Keeping Lens Cases Safe
In a study partly funded by Alcon, researchers at Brien Holden Vision Institute and the University of New South Wales in Sydney, Australia, investigated the ability of contact lens storage case cleaning regimens to remove robust microbial biofilms.
Test storage cases were inoculated with 2 mL of 106 CFU/mL of ocular isolates (either 8.3 ±0.2 log CFU Pseudomonas aeruginosa, or 6.5 ±0.2 log CFU Staphylococcus aureus) and incubated for 48 hours. Cases were subsequently treated with either a 10-second rinse with hot water; a 10-second rinse with a multipurpose solution containing polyhexamethyl biguanide and polyquad; soaking with the MPS; or soaking with 3% hydrogen peroxide, followed by either air-drying for six hours or tissue wiping.
The study tested six commercially available multipurpose solutions, a commercially available hydrogen peroxide and povidone-iodine. Twelve clinical isolates (six strains of P. aeruginosa, one strain of P. fluorescens, one strain of Stenotrophomonas malto- philia, two strains of Serratia marcescens, one strain of Alcaligenes xylosoxidans, and one strain of Chryseobacterum indologenes) were cultivated. Four mL of disinfectants and 40 µL of the controlled liquid were put in the cases. After four hours, the liquid was collected.
To test the results with adherent bacteria, 1 mL of controlled Y medium was injected into the storage cases and cultivated stationary for 24 hours. Four mL of disinfectants were placed in the cases after decantation of the Y medium, and after four hours, the inside surfaces of the storage cases were scraped to collect adherent bacteria.
Povidone-iodine displayed the highest disinfection efficacy against planktonic bacteria of all strains, even though most MPSs showed >3 log reduction against all planktonic bacterial strains. The difference was far greater with adherent bacteria: Povidone-iodine and hydrogen peroxide showed >4 log reduction against adherent bacteria, while MPSs showed <3 log reduction.5838
OCT: Seeing More
Test storage cases were inoculated with 2 mL of 106 CFU/mL of ocular isolates (either 8.3 ±0.2 log CFU Pseudomonas aeruginosa, or 6.5 ±0.2 log CFU Staphylococcus aureus) and incubated for 48 hours. Cases were subsequently treated with either a 10-second rinse with hot water; a 10-second rinse with a multipurpose solution containing polyhexamethyl biguanide and polyquad; soaking with the MPS; or soaking with 3% hydrogen peroxide, followed by either air-drying for six hours or tissue wiping.
- Rinsing with MPS or hot water and air-drying cases had no significant effect on S. aureus biofilms; these protocols, however, did partially remove P. aeruginosa biofilms (3.2 to 6.8 log CFU survivors).
- Soaking in MPS for four hours caused no reduction of biofilm.
- Soaking in hydrogen peroxide partially removed biofilms (6.1 ±0.7 log CFU survivors P. aeruginosa; 1.2 ±2.1 log CFU S. aureus).
- Rinsing or soaking cases with MPS, followed by tissue wiping and air-drying showed the greatest reduction in biofilm (0.9 ±0.2 log CFU survivors P. aeruginosa; 3.4 ±1.2 log CFU S. aureus).6480
The study tested six commercially available multipurpose solutions, a commercially available hydrogen peroxide and povidone-iodine. Twelve clinical isolates (six strains of P. aeruginosa, one strain of P. fluorescens, one strain of Stenotrophomonas malto- philia, two strains of Serratia marcescens, one strain of Alcaligenes xylosoxidans, and one strain of Chryseobacterum indologenes) were cultivated. Four mL of disinfectants and 40 µL of the controlled liquid were put in the cases. After four hours, the liquid was collected.
To test the results with adherent bacteria, 1 mL of controlled Y medium was injected into the storage cases and cultivated stationary for 24 hours. Four mL of disinfectants were placed in the cases after decantation of the Y medium, and after four hours, the inside surfaces of the storage cases were scraped to collect adherent bacteria.
