OPTOMETRY RESEARCH PAPER. A cost-per-wear model based on contact lens replacement frequency

Transcription

1 cxo_ C L I N I C A L A N D E X P E R I M E N T A L OPTOMETRY RESEARCH PAPER A cost-per-wear model based on contact lens replacement frequency Clin Exp Optom 2010; 93: 4: Nathan Efron* BScOptom PhD DSc Suzanne E Efron BSc(Hons) MPhil Philip B Morgan BSc(Hons) PhD Sarah L Morgan BSc(Hons) MPhil * Institute of Health and Biomedical Innovation and School of Optometry, Queensland University of Technology, Brisbane, Queensland, Australia Mermaid Beach, Queensland, Australia Eurolens Research, Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom n.efron@qut.edu.au Submitted: 10 March 2010 Revised: 12 April 2010 Accepted for publication: 18 April 2010 DOI: /j x Purpose: The aim was to construct and advise on the use of a cost-per-wear model based on contact lens replacement frequency, to form an equitable basis for cost comparison. Methods: The annual cost of professional fees, contact lenses and solutions when wearing daily, two-weekly and monthly replacement contact lenses is determined in the context of the Australian market for spherical, toric and multifocal prescription types. This annual cost is divided by the number of times lenses are worn per year, resulting in a cost-per-wear. The model is presented graphically as the cost-per-wear versus the number of times lenses are worn each week for daily replacement and reusable (twoweekly and monthly replacement) lenses. Results: The cost-per-wear for two-weekly and monthly replacement spherical lenses is almost identical but decreases with increasing frequency of wear. The cost-per-wear of daily replacement spherical lenses is lower than for reusable spherical lenses, when worn from one to four days per week but higher when worn six or seven days per week. The point at which the cost-per-wear is virtually the same for all three spherical lens replacement frequencies (approximately AUD$3.00) is five days of lens wear per week. A similar but upwardly displaced (higher cost) pattern is observed for toric lenses, with the cross-over point occurring between three and four days of wear per week (AUD$4.80). Multifocal lenses have the highest price, with cross-over points for daily versus two-weekly replacement lenses at between four and five days of wear per week (AUD$5.00) and for daily versus monthly replacement lenses at three days per week (AUD$5.50). Conclusions: This cost-per-wear model can be used to assist practitioners and patients in making an informed decision in relation to the cost of contact lens wear as one of many considerations that must be taken into account when deciding on the most suitable lens replacement modality. Key words: Australia, cost-per-wear model, multifocal lens, replacement frequency, soft contact lens, spherical lens, toric lens Many factors are taken into account when choosing the most appropriate contact lens type for a prospective wearer. In the context of soft lenses, consideration may be given to optical and material characteristics such as polymer type, oxygen transmissibility, water content, material modulus of elasticity, surface wettability and lubricity. 1 The range of parameters in which a given lens type is available 2 will dictate whether such a lens can be prescribed for a particular patient. A decision must also be made in respect of the most appropriate lens replacement frequency, such as daily, 3 two-weekly or monthly 4 replacement. All of the above factors impinge on clinical decision-making; however, 2010 The Authors Clinical and Experimental Optometry 93.4 July 2010 Journal compilation 2010 Optometrists Association Australia 253

2 Lens type Replacement frequency Lens Manufacturer Material Lenses per box Spherical Daily 1-Day Acuvue Moist Johnson & Johnson Vision Care Hydrogel 30 or 90 Two-weekly Acuvue Oasys Johnson & Johnson Vision Care Silicone hydrogel 6 Monthly Air Optix CIBA Vision Silicone hydrogel 3 Toric Daily 1-Day Acuvue for Astigmatism Johnson & Johnson Vision Care Hydrogel 30 or 90 Two-weekly Acuvue Oasys for Astigmatism Johnson & Johnson Vision Care Silicone hydrogel 6 Monthly Air Optix for Astigmatism CIBA Vision Silicone hydrogel 3 Multifocal Daily Focus Dailies Progressives CIBA Vision Hydrogel 30 Two-weekly Acuvue Bifocal Johnson & Johnson Vision Care Hydrogel 6 Monthly Air Optix Aqua Multifocal CIBA Vision Silicone hydrogel 3 Table 1. Lenses represented in the cost-per-wear model templated on top of these considerations is the critical issue of cost and affordability. Practitioners will generally make recommendations to prospective lens wearers based on clinical considerations but ultimately the choice of lens type will be affected by the willingness and ability of the