Polymacon Lenses Research Articles

Association Between Ocular Surface Temperature and Tear Film Stability in Soft Contact Lens Wearers.

To investigate the correlation between the changes in the ocular surface temperature (OST) and tear film stability over soft contact lenses (SCLs). We enrolled 20 eyes of 20 normal SCL wearers (20 men; 24.4 ± 4.1 years). We used four different daily disposable SCLs: one silicone hydrogel lens (delefilcon A) and three hydrogel lenses (etafilcon A with polyvinylpyrrolidone [PVP], etafilcon A, and polymacon). OST was measured every second during 10 seconds without blinking. We defined the difference in the OST from 0 to 10 seconds as ΔOST. To evaluate tear film stability, we measured noninvasive tear break-up time (NIBUT) and tear interference patterns on the contact lenses (TIPCL) using tear film interferometry. The parameters were measured before and 15 minutes after wearing each SCL. ΔOST was correlated significantly with NIBUT without (r = 0.411, P < 0.01) and with SCL (r = 0.642, P < 0.01). TIPCL grade was correlated significantly with ΔOST over SCLs (r = -0.636, P < 0.01). ΔOST was significantly smaller with silicone hydrogel delefilcon A than hydrogel etafilcon A and polymacon lenses (P < 0.05 and P < 0.01, respectively). Delefilcon A and etafilcon A with PVP lenses had significantly smaller NIBUT than etafilcon A (P < 0.05 for both comparisons). TIPCL grade of delefilcon A lens was significantly smaller than those of etafilcon A and polymacon (P < 0.01 for both comparisons). The changes in OST over SCLs are related to tear film stability. Measurements of OST can be used to evaluate tear film stability for SCL wearers.

Experimental studies on soft contact lenses for controlled ocular delivery of pirfinedone: in vitro and in vivo

Context: Pirfinedone (PFD) is a novel agent which has the potential to prevent scarring in the eyes. The 0.5% PFD eye drops exhibits poor bioavailability. Whereas, the feasibility of using contact lens as ocular drug delivery device initiated novel possibilities.Objective: To evaluate the delivery of PFD by soft contact lens (SCL) in vivo, we screened the most suitable lens material for PFD among various commercially available SCL materials in vitro.Material and methods: Firstly, 11 different SCLs (−1.00 diopter) were respectively soaked in 2 ml of 0.05% PFD-loading solution for 24 h to fully absorb drug, and then placed in fresh phosphate buffered saline (PBS) to release the drug. PFD concentration in PBS was determined by ultraviolet absorbance at 310 nm. Secondly, by immersing in 2 ml of 0.5% PFD eye drops for 24 h, the polymacon lens (0.00 diopter) was then placed on the cornea of New Zealand rabbits. PFD concentrations were detected by high performance liquid chromatography (HPLC) in tears, aqueous humor, conjunctiva, cornea, and sclera at different time points.Results: PFD showed some affinity for pHEMA-based lenses and the polymacon lens more slowly released more amount of PFD than any other lens in vitro (p < 0.001). Compared with eye drops, drug-loaded SCLs greatly enhanced the retention time and concentrations of PFD in cornea and aqueous humor and consequently improved the bioavailability of PFD.Conclusion: Polymacon-based SCL is probably a promising vehicle to be an effective ophthalmic delivery system for PFD.

Impact of Contact Lens Materials on Multipurpose Contact Lens Solution Disinfection Activity Against Fusarium solani

To investigate the effects of eight different soft contact lenses on disinfection efficacy of a multipurpose solution (MPS) containing polyhexamethylene biguanide (PHMB) against Fusarium solani. Six silicone hydrogel lenses (galyfilcon A, senofilcon A, comfilcon A, enfilcon A, balafilcon A, and lotrifilcon B) and two conventional hydrogel lenses (polymacon and etafilcon A) were placed in polypropylene lens cases filled with MPS containing 0.0001% PHMB and soaked for 6, 12, 24, 72, and 168 hours. After each interval, depleted MPS from lens cases were removed and assayed for activity against F. solani according to International Organization for Standardization (ISO) 14729 stand-alone procedure. A portion was aliquoted for chemical analysis. Soaking etafilcon A, balafilcon A, and polymacon lenses for 6 hours reduced the concentration of PHMB in MPS by more than half the stated labeled concentration, with concentrations below the limit of detection for etafilcon A-depleted and balafilcon A-depleted solutions after 12 and 72 hours of soaking, respectively. Except for comfilcon A-depleted solutions, all others failed to consistently obtain one log reduction of F. solani. The solutions soaked with etafilcon A, balafilcon A, and polymacon lenses for 24 hours or more lost all or almost all fungicidal activity against F. solani. Over time, the disinfectant uptake by some lenses can significantly reduce the PHMB concentration and the fungicidal activity of the MPS against F. solani. Current ISO methodology does not address the reduction in microbiocidal efficacy when lenses are soaked in MPS. The ISO committee should consider adding "soaking experiments" to quantify the effect that contact lens materials have on the performance of MPSs.

