Rigid contact lenses have been used to correct refractive error since the first reported fitting of this type of optical device to a human eye in 1888.1 For the next 60 years of contact lens fitting, only large-diameter scleral lenses were fitted.2 These were originally made from glass, but polymethyl methacrylate (PMMA) began to be used after being invented in the 1930s. Small-diameter corneal lenses were introduced in the 1950s, and lenses were made from gas-permeable plastics in the 1970s.2
A major change in contact lens technology occurred in the early 1970s with the introduction of soft hydrogel contact lenses.2 Soft lenses now dominate the contact lens market and are available in a wide variety of materials, designs, replacement frequencies, and wearing modalities.3 Although rigid lenses are still fitted today, they are prescribed more for specialty purposes, being primarily used for the correction of optically challenging conditions, such as keratoconus, corneal distortion, and after refractive surgery, and for orthokeratology.
Although it is clear that rigid lenses are no longer the mainstay of contact lens fitting, little is known of the true extent to which these lenses are fitted around the world. Such information can provide a valuable yardstick for contact lens clinicians against which they can assess their own prescribing practices. Here we examine trends in rigid contact lens fitting during a 16-year period (1996 to 2011) and undertake a detailed analysis of contemporary worldwide fitting of this lens type (2007 to 2011).
Conduct of the Annual Survey
Between January and March each year from 2007 to 2011, a contact lens fitting survey was undertaken in 40 countries. This was achieved through the offices of members of the International Contact Lens Prescribing Survey Consortium, which is a network of academics, industry representatives, and clinical colleagues who have agreed to manage the survey in their country or geographic region, as outlined below.
We requested that consortium members send a paper or electronic (e-mail) survey form to as many contact lens practitioners (opticians, optometrists, and/or ophthalmologists, depending on the market) in their country as possible, with a notional target of 1000 surveys sent. Some smaller countries were unable to reach this target because of the limited number of practitioners in that region.
In some countries, such as Australia, survey forms were sent to virtually every practitioner in the country (almost 4000 practitioners). In other countries, survey forms were sent to a selection of practitioners throughout the country; this process varied among countries, ranging for example from a computer-generated random list of exactly 1000 recipients from the national practitioner register in the United Kingdom to a list of practitioner-subscribers to contact lens trade publications in the United States and Russia. In large countries with dispersed populations, such as China and Russia, survey forms were sent to practitioners in a select number of major urban cities. The survey forms were sent together with a request that they be completed and returned within 3 months of receipt. To minimize any possible impact of the annual business activity cycle on the types of lenses fit, the survey was conducted in the first few months of each year in all countries.
The same survey format was used each year, as published previously.4 This survey was a single-page form, on which practitioners were requested to enter a number of background details and to supply generic information about the first 10 contact lens fits performed after receipt of the survey form. For each contact lens fitting, practitioners were requested to complete the following details: date of fitting, new fitting or refitting, age and sex of patient, lens material, lens design, frequency of lens replacement, times per week of lens wear, wearing modality (daily or extended wear), and care system.4 Practitioners were asked to return the form irrespective of the number of patients seen (if fewer than 10). The returned forms were logged, and data from each form were manually entered into an Excel (Microsoft Corporation, Redmond, Wash) spreadsheet to facilitate data analysis.
Although this article reports a detailed analysis of survey data collected between 2007 and 2011, we have been collecting information on rigid lens fitting every year since 1996, initially in the United Kingdom (1996 to 1999) and then gradually increasing the number of countries surveyed since 2000. To illustrate trends in rigid lens prescribing between 1996 and 2011, the proportion of rigid lenses prescribed in seven countries during this period was determined.
The Office of Research Ethics at the University of Waterloo, Canada, granted approval for this work, and noted that, as the data being collected were (1) part of normal practice care provision, (2) transcribed from the practice patient records, and (3) deidentified in respect of the patients, then the requirement for patient informed consent was waived.
Differences among practitioners in relation to the amount of contact lens fitting performed were taken into account by assigning an appropriate weighting to each recorded contact lens fit. This was achieved by estimating the number of contact lens fits performed each year by each respondent (based on the date information provided on the survey form) and using this as a weighting factor. For example, the data generated by a practitioner completing all 10 fits in 1 week were given twice the weighting of a practitioner who fitted 10 patients in 2 weeks. Data were mined with the aid of the Excel Pivot Table function. Statistical analysis of differences was conducted using logistic regression models (JMP, SAS Institute Inc., Cary, NC) for rigid lens fits.
