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.     

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.     

A comparative study of visual function of young myopic adults wearing contact lenses vs. spectacles

PurposeTo evaluate the impact of contact lenses wear vs. spectacles wear on visual function of young adults with mild to moderate myopia.Methods57 students (27 male and 30 female) with a mean age of 23 years old participated in the study. Their mean best corrected visual acuity was 10/10 binocularly, all suffered from mild to moderate myopia (?3.75 sph/SD 1.25 sph) and they were both contact lenses and spectacles wearers. The VF-14 questionnaire was administered to assess the contact lenses wear vs. spectacles wear impact score on general daily living among the young individuals. It was used translated in Greek after following the ‘translation-back translation’ procedure.ResultsThe mean VF-14 score among spectacles and contact lenses wearers was 100 and 86.78 (SD 4.08) respectively. Although there was a significant difference between the two groups (p < 0.05), both scores were related to a satisfactory functional vision for daily living. The contact lenses wearers were facing difficulty especially while driving at night, seeing steps, as well as doing fine handwork (i.e. sewing, knitting or carpentry).ConclusionsThe use of both spectacles and contact lenses provides satisfactory visual functioning for daily activities in young individuals suffering from mild to moderate myopia. However, there is a spectacles’ wear superiority in personal satisfaction when compared to contact lenses.     

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.     

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.     

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).     

Ethnic differences in dry eye symptoms: Effects of corneal staining and length of contact lens wear

PurposeTo explore the relationships among length of contact lens (CL) wear, degree of corneal staining and severity of dryness symptoms, and to determine whether these relationships differ between Asians and non-Asians.MethodsAdapted soft CL wearers (n = 395; 180 Asian, 215 non-Asian) were required to discontinue CL wear for at least 24 h and report to the University of California, Berkeley Clinical Research Center (UCB-CRC). Fluorescein corneal staining was graded according to Brien Holden Vision Institute scales. Length of CL wear was reported by subjects and subjective dryness ratings were collected using the UCB-CRC Dry Eye Flow Chart (DEFC).ResultsMore Asian CL wearers exhibited corneal staining compared to non-Asians, and Asian CL wearers had a higher mean grade of corneal staining (p < 0.001), as well as a higher mean DEFC classification (p < 0.001). The difference between Asians and non-Asians in grades of corneal staining extent and depth were significant (p < 0.001). Among non-Asian CL wearers, dryness symptoms decreased with more years of CL wear and increased in the presence of corneal staining, which was not the case for Asian CL wearers.ConclusionsAsian soft CL wearers reported more severe dryness symptoms and demonstrated more severe corneal staining overall compared to non-Asians. Among non-Asians, dryness symptoms were less severe on average with increased years of CL wear and more severe in the presence of corneal staining. Dryness severity does not appear to be related to years of CL wear or corneal staining among Asians.     

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.     

Comparative study of the structural and physicochemical properties of two food derived antihypertensive tri-peptides,Isoleucine-Proline-Proline and Leucine-Lysine-Proline encapsulated into a chitosan based nanoparticle system

Food derived tri-peptides; Leucine-Lysine-Proline (LKP) and Isoleucine-Proline-Proline (IPP) are angiotensin converting enzyme inhibitors and may have potential to alleviate hypertension. The aim of this work was to understand the interactions of IPP and LKP when formulated into a chitosan nanoparticle (NP) to help improve permeation. Our findings indicate different mean inhibitory concentrations (LKP: 0.36 ± 0.01 μM and IPP: 3.1 ± 0.6 μM) and encapsulation efficiencies at different ratios of chitosan: tripolyphosphate (LKP NPs: 65% at 6:1 and IPP NPs: 43% at 4:1). Molecular modelling and circular dichroism showed different stable amino side-chain-specific conformations for each peptide. IPP showed more steric hindrances to intra-chain rotations, resulting in an unordered peptide structure, whereas LKP showed more flexibility associated with a (disordered) β-strand-like conformer. In-vitro release kinetics showed a slower release for LKP NPs in acidic pH compared to IPP NPs. In conclusion, LKP NPs were found to have better binding compatibility with chitosan.     

