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

The sorption and desorption of radiolabeled dipalmitoylphosphatidylcholine (DPPC) and cholesterol (CH) were measured on 5 types of commercial contact lenses. The lenses were soaked in vitro in an artificial tear fluid for 16 h. The effects of borate buffered saline and two commercial multi-purpose lens-care solutions (MPSs) on reducing the lipid (DPPC and CH) sorption and increasing the lipid removal were examined. The results showed that silicone hydrogel (SiHy) lenses accumulated the most lipids, sorbing over an order of magnitude more than polymacon, a conventional hydrogel lens. Pre-soaking the SiHy lenses for 16 h in MPSs reduced the DPPC sorption by up to 13% and the CH sorption by up to 11%, compared to controls that were not pre-soaked. However neither these reductions nor those on polymacon were statistically significant (p > 0.05). In sorption experiments without presoaking, subsequent exposure to the MPSs removed some DPPC from the lenses (0–3.1% for SiHy lenses and 14–55% for polymacon), but CH removal was 0.0–0.8% for SiHy lenses and 0.6–28% for polymacon lenses. Some of these removals were statistically significant (p < 0.05).     

Pressurized low polarity water extraction of lignans from whole flaxseed

The application of pressurized low polarity water (PLPW) extraction to the production of flaxseed lignans-rich products has been studied, and the key geometric and process conditions, including temperature, flow rate, and total volume have been determined and optimized. Maximum amounts of lignans and other flaxseed bioactive, including proteins were extracted at 160 °C and 5.2 MPa. However, on a dry weight basis the most concentrated extracts in terms of lignans and other phenolic compounds were obtained at 140 °C and 5.2 MPa. A flow rate of 0.5 mL/min was optimal for the extraction of lignans from flaxseed (Linum usitatissimum L.) and a total volume of 30–40 mL/g of seed was required to maximize the recovery. Higher flow rates increased the rate of the extraction but required larger water volumes. Bed depth to ID ratios of 5–18 resulted in faster extraction and maximum recovery (90–95%) at water to seed ratios of 30–50 mL/g. Larger depth to ID ratios (15–18) would allow the use of lower solvent to solid ratios (14–20 mL/g) and would still result in yields of 84–90%.     

Functional hydrogel microspheres: Parameters affecting electrostatic assembly of biopolymer particles fabricated from gelatin and pectin

Hydrogel microspheres may be used for various applications within foods, cosmetics, and pharmaceuticals, such as texture modification, encapsulation, or controlled release. The aim of this research was to examine the key parameters affecting the formation and properties of hydrogel microspheres fabricated by electrostatic complexation of gelatin and pectin. Hydrogel microspheres were formed by mixing 0.5 wt% gelatin and 0.01 wt% pectin at pH 10.0 and 30 °C, and then acidifying to pH 5.0 with continuous stirring. The effects of salt content (0–100 mM NaCl), shear rate (150–600 rpm), and acidification rate (fast, medium, and slow) on the formation and properties of the hydrogel microspheres were investigated. Increased salt content perturbed the complexation process due to electrostatic screening and ion-binding effects, which meant that lower pH values were needed to induce complexation. Optical microscopy and static light scattering showed that salt content also altered hydrogel particle microstructure. The largest particles were formed at an intermediate shear rate (300 rpm), which was attributed to the influence of shearing on mixing, particle disruption, and particle coalescence. Hydrogel microsphere size decreased as the acidification rate increased, which was attributed to an alteration in the balance of particle formation and particle growth. The parameters identified in this study facilitate the design of hydrogel microspheres with specific sizes and morphologies, which might be useful for tailoring their functional properties for different commercial applications.     

