Acuvue Advance Research Articles

Convective loading and release of latanoprost in silicone hydrogel contact lenses

Event Abstract Back to Event Convective loading and release of latanoprost in silicone hydrogel contact lenses William Pitt1, Ryan R. Horne1 and Kevin E. Judd1 1 Brigham Young University, Chemical Engineering Department, United States Statement of Purpose: We investigated the feasibility loading silicone hydrogel (SiHy) contact lenses with a hydrophobic anti-glaucoma drug, latanoprost, by swelling the lenses in a n-propanol solution of drug. Subsequent release into artificial tear solution (ATS) was measured. This study compares the loading and release of latanoprost in Acuvue Advance® (Johnson & Johnson Vision Care, Jacksonville, FL), Air Optix® (Alcon, Fort Worth, Texas) and Total Dailies 1® (Alcon). Methods: A 0.125 g/L n-propanol solution of radiolabeled latanoprost was made by dissolving latanoprost in n-propanol to which was added 5 µL of ethanol which contained 10 µCi of radioactive latanoprost. The loading procedure was performed at 25°C by removing a contact lens from its blister pack, rinsing with double-distilled water (DDH2O), blotting dry, immersing the contact lens in a loading solution for 240 seconds, immediately removing and washing the lens in 3 rinses for 5 seconds each in ~15 mL of DDH2O, and in ~5 mL of DDH2O for 15 minutes to allow for the lens to shrink to original size. The lens was moved either to a latanoprost extraction step or to ATS. Latanoprost extraction, a series of 2 soaks of 1 hr each in 2 mL n-propanol at 35°C, quantitated the radiolabeled latanoprost loaded into the lens, as described previously [1]. To simulating wear in ATS, the lens is immersed in 3 mL of ATS and swirled at 35°C. The lens was moved to fresh ATS after 1, 2, 4, and 6 days. A sample of ATS was taken for quantitation right before transferring the lens. Results: Latanoprost was successfully loaded into SiHy lenses. The drug showed 1st order release into artificial tears over a span of 2-3 days by which time the latanoprost was mostly depleted. For the same loading conditions, the amount of drug loaded and initial release rate were functions of the type of silicone hydrogel (see Figure 1). Of the lenses tested, Acuvue Advance® (galyfilcon A) accepted the most latanoprost and released at the fastest rates (p<0.05), followed by Air Optix® (lotrafilcon B) and Total Dailies 1® (delefilcon A) which released at similar rates. When normalized to the amount loaded, the kinetics of release of latanoprost were highly comparable for the different silicone hydrogels. Caption to Figure 1. Cumulative release of latanoprost per lens into ATS from different contact lenses . Error bars show the 95% CI, n=3. Conclusions: Literature reports of loading times for hydrophobic drugs are usually hours or days, [2] but this method allows for rapid loading of the drug latanoprost on the order of minutes. Despite a loading time of only 4 minutes, release is on the order of 2-4 days for the given conditions. We postulate that the hydrophobic character of SiHy contact lenses enables favorable interaction with the hydrophobic moieties of latanoprost, enhancing uptake during the loading process when latanoprost-solvating n-propanol in the polymer matrix is displaced by water, in which latanoprost is only minimally soluble. Loading and release was less for latanoprost than our previous findings for DMPC [1], which is consistent with latanoprost being less hydrophobic than DMPC. The amount of loading was higher in galyfilcon A which has 47% water content as compared to that of lotrafilcon B and delefilcon A, both having 33% water content. The higher loading is roughly correlated with the increase in water content of the polymer. Additional correlations of the silicone hydrogel chemistries and their potential effect on loading will also be presented. Funding for this study was provided by Brigham Young University.

Optical edge effects create conjunctival indentation thickness artefacts.

