Short term wear of high Dk soft contact lenses does not alter corneal epithelial cell size or viability

Quantitative assessment of central and limbal epithelium after long-term wear of soft contact lenses and in patients with dry eyes: a pilot study

PurposeAnalysis of microstructural alterations of corneal and limbal epithelial cells in healthy human corneas and in other ocular conditions.Patients and methodsUnilateral eyes of three groups of subjects include healthy volunteers (G1, n=5), contact lens wearers (G2, n=5), and patients with dry eyes (G3, n=5) were studied. Imaging of basal (BC) and intermediate (IC) epithelial cells from central cornea (CC), corneal limbus (CL) and scleral limbus (SL) was obtained by in vivo confocal microscopy (IVCM). An appropriate image analysis algorithm was used to quantify morphometric parameters including mean cell area, compactness, solidity, major and minor diameter, and maximum boundary distance.ResultsThe morphometric parameters of BC and IC demonstrated no significant differences (P>0.05) between groups. Comparison between three corneal locations (CC, CL, and SL) within the groups showed significant differences (P<0.05) with mean values of cell area, compactness, solidity, and major and minor diameter of BC that increase from CC to limbus. The BC were round and regular in the central cornea (P<0.05) compared with CL and SL.ConclusionsIVCM enables high-quality confocal images from central corneal and limbal epithelium. This quantitative study demonstrated morphological differences in the basal and intermediate epithelium between limbus and central cornea, and found no differences between contact lens wearers, dry eyes, and normal subjects.

Microbiological study of therapeutic soft contact lenses used in the treatment of recurrent corneal erosion syndrome

OBJECTIVE

To determine the bacteriological spectrum of the removed therapeutic soft contact lenses (TSCLs) and to establish efficacy of prophylactic antibiotics on TSCLs used for 2 weeks for treatment of patients with recurrent corneal erosion syndrome (RCES).

METHODS

This study included idiopathic RCES treated using highly oxygen-permeable silicone hydrogel contact lenses (CLs), and treated 4 times per day with topical tobramycin 3% for 2 weeks. After TSCLs were applied for 2 weeks, the lenses were removed with sterile forceps under which a speculum was inserted, and placed on blood agar with the inner face down. The TSCLs were analyzed for bacterial colonization, and antibiotic susceptibility tests were performed for the isolates, using disk diffusion.

RESULTS

Of the 40 lenses analyzed, 9 (22.5%) yielded positive cultures. Staphylococcus epidermidis was the most commonly isolated microorganism; there were five methicillin-sensitive coagulase-negative staphylococci and two methicillin-resistant coagulase-negative staphylococci. Furthermore, we found two lenses that were colonized by Enterobacter gergoviae and Citrobacter freundii. All cultured bacteria showed intermediate or complete sensitivity to ciprofloxacin, tigecycline, and tobramycin. Despite bacterial colonization in 9 CLs, no clinical signs of infectious keratitis were found in any of the patients with prophylactic topical tobramycin 3%.

CONCLUSIONS

In case of using TSCLs for 2 weeks, tobramycin or ciprofloxacin may be useful as prophylactic topical antibiotics for preventing secondary corneal infections. Considering currently growing incidence of ciprofloxacin-resistant ocular isolates, tobramycin seems to be a reasonable prophylactic topical antibiotic susceptible broad spectrum of bacteria in clinics.

Alginate-polyester comacromer based hydrogels as physiochemically and biologically favorable entities for cardiac tissue engineering

The physiochemical and biological responses of tissue engineering hydrogels are crucial in determining their desired performance. A hybrid comacromer was synthesized by copolymerizing alginate and poly(mannitol fumarate-co-sebacate) (pFMSA). Three bimodal hydrogels pFMSA-AA, pFMSA-MA and pFMSA-NMBA were synthesized by crosslinking with Ca(2+) and vinyl monomers acrylic acid (AA), methacrylic acid (MA) and N,N'-methylene bisacrylamide (NMBA), respectively. Though all the hydrogels were cytocompatible and exhibited a normal cell cycle profile, pFMSA-AA exhibited superior physiochemical properties viz non-freezable water content (58.34%) and water absorption per unit mass (0.97 g water/g gel) and pore length (19.92±3.91 μm) in comparing with other two hydrogels. The increased non-freezable water content and water absorption of pFMSA-AA hydrogels greatly influenced its biological performance, which was evident from long-term viability assay and cell cycle proliferation. The physiochemical and biological favorability of pFMSA-AA hydrogels signifies its suitability for cardiac tissue engineering.