Povidone-iodine displayed the highest disinfection efficacy against planktonic bacteria of all strains, even though most MPSs showed >3 log reduction against all planktonic bacterial strains. The difference was far greater with adherent bacteria: Povidone-iodine and hydrogen peroxide showed >4 log reduction against adherent bacteria, while MPSs showed <3 log reduction.5838
OCT: Seeing More
Researchers in Miami and at two medical colleges in China conducted a pilot study to demonstrate the effectiveness of a new ocular surface optical coherence tomography (OS-OCT) device designed to image the ocular surface and tear film underneath the edge of contact lenses, making it possible to study contact-lens-induced ocular surface compression and localized pressure underneath the lens. The OS-OCT system features a custom spectrometer with a depth resolution of 1.6 µm in ocular tissue with a speed of 24,000 A-lines per second.
The light delivery system and a video viewing system were co-axially aligned and mounted on a standard slit lamp. Researchers imaged the ocular surface of one eye of five normal subjects (three males and two females) wearing contact lenses (PureVision, Bausch + Lomb). The system imaged and measured the tear film and epithelium underneath the lens at the periphery of the cornea. Furthermore, a drop of Soothe XP (B + L) placed on the concave side of the lens before insertion served as a scatter enhancer, allowing tracking of the tear exchange underneath the lens over a five-minute period.
The tear-film gap and epithelium around the peripheral cornea and limbus were clearly visualized. (See image, above.) The tear-film gap on the peripheral cornea was 14 ±9 µm thick and 1,361 ±451 µm long on all five eyes; the tear-film gap on the limbus was 30 ±10 µm thick and 858 ±662 µm long in three eyes. The scatter intensity of the tear-film gap underneath the lens edge increased for about one minute and then decreased.6541
Infiltrates: Causes and Effects
The light delivery system and a video viewing system were co-axially aligned and mounted on a standard slit lamp. Researchers imaged the ocular surface of one eye of five normal subjects (three males and two females) wearing contact lenses (PureVision, Bausch + Lomb). The system imaged and measured the tear film and epithelium underneath the lens at the periphery of the cornea. Furthermore, a drop of Soothe XP (B + L) placed on the concave side of the lens before insertion served as a scatter enhancer, allowing tracking of the tear exchange underneath the lens over a five-minute period.
The tear-film gap and epithelium around the peripheral cornea and limbus were clearly visualized. (See image, above.) The tear-film gap on the peripheral cornea was 14 ±9 µm thick and 1,361 ±451 µm long on all five eyes; the tear-film gap on the limbus was 30 ±10 µm thick and 858 ±662 µm long in three eyes. The scatter intensity of the tear-film gap underneath the lens edge increased for about one minute and then decreased.6541
Infiltrates: Causes and Effects
Concerned about the increasing availability of contact lenses from unsupervised sources such as the Internet and local markets—often not accompanied by information about contact lens hygiene and care—researchers at the Strasbourg University Hospital in Strasbourg, France, conducted a prospective, multicenter, case-control study involving 12 university hospitals. They reviewed three years of data regarding all lens wearers presenting with microbial keratitis. Subjects had a complete ophthalmological examination and completed a 51-item anonymous questionnaire to determine subject demographics and lens-wear history. Data from 356 patients were compared to data from 410 healthy CL wearers.
Patients wearing soft contact lenses had a higher risk for MK compared to rigid-lens wearers (relative risk: 4.1; p<0.0001). Among soft lens wearers, daily disposable CL and two-week replacement CL wearers had a greater risk of MK (RR: 1.8; p=0.0443) than monthly replacement contact lens wearers (RR 1.9; p=0.0133). This find ing was associated with failure to fol- low basic rules of hygiene (e.g., not washing hands); lack of professional supervision for daily disposable lenses; and missing the deadline for renewal of two-week replacement CLs.6516
A retrospective, multicenter case control study funded by Alcon, conducted at sites in the United States and Australia, evaluated the association of symptomatic soft contact lens-related corneal infiltrative events (CIEs) with lens material, lens care products and other risk factors.
