Use of silicone hydrogel contact lenses by Australian optometrists

OPTOMETRY ORIGINAL PAPER

Use of silicone hydrogel contact lenses by Australian optometrists Clin Exp Optom 2004; 87: 1: 19-23

Craig A Woods*+BSc (Hons) PhD MCOptom DipCL FAAO FVCO Philip B Morgangll BSc (Hons) PhD MCOptom FAAO * Clinical Vision Research Australia, Victorian College of Optometry + Department of Optometry and Vision Sciences, The University of Melbourne 8 Eurolens Research, University of Manchester Institute of Science and Technology 11 Department of Optometry and Neuroscience, University of Manchester Institute of Science and Technology

Submitted: 28 May 2003 Revised: 6 October 2003 Accepted for publication: 11 October 2003

Background: Prior to the launch of silcone hydrogel (Si-H) materials in Australia in 1999, only 1.6 per cent of lenses were prescribed on a continuous wear basis. Methods:One thousand surveys were distributed randomly to practitioners in Australia during January 2000, 2001 and 2002 (total surveys 3,000). Each anonymous survey requested data about the next 10 patients fitted with contact lenses, including date, age, gender, new fitting or refitting, lens material type, lens design, frequency of replacement, modality of wear, uses per week and care regimen. Results:Twenty per cent (599) were returned, reporting data on 5,976 fittings. A total of 710 fittings used Si-H contact lenses (11.9 per cent), which represented 18.6 per cent of all soft lens fittings. During the three years, the proportion of practitioners prescribing Si-H lenses increased from 42.2 to 52.5 per cent. In 2000, 43.8 per cent were daily wear, which decreased to 32.2 per cent by 2002. The solution system of choice for daily wear lenses was multipurpose solutions (98.4 per cent); the only alternative was hydrogen peroxide systems. Continuous wear represented 11.7 per cent of all fittings, ofwhich 85.7 per cent were Si-H, 3.0 per cent RGP lenses and 11.3 per cent conventional hydrogels. For continuous wear, 79.0 per cent of fittings were to existing wearers, whereas for daily wear, 59.4 per cent were existing wearers. More males were prescribed Si-H continuous wear contact lenses, while females were more likely to be prescribed Si-H on a daily wear basis. Discussion: Si-H contact lenses were introduced to the Australian market as a continuous wear contact lens, yet many practitioners use this product for daily wear with multipurpose solutions. By 2002, more practitioners were prescribing Si-H contact lenses for continuous wear than in 2000, suggesting a growing confidence in that product for that mode of wear. A comparison with an earlier survey shows there is an increase in continuous wear from 1.6 per cent to 11.7 per cent over a five-year period.

Key words: fitting habits, silicone hydrogel contact lenses, survey

The option to use silicone hydrogel (Si-H) materials when prescribing contact lenses in Australia has been available only since the end of the first quarter in 1999. Bausch & Lomb and Ciba Vision launched products that were manufactured using Si-H materials. Since that time, the manu-

facturers have continued to market their products to practitioners and the public as continuous wear lenses. Despite this, some practitioners may have made the decision to use these products for their patients for daily wear.' No information has been delivered to the practitioner from manuClinical and Experimental Optometry 87.1 January 2004

19

facturers regarding the use of these lenses for dailywear,especially regarding the compatibility of care systems designed for use with conventional hydrogel materials. Shuley and colleagues*reported on the use of different lens designs prior to the launch of Si-H material contact lenses.

Si-H fitting in Australia Woods and Morgan

Year

Number distributed

Returned surveys (n)

Returned surveys (Yo)

2000

1000

223

22.3

2001

1000

178

17.8

2002

1000

198

19.8

Table 1. The proportion of responses for each year that the survey was conducted

Figure 1. The proportion of practitioners using silicone hydrogel materials

Figure 2. The distribution of soft contact lens materialsprescribed for both daily and continuous wear

Figure 3. The proportion of silicone hydrogel material contact lenses used for daily wear

Eleven per cent of all lenses were manufactured using rigid gas permeable materials, the remainder being from soft conventional hydrogel materials, while only 1.6 per cent of all contact lenses fitted were prescribed for continuous wear. The reported use of Si-H materials was zero in their study, as was expected. While the paper published by Shuley and colleagues* did not report the proportion of lenses prescribed for continuous wear, a value of 1.6 per cent for the popularity of continuous wear prior to the availability of Si-H lenses has been established (LG Carney,

personal communication). We wished to ascertain whether Si-H contact lenses would be embraced by practitioners, whether they would be used for continuous or daily wear, which solutions would be recommended and to whom these lenses would be fitted.

