Reset A Novel Wetting and Cleaning Drop
For Enhanced Contact Lens Comfort
Author: Mr Nick Atkins
Whether we look in the general or contact lens wearing populations, practitioners are dealing with an increasing number of patients complaining of symptoms associated with ocular dryness. Contact lens wearers are far more predisposed to dryness symptoms and signs with it being a well-documented cause of discontinuation1 and this remains one of the chief challenges still remaining in contact lens practice.
Whilst the goal of eliminating hypoxia has largely been resolved with the advent of silicone hydrogel materials, the equally important criteria for patient acceptance - comfort - has yet to be completely solved. Discontinuation from contact lens wear occurs as a result of poor comfort in seventy two percent of the cases,2 with dryness being the most commonly reported symptom.3-5 Symptoms of discomfort and dryness with contact lens wear have been related to lens movement and edge profiles,6 dehydratation,7 protein and lipid deposition,8 modulus of rigidity, wettability and lubricity,9,10 and solution toxicity.11,12
Whether the patient is fitted for daily wear, with hydrogel or silicone hydrogel lenses, or flexi, extended or continuous wear with silicone hydrogels, it can be seen that problems can still occur and that these are ultimately linked to the drop-out rate for contact lens wear. Clearly getting to the root cause of the problem and ideally resolving it with a change of lens type, modality or lens care system would be seen as ideal, particularly where the problem is potentially contact lens wear threatening; however one area that is frequently overlooked in less severe and intermittent cases is the role that might be played by comfort/rewetting drops. For both daily and continuous wear a case can be made for the use of rewetting drops to assist with comfort issues due to dryness, dehydration and, with the addition of a surfactant, deposition.
In recent years there have been numerous new eye drop introductions, with different active ingredients, that target specific areas of the tear film with the aim of restoration and prolonged symptom relief. With correct diagnosis of the underlying cause as well as understanding of the differences between products and how they work, practitioners can increasingly help improve their patients' comfort during prolonged wearing times, during certain tasks and/or in adverse environments.
The ideal contact lens rewetting solution can be said to require the following key features:
- Provide immediate relief
- Gives prolonged residency in the tear film/on the contact lens surface
- A preservative free (non-toxic to the ocular surface)
- Does not blur vision following instillation
Additional benefits might include
- Helping to maintain a clean contact lens surface
- Easy/simple to use/instil
- Small droplet size to avoid blurring/washing away the tear film
Introducing RESET Dual Action Lensdrops
RESET (Figure 1) is a new generation contact lens wetting and cleaning drop, marketed in the UK by Advanced Eyecare Research and indicated for relief of ocular discomfort due to alteration of the pre-corneal tear film during contact lens wear. The drop is compatible with all types of contact lenses and may be instilled directly in the eye during lens wear. It is preservative-free in the eye and comes in a convenient 10ml multi-dose bottle.
In order for drop instillation to be as comfortable as possible the solution should have a pH and tonicity close to natural tears. The pH of tears is 7.4 - 7.5 with most drops around pH 7.4. Most solutions are an isotonic solution of 0.9% sodium chloride although occasionally a hypertonic solution is used in severe aqueous deficient dry eye to increase corneal absorption. Viscosity is extremely important with the right level ensuring the appropriate level of lubrication and retention. Too low and although it spreads well it will evaporate quickly. Too high can increase retention time but is likely to disturb vision.
For many years cellulose derivatives have been used as the standard therapy in preparations often referred to as 'artificial tears'. An example of such a solution is Hypromellose. Cellulose derivatives are water soluble polymers formulated in a range of viscosities to enhance retention time of the drop in the eye. They can be useful for mild or transient, environmental dryness symptoms, as they provide immediate effect and do not blur the vision. Carboxymethylcellulose (CMC) is a semi-synthetic derivative of cellulose used as a lachrymal substitute due to its mucus-like properties and particularly high ocular tolerability.
Table 1 shows the key elements, as well as their concentration and primary function, of the RESET formulation. In addition to the actives CMC and Pluronic F127, product conservation is maintained with the OxyChlorite system, whose principal characteristic is to guarantee the microbiological safety of the product inside the bottle and then to rapidly decompose into non toxic substances, after being instilled in the eye and coming into contact with the proteins and enzymes naturally present in the tear film and on the surface of the cornea. As a result, these characteristics permit the product to avoid the problems due to the use of traditional preservatives in ophthalmic preparations.
OxyChlorite is part of a new category of ophthalmic "physiodegradable" product conservation systems known as oxychloro derivatives or Stabilized Oxychloro Complexes (SOC) and was first seen in Regard, the preservative free multipurpose solution from Advanced Eyecare Research, in 200313. The preserving action is the result of the synergy between the chlorite ion and hydrogen peroxide, which provides an active disinfection and then releases oxygen to the corneal surface (Figure 2)14. Sodium chlorite generates chlorine dioxide which is very effective in killing Gram + and Gram - bacteria, yeasts and fungi, subsequently breaking down into the components of natural tears, salt, water and oxygen. Sodium chlorite is activated by acidic cellular components and has been used safely for many years as a treatment for municipal drinking water.
