EVEN AMONG INDIVIDUALS performing the same visual task, such as using a computer or reading a book, there is considerable variation in pupil size (Cardona and López, 2016). This can have a significant impact on the performance of multifocal contact lenses (MFCLs) that utilize simultaneous vision designs, as the refractive power profile across a lens from the center to the periphery changes (Papadatou et al, 2017). As pupil size varies, the proportion of the lens surface the eye experiences dedicated to distance, intermediate, and near vision theoretically changes, impacting performance (Papadatou et al, 2017).

Across multiple studies, MFCLs are reported to be the same as or insignificantly worse than single vision lenses when measuring high-contrast distance visual acuity across pupil sizes from 3 mm to 6 mm (Dolce et al, 2025; Phatak et al, 2025). Acuity decrease, if any, is considered a few letters, less than a line at most in some studies, and so is reported to be clinically insignificant (Dolce et al, 2025; Phatak et al, 2025).

Indeed, when comparing 4 multifocal contact lenses at distance, intermediate, and near under different lighting conditions with high-contrast targets in 1 study, there was reportedly no association between pupil size and visual acuity among participants (Martinez-Plaza et al, 2026). However, using measures other than high-contrast acuity shows a different picture.

In a different study, a 2-line difference between a 3-mm and 6-mm pupil when wearing MFCLs has been reported when acuity is measured using a low-contrast, rather than a high-contrast, chart (Dolce et al, 2025). Measuring multiple spatial frequencies also highlights the impact of MFCLs on visual performance. While there is no difference in the contrast sensitivity function (CSF) between 3-mm and 6-mm pupils when wearing single vision lenses, there is up to a 17% decrease in the area under the log CSF curve with the 6-mm pupil, indicating that there is likely a clinically meaningful impact of wearing these lenses when the pupil is large (Dolce et al, 2025). The explanation is that the higher-order aberrations incorporated into multifocal lenses have a greater impact on the CSF when the pupil is larger. As the pupil size decreases, vision/CSF is more diffraction limited and aberrations are less impactful (Dolce et al, 2025).

Visual satisfaction with MFCLs appears to be associated with pupillary dynamics—the greater ability to change pupil size under different lighting conditions, which can be measured by comparing mesopic and photopic pupil sizes (Martinez-Plaza et al, 2026). In this study, the lack of a relationship found between high-contrast visual acuity and visual satisfaction suggests that other measures may be more useful in predicting MFCL acceptance (Martinez-Plaza et al, 2026). Pupils that are able to react to a greater degree under different lighting conditions may be able to benefit more from the multifocal optics of the lenses (Martinez-Plaza et al, 2026).

Manipulation of the pupil through the use of tints or neutral density filters have also been investigated (Park et al, 2020). Incorporation of tints has been shown to lead to enlargement of pupils, allowing for more of the distance optics to be experienced with center-near MFCL designs (Park et al, 2020). Unfortunately, this is not coupled with an increase in distance visual acuity. In fact, if light transmission is decreased to below 50%, distance visual acuity decreases (Park et al, 2020).

Numerous factors affect the performance and ultimately the acceptance of MFCLs. Pupil size is one such factor, and further developments may provide insight into how its measurement can be used to optimize MFCL use.

Acknowledgments: The author would like to thank Lily Ho at UNSW Sydney for her support and feedback on this article.

References

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