Clinical records from 166 patients with symptomatic CIEs and known extended-wear status were identified at five academic eye-care centers. Subjects used more than 50 different soft lens brands and more than 10 lens-care brands. Each subject was matched to three controls (who wore soft lenses but were not matched for demographic or lens factors) who had received eye care near the time of each case’s last full exam at that center. Clinical diagnoses were established by an expert panel who were masked to lens and lens care brand.
The data showed that corneal infiltrative events were positively associated with younger patient age, extended wear and reusable soft lenses. Among daily wear users, silicone hydrogels were also a significant risk factor for CIEs; however, use of daily disposable lenses was protective for CIEs. The leading soft lens and lens-care product brands were not significantly associated with development of CIEs in any model.6488
In a study funded by B + L, re-searchers at Medmetrics Inc., in Ottawa, Ontario and at B + L performed a comprehensive review of the medical literature on the annual incidence of corneal infiltrative events in order to estimate the annual economic burden of these events among soft contact lens wearers in the United States (including both direct and indirect costs associated with treatment and management).
In 2010 there were an estimated 35.2 million non-single-use daily wear soft contact lens wearers in the United States. Using an estimated annualized incidence rate for non-severe and severe CIEs of 9.1 and 4.9 per 10,000 wearers, respectively, a total of 32,032 non-severe and 17,248 severe CIEs occurred in United States in 2010. The cost of a non-severe CIE was estimated to be $1,002.90 ($694.56 in direct costs and $308.34 in indirect costs); the cost of a severe CIE was estimated to be $1,496.00 ($913.58 in direct costs and $582.42 in indirect costs). Overall, the total estimated cost of CIEs in the United States in 2010 was estimated to be $57,927,900.
The authors note that although CIEs are relatively rare, the economic burden resulting from them is significant for both the health-care system and individual patients in the United States. Use of improved lens-care regimens and/or daily disposable lenses could help to reduce this burden.5537
Asking the Right Questions
A retrospective study partly funded by CIBA Vision, conducted at optometry schools in the United States and Canada, sought to identify patient behaviors, risk factors and gaps in case histories that were potentially associated with infiltrative or infectious conditions in soft contact lens wearers that clinicians may not be inquiring about.
| Risk Factors Checked in Clinical Case Histories6500
| ||
| Percentage of charts
that included the concern |
Percentage of reviewers
agreeing that concern should be included in charts | |
| Back-up spectacle wear | 50 | 88 |
| Swimming | 33 | 63 |
| Care regimen | 50 | 75 |
| Wearing Schedule | 67 | 88 |
| Hot tub use | 17 | 38 |
| Lens replacement schedule | 67 | 75 |
| Overnight wear | 83 | 88 |
| Respiratory status | 50 | 75 |
The results suggest that important information on risk factors for SCL complications is often absent from the clinical case history. Disparities between existing documentation in the clinical chart and panel perceptions were noted for patient behavior, symptoms, and health status. Compliance issues showed the largest gap between chart presence and reviewer rating of importance; other results from the study are shown in the chart above.
The authors note that development of a risk profile questionnaire for patients would help to define and document the risk factors associated with soft contact lens complications.6500
Patient Actions, Patient Choices
A cross-sectional study conducted at the Ohio State University College of Optometry sought to determine whether compliance with contact lens care regimens was affected by the presence of contact lens-related dry eye. Data for the study were derived from responses to a compliance survey filled out by contact lens wearers with and without dry eye. Eligible subjects had to have worn soft contact lenses for at least one year or more, be between the age of 18 to 39, be wearing daily (non-overnight) lenses, and have good systemic and ocular health.
The Contact Lens Dry Eye Questionnaire was used to determine dry-eye status. A separate compliance survey included several questions regarding ease of contact lens care; rub and rinse practices; contact lens replacement frequency; lens case replacement frequency; solution replacement/topping off practices; and frequency of sleeping in contact lenses. Subjects included 24 asymptomatic lens wearers and 19 with CL-related dry eye. Average age was 26.4 ±5.2 years; 59 percent of the subjects were female. (Notably, 74 percent of the dry-eye group were female, vs. 42 percent of the non-dry eye group.)