METHODS Since 1996, an international fitting survey has been conducted. As part of this program, Australia has been surveyed annually since 2000.'-9Each year, the Clinical and Experimental Optometry 87.1 January 2004

20

survey form requested basic background information about the practitioner completing the questionnaire and solicited generic (unbranded) information about the first 10 patients fitted with contact lenses after receipt. Data about each lens fitting fell into the following categories: date, age and gender of patient, new fitting or refitting, lens material, lens design, lens replacement frequency, number of anticipated uses per week, wearing modality and care system prescribed. In addition to the information collected in previous studies, the state and territory in which the optom-

Si-H fitting in Australia Woods and Morgun

Figure 4. The proportion of multipurpose solutions used with silicone hydrogel material contact lenses

Figure 5. The proportion of continuous wear in the contact lens market

Figure 6. The distribution of contact lens materials used for continuous wear

Figure 7. The distribution of new fittings and refittings for silicone hydrogel material contact lenses for all fittings

etrist practised was recorded and a more detailed description of the design of rigid lens prescribed. At the start ofJanuary of each year, 1,000 survey forms were mailed to a proportional selection of practitioners in each state and territory. The selection of practitioners was randomised using randomisation software (Randomisation generator, wwwxandomization.com). This paper reviews and reports the results from the surveys conducted during 2000, 2001 and 2002, particularly relating to practitioner use of Si-H materials.

Use of silicone hydrogel materials

RESULTS

Response rates During the three years, 3,000 surveyswere distributed and a total of 599 were returned (Table 1). The 599 responding practitioners reported on 5,976 contact lens fittings, of which 710 were with Si-H materials. The mean age of the patients fitted with Si-H contact lenses was 31.9 f 11.5 years; the gender ratio was 62:38 (female: male). Clinical and Experimental Optometry 87.1 January 2004

21

The proportion of practitioners who prescribed Si-H materials during the three years of this survey is shown in Figure 1. For the three years of this survey, soft contact lenses represented 88.6 per cent, 91.0 per cent and 88.0 per cent of all lenses prescribed (a mean of 89.1 per cent for the three years). The breakdown for the soft lens materials used is shown in Figure 2. Practitioners chose to prescribe Si-H contact lenses for both daily and continuous wear. Figure 3 shows the proportion of Si-H fittings that were for daily wear.

Si-H fitting in Australia Woods and Morgan

Figure 8. The distribution of new fittings and refittings for silicone hydrogel material contact lenses for continuous wear

Mode of wear (Silicone hydrogel contact lenses) All fittings

Male

Figure 9. The distributionof new fittings and refittings for silicone hydrogel material contact lenses for daily wear

Female

Continuous wear fittings

257 (36.2%) 453 (63.8%) 178 (42.7%) 239 (53.7%)

Daily wear fittings

79 (27.0%)

214 (73.0%)

Table 2. The impact of gender on prescribing of silicone hydrogel contact lenses

Solution use A significant proportion of contact lenses manufactured with Si-H material were prescribed for dailywear.When a practitioner makes the decision to prescribe these lenses for daily wear, the practitioner must determine the solutions for lens maintenance and disinfection. Multipurpose solutions were preferred at the virtual exclusion of other systems (Figure 4).

Continuous wear The introduction of silicone hydrogel materials was intended for continuous wear and the impact of these new contact lens products on this mode of wear is shown in Figure 5. Considering contact lenses solely prescribed for continuous

are statistically more likely than females to be prescribed Si-H based contact lenses on a continuous wear basis (Chi Sq = 18.784, p < 0.0001). The mean age for all patients fitted with Si-H contact lenses was 31.9 11.5 years. Patients who were fitted with these lenses on a continuous wear basis were significantly (F = -3.838, p = 0.0220) older (32.9 f 11.0 years) than those fitted for daily wear (30.5 f 11.9 years). Regarding gender, females (32.1 f 11.7 years) were significantly (F = 4.366, p = 0.0366) older than the males (31.6 f 11.0 years).

*

wear, the distribution of lens materials is shown in Figure 6.

DISCUSSION

New fittings versus refittings

Practitioner use

Refittings occurred when existing wearers were fitted with contact lenses that were different from their previous designs. The proportion of new fittings versus refittings when prescribing Si-H material contact lenses is shown in Figure 7. The proportion of new wearers who were prescribed Si-H lenses for continuous wear (Figure 8) and daily wear (Figure 9) is shown.

During the three years over which this survey was conducted, data were collected from 599 practitioner surveys. The results provided insight into how those practitioners chose to use the innovative products manufactured using Si-H materials. It might be expected that on its introduction, a new product would be used initially by a limited group and that group size would increase with time, if that product were thought to be successful or decrease, if the success were questionable. Clearly, the proportion of practitioners using Si-H lenses has increased, suggest-

Prescribing by patient gender and age The distribution of Si-H material contact lenses by gender is shown in Table 2. Males Clinical and Experimental Optometry 87.1 January 2004

22

Si-H fitting in Australia Woods and Morgan

ing that the popularity of these products is increasing.

Patient demographics Males were more likely than females to be prescribed Si-H material contact lenses on a continuous wear basis. Older patients were also more likely to be prescribed Si-H material contact lenses on a continuous wear basis, so older males would tend to be prescribed continuous wear contact lenses and younger females daily wear lenses.

