Clear way ahead for contacts
The number of contact lens wearers in the UK has more than doubled in the past 20 years from 1.6 million in 1992 to 3.7 million in 2012.
“Recent advances in lens technology mean contact lenses have never been safer or more comfortable, and is why more and more people are choosing them as an additional option for all-day or occasional wear,” says Andy Yorke, president of the British Contact Lens Association. “New materials and moisturising agents are helping to keep eyes feeling fresh and hydrated for longer, and reducing the risk of infection.”
According to the Association of Contact Lens Manufacturers, 606 million contact lenses were sold in the UK in 2012, with daily disposable soft contact lenses representing 59 per cent of the market. This compares to 35 per cent for soft frequent replacement lenses and just 5 per cent for rigid gas permeable (RGP) contact lenses.
Soft lenses made from silicone hydrogel material are now the most popular option, with a third of contact lens wearers choosing them over conventional hydrogel lenses. Silicone hydrogel lenses allow up to five times more oxygen to reach the cornea, the transparent front part of the eye, thus making them more comfortable to wear for longer with a reduced risk of problems relating to lack of oxygen.
Originally intended for extended or overnight wear, silicone hydrogel materials are now used for all types of soft lenses, including toric lenses for people who have an astigmatism, and bifocal and multifocal lenses for those who require both a near and distance prescription.
Despite a decline in the use of RGPs over the years, some practitioners believe they provide sharper vision and a healthier option for long-term, full-time wear than soft contact lenses. RGP lenses are generally considered to be better at correcting irregularly shaped eyes and are more durable so are usually replaced every six or 12 months.
The aim is to correct vision without the need for spectacles or contact lenses during the day
Toric, bifocal and multifocal lenses are all available in gas permeable materials. New, larger diameter lenses are now increasing in popularity because their size makes them significantly more comfortable than smaller, more traditional RGP lenses.
Providing the best of both worlds – crisp vision and comfortable wear – is the so-called “hybrid” RGP lens, which has a soft periphery with a gas-permeable centre. These relatively new specialist lenses are particularly suitable for those with sensitive eyes and for people with keratoconus, a progressive disease that involves the thinning and steepening, or bulging, of some of the cornea.
But perhaps one of the most exciting advances in RGP lens technology in recent years has been the development of orthokeratology or ortho-k, also known as corneal re-shaping or overnight vision correction. Ortho-k is the use of specially designed RGP lenses to alter the shape of the cornea in order to reduce or correct low to moderate levels of myopia (short sight).
According to the European Academy of Orthokeratology, ortho-k works best for people with a prescription in the range of -3.00D to -6.00D, with no more than -1.75D of astigmatism. The lenses are worn nightly or on alternate nights and removed in the morning. The aim is to correct vision without the need for spectacles or contact lenses during the day. Because the effects on the shape of the eye are temporary, the eyes return to their original shape and prescription if the lenses are left off for a few days.
The main advantage of ortho-k is freedom from vision correction in waking hours. Since it’s possible to see both with and without the lenses, they correct vision around the clock. Many practitioners are also now fitting ortho-k lenses to help control the progression of myopia in both adults and children, and the effectiveness of the technique is increasingly being supported in clinical literature.
Caroline Burnett Hodd, an optometrist at the specialist contact lens practice in London founded by her contact lens pioneering grandfather, Freddie Burnett Hodd, has been fitting ortho-k lenses for around two years. She says: “Going more short-sighted or myopic not only means that you need to make your spectacles or contact lenses stronger, it also has a health impact.
“High myopia makes an eye much more at risk of retinal detachment or conditions such as glaucoma. Up until recently we have had to stand idly by as things got worse, but now we have a contact lens that can help.
“The lens is worn at night and not only does it allow the wearer to see without glasses or lenses during the day, we find that it helps to slow down the increase in myopia. We are fitting patients as young as seven with great success.”
One such patient is ten-year-old Tilly Conant, from Rutland, who Dr Burnett Hodd first fitted with ortho-k lenses around six months ago. “I think the contact lenses are great because I don’t have glasses in the way while I play sport and den building,” says Tilly. “Also I don’t have to worry about my eyes during the day. It took me a few weeks to get used to them, but now I put them in without a thought.”
Dr Burnett Hodd comments: “Of course, the effectiveness of ortho-k for myopia control is not universal and not every child will respond as well as Tilly, but with the additional benefits to the overall long-term health of the eye, it’s certainly a rigid-lens option with an edge.”