Modern contact lenses are available in a variety of designs and modalities to aid vision correction in wearers of all ages.
Successful outcomes when fitting single vision soft lenses are typically straightforward.
However, multifocal (MF) lenses can be more challenging, and a variety of factors, including patient lifestyle and expectations, should be assessed before fitting.
The unique designs of MF soft lenses vary greatly between manufacturers and to determine the optimal lens, more than one design is often required during the fitting process.1-3
Professional Belief Survey Results
A recent survey of 1,028 eye care professionals (ECPs), conducted from 2021 to 2022 across multiple countries, showed that 36% agreed with the statement that ‘Lens fitting recommendations for soft multifocal lenses are the same across manufacturers’ fit guides’ (figure 1).4
This mismatch between opinion and the reality that the unique designs require different approaches to fit them appropriately highlights the importance of following the respective fitting guides, some of which are available for use as phone-based apps or web-applications, in addition to hard copy versions.
Figure 1: Results showing how far respondents agreed that initial lens selection and vision optimisation recommendations for soft multifocal fitting are the same across manufacturers’ fit guides. Data is from 2022 except Russia, which is from 2021
What the Evidence Shows
Regardless of manufacturer, the first step for any MF soft lens fit is to begin with an up-to-date refraction, ensuring that plus in the prescription is maximised.
Most fitting guides recommend fitting spherical MF lenses to eyes with no more than 0.75 or 1.00D of astigmatism. The prescription is then converted to a vertex-corrected spherical equivalent. MF fitting guides across manufacturers typically suggest that ocular dominance should be determined by the sensory or blur test, using either +1.00D or +1.50D lenses.
The preferred sighting method is not recommended as a first choice. General guidelines for initial lens selection include using the spherical equivalent for distance power.
However, selection of the near add varies across lens types; some manufacturers suggest using the same near add as the spectacle refraction binocularly or measuring and selecting a more ‘functional’ add while others lean towards an approach of fitting different near adds dependent on ocular dominance.
Adhering to the appropriate fitting guides make this choice simple to follow. Subsequent optimisation of distance and near vision is often approached by performing an over-refraction on the dominant or non-dominant eyes, however, some manufacturers clearly specify no over-refraction.
Depending on the fitting guide, changes to near adds are only recommended for certain MF lenses, while other manufacturers recommend modifying distance power only.
The variation in lens parameters between different manufacturers’ fitting guides is shown for the same patient in table 1.
Table 1: Examples of initial lens power selection for the same spectacle Rx from a sample of different MF soft lens fitting guides
Conclusion
Fitting guides are created based on the optical design of each manufacturer and the knowledge that they gain during their development of a MF lens design and extensive assessment through clinical studies that take place before the lens is approved for use.
Their goal is to maximise fitting success, to reduce chair time and create confidence in the product. The ocular dominance test plays an important role in the fitting process.
In the above-mentioned survey,4 61% of eye care practitioners on average across all countries surveyed stated that they used the preferred sighting method. However, fitting guides typically specify the blur test with a +1.00 or +1.50D lens.
The sighting method forces patients to choose between their two eyes when focusing on a target, while the sensory method (blur test) has the advantage of simulating what occurs when disparity occurs in a binocular situation and thus determining which eye has the greatest sensitivity to plus defocus.5
In certain cases, some patients may be satisfied with their vision even though a different fitting approach to manufacturers’ guidelines is used. It is also possible that practitioners who follow the fitting guidelines and cannot get satisfactory results may then go on to choose different methods.
Despite these points, the vast majority of patients are likely to benefit if manufacturer guidelines are followed by their eye care practitioners when fitting soft multifocal contact lenses.
- Dr Doerte Luensmann is a senior clinical scientist at the Centre for Ocular Research & Education, School of Optometry & Vision Science, University of Waterloo. John Meyler is head of global professional education for Johnson & Johnson Medical Ltd.
References
1 Moody K, Hickson-Curran S, Ben Wooley B and Ruston D. Innovating for multifocal fitting success. Optician. 05/07/2015.
2 Lazon de la Jara P, Sulley A. Novel multifocal CLs for presbyopia. Optician. 03/12/2021.
3 Bauman E. Material effect on multifocal contact lens fitting of lenses of the same optical design with the same fitting guide. Contact Lens and Anterior Eye. 2018;41:S60.
4 Johnson & Johnson Vision Care. Online survey of 1028 Eye Care Professionals across United States, United Kingdom, Russia, China, Japan, and South Korea. JJV data on file. 2021 (Russia) and 2022 (other markets).
5 Pointer JS. Sighting versus sensory ocular dominance. J Optom. 2012 Apr;5(2):52-55. doi:10.1016/j.optom.2012. 03.001