Continuous wear Continuous wear has grown significantly as a proportion of all fittings from that reported in 1999 at 1.6 per cent (LG Carney, personal communication) to 11.7 per cent overall since Si-H based contact lenses were introduced. Shuley and colleagues2 did not report which materials were used for continuous wear. It might be reasonable to assume that the vast majority of lenses used for continuous wear would have been manufactured from conventional hydrogel materials. The growth during the collection of the data for this survey of continuous wear is at the expense of conventional hydrogel materials a n d has resulted in the majority of the lenses used for continuous wear being manufactured from Si-H materials (overall 88.4 per cent). It is interesting that the use of RGP materials for this mode has increased from 0.3 per cent in 2000 to 5.1 in 2002. The reported use of daily wear of the Si-H contact lenses from this survey suggests a large number of practitioners and patients choosing daily over continuous wear (overall 38.5 per cent). Intuitively, practitioners would be expected to prescribe a new product in the safest mode ofwear, that is, daily wear, and as their confidence grows the choice of mode of wear would change to continuous wear. This survey appears to confirm this, as the proportion of patients fitted with daily wear was reducing each year to a statistically significant level.

Refits versus new fits The decision by a practitioner to prescribe continuous wear must be influenced by

the information available. This can be obtained from several sources: previous experience, the professional literature, the contact lens manufacturers, attendance at research conferences and continuing education symposia. While there is a strong indication that Si-H contact lenses address many of the limitations of other lens materials for continuous wear, practitioners may choose to prescribe this mode of wear for patients whom they perceive as more likely to succeed, such as existing wearers. Data from this survey confirms this, as only 21.0 per cent of continuous wear fittings were to neophytes as compared to 40.6 per cent of daily wear fittings.

Solution use The vast majority of practitioners have chosen to use multipurpose solution systems for the disinfection and cleaning of Si-H material contact lenses. Multipurpose solutions have been chosen to the virtual exclusion of other systems including hydrogen peroxide. This is similar to the practitioners’ solution-prescribing habits for conventional soft hydrogel lenses, suggesting a transfer or an assumption of knowledge from one product to an entirely different product 17pe.I.~ The assumption that any solution can be used with Si-H contact lenses might be naive as there are recent reports of biological compromise relating to use of multipurpose solutions containing polyaminopropyl biguanide with Si-H material^.^.^

CONCLUSION ~

~~

These surveys were conducted during the months of January to March inclusive, in 2000,2001 and 2002. Data were collected for a total of 5,976 fittings and of these 710 were using Si-H materials, representing 11.9 per cent of all fittings. The proportion of practitioners using Si-H material contact lenses increased each year of the survey. While Si-H material based products have been exclusively promoted by industry for continuous wear use, practitioners have chosen to also prescribe these contact lenses for daily wear. Similarly, the use of the Si-H material contact lenses for c o n t i n u o u s wear has Clinical and Experimental Optometry 87.1 January 2004

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increased each year. These lenses have continued to be prescribed for daily wear. Despite very limited information being made available regarding contact lens solutions to be used for disinfection and cleaning, multipurpose solutions were the solutions of choice for 98.4 per cent of patients by 2002. The preference for fitting Si-H material contact lenses to existing lens wearers was evidenced throughout the survey period. This was especially the situation when the lenses were prescribed on a continuous wear basis. When contact lenses were prescribed on a continuous wear basis, Si-H materials were used on the majority of occasions. Practitioners are more likely to prescribe these lenses on a continuous wear basis if the patient is an older male, while younger female patients are more likely to have these lenses for daily wear. ACKNOWLEDGEMENTS

We thank the research staff of Clinical Vision Research Australia and Eurolens Research for processing this survey and Professor Nathan Efron for providing the original concept for the survey. REFERENCES 1. Woods C, Morgan P. Trends in Australian contact lens prescribing 2000. Clin Exp Optom 2000; 83: 323329. 2. Shuley V, Ferguson L, Muller S et al. Prescribing patterns. Contact Lenses, Suppl Australian Optometry, 1999 (Dec): 2-3. 3. Woods CA, Morgan PB. Contact lens prescribing in the Australian states and territe ries 2001. Clin Exp Optom 2002; 85: 279-283. 4. Jones LW, Macdougall N , Sorbara LG. Asymptomatic corneal staining associated with the use of Balafilcon silicone hydrogel contact lenses disinfected with a polyaminopropyl biguanide preserved care regimen. Optom Vis Scz 2002; 79: 753-761. 5 . Epstein AB.SPK with daily wear of silicone hydrogel lenses and MPS. Contact Lens Spectrum 2002; 17: 30.

Author’s address: Dr Craig A Woods Clinical Vision Research Australia Victorian College of Optometry 374 Cardigan Street Carlton VIC 3053 AUSTRALIA