Correcting near and intermediate vision continues to be the greatest fitting challenge for ECPs. Power profile mapping can help provide insight into fitting aspheric multifocal contact lenses and guide the ECP toward selecting the best lens design for the patient.
Worldwide, eye care professionals (ECPs) do not dispute that the presbyopic patient population is growing. This population of patients, which generally presents in their early to mid-40s and older, has greater vision challenges: they need simultaneous correction for near, intermediate, and distance vision. Nearly 70 per cent of the world’s population requires some vision correction by the time they are in their mid-40s.1
While some patients may have worn contact lenses at younger ages, there is an increased dropout rate from contact lenses after 45 years of age, despite an increased interest in contacts and increased need for vision correction.1 As the presbyopic population increases, so too does the need for ECPs to understand advances in lens optics and their patients’ ever-changing vision needs.
Life Activities and Changing Vision Needs
A recent web study, completed by 404 patients in the United States (US) and 301 patients in France, examined ECP and patient experiences with presbyopia in order to better understand this population’s vision needs.2 The survey, while assessing the patient’s daily vision needs, asked about lens use satisfaction, as well as the frequency and impact of symptoms experienced with contact lens use.
Approximately three in 10 presbyopes are never successfully
fitted for lenses
When patients were asked to rate their overall satisfaction by lens attributes, the primary area of dissatisfaction for multifocal and monovision wearers was near vision. The survey also asked these patients about their ‘real-world’ vision needs. While all vision categories (near, intermediate, and distance vision) were listed as visual priorities while working, near vision was listed as the most important issue for all lens wearers at work. This is not surprising, given that many contact lens wearers spend the majority of their work day using a computer (Figure 1).3
A total of 75 US ECPs and 75 French ECPs were asked to complete a survey that discussed the challenges and success rates of fitting presbyopic patients.2 Eye care professionals agreed that correcting distance vision is the least challenging in both the US and France. However, correcting near vision in the US and correcting mid-range vision in France were listed as the greatest challenge for each respective country (Figure 2).
When asked about the number of visits it takes to successfully fit a presbyopic patient, all ECPs indicated that, on average, four in 10 patients are not fitted successfully in the first or second visit. Additionally, ECPs estimated that about three in 10 presbyopes are never successfully fitted with lenses. This makes the fitting process frustrating for patients and ECPs alike.
Comparing Lens Designs
While the above studies did not examine fitting success rates of specific lens brands, an earlier study evaluated the power profiles of two popular multifocal (MF) contact lens brands by looking at the similarities and differences between designs using a new generation high resolution Hartmann-Shack wavefront sensor.4,5 The study compared -3.00D PureVision MF (low and high add) lenses and -3.00D Air Optix Aqua MF (low, medium, and high add) lenses. Measurements were also taken on -3.00D single vision sphere PureVision and Air Optix Aqua lenses. Each of the multifocal and single vision sphere lens designs were measured three times from the centre out to a 3mm radial distance.
The median power of the three measurements was then plotted to create power profiles that could help explain on-eye performance of these lenses (Figures 3 and 4).
Both PureVision MF and Air Optix Aqua MF lenses use aspheric (negative spherical aberration) optical designs to create a centre-near add. However, the PureVision MF has two different add power designs, while Air Optix Aqua uses an additional add power design. The question the study asked was, does the additional add power design provide additional benefit?
Measurements from the power profiles of the PureVision MF lenses demonstrated two distinct, differentiable power profiles (Figure 3). The PureVision MF low add lens measured more than twice the add power provided by the Air Optix Aqua low add MF lens: an estimated add of +0.59D for the PureVision MF lens compared to an estimated add of only +0.25D for the Air Optix Aqua MF lens. Additionally, the PureVision MF high add lens measurements showed a greater amount of add than either the Air Optix Aqua medium or high add lenses: an estimated add of +1.84D compared to +1.31D and +1.41D for the Air Optix Aqua MF medium and high add lenses, respectively.
Figure 4 shows the power profiles for the three Air Optix Aqua multifocal designs and the Air Optix single vision lens. Because of the similar power profiles, ECPs may find it difficult to discriminate between the Air Optix Aqua medium and high add powers clinically, and may struggle to find an adequate solution as the patient’s greater add power needs develop with age. PureVision MF provides more add power to help address the changing needs of the presbyopic wearer.5
Summary
Due to the differing distance, intermediate, and near vision needs of the presbyopic population, this patient group is challenging to fit. Correcting near and intermediate vision continues to be the greatest fitting challenge for ECPs. Near and intermediate vision demands also provide the greatest area of disappointment for patients in a world of increased near and intermediate visual needs, especially from numerous hours spent on computers and smart phones each day.
The fitting process, which typically takes an average of 2.6 fittings to successfully fit a patient with contact lenses, can be frustrating for patients and ECPs alike. This results in even more frustration when considering that approximately three in 10 presbyopes are never successfully fitted for lenses.
Power profile mapping can help provide insight into fitting aspheric multifocal contact lenses. Knowledge of the lens power profile can guide the ECP toward selecting the best lens design for the patient. The power profiles of the three Air Optix Aqua MF contact lenses and the two PureVision MF lenses tested showed that there are effectively only two distinct add powers for each of the lens brands. However, PureVision MF demonstrated that these lenses provide more add power than the three Air Optix Aqua MF contact lenses to help address the changing needs of the presbyopic wearer.
Alexis KS Vogt, PhD is an Optical Physicist for Bausch + Lomb. She was invited to join the Lens Design department in January 2008 where her primary duties involved designing and developing innovative contact lenses and leading the contact lens competitive analysis project. In 2012 Alexis joined the Medical Affairs group to provide contact lens technical support for Professional Relations colleagues worldwide and to communicate through presentations and publications the design features and patient benefits of Bausch + Lomb contact lenses.
Siva Raj – Director, New Product Insights – Strategic Knowledge & Insights, Bausch + Lomb. Siva has over 17 years of global experience in helping organisations in healthcare and other industries build better products by targeting unmet customer needs.
References:
1. Source: Multi-sponsor Surveys’ 2010 WW Consumer Contact Lens Market Study Interviews conducted in Western Europe, Sweden, Russia, China, India, Hong Kong, Taiwan, Singapore, South Korea, Thailand, Malaysia, Australia and the U.S.
2. Market research: Kadence International. July 2012.
3. Exploring blurry, changing or fluctuating vision associated with contact lens wear. Kadence International. January 2012.
4. Vogt, A.K.S., et al., Using power profiles to evaluate aspheric lenses. CL Spectrum, 2011(January).
5. Vogt, A.K.S., et al., Distribution of power. Optician, 2010(February).