Trend of soft contact lens prescribing in an optometry centre in India: A 6-year analysis

This six-year retrospective longitudinal study was conducted to examine the changes in the pattern of prescribing soft contact lenses in an optometry centre located in a University in South India. Details regarding the type of lenses, lens material, wearing pattern and the clinical diagnoses were analyzed from January 2006 to December 2011. A total of 1273 soft contact lens fits (n = 1273) were analyzed. Two-third of the total lenses dispensed was for females and their mean age (24.0 ± 8.3 yrs) was less than that of male (27.0 ± 11.2 yrs) lens users. Nearly 70% of them had myopia and 48% wore conventional soft contact lenses. During the studied six years, the percentage of conventional lenses declined by 60%. This study demonstrated a gradual and significant increase in popularity of disposable contact lenses and silicone hydrogel lens material which is comparable to the global trend.     

Efficacy of two silicone-hydrogel contact lenses for bandage use after photorefractive keratectomy

PurposeTo evaluate the efficacy of two silicone hydrogel (SiH) contact lenses, approved for continuous wear for one week, following photorefractive keratectomy (PRK).MethodsForty seven myopic patients (94 eyes) undergone bilateral PRK were enrolled in this prospective, double-masked, comparative study. One eye of each patient was fitted with a Lotrafilcon B lens (Ciba Vision, Duluth, US; 30-day recommended replacement) whereas the fellow eye was fitted with an Asmofilcon A lens (Menicon, Nagoya, Japan; 14-day recommended replacement). Epithelial defect size was assessed using slit lamp biomicroscopy on the day of surgery and at days 1–4 post-operatively. Uncorrected and best-corrected visual acuity and retinal straylight (C-Quant, Oculus Optigerate, Germany) were evaluated pre-operatively and one month post-operatively.ResultsAverage epithelial defect size for Asmofilcon A and Lotrafilcon B was 25.5 ± 11.0 mm² vs. 27.1 ± 9.9 mm² at day 1 (p = 0.007) and 6.3 ± 7.0 mm² vs. 9.2 ± 9.5 mm² at day 2 (p = 0.012) post-operatively. Re-epithelialization at day 3 was completed in 87.2% of the eyes fitted with Asmofilcon A lenses, compared to 74.5% with Lotrafilcon B lenses (p = 0.012). At the 3rd post-operative day 29.8% of re-epithelialized eyes showed irregular suture with Lotrafilcon B, compared to 12.8% eyes with Asmofilcon A lenses (p < 0.001). Finally, no statistically significant differences were found post-operatively between the two lenses retinal straylight (p = 0.98) and best-corrected visual acuity (p = 0.68).ConclusionsSiH lenses can be used as an effective bandage after PRK due to the limited time requested for achieving complete corneal re-epithelialization. Faster and smoother epithelial healing is provided with Asmofilcon A over Lotrafilcon B lenses.     

The use of daily disposable lenses in problematic reusable contact lens wearers

PurposeReplacing soft contact lenses (CLs) on a daily basis brings a number of advantages, most notably, reduced exposure to deposits, disinfectants, allergens, and other contaminants. This retrospective study estimated the prevalence of problems in current wearers of reusable soft CLs and tested the effect of refitting “problem” patients with daily disposable (DD) hydrogel lenses.MethodsPrevalence was estimated from 398 current reusable CL wearers for: frequent/constant discomfort or dryness, ≥2 h of uncomfortable wear, ≥grade 2 conjunctival hyperaemia (0–4), or ≥grade 3 corneal staining (0–15). In the second part of the study, 217 reusable CL wearers classified as problem patients were randomly refitted with DD lenses manufactured from one of two materials: etafilcon A (n = 96) or nelfilcon A (n = 121) and reassessed 1 week later.ResultsThirty-nine percent (154/398) had some qualifying criterion: reduced comfortable wearing time (CWT), 20%; dryness, 20%; irritation, 5%; corneal staining, 8%; and hyperaemia, 7%. After refitting with DDs, the prevalence of reduced CWT was decreased from 65% to 51% (P = 0.0039), dryness from 60% to 41% (P < 0.0001) and corneal staining from 28% to 21% (P = 0.04). There was no significant change in the prevalence of irritation, or hyperaemia. Some differences were noted between the two lens materials.ConclusionsA high proportion of reusable soft lens wearers encounter clinically relevant signs or symptoms with their current CLs. This study provides evidence that refitting with DD lenses is a useful strategy for alleviating some of the common problems of CL wear.     

