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C-54870

Toric soft lens prescribing

Modern designs and materials that deliver improved performance have increased the prescribing of toric soft contact lenses. But there is still potential for growth in daily disposable torics.

Introduction 

Prescribing of toric soft contact lenses has steadily increased in recent years.1 Although prescribing rates vary from country to country, across Spain, Germany, UK and Italy around one in four of all soft lens fits in 2016 (24%) was with a toric design.

The uptake of soft torics has been attributed to a variety of factors, from more lens options becoming available to growing confidence among practitioners in fitting them.3 Toric lens design has also advanced to provide greater fitting stability.

But toric soft lens prescribing still falls short of that required to correct clinically significant astigmatism in all lens wearers.1 Almost a half of potential soft lens wearers (47%) have astigmatism of 0.75DC or greater in at least one eye and more than a third of all eyes (36%) show astigmatism of 1.00DC or more.5

Figure 1

The daily disposable opportunity 

Daily disposable torics in particular are yet to reach their full potential. Worldwide, the proportion of toric fittings that were daily disposables has traditionally been much lower than that of spherical fittings (14% versus 28%).1 While European prescribing data for toric fits from 2011-2015 show reusable torics still tracking slightly below the 36% threshold, daily disposables continue to lag behind by around 10% (see Figure 1: Proportion of toric soft lens fits across 16 European markets that were daily disposable and reuseable, 2011–15. Courtesy of Eurolens Research, 2016).6 Further analysis of prescribing trends in Europe by lens type shows that while spheres were over-indexed in all these years, daily disposable toric lenses were under-indexed compared to reusable torics (see Figure 2: Annual prescribing trends for daily disposable and reuseable lenses across 16 European markets by lens type in 2015. Courtesy of Eurolens Research, 2016).6 

The daily disposable category is currently the key driver for growth in the contact lens market.7 In several European countries, daily disposables now account for a majority of soft lenses fitted. In Italy, nearly six in 10 soft lenses fitted (58%) in 2015 were this modality, with similarly high levels of prescribing in the UK (55%) and Denmark (53%).

Expanding options in toric designs in the silicone hydrogel (SiHy) daily disposable segment are predicted to have a significant impact on this modality’s influence from 2016, as new options offer improved health and convenience.7

Retention with toric prescribing 

Despite advances in toric soft lens technology, dropout has traditionally been more prevalent among toric users than spherical lens wearers.9–10 A recent study found that 73% of new wearers with toric soft lenses were still wearing them after one year compared to 79% with spherical lenses.11 Visual problems were the most common reason for dropout among new wearers of toric lenses, while comfort and handling were more often the reason in spherical lens users. 

Encouragingly, a high proportion of toric non-users (whether dropouts, new wearers or sphere wearers) can be easily fitted with toric soft lenses and the success rate is high (94%).12 Previous dropouts and new wearers achieve visual acuity (VA) comparable to spectacles when fitted with torics, and spherical contact lens wearing astigmats achieve superior VA when refitted. Many astigmats who are not currently using toric soft contact lenses could, therefore, do so successfully. 

Visual quality of life benefits 

New evidence is also emerging that astigmats experience benefits to their visual quality of life (QoL), as well as their vision, when fitted with soft torics. Soft lens wearers with low to moderate astigmatism (-0.75 to -1.75DC) were fitted binocularly with a spherical lens and its toric counterpart.13 After one week’s wear of each lens type, patients reported significantly improved visual QoL scores with torics (overall, for vision clarity and for correction satisfaction) compared to spheres. 

Soft torics were also quickly and easily fitted; fitting times with torics were similar to spheres and there was no significant difference in the number of lenses required for a successful fit.13 

Barriers to toric prescribing 

Since toric soft lenses in general – and daily disposable torics in particular – continue to be under-represented in current prescribing rates, it is important to identify and address potential barriers to their recommendation. 

