and rotational recovery (P < 0.001) among different contact lenses and the performed multiple comparisons indicated differences in rotation and also in reorientation speed were only seen between the Biofinity Toric when compared to four other lenses (P < 0.05).ConclusionAlthough there was appropriate fitting, based upon lens orientation and reorientation speed, with each of the study lenses it would appear that the optimized ballast technique used in the design of the Biofinity Toric helps reduce lens rotation and improve rotational recovery compared to others.     

Which soft contact lens power is better for piggyback fitting in keratoconus?

PurposeTo evaluate the impact of differente soft contact lens power in the anterior corneal curvature and regularity in subjects with keratoconus.MethodsNineteen subjects (30 eyes) with keratoconus were included in the study. Six corneal topographies were taken with Pentacam Eye System over the naked eye and successively with soft lens (Senofilcon A) powers of −3.00, −1.50, 0.00, +1.50 and +3.00 D. Corneal measurements of mean central keratometry (MCK), maximum tangential curvature (TK), maximum front elevation (MFE) and eccentricity (Ecc) at 6 and 8 mm diameters as well as anterior corneal surface high order aberrations (i.e. total RMS, spherical- and coma-like and secondary astigmatism) were evaluated.ResultsNegative- and plano-powered soft lenses flattened (p < 0.05 in all cases), whereas positive-powered lenses did not induce any significant changes (p > 0.05 in all cases) in MCK in comparison to the naked eye. The TK power decreased with negative lenses (p < 0.05 in both cases) and increased with +3.00 D lenses (p = 0.03) in comparison to the naked eye. No statistically significant differences were found in MFE with any soft lens power in comparison to the naked eye (p > 0.05 in all cases). Corneal eccentricity increased at 8 mm diameter for all lens powers (p < 0.05 in all cases). No statistically differences were found in HOA RMS and spherical-like aberration (both p > 0.05). Statistically differences were found in coma-like and secondary astigmatism (both p < 0.05).ConclusionNegative-powered soft contact lenses provide a flatter anterior surface in comparison to positive-powered lenses in subjects with keratoconus and thus they might be more suitable for piggyback contact lens fitting.     

Effect of material and care system combination on subclinical inflammation of the ocular surface in soft contact lens wear

PurposeTo investigate the ocular subclinical inflammatory response in two soft contact lens materials when used in combination with two different care systems (‘solutions’).MethodsFifteen established soft contact lens wearers wore each of two lenses: Acuvue® 2 (CH) and Acuvue® Oasys® (SiH) or no lenses in random sequence for one week. Two care systems were used: a peroxide system: Oxysept 1 Step® (P) for the right lens and Opti-Free® Replenish® (MPS) for the left lens. After one week of lens/no lens wear, in vivo confocal microscopy (IVCM) of corneal and conjunctival regions was carried out. Density of presumed dendritic cells (DC) and ‘white spots’ (WS) were quantified. Impression cytology of the bulbar and upper eyelid margin conjunctivae was carried out and samples were analysed for CD45+, CD3+ and CD11c+ cells.ResultsThe SiH + MPS combination showed a greater inflammatory response compared to SiH + P in seven out of 12 parameters investigated (p < 0.05). The remaining five were not statistically different between the two solutions. The converse was found for the CH lens, with four of the 12 parameters showing a greater response with the P solution compared to the MPS (p < 0.05).ConclusionThis study suggests that the SiH lens investigated demonstrated an upregulated response when used with a MPS compared to a P solution whereas the converse is true for the CH lens which showed a reduced response when used with a MPS compared to a P solution. This finding aids in the understanding of the biological underpinnings of manifest corneal inflammatory events during contact lens wear.     

Evaluating the effect of splitting cylindrical power on improving patient tolerance to toric lens misalignment