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.     

Objective and subjective visual performance of multifocal contact lenses: Pilot study

PurposeThe aim of the present study was to compare the objective and subjective visual performance of three different soft multifocal contact lenses.Methods10 subjects (habitual soft contact lens wearers) between the ages of 40 and 45 years participated in the study. Three different multifocal silicone hydrogel contact lenses (Acuvue Oasys, Air Optix and Biofinity) were fit within the same visit. All the lenses were fit according to the manufacturers’ recommendation using the respective fitting guide. Visual performance tests included low and high contrast distance and near visual acuity, contrast sensitivity, range of clear vision and through-focus curve. Objective visual performance tests included measurement of open field accommodative response at different defocus levels and optical aberrations at different viewing distances.ResultsAccommodative response was not significantly different between the three types of multifocal contact lenses at each of the accommodative stimulus levels (p > 0.05). Accommodative lag increased for higher stimulus levels for all 3 types of contact lenses. Ocular aberrations were not significantly different between these 3 contact lens designs at each of the different viewing distances (p > 0.05). In addition, optical aberrations did not significantly differ between different viewing distances for any of these lenses (p > 0.05). ANOVA revealed no significant difference in high and low contrast distance visual acuity as well as near visual acuity and contrast sensitivity function between the 3 multifocal contact lenses and spectacles (p > 0.05).ConclusionsThere was no statistically significant difference in accommodative response, optical aberrations or visual performance between the 3 multifocal contact lenses in early presbyopes.     

Contact lens prescribing pattern in India—2011

PurposeTo understand the pattern of prescribing contact lenses (CL) among Indian practitioners.MethodsSurvey forms were sent to 257 practitioners across the country to collect information about their last 10 CL fits, location and type of practice, years of experience and educational qualification. A logistic regression analysis was performed to determine any association of various factors to the lens fitting pattern and chi-square test was used to compare proportions. The data were analyzed using SPSS v.16.ResultsCL fitting details from 227 practitioners were acquired representing a total of 2270 fits. The mean age of patients was 26.8 ± 7.4 years and 67% of them were females. Ninety-eight percent of patients wore soft CL comprising 24% toric lenses. Ninety percent patients preferred disposable modality with 65% of these opting for monthly disposable lenses. Twenty-eight percent of the lenses dispensed were silicone hydrogel (SiH) lenses. Optometry practices located in metropolitan cities dispensed significantly higher numbers of disposable (p < 0.001) and SiH lenses (p < 0.001). Logistic regression analysis showed Fellowship of International Association of Contact Lens Educators (FIACLE) (OR: 13.79, 95% CI: 2.61–72.70), post graduate degree (OR: 3.87, 95% CI: 0.87–17.12) and years of experience were directly associated with fitting of advanced CL.ConclusionThe CL prescribing patterns in India elicited from this survey suggest the dominance (90%) of prescribing of disposable soft CL. Higher level of education, greater experience and a FIACLE status were significantly associated with advanced fitting.     