Historically, practitioners may have perceived fitting soft torics to be complex, requiring more chair time for the fitting process and taking longer to explain astigmatism and the need to correct it. As we have seen, modern torics can be successfully and easily fitted to patients with a variety of lens-wearing experiences.12–13

Some practitioners may tend not to probe too deeply into patient signs and symptoms and assume astigmats are satisfied with their vision correction unless they volunteer otherwise. Others may consider the patient’s astigmatic correction to be too low to require a toric lens or suppose that astigmatism can be masked with spherical lenses.14 In both cases again there is evidence that astigmats fitted with toric lenses benefit from better VA and improved visual quality of life.12–13 

Asking high-quality open questions when taking a history and physically demonstrating the difference that toric lenses make, simply by holding a cylindrical trial lens over a spherical contact lens correction, are useful communication strategies for eliciting the need for a change.15–16 

Business considerations can also come into play. Practitioners may assume that patients are looking for the cheapest possible option or are unable to afford the additional cost of toric lenses. Or they may perceive toric lenses to be less profitable to the practice than spherical lenses due to misconceptions about the time taken to fit them. 

In fact price has been shown to have much less influence on choice of vision correction than practitioners might expect, and health, not cost, is the key driver of purchasing decisions among contact lens wearers.17

Perhaps one of the greatest barriers to toric use is that patients may simply be unaware of the existence of these lenses. The most common reasons given by astigmats wearing spherical contact lenses for not using torics are that they were unaware there were lenses for astigmatism (28%) or that they had astigmatism (22%);12 this points to a need to communicate and explain the condition and the benefits of correction more carefully.16

Figure 2 revised

Prescribing daily disposable torics

With daily disposable toric lenses, the historical lack of parameter and/or material availability may have further compounded the barriers to recommendation. Restricted parameter ranges, such that practitioners were forced to compromise on vision, may have hindered growth. 

The limited SiHy daily disposable options available – when the health benefits of SiHys have made these by far the most popular choice of lens material overall – may also have contributed to slow uptake in this segment.

Practitioners may also be inclined to stick with a hydrogel daily disposable if it is available both as a sphere and a toric, rather than upgrading to a SiHy option. Similarly, recommending an upgrade to the next generation of SiHy materials may be unlikely if suitable parameters are not available. 

A reliable and consistent lens design is also important especially for those already using toric lenses. There may be a reluctance to consider refitting a seemingly successful reusable toric lens wearer into an alternative design in the daily disposable modality. Toric wearers themselves may simply accept potential compromises with their existing lenses and be reluctant to accept or seek a change, even though their preference might be for a daily disposable option. 

The perception that daily disposable users are part-time wearers and so less discerning about quality of vision may also have hampered uptake. In addition, the notion that it could be worth compromising on vision for the convenience of daily disposability may have also had an impact upon prescribing habits. An example might be the prescribing of daily disposable spheres to astigmats for sports, although optimum vision is surely as important or more so in these situations. 

Finally, practitioners may lack confidence in their own product knowledge and fitting skills and need support in handling upgrades from older designs and materials to the next generation of daily disposable torics that are more technologically advanced. 

Figure 3

Drivers to recommendation 

If there are many potential barriers to prescribing daily disposable torics, what currently drives practitioners in recommending these lenses? A new survey aims to understand what practitioners are looking for in a daily disposable toric and the factors that influence their recommendation habits.18 

A total of 131 active prescribers of daily disposables in the UK (50), US (50), and Australia and New Zealand (31) completed the online survey. They were required to conduct 10 or more new contact lens fits and refits in a typical month, of which at least 10% were with daily disposables. 

Almost all the practitioners in the sample were active toric prescribers, currently prescribing daily disposable torics (98%). Respondents had a wide range of contact lens fitting experience, from two years to 45 years (mean 18 years). Two-thirds worked in independent practice and a third in specialist contact lens stores or chains. 