The data showed that the dry-eye subjects ranked ease in lens care sig-nificantly lower than the non-dry eye subjects (8.1 ±2.2 vs. 9.5 ±0.9 [p=0.001]). However, for lens rubbing on both surfaces of the contact lens, 47 percent of the dry-eye group reported compliance, while only 17 per- cent of the non-dry-eye group reported compliance (p=0.046). For lens rubbing time, the mean values were 5.8 ±8.3 in the dry eye group and 2.2 ±4.1 in the non-dry eye group, although this difference was not significant (p=0.085). No differences were detected in compliance factors such as contact lens case replacement frequency, care solution topping off, lens rinsing or sleeping in lenses.
The authors note that although perceived ease in lens care was rated lower by the dry-eye group, their lens rub compliance was significantly better than the non-dry-eye group.6519
Researchers at Kinki University School of Medicine in Osaka-Sayama City, Japan, and CIBA Vision in Tokyo, conducted a study to investigate the cleaning efficacy of some brands of daily cleaners for SHCLs contaminated by eye makeup cosmetics and cosmetic cleansing products.
They contaminated five types of silicone hydrogel contact lenses (lotrafilcon A, lotrafilcon B, senofilcon A, balafilcon A and asmofilcon A) with pencil eyeliner, which was painted directly on the lenses, and cosmetic cleansing oil. The lenses were then soaked in saline for 30 minutes, placed on the palm of the hand, rubbed 20 times using an index finger, and rinsed with a multipurpose solution.
The combination of rubbing and MP solution removed the eyeliner pencil marks, although the MP solution by itself was not effective. The cleansing oil, however, was absorbed by the lenses and could not be removed by daily cleaners. Furthermore, the oil caused lens deformation in the senofilcon A, balafilcon A and asmofilcon A lenses. (Lotrafilcon A and lotrafilcon B, which have a plasma coating, were not deformed.) Cleaning cannot reverse deformation.6533
Noting that in past decades multifocal contact lenses have struggled to compete with monovision, researchers at three universities in Canada, Australia and the United Kingdom set out to investigate whether reported improved multifocal lens performance is reflected by a shift in preference toward multifocal contact lenses.
A previous survey conducted in Australia in 1988 to 89 found that 9 percent of presbyopes were fit with multifocal contact lenses; 29 percent chose monovision; and 63 percent chose standard single vision. To gain a more current perspective, the study authors reviewed data regarding 16,680 presbyopic lens fits in patients over the age of 45, collected in 38 countries over the past five years via the International Contact Lens Prescribing Survey Consortium. In addition, published reports of clinical trials were reviewed to assess multifocal lens performance during this time.
The data showed that during the past five years 29 percent of these patients were fit with multifocal contact lenses; 8 percent chose monovision; and 63 percent chose standard single vision. For comparison to the earlier Australian study, the Australian segment of the recent data showed that 28 percent chose multifocal lenses and 13 percent chose monovision (compared to 9 percent and 29 percent, respectively, in 1988 to 89). This suggests a significant increase in the use of multifocal contact lenses since the earlier survey was conducted.6542
Ortho-K and Myopia
The data showed that the dry-eye subjects ranked ease in lens care sig-nificantly lower than the non-dry eye subjects (8.1 ±2.2 vs. 9.5 ±0.9 [p=0.001]). However, for lens rubbing on both surfaces of the contact lens, 47 percent of the dry-eye group reported compliance, while only 17 per- cent of the non-dry-eye group reported compliance (p=0.046). For lens rubbing time, the mean values were 5.8 ±8.3 in the dry eye group and 2.2 ±4.1 in the non-dry eye group, although this difference was not significant (p=0.085). No differences were detected in compliance factors such as contact lens case replacement frequency, care solution topping off, lens rinsing or sleeping in lenses.