Conjunctival compression observed in ultrahigh resolution optical coherence tomography (UHR-OCT) images of contact lens edges could be actual tissue alteration, may be an optical artefact arising from the difference between the refractive indexes of the lens material and the conjunctival tissue, or could be a combination of the two. The purpose of this study is to image the artefact with contact lenses on a non-biological (non-indentable) medium and to determine the origins of the observed conjunctival compression. Two-dimensional cross-sectional images of the edges of a selection of marketed silicone hydrogel and hydrogel lenses (refractive index ranging from 1.40 to 1.43) were acquired with a research grade UHR-OCT system. The lenses were placed on three continuous surfaces, a glass sphere (refractive index n = 1.52), a rigid contact lens (n = 1.376) and the cornea of a healthy human subject (average n = 1.376). The displacement observed was analysed using ImageJ. The observed optical displacement ranged between 5.39(0.06) μm with Acuvue Advance and 11.99(0.18) μm with Air Optix Night & Day when the lens was imaged on the glass reference sphere. Similarly, on a rigid contact lens displacement ranged between 5.51(0.03) and 9.72(0.12) μm. Displacement was also observed when the lenses were imaged on the human conjunctiva and ranged from 6.49(0.80) μm for the 1-day Acuvue Moist to 17.4(0.22) μm for the Pure Vision contact lens. An optical displacement artefact was observed when imaging a contact lens on two rigid continuous surfaces with UHR-OCT where compression or indentation of the surface could not have been a factor. Contact lenses imaged in situ also exhibited displacement at the intersection of the contact lens edge and the conjunctiva, likely a manifestation of both the artefact and compression of the conjunctiva.

Conjunctival effects and blood flow changes related to silicone hydrogel lens wear and their relationship with end of day comfort

Purpose: First purpose was to determine if there was any relationship among lens fitting characteristics, conjunctival effects and blood flow changes with higher (PureVision 8.3, 8.6) and lower (Acuvue Advance 8.3, 8.7) modulus silicone hydrogel lenses. Second purpose was to correlate these changes with end of day comfort.

Visual and optical performance of silicone hydrogel contact lenses for moderate myopia

Purpose To compare the short-term visual and optical performance of silicone hydrogel contact lenses for myopia ≥ −3.00D. Methods This was a short-term, non-dispense, double-masked, randomized study investigating Night&Day (ND), PureVision (PV), O2 Optix (O2), Biofinity (BF), Acuvue Advance (AA) and Acuvue OASYS for myopia ≥ −3.00D. Testing was conducted under scotopic conditions. Measures (one eye only) included: high- and low-contrast visual acuity (HCVA/LCVA), contrast sensitivity, subjective clarity of vision ratings (0-100 scale using reference images, with test image representing grade 50) and ocular aberrations (up to the 4th order, analyzed across individual scotopic pupil sizes). Results Three males and 27 females participated, with a mean (± SD) age of 24.9 ± 7.7 yrs (range 19 to 53 yrs), sphere of −5.30 ± 1.73D (range −3.00 to −10.75D) and cylinder −0.36 ± 0.23D (range 0 to −0.75D). Mean (± SEM) logMAR HCVA ranged from 0.06 (PV) to 0.10 (AA) (± 0.02), LCVA from 0.33 (BF) to 0.40 (AA) (± 0.02) and contrast sensitivity from 2.33 (BF) to 2.53 (ND) (± 0.15) (differences not statistically significant; all p > 0.05). Subjective ratings for the test image ranged from 59 (PV) to 64 (ND) (± 4) and 56 (AA) to 65 (ND) (± 4), for monochromatic and polychromatic reference images, respectively (all p > 0.05). There was a statistically significant impact on ocular aberrations with all study lenses compared to no lens. Between-lens differences were statistically significant for defocus (Z 0 2), horizontal coma (Z 1 3) and spherical aberration (Z 0 4). Conclusions Despite some differences in ocular aberrations, there were no significant differences in HCVA, LCVA, contrast sensitivity or subjective ratings across lenses.

