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Italian optometrist Guido de Martin compiled some data on a small-scale comparative trial of the performance of the Safegel lens soon to be released in the UK. Optician reports
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Optician recently reported on a new lens soon to be released in the UK with a hyaluronate element within the hydrogel matrix (Optician, November 17, 2006).
The Safegel will be available as both a one-day and seven-day lens and its features are listed in Table 1. The introduction of hyaluronate into the Filcon B matrix, along with some other mineral components (magnesium, potassium and calcium) allows for its slow release as the lens reaches the ambient ocular temperature (Figure 1).
This release is aimed at stabilising the tear structure over a day of wear to help reduce the common symptoms of dryness found among many contact lens wearers. Ferning tests with hyaluronate show similar properties to tears as compared with normal saline (Figure 2).
So much for the theory - what about the practice?
UK-based trials will be interesting to follow, but a number of Italian practitioners (Safegel's parent company Safilens is based in Italy) took part recently in a trial aimed at assessing patient response upon conversion to the new lens.
TRIAL DESIGN
The sample size was small with 11 patients taking part, so 22 eyes were assessed.
The range of corneal diameters varied from 11.3mm to 12.01mm, with K readings ranging from 8.22mm to 7.36mm.
Power requirements ranged from +2.00D to -8.00D. The subjects all had over six months' experience with average-rated satisfaction, and one or more symptom related to dry eye during periods of habitual contact lens wear.
Neophytes were avoided and the entire sample completed a satisfaction questionnaire prior to refitting, along with undergoing an extensive slit-lamp and corneal profile assessment. Wearers' existing lenses included three types of one-day lens, one-weekly, one silicone hydrogel lens and one annual replacement lens. Refraction and care systems were not changed.
The trial involved the patients switching to the Safegel lens for seven days and then returning to their original lens. At that end of the seven-day period the patients were assessed by questionnaire and clinical examination.
RESULTS
Six of the patients felt the Safegel was better than the lens they were used to, three noted no change and two felt the lens was worse (Figure 3).
When asked to compare with other one-day lens experience, all felt the new lens was an improvement, though little detail was given in the study about the previous level of experience.
As shown in Figure 4, preference was based on comfort and vision stability rather than practicality. Using a one to 10 point scale rating of vision, the average score for the Safegel was one point higher than the average stated for previous lens wear (Figure 6).
For those patients aware of red eyes after lens wear (either 'occasionally' or 'never'), patients rated the red response as less with the Safegel, while the numbers finding no red eye response increased with the new lens (Figure 7).
The results were somewhat similar regarding the perception of dry eye among patients but this time the number of patients never to have any dry eye symptoms switched from none to seven, the majority (Figure 8).
Slit-lamp assessment backed up these perceptions with 18 out of the 22 eyes rated showing excellent fit at the end of the trial period and the same number showing optimal movement (Figures 9 and 10).
To quote one researcher: 'When examined at the end of the day, none of the patients had issues with the lens being immobile in their eye or complained of having difficulties removing the Safegel 1-Day, situations which sometimes occur with existing one-day lenses.'
Perhaps, most significantly for this type of lens, evaluation of dry spots at the end of the day showed none to be present in 18 out of the 22 eyes examined.
LOOKING AHEAD
With an increasingly competitive contact lens market in the UK and a potential patient base for lenses open to those suppliers able to improve comfort in the many patients suffering symptoms of dryness in the modern environment, the launch of Safegel will be viewed with interest.
While the above study is somewhat limited in both design and size, it does suggest that future comparative trials over a wider sample with better controls and randomisation would be useful and possibly confirm that hyaluronate-based lenses are another useful addition to the contact lens practitioner armoury.