During the 5-year survey period (2007 to 2011), data about lens modality were collected in relation to 12,230 rigid lens fits. Data were also collected for 100,670 soft lens fits; these data were used in this study for comparison purposes. The median country response rate was 1345 fits (range, 59 fits in Nepal to 22,802 fits in Japan).
Rigid lenses represented 10.8% of all contact lens fits; however, there was considerable variance in rigid lens fitting among the 40 countries surveyed, ranging from 0.2% in Lithuania to 37% in Malaysia (Fig. 1).
The mean age (±SD) of those fitted with rigid lenses (37.3 ± 15.0 years) was greater than that for soft lenses (29.8 ± 12.4 years) (χ2 = 78.4, p < 0.0001). Males represented 36% of all those wearing rigid lenses versus 32% of those wearing soft lenses; this difference was not significant (χ2 = 2.54, p = 0.11).
The proportion of spherical, toric, presbyopic, orthokeratology, and other designs used for rigid and soft lens fits is shown in Fig. 2. The distributions of designs used for these two modalities of wear were significantly different (χ2 = 701.9, p < 0.0001). As can be seen from Fig. 2, compared with soft lens fits, less rigid lenses with spherical and toric designs, and more presbyopic designs, are fitted. Orthokeratology designs represented 11.5% of rigid lens fits and 1.9% of all contact lens fits, ranging from 7.5% of all contact lens fits in Hong Kong to “no recorded fits” in 12 countries (Fig. 3).
Fig. 4 displays the proportion of rigid lens fits according to material type and overall lens form. For the purposes of this survey, contact lens oxygen permeability (Dk) values were categorized as low Dk (<40 × 10-9 cm mL O2/s mL mm Hg), mid-Dk (40 to 90 × 10-9 cm mL O2/s mL mm Hg), and high Dk (>90 × 10-9 cm mL O2/s mL mm Hg). Fig. 4 reveals that most rigid lenses were fabricated from high-Dk (36%) or mid-Dk (42%) materials. Scleral and PMMA lenses represented only a small minority of rigid lens fits (1.6% and 1.2%, respectively).
Whereas 85% of soft lenses were replaced regularly (daily, 1 to 2 weekly, or monthly), only 7% of rigid lenses were regularly replaced (lenses replaced on a planned basis of any frequency) (χ2 = 8115.3, p < 0.0001). There was no difference between rigid and soft lenses with respect to the extent of extended wear prescribing (χ2 = 0.26, p = 0.61), with extended wear representing 8% of both rigid and soft lens fits. Most rigid lens extended wear fits (51%) were for orthokeratology.
We arbitrarily define “part time” and “full time” as wearing lenses one to three times per week and four to seven times per week, respectively. Four percent of rigid lenses were fitted for part time wear versus 10% of soft lenses (χ2 = 206.3, p < 0.0001).
The trend in rigid lens fitting in all countries surveyed between 1996 and 2011 is displayed in Fig. 5. As is clear from inspection of this figure, there was a general decline in rigid lens fitting during the course of this survey period.
Differences in the extent of rigid lens prescribing between nations may be attributed to international differences in the training, attitudes, and collective confidence of the predominant practitioner groups—opticians, optometrists, and ophthalmologists. For example, ophthalmologists, who largely or exclusively manage serious contact lens–related eye infections in many regions of the world, may harbor more conservative attitudes and concerns relating to the ocular health risks of soft lenses in general and for this reason may prefer to prescribe rigid lenses, which are known to be associated with a lower rate of vision-threatening microbial keratitis.5–8
The much higher age at which people are fitted with rigid lenses is perhaps a reflection of the overall trend of a reduction in rigid lens fitting over time (see below for discussion of rigid lens fitting trends). That is, those being fitted with rigid lenses are largely existing (and thus older) wearers who have happily adapted to this lens type and see no reason to change to soft lenses.
The analysis of rigid lens fits according to lens design highlights the trend toward rigid lenses being fitted for specialist applications. This is evidenced by the higher rate of fittings for presbyopia with rigid lenses; certain presbyopic fitting strategies, such as translating bifocal designs, can only be achieved with rigid lenses.9 As well, only rigid lenses can induce sufficient changes in corneal topography to induce a meaningful shift in refraction, which is the essential requirement of orthokeratology.10 International differences in the extent of orthokeratology fitting are probably impacted to a large extent by the enthusiastic endorsement of local practitioners or societies and access of local laboratories prepared to supply this highly specialized form of lens.
A significant proportion of rigid lens designs (7.3%) were designated as “other”; however, there was no facility on the survey form to indicate the specific type of “other” lens design fitted. These may have been one of a growing variety of innovative specialized rigid lens designs that have become available in recent years, such as intralimbal lenses, piggyback, and hybrid lenses.11
The proven ocular health benefits of higher Dk materials in both soft and rigid lens domains12,13 explain the predominance of mid- to high-Dk rigid lens prescribing. Rigid lenses are now rarely made from oxygen-impermeable PMMA.
