EYEZONE: Studies & Research


Dr. Razmig Knajian:
A daily disposable designed for healthy contact lens wear

Just over a year since its UK launch, David Ruston and Dr Kurt Moody take a look at the design and performance of the world’s first daily disposable silicone hydrogel contact lens

Since their launch 15 years ago, daily disposable (DD) contact lenses (CLs) continue to be an increasingly attractive option for patients Approximately one in five new contact lens fits around the world are DD, although this varies greatly across different markets from 3 per cent in Canada, 32 per cent in the UK to 64 per cent in Denmark.1 DD wearers enjoy the convenience benefits of no need for care regimens, concerns about deposition issues or about replacement schedules (Table 1). The DD modality has been shown to offer improved vision, health and comfort, with fewer overall complications and unscheduled visits,2,3,4 and greater patient satisfaction,3-8 in particular with  atopic patients.9,10 Within this modality there are now a wide range of options available: different materials, toric and multifocal designs, and all with a wide range of parameters.

 TABLE 1
Daily Disposable contact lens benefits
* Convenience
* No care regimens
* Minimal replacement schedule
* Daily replacement schedule
* Spare lenses
* Improved health and comfort - fewer overall complications & unscheduled visits, greater patient satisfaction
* Advantages for atopic patients
* Wide range materials, lens designs and parameters
TABLE 2
Slicone hydrogel material benefits
* Oxygen performance - no clinical signs of hypoxia
* Longer, comfortable wearing times
* Low protein deposition
* Reduction in symptoms of dryness
* Low on eye dehydration
* Wide range materials, lens designs and parameter
TABLE 3
1-Day Acuvue TruEye specifications, parameters and key features
Material (US adopted name) narafilcon A
Internal wetting agent Yes, via Hydraclear 1 Technology
Water content (per cent) 46
Base curve (mm) 8.5, 9.0
Diameter (mm) 14.2
Centre thickness @ -3.00D (mm) 0.085
Oxygen transmissibility* @ -3.00D (*10-9) 118
Oxygen flux (per cent)** 98
Corneal oxygen consumption (per cent)51 100
Power range -0.50D to -6.00D (0.25D steps)
-6.50D to -12.00D (0.50D steps)
+0.05D to +6.00D (0.25D steps)
UV blocking >96 per cent UVA, 100 per cent UVB
Class 1 UV blocker
Inside-out indicator 1-2-3 inversion indicator
Visibility tint Yes
*Measured via polarographic method, edge and boundary corrected
**Compared to 100 per cent with no lens wear; through lens center -3.00D lens

Much research over recent years has highlighted the issue that around half of current CL wearers suffer from dryness and discomfort-related symptoms.11-18 Findings have also indicated that the symptoms increase during the day19,20 leading to reduced wearing times, dissatisfaction and eventually discontinuation of lens wear.21,22 Developments in contact lens materials, including those for the DD modality, have been driven to combat the issues of end of day comfort and dryness symptoms. However, significant interest over the last decade in silicone hydrogel (SiH) materials has highlighted the amount of available oxygen to the cornea as a limitation of hydrogel DDs.

SiH materials have led to hypoxic signs such as limbal hyperaemia and neovascularisation being considered thing of the past23,24 due to higher oxygen performance compared to conventional hydrogel materials.25 These materials now account for three in 10 of new soft daily wear fits.1 Non-hypoxia related complications have been seen with these novel lens materials, particularly when worn overnight. The higher moduli of early generation materials25-28 led to lower initial comfort29 and mechanical complications, such as superior epithelial arcuate lesions (SEALs) and lens related papillary conjunctivitis (CLPC).23,24,30,31 However, these complications are reduced with lower moduli, next generation SiH materials or changing from overnight to daily wear. Potential incompatibilities between certain combinations of SiHs and preserved multipurpose care regimens causing corneal staining32-34 can be resolved by using preservative- free regimens or careful selection of lens/solution combination. When initially launched as continuous wear lenses, SiHs were heralded as the ‘holy grail’ of overnight CL wear, yet there has been no reduction in the risk of microbial keratitis (MK) with overnight lens wear.35-37 Although the risk of MK has remained the same, with overnight use remaining the biggest risk factor, its severity has decreased with SiH. However, incidence of inflammatory and infiltrative conditions has been shown to be higher, particularly with overnight wear.38,39

In addition to the oxygen performance benefits, some SiH materials have also been shown to alleviate contact lens related dryness and discomfort, in particular in challenging environments. Wettability and lubricity have been improved in some materials, increasing levels of reported patient comfort compared to habitual lenses.40-43 There are now a wide range of commercially available SiH lenses with significant benefits to wearers (Table 2), although until recently these materials were only available in reusable lenses.

