Extended-wear Soft Contact Research Articles

Corneal Vascularization in a Group of Soft Contact Lens Wearers: Prevalence, Magnitude, Type and Related Factors

Groups of 827 soft contact lens wearers and 900 non-contact lens wearers were examined for corneal vascularization by means of biomicroscopy. Slit-lamp photo­graphs were taken to record cases of vascularization and to permit measurements of the magnitude of the vascular response. The prevalence of corneal vasculariza­tion in the soft contact lens group was 33.9% compared to 2.0% in the non-contact lens group.
 Of the soft contact lens related vascular responses, 98.6% were located in the superficial stroma, indicating that the conjunctival circulation is most often involved in cor­neal vascular responses to soft contact lenses. Vascular penetration radially into the cornea from the limbus did not exceed 4.5 mm in either the study or control groups; 96.8% of the vascular responses being 1.5 mm or less in the soft contact lens group. Age and sex of the patients were not significantly related to the observed frequency of corneal vascularization in either the study or control groups. However, refractive error, daily wearing time and the total length of time soft contact lenses had been worn were significantly related to the observed frequency of corneal vas­cularization in the soft contact lens group.
 Even though sampling error and bias affect this type of study, it appears that corneal vascularization is a frequent ocular response in patients who are wearing daily-wear and extended-wear soft contact lenses. This study supports the recom­mendation that all soft contact lens patients, including those who may be asympto­matic, should be carefully examined at regular intervals for signs of adverse ocular responses such as corneal vascularization.

A 24-year-old contact lens wearer with unilateral vision loss requiring penetrating keratoplasty.

A 24-year-old myopic woman from rural Victoria who wore extended-wear soft contact lenses presented at Alfred Health, Melbourne, Australia, with a 2-week history of left eye irritation, redness, photophobia, and reduced visual acuity. She denied sleeping while wearing lenses, trauma, or agricultural exposure. She had been treated with topical ciprofloxacin 0.3% drops without improvement. There was a history of travel to Vietnam but only to coastal city centers. Initial symptoms developed in Australia prior to traveling to Vietnam, where they became progressively worse.

Стан відновного потенціалу глютатіону і пероксідації ліпідів в сльозі пацієнтів, які тривалий час користуються м’якими контактними лінзами

Стан відновного потенціалу глютатіону і пероксідації ліпідів в сльозі пацієнтів, які тривалий час користуються м’якими контактними лінзами

Hydrogel Contact Lens Water Content is Dependent on Tearfilm pH

Based on clinical inferences, investigators theorized in situ soft lens hydration was linked to the precorneal tearfilm pH. Forty-one myopic subjects at Fort Rucker, AL, USA were fitted with one of two types of extended-wear soft contact lenses, and were followed quarterly for a period of 33 mo. The anterior soft contact lens surface pH was measured in situ, while the in vitro lens water content was measured immediately after lens removal, using a hand-held refractometer on one lens, and a gravimetric means of hydration measurement on the other lens. The in situ pH increased logarithmically across extended wearing time, reaching an asymptote at approximately 5 d' wearing time at a pH of 7.45 ± 0.03. Lens water content was shown to similarly decrease at an inversely logarithmic rate, leveling off at 4-5 d' extended wearing time. Both means of hydration assessment correlated well with each other across days' extended wearing time (R = 0.98; p < 0.0001). A log-log dual conversion yielded significantly different linear slopes (p < 0.001), based on a multifactorial analysis of both lens types, by the pH, and by their water content. The differing ionic status of each material accentuated their varied polar attraction characteristics. Two soft lenses, identical in all patient-based parameters, could provide differing oxygen availability, as well as differing physical fits in patients of identical physical characteristics, as a result of their unique tearfilm pH differences. The in situ hydrogel lens water content is directly dependent on the precorneal tearfilm pH.

Pseudodendritic Fungal Epithelial Keratitis in an Extended Wear Contact Lens User

