Photopic pupil size change in myopic orthokeratology and its influence on axial length elongation

Meng-Jun Zhu; Li Ding; Lin-Lin Du; Jun Chen; Xian-Gui He; Shan-Shan Li; Hai-Dong Zou

doi:10.18240/ijo.2022.08.15

Photopic pupil size change in myopic orthokeratology and its influence on axial length elongation

Int J Ophthalmol. 2022 Aug 18;15(8):1322-1330. doi: 10.18240/ijo.2022.08.15. eCollection 2022.

Authors

Meng-Jun Zhu¹, Li Ding¹, Lin-Lin Du¹, Jun Chen¹, Xian-Gui He¹, Shan-Shan Li¹, Hai-Dong Zou^{1

2}

Affiliations

¹ Shanghai Eye Disease Prevention & Treatment Center/Shanghai Eye Hospital, Shanghai 200040, China.
² Shanghai General Hospital, National Clinical Research Center for Eye Diseases, Shanghai Key Laboratory of Ocular Fundus Diseases, Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai Engineering Research Center of Precise Diagnosis and Treatment of Eye Diseases, Shanghai 200080, China.

Abstract

Aim: To explore the photopic pupil size behavior in myopic children undergoing overnight orthokeratology (ortho-k) over 1-year period and its effects on the axial elongation.

Methods: A total of 202 Chinese myopic children were enrolled in this prospective clinical trial. Ninety-five subjects in ortho-k group and eighty-eight subjects in spectacle group completed the 1-year study. Axial length (AL) was measured before enrollment and every 6mo after the start of ortho-k. The photopic pupil diameter (PPD) was determined using the Pentacam AXL and measured in an examination room with lighting of 300-310 Lx. Stepwise multiple linear regression analysis was used to identify variables contribution to axial elongation.

Results: Compared with spectacle group, the average 1-year axial elongation was significantly slower in the ortho-k group (0.25±0.27 vs 0.44±0.23 mm, P<0.0001). In ortho-k group, PPDs significantly decreased from 4.21±0.62 mm to 3.94±0.53 mm after 1mo of lens wear (P=0.001, Bonferroni correction) and the change lasts for 3-month visit. No significantly change during the other follow-up visits was found (P>0.05, Bonferroni correction). The 4.81 mm PPD may be a possible cutoff point in the ortho-k group. Subjects with PPD below or equal to 4.81 mm tended to have smaller axial elongation compared to subjects with PPD above 4.81 mm after 1-year period (t=-3.09, P=0.003). In ortho-k group, univariate analyses indicated that those with older age, greater degree of myopia, longer AL, smaller baseline PPD (PPD_baseline) experienced a smaller change in AL. In multivariate analyses, older age, greater AL and smaller PPD_baseline were associated with smaller increases in AL. In spectacle group, PPD tended to be stable (P>0.05, Bonferroni correction) and did not affect axial growth.

Conclusion: PPDs experience significantly decreases at 1-month and 3-month ortho-k treatment. Children with smaller PPD tend to experience slower axial elongation and may benefit more from ortho-k.

Keywords: accommodation; axial length; myopia; orthokeratology; pupil diameter.

International Journal of Ophthalmology Press.