Kinetics of Lysozyme Activity Recovered from Conventional and Silicone Hydrogel Contact Lens Materials

We determined the activity of lysozyme recovered from various conventional and silicone hydrogel (SH) contact lens materials as a function of time, using an in vitro model. Polymacon, omafilcon, etafilcon, vifilcon, lotrafilcon A, lotrafilcon B, balafilcon A, galyfilcon A and senofilcon A contact lenses (n = 5) were incubated in lysozyme solution for time periods ranging from 1 h to 28 days. Following the specified incubation period, the lysozyme deposited on the lenses was extracted and the sample extracts were assessed for lysozyme activity and total lysozyme. We found no significant difference (NSD) between omafilcon and polymacon lens materials for the initial 3 days (P > 0.05); however, there was a significant difference between the two lenses from 5 to 28 days (P < 0.05). There was NSD (P > 0.05) between etafilcon and vifilcon lens materials at all time-points and significant differences were seen between various SH lens materials at different time points. After 28 days, lysozyme deposited on etafilcon (90 ± 3%) and vifilcon (91.4 ± 3%) exhibited the greatest activity. Lysozyme deposited on polymacon (17.8 ± 4%), lotrafilcon A (23.4 ± 4%) and lotrafilcon B (24 ± 5%) exhibited the lowest activity. Lysozyme deposited on omafilcon, galyfilcon, senofilcon and balafilcon exhibited 38 ± 3%, 62.3 ± 8%, 47 ± 6% and 61 ± 7% of activity, respectively. The reduction in activity of lysozyme deposited on contact lens materials is time-dependent and the rate of reduction varies between lens materials. This variation in activity recovered from lenses could be due to the differences in surface/bulk material properties or the location of lysozyme on these lenses.

Imaging Protein Deposits on Contact Lens Materials

The majority of studies investigating protein deposition on contact lens materials require that the deposit of interest be removed, potentially resulting in erroneous results if some proteins are not removed adequately. The purpose of this study was to investigate the use of in situ imaging methods to examine protein deposition on conventional poly(2-hydroxyethyl methacrylate) (polyHEMA)-based and silicone hydrogel contact lens materials. Six silicone hydrogel and five polyHEMA-based hydrogel contact lens materials were examined by Atomic Force Microscopy (AFM) and/or Scanning Electron Microscopy (SEM) techniques, after being deposited with proteins in an in vitro model. AFM studies examined lenses deposited solely with lysozyme at approximate physiological concentrations and SEM studies were conducted on lenses exposed to a dilute mixture of lysozyme and albumin-conjugated gold spheres. AFM studies demonstrated that the lens materials had markedly differing surface topographies. SEM results showed that galyfilcon A and balafilcon A lenses deposited both lysozyme and albumin in relatively large aggregates, as compared with lotrafilcon A and B, in which the proteins were deposited in a more evenly spread, monolayer formation. Polymacon lenses deposited more protein than any of the silicone hydrogel materials and much of the protein was aggregated together. AFM data indicated that balafilcon A, lotrafilcon A and polymacon deposited lysozyme in a similar manner, with very little lysozyme being deposited in discrete areas. Galyfilcon A behaved very differently, with the lysozyme exhibiting both aggregates as well as string-like formations over the lens surface. Imaging techniques that allow proteins to be examined in situ show much promise for determining the extent and physical characterization of protein on contact lens materials. These techniques indicate that the pattern of deposition of proteins onto silicone hydrogel contact lens materials differs between materials, depending upon their bulk and surface composition.

Phospholipids and Their Degrading Enzyme in the Tears of Soft Contact Lens Wearers