As with other modalities, DD wearers need to be compliant with lens replacement, hygiene and not wearing them overnight, as their misuse has been shown to occasionally result in severe complications.44-49 MK incidence with this modality has been found to be similar to that for reusable, disposable hydrogels, with one recent study finding DD wear associated with a lower risk of severe MK.37 The associated MK severity for DD hydrogels has been shown to be lower than with reusable and other soft hydrogel lenses,36 with no DD users losing vision at a level defined by severe MK (VA≥6/12). This article will review the features, characteristics and clinical performance of the most recent DD from Johnson & Johnson Vision Care. It will also discuss practitioner experience with the lens by those who have been prescribing the lens since its initial launch in August 2008.

1-Day Acuvue TruEye
1-Day Acuvue TruEye (1DAVTE), the world’s first DD SiH CL, combines the convenience and health benefits of a DD modality, with the physiological and comfort benefits of SiH material. This lens surpasses the performance of a hydrogel lens in a number of areas, such as no hypoxia related signs due to the increase in oxygen performance. Comfort is also an essential element in the success of any CL, and hence comfort levels equal to or greater than 1-Day Acuvue Moist was also one of the requirements during the lens’ development. Clinical findings have indicated excellent overall and end of day comfort. 1DAVTE parameters and specifications are shown in Table 3. The power range was extended in July 2009 (now from +6.00D to -12.00D), and an additional base curve (9.0mm) was introduced last month, so the parameters now match those for 1-Day Acuvue Moist.

Designed for optimal ocular health The oxygen performance of 1DAVTE compares well with other SiH materials and is considerably higher than hydrogel materials. 1DAVTE has an oxygen transmissibility (Dk/t) of 118 x 10-11 (measured via polarographic method, edge and boundary corrected), and an oxygen delivery profile significantly higher than all other currently available hydrogel DDs for both central and peripheral Dk/t.50 If oxygen flux is considered, 98 per cent of the available atmospheric oxygen reaches the surface of the central cornea with daily wear. 1DAVTE also ensures total corneal oxygen consumption levels equivalent to no lens wear in the open eye for the most commonly used lens powers (Figure 1).51 Corneal oxygen consumption represents the amount of oxygen needed to ensure normal cellular activity underneath every part of the CL52 and can show diffusive and physiological mechanisms during CL wear in different materials. The oxygen delivery of 1DAVTE is expected to have significant benefits for all patients, particularly those who wear lenses long or variable hours, or have higher prescriptions with thicker lenses.

1DAVTE is manufactured from narafilcon A material and the newest iteration of the proprietary Hydraclear technology used by Johnson & Johnson in all their SiH materials (Hydraclear in Acuvue Advance and Hydraclear Plus in Acuvue Oasys). The Hydraclear technology, which permanently embeds a wetting agent into the lens results in lenses with flexibility, lubricity and moisture retention, without the need for a surface coating or treatment. Hydraclear 1 is specifically designed for the DD modality and results in a high volume of polyvinyl pyrrolidone (PVP) throughout the lens matrix. The PVP attracts water, and 1DAVTE is wettable and smooth with a low coefficient of friction. Studies to measure coefficient of friction show that the narafilcon A material has the lowest coefficient of friction of all DD and SiH CLs50 (Figure 2). This provides a lubricious lens material for initial comfort, maintained comfort at the end of the day and minimal impact on ocular tissue. Studies have shown50 that narafilcon A with Hydraclear 1 technology shows no release of the internal wetting agent during wear into the ocular environment. The lens’ dynamic contact angle is equivalent to that for 1-Day Acuvue Moist, giving excellent wettability. Modulus for 1DAVTE is relatively low and similar to that for Acuvue Oasys, with a relatively high water content, similar to Acuvue Advance; these material properties are aimed to minimise issues that can affect comfort and mechanical complications when refitting existing hydrogel wearers.


As with the rest of the J & J SiH CLs, 1DAVTE offers a Class I UV blocker, with the benefits of protection from UV exposure, and has the highest UV-blocking of any DD lens currently on the market (>96 per cent UV-A and 100 per cent UV-B).50 The majority of patients feel that the option of additional UV-radiation protection for their eyes is very important.53 There is evidence to support that UV-blocking CLs help to protect from the concentration of UV radiation at the nasal limbus and nasal lens cortex caused by the peripheral light focusing effect,54 the areas where UV induced tissue changes are most commonly found.