PurposeEvaluating the impact of splitting toric power on patient tolerance to misorientation such as with intraocular lens rotation.SettingUniversity vision clinic.MethodsHealthy, non astigmats had +1.50D astigmatism induced with spectacle lenses at 90°, 135°, 180° and +3.00D at 90°. Two correcting cylindrical lenses of the opposite sign and half the power each were subsequently added to the trial frame misaligned by 0°, 5° or 10° in a random order and misorientated from the initial axis in a clockwise direction by up to 15° in 5° steps. A second group of adapted astigmats with between 1.00 and 3.00DC had their astigmatism corrected with two toric spectacle lenses of half the power separated by 0°, 5° or 10° and misorientated from the initial axis in both directions by up to 15° in 5° steps. Distance, high contrast visual acuity was measured using a computerised test chart at each lens misalignment and misorientation.ResultsMisorientation of the split toric lenses caused a statistically significant drop in visual acuity (F = 70.341; p < 0.001). Comparatively better acuities were observed around 180°, as anticipated (F = 3.775; p = 0.035). Misaligning the split toric power produced no benefit in visual acuity retention with axis misorientation when subjects had astigmatism induced with a low (F = 2.190, p = 0.129) or high cylinder (F = 0.491, p = 0.617) or in the adapted astigmats (F = 0.120, p = 0.887).ConclusionMisalignment of toric lens power split across the front and back lens surfaces had no beneficial effect on distance visual acuity, but also no negative effect.     

Predicting success with silicone-hydrogel contact lenses in new wearers

Purposeto evaluate changes in tear metrics and ocular signs induced by six months of silicone-hydrogel contact lens wear and the difference in baseline characteristics between those who successfully continued in contact lens wear compared to those that did not.MethodsNon-invasive Keratograph, Tearscope and fluorescein tear break-up times (TBUTs), tear meniscus height, bulbar and limbal hyperaemia, lid-parallel conjunctival folds (LIPCOF), phenol red thread, fluorescein and lissamine-green staining, and lid wiper epitheliopathy were measured on 60 new contact lens wearers fitted with monthly silicone-hydrogels (average age 36 ± 14 years, 40 females). Symptoms were evaluated by the Ocular Surface Disease Index (OSDI). After six months full time contact lens wear the above metrics were re-measured on those patients still in contact lens wear (n = 33). The initial measurements were also compared between the group still wearing lenses after six months and those who had ceased lens wear (n = 27).ResultsThere were significant changes in tear meniscus height (p = 0.031), bulbar hyperaemia (p = 0.011), fluorescein TBUT (p = 0.027), corneal (p = 0.007) and conjunctival (p = 0.009) staining, LIPCOF (p = 0.011) and lid wiper epitheliopathy (p = 0.002) after six months of silicone-hydrogel wear. Successful wearers had a higher non-invasive (17.0 ± 8.2 s vs 12.0 ± 5.6 s; p = 0.001) and fluorescein (10.7 ± 6.4 s vs 7.5 ± 4.7 s; p = 0.001) TBUT than drop-outs, although OSDI (cut-off 4.2) was also a strong predictor of success.ConclusionSilicone-hydrogel lenses induced significant changes in the tear film and ocular surface as well as lid margin staining. Wettability of the ocular surface is the main factor affecting contact lens drop-out.     

A comparison of regimen methods for the removal and inactivation of bacteria, fungi and Acanthamoeba from two types of silicone hydrogel lenses

Purpose

To compare the antimicrobial efficacy of commercial contact lens solutions when used according to the manufacturers’ recommended regimens with two types of silicone hydrogel lenses.

Methods

Four multipurpose contact lens care solutions were examined, representing manufacturer recommended regimens of “rub & rinse”, “no rub, rinse” or “no rub, no rinse”. Test organisms were Pseudomonas aeruginosa, Serratia marcescens, Staphylococcus aureus, Fusarium solani, Candida albicans and Acanthamoeba castellanii (trophozoites and cysts). Organisms, in the presence of organic soil, were inoculated on to Acuvue Oasys or Air Optix lenses and subjected to the solution manufacturer's recommended regimen. The number of surviving organisms on the lenses and in the soak solution was enumerated in accordance with ISO 14729.

Results

ISO 14729 dictates that for a given organism the combined average number of surviving microbes from the lenses and disinfectant soaking solution must be ≤10 colony forming units (cfu)/ml. By this criterion, only Complete Easy Rub (“rub & rinse” regimen) gave satisfactory results for all bacteria, fungi and Acanthamoeba with both lens types. Solutions employing “no rub, rinse” were less satisfactory but significantly better than “no rub, no rinse”. Significant differences were found in organism survival on the lenses with greater numbers remaining on the Air Optix compared to Oasys (p < 0.01-0.0001).

Conclusion

The findings of this study demonstrate that the use of a manual rubbing step is more effective than rinsing or soaking alone in removing pathogenic microbes from silicone hydrogel lenses. Accordingly, it would seem prudent to recommend that contact lens care systems include a rub step as part of the hygiene regimen.