Scleral lenses, which today are mainly used for advanced keratoconus and medical and cosmetic restoration reasons,14 still represent only a small proportion (1.6%) of rigid lens fits. Although our survey form did not distinguish between scleral lens types, it is likely that these scleral lens fits were of a variety of forms, including corneo-scleral, semi-scleral, mini-scleral, and conventional scleral designs.15 The wide variety of scleral lens types now available offers more scope for specialist contact lens fitting and may lead to increased prescribing within this niche sector.
Rigid contact lenses, by definition, have a high modulus of elasticity and are thus more durable and resistant to physical damage and deformation. Indeed, such lenses have been shown to have a longer natural “life expectancy” than soft lenses.16 Therefore, from a material integrity standpoint, rigid lenses do not need to be replaced as regularly as soft lenses. However, deposits may build up on the surface of rigid lenses,17 and for this reason, regular replacement is advisable.18 Because of the relatively high cost involved in the manual manufacture (lathing and polishing) of rigid contact lenses,19 the unit cost of rigid lenses is considerably higher than that of soft lenses, making regular rigid lens replacement prohibitive. This largely explains why only 7% of rigid lenses are regularly replaced compared with 85% of soft lenses.
Rigid lenses are fitted for extended wear to the same extent as soft lenses but apparently for different reasons. The primary reason for extended wear rigid lens fitting is overnight orthokeratology,10 whereas with soft lenses, extended wear is fitted as a modality that confers increased wearer convenience.
The staged physiological adaptation required for comfortable rigid lens wear20 largely precludes the fitting of this lens type on a part-time basis. Conversely, current-generation soft lenses essentially require no adaptation and can be worn all day from the first wearing occasion.21 This explains why only 4% of rigid lenses were fitted for part-time wear compared with 10% of soft lenses.
Decline in Rigid Lens Fitting Over Time
The extent of rigid lens fitting seems to have been in decline during the past 16 years of this survey. The reasons for this decline are complex, and a full discussion of the various factors involved is beyond the scope of this article. By way of summarizing these issues, Efron22 has cited 10 reasons for the gradual decline in rigid lens fitting: initial rigid lens discomfort; intractable rigid lens–induced corneal pathology (3 and 9 o’clock staining) and lid pathology (ptosis); extensive soft lens advertising; superior soft lens fitting logistics; lack of rigid lens training opportunities; redundancy of the rigid lens “problem solver” function; improved soft toric and bifocal/varifocal lenses; limited uptake of orthokeratology; lack of investment in rigid lenses; and the emergence of aberration control soft lenses.
Although rigid lenses are generally no longer considered as the “first choice” option when fitting contact lenses for cosmetic reasons, the results of this survey confirm that this lens category still has a limited specialist role in refractive correction. Notwithstanding the considerable variance across nations, rigid lenses overall currently represent 10.8% of all contact lenses fitted. Some practitioners still prefer fitting, and patients prefer wearing, rigid lenses because of their physical resilience and stable surface characteristics. As well, the unique optical and physical requirements of contact lenses to achieve good vision in challenging situations such as keratoconus and adequate refractive change with orthokeratology necessitate the fitting of rigid lenses. For these reasons, it is likely that the decline in rigid lens fitting will asymptote toward, but not reach, the “zero fitting” baseline and will remain as a viable, albeit increasingly specialized, form of vision correction.
Institute of Health and Biomedical Innovation
and School of Optometry
Queensland University of Technology
Kelvin Grove Queensland 4059
Members of the International Contact Lens Prescribing Survey Consortium
Philip B. Morgan, United Kingdom; Nathan Efron, Australia; Craig A. Woods, Australia; Suresh Awasthi, Nepal; Vadim Belousov, Russia; Jolanta Bendoriene, Lithuania; Aris Chandrinos, Greece; Prema Chane, India; Byoung Sun Chu, South Korea; Edgar Davila-Garcia, Puerto Rico; Nir Erdinest, Israel; Philip Fine, Israel; José Manuel González-Méijome, Portugal; Hans-Jürgen Grein, Germany; Christina N. Grupcheva, Bulgaria; Jorgen Gustafsson, Sweden; Magne Helland, Norway; Hreinn Ingi Hreinsson, Iceland; John Hsiao, Taiwan; Motozumi Itoi, Japan; Oskar Johansson, Sweden; Deborah Jones, Canada; Razmig Knajian, United Arab Emirates; Wanda Lam, New Zealand; Carla J. Mack, United States of America; Florence Malet, France; Edoardo Marani, Italy; Sebastian Marx, Germany; Giancarlo Montani, Italy; Jason J. Nichols, United States of America; Alice Pesinova, The Czech Republic; Geraint Phillips, New Zealand; Simona Radu, Romania; Ole Ravn, Denmark; Svend-Erik Runberg, Denmark; Jacinto Santodomingo, Spain; Mirna S. Silih, Slovenia; Kah-Ooi Tan, China; Ioannis G. Tranoudis, Greece; Eef van der Worp, The Netherlands; Mihály Végh, Hungary; Edit Vodnyanszky, Hungary
Received July 27, 2012; accepted October 10, 2012.