patient to pay the price of the recommended regimen. The three key components of contact lens wear are the professional fee, the cost of lenses and the cost of lens care solutions. A compromise may need to be reached between clinical requirements and cost. A wealth of information is available in the literature describing the ocular response to various types of contact lenses 5 but little has been published to assist practitioners and lens wearers balance these considerations against the associated financial burden of this form of optical correction. Although there is a variation in price among different lens brands of a given category (for example, spherical lenses), 6 the factor that perhaps has the greatest impact on the cost of lenses is replacement frequency. In Australia in 2009, virtually all soft lenses prescribed fell into three lens replacement categories: daily (26 per cent of all soft lenses prescribed), two-weekly (42 per cent) and monthly (31 per cent) replacement. 7 Daily disposable lenses are generally perceived as being more expensive than reusable (two-weekly or monthly replacement) lenses, leading many practitioners to prescribe and many patients to request the latter. This notion is over-simplistic because the true cost of lens wear will be impacted by, or be a determinant of, the frequency of use of lenses factors that have not been considered in the literature. Because lens cost has a direct bearing on the joint decision that a practitioner and patient will make in respect of lens type, we feel that this issue ought to receive formal consideration. In this paper, we report a novel cost-per-wear model that provides an equitable means of considering the financial impact of different lens replacement frequencies by factoring in the contributory cost of professional fees, lenses and lens care solutions. The basis of this model is that a direct comparison can be made between the cost of different lens replacement modalities by considering the total cost incurred each time the lens is worn. We refer to this concept as the cost-perwear. METHODS The cost-per-wear is calculated by determining the total cost incurred by a patient over a 12-month period, taking into account professional fees and cost of lenses and solutions, and dividing this total amount by the number of times the lenses are worn in that 12-month period. All monetary values reported in this paper are in Australian dollars (AUD). A professional consultation fee of $ per year is used in this model. This is the recommended fee suggested in the Consultations section of the Eyetalk Reference Guide, 8 an ophthalmic products and services retail price guide that is used widely in Australia. This fee structure is designated as representing a contact lens course of consultations for prescription and fitting, involving a minimum of three visits in six months. 8 To illustrate the structure of this model, the price of one arbitrarily chosen and representative daily, two-weekly and monthly replacement lens brand is selected from the Contact lenses section of the Eyetalk Reference Guide. 6 A different version of the cost-per-wear model is constructed for each of three forms of contact lens optical correction: spherical, toric and multifocal lenses. Details of the nine lenses represented in these models (three forms of optical correction in each of three replacement frequencies) are given in Table 1. Lens care solutions are required for patients prescribed reusable lenses but not for those prescribed single use (daily replacement) lenses. Multi-purpose solutions represented 96 per cent of the Australian lens care market in 2009, with the balance comprising one-step (3.5 per Clinical and Experimental Optometry 93.4 July The Authors 254 Journal compilation 2010 Optometrists Association Australia

3 Days of lens wear per week Days of lens wear in 3 months Volume of solution required for 3 months use (ml) Number of solution bottles purchased for 3 months use a Solution volume of a single bottle (ml) Annual cost (AUD) a. Assuming 8.0 ml of solution is used each day Table 2. Calculation of annual cost of Complete Multi-Purpose Solution Easy Rub Formula for use with twoweekly and monthly replacement lenses cent) and two-step (0.5 per cent) hydrogen peroxide disinfecting systems. 7 In view of the market dominance of multi-purpose solutions, an arbitrarily chosen and representative brand of this solution category Complete Multi- Purpose Solution Easy Rub Formula (Abbott Medical Optics Australia Pty Ltd, Pymble, New South Wales) is used by way of example. The price of this product is determined from the Contact lens care products section of the Eyetalk Reference Guide. 