In vivo confocal microscopy: corneal changes of hydrogel contact lens wearers

To evaluate the corneal findings in hydrogel contact lens wearers by in vivo confocal scanning microscopy. One hundred and forty-two eyes of 71 myopic contact lens wearers (group 1) and 142 eyes of 71 non-contact lens wearers (group 2), whose age, gender and refractive error matched, were enrolled in order to detect the corneal changes by in vivo confocal microscopy through the central cornea. The average age was 25.5 ± 5.7 (16-52) and 25.6 ± 5.6 (17-49) in groups 1 and 2, respectively. The mean duration of contact lens wear was 43.9 ± 15.3 (6-240) months. Anterior keratocyte density was 667.5 ± 128.3 cells/mm(2) in group 1 and 821.4 ± 136.7 cells/mm(2) in group 2 (P = 0.001). Posterior keratocyte densities of groups 1 and 2 were 540.2 ± 87.6 cells/mm(2) and 628.2 ± 72.4 cells/mm(2), respectively (P < 0.001). Endothelial cellular density was 2611.2 ± 298.4 cells/mm(2) in group 1 and 2643 ± 218.2 cells/mm(2) in group 2 (P = 0.52). Ratio of polymegethism was 44.6 ± 8.8% in group 1 and 31.3 ± 4.7% in group 2 (P < 0.001). Epithelial cellular enlargement was observed in eyes wearing contact lenses with a mean Dk/t ratio of 26.5 × 10(-9) ± 5.9 (8.9-32 × 10(-9)). Stromal microdots occurred with contact lenses with a mean Dk/t ratio of 13.2 × 10(-9) ± 17.5 × 10(-9) (8.9-20 × 10(-9)). In vivo examination of the cornea with confocal microscopy revealed a number of changes. These changes can be attributed both to the mechanical and the hypoxic effects of soft contact lenses. In soft contact lenses with a high Dk/t ratio, these changes would be less frequent.

Tear film, contact lens, and patient factors associated with corneal staining

PURPOSE

The purpose of this study was to examine ocular surface and tear film, contact lens, care solution, medical, and patient-related factors that are associated with corneal staining in contact lens wearers.

METHODS

In this cross-sectional/nested case-control study, in addition to the assessment of corneal staining with fluorescein, a variety of tear film and ocular surface, contact lens, and patient-related factors were examined. Poisson regression models were used to examine the relation between corneal staining and these factors.

RESULTS

Data from 413 patients were eligible for the analyses described. The average age was 30.6 ± 11.1 years, and 277 (67.1%) of the patients were women. Several factors were shown to be related to increased corneal staining in multivariate modeling, including increased daily wearing times (P = 0.0006), lower income (P = 0.0008), lissamine green conjunctival staining (P = 0.002), contact lens deposition (P = 0.007), increased tear meniscus height (P = 0.007), and decreased hydrogel nominal water content (P = 0.02). The wearing of silicone hydrogels (as opposed to hydrogels) was protective against corneal staining (P = 0.0004). Notably, neither contact lens care solutions nor disinfectants were associated with corneal staining.

CONCLUSIONS

Corneal staining in contact lens wearers continues to be a frequent, but not well understood, outcome. These data suggest that contact lens factors (water content, material, wearing time, and deposition) are more generally associated with corneal staining than are contact lens care solutions or other ocular surface and tear film, demographic, or medical factors.

The effects of short-term lens wear and eye rubbing on the corneal epithelium

OBJECTIVES

To measure the effects of short-term high oxygen-transmissible (Dk) soft and rigid contact lens wear and eye rubbing on basal epithelial appearance and epithelial thickness.