The accuracy of Goldmann applanation tonometry over silicone hydrogel contact lenses in patients with glaucoma

PurposeTo investigate the accuracy of measuring intraocular pressure over a silicone hydrogel contact lens using Goldmann applanation tonometry in eyes with glaucoma.MethodsThis was a prospective, randomized study and enrolled 28 patients (28 right eyes) with primary open angle glaucoma. Intraocular pressure was taken with and without a silicone hydrogel contact lens (−0.50 D), in situ (using Goldmann applanation tonometry), in a randomized order of measurements. Statistical analysis was performed using paired t-test and Bland–Altman plot.ResultsThe mean difference (± standard deviation) found between intraocular pressure measurement without (mean 16.7 ± 3.2 mmHg) and with (mean 17.3 ± 3.0 mmHg) contact lens was found to be −0.57 ± 2.3 mmHg (95% confidence interval, −1.5 to 0.3). No significant statistical difference was found between the two groups with paired t-test (p = 0.19). The Bland Altman plot showed some evidence of increasing variability of differences between two measures of intraocular pressure, with increasing intraocular pressure. The 95% limits of agreement of the Bland Altman plot were unacceptably large (−5 mmHg to 3.9 mmHg).ConclusionAgreement between Goldmann applanation tonometry with and without contact lenses seems to be poor in patients with glaucoma, especially for high intraocular pressure.     

Supercritical fluid extraction of black pepper oil

The supercritical fluid extraction (SFE) of oil from ground black pepper, using supercritical carbon dioxide (SC CO₂) as a solvent, is presented in this study. The effect of process parameters, namely pressure (90, 100, 150 bar) and temperature (40, 50 °C) of extraction, and solvent flow rate (1.1, 2, 3 kg/h), on the extraction rate was examined in a series of experiments conducted in a bench scale apparatus. The results indicated a significant increase of extraction rate with increase of pressure or decrease of temperature. A similar effect was observed with the increase of solvent flow rate. The experimental data were satisfactorily correlated by two mass balance models. The first one is based on the Lack’s plug flow model, which accounts for both the solubility and diffusion controlled regimes of the extraction, and the second one on the adsorption–desorption equilibrium of solute from solid tissue, the diffusion of the solute dissolved in the supercritical solvent to the surface and the mass transfer through the external film into the bulk.     

An acute clinical comparison of corneal staining and comfort associated with contact lens care solutions

PurposeThis study compared the biocompatibility and comfort of 4 lens care solutions currently marketed in France.MethodsThis was a randomized, interventional, double-masked, single-center crossover study assessing balafilcon A silicone hydrogel contact lenses, bilaterally, straight from the blister pack solution (control) and pre-soaked in the following lens care solutions: Regard^® (containing sodium chlorite), ReNu^® (containing a PHMB [polyhexamethylene biguanide] derivative), CyClean™ and MeniCare™ Soft (both containing PHMB). Subjects were randomized to the order of test solution use. For each of the 5 solutions tested, subjects attended a baseline/lens dispensing visit and an intervention visit 2 h later. At both visits, evaluation included slit-lamp examination, corrected-distance visual acuity, corneal staining, and subject-assessed photophobia, ocular comfort, and ocular redness.ResultsThirty subjects were enrolled and 28 were evaluable. Corneal staining severity was significantly worse than baseline after 2 h of wearing lenses soaked in CyClean, MeniCare, or ReNu (P ≤ 0.001). The MeniCare group alone demonstrated a significant improvement in ocular comfort after 2 h of lens wear (P = 0.02). No group demonstrated significant changes in ocular redness or photophobia. Corrected-distance visual acuity was similar between baseline and intervention visits for each test solution. No adverse events were reported during the study.ConclusionsSilicone hydrogel contact lenses presoaked in lens solutions containing PHMB or a PHMB derivative produced an increase in corneal staining after 2 h of lens wear. The higher levels of corneal staining in the 2 solutions did not correlate with increased discomfort within this 2-h timeframe.     

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.     