Alternaria and Paecilomyces Keratitis Associated With Soft Contact Lens Wear

To report a series of 5 patients with soft contact lens (SCL) related fungal keratitis caused by unusual organisms diagnosed at the Wills Eye Institute, Cornea Service in 2008. Chart review of patients with SCL related Alternaria and Paecilomyces keratitis diagnosed in 2008 was performed. Causes of these fungal infections were compared to previous years. During a period from 1999 to 2007, among 64 patients with fungal keratitis, Alternaria was isolated from one case after corneal foreign body removal in 2004, and Paecilomyces was not isolated in any of these patients. In 2008, however, 5 patients with SCL-related atypical fungal keratitis were diagnosed. Alternaria was isolated from 2 cases and Paecilomyces from 3 cases. All patients wore Acuvue SCL (Johnson & Johnson Vision Care): Acuvue Oasys, Acuvue Advance, and Acuvue 2 (1 case each) and Acuvue unspecified (2 cases). A total of 2 patients with Alternaria and 1 patient with Paecilomyces used ReNu or a generic-brand solution manufactured by Bausch & Lomb; 2 with Paecilomyces keratitis used Opti-free Replenish solution. A total of 3 patients wore lenses for daily wear and 2 wore them occasionally for overnight wear. The patients were treated with either voriconazole drops alone or combined with voriconazole 200 mg pills or Natamycin 5% drops. Three patients responded well to treatment. One patient with Paecilomyces keratitis developed a corneal perforation managed with tissue adhesive. One Paecilomyces keratitis patient required an emergency penetrating keratoplasty because of a perforated corneal ulcer present at the initial examination. We report 2 cases of Alternaria and 3 cases of Paecilomyces keratitis in patients wearing frequent replacement lenses and using multipurpose solutions diagnosed during 2008. We want to raise awareness of fungal keratitis caused by unusual organisms associated with SCL wear.

Corneal Topography and Soft Contact Lens Fit

To determine which ocular topography variables affect soft contact lens fit. Fifty subjects each wore three pairs of soft lenses in random succession (Vistakon Acuvue 2, Vistakon Acuvue Advance, Ciba Vision Night & Day), and various aspects of lens fit were evaluated. The steeper base curves of each type were worn in one eye and the flatter base curves in the other eye. Corneal topography data were collected using a Medmont E300 corneal topographer (Camberwell, Australia). Corneal curvature, shape factor (SF), and corneal height were measured over a 10 mm chord and also over the maximum measurable diameter. These were measured in the horizontal, vertical, steepest, and flattest meridians. With each lens type, the steeper base curve provided the best fit on the greatest proportion of eyes and the significant differences in various aspects of fit were noted between base curves. For each lens type, there was no significant difference in mean K-reading between those eyes best fit with the steeper base curve and those eyes best fit with the flatter base curve. Two of the lenses showed a positive correlation between centration and horizontal corneal height (maximum), whereas one lens showed a negative correlation between centration and horizontal SF (SF = e). Several lenses showed a positive correlation between post-blink movement and horizontal or vertical corneal SF. The measurement of corneal topography using current Placido disc instrumentation allows a better prediction of soft lens fit than by keratometry, but it is not reliable enough to enable accurate selection of the best fitting base curve. Some correlations are evident between corneal measurements; however, trial fitting remains the method of choice for selection of soft lens base curve.

Enzymatic Quantification of Cholesterol and Cholesterol Esters from Silicone Hydrogel Contact Lenses

The purpose of this work was to develop an enzymatic method of quantification of cholesterol and cholesterol esters derived from contact lenses, both in vitro and ex vivo. Lotrafilcon B (O2 Optix; CIBA Vision, Inc., Duluth, GA) and galyfilcon A (Acuvue Advance; Vistakon, Inc., Jacksonville, FL) silicone hydrogel contact lenses were independently incubated in cholesterol oleate solutions varying in concentrations. After incubation, the lenses were removed and underwent two separate 2:1 chloroform-methanol extractions. After in vitro studies, 10 human subjects wore both lotrafilcon B and galyfilcon A contact lenses for 7 days. The lenses also underwent two separate 2:1 chloroform-methanol extractions. All in vitro and ex vivo samples were quantified with a cholesterol esterase enzymatic reaction. Calibration curves from quantifications of in vitro contact lens samples soaked in successively decreasing concentrations of cholesterol oleate yielded coefficients of determination (R(2)) of 0.99 (lotrafilcon B) and 0.97 (galyfilcon A). For in vitro contact lens samples, galyfilcon A was associated with an average cholesterol oleate extraction of 39.85 +/- 48.65 microg/lens, whereas lotrafilcon B was associated with 5.86 +/- 3.36 microg/lens (P = 0.05) across both extractions and all incubation concentrations. For ex vivo contact lens samples, there was significantly more cholesterol and cholesterol esters deposited on galyfilcon A (5.77 +/- 1.87 microg/lens) than on lotrafilcon B (2.03 +/- 1.62 microg/lens; P = 0.0005). This is an efficient and simple method of quantifying total cholesterol extracted from silicone hydrogel contact lenses and, potentially, the meibum and/or tear film. Certain silicone hydrogel materials demonstrate more affinity for cholesterol and its esters than do others.