9 Complete Multi-Purpose Solution Easy Rub Formula is available in individual 60 ml, 120 ml, 360 ml and 480 ml bottles and multiple packs of ml and ml bottles. 9 The annual cost of purchasing this solution for use with lenses worn from one to seven days per week, consistent with the assumptions below, is shown in Table 2. In constructing this model, the following assumptions are made with respect to the optical and behavioural characteristics and purchasing patterns of an individual patient: 1. The patient requires a different optical prescription for each eye. 2. The patient is fully compliant with all aspects of lens wear. Thus, lenses are discarded in accordance with the manufacturer-recommended replacement frequency irrespective of the frequency of lens wear. 3. The patient is fully compliant with all aspects of lens care. In particular, contact lens solution bottles are discarded after the recommended expiry time after opening, which is 90 days for Complete Multi-Purpose Solution Easy Rub Formula The patient uses 8.0 ml of Complete Multi-Purpose Solution Easy Rub Formula each day that reusable lenses are worn and makes the most costefficient purchase of solution to last three months at a time. 5. The patient makes the most costefficient purchase of lenses and solutions for three months use at a time. Thus, for example, when faced with a choice of purchasing daily replacement lenses in boxes of 30 or 90 lenses, a patient anticipating wearing lenses one or two times per week would purchase one box of 30 lenses for each eye, whereas a patient anticipating wearing lenses between three and seven times per week would purchase one box of 90 lenses for each eye. A sample calculation of the cost-perwear for daily, two-weekly and monthly replacement spherical lenses worn from one to seven days per week is given in the Appendix. RESULTS The relative contributions of professional fees, lenses and solutions to the total annual cost of spherical contact lenses worn every day is shown for daily, twoweekly and monthly replacement modalities in Figure 1. In this example, daily replacement, two-weekly and monthly replacement contact lenses represent 86, 66 and 65 per cent of the total annual cost of lens wear, respectively. This proportionality is very similar for toric and multifocal lenses. The cost-per-wear model is represented in Figure 2 as a series of three graphs, one each for spherical, toric and multifocal lenses. Each graph shows the relationship between the number of days of wear per week on the x-axis versus cost-per-wear on the y-axis, for daily, two-weekly and monthly lens replacement. General comparison of the three graphs in Figure 2 reveals that spherical lenses have the lowest overall cost, with toric lenses being a little more expensive and multifocal being the most expensive of the three forms of contact lens correction examined. For all optical lens types and lens replacement frequencies, the cost-per-wear decreases with increasing number of days of lens wear per week The Authors Clinical and Experimental Optometry 93.4 July 2010 Journal compilation 2010 Optometrists Association Australia 255

4 In the example of spherical lenses (Figure 2A), there is little difference between the cost-per-wear of two-weekly and monthly replacement lenses irrespective of the number of times per week lenses are worn. For lenses worn one day per week, the cost-per-wear of daily replacement lenses ($5.80) is significantly lower than that of two-weekly replacement lenses ($13.70) and monthly replacement lenses ($13.37). As the number of days of wear per week increases, this difference decreases and at five days of wear per week there is virtually no difference between the cost-perwear of the three lens replacement modalities (approximately $3.00). For lenses worn six or seven days per week, Daily replacement Two weekly replacement Monthly replacement $0.00 $ $ $ $ $ professional fee lenses solutions $ $ $ Figure 1. Contribution of professional fee, lens costs and solution costs to the total annual cost of daily, two-weekly and monthly replacement spherical lenses worn seven days per week the situation is reversed, with daily replacement lenses having a higher costper-wear ($2.95 and $2.88, respectively) compared with two-weekly replacement lenses ($2.52 and $2.16, respectively) and monthly replacement lenses ($2.47 and $2.11, respectively). The cost-per-wear model as applied to toric lenses is generally similar to that for spherical lenses. For toric lenses (Figure 2B), the cost-per-wear of twoweekly replacement lenses is slightly higher than that for monthly replacement lenses irrespective of the number of times per week lenses are worn. For lenses worn one day per week, the cost-per-wear of daily replacement lenses ($7.56) is significantly lower than that of two-weekly