METHODS

Ten subjects were enrolled in a randomized crossover study. The subjects' left eye was used as a control, and the right eye either wore a high Dk soft lens, high Dk parallel fitted rigid gas-permeable lens, or was rubbed on 3 separate days. Epithelial basal cell regularity and central and peripheral epithelial thickness were assessed before and after 6-hr soft or rigid lens wear or 10-min rubbing using in vivo confocal microscopy and modified optical pachometry.

RESULTS

Basal cell regularity was unaffected by short-term lens wear or eye rubbing (Friedman Test, P=0.11 and 0.37 in test and control eyes, respectively). The peripheral epithelium was thicker than the central epithelium (repeated-measures analysis of variance, P=0.03) but remained unaffected by short-term lens wear or eye rubbing (repeated-measures analysis of variance, P>0.05, power <0.08).

CONCLUSIONS

Corneal epithelial thickness and basal cell morphology were not affected by short-term lens wear or eye rubbing in this pilot study.

The effect of long-term wear of soft lenses of low and high oxygen transmissibility on the corneal epithelium

PURPOSE

To measure the effects of long-term wear of soft lenses of low and high oxygen transmissibility (Dk) on basal epithelial appearance and epithelial thickness.

METHODS

Sixty-three subjects were enrolled in a cross-sectional study. Seventeen high Dk lens wearers and 24 low Dk lens wearers who had worn lenses on an extended wear basis for more than 3 years (range: 3-22) were compared to a group of 22 age-matched subjects who had never worn contact lenses. Cell regularity and the intensity of light backscattered by the basal epithelium were assessed using confocal microscopy. Epithelial thickness was measured at the centre and at four peripheral locations using modified optical pachometry.

RESULTS

Epithelial basal cells appeared less regular in low Dk lens wearers than high Dk wearers or controls (Mann-Whitney U-test, P=0.001). The intensity of backscattered light did not differ across groups (Kruskal-Wallis test, P=0.37). Low Dk wearers had the thinnest epithelium (46 (10) microm), followed by high Dk wearers (54 (14) microm) and controls (58 (9) microm; ANOVA, P<or=0.006). Topographical position did not affect epithelial thickness (ANOVA, P=0.10).

CONCLUSIONS

Visible alterations to the basal epithelial cells can only be detected in long-term extended wearers of low Dk soft lenses. Extended wear of high Dk soft lenses results in topographically uniform epithelial thinning that is significantly less than the thinning seen with low Dk lenses. Confirmation of these findings using groups with evenly matched duration of lens wear is required.

The epidemiology of contact lens related infiltrates

With estimated numbers of contact lens wearers worldwide exceeding 140 million, even complications with a low incidence will affect a significant number of individuals. Although contact lenses clearly have many advantages for wearers, certain risks have been associated with their use. Differences in risk for different types of contact lenses and wearing patterns have been demonstrated for both rare and common lens related complications. This review particularly focuses on the incidence and etiology of contact lens related corneal infection and inflammation. An understanding of the risks and contributory factors to these conditions is important for practitioners and will enable an informed choice of safer lens wear modalities, wear schedules, and hygiene regimes to be made.

Silicone Hydrogel Contact Lenses and the Ocular Surface

For 30 years, contact lens research focused on the need for highly oxygen-permeable (Dk) soft lens materials. High Dk silicone hydrogel contact lenses, made available in 1999, met this need. The purpose of this review is to examine how silicone hydrogel lens wear affects the ocular surfaces and to highlight areas in which further research is needed to improve biocompatibility. Silicone hydrogel lenses have eliminated lens-induced hypoxia for the majority of wearers and have a less pronounced effect on corneal homeostasis compared to other lens types; however, mechanical interaction with ocular tissue and the effects on tear film structure and physiology are similar to that found with soft lens wear in general. Although the ocular health benefits of silicone hydrogel lenses have increased the length of time lenses can be worn overnight, the risk of infection is similar to that found with other soft lens types, and overnight wear remains a higher risk factor for infection than daily wear, regardless of lens material. Future contact lens research will focus on gaining a better understanding of the way in which contact lenses interact with the corneal surface, upper eyelid, and the tear film, and the lens-related factors contributing to infection and inflammatory responses.