Low tear phospholipids levels are associated with tear film instability in soft contact lens wearers. We assayed levels of phospholipids and their degrading enzyme secretory phospholipase A2 (sPLA2) both in tears and deposited on contact lenses composed of 2 hydrophilic materials after 1 day of routine use. Polymacon (Medalist; FDA group 1, low water/nonionic) and Etafilcon A (One Day Acuvue; group 4, high water/ionic) contact lenses were worn for 12 hours by 16 experienced contact lens wearers. Phospholipids in tear fluids and deposited on contact lenses were estimated by phosphorus determination with ammonium molybdate through enzymatic digestion. Double-antibody sandwich ELISA was used to determine group IIa sPLA2 concentrations, and sPLA2 activity was assayed using 1,2-diheptanoyl thio-phosphatidylcholine as substrate. Phospholipids concentrations in tears with Polymacon and Etafilcon A were 186 +/- 39 and 162 +/- 33 microg/mL, respectively. The latter concentration was significantly lower than that observed in the same subjects when not wearing contact lenses (P = 0.0023). In tears, both group IIa sPLA2 concentrations and enzymatic activity remained unchanged, regardless of lens wearing. However, Etafilcon A (0.57 +/- 0.09 microg/lens) showed more group IIa sPLA2 deposition than Polymacon (0.01 +/- 0.01 microg/lens; P < 0.001). Furthermore, group IIa sPLA2 deposited on Etafilcon A but not on Polymacon lenses retained its enzymatic activity. Significant differences of group IIa sPLA2 deposition were found in the 2 lenses tested. Such deposition might induce phospholipid hydrolysis in tears and thereby promote tear film instability in hydrophilic contact lens wearers.

Post-lens tear-film depletion due to evaporative dehydration of a soft contact lens

For a soft-contact-lens (SCL) wearer, corneal health and comfort are strongly influenced by water transport through the polymeric materials used in lens fabrication. In particular, evaporative water loss at the anterior lens surface is a potential cause of contact-lens dehydration and of post-lens tear-film depletion, which in turn, may lead to discomfort, dryness syndrome, and/or lens adhesion. We present a solution–diffusion model for transport of water through soft-contact-lens materials to mimic evaporative dehydration from a contact lens during blinking and to access possible SCL adhesion to the corneal surface under a variety of environmental conditions (e.g., wind speed and relative humidity). To describe the water-transport process, we use an extended version of the Maxwell–Stefan multicomponent diffusion equation for species that differ starkly in size (i.e., water and the polymer matrix). To describe thermodynamic properties of the soft-contact-lens/water mixture, we use a modified Flory–Rehner theory for polymer solutions. The proposed transport model is applied to two typical SCL materials: a low-water-content (38 wt.%) polymacon SCL (SofLens ® 38), and a high-water-content (70 wt.%) hilafilcon A SCL (SofLens™ One Day). We calculate that a SCL on the eye loses water within a few minutes from lens insertion until it reaches a periodic steady state, with an average water content a few percent lower than the initial saturated water content. When the external relative humidity is low and the wind speed is high, the periodic-steady net flux of water from the post-lens tear film (PoLTF) through the contact lens toward the environment is comparable to the supply of water to the PoLTF from the eye anterior chamber. Thus, PoLTF depletion may occur at these conditions, leading to undesired, reduced SCL on-eye movement or, perhaps, to SCL adhesion on the ocular surface. Also, our calculations show that, at the most dehydrating conditions, the high-water-content hilafilcon A lens is more prone to dehydration and PoLTF depletion than is the low-water-content polymacon lens with the same thickness. However, at the least dehydrating conditions this trend is reversed. Relative humidity, wind speed, and lens thickness significantly influence SCL dehydration.

Is the superior cornea continuously swollen?

Background: During waking hours, the upper eyelid typically covers the superior two millimetres of the cornea. This partial oxygen barrier is the presumed cause of the reversibly elevated epithelial oxygen uptake in tiiis region of the cornea. We studied the thickness profile of the vertical corneal meridian before and after extended exposure to a uniform hypoxic stimulus to ascertain die extent of chronic superior corneal swelling diat might be attributable to coverage by die upper lid. Methods: Each of 16 male subjects, age 24 to 40 years, wore a uniformly thick polymacon lens (Dk/L = 5.7 times 10‐9 cm ml 02/s ml mmHg) on one eye for four hours with die eyelid patched. Thickness was measured at five sites across the vertical corneal meridian prior to and immediately after patching. Baseline thickness and swelling were compared at die superior and inferior edges of selected central chord diameters. Results: At baseline, die superior cornea was, on average, 31 μm thicker (p = 0.0002) at the 7.1 mm chord and 9 μm thicker (not significant) at die 3.75 mm chord, compared to die inferior cornea at die corresponding chords. Mean corneal swelling ranged from 70.5 μm centrally to approximately 48 μm at die 7.1 mm chord diameter. The extent of swelling at die corresponding superior and inferior sites was virtually identical for both chord diameters. Conclusion: Although die superior cornea is significantly thicker than die inferior cornea, diis difference does not appear to be immediately related to die chronic differences in open eye oxygen tension between the superior and inferior regions.

Modulation of bacterial adhesion to hydrogel contact lenses by albumin.