Pseudodendritic keratitis in a contact lens wearer is generally associated with acanthamoeba keratitis. We report a case of isolated pseudodendritic fungal epithelial keratitis that occurred in an extended wear contact lens user. A 48-year-old woman was evaluated in our clinic for a 36-hour history of left eye pain. She wore extended wear soft contact lenses and frequently rinsed her eyes with tap water. Her left cornea had a paracentral 3-mm area of epithelium with raised ridges in a pseudodendritic pattern. The underlying corneal stroma was normal. A therapeutic and diagnostic corneal scraping of the lesion was performed and sent for Gomori methenamine silver (GMS) staining. The clinical concern was for epithelial acanthamoeba keratitis. The GMS staining revealed septate fungal hyphae within sheets of corneal epithelium. The patient was started on frequent alternating natamycin (5%) and amphotericin B (0.15%) antifungal eyedrops and exhibited a rapid clinical response. Her keratitis completely resolved, and her vision returned to her baseline of 20/25. Corneal fungal cultures showed no growth. Our case is an extremely unusual presentation of fungal keratitis, which rarely presents as a pseudodendritic epithelial keratitis. There are two previous similar case reports initially misdiagnosed as acanthamoeba keratitis. Clinicians should be aware that isolated fungal epithelial keratitis can present as a distinct entity and should be considered in the differential diagnosis of pseudodendritic keratitis. The GMS staining is an excellent diagnostic test in a patient presenting with pseudodendritic keratitis because it allows rapid diagnosis of acanthamoeba and fungal infections.

Imposed anisometropia, accommodation, and regulation of refractive state.

To determine the effects of imposed anisometropic retinal defocus on accommodation, ocular growth, and refractive state changes in marmosets. Marmosets were raised with extended-wear soft contact lenses for an average duration of 10 weeks beginning at an average age of 76 d. Experimental animals wore either a positive or negative power contact lens over one eye and a plano lens or no lens over the other. Another group wore binocular lenses of equal magnitude but opposite sign. Untreated marmosets served as controls and three wore plano lenses monocularly. Cycloplegic refractive state, corneal curvature, and vitreous chamber depth were measured before, during, and after the period of lens wear. To investigate the accommodative response, the effective refractive state was measured through each anisometropic condition at varying accommodative stimuli positions using an infrared refractometer. Eye growth and refractive state are significantly correlated with the sign and power of the contact lens worn. The eyes of marmosets reared with monocular negative power lenses had longer vitreous chambers and were myopic relative to contralateral control eyes (p < 0.01). Monocular positive power lenses produced a significant reduction in vitreous chamber depth and hyperopia relative to the contralateral control eyes (p < 0.05). In marmosets reared binocularly with lenses of opposite sign, we found larger interocular differences in vitreous chamber depths and refractive state (p < 0.001). Accommodation influences the defocus experienced through the lenses, however, the mean effective refractive state was still hyperopia in the negative-lens-treated eyes and myopia in the positive-lens-treated eyes. Imposed anisometropia effectively alters marmoset eye growth and refractive state to compensate for the imposed defocus. The response to imposed hyperopia is larger and faster than the response to imposed myopia. The pattern of accommodation under imposed anisometropia produces effective refractive states that are consistent with the changes in eye growth and refractive state observed.

Thermoplastic amphiphilic conetworks

Our main objective was the design, synthesis, characterization, and testing of a novel class of materials, thermoplastic amphiphilic conetworks (TP-APCNs). A further objective was the evaluation of TP-APCNs as biomaterials, for example, as immunoisolatory membranes in a bioartificial pancreas, or as extended-wear soft contact lenses. The synthesis of the first TP-APCNs was accomplished by blending an amphiphilic graft polymer, poly(dimethyl acryl amide)-g-polydimethylsiloxane (PDMAAm-g-PDMS), with a commercial PDMS-containing polyurethane (PU). The common PDMS segments coalesce and form a single phase, whereas the hard/crystalline segments of the PU physically crosslink the blend. The properties of TP-APCNs can be controlled by the graft/PU ratio and segment molecular weights. TP-APCNs with cocontinuous hydrophilic and hydrophobic phases were prepared as demonstrated by swelling in water and n-heptane. Depending on the blend ratio and molecular weights, optically clear water-swollen TP-APCNs with 0.5–4 MPa tensile strength, 70–280% elongation, together with 2–11 × 10−7 cm2/s glucose permeability, and 1.2–8 × 10−8 cm2/s insulin permeability were prepared. TP-APCNs are processible by casting and molding. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 682–691, 2009

Isolation of Coagulase-Negative Staphylococci From Extended-Wear Soft Contact Lenses in Asymptomatic Patients: Retracted

Coagulase-negative staphylococci and diphtheroids are normal inhabitants of the outer surface of the human eye. These microorganisms serve as part of the defense mechanism of the ocular anatomy in preventing colonization and infection by pathogenic bacteria. Nevertheless, infections associated with contaminated solutions and cases became serious problems for people who wear soft contact lenses. The aim of this study is to isolate and identify aerobic bacteria, particularly, gram-negative species associated with the use of extended-wear soft contact lenses. Extended-wear contact lenses were collected, using aseptic technique, from the eyes of individuals after 30 days of extended wear (5-7 day intermittent periods) and were examined for adhered aerobic bacteria. Coagulase-negative staphylococci were isolated from 74% of the lenses. Serratia marcescens was found at an incidence of 10% and Pseudomonas aeruginosa at an incidence of 6%. The presence of species of bacteria, including P. aeruginosa and S. marcescens, which have been associated with daily wear soft contact lenses, solutions, and cases also seem to be associated with extended-wear lenses.