A recent study evaluating RESET for ocular tolerability, efficacy in improving ocular comfort and protein deposit cleaning ability found that using the drops at least 3 times a day enhances lens comfort by both wetting and cleaning the contact lenses15. The clinical efficacy was evaluated in a controlled, in-vivo, contralateral eye (RESET in one eye, physiological saline in other eye) study over 45 days (visits at 15, 30 & 45 days) with 20 soft (low and high water content, ionic and non ionic materials) and 10 RGP (fluorosilicone acrylate) contact lens wearers. RESET demonstrated excellent tolerability overall and shows a significant reduction in ocular discomfort for both the soft lens wearers (55%, p0.001) and the RGP wearers, although the latter result was not statistically significant (p=0.06).
The accumulation of protein deposits on soft contact lenses was measured in-vitro.
The soft contact lenses utilised with the test and control solutions were analysed by spectrophotometry to quantify the protein deposits on the lens surfaces. The results indicated a statistically significant reduction of 41% (p0,01) in the accumulation of protein deposits on the lenses treated with RESET compared to saline solution. The reduction was statistically significant for the soft contact lens subgroups for Type II and (-52%) and Type III (-51%) lens types. The results are represented graphically in Figure 4.
Reducing corneal staining
Interestingly a recent study has suggested another use for rewetting drops. A recent study has suggested that a CMC-containing pre-application drop can reduce corneal staining resulting from disinfection with a polyhexanide multi-purpose solution (MPS)16.
In this investigator-masked, randomised, two-way crossover study, 30 adapted soft contact lens (SCL) wearers wore a new Group II lens (alphafilcon A, 66% water) daily for 4 weeks and disinfected lenses using a MPS containing 0.0001% polyhexanide.
A lens lubricant containing either CMC or povidone as the primary viscolyser was applied to the lens each day before lens wear. Biomicroscopic signs and symptomatology were assessed. The difference in scores, 0 to 4 weeks and the difference between lubricants were analysed.
The cumulative fluorescein staining scores for combined eyes demonstrated a significant increase over time (e.g., cumulative staining score; p = 0.004 and p < 0.001 for CMC and povidone, respectively, matched pairs t-test, two-tailed), suggesting that for both lubricants the staining worsened with wear. This effect was expected and likely driven by the MPS. However, the mean cumulative staining scores for CMC and povidone were significantly different (p = 0.003) suggesting a greater increase in corneal staining for the povidone lubricant. The symptom scores were not significantly different, 0 to 4 weeks by regimen or between pre-instillation drops.
This result is consistent with a proposed mechanism for CMC to neutralise cationic disinfectants and may offer clinicians another means to reduce this type of corneal staining.
RESET appears to act as an efficacious lubricant for the ocular surface giving the product mucus-like characteristics. A notable aspect of the formulation is the use of OxyChlorite preservative system, which confers the characteristics of a unit-dose drop, in that it is preservative free in the eye with all the associated advantages. It can be speculated that the recommendation of rewetting drops for regular use as part of the wearers care programme is inhibited by the fact that for most clinicians the most important feature - that the drop is preservative free - typically means the use of relatively uneconomic (for frequent daily instillation at least) unit-dose drops. Consequently the availability drops like RESET should begin to encourage more practitioners to 'prescribe' the routine use of such drops with the majority rather than the minority of patients. Perhaps their role should be thought of as discomfort prevention rather than comfort maintenance only if there is a 'problem'?
Anecdotally many patients report better comfort on insertion by adding a rewetting drop into the 'bowl' of the lens. This author and other contact lens practitioners also regularly advocate the use of drops post lens removal17. This may offer a therapeutic benefit by immediately supplementing the tear film following lens removal. Ideally the solution used pre, during and post wear would, out of convenience, be the same and with this rate of usage a multi-dose, preservative free solution would be preferable.
With the lipid deposition that afflicts Group II hydrogels and some silicone hydrogel8 materials there is certainly a case for the use of an in-eye cleaning agent to help maintain a clean lens surface. It can be seen that this might be particularly beneficial for extended and continuous wearers of silicone hydrogel lenses.
On the basis of the above findings RESET can be utilised as a wetting and lubricating drop by healthy contact lens wearers and is well tolerated. Additionally, used as needed, it demonstrates a significant efficacy to reduce the symptoms of ocular discomfort in the group of soft contact lens wearers and although not statistically significant, a general improvement in ocular discomfort amongst RGP lens wearers. Finally, after a continuous use of RESET the accumulation of protein deposits on soft contact lenses was significantly reduced. Being a CMC based rewetting agent, RESET could also assist in reducing the corneal staining sometimes seen with certain silicone hydrogel, MPS combinations.
This makes a strong case for contact lens practitioners to seriously consider recommending the routine the use of an in-eye cleaning and rewetting drop such as RESET, as part of their contact lens care programme in both daily and continuous wear modalities.
Acknowledgements: The author would like to thank Chris Jamieson of Advanced Eyecare Research for his support in producing this article.
1. Sulley A, Management of the dry eye in contact lens practice. Optician, 2003; 226: 24-27.
2. Schlanger JL, Schwartz CA, Leser E. Happy patients: connecting comfort and compliance. Spectrum 1993;8:45-7.