Corneal staining and its clinical relevance or otherwise has been one of the hottest topics this year, and interest shows no sign of abating in the year to come.
The debate centres on the Andrasko Corneal Staining Grid,1 which reports the average staining area with various lens/solution combinations after two hours of lens wear (Optician, March 1). Funded by Alcon, the grid has now been available online for over a year and its developers Dr Gary Andrasko and Dr Kelly Ryen have since published some of their findings in the US.2
In the September issue of Contact Lens Spectrum, researchers at the Institute for Eye Research (IER) in Sydney, Australia, published new data on solution-induced staining in silicone hydrogel wear which they said showed 'deficiencies' in the staining grid.
Co-funded by CIBA Vision, the IER Matrix Study by Carnt et al3 followed 640 subjects using various combinations of solutions and lenses over three months. The study looked at four silicone hydrogel lenses (Johnson & Johnson's Acuvue Advance and Acuvue Oasys, CIBA Vision's O2Optix and Bausch & Lomb's PureVision) when used with four brands of solution (CIBA's AOSeptPlus (Clear Care) and Aquify (SoloCare Aqua) MPS, and Alcon's Opti-Free Express and Opti-Free RepleniSH).
In this study, longer term wear with the Opti-Free solutions showed relatively poorer performance with Acuvue Oasys, O2Optix and PureVision lenses compared with Andrasko's findings. The authors concluded that 'short-term testing' based on the extent of staining at two hours did not reflect performance over time and could not predict long-term clinical success. Currently, the only way to virtually eliminate solution-induced staining with silicone hydrogel lenses was to use hydrogen peroxide, they said.
Those interested in following these claims and counter-claims can read Dr Andrasko's subsequent contribution to the debate by logging on to his blog,4 where the results of staining studies conducted in Japan5 are also discussed.
Real or random?
In the latest study, published in the November issue of Contact Lens Spectrum, researchers at CIBA Vision and the University of Alabama conducted a statistical analysis of the staining grid data to determine whether they represent real differences in product performance or random occurrences.
Dillehay et al6 found that the data only supported consistent non-random differences in corneal staining with ReNu MultiPlus (branded or generic) when used with B&L's PureVision and SofLens 66 and with CooperVision's Proclear lens, and for Complete MoisturePlus when used with PureVision and SofLens 66.
These authors also pointed to underlying problems with Andrasko and Ryen's study design and said that the staining grid might be adding confusion instead of simplifying the selection of lens/solution combinations. The colour-coding system used in the staining grid to categorise the level of staining and its significance had led many practitioners to believe that there were substantial product differences where none existed, and no substantial differences where some did exist, they said.
Earlier this year, B&L and Alcon settled a lawsuit filed by B&L concerning Alcon's use in promotional material of the colour-coded chart. The lawsuit was dismissed without payment of damages from either party. A paper in the November issue of Eye & Contact Lens by researchers at Bausch & Lomb and the University of Waterloo, Canada continues the debate between these two companies surrounding the biocompatibility of their products.
Bantseev et al7 used confocal laser scanning microscopy to study the epithelium of bovine corneas treated with two contact lens solutions. Image analysis indicated significantly fewer mitochondria only in the superficial epithelium after treatment with ReNu MultiPlus, whereas Opti-Free Express produced significantly fewer mitochondria in both the superficial and intermediate epithelial layers.
The authors concluded that the Alcon solution had the potential for deeper mitochondrial effects.
Children's wear
Another paper in the same issue of Eye & Contact Lens has some interesting findings on a very different subject.
In the latest report from the Contact Lenses in Paediatrics (CLIP) Study Group, Walline et al8 examine the benefits of contact lens wear for children (aged 8-12) and teens (aged 13-17). Subjects completed a quality of life survey while wearing spectacles then after one week, one month and three months wearing silicone hydrogel lenses.
Contact lenses significantly improved quality of life for both groups and there were no differences in improvement between children and teens. Contact lens wear dramatically improved how both groups felt about their appearance and participation in activities, leading to greater satisfaction with their optical correction.
The authors concluded that children should routinely be offered contact lenses to correct refractive error, a rare piece of good news for the patient, practitioner and contact lens industry.
References
1 www.staininggrid.com
2 Andrasko GJ and Ryen KA. A series of evaluations of MPS and silione hydrogel lens combinations. Review of Cornea & CLs, March 2007 36-42.
3 Carnt N, Willcox MDP, Evans V et al. Corneal staining: the IER Matrix Study. CL Spectrum, 200722: 9 38-43.
4 www.staininggrid/blog.aspx
5 www.staininggrid-japan.com
6 Dillehay SM, Long B and Cutter G. A statistical analysis of the staining grid. CL Spectrum, 20072210.
7 Bantseev V, McCanna DJ, Driot J-Y et al. Biocompatibility of contact lens solutions using confocal laser scanning microscopy and the in vitro bovine cornea. Eye & Contact Lens, 2007 33:6 308-316.
8 Walline JJ, Gaume A, Jones LA et al. Benefits of contact lenses for children and teens. Eye & Contact Lens, 200733:6 317-321.