Human corneal epithelial cell shedding and fluorescein staining in response to silicone hydrogel lenses and contact lens disinfecting solutions

A pilot study was conducted to evaluate human corneal epithelial cell shedding in response to wearing a silicone hydrogel contact lens/solution combination inducing corneal staining. The nature of ex vivo collected cells staining with fluorescein was also examined. A contralateral eye study was conducted in which up to eight participants were unilaterally exposed to a multipurpose contact lens solution/silicone hydrogel lens combination previously shown to induce corneal staining (renu® fresh™ and balafilcon A; test eye), with the other eye using a combination of balafilcon A soaked in a hydrogen peroxide care system (Clear Care®; control eye). Lenses were worn for 2, 4 or 6 hours. Corneal staining was graded after lens removal. The Ocular Surface Cell Collection Apparatus was used to collect cells from the cornea and the contact lens. In the test eye, maximum solution-induced corneal staining (SICS) was observed after 2 hours of lens wear (reducing significantly by 4 hours; p < 0.001). There were significantly more cells collected from the test eye after 4 hours of lens wear when compared to the control eye and the collection from the test eye after 2 hours (for both; n = 5; p < 0.001). The total cell yield at 4 hours was 813 ± 333 and 455 ± 218 for the test and control eyes, respectively (N = 5, triplicate, p = 0.003). A number of cells were observed to have taken up the fluorescein dye from the initial fluorescein instillation. Confocal microscopy of fluorescein-stained cells revealed that fluorescein was present throughout the cell cytoplasm and was retained in the cells for many hours after recovery from the corneal surface. This pilot study indicates that increased epithelial cell shedding was associated with a lens-solution combination which induces SICS. Our data provides insight into the transient nature of the SICS reaction and the nature of fluorescein staining observed in SICS.

The TFOS international workshop on contact lens discomfort : report of the subcommittee on clinical trial design and outcomes

The goal of this report is to review previously published clinical trials addressing contact lens discomfort (CLD) to identify appropriate trial design and outcome parameters to guide future clinical research that will characterize and investigate possible causes of CLD. A further goal is to identify possible confounding features of clinical trial design and performance in order to reduce bias in conduct of future trials or analysis of data from those trials.

An international survey of toric contact lens prescribing

To characterize toric contact lens prescribing worldwide. Up to 1,000 survey forms were sent to contact lens fitters in up to 39 countries between January and March every year for 5 consecutive years (2007–2011). Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Only data for toric and spherical soft lens fits were analyzed. Survey data collected since 1996 were also analyzed for 7 nations to assess toric lens fitting trends since that time. Data were collected in relation to 21,150 toric fits (25%) and 62,150 spherical fits (75%). Toric prescribing ranged from 6% of lenses in Russia to 48% in Portugal. Compared with spherical fittings, toric fittings can be characterized as follows: older age (29.8 ± 11.4 years vs. 27.6 ± 10.8 years for spherical lenses); men are overrepresented (38% vs. 34%); greater proportion of new fits (39% vs. 32%); use of silicone hydrogel lenses (49% vs. 39%); and lower proportion of daily disposable lenses (14% vs. 28%). There has been a continuous increase in toric lens prescribing between 1996 and 2011. The proportion of toric lens fits was positively related to the gross domestic product at purchasing power parity per capita for year 2011 (r2 = 0.21; P=0.004). At the present time, in the majority of countries surveyed, toric soft contact lens prescribing falls short of that required to correct clinically significant astigmatism (≥0.75 diopters) in all lens wearers.

The impact of contemporary contact lenses on contact lens discontinuation

Discontinuation or “dropout” from contact lens (CL) wear continues to afflict the CL industry. This study was conducted to determine whether the advent of new CL materials and designs has impacted the dropout rate and the reasons for discontinuation. Current and lapsed CL wearers residing in Canada were recruited using Facebook to take part in an on line survey investigating CL wearing experiences during 2008 to 2010 and to establish the percentage of participants who temporarily and permanently discontinued CL wear during the period surveyed. Four thousand two hundred seven eligible surveys were received (64% female; median age 27 years). Forty percent had lapsed from lens wear for at least 4 months; however, 62% of the lapsed wearers (LWs) resumed wear. There were no differences between LWs and nonlapsed wearers (NLWs) with respect to gender; however, LWs were older, started lens wear when older, and had not worn lenses for as long as NLWs (all P<0.001). More NLWs than LWs wore silicone hydrogel CLs (49% vs. 38%, P<0.001) and more LWs than NLWs wore daily disposable lenses and hydrogel CLs (24% vs. 19% and 22% vs. 18%, respectively, P≤0.001). Primary reasons for discontinuation were discomfort (24%), dryness (20%), red eyes (7%), and expense (7%). Compliance with lens replacement was no different between LWs and NLWs (48% vs. 45%). About 23% of those surveyed had discontinued CL wear permanently. The primary reasons for dropping out continue to be discomfort and dryness. Dropout rates were lower in silicone hydrogel wearers.

An international survey of daily disposable contact lens prescribing

The aim was to determine the extent of daily disposable contact lens prescribing worldwide and to characterise the associated demographics and fitting patterns. Up to 1,000 survey forms were sent to contact lens fitters in up to 40 countries between January and March every year for five consecutive years (2007 to 2011). Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Survey data collected since 1996 were also analysed for seven nations to assess daily disposable lens fitting trends since that time. Data were collected in relation to 97,289 soft lens fits, of which 23,445 (24.1 per cent) were with daily disposable lenses and 73,170 (75.9 per cent) were with reusable lenses. Daily disposable lens prescribing ranged from 0.6 per cent of all soft lenses in Nepal to 66.2 per cent in Qatar. Compared with reusable lens fittings, daily disposable lens fittings can be characterised as follows: older age (30.0 ± 12.5 versus 29.3 ± 12.3 years for reusable lenses); males are over-represented; a greater proportion of new fits versus refits; 85.9 per cent hydrogel; lower proportion of toric and presbyopia designs and a higher proportion of part-time wear. There has been a continuous increase in daily disposable lens prescribing between 1996 and 2011. The proportion of daily disposable lens fits (as a function of all soft lens fits) is positively related to the gross domestic product at purchasing power parity per capita (r(2) = 0.55, F = 46.8, p < 0.0001). The greater convenience and other benefits of daily disposable lenses have resulted in this modality capturing significant market share. The contact lens field appears to be heading toward a true single-use-only, disposable lens market.

International contact lens prescribing in 2013

Every year since 2001, we have reported data from an international survey of contact lens prescribing in Contact Lens Spectrum. This work, which first started in the United Kingdom, has now recorded information about more than 250,000 contact lens fits in 54 countries. Our approach is simple. We ask contact lens prescribers (optometrists, opticians, or ophthalmologists, depending on the country) to record information about the first 10 contact lens fits that they perform after the start of the survey period each year. Each fit is then weighted to reflect the volume of fits performed by each practitioner. Information is collated at our two survey offices in Manchester, United Kingdom and Waterloo, Canada. For this report of contact lens prescribing in 2013, we report data for 21,673 lens fits in 31 markets around the world.