Characterization of powdered epidermal vaccine delivery with multiphoton microscopy

Multiphoton laser scanning microscopy (MPLSM) has been adapted to non-invasively characterize hand-held powdered epidermal vaccine delivery technology. A near infrared femtosecond pulsed laser, wavelength at approximately 920 nm, was used to evoke autofluorescence of endogenous fluorophores within ex vivo porcine and human skin. Consequently, sub cellular resolution three-dimensional images of stratum corneum and viable epidermal cells were acquired and utilized to observe the morphological deformation of these cells as a result of micro-particle penetration. Furthermore, the distributional pattern of micro-particles within the specific skin target volume was quantified by measuring the penetration depth as revealed by serial optical sections in the axial plane obtained with MPLSM. Additionally, endogenous fluorescence contrast images acquired at the supra-basal layer reveal cellular structures that may pertain to dendritic Langerhans cells of the epidermis. These results show that MPLSM has advantages over conventional histological approaches, since three-dimensional functional images with sub-cellular spatial resolution to depths beyond the epidermis can be acquired non-invasively. Accordingly, we propose that MPLSM is ideal for investigations of powdered epidermal vaccine delivery.

Changes in corneal structure with continuous wear of high-Dk soft contact lenses: a pilot study

PURPOSE

Despite numerous studies that have considered the effects of extended wear of high-Dk soft contact lenses on ocular physiology, little attention has been paid to the impact of such lenses on central or peripheral corneal thickness and curvature. The present study aims to report the time course of changes in corneal thickness and curvature that accompanies the 30-night continuous wear of new silicone hydrogel soft contact lenses in a neophyte population in a longitudinal study.

METHODS

Six subjects wore high-Dk lotrafilcon (Dk = 140) on a 30-night replacement schedule for 12 months. Only measurements from the right eye were considered for analysis. Topographical measurements of corneal thickness and curvature were taken. The same parameters were monitored for an additional period of 3 months after lens removal.

RESULTS

An almost homogenous increase in corneal radius of curvature was detected for all the locations studied, being statistically significant for the 4-mm cord diameter area. This effect was associated with a progressive thinning effect for the central cornea, whereas midperipheral and peripheral areas did not display such a thinning effect during continuous wear. These effects were still evident for the central cornea 3 months after contact lens wear discontinuation.

CONCLUSIONS

Continuous wear of high-Dk silicone hydrogel contact lenses is associated with clinically appreciable changes in topographical corneal curvature, whereas only a reduction in corneal thickness is appreciated in the central area. This effect seems to be a result of mechanical pressure induced by these hybrid hyperpermeable materials, characterized by a higher modulus of elasticity. The small sample size compromises the conclusions addressed from this study, and further work will be necessary to confirm the present results.

Case reports of three atypical infiltrative keratitis events with high DK soft contact lens wear

PURPOSE

We report three atypical infiltrative keratitis events in patients that had successfully worn highly oxygen permeable (Dk) soft contact lenses on an extended wear (EW) schedule for at least 15 months. These cases highlight the role of patient/practitioner education, patient compliance, examination, and appropriate referrals that are required to reduce the risk of complications during lens wear.

METHODS AND RESULTS

Each patient had been wearing high Dk soft lenses on an EW schedule with monthly replacement for at least 15 months and presented with severe pain, redness, and photophobia. The events were characterized by focal infiltrate(s) with an overlying epithelial defect in the superior periphery to mid-periphery of the cornea and extensive diffuse infiltration.

CONCLUSIONS

The signs and symptoms of each case were more severe than is typically associated with contact lens-related infiltrative keratitis. Because of the slow progression of signs and relatively fast resolution, the cases were not found to be microbial keratitis. Although high Dk soft contact lenses overcome hypoxia-associated complications associated with extended wear, patients and practitioners must be vigilant as adverse events can still occur and in rare instances can be severe. Education and patient compliance are a crucial part of successful management of patients on EW schedules. Constant reinforcement is necessary to ensure patient compliance.