Synthesis, characterization and properties of novel highly oxygen permeable amphiphilic membranes

AbstractThe objective of this research was to develop new strategies for the synthesis of novel optically clear highly oxygen permeable membranes exhibiting appropriate water uptake and mechanical properties for possible ophthalmic applications. Thus a series of bicontinuous amphiphilic conetworks containing well‐defined poly‐ (ethylene glycol) and polydimethylsiloxane segments crosslinked by three novel crosslinking/modifying agents were synthesized, characterized, and evaluated. This paper concerns the design and synthesis of the crosslinking/modifying agents (see Fig. 2), and their use for the synthesis of clear, highly oxygen permeable amphiphilic membranes. Select membranes exhibit outstanding oxygen permeabilities (&gt;200 barrers) far superior to contemporary commercial soft contact lenses, together with mechanical properties and water uptake appropriate for extended wear soft contact lens application. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 308–316, 2007

Effects of Extended-Wear Soft Contact Lenses on the Ocular Surface and Central Corneal Thickness

Purpose: New contact lens materials with high oxygen permeability are said to be convenient for the extended-wear (EW) schedule. We evaluated the short-term effect of EW soft contact lens usage on ocular surface and central corneal thickness. Patients and Methods: Fifty-two eyes of 26 patients were included in the study. Sixteen of the patients used the high oxygen-permeable lenses for a 30-day extended-wear schedule (group I). Ten patients used the lenses on a daily wear basis (DW, group II). All patients were evaluated for visual acuity and central corneal thickness by corneal and conjunctival biomicroscopy, Schirmer and tear break-up time (BUT) tests. Impression cytology was performed in the superior/temporal, inferior/nasal quadrants of the conjunctiva, 1 mm from the limbus, with cellulose acetate filter paper. The specimens were graded under light microscopy according to Nelson’s classification. Results: Three patients in the EW group were excluded from the study as they discontinued lens usage due to slight discomfort and hyperemia. Biomicroscopic findings and tear function tests indicated no increased pathological results. Central corneal thickness decreased from 554 ± 9.55 to 546 ± 9.30 µm (mean ± SEM) in the EW group (p = 0.002), whereas no significant change occurred in the DW group. Cytological evaluation of the EW group showed an 88% increase in metaplasia (p = 0.007), especially close to the limbal areas and in the superior quadrants; this ratio was 30% in the DW group. Snake-like chromatin changes were found to be increased, from 4 to 6 patients, in the EW group while it remained the same in the DW group (p > 0.05). Individual comparisons of the initial and final pathological conditions of the ocular surfaces in the two groups showed that there was an increase in pathology in the EW group while there was no significant difference in the DW group. Conclusions: On a 30-day extended-wear basis with high oxygen-permeable lenses, the possible development and increase of conjunctival cytologic changes secondary to mechanical trauma is one of the main remaining problems. Conjunctival and related immunologic pathologies should not be overlooked when prescribing an extended-wear lens schedule.

Time to resolution of contact lens-induced corneal warpage prior to refractive surgery.

To evaluate the resolution of contact lens-induced corneal warpage before keratorefractive surgery. We prospectively studied the eyes of 165 consecutive contact lens-wearing patients evaluated for keratorefractive surgery. Significant contact lens-induced corneal warpage was detected by comeal topography in 20 eyes of 11 patients. Manifested refraction, keratometry, and cornea topography were subsequently recorded during weekly or biweekly reevaluations and were compared with previous measurements for stability. Effects of age, sex, type, and duration of contact-lens wear and the recovery time period to stabilization were analyzed. Overall, a 12% incidence of significant contact lens-induced corneal warpage was found. In patients demonstrating lens-associated warpage, the mean duration of prior contact lens wear was 21.2 years (range 10 to 30 years); lens use included daily wear soft (n=2), extended-wear soft (n=6), toric (n=4), and rigid gas-permeable contact lenses (n=8). Up to 3.0 diopter (D) refractive and 2.5D keratometric shifts accompanied by significant topography pattern differences were observed. The average recovery time for stabilization of refraction, keratometry (change within +/- 0.5D), and topography pattern was 7.8+/-6.7 weeks (range 1 to 20 weeks). Recovery rates differed between the lens types: soft extended-wear 11.6+/-8.5 weeks, soft toric lens 5.5+/-4.9 weeks, soft daily wear 2.5+/-2.1 weeks, and rigid gas-permeable 8.8+/-6.8 weeks. We observed a 12% incidence of significant contact lens-induced corneal warpage in patients undergoing evaluation for keratorefractive surgery. Warpage occurred with all types of contact lens wear but resolved at different rates. To optimize the quality and predictability of keratorefractive procedures, an appropriate waiting period is necessary for contact lens-induced corneal warpage to stabilize. We suggest that resolution of corneal warpage be documented by stable serial manifested refractions, keratometry, and corneal topographic patterns before scheduling patients for keratorefractive surgery.