The authors note that although perceived ease in lens care was rated lower by the dry-eye group, their lens rub compliance was significantly better than the non-dry-eye group.6519
Researchers at Kinki University School of Medicine in Osaka-Sayama City, Japan, and CIBA Vision in Tokyo, conducted a study to investigate the cleaning efficacy of some brands of daily cleaners for SHCLs contaminated by eye makeup cosmetics and cosmetic cleansing products.
They contaminated five types of silicone hydrogel contact lenses (lotrafilcon A, lotrafilcon B, senofilcon A, balafilcon A and asmofilcon A) with pencil eyeliner, which was painted directly on the lenses, and cosmetic cleansing oil. The lenses were then soaked in saline for 30 minutes, placed on the palm of the hand, rubbed 20 times using an index finger, and rinsed with a multipurpose solution.
The combination of rubbing and MP solution removed the eyeliner pencil marks, although the MP solution by itself was not effective. The cleansing oil, however, was absorbed by the lenses and could not be removed by daily cleaners. Furthermore, the oil caused lens deformation in the senofilcon A, balafilcon A and asmofilcon A lenses. (Lotrafilcon A and lotrafilcon B, which have a plasma coating, were not deformed.) Cleaning cannot reverse deformation.6533
Noting that in past decades multifocal contact lenses have struggled to compete with monovision, researchers at three universities in Canada, Australia and the United Kingdom set out to investigate whether reported improved multifocal lens performance is reflected by a shift in preference toward multifocal contact lenses.
A previous survey conducted in Australia in 1988 to 89 found that 9 percent of presbyopes were fit with multifocal contact lenses; 29 percent chose monovision; and 63 percent chose standard single vision. To gain a more current perspective, the study authors reviewed data regarding 16,680 presbyopic lens fits in patients over the age of 45, collected in 38 countries over the past five years via the International Contact Lens Prescribing Survey Consortium. In addition, published reports of clinical trials were reviewed to assess multifocal lens performance during this time.
The data showed that during the past five years 29 percent of these patients were fit with multifocal contact lenses; 8 percent chose monovision; and 63 percent chose standard single vision. For comparison to the earlier Australian study, the Australian segment of the recent data showed that 28 percent chose multifocal lenses and 13 percent chose monovision (compared to 9 percent and 29 percent, respectively, in 1988 to 89). This suggests a significant increase in the use of multifocal contact lenses since the earlier survey was conducted.6542
Ortho-K and Myopia
Funded by the Australian government, researchers at the University of New South Wales, Kensington, in Sydney, conducted a study designed to measure changes in axial length and refractive error associated with overnight orthokeratology in 26 myopic children over the course of a six-month period; changes were compared with conventional daily rigid gas-permeable contact lens wear. (The researchers had commercial ties to Bausch + Lomb Boston, BE Enterprises and Capricornia Contact Lens.)
Twenty-six children with progressive myopia (ages 10.5 to 16.7 years) wore an overnight OK lens in one eye and an RGP lens for daily wear in the other eye for one year; halfway through the trial the lens-eye combinations were reversed. Axial length was monitored using the IOLMaster; spherical equivalent refractive error was measured at baseline and after a two-week washout period of no lens wear, at six and 12 months.
After six and 12 months the OK eye showed no change in axial length and a slight decrease in myopia compared to baseline, whereas the GP eye showed axial length growth and myopia progression. These effects crossed over when the eye-lens combinations were reversed after six months.
- Differences in axial length growth between OK and GP eyes were statistically significant at six months (0.05 ±0.12 mm, p<0.05) and 12 months (0.09 ±0.17 mm, p<0.005).
- Significant differences in refractive error were also found after the two-week washout, both at six months (-0.32 ±0.45 D, p<0.005) and 12 months (-0.57 ±0.66 D, p<0.005).
- Increases in axial length and myopic refractive error in the GP eye were significantly correlated (r: -0.698, p<0.001). Correlation between these variables in the OK eye did not reach statistical significance.
Dr. Asbell is a professor of ophthalmology and the director of cornea and refractive surgery at the Mount Sinai School of Medicine.