and monthly replacement lenses ($16.46 and $15.86, respectively). As the number of days of wear per week increases, this difference decreases and between three and four days of wear per week there is virtually no difference in the cost-per-wear of the three lens replacement modalities (approximately $4.80). For lenses worn between four and seven days per week, the situation is reversed, with daily replacement lenses having a higher cost-per-wear (for example, $4.26 for seven days of wear $22.00 $20.00 Spherical lenses $22.00 $20.00 Toric lenses $22.00 $20.00 Multifocal lenses $18.00 $18.00 $18.00 Cost per wear $16.00 $14.00 $12.00 $10.00 $ Daily Two weekly... Monthly Cost per wear $16.00 $14.00 $12.00 $10.00 $ Daily Two weekly Monthly Cost per wear $16.00 $14.00 $12.00 $10.00 $ Daily Two weekly Monthly $6.00 $6.00 $6.00 $4.00 $4.00 $4.00 $2.00 $2.00 $2.00 $0.00 $ Days of wear per week Days of wear per week A B C $ Days of wear per week Figure 2. Cost-per-wear (AUD) for daily, two-weekly and monthly replacement lenses in relation to (A) spherical, (B) toric and (C) multifocal lenses Clinical and Experimental Optometry 93.4 July The Authors 256 Journal compilation 2010 Optometrists Association Australia

5 per week) versus two-weekly and monthly replacement lenses ($2.55 and $2.47 for seven days of wear per week, respectively). The cost-per-wear of two-weekly replacement multifocal lenses (Figure 2C) is appreciably higher than that for monthly replacement lenses irrespective of the number of times per week lenses are worn. For lenses worn one day per week, the cost-per-wear of daily replacement lenses ($7.04) is considerably lower than that of two-weekly lens replacement ($20.97). As the number of days of wear per week increases, this difference decreases and between four and five days of wear per week, there is no difference in the costper-wear of these two lens replacement modalities (approximately $5.00). For lenses worn between six and seven days per week, the situation is reversed, with daily replacement lenses having a higher cost-per-wear (for example, $4.87 for seven days of wear per week) versus twoweekly replacement lenses ($3.20 for seven days of wear per week). A similar pattern is observed when comparing the cost-per-wear of daily versus monthly replacement multifocal lenses. For lenses worn one day per week, the cost-per-wear of daily replacement lenses ($7.04) again is considerably lower than that of monthly lens replacement ($15.86). As the number of days of wear per week increases, this difference decreases and at three days of wear per week, the cost-per-wear of these two lens replacement modalities is about the same (approximately $5.50). For lenses worn between four and seven days per week, the situation is reversed, with daily replacement lenses having a higher cost-per-wear (for example, $4.87 for seven days of wear per week) versus monthly replacement lenses ($2.47 for seven days of wear per week). DISCUSSION Our search of the ophthalmic literature in the international bibliographic search engine PubMed, using the search terms contact lenses and cost, revealed 141 citations, however, none of these papers reported an analysis of the cost basis of contact lens wear. In the papers that were of relevance, cost was mentioned only in passing. Numerous reports have appeared in the medical literature addressing the impact of patient costs on the prescribing of drugs by medical practitioners, although the findings are inconsistent. In the USA, Pham, Alexander and O Malley 11 found that 78 per cent of physicians reported routinely considering cost factors when prescribing drugs; however, Shrank and colleagues 12 observed that only 20 per cent of physicians were usually or always aware of patient costs for medication. Physicians working in large group practices were more likely to consider patient expenditure when prescribing generic drugs compared with those working in solo and two-person practices. 11 Eye-care practitioners typically sell contact lenses directly to their patients and therefore, are obliged to consider the costs of lens wear, at least in a general fashion. This is a slightly different scenario from that faced by medical practitioners, who in Australia are not involved in the direct sale of medications to patients (this function is performed by pharmacists). Another key difference between prescriptions for medicines and contact lenses is that the former are often required to improve health, whereas the latter are typically optional and related to improved cosmesis. Nevertheless, prescribing decisions made by both medical and contact lens practitioners will impact the expenses incurred by a patient and in that way the analogy of modelling contact lens prescribing