Ex Vivo Protein Deposition on Bi-Weekly Silicone Hydrogel Contact Lenses

This study investigated the protein deposition that occurs on daily wear silicone hydrogel (SH) lenses, after 2 weeks of wear. A total of 40 subjects were divided into equal groups, based on their habitual SH contact lens [CIBA Vision O2OPTIX (O2); Johnson & Johnson ACUVUE ADVANCE with HYDRACLEAR (ADV); Bausch & Lomb PureVision (PV); CIBA Vision Night & Day (ND)]. A randomized, double-masked, cross-over study was conducted in which subjects wore either their habitual SH material or Johnson & Johnson ACUVUE OASYS with HYDRACLEAR PLUS (OAS) for 2 weeks. At the end of the 2-week period, lenses were collected for analysis of total protein, total lysozyme, and percent denatured lysozyme. Total protein was greatest for PV (33 +/- 6 microg/lens), with other lenses depositing <10 microg/lens. The PV amount was greater than other materials (p < 0.001), with no significant differences between the other three materials (p > 0.05). Total lysozyme was also greatest for the PV lens (11 +/- 3 microg/lens), with other lenses depositing <2 microg/lens. The PV amount was greater than all other materials (p < 0.001). ADV and OAS were greater than O2 (p < 0.01) but were not different from each other (p > 0.05). The percentage of lysozyme that was denatured was greatest for ND (90 +/- 8%) and lowest for PV (23 +/- 10%). The lysozyme extracted from ND and O2 lenses was significantly more denatured than that extracted from the other lens materials (p < 0.001). There were no significant differences for lysozyme activity between ND and O2 (p > 0.05) or between ADV, OAS, and PV (p > 0.05). The amount of denatured lysozyme/lens was <3 microg/lens for all materials. Lysozyme as a percentage of the total protein deposited ranged from 32 (PV) to 6% (O2). This study confirms that all SH lenses deposit low levels of protein, and that the amount and percentage of denatured lysozyme can vary, depending on the overall surface charge of the material and absence or type of surface treatment.

Clinical Evaluation of Factors Affecting Soft Toric Lens Orientation

To evaluate the comparative orientation characteristics of currently available silicone hydrogel torics. The re-orientation characteristics of four toric lenses were assessed: three prism-ballasted (PB) designs, Purevision Toric (PVT), Air Optix Toric (AOT), Proclear Toric (PCT), and an "Accelerated Stabilization Design" (ASD) ACUVUE ADVANCE for Astigmatism (AAfA). In the first part of the study, the toric lenses were rotated, approximately 45 degrees in the infero-temporal direction and a video recording of lens reorientation was made from which blink-by-blink measurements of lens orientation were taken. In the second part of the study, subjects were positioned with their head orientated 90 degrees to the vertical and lens orientation photographed once it had settled. In Part 1, the speed of re-orientation from oblique mis location was similar for the four designs tested and ranged from 22°/min (PVT) to25°/min (AOT). Lenses showed more rotation during rather than between the blink (p<0.0001). Between blinks, AAfA and AOT showed significantly more rotation than PCT and PVT (p0.04). There were no significant differences between lenses for rotation during the blink. The PB lenses showed faster re-orientation further away from the zero position.AAfA showed no significant difference in rotation speed with varying orientation position. In Part 2, all the PB lenses rotated significantly more under the effect of gravity than the ASD lenses.The mean total rotation of the AAfA lenses,from their settled position, was 11.4° compared with 25.9° for PVT (p0.01), 18.4° with AOT (p0.02) and 37.4° with PCT (p0.0002) [corrected]. The mean total rotation of the AAfA lenses, from their settled position, was 11.2 degrees compared with 32.8 degrees for PVT (p < 0.001), 16.1 degrees with AOT and 33.1 degrees with PCT (p < 0.001). The four lens designs show similar re-orientation speeds. In the recumbent position, PB lenses rotate more from their normal settled position than ASD lenses.