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.     

Inactivation of Escherichia coli O157:H7 by cinnamic aldehyde purified from Cinnamomum cassia shoot

Escherichia coli O157:H7 is a pathogen, which causes the hemorrhagic colitis, hemolytic uremic syndrome and thrombotic thrombocytopenic purpura in humans. Control of the bacterial cells in foods is an important factor to reduce outbreaks of the foodborne diseases. In this study, cinnamic aldehyde possessing antimicrobial activity against the bacterial cells was purified from the extract of cinnamon (Cinnamomum cassia Blume) shoot by sequential fractionation with various solvents and silica gel column chromatography. When E. coli O157:H7 cells were incubated at 37°C for 12 h in the presence of 500 μg ml⁻¹ of the purified from cinnamic aldehyde, the viable counts decreased dramatically (from 4.9×10⁶ to 1.0×10² cfu ml⁻¹). In the presence of 1000 μg ml⁻¹ of the substance, most of the cells were killed after 2 h of incubation suggesting that the antimicrobial activity of cinnamic aldehyde is bacteriocidal in E. coli. Scanning electron microscopic observations revealed that the bacterial cells treated with the cinnamic aldehyde suffered from severe damages in their surface structure. Minimal inhibitory concentration of the cinnamic aldehyde was determined to be 250 μg ml⁻¹ against E. coli strains O157:H7 and O26 or 500 μg ml⁻¹ against strains ATCC11105 and O111.     

Evaluation of central corneal thickness after cataract surgery,penetrating keratoplasty and long-term soft contact lens wear

PurposeThe aim of this study was to compare central corneal thickness (CCT) between corneas of normal healthy eyes (cNHE), corneas of eyes that had undergone cataract surgery by clear corneal phacoemulsification with implantation of an intracapsular intraocular lens (cIOL), corneal grafts after penetrating keratoplasty (gPK) and corneas of long-term soft contact lens wearers (cCL).MethodsThe study design was a consecutive cross-sectional trial. CCT was measured using rotating Scheimpflug camera (Pentacam, software version 1.16r04) in 80 cNHE, 79 cIOL, 46 gPK and 78 cCL. Analysis of variance (one-way ANOVA) was performed to compare differences of mean values between these four groups. Pearson's or Spearman's correlation coefficient (r) was determined between CCT value and age, follow up time after penetrating keratoplasty (timePK) or contact lens wearing time (timeCL).ResultsMeans of CCT measurements were comparable between cNHE (mean CCT ± standard deviation, 554 ± 36 μm), cIOL (551 ± 40 μm) and gPK (534 ± 52 μm) as determined by one-way ANOVA. Mean CCT values in cCL (537 ± 37 μm) were statistically significantly lower in comparison to cNHE (p = 0.026, 95% CI = 1.43–31.44). There was no linear correlation between age and CCT values of cNHE and cIOL (p = 0.841, r = −0.031 and p = 0.931, r = 0.011, respectively). No linear relationship was determined between CCT values of cCL and timeCL (p = 0.315, r = −0.125). CCT values of gPK did not correlate with timePK (p = 0.738, r = 0.054).ConclusionsThe data reported here indicate that in the same statistical model among CCT values of cNHE, cIOL and gPK only long-term soft contact lenses (CL) wearer have significantly lower CCT measurements.     

Antimicrobial activity of whey protein based edible films incorporated with oregano,rosemary and garlic essential oils