on medical drug prescribing generally holds. The cost-per-wear model described in this paper is illustrated using what are considered to be representative professional fees, and lens and solution costs, in Australia. The model is instructive in that it provides a rational basis for comparing the cost of different contact lens replacement frequencies. Practitioners may have different professional fees (for example, charging higher fees for more complex fittings), different lens and solution price structures and preferred product brands. Practitioners may also wish to consider the impact of different assumptions to those adopted here. Alternative cost-per-wear models can be constructed using the principles outlined in this paper to examine the impact of different cost inputs and assumptions that relate to their own practices. Although various forms of the cost-perwear model can be constructed, we believe that the model demonstrated here is unlikely to change significantly with different input values. Furthermore, we feel that this model is sufficiently robust to be applied to the cost of contact lens wear in different countries. The four major contact lens manufacturers operate globally and while region-specific factors such as local customs, the retail environment, styles of professional practice, professional fee structures, distribution costs, supply and demand issues, state and federal government taxes et cetera will influence the overall cost to patients, the relative costs of the different forms of lens wear are unlikely to vary. A key ramification of our model is the importance of considering the expected number of times a prospective patient wears lenses each week. This variable will have a significant impact on the relative cost and therefore the choice of lens replacement frequency. Part-time and full-time wear can arbitrarily be defined as wearing lenses one-to-three times per week and four-to-seven times per week, respectively. It is clear from our model that a daily replacement modality is more cost-effective for part-time lens wear. As the number of days the lenses are worn each week increases, the cost advantage progressively decreases and the cross-over point at which daily replacement lenses start to become more expensive than reusable lenses is between three and five days of lens wear per week, depending on the type of optical correction (spherical, toric or multifocal). The validity of the above analysis can be tested by examining the extent of prescribing the three lens replacement modalities, stratified according to the number of days lenses are worn each week. If cost is a primary driver of the choice of lens replacement frequency, it would be expected that daily replacement and reusable lenses are worn mainly for 2010 The Authors Clinical and Experimental Optometry 93.4 July 2010 Journal compilation 2010 Optometrists Association Australia 257

6 Proportion of lens fittings % daily replacement two weekly replacement monthly replacement part-time and full-time wear, respectively. In fact, an examination of the wearing frequency of 11,801 soft lens wearers in Australia 7 between 2000 and 2009 reveals this pattern (Figure 3). Sixty-six per cent of those wearing daily replacement lenses used their lenses on a part-time basis, versus only 17 and 10 per cent of those wearing two-weekly and monthly replacement lenses, respectively. As discussed in the Introduction, other factors that may be taken into consideration in the choice of lens replacement frequency are lens material and design. Notwithstanding the wide range of products available in all three replacement frequencies, 2 some material/design combinations deemed most suitable for a particular patient may not be available in a preferred replacement frequency. In addition, both practitioners and patients may be influenced by brand loyalty, and practitioners may wish to source lenses from a preferred manufacturer for reasons other than price, such as better supply logistics and professional support. Such considerations have not been taken into account in this analysis. An important factor that impinges on the affordability of a contact lens regimen Days of wear per week Figure 3. Proportion of patients fitted with daily, two-weekly and monthly replacement lenses stratified for number of days of wear per week and could significantly influence patient choice of lens replacement frequency is the degree of ametropia of the patient. For example, a contact lens patient with high myopia (say, above D) may prefer to wear contact lenses on most days to avoid the optical and cosmetic disadvantages of high-powered spectacle lenses. Therefore, such a patient does not really have the flexibility of opting for a compromise arrangement of purchasing daily replacement lenses (for increased convenience) but using them on a reduced number of days per week (to reduce the cost-per-wear). These considerations become more pronounced for the higher cost toric and multifocal prescription types. Constraints in parameter availability may also influence the choice of lens replacement frequency and indeed override cost considerations. For example, daily replacement toric lenses are generally available in a reduced range and number of cylindrical power/axis combinations compared with reusable toric lenses. 