Elizabeth Lumb provides an update on the Clariti Toric family of contact lenses
Toric contact lens fitting is now far removed from being revered as a speciality lens fit and this is reflected when tracking prescribing trends over the past decade.1
Work carried out by Young indicates that over one third of prospective contact lens wearers require an astigmatic correction2 and this closely matches the prescribing habits of UK eye care practitioners (ECPs) for reusable soft toric CLs.1 Better manufacturing and reliable reproducibility, combined with straightforward and predictable fitting characteristics have all contributed to the changes witnessed in prescribing behaviours over this time (Figure 1).
[CaptionComponent="40"]In contrast, the prescribing of toric daily disposable contact lenses has not yet reached the same penetration as the reusable market. There may be several reasons for this and could simply be due to a lack of choice of materials and/or parameters. Equally, practitioners may feel that part-time wearers are less discerning about the quality of their vision and choose to ignore the cylindrical component of the prescription. The patients themselves may perceive the cost-to-benefit ratio of a part-time correction with toric contact lenses prohibitive.
Of course, one of the most significant changes in contact lens prescribing over the last decade has been the way that practitioners have embraced the mantra of ‘silicone as standard’ – certainly for the reusable category and as more silicone hydrogel products come on line in the daily category, this too is showing rapid growth (Figure 2).
[CaptionComponent="41"]Yet despite increasingly sophisticated material changes over the recent years, ECPs can still find themselves faced with compromising contact lens prescribing decisions when dealing with prescriptions that extend beyond the manufacturer’s standard range, especially for their astigmatic patients. On the one hand, they recognise the significant and well documented benefits of prescribing silicone hydrogel lenses,3 yet where parameters are restricted, this can mean that ECPs are shoe-horning patients into silicone hydrogel soft toric corrections that can leave them potentially visually compromised and at risk of dropping out of contact lens wear, or physiologically compromised if faced only with the choice of a conventional hydrogel.
It is well documented that Dk/t of a conventional soft toric hydrogel, remains a significant consideration as the stabilisation method utilises variations in lens thickness and a subsequent and significant regional reduction in Dk/t. In fact, in low Dk prism ballast designs, the inferior cornea may receive as little as a third of the oxygen the superior cornea receives.4
Historically, this hypoxia inducing scenario created contact lens management dilemmas as practitioners were faced with highly motivated patients who had to wear their contact lenses with conservative wearing times as dictated by their practitioner, with the knowledge that the majority were likely to be less than compliant.5
In contrast, the Dk debate in silicone hydrogel lenses appears to have been answered6 allowing patients to wear their contact lenses for as long as they want to, rather than at the discretion of their practitioner in terms of oxygen performance, so it makes sense for practitioners to look to silicone hydrogel materials when considering contact lens options for their astigmatic patients.
Toric prescriptions and dropout
Research tells us that patient retention is a key factor in protecting contact lens business and it is interesting to note that whilst the most recognised reason for dropout of contact lens wear is discomfort, particularly towards the end of the day,7 a disproportionate amount of contact lens dropouts (65 per cent) have uncorrected astigmatism in at least one eye of 0.75DC or more.8 It is worth bearing these facts in mind when considering any astigmatic fit – not just those that reach clinically significant levels of astigmatism, but also those that are currently wearing soft toric contact lenses with residual astigmatism remaining.
Material innovation
In 2005, Sauflon introduced Clariti to the global market; their innovative silicone hydrogel material, with the perfect balance of highly desirable properties that meet the needs of business owners, ECPs and patients alike. Intelligent, sophisticated manufacturing processes allows vast versatility to produce a range of designs that have lead to the development of two award winning products and two complete families of contact lenses offering sphere, toric and multifocal contact lenses.
In 2011, Sauflon launched the world’s first daily disposable silicone hydrogel toric contact lens; a product so innovative it went on to win the 2012 Contact Lens Product of the Year at the Optician Awards.
The success of this lens has naturally led to the development of an increased range of parameters to accommodate even more astigmatic patients who enjoy the freedom and flexibility of a silicone hydrogel daily disposable toric contact lens. The extension to the range now includes two additional cylinder powers (-1.75 and -2.25) and six additional axes making this the world’s largest silicone hydrogel daily toric range available.
The undeniable truth is that spectacle wearers with more significant prescriptions, including moderate to high levels of astigmatism, are incredibly motivated to succeed with contact lenses as they enjoy a better quality of life particularly for appearance but also for driving in glare, wearing non-prescription sunglasses and during exercise.11
While the existing parameter range of re-useable Clariti Toric was already very comprehensive, Sauflon wanted to do more to provide a silicone hydrogel option for practitioners to fit astigmatic patients whose prescriptions fall outside of the standard range. Because of the unique manufacturing process, Sauflon are now able to offer a custom-made silicone hydrogel monthly disposable toric contact lens with cylindrical correction up to -5.75DC and with sphere powers ranging from +10.00 to -10.00 (Table 3). Sauflon’s Clariti XR Toric is a precision lathe-cut, back surface toric giving a highly reproducible custom-made lens with a turnaround of two weeks from order placement. A money-back guarantee is offered if this time frame is not met.