The use of edible films to release antimicrobial constituents in food packaging is a form of active packaging. Antimicrobial properties of spice extracts are well known, however their application to edible films is limited. In this study, antimicrobial properties of whey protein isolate (WPI) films containing 1.0–4.0% (wt/vol) ratios of oregano, rosemary and garlic essential oils were tested against Escherichia coli O157:H7 (ATCC 35218), Staphylococcus aureus (ATCC 43300), Salmonella enteritidis (ATCC 13076), Listeria monocytogenes (NCTC 2167) and Lactobacillus plantarum (DSM 20174). Ten millilitres of molten hard agar was inoculated by 200 μl of bacterial cultures (colony count of 1 × 10⁸ CFU/ml) grown overnight in appropriate medium. Circular discs of WPI films containing spice extracts, prepared by casting method, were placed on a bacterial lawn. Zones of inhibition were measured after an incubation period. The film containing oregano essential oil was the most effective against these bacteria at 2% level than those containing garlic and rosemary extracts (P < 0.05). The use of rosemary essential oil incorporated into WPI films did not exhibit any antimicrobial activity whereas inhibitory effect of WPI film containing garlic essential oil was observed only at 3% and 4% level (P < 0.05). The results of this study suggested that the antimicrobial activity of some spice extracts were expressed in a WPI based edible film.     

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.     

Corneal changes following short-term rigid contact lens wear

PurposeThe aim of this cross-over study was to investigate the changes in corneal thickness, anterior and posterior corneal topography, corneal refractive power and ocular wavefront aberrations, following the short term use of rigid contact lenses.MethodFourteen participants wore 4 different types of contact lenses (RGP lenses of 9.5 mm and 10.5 mm diameter, and for comparison a PMMA lens of 9.5 mm diameter and a soft silicone hydrogel lens) on 4 different days for a period of 8 h on each day. Measures were collected before and after contact lens wear and additionally on a baseline day.ResultsAnterior corneal curvature generally showed a flattening with both of the RGP lenses and a steepening with the PMMA lens. A significant negative correlation was found between the change in corneal swelling and central and peripheral posterior corneal curvature (all p ≤ 0.001). RGP contact lenses caused a significant decrease in corneal refractive power (hyperopic shift) of approximately 0.5 D. The PMMA contact lenses caused the greatest corneal swelling in both the central (27.92 ± 15.49 μm, p < 0.001) and peripheral (17.78 ± 12.11 μm, p = 0.001) corneal regions, a significant flattening of the posterior cornea and an increase in ocular aberrations (all p ≤ 0.05).ConclusionThe corneal swelling associated with RGP lenses was relatively minor, but there was slight central corneal flattening and a clinically significant hyperopic change in corneal refractive power after the first day of lens wear. The PMMA contact lenses resulted in significant corneal swelling and reduced optical performance of the cornea.     

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.     

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.     

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.     

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.     

Stabilized nanosilver based antimicrobial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) nanocomposites of interest in active food packaging

Antimicrobial silver based nanocomposites of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) were successfully synthesized and characterized. For the synthesis, a masterbatch of in situ stabilized silver nanoparticles (AgNPs) produced into a mixed microbial cultures based poly(3-hydroxybutyrate-co-18 mol%-3-hydroxyvalerate) (PHBV18) was used, which was diluted by melt compounding with a commercial poly(3-hydroxybutyrate-co-3 mol%-3-hydroxyvalerate) (PHBV3) material. The incorporated AgNPs (0.04 wt.%) led to a surprising oxygen permeability drop of ca. 56% compared to the neat polymer. The thermal stability and optical properties of the nanocomposites were not significantly modified as compared to the neat PHBV3. Moreover, the antimicrobial performance of the PHBVs-AgNPs films against two of the most common food borne pathogens, Salmonella enterica and Listeria monocytogenes, showed a strong and sustained (even after seven-months) antibacterial activity. This study provides an innovative route to generate fully renewable and biodegradable antimicrobial nanocomposites that could potentially be of interest in film and coating applications such as active food packaging.Industrial relevanceAs a response to the consumers for more safety foodstuffs and ecofriendly packaging materials, this work presents a novel methodology to develop antimicrobial packaging by using biodegradable materials obtained from industrial food by-products in combination of an industrially meaningful melt blending process. The methodology here applied allows the use of low doses of stabilized silver nanoparticles in the polymer matrix, without additives, which exhibits prolonged antimicrobial activity against food borne pathogens and enhanced oxygen barrier properties. These materials are of great interest in the development and design of biodegradable active food packaging materials and antibacterial food contact surfaces with the additional advantage that they can be easily scale-up.