Clinical performance
1DAVTE has technical features to establish it as a premium DD lens: oxygen performance benefits of a SiH material, high lubricity, excellent wettability and UV protection. Information gained since the launch has shown the lens provides excellent on-eye performance with clinical trial results showing excellent comfort.
A study underway at Eurolens Research at Manchester University is comparing comfort and physiological response with 1DAVTE to no lens wear.55 Some 70 neophytes have been age and gender matched, and randomly assigned to either DD SiH lens wear or continuing to wear spectacles. They report on ocular comfort by responding to SMS messages sent to them at five fixed times during the day. Interim, one-month results of the year-long, double-masked, parallel group study were reported at the BCLA conference in May 2009. After one week, lens comfort was high throughout the wearing period and end-of-day comfort equivalent between lens and spectacle wearers. After one month, lens comfort was comparable with that of non-lens wearers, with no decline as the day progressed (Figure 3). Comfort was also shown to improve from weeks one to four with lens wearers, showing an adaptation effect. The adaptation period would be expected to be greatest for these neophyte subjects, and would most likely be less for experienced lens wearers. These early results show that adapted wearers of 1DAVTE should expect consistent, comfortable wear from morning to night, and comfort comparable to wearing no lens at all. The study also showed key measures of ocular physiology (limbal and conjunctival hyperaemia, corneal staining and tarsal conjunctival changes) were unaffected after one month’s lens wear.


A study conducted at five sites in the US56 enrolled 81 current spherical, reusable, frequent-replacement, soft lens wearers (60 per cent were SiH wearers) who were then randomised to either 1DAVTE or 1-DAY Acuvue (1DA) and wore lenses daily for three months. After three months of wear only 17 per cent of 1DAVTE wearers had any symptoms compared with 24 per cent of 1DA. In particular, dryness symptoms were reported by less than half as many 1DAVTE as 1DA subjects (11 per cent vs 23 per cent, P=0.001), with lens awareness noted less frequently in those wearing 1DAVTE (2 per cent vs 8 per cent, P=0.001). All subjects were successfully fitted, and 95 per cent of those assigned to 1DAVTE (41 subjects) successfully completed the study, with those discontinued being due to non-compliance to the protocol rather than a lens-related issue.


Dimensions of ocular health
Patients are more knowledgeable than ever. Hence it is important for practitioners to be aware of a lens’ attributes and how they can benefit wearers, in addition to giving patients confidence that they are being offered a product with the latest performance benefits. Patients are interested in the best lenses for them and their lifestyle, and are keen to try new products, particularly if it allows them to wear lenses when they want to. Seven out of ten contact lens wearers believe that a healthy contact lens for their eyes is extremely or very important, although a survey in 2006 showed that only 16 per cent agreed that their DD met this requirement.57 Additionally, more than 80 per cent of patients are willing to pay more for a lens that offers better ocular health.58


To help describe the features and benefits of 1DAVTE to patients, practitioners can explain how the different aspects relate to the main dimensions of ocular health. Health the practitioner and patient can see, such as whiter eyes, is achieved with the lens allowing 100 per cent oxygen consumption and hence having no impact on corneal metabolism. Many patients wear their lenses for long hours, and may be economical with the truth about how long they wear their lenses for fear of being told to reduce or even stop lens wear. 1DAVTE oxygen performance provides a lens with oxygen consumption comparable to no lens wear which should result in ‘guilt-free wear’ for patients. Patients can benefit from comfortably wearing their lenses with fewer symptoms and whiter eyes (Figure 4). Another dimension is health that the patient can feel; this is realised with the Hydraclear 1 technology, giving comfort comparable to no lens wear.50 1DAVTE also offers protective- health with Class I UV-radiation blocking, and the health benefits of the DD modality.

Fitting tips
Practically all patients can be a candidate for 1DAVTE, whether a new or existing wearer, and the parameters enable the lens to be fitted to a wide range of patients. Recommendations can be based on lifestyle. Busy, health conscious patients lead demanding lives who want the freedom to wear lenses for as long as their day lasts are ideal candidates. The lens offers health benefits to all wearers, including part-time wearers, who may still wear their lenses for long hours or wear their lenses for outdoor activities. Additionally many patients will enjoy better end-of-day comfort compared to their habitual lenses. If patients are at least as comfortable as with their current lens, then 1DAVTE offers a better choice due to the additional health benefits during contact lens wear.