Encapsulation,protection, and release of polyunsaturated lipids using biopolymer-based hydrogel particles

Delivery systems are needed to encapsulate polyunsaturated lipids, protect them within food products, and ensure their bioavailability within the gastrointestinal tract. Hydrogel particles assembled from food-grade biopolymers are particularly suitable for this purpose. In this study, hydrogel microspheres were fabricated by electrostatic complexation of low methoxy pectin and caseinate by decreasing the solution pH from 7 to 4.5. After hydrogel particle formation, the caseinate was enzymatically cross-linked using transglutaminase to improve the stability of the biopolymer matrix. The effect of hydrogel particle encapsulation on the physical location, chemical stability, and lipase digestibility of emulsified polyunsaturated lipids (fish oil) was investigated. The cross-linked hydrogel particles formed using this process were relatively small (D₄₃ = 4.6 μm), negatively charged (ζ = − 37 mV), and evenly distributed within the system. Confocal microscopy confirmed that the fish oil droplets were trapped within casein-rich hydrogel microspheres. Encapsulation of the fish oil droplets improved their stability to lipid oxidation compared to conventional emulsions, which was attributed to a high local concentration of antioxidant protein around the emulsified lipids. The rate and extent of digestion of the encapsulated lipid droplets within a simulated small intestine were similar to those of non-encapsulated ones. These results suggest that casein-rich hydrogel microspheres may protect polyunsaturated lipids in foods and beverages, but release them after ingestion.     

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.     

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.     

The effect of tinted soft contact lens wear on functional visual acuity and higher-order aberrations

PurposeTo investigate the differences of functional visual acuity (FVA) and high order aberrations (HOAs) in relation to tinted and clear hydrogel soft contact lens (SCL) wear.MethodsA prospective comparative study was performed in 16 eyes of 16 healthy volunteers. Dynamic visual acuity (using a FVA measurement system) and higher-order aberrations (using a wavefront sensor) were compared in subjects wearing two types of soft contact lenses: 1-day Acuvue^® (Vistakon, Jacksonville, FL) clear and the 1-day Acuvue^® Define^TM (Vistakon, Jacksonville, FL) tinted lens. The blink rates were recorded during FVA testing. The correlation between the difference of HOAs and differences in FVA values was analyzed.ResultsThe mean LogMAR FVA scores with clear and tinted SCLs were 0.07 ± 0.13 and 0.14 ± 0.17 (P < 0.05). The mean blink frequencies with clear and tinted SCL wear were 18.4 ± 8.3 and 25.3 ± 4.7 blinks/min (P < 0.05). Both 3rd-order aberrations and total HOAs showed statistically significant differences between the two types of soft contact lenses for 6 mm pupil measurements (P < 0.05). A significant positive linear correlation was observed between ΔHOAs and ΔLogMAR FVA for 6 mm pupil measurements (R = 0.53, P = 0.04).ConclusionsTinted contact lens wear appears to induce a reduction in optical quality. Functional visual acuity measurement is a useful procedure to study the changes of visual performance and quality in tinted contact lens wear.     

Spectral transmittance of UV-blocking soft contact lenses: A comparative study

BackgroundThree major parts of sunlight consist of visible, ultraviolet and infrared radiation. Exposure to ultraviolet radiation (UVR) can result in a spectrum of skin and ocular diseases. UV-blocking contact lenses help provide protection against harmful UV radiation. We studied the ultraviolet and visible light rays transmission in some soft UV-blocking contact lenses.Material and methodsFour available tinted soft lenses (Acuvue Moist, Zeiss CONTACT Day 30 Air spheric, Pretty Eyes and Sauflon 56 UV) have been evaluated for UV and visible transmission. One-way ANOVA testing was performed to establish is there a statistically significant difference between the UV regions and visible spectra means for the contact lenses (α = 0.05).ResultsPretty Eyes, Zeiss CONTACT, Acuvue Moist and Sauflon 56 UV showed UV-B transmittance value of 0.65%, 10.69%, 1.22%, and 5.78%, respectively. Pretty Eyes and Acuvue Moist had UV-A transmittance values of 32% and 34%, Sauflon 56 UV and Zeiss CONTACT had transmittance values of 48% and 43%, respectively. All of the studied lenses transmitted at least 94.6% on the visible spectrum. The results of the one-way ANOVA statistical analysis show that a statistically significant difference exists within the group of contact lenses tested for the visible (p < 0.001), UV-B (p < 0.001) and UV-A (p < 0.001) portions of the spectrum (α = 0.05).ConclusionAcuvue Moist has the best UV-blocking property and also visible transmission between other tested contact lenses in this study.     