Invited comment:

Invited comment:

Compensatory changes in eye growth and refraction induced by daily wear of soft contact lenses in young marmosets

Several studies have shown that growth of the primate eye responds in a compensatory direction to both positive and negative spectacle lenses — eyes grow more slowly and become hyperopic in response to positive lenses, and eyes grow more rapidly and become myopic in response to negative lenses. On the other hand, extended wear soft contact lenses, whether positively or negatively powered, induce hyperopia ( Hung & Smith, 1996. Extended-wear, soft, contact lenses produce hyperopia in young monkeys. Optometry & Vision Science 73, 579–584.). We investigated whether responses in a compensatory direction occurred to soft contact lenses worn on a daily wear basis (8 h per day on an 8:16 h light:dark cycle). Ten infant marmosets (8–13 weeks of age) wore a soft contact lens, in one eye only, for 5–9 weeks. Lens powers used were zero ( n=2), +2D ( n=1), +2D followed after 5 weeks of lens wear by +4D ( n=1) for 4 weeks, +4D ( n=2), −2D followed after 5 weeks of lens wear by −4D ( n=2) for 4 weeks, −4D ( n=2). At the end of the lens-wear period the positive lens-wearing eyes were more hyperopic relative to the fellow untreated eyes [mean +2.39±0.24D (SE)] and the negative lens-wearing eyes were more myopic than the fellow untreated eyes [mean −2.48±0.91D (SE)]. Fellow eyes were unaffected by lens wear [mean final refraction +0.45±0.09D (SE)]. Plano lenses did not affect eye growth in either marmoset fitted with plano contact lenses.

Presbyopic contact lenses

The year 1999 will be remembered as the one in which a very successful bifocal soft contact lens was finally available for the millions of presbyopic and emerging presbyopic Baby Boomers. As a result, soft bifocal fits almost tripled in 1 year. The introduction in 1999 of new daily disposable and new high oxygen permeable extended wear soft contact lenses will give practitioners more options to be successful with monovision. Tips from several practitioners on being successful with bifocal soft lenses are given. It cannot be stressed enough, however, that for patients with presbyopia to be successful with these lenses, they must be willing to compromise somewhat on the quality of vision they remember as a 30-year-old.

Extended-wear contact lenses, microbial keratitis, and public health

Extended-wear soft contact lenses (lenses worn continuously for more than 24 h and in many cases for 1–4 weeks) are being relaunched in several countries. This move follows a decade of their restriction by licensing authorities and by contact-lens practitioners because the incidence of microbial keratitis is greater with extended-wear than with daily-wear, soft hydrogel lenses.1,2 Why are extended-wear lenses being revisited and what might be the implications for public health?

Incidence of contact-lens-associated microbial keratitis and its related morbidity

The incidence of contact-lens-associated microbial keratitis is uncertain and its related morbidity in the general population of contact-lens wearers is not known. We examined these issues in a prospective epidemiological study. We surveyed all practising ophthalmologists in the Netherlands to identify all new cases of microbial keratitis reported during a 3-month period in 1996. Follow-up telephone calls were made to examine ocular morbidity. We undertook annual nationwide telephone surveys between 1994 and 1997 to estimate the prevalence of contact-lens wear. Of 440 ophthalmologists contacted, 379 provided information. There were 92 cases of microbial keratitis; 17 used daily-wear rigid gas-permeable lenses, 63 daily-wear soft lenses, and 12 extended-wear soft lenses. The estimated annualised incidence of microbial keratitis was 1.1 per 10,000 (95% CI 0.6-1.7) users of daily-wear rigid gas-permeable lenses, 3.5 per 10,000 (2.7-4.5) users of daily-wear soft lenses, and 20.0 per 10,000 (10.3-35.0) users of extended-wear soft lenses (p<0.00001 for comparison between all groups), Five of the 92 patients achieved a final visual acuity of 20/70 or less. Pseudomonas and Serratia spp were the organisms most commonly isolated. Pseudomonas keratitis accounted for the largest mean diameter of corneal ulcers, the highest mean number of days in hospital, the greatest number of mean outpatients visits, and the poorest visual acuity outcome. The incidence of microbial keratitis among users of extended-wear soft contact lenses in the Netherlands is similar to that reported in the USA during 1989. Awareness of risk factors and improvement in contact-lens materials have not led to a decrease in incidence. Overnight wear should be strongly discouraged.