DD lenses are a popular option for both practitioners and patients, with the convenience and health benefits the modality offers. Ways to address comfort issues, in addition to highlighting health benefits, will encourage patients to trial new lenses. Although many patients may comment on discomfort and dryness with lens wear, many consider that this is normal and little can be done to improve it. Careful questioning to elicit specific symptoms may reveal that a patient is not entirely happy with comfort throughout the whole day and gives an opportunity to discuss, for example, the Hydraclear 1 technology and benefits of SiH materials, and upgrade them into new lenses.


The fit of 1DAVTE may seem tight in some patients compared with other DDs. Due to the low lens surface friction, lid interaction is minimal and the lens may only show minimal movement on blink in primary gaze. However, it should be freely mobile with the ‘push-up’ test. In those instances where the lens is genuinely tight (ie does not move well during push-up), the 9.00 base curve should be trialled. It is also recommended that the 9.00mm base curve should be the lens of choice for patients with smaller and or flatter corneas.


A small percentage of patients may be more prone to greasing and lipid deposits with SiH lenses than with hydrogel lenses. To minimise smearing and depositing in such patients, ensure patients wash and dry their hands thoroughly before handling lenses and exercise care when applying oil-based cosmetics. If there is any lid margin disease, this should be treated prior to fitting lenses. Once the condition is managed, lens wear will be more successful. For those where deposition does not improve, 1-Day Acuvue Moist has a very low affinity to lipid. During a refit, some wearers may report that 1DAVTE ‘feels different’ compared to their hydrogel lenses. It is important to reinforce the overall health benefits of 1DAVTE and encourage a five day trial for the patient to experience the lens throughout the whole day. The majority will adapt and benefit from end-of-day comfort in addition to the ocular health benefits; the neophyte study described earlier55 showed end-of-day comfort was equivalent to no-lens wear after one week. With the addition of the 9.00mm base curve lens, the small percentage of patients who may not have noticed the benefits of 1DAVTE initially should be re-introduced to the lens as they may benefit from a looser fit.


Daily disposable discussions
On discussing with practitioners their experiences fitting DD lenses, they all concurred that 1DAVTE was a breakthrough in DD lenses, offering no compromise to their patients. ‘1DAVTE is the most exciting new product since the original launch of daily disposable lenses’ said Hayley Wainer. She went on to say that the lens meets all oxygen requirements for no oedema and white eyes, had the benefit of daily disposability for hygiene and convenience. Daska Barnett added that the UV-block was welcomed by both her and her patients.


Wainer liked the fact that with 1DAVTE there was no pressure needed to get patients to watch their wearing time or give their eyes a rest at the end of the day; it enabled her to allow patients to wear their lenses all waking hours which they appreciate with busy lives, along with less redness at the end of the day. Another area that benefits many patients has been comfort with the new lens. ‘I find 1DAVTE to be an excellent product for minimal dryness, in particular in challenging environments such as air-conditioned offices and working with computers,’ said Wainer, and Liya Ali was impressed with the high levels of initial comfort for the lens.


When refitting patients into 1DAVTE, it is important to manage patients’ expectations when they have been wearing comfortable, low modulus hydrogel lenses such as 1-Day Acuvue Moist. Wainer finds she has good success in such situations by explaining all the lens’ benefits, but that it may take a few days for them to settle into a new, better material. Barnett added that some patients do not always see an improvement in comfort over their existing lenses when refitted with 1DAVTE, but again she reminds patients that she will notice a difference to their ocular physiology. Ali concluded that 1DAVTE represented a healthier lens for peace of mind, comfort and convenience, and did not think there was anything else one could ask for in a DD lens. Barnett added that 1DAVTE is now her lens of first choice and says to her patients that she ‘cannot recommend it highly enough because it is better for you’.


Conclusions The physiological performance and comfort of lenses should be considered when choosing the optimal DD lens to prescribe. In addition to the benefits for patients, this will help with growth of our practices in terms of long-term patient satisfaction and previous discomfort-related CL drop-outs. 1DAVTE is the first contact lens to combine the health and comfort benefits of a silicone hydrogel material with the hygiene and convenience of a daily disposable, enabling practitioners to fit contact lenses to a wide range of patients while helping to maintain eye health during contact lens wear. The era of compromise between the optimal material and replacement frequency may be over.


References

A list of references is available from the clinical editor at william.harvey@rbi.co.uk M David Ruston is professional affairs director for Johnson & Johnson Vision Care, Northern Europe. Dr Kurt Moody is associate director of new product clinical performance research at Johnson & Johnson Vision Care, Inc, Global Headquarters in Jacksonville, Florida.


   

 

 

 

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