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Despite continuing developments in design and technology, contact lenses are still to realise their full potential in the UK where there are as many as 2.4 million lapsed wearers and almost one in four drop out in the first month of trial.
Recommending the best contact lens for each patient will maximise patient satisfaction and retention, and drive business growth. So said Johnson & Johnson Vision Care's director of professional affairs, David Ruston, introducing the company's latest educational roadshow, 'Getting the balance right'. The events ran in London and Leeds last month and featured three specialists from the US alongside UK speakers.
Say goodbye to dry?
Discomfort and dryness remain the principal causes of dropout. Understanding the relationship between contact lens wear and dry eye is crucial in keeping wearers in lenses. Dry eye specialist Dr Jason Nichols of Ohio State University described a major advance in this area, with the publication - just 10 days previously - of the International Workshop on Meibomian Gland Dysfunction (MGD).
The culmination of two years' research, the workshop involved more than 50 international experts. Dr Nichols said there was evidence that contact lens wear was associated with loss of meibomian glands, and rigid lens wearers showed more loss than soft lens wearers, suggesting lens modulus might be implicated. As many as one in six contact lens wearers experienced discomfort because of MGD or dry eye disease.
The top four strategies for managing dry eye patients were to refit to a different material, prescribe rewetting/lubricant drops, change the solution or refit with a more frequently replaced lens. Other approaches included heat and manual expression, and fish oil supplements.
Dr Cris Schnider of Vistakon, Jacksonville, looked at UV protection as a factor in lens choice. Exposure to UV was a concern throughout life but particularly in the first 12 years, since the lens had little ability to block UV. Children spend more time outdoors and it was often hard to get them to wear sunglasses. Post-Lasik patients also needed UV protection because the cornea was thinner and its UV-absorbing potential was reduced.
UV posed maximum risk to the eye at different times of day to its risk to skin and was a year-round hazard, said Dr Schnider. Northern latitudes, where the sun is low in the sky, posed more risk than southern latitudes. 'We need to have a different conversation with patients when we talk about eyes rather than skin,' she said.
The first line of defence was a broad-brimmed hat and wraparound sunglasses some sunglass designs allowed as much as 45 per cent of light to pass around to the ocular surface. UV-blocking contact lenses afforded significant protection from the peripheral light-focusing effect at the nasal limbus, compared to non-UV blocking contact lenses. 'They're not the primary nor the only line of defence, but an important adjunct in those suitable for contact lenses,' Dr Schnider argued.
Her colleague Dr Lenora Copper reviewed soft lens manufacturing techniques and the material properties that were important to maintain ocular physiology, vision and comfort. Tear component uptake was critical to ocular physiology and different materials had affinities for different components. Uptake could be either good or bad, she pointed out.
Friction was the main driver to understanding the comfort of new materials but solution properties were also a key element in wearer comfort. Changes in surface tension and viscosity could alter on-eye wettability and tear film stability, while pH and osmolarity affected both comfort and lens parameters.
'Dk is dead!' declared Dr Philip Morgan of the University of Manchester, arguing that all current silicone hydrogel (SiH) lenses delivered sufficient oxygen to the cornea and other properties were driving lens comfort. Key material properties were modulus, co-efficient of friction, wettability and deposition, while key design elements included lens volume and edge. Other effects such as lens dehydration were more difficult to relate to comfort.
In her second presentation, Dr Copper examined some of the methods of evaluating these material properties. There were no standardised tests for wettability, co-efficient of friction or modulus and contact lens companies used different ways to present these properties, often with dramatically different results. 'Actually, it's not the numbers that matter, it's how the lens performs on the eye,' she said.
The final frontier
Dr Morgan described a new benchmark for comparing contact lens success: the naked eye. The industry norm was to assess the performance of a new contact lens material or design against another similar product. But the ultimate test of physiological compatibility was a comparison with no lens wear.
His group fitted 75 neophytes with either the TruEye daily disposable SiH or with no lens and followed them for a year. At weeks one and five, wearers reported comfort five times a day using SMS text messaging. Masked slit-lamp examination was carried out at dispensing and at six scheduled visits during the year.
Mean comfort scores were similar for lens and no lens wear and the lens also maintained comfort at end of day. There was no significant difference in bulbar or limbal conjunctival hyperaemia, nor in corneal staining, between wearers and non-wearers. The only difference was for conjunctival staining. Morgan concluded: 'It's getting hard to tell the difference between an eye wearing a contact lens and the naked eye.' ?
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