Practitioners were asked to rank in order (from most to least important), the importance to them of various lens features when recommending a particular daily disposable toric. Patient comfort and vision clarity, overall eye health and lens stability, followed by range of parameters were considered the most important attributes (see Figure 3: Key attributes that drive daily disposable toric soft lens prescribing. Equal ranking identified where more than one feature included). Practitioners were then asked to rank seven specific features most important to them when recommending a particular daily disposable toric. Of these lens attributes, vision correction/clarity on insertion and throughout day was most commonly ranked in the top three most important, cited by 51%, followed by patient comfort on insertion and throughout the day (48%) and overall healthy eyes (43%). 

Rotation and stability of the lens, and availability of power range, were the next most frequently cited (30% and 25%, respectively). Limited cylinder axes were considered the greatest obstacle to prescribing daily disposable torics, cited by 70% of eye care practitioners (ECP). 

ECPs were most influenced by the patient’s intended frequency of wear (cited by 21%) when choosing a daily disposable toric lens over monthly or two-weekly torics. But comfort and eye health were the next most common reasons for their choice (17% and 15%, respectively).

Examining each of these factors with reference to recent studies may help to identify what drives ECP recommendations for daily disposable torics and the attributes that new products need to provide. 

Patient comfort

Contact lens discomfort remains the primary reason for discontinuing wear overall.19 Comfortable wear is a priority for ECPs for all patients but is it more of a concern with toric lenses?

In fact there are surprisingly few proven links between contact lens discomfort and toric lens design.20 Dryness symptoms seem to be more frequent among toric soft lens wearers (43% versus 30%).21 But interaction of the lid margin with front surface irregularities may be difficult to distinguish from interaction with a dry lens surface.22

An early study evaluated the clinical performance of toric designs of varying prism and truncation.23 Not surprisingly, there was a tendency for the designs with thicker prism and more truncation to be less acceptable. Using a more recent prism-ballasted, but non-truncated, design, Cho and colleagues found no significant difference in comfort between this design and its spherical equivalent.24

As we have seen, a high proportion of astigmats who are not using torics – whether dropouts, new wearers or sphere wearers – can be successfully fitted.12 But comfort is still the most common reason for failure in all three groups, which suggests we may still not be where we want to be with toric lens comfort. 

Another interesting new finding is the first demonstration of an association between clarity of vision and ocular comfort;25–26 these authors observed that complex psychological factors could influence a change in comfort when vision is blurred. 

If vision and comfort are linked, ECPs need toric lenses that support consistent vision quality as well as providing physical comfort.

Figure 4

Vision clarity

Lens orientation and stability have clearly been an issue with some previous soft torics but does this remain a barrier to wider prescribing? 

A review of the impact of rotational stabilisation methods on toric soft lens performance concluded that the introduction of improved lens designs was among the factors that had contributed to increased success in prescribing these lenses.4 The newer lens designs tend to reduce lens rotation and improve rotational stability, resulting in more stable vision. 

A recent study compared lens orientation and rotational recovery of five soft toric lenses.27 Although appropriate fitting was achieved with all the lenses tested, a design using optimised prism-ballasting stabilisation helped reduce lens rotation and improve rotational recovery compared to other designs. 

Other authors have found that a range of patient and lens factors influence toric soft lens fit and acknowledge that blink dynamics and lens-lid interaction are likely to be significant in determining the stability of these lenses, as well as the stabilisation technique used in the design.28 

A stable fit with rapid orientation is especially important at the initial fitting. If vision results are good from the outset, this might be expected to have a positive impact on chair time and on repeat visits. 

Given that visual problems are the most common reason for discontinuation among toric lens wearers who drop out in the first year,11 clear, consistent vision is a particularly important factor when selecting a soft toric for a new wearer. 