Changes in UV-Visible Transmittance of Silicone-Hydrogel Contact Lenses Induced by Wear

To evaluate the influence of wear of silicone-hydrogel contact lenses on lens ultraviolet and visible spectrum transmittance by studying several contact lenses before and after wear. To investigate the ability of contact lenses to maintain their transmittance characteristics, we measured 104 different contact lenses in the ultraviolet (UV) and visible range from 200 to 700 nm, with a Shimadzu UV3101-PC UV-vis-NIR spectrophotometer equipped with an integrating sphere. The lenses used in this study were Acuvue Advance (Johnson & Johnson Vision Care, Inc.), Air Optix Night & Day (CIBA Vision), Air Optix (CIBA Vision), and PureVision (Bausch & Lomb). A conventional hydrogel contact lens was also tested, Acuvue (Johnson & Johnson Vision Care Inc.). Our study indicates that lenses that do not have UV absorbers incorporated into the polymer transmitted most of the UV radiation (UVR) before and after wear. The results of the statistical analysis show that for the UVC portion of the spectrum significant difference exists within the measurements obtained before and after wear for all the lenses, with the exception of PureVision. Acuvue Advance is the only material in which significant transmittance differences were observed in the visible spectral range. Transmittance is modified after contact lenses wear, probably due to the formation of biofilms on the contact lens surface, being more noticeable in the UVR region of the spectrum (200-400 nm). Silicone-hydrogel and conventional hydrogel contact lens materials that provide UVR protection (UV-blocker) maintain this property even after being worn. The changes observed in the visible spectrum seem not to have any implications in visual performance of silicone-hydrogel contact lenses.

Power Profiles and Short-Term Visual Performance of Soft Contact Lenses

To investigate the manner in which contemporary soft contact lenses differ in the distribution of optical power within their optic zones and establish if these variations affect the vision of wearers or the prescribing procedure for back vertex power (BVP). By using a Visionix VC 2001 contact lens power analyzer, power profiles were measured across the optic zones of the following contemporary contact lenses ACUVUE 2, ACUVUE ADVANCE, O2OPTIX, NIGHT & DAY and PureVision. Single BVP measures were obtained using a Nikon projection lensometer. Visual performance was assessed in 28 masked subjects who wore each lens type in random order. Measurements taken were high and low contrast visual acuity in normal illumination (250 Cd/m), high contrast acuity in reduced illumination (5 Cd/m), subjective visual quality using a numerical rating scale, and visual satisfaction rating using a Likert scale. Marked differences in the distribution of optical power across the optic zone were evident among the lens types. No significant differences were found for any of the visual performance variables (p > 0.05, analysis of variance with repeated measures and Friedman test). Variations in power profile between contemporary soft lens types exist but do not, in general, result in measurable visual performance differences in the short term, nor do they substantially influence the BVP required for optimal correction.

In Situ Visualization of Tears on Contact Lens Using Ultra High Resolution Optical Coherence Tomography

To demonstrate the capability of directly visualizing the tear film on contact lenses using optical coherence tomography (OCT). Six eyes of three healthy subjects wearing PureVision and ACUVUE Advance soft and Boston RGP hard contact lenses were imaged with a custom built, high speed, ultra-high resolution spectral domain optical coherence tomograph. Refresh Liquigel was used to demonstrate the effect of artificial tears on the tear film. Ultra high resolution images of the pre- and post-lens films were directly visualized when each lens was inserted onto the eye. After the instillation of artificial tears during lens wear, the tear film was thicker. The post-lens tear film underneath the lens edge was clearly shown. Interactions between the lens edges and the ocular surface were obtained for each of the lens types and base curves. With a contrast enhancement agent, tear menisci on the contact lenses around the upper and lower eyelids were highlighted. With hard contact lenses, the tear film was visualized clearly and changed after a blink when the lens was pulled up by the lid. Ultra-high resolution OCT is a potentially promising technique for imaging tears around contact lenses. This successful demonstration of in situ post-lens tear film imaging suggests that OCT could open a new era in studying tear dynamics during contact lens wear. The novel method may lead to new ways of evaluating contact lens fitting.

