Is it necessary to measure pupil size when initiating myopia management? Should pupil size be a factor while selecting a strategy, and does it influence efficacy of myopia control treatments? This question was put forth to the Myopia Profile community. Here is the post asking questions about myopia controlling and multifocal (MF) contact lens designs, along with orthokeratology.
Effect of pupil size in myopia control contact lenses
There are currently two main types of soft contact lenses are used in myopia control treatment on the market. These are myopia control specific designs (eg. concentric dual focus MiSight and extended depth of focus Mylo), and aspheric multifocal designs which are also used for presbyopia (eg. Biofinity D center and NaturalVue).
The myopia control efficacy of MiSight has been shown to be independent of pupil size.1 The BLINK study, which investigated medium- and high-add aspheric multifocal contact lenses for myopia control, measured pupil size but data has not yet been reported on any relationship between pupil size and myopia control efficacy. For reference, the average pupil size in the BLINK study was 5.4 ± 0.7mm in mesopic and 6.5 ± 0.7mm in photopic conditions, in multi-ethnic children aged 7-11 years.2
Vision outcomes can also be influenced by pupil size. In both myopia control and multifocal designs, modelling has shown that a larger pupil size will increase the the area of the pupil covered by the varying focus powers - near and far, but smaller pupils may experience better distance vision.3
Different contact lens designs will influence vision outcomes - two studies of the MiSight dual focus concentric contact lens have shown better than 6/6 or 20/20 equivalent, on average,1,4 while the Biofinity centre distance aspheric +2.50 Add has been shown to need a mean -0.62D over-minus correction for best acuity.5
We don't yet have the data available to see how pupil size may interact with visual acuity outcomes in children wearing these contact lenses for myopia control.
How about orthokeratology?
One small but influential study reported that orthokeratology lens wearers with larger pupil diameters experienced greater myopia control efficacy than those with smaller pupils. They hypothesized that a large pupil allows more myopic defocus shift for the peripheral retina, but did not measure it.6
This paper led to the interest in the interaction between the back optic zone diameter (BOZD) of ortho-k lenses, pupil size and myopia control efficacy. In a retrospective study, it was found that when the pupil size was larger than the BOZD, the patient experienced slower axial elongation.7 No methodology was provided on how the BOZD was chosen for each patient.
A randomized controlled trial8 fit children with either a 5mm or 6mm BOZD, and found that the 5mm BOZD group exhibited only 0.15mm axial growth over two years, compared to 0.35mm in the 6mm BOZD group. Pupil size was measured, but any interaction between pupil size and myopia control was either not present or not reported in this research abstract.
The sum of this data indicates that there is likely a relationship between pupil size, ortho-k lens design and myopia control efficacy, but we don't yet have enough guidance to make changes to clinical practice. An important note is that 5mm BOZD's can influence vision in lower lighting conditions,9 which may be important to some children and young adults.
How does pupil size change optics?
There is still a lot to learn. on this topic. In the case of orthokeratology, the presumption that a larger pupil size will increase the relative peripheral myopic shift has been shown incorrect.10 A larger pupil size will typically result in increased higher-order aberrations of the eye, which have shown a relationship with better myopia control outcomes in ortho-k.11
While smaller treatment zone diameters may increase myopia control efficacy in ortho-k,7,8 but a new discussion has emerged on whether treatment zone decentration may12 or may not13 also have an influence. Authors in this arena caution that fitting properly centered ortho-k lenses is "recommended to ensure the safety of Ortho-K lens wear and to maintain visual quality."13
Take home messages:
- Pupil size may play a role in visual outcomes in myopia control and multifocal soft contact lenses, but it does not impact efficacy with MiSight, and the relationship in center-distance multifocal contact lenses is unknown.
- A complex relationship between pupil size and back optic zone diameter in orthokeratology may relate to myopia control efficacy, but there is still more to learn.
- Prieto-Garrido FL, Verdejo JL, Villa-Collar C, Ruiz-Pomeda A. Predicting factors for progression of the myopia in the MiSight assessment study Spain (MASS). Journal of Optometry. 2022 Jan 1;15(1):78-87. (link)
- Walline JJ, Giannoni AG, Sinnott LT, Chandler MA, Huang J, Mutti DO, Jones-Jordan LA, Berntsen DA, BLINK Study Group. A randomized trial of soft multifocal contact lenses for myopia control: baseline data and methods. Optometry and Vision Science. 2017 Sep;94(9):856. (link)
- Remón L, Pérez-Merino P, Macedo-de-Araújo RJ, Amorim-de-Sousa AI, González-Méijome JM. Bifocal and multifocal contact lenses for presbyopia and myopia control. Journal of Ophthalmology. 2020 Mar 27;2020. (link)
- Chamberlain P, Peixoto-de-Matos SC, Logan NS, Ngo C, Jones D, Young G. A 3-year Randomized Clinical Trial of MiSight Lenses for Myopia Control. Optom Vis Sci. 2019 Aug;96(8):556-567. (link)
- Schulle KL, Berntsen DA, Sinnott LT, Bickle KM, Gostovic AT, Pierce GE, Jones-Jordan LA, Mutti DO, Walline JJ; Bifocal Lenses in Nearsighted Kids (BLINK) Study Group. Visual Acuity and Over-refraction in Myopic Children Fitted with Soft Multifocal Contact Lenses. Optom Vis Sci. 2018 Apr;95(4):292-298. (link)
- Chen Z, Niu L, Xue F, Qu X, Zhou Z, Zhou X, Chu R. Impact of pupil diameter on axial growth in orthokeratology. Optometry and Vision Science. 2012 Nov 1;89(11):1636-40. (link)
- Pauné J, Fonts S, Rodríguez L, Queirós A. The role of back optic zone diameter in myopia control with orthokeratology lenses. Journal of Clinical Medicine. 2021 Jan 18;10(2):336. (link)
- Guo B, Cheung SW, Kojima R, Cho P. One‐year results of the Variation of Orthokeratology Lens Treatment Zone (VOLTZ) Study: a prospective randomised clinical trial. Ophthalmic and Physiological Optics. 2021 Jul;41(4):702-14. (link)
- Carracedo G, Espinosa-Vidal TM, Martínez-Alberquilla I, Batres L. The Topographical Effect of Optical Zone Diameter in Orthokeratology Contact Lenses in High Myopes. J Ophthalmol. 2019 Jan 2;2019:1082472 (link)
- Gifford P, Tran M, Priestley C, Maseedupally V, Kang P. Reducing treatment zone diameter in orthokeratology and its effect on peripheral ocular refraction. Cont Lens Anterior Eye. 2020 Feb;43(1):54-59. (link)
- Lau JK, Vincent SJ, Cheung SW, Cho P. Higher-Order Aberrations and Axial Elongation in Myopic Children Treated With Orthokeratology. Invest Ophthalmol Vis Sci. 2020 Feb 7;61(2):22. (link)
- Lin W, Li N, Gu T, Tang C, Liu G, Du B, Wei R. The treatment zone size and its decentration influence axial elongation in children with orthokeratology treatment. BMC Ophthalmol. 2021 Oct 12;21(1):362. (link)
- Sun L, Li ZX, Chen Y, He ZQ, Song HX. The effect of orthokeratology treatment zone decentration on myopia progression. BMC Ophthalmol. 2022 Feb 15;22(1):76. (link)