1. Efron N, Pearson RM. Centenary celebration of Fick’s Eine Contactbrille. Arch Ophthalmol 1988; 106: 1370–7 [erratum published in Arch Ophthalmol 1989;107:28].
2. Efron N. Historical perspective. In: Efron N, ed. Contact Lens Practice, 2nd ed. Oxford, UK: Butterworth-Heinemann; 2010: 3–9.
3. Kerr C, Ruston D. The ACLM Contact Lens Year Book 2012. Devizes, Wiltshire, UK: The Association of Contact Lens Manufacturers; 2012.
4. Morgan PB, Efron N. A decade of contact lens prescribing trends in the United Kingdom (1996–2005). Cont Lens Anterior Eye 2006; 29: 59–68.
5. Schein OD, Glynn RJ, Poggio EC, Seddon JM, Kenyon KR. The relative risk of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses. A case-control study. Microbial Keratitis Study Group. N Engl J Med 1989; 321: 773–8.
6. Poggio EC, Glynn RJ, Schein OD, Seddon JM, Shannon MJ, Scardino VA, Kenyon KR. The incidence of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses. N Engl J Med 1989; 321: 779–83.
7. Morgan PB, Efron N, Hill EA, Raynor MK, Whiting MA, Tullo AB. Incidence of keratitis of varying severity among contact lens wearers. Br J Ophthalmol 2005; 89: 430–6.
8. Stapleton F, Keay L, Edwards K, Naduvilath T, Dart JK, Brian G, Holden BA. The incidence of contact lens–related microbial keratitis in Australia. Ophthalmology 2008; 115: 1655–62.
9. Meyler J. Presbyopia. In: Efron N, ed. Contact Lens Practice, 2nd ed. Oxford, UK: Butterworth-Heinemann; 2010: 252–65.
10. Carney LG. Orthokeratology. In: Efron N, ed. Contact Lens Practice, 2nd ed. Oxford, UK: Butterworth-Heinemann; 2010: 332–8.
11. Barnett M, Mannis MJ. Contact lenses in the management of keratoconus. Cornea 2011; 30: 1510–6.
12. Covey M, Sweeney DF, Terry R, Sankaridurg PR, Holden BA. Hypoxic effects on the anterior eye of high-Dk soft contact lens wearers are negligible. Optom Vis Sci 2001; 78: 95–9.
13. Maldonado-Codina C, Morgan PB, Schnider CM, Efron N. Short-term physiologic response in neophyte subjects fitted with hydrogel and silicone hydrogel contact lenses. Optom Vis Sci 2004; 81: 911–21.
14. Pullum KW. Scleral lenses. In: Efron N, ed. Contact Lens Practice, 2nd ed. Oxford, UK: Butterworth-Heinemann; 2010: 233–42.
16. Jones L, Woods CA, Efron N. Life expectancy of rigid gas permeable and high water content contact lenses. CLAO J 1996; 22: 258–61.
17. Bontempo AR, Rapp J. Lipid deposits on hydrophilic and rigid gas permeable contact lenses. CLAO J 1994; 20: 242–5.
18. Woods CA, Efron N. Regular replacement of extended wear rigid gas permeable contact lenses. CLAO J 1996; 22: 172–8.
19. Efron N, Newman S. Rigid lens manufacture. In: Efron N, ed. Contact Lens Practice, 2nd ed. Oxford, UK: Butterworth-Heinemann; 2010: 154–61.
20. Young G. Rigid lens design and fitting. In: Efron N, ed. Contact Lens Practice, 2nd ed. Oxford, UK: Butterworth-Heinemann; 2010: 176–89.
21. Young G. Soft lens design and fitting. In: Efron N, ed. Contact Lens Practice, 2nd ed. Oxford, UK: Butterworth-Heinemann; 2010: 109–18.
22. Efron N. Obituary—rigid contact lenses. Cont Lens Anterior Eye 2010; 33: 245–52.