Proteins Identified From Care Solution Extractions of Silicone Hydrogels

The purpose of this study was to investigate the quantity and identify the proteins extracted from two different types of silicone hydrogel contact lenses by several multipurpose care solutions after 1 day of wear. Ten subjects were recruited to wear galyfilcon A lenses (Acuvue Advance, Vistakon) followed by lotrafilcon B lenses (O2 Optix, CIBA Vision) each for four consecutive days. Each day, subjects inserted a new pair of lenses for 8 h of wear after which both lenses were removed using forceps (lenses were not rubbed or rinsed after removal). Lenses were pooled in one of four commercially available care solutions for a 24-h soak followed by precipitation, resuspension in water, and quantification by Bradford assay and identification by mass spectrometry. Protein recovery from care solutions was as follows (quantities are in microg/lens): AQuify (galyfilcon A: 0.56, lotrafilcon B: 1.24), Complete MoisturePlus (galyfilcon A: 1.44, lotrafilcon B: 1.47), Opti-Free Express (galyfilcon A: 2.31, lotrafilcon B: 5.67), and ReNu MoistureLoc (galyfilcon A: 1.17, lotrafilcon B: 4.38). For each care solution, greater quantities of protein were removed from lotrafilcon B (3.19 +/- 2.19 microg/lens) than from galyfilcon A (1.37 +/- 0.72 microg/lens). Lactoferrin, lysozyme, and lipocalin were the most commonly identified, whereas various keratin compounds and other unique proteins were also detected. Opti-Free Express was consistently associated with the more efficient removal of proteins from these silicone hydrogels. More total protein was removed from lotrafilcon B than from galyfilcon A (approximately 2 x more protein) for all four care solutions, and 12 total unique protein species were recovered from galyfilcon A, whereas only 10 were recovered from lotrafilcon B. The higher quantities of protein extracted from lotrafilcon B may be due to stronger protein binding with this material and/or to differences in solution efficacy.

Higher-Order Aberrations When Wearing Sphere and Toric Soft Contact Lenses

To determine the on-eye effect of spherical and toric contact lens design on higher-order aberrations (HOA). Thirty eyes (15 subjects) entered a masked, randomized, cross-over study. Each eye was fitted with the spherical and toric lens of the following brands in random order: Acuvue Advance, Biomedics 55, Frequency 55, and SofLens 66. HOAs were measured using the Zywave II Aberrometer over a 6-mm aperture up to fifth order. A linear model accounting for the fixed effect of lens type and random effects of subject and eye was created. Paired t-tests were completed between lens brands within the spherical and toric lenses and between the spherical and toric lens within each brand. Best-corrected visual acuity (VA) was measured and compared. No clinically meaningful differences in total HOAs were found between brands or between the spherical and toric lens within a brand. Positive spherical aberration (SA) was reduced by all spherical and toric lenses compared to wearing no lens by 0.07 to 0.23 microm (p < 0.0001). Frequency toric induced the greatest change in SA. The thin-zone design lens (Acuvue Advance for Astigmatism) had a statistically different amount of vertical coma (-0.04 microm) than the three prism-balast toric lenses (0.11 to 0.23 microm; p < 0.0001). SofLens toric had the greatest amount of vertical coma, but better VA than Acuvue Advance for Astigmatism and Frequency toric. With the exception of Acuvue Advance for Astigmatism, toric lenses had greater absolute magnitude of vertical coma than their sphere counterparts (all p < 0.002). No other significant HOA differences were observed. Toric contact lenses with prism-ballast designs demonstrated more vertical coma, but better VA. Positive SA was reduced by spherical and toric contact lenses. The visual quality effect of lens design and material on induced HOAs warrants further investigation.

Short-Term Corneal Endothelial Response to Wear of Silicone-Hydrogel Contact Lenses in East Asian Eyes