Secretory IgA epitopes in basal tears of extended-wear soft contact lens wearers and in non-lens wearers.

To determine secretory IgA epitopes in tears of extended-wear soft contact lens wearers and non-wearing controls. We developed enzyme-linked immunosorbent assays (ELISA) to determine the tear concentrations of two epitopes of secretory IgA, the IgA alpha-chain and the secretory component. These epitopes were measured in basal tears of 20 individuals in 6 nights of extended wear of etafilcon A soft contact lenses and in 19 non-lens-wearing individuals. Levels of IgA alpha-chain immunoreactivity were significantly decreased in the lens-wearing group compared to non-lens wearers. However, the level of secretory component immunoreactivity was not significantly different between groups. IgA alpha-chain and secretory component immunoreactvity were highly correlated; however, some samples showed a marked variation between these two values. Tear concentrations of sIgA epitopes are significantly reduced in extended-wear contact lens wearers, and may contribute to the increased susceptibility to ocular infection seen in this group.

Increase in corneal epithelial cell size with extended wear soft contact lenses depends on continuous wearing time: Tsubota K, Hata S, Toda I, Yagi Y, Sakata M, Shimazaki J: Br J Ophthalmol 1996;80:144–147

Increase in corneal epithelial cell size with extended wear soft contact lenses depends on continuous wearing time: Tsubota K, Hata S, Toda I, Yagi Y, Sakata M, Shimazaki J: Br J Ophthalmol 1996;80:144–147

Changes to the ocular biota with time in extended- and daily-wear disposable contact lens use.

Gram-negative bacteria may play a role in the etiology of certain soft contact lens (SCL)-related diseases. Contact lens (CL) wear may modify the normal ocular biota, providing a more favorable environment for potential pathogens. This study reports temporal changes in ocular biota in daily-wear (DW) and extended-wear (EW) disposable SCL use in experienced and neophyte wearers. Lid margin and bulbar conjunctival biota were sampled prior to CL fitting in 26 previous DW SCL users, 18 previous EW SCL users, and 26 neophytes. Wearers were fitted with an etafilcon A CL in one eye and a polymacon CL in the fellow eye. Lenses were worn on a daily basis by the 26 previous DW SCL wearers and on an EW basis by the remaining 44 subjects. The ocular biota was further sampled after 1, 3, 6, 9, and 12 months of wear. The ocular biota consisted of coagulase-negative staphylococci, Corynebacterium spp., Micrococcus spp., and Propionibacterium spp. Potential pathogens were rarely isolated at baseline. No significant trend of increasing ocular colonization was shown for extended CL wear. Lid and conjunctival colonization increased with DW SCL use (P < 0.001), although this increase occurred for nonpathogenic species only. Fewer potential pathogens were isolated from DW SCL than from EW SCL users (P < 0.05). The lid margin consistently showed greater colonization than the conjunctiva and may be a source of potential pathogens during CL wear. Hydrogel CL wear appears to modify the ocular biota. An increased number of commensal organisms were present in DW SCL use. EW SCL use altered the spectrum of organisms isolated. These alterations may suppress the normal ocular defense mechanisms and may be relevant in the pathogenesis of CL-related disease.

The Complications of Excimer Laser Photorefractive Keratectomy for Myopia in the First Year

Objective: To record the frequency and type of complications that occur following photorefractive keratectomy (PRK) for myopia. Design: Prospective, with follow-up for 1 year. Setting: Mater Private Hospital Laser Clinic, Dublin, Republic of Ireland. Patients: One hundred and sixty one myopic eyes in 120 patients. Main Outcome Measures: Any complications occurring in the follow-up period. Patient satisfaction rating, on a graded scale, was recorded in the first 50 eyes in 50 consecutive patients at 1 year. Results: Of 161 eyes 22.4% had early complications of their procedure. These were most commonly caused by the use of routine post-laser medications. Furthermore, only 6% of 50 patients surveyed, failed to achieve their original aim (wholely or in part) in undergoing the treatment. In no case was the visual outcome compromised by non-refractive complications. Conclusions: PRK is safer than extended wear soft contact lens use.