March 9, 2026
By Kevin Chan, OD, MS, FAAO, IACMM
Optical ‘Defocus’ and Pupillary Dynamics – Clinical Background
Photo Credit: Getty Images
For years, the premise of peripheral hyperopic defocus has emerged as a plausible mechanism that promotes axial elongation and, thus, myopia development. For that, myopic defocus theory has been explored, and extensive research has shown that it can slow or halt axial growth.
The notion of “defocus,” however, isn’t always to make objects out-of-focus on the retina. Indeed, it can actually be a misnomer that has commonly been used and oversimplified in clinical literature. To enable the effects of optical defocus on the eye, pupil size plays an important, yet also underestimated, role in tandem. In other words, pupillary dynamics is directly associated with the optical defocus profile and modulation.
In the latest development of myopia control spectacles, peripheral defocus modulation is hypothesized not only affected by each specific spectacle lens design, but it can also be influenced by pupillary dynamic activities. This likely results in various distributions and amounts of peripheral light reaching the retina.
In this exploratory research by Jinghua Zhu et al., the authors aimed to unfold the relationship between pupillary characteristics and clinical effectiveness of various myopia control spectacles.
Key Objectives
- Does pupil area influence the degree of myopia control achieved with peripheral defocus lenses?
- Can pupillary dynamics serve as a predictive biomarker for treatment outcomes in clinical practice?
- How to identify and bridge the gaps in understanding the key physiological determinants of myopia control efficacy.
Methodology
- Retrospective study of 310 children aged 7 to 14 years with low-to-moderate myopia at Aier Eye Hospital, Shenzhen, China between July 2021 and December 2024
- A total of three lens types were analyzed.
- Inclusion criteria, including age, gender, pupil area, spherical equivalent refractive (SER) error of <-6.00D and astigmatism <-1.50D, axial length (AL) and type of spectacle lens worn.
- Exclusion criteria:
- Corneal pathology, ocular inflammation, cataract, glaucoma, fundus abnormalities, or media opacity
- History of amblyopia, strabismus, nystagmus, or poor fixation
- History of systemic diseases
- History of prior myopia control interventions within 6 months before lens fitting
- Primary endpoints: 1) axial length and 2) refractive error changes
- Multivariate regression analyses were used to evaluate the relationship between baseline pupil area and treatment efficacy. Potential confounders such as age, baseline refraction and compliance were identified and adjusted.
Results
- A total of 310 participants were enrolled, 150 of which were with lens type A (48.4%), 82 with lens type B (26.5%) and 78 with lens type C (25.2%).
- A robust association was found between larger pupil area and enhanced efficacy of peripheral defocus spectacle lenses in controlling myopic progression.
- Children with greater baseline pupil areas exhibited reduced axial elongation and slower increases in myopic refractive error with statistical significance compared to those with smaller pupil areas.
- These findings were shown to be persistent upon adjusting for demographic and ocular variables, suggesting that pupil area can independently modulate lens efficacy across different lens types and treatment outcomes.
- In addition, the subgroup analysis indicated that the effect was more pronounced under mesopic conditions, highlighting the importance of ambient lighting setting for optimal lens performance.
Scatterplots showing correlations between axial growth and pupil area at 12-month follow-up across the three lens types. (Excerpted from Figure 3, Zhu et al. 2026)
Clinical Significance
The interpretation of these results collectively map out a plausible optical mechanism: larger pupils allow more peripheral light rays, modulated by the lens design, to reach the retinal periphery, thereby enhancing the intended defocus signal that regulates ocular growth. In clinical practice, this can be a crucial component when it comes to better patient selection and extrapolation of the treatment efficacy by myopia control spectacles. This echoes and supports the plausibility of pupil-size-dependent treatment effect among all other viable myopia control interventions such as orthokeratology and atropine as a combination therapy. Interestingly though, the role of pupil size on clinical effectiveness by multifocal soft contact lenses remained largely inconclusive, suggesting that the notion and common understanding in the multifocality in contact lenses may exert different interpretations and optical mechanisms on patients with various pupillary characteristics.
Moreover, this study provides further merits in consideration of the nuanced relationships between environmental lighting and pupil dynamics when prescribing and evaluating peripheral defocus lenses.
Study Limitations and Caveats
- Lens architecture: The resulting extent of myopic defocus signals delivered to the retina can be impacted by the configuration and placement of peripheral addition zones relative to the pupil margin.
- The homogenous patient population (all of Chinese children) studied in a single center may be subject to selection bias and limit generalizability to broader populations with diverse ethnic backgrounds and ocular characteristics.
- Pupil-size-dependent relationships were not consistently observed across all lens types, suggesting that there can be more involved beyond the differences in lens types alone.
- Ambient illumination, circadian phases and accommodative demand were absent in this study, for which can directly or indirectly influence treatment outcomes in real-world settings.
Takeaways
This study has shed light on the dynamic pupillary characteristics and how it may serve as a key determinant of patient selection and peripheral defocus spectacle lens efficacy for myopia management. Moreover, this study also underscores the importance of more personalized treatment strategies beyond interventions alone.
Abstract
Purpose
To investigate whether pupil area influences the effectiveness of peripheral defocus spectacle lenses in controlling axial elongation and refractive error progression among myopic children.
Methods
This retrospective analysis included 310 myopic children ages 7 to 14 years. Each participant wore one of three myopia control lens types for at least 12 months: type A, defocus incorporated multiple segments (DIMS) lenses; type B, highly aspherical lenslets; or type C, personalized freeform optical design. Participants were grouped by pupil area (above or below the mean). Axial length and spherical equivalent refractive error were measured at baseline, 6 months, and 12 months. A linear mixed-effects model was used to evaluate the effect of the interaction between pupil area and lens type on axial elongation.
Results
Among children with larger pupils, lens type B was associated with less axial elongation and refractive error progression at 12 months compared with types A and C (P < 0.001). In contrast, no significant differences among lens types were observed in children with smaller pupils. An interaction term (β = −0.086, P = 0.002) indicated that the efficacy of lens type B may be influenced by pupil area.
Conclusions
Pupil area may influence the efficacy of peripheral defocus spectacle lenses for myopia control. Children with larger pupils demonstrated greater benefit from highly aspherical lenslets, suggesting that pupil area should be considered in clinical decision-making.
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