To evaluate corneal endothelial bleb response to wear of silicone-hydrogel contact lenses in eyes of East Asian subjects. A total of 24 subjects of East Asian origin, attended 3 separate sessions for a prospective, single-centre, trial. The following contact lenses were used: ACUVUE ADVANCE with HYDRACLEAR (ADVANCE, -3 dioptres), ACUVUE OASYS with HYDRACLEAR Plus (OASYS, -3 dioptres), Focus NIGHT & DAY (NIGHT & DAY, -3 dioptres) and SofLens 38 (+3 dioptres). A modified Balaam's crossover design was used to randomize presentation of sessions and contact lenses within sessions. Session 1 was a comparison between OASYS and SofLens 38 under closed eye conditions, session 2 was a comparison between ADVANCE and NIGHT & DAY under open eye conditions, and session 3 was a comparison between OASYS and NIGHT & DAY worn under closed eye conditions. Corneal endothelial images were captured with the Topcon SP-3000P noncontact Specular Microscope before lens wear, after 20 mins of wear with lenses on and 5 and 10 mins later after lens removal. Blebs were manually identified on these digital images by a masked observer. The area of blebs and total area under consideration were derived using ImageNet software and used to calculate percentage area of blebs. A boundary of equivalence of 1% was used as a clinically significant bleb area difference, and two-sided 95% confidence intervals were utilized to evaluate differences between lenses within each session. In session 1, SofLens 38 produced a mean percentage area of blebs of 8.0% under closed eye conditions, which was significantly different to that produced by OASYS (1.6%). In session 2, both Advance and Night & Day produced a mean percentage bleb area of 0.4% under open eye conditions. In session 3, OASYS and NIGHT & DAY produced statistically similar mean percentage bleb areas of 1.7% and 2.0%, respectively. The similarity of bleb responses induced by the silicone-hydrogel lenses under the tested wearing conditions is consistent with the proposition that increases in Dk/t above a certain level will produce minimal change in corneal physiologic conditions compared with that when no lens is worn.

Comparative Study of Two Silicone Hydrogel Contact Lenses Used as Bandage Contact Lenses after LASEK

To evaluate two silicone hydrogel contact lens materials as continuous-wear bandage contact lenses after laser-assisted subepithelial keratomileusis (LASEK). The inclusion criteria were myopia of -6.00 diopters (D) or less, astigmatism lower than -1.5 D, bilateral best-corrected visual acuity of 20/20 or better, and candidates for bilateral LASEK. The patients were randomized to be fitted with a Balafilcon A (PureVision) lens in one eye and Galyfilcon A (Acuvue Advance) in the fellow eye. Uncorrected visual acuity, corneal epithelial status, conjunctival and limbal hyperemia, lens movement, contact lens debris, and the responses to a subjective-comfort questionnaire were assessed postoperatively. The parameters were evaluated before and 1 and 5 days after the procedure. A paired Student's t-test and chi-square tests were used when appropriate. We analyzed 44 eyes of 22 consecutive patients who underwent LASEK to correct low-to-moderate myopia. The mean spherical equivalent was -3.25 +/- 2.36 D. There was no difference in conjunctival or limbal hyperemia, lens movement, uncorrected visual acuity, or epithelial healing between the two lenses at any visit. A significant difference was found in lens deposition and discomfort, which were greater with the PureVision lens 5 days postoperatively (p = 0.01 for both comparisons). PureVision and Acuvue Advance contact lenses seem to be useful as continuous wear bandage contact lenses. There is no major clinical difference between the lenses, although patients report greater comfort with Acuvue Advance.

Pseudomonas Keratitis Associated With Daily Wear of Silicone Hydrogel Contact Lenses

To report two cases of pseudomonas keratitis associated with daily wear of silicone hydrogel contact lenses. Medical records of two patients who developed pseudomonas keratitis while wearing silicone hydrogel lenses on a daily-wear schedule are reviewed and discussed. A 13-year-old girl who wore ACUVUE Advance lenses (Johnson & Johnson Vision Care, Jacksonville, FL) 12 to 14 hours daily developed a paracentral corneal ulcer in her left eye 4 months after beginning contact lens use. Cultures were positive for Pseudomonas aeruginosa. The ulcer responded to fortified antibiotics and resolved in 10 days. Best-corrected visual acuity after resolution of the ulcer was 20/25. A 58-year-old woman with a 30-year history of rigid gas-permeable contact lens wear was refitted with O2 Optix lenses (CIBA Vision, Duluth, GA). Six months later, she had a 4.9 x 4.0 mm epithelial defect with an underlying stromal infiltrate in the right eye. Cultures were positive for P. aeruginosa. The ulcer responded to fortified antibiotics and resolved in 30 days. Best-corrected visual acuity after resolution of the ulcer was 20/30. Increased oxygen permeability associated with silicone hydrogel contact lenses may reduce, but does not eliminate, the risk of pseudomonas keratitis. Studies have yet to quantify the risk of keratitis associated with daily wear of these lens materials. Further study is necessary to identify the risks of complications with daily wear of silicone hydrogel lenses and to determine which factors may contribute to those risks.