Eye health 

The daily disposable modality aligns with practitioner and patient requirements for various attributes, including convenience, simplicity and compliance. What new evidence is there to support the contention that disposing of lenses daily has significant health benefits for soft lens wearers? The 2015 TEMPO study reported annualised adverse events – including corneal infiltrative events (CIEs) – with use of SiHy and hydrogel daily disposable lenses.29 CIE rates of 0.4% and 0%, respectively, were significantly lower than rates reported with reusable soft lenses (3–4% per year), indicating improved safety outcomes with these daily disposables. 

Ocular physiology has traditionally been a concern with toric lens designs since all soft torics have zones of increased thickness to achieve orientation and stabilisation. These zones often cover the limbal area where localised oxygen deficiency could lead to hyperaemia and neovascularisation. Peripheral corneal swelling has been noted with a low oxygen permeability (Dk) soft toric but not with an identical toric lens made with SiHy material.30 

New methods for mapping thickness profiles of soft torics have improved our understanding of differences between lens designs and quantified the oxygen transmissibility (Dk/t) across the central optic zone;31 these authors concluded that modern SiHy torics provided excellent oxygen supply to the cornea. 

Optimised soft toric designs that combine the safety profile of the daily disposable modality with the minimal effects on ocular physiology of a SiHy material would, therefore, seem to be desirable. 

Table 1

Lens range 

Increasing uptake of soft torics has been attributed to a variety of factors, from more lens options becoming available to growing confidence among practitioners in fitting toric lenses.3 But is the limited availability of lenses and parameters in daily disposable torics still a barrier to ECP recommendation?

Three-quarters of ECPs surveyed (74%) agreed (‘agree’ or ‘agree strongly’) that they tended to use daily disposable toric and spherical lenses of the same brand. Nearly half (47%) said experience with a spherical lens strongly influenced (‘very influential’ or ‘extremely influential’) their recommendation of a toric lens of the same brand. 

Yet there are still relatively few daily disposable toric options available, both overall and compared to their spherical counterparts (see Figure 4: Daily disposable sphere and toric availability in European markets). 

Availability of power range is an important factor in ECPs’ recommendation of a particular daily disposable toric and limited cylinder axes remain an obstacle to prescribing. Parameter ranges in the toric daily disposable segment still tend to lag behind reusable lenses.32 

Manufacturers need to support practitioners by introducing more daily disposable toric options in a wide range of parameters so that even more astigmats can benefit.

Seizing the opportunity 

The potential for more astigmats to benefit from the convenience and simplicity of daily disposable toric soft contact lenses suggests an opportunity for more proactive recommendation by practitioners and for greater differentiation between products in this segment. 

Practitioners are looking for daily disposable torics that deliver patient comfort and vision clarity, overall eye health and lens stability, and are available in a broad range of powers and cylinder axes.

Now is the time to start a conversation around best practice in toric soft lens prescribing and prepare the way for new options that could mean an end to compromise for our astigmatic patients. 

About the author

Alison Ewbank FCOptom qualified as an optometrist and worked in independent, multiple and hospital practice before embarking on a career in publishing. She is now a freelance writer specialising in contact lenses and anterior eye. 

References

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  2. Data on file, CooperVision 2016
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  4. Edrington TB. A literature review: the impact of rotational stabilization methods on toric soft contact lens performance. Cont Lens Anterior Eye 2011;34:3 104-110
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  6. Morgan PB. Personal communication, 2016
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  25. Rao SB and Simpson TL. Impact of blur on suprathreshold scaling of ocular discomfort. Invest Ophthalmol Vis Sci 2015;56:2304-2311
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  29. Chalmers RL, Hickson-Curran S, Keay L et al.  Rates of adverse events with hydrogel and silicone hydrogel daily disposable lenses in a large postmarket surveillance registry: the TEMPO Registry. Invest Ophthalmol Vis Sci 2015;56:654-663
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  31. Elder Smith A and Hough T. Oxygen transmissibility within the optic zone of soft toric lenses. Optician 2014;247:6442 26-30
  32. The ACLM Contact Lens Year Book, 2016. Association of Contact Lens Manufacturers.