2 A patient with an astigmatic correction that falls outside the parameters available in daily replacement systems may be faced with an uneasy choice of: 1. A significant visual compromise resulting from an incomplete optical correction but with very convenient daily replacement lenses, or 2. A superior visual outcome with a full optical correction but with less convenient reusable lenses. The perceived or actual environmental impact of lens wear may also influence the choice that a patient makes with respect to lens replacement modality. Certainly, the environmental impact of contact lenses is an issue that is raised from time to time in the lay media. 13 Morgan, Morgan and Efron 14 have investigated this issue and found that, at the consumer level, the environmental impact of daily lens replacement is greater than that of monthly lens replacement. The overall magnitude of the environmental impact was found to be low for all lens types; the annual environmental impact of daily lens replacement was shown to be equivalent to discarding 33 cans (volume 330 ml) of Coca Cola (Coca-Cola Amatil [Aust] Pty Ltd, Sydney). This in turn represents about 0.5 per cent of the total environmental impact of an individual lens wearer in terms of the amount of domestic waste discarded each year. 14 Many contact lens wearers in Australia have some form of private health insurance cover which provides rebates for expenditure on lenses, thus allowing some of the costs relating to contact lens wear to be reimbursed. As well, some lens wearers with higher prescriptions are eligible for a substantial rebate of professional fees through Medicare (the Australian publicly-funded universal health care system). Although such factors are not taken into account in the cost-per-wear model presented here, practitioners can advise lens wearers of the reduction in outof-pocket expenses that is relevant to each specific case. A key assumption in this paper is that patients and practitioners are fully compliant with the lens replacement frequency recommended by manufacturers. Recent evidence from Dumbleton and associates 15 has revealed significant non-compliant behaviour in this regard. In anonymous practitioner and patient surveys of lens Clinical and Experimental Optometry 93.4 July The Authors 258 Journal compilation 2010 Optometrists Association Australia

7 replacement compliance in Canada, six, 34 and two per cent of practitioners recommended longer replacement frequencies than those suggested by the manufacturer for daily, two-weekly and monthly lens replacement, respectively. Non-compliance rates for properly advised (manufacturer recommended) replacement frequencies reported by patients for the three lens replacement modalities were 13, 50 and 33 per cent, respectively. Dumbleton and associates 15 observed similar levels of non-compliance in the USA. There is no reason to believe that noncompliance rates would be any different in Australia and practitioners are advised to consider potential non-compliance when interpreting the outputs of the cost-perwear model reported here. For example, if a patient is non-compliant by way of replacing lenses less frequently than recommended, the model, which assumes full compliance, will overestimate the cost-per-wear. The most frequent reason for noncompliance among daily replacement wearers cited in the report of Dumbleton and associates 15 was to save money (reported by 56 per cent of respondents), which highlights the importance of considering patient costs when prescribing contact lenses. Given the demonstration by Korn and co-workers 16 of the benefits of improving the awareness of practitioners of the impact of patient expenses on prescribing patterns in a medical context, we trust that the cost-per-wear analysis reported here will be of similar benefit to contact lens practitioners and lens wearers. CONCLUSIONS Patient costs need to be taken into account when prescribing medications or appliances. This principle certainly applies to the choice of a product like contact lenses, which for many users is a non-essential, albeit desirable, purchase. In this paper, we report a cost-per-wear model based on contact lens