Conformational and Quantitative Characterization of Lysozyme Extracted from Galyfilcon and Senofilcon Silicone Hydrogel Contact Lenses

Purpose: To compare two solvents for retrieval of lysozyme deposited on a silicone hydrogel (SH) contact lens material galyfilcon A (GA; Acuvue Advance). Methods: Two buffers used were 50:50 acetonitrile/0.02% trifluoroacetic acid (buffer 1) and 50:50 acetonitrile/50 mM NaOH (buffer 2). Results: Extraction efficiency from GA lenses was 74% (buffer 1) and 83% (buffer 2). Buffer 2 decreased lysozyme activity > buffer 1. Ex vivo GA lenses showed total protein deposition of 2–16 μ g/lens with total lysozyme deposition of 0.3–3.9 μg/lens. Conclusions: We have developed a low acid strength extraction buffer that can be used to efficiently extract active lysozyme protein from novel siloxane-based contact lens materials.

Rotational Stability of Toric Soft Contact Lenses During Natural Viewing Conditions

To compare objectively the rotational stability of two differently designed toric soft contact lenses over a range of natural viewing conditions using a novel infrared, video-based technique. Two contact lenses using different methods of stabilization were assessed: Accelerated Stabilization Design (ACUVUE ADVANCE for ASTIGMATISM) and Lo-Torque Design (B&L SofLens Toric). Four tasks involving saccades were performed: settling time with free viewing, reading, visual search, and execution of large versional tasks. Lens position (degrees of rotation) was continuously recorded with a head mounted, infrared, video-based system and a digital photo slit-lamp in 20 adult subjects. All measurements were obtained from the left eye under binocular viewing conditions with contact lenses on both eyes. The ACUVUE lens was significantly more stable during the settling time and large saccadic versional tasks than the SofLens. For the two other tasks (reading, visual search), performance was similar. The ACUVUE design was superior in stability for two of the four conditions tested. This resulted in a more stable lens immediately after insertion as well as during some visual tasks involving either naturally occurring or programmed large versional eye movements. Both lens designs provided acceptable performance in terms of induced astigmatism produced by off-axis rotation.

Visual Acuity with Spherical and Toric Soft Contact Lenses in Low- to Moderate-Astigmatic Eyes

To evaluate the visual acuity of myopic, astigmatic eyes, with spherical and toric soft contact lenses. A randomized, masked, cross-over study was conducted to compare acuity with soft spherical and toric contact lenses on patients with between -0.75 and -2.00 D of refractive astigmatism. A total of 15 patients (30 eyes) were fitted with four brands of spherical and toric lenses (Acuvue Advance, Biomedics 55, Frequency 55, and SofLens 66), in random order. An initial visit was conducted to fit the lenses and an over-refraction (OR) was performed to determine the best prescription. At the measurement visit, patients' pupils were dilated with 1.0% tropicamide and 2.5% phenylephrine to allow wavefront aberration measurements, and a final OR was performed. A 6-mm aperture was held in front of the eye to measure visual acuity through just the contact lens and the contact lens with the final OR. Acuity was measured monocularly, under photopic and mesopic conditions with high- and low-contrast logMAR charts at distance. Differences in acuity were analyzed using repeated measures analysis of variance. Visual acuity with soft spherical contact lenses was not significantly different between lens brands. For toric contact lenses, acuity was significantly better with Biomedics 55 and SofLens 66 than with Acuvue Advance; and acuity with SofLens 66 was significantly better than with Frequency 55. Low-astigmatic eyes gained between 3 and 5.5 letters of acuity with toric contact lenses vs. spherical lenses; and moderate-astigmatic eyes gained between 8 and 12.5 letters. Both low- and moderate-astigmatic eyes showed improvements in acuity with toric contact lenses. Lens brand had a measurable effect on acuity for toric contact lenses. Further investigation of aberrations induced by contact lens design is warranted to explain the observed differences in visual performance.