Retinol binding to β-lactoglobulin or phosphocasein micelles under high pressure: Effects of isostatic high-pressure on structural and functional integrity

Embedding of bioactive molecules in food matrices is of interest for food industry to develop new foods or ingredients. The present study aims at deepening understanding of ligand binding to dairy proteins regarded as nano-vehicles, using pressure-assisted technological tools. We compared effects of isostatic high-pressure up to 350–400 MPa on the stability and the retinol-binding capacity of β-lactoglobulin (β-LG) or phosphocasein (PC) at pH 6.5–6.6. Retinol binding to β-LG changed the intrinsic protein and retinol fluorescence, characterised by fluorescence resonance-energy-transfer (FRET). After correction for inner filter effects, the FRET level estimated for the β-LG–retinol complex at pH 6.5 and P_atm was compatible with a retinol position at the β-LG surface cleft. Pressurisation of the β-LG–retinol complex induced an irreversible loss of the retinol-ligand above 150 MPa. Pressurisation of PC dispersion up to 200 MPa induced a marked decrease in the PC intrinsic fluorescence intensity with a concomitant red-shift of the spectral mass centre (CSM) explained by Trp residues exposure to aqueous solvent. The pressure-induced CSM half-transition (P_1/2) was 116 MPa for PC instead of 183 MPa for β-LG. Retinol binding to PC also resulted in important FRET, but PC assemblies partly retained retinol after pressure-release from 400 MPa. Interestingly, the pressure-induced dissociation rate of PC assemblies in the 15–35 °C temperature range was significantly accelerated at lower temperature, reflecting non-Arrhenius behaviour. PC particle sizes evaluated by dynamic light-scattering, confirmed that the pressure-induced dissociation was practically achieved at 200 MPa. Thus PC dissociation paralleled the structural changes determined by fluorescence spectroscopy.     

Overnight orthokeratology with two brands of reverse-geometry contact lenses

PurposeTo evaluate the refractive and corneal topographical changes of overnight orthokeratology in myopia with two brands of contact lenses.MethodsFourty-four eyes of 22 myopic patients with manifest refraction spherical equivalent (MRSE) of −1.00 to −5.00 D (cylinder ≤ −1.0) were fitted with either DreamLens (Hanita Lenses Investments, Hanita, Israel) (group A) or Rinehart–Reeves (R&R; Danker Laboratories, Sarasota, FL) (group B) reverse-geometry lenses. Each subject eye was evaluated in regards to the uncorrected and corrected distance visual acuities, manifest refraction, slit lamp biomicroscopy, and corneal topography at each follow-up examination.ResultsThe follow-up was 1 year. For groups A and B, the mean uncorrected distance visual acuity was −0.02 ± 0.10 log MAR (20/20) and −0.08 ± 0.12 log MAR (20/20) respectively at year-1 examination. The mean MRSE decreased from −2.70 ± 0.9 D to −0.50 ± 0.08 D in group A and −3.1 ± 1.1 to −0.62 ± 0.18 D in group B at week-1; and remained stable thereafter in each group. For both groups, starting with week-1, the mean anterior best-fit sphere (ABFS) was statistically significantly flatter from baseline. A high correlation was found between the change in apical corneal power (ACP) and MRSE (r₁ = 0.79, r₂ = 0.71), and there was a good correlation between the change in ABFS and MRSE (r₁ = 0.67, r₂ = 0.64) in both groups. No significant ocular adverse events were observed during study.ConclusionsBoth types of contact lenses safely and effectively decreased the myopic refractive error at 1 year follow-up. The refractive effect was mainly induced by the changes in the anterior corneal shape and the ACP.