The purpose of this investigation was to measure the abilities of Pseudomonas aeruginosa and Staphylococcus epidermidis strains to adhere to two hydrogel lens materials and measure the effect of a protein-coated surface on the number of adhered bacteria. Proteins absorbed to contact lenses during sleep were extracted, subjected to sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE), and probed for the presence of albumin. Bacterial adhesion was measured by counting bacteria adherent to contact lenses coated in vitro in increasing concentrations of albumin, examining the ability of albumin in solution to prevent adhesion to albumin-coated lenses, and examining the topography of bacterial adhesion by electron microscopy. Albumin adsorbed to lenses during overnight wear. In vitro studies demonstrated that Polymacon lenses adsorbed more albumin than Etafilcon A lenses. In general, the numbers of adherent bacteria increased with increasing concentration of albumin. Bacteria adhered in higher numbers to Polymacon lenses than Etafilcon A (p < 0.05). P. aeruginosa showed an increased adhesion as the amount of albumin on Etafilcon A lenses increased. There was a decrease in numbers of bacteria adhering per milligram of albumin as the level of albumin increased on Polymacon lenses. Cells tended to adhere to "deposits" on albumin-coated lenses. Albumin adsorbed onto the surface of contact lenses modulated the ability of P. aeruginosa and S. epidermidis to adhere. P. aeruginosa is commonly associated with contact lens-associated microbial keratitis, where bacterial adhesion to contact lenses is believed to be an important first step in the pathogenesis of the disease.

The effects of disposable daily-wear contact lenses on goblet cell count: Conner CG, Campbell JB, Steel SA: CLAO J 1997;23:37–39

The number of goblet cells on the inferior bulbar conjunctiva increases in response to daily wear contact lens use. We conducted a study to examine whether daily wear soft contact lenses worn on a 2-week disposable schedule would also induce the same goblet cell response.Twenty-eight subjects who had never worn contact lenses were fit with 38% water polymacon lenses. The lenses were worn on a daily wear basis and replaced every two weeks over a 6-month period. Goblet cell count was determined by impression cytology of the inferior bulbar conjunctiva.No significant increase in goblet cell count was observed in the subjects during the 6 months period; the 3.23% baseline goblet cell count was never exceeded. In our previous study, after 6 months of conventional daily wear lens use, the goblet cell count increased from a baseline of 4.19% to 8.0%.It appears that wearing daily wear soft contact lenses on a disposable basis may be less irritating to the ocular surface than wearing soft contact lenses on a conventional daily wear basis.

A comparison of 141 polymacon (Iogel) and 140 poly(methyl methacrylate) intraocular lens implants.

In a prospective controlled trial 290 consecutive patients were randomly allocated a polymacon or a poly(methyl methacrylate) (PMMA) intraocular lens. Early Treatment of Diabetic Retinopathy Study (ETDRS) acuity charts gave similar results with both lenses. However Pelli-Robson contrast sensitivity charts gave a better result with PMMA lenses. Polymacon lenses appeared to remain free of any adhesions after implantation raising the question of long term stability. Four patients experienced problems related to this, three involved total lens dislocation. Seven patients developed early 'fibrin' membranes coating the polymacon lens, of which three were florid.

Pseudomonas Attachment to New Hydrogel Contact Lenses

The adhesion of two strains of Pseudomonas aeruginosa to unworn hydrogel contact lenses (CLs) was studied by scanning electron microscopy. New daily-wear polymacon lenses (38.6% water content) and extended-wear lidofilcon A lenses (70% water content) were exposed to a suspension of 10(8) colony-forming units per milliliter of P aeruginosa for 2, 5, 15, 30, and 60 minutes. Increasing numbers of bacteria were found to attach to the lenses with time, and no significant differences between CL types were demonstrated. Attachment was considered to be irreversible since washing did not remove the bacteria. We conclude that P aeruginosa can actively attach to new, unworn hydrogel CLs.

Evidence for Lack of Antigenicity of Polymacon Contact Lens Material in Guinea Pigs

In an experiment designed to test one parameter of the antigenic potential of the hydrogel soft contact lens material polymacon (delayed hypersensitivity as shown by skin test), we divided 20 guinea pigs into four groups of 5. 5 guinea pigs were immunized with ground polymacon in complete Freund’s adjuvant. These animals and 5 uninjected control animals were skin-tested with the same lens material. As a positive control, another 5 animals were immunized with bovine serum albumin in complete Freund’s adjuvant. These animals and 5 uninjected control animals were skin-tested with bovine serum albumin. Only the animals immunized and skin-tested with bovine serum albumin had positive skin-test results for delayed hypersensitivity. The lens material was tolerated without inflammation in immunized and nonimmunized skin-tested animals. There was no histologic evidence for antigenicity of polymacon in guinea pig tissues. We conclude that polymacon is unlikely to act as an antigen for delayed hypersensitivity in the guinea pig. We suggest that conjunctivitis associated with the wearing of polymacon lenses is not caused by antigenicity of the lens itself, but by that of some material adhering to the lens.