Fitting Clariti Toric and Clariti XR Toric
Sauflon’s manufacturing process and proven toric stabilisation methods mean fitting Clariti Toric contact lenses deliver a predictable result and high practitioner confidence. Fitting banks are available for Clariti 1 Day Toric and Clariti Toric.
Free-of-charge diagnostic lenses are available in the XR range. See Table 4 for five simple steps to fitting.
Back vertex distance (BVD) and toric contact lenses
It is worth remembering that successful fitting is dependent on the lens performing on the eye well in terms of stabilisation, but also, any diagnostics that are ordered match the patient’s corneal refractive power as closely as possible – perhaps more relevant with the more significant astigmatic prescriptions as it becomes essential to consider back vertex distance adjustments in both meridians.
This simple formula below can help when making an adjustment to the power of any spectacle prescription when calculating the required contact lens power. The formula needs to be applied to both meridians of power.
For spherical prescriptions, it is well understood that for high hypermetropes, there will be a requirement to add additional plus power to a contact lens; for myopes, the prescription will reduce. It is helpful to think about what goes into a trial frame during an eye examination when considering any back vertex adjustment for astigmatic prescriptions as the cylindrical element requires consideration in addition to the spherical element as the two case studies show.
A balance of properties
Research into soft contact lens comfort suggests that modulus, thickness, water content and especially lubricity (low co-efficient of friction) are key influencers of end of day comfort.9 The patented Clariti material has been specifically formulated to address comfort with a low modulus, high water content and highly lubricious contact lens and balances this with high oxygen
transmissibility and UV protection to provide the perfect partnering of exceptional ocular health and outstanding long-lasting comfort.
? Lubricity – Research has linked highly lubricious contact lenses and long-lasting comfort.9 Patented AquaGen technology ensures that the Clariti families deliver outstanding levels of lubricity which closely matches that of the cornea, reducing lid-lens interaction and providing all-day comfort.
? Oxygen transmissibility – Vital to ensure optimal ocular health, the Clariti families of contact lenses deliver up to 97% corneal oxygenation yet retains the flexibility and biocompatibility of traditional hydrogel lenses
? Modulus – The flexibility of a contact lens is an important factor to ensure optimal fit and comfort. Lower modulus materials help reduce lens awareness and enhance comfort.
? Water content – Similar to that of traditional hydrogel lenses, the high water content of the Clariti family, combined with AquaGen technology, supports all day comfort
? UV protection – During daylight hours our eyes are exposed to the harmful effects of UV radiation. The Clariti family has built-in UV protection filtering both UVA and UVB rays helping to preserve macular pigment density and promoting long term ocular health.10
? For more information and free trials contact Sauflon on 020 8322 4222 or email info@sauflon.co.uk
References
1 Morgan PB, Efron N. Trends in UK contact lens prescribing 2012. Optician, 2012; 246 (6364): 14-15.
2 Young G, Sulley A, Hunt C. Prevalence of astigmatism in relation to soft contact lens fitting. Eye and Contact Lens, 2011; (37-1): 20-25.
3 ‘Keeping up with the Jonses’ Contact Lens Monthly, Optician, 2011; 23-24.
4 Tyagi G, Collins M, Read S, Davis B. Regional changes in corneal thickness and shape with soft contact lenses. Optometry and Vision Science, 2010; 87(8); 567-575.
5 Collins MJ, Carney LG. Patient compliance and its influence on contact lens wearing problems. Am J Optom Physiol Opt ,1986; 63; 952-6.
6 Brennan N, Morgan PB. Clinical highs and lows of Dk/t. Part 1 – Has oxygen run out of puff? Optician, 2009; 238; (6209): 16-20.
7 Young G. Why one million contact lens wearers dropped out. Contact Lens Ant Eye, 2004; 27(2): 83-5.
8 Young G, Veys J, Pritchard N, Coleman S. A multi-centre study of lapsed contact lens wearers. Ophthalmic & Physiological Optics, 2002; 22: 516-27.
9 Brennan N. A. et al Supporting data linking coefficient of friction and comfort. 2013 BCLA Clinical Conference – Session 17; Lenses and Design.
10 Wolffsohn J.S. et al, Does blocking ultra-violet light with contact lenses benefit eye health? 2012 BCLA Clinical Conference – Session 12; Contact Lenses and the Environment.
11 Pesudovs K, Garamendi E, Elliot D. A quality of life comparison of people wearing spectacles or contact lenses or having undergone refractive surgery. Journal of Refractive Surgery, 2006; (22).
? Elizabeth Lumb is clinical relations manager for Sauflon Pharmaceuticals