replacement frequency. The model reveals the cost implications of choosing the most appropriate form of optical correction (spherical, toric or multifocal lenses) with reference to the number of times the lenses are worn, or predicted to be worn, each week. The essential conclusion of this work is that daily replacement lenses are more cost-effective for part-time wear and reusable lenses are more cost-effective for full-time wear. Such cost considerations can be weighed against other clinical and non-clinical factors in arriving at the best contact lens option for the patient. REFERENCES 1. Maldonado-Codina C. Soft lens materials. In: Efron N, ed. Contact Lens Practice, 2nd ed. Oxford: Butterworth-Heinemann, p Product guide. Soft and RGP lenses and solutions. In: Oshry G, ed. Contact Lenses (Supplement to Australian Optometry). Carlton, Victoria, Australia: Optometrists Association Australia, p Efron N. Daily soft lens replacement. In: Efron N, ed. Contact Lens Practice, 2nd ed. Oxford: Butterworth-Heinemann, p Tanner J. Planned soft lens replacement. In: Efron N, ed. Contact Lens Practice, 2nd ed. Oxford: Butterworth-Heinemann; p Efron N. Contact Lens Complications, 2nd ed. Oxford: Butterworth-Heinemann, McCann M. Contact lenses. Eye Talk Reference Guide 2010; 30: Efron N, Morgan PB, Woods CA. Trends in Australian contact lens prescribing during the first decade of the 21st Century ( ). Clin Exp Optom. 2010; 93: McCann M. Consultations. Eye Talk Reference Guide 2010; 30: McCann M. Contact lens care products. Eye Talk Reference Guide 2010; 30: Complete Multi-Purpose Solution Easy Rub Formula. Important safety information [product advice on the internet]. Abbott Medical Optics. Available from: multi-purpose-solution/complete-multipurpose-solution-easy-rub-formula. Accessed on April 13, Pham HH, Alexander GC, O Malley AS. Physician consideration of patients out-ofpocket costs in making common clinical decisions. Arch Intern Med 2007; 167: Shrank WH, Asch SM, Joseph GJ, Young HN, Ettner SL, Kholodenko Y, Glassman P et al. Physicians perceived knowledge of and responsibility for managing patients out-of-pocket costs for prescription drugs. Ann Pharmacother 2006; 40: Rastogi NS. Glasses vs. contact lenses. An ophthalmic guide to saving the planet. Posted January 10, Available from: Accessed on April 13, Morgan SL, Morgan PB, Efron N. Environmental impact of three replacement modalities of soft contact lens wear. Contact Lens Ant Eye 2003; 26: Dumbleton K, Richter D, Woods C, Jones L, Fonn D. Compliance with contact lens replacement in Canada and the United States. Optom Vis Sci 2010; 87: Korn LM, Reichert S, Simon T, Halm EA. Improving physicians knowledge of the costs of common medications and willingness to consider costs when prescribing. J Gen Intern Med 2003; 18: Corresponding author: Professor Nathan Efron Institute of Health and Biomedical Innovation and School of Optometry Queensland University of Technology Brisbane QLD AUSTRALIA n.efron@qut.edu.au 2010 The Authors Clinical and Experimental Optometry 93.4 July 2010 Journal compilation 2010 Optometrists Association Australia 259

8 APPENDIX Sample calculations of cost-per-wear (CPW) for spherical lenses ($AUD) Abbreviations CPW d cost-per-wear for d days of lens wear per week PF professional fees ACL annual cost of lenses ACS annual cost of solutions 1. Daily replacement lenses A. Professional fees PF = per year B. Lenses 1 or 2 days per week: 1 box of 30 lenses = ACL = 24 boxes = to 7 days per week: box of 90 lenses = ACL = 8 boxes = C. Solutions ACS = 0.00 per year CPW d = (PF + (d ACL/7) + ACS)/(365 d/7) Therefore: CPW 1 = ( ( /7) )/(365 1/7) = 5.80 CPW 2 = ( ( /7) )/(365 2/7) = 4.35 CPW 3 = ( (3 900/7) )/(365 3/7) = 3.43 CPW 4 = ( (4 900/7) )/(365 4/7) = 3.19 CPW 5 = ( (5 900/7) )/(365 5/7) = 3.04 CPW 6 = ( (6 900/7) )/(365 6/7) = 2.95 CPW 7 = ( (7 900/7) )/(365 7/7) = Two-weekly replacement lenses A. Professional fees PF = per year B. Lenses Box of 6 lenses = ACL = 8 boxes = C. Solutions ACS as per Table 2 CPW d = (PF + ACL + ACS)/(365 d/7) Therefore: CPW 1 = ( )/(365 1/7) = CPW 2 = ( )/(365 2/7) = 7.28 CPW 3 = ( )/(365 3/7) = 4.85 CPW 4 = ( )/(365 4/7) = 3.74 CPW 5 = ( )/(365 5/7) = 3.02 CPW 6 = ( )/(365 6/7) = 2.52 CPW 7 = ( )/(365 7/7) = Monthly replacement lenses A. Professional fees PF = per year B. Lenses Box of 3 lenses = ACL = 8 boxes = C. Solutions ACS as per Table 2 CPW d = (PF + ACL + ACS)/(365 d/7) Therefore: CPW 1 = ( )/(365 1/7) = CPW 2 = ( )/(365 2/7) = 7.12 CPW 3 = ( )/(365 3/7) = 4.74 CPW 4 = ( )/(365 4/7) = 3.66 CPW 5 = ( )/(365 5/7) = 2.96 CPW 6 = ( )/(365 6/7) = 2.47 CPW 7 = ( )/(365 7/7) = 2.11 Clinical and Experimental Optometry 93.4 July The Authors 260 Journal compilation 2010 Optometrists Association Australia