Retinal contour modelling to reproduce two-dimensional peripheral spherical equivalent refraction

Individualized modeling for the peripheral optics of the human myopic eye

Individualized optical modelling of the eye is a useful tool to estimate optical properties of the eye from a set of geometrical parameters. In the context of myopia research, it is important to understand not only the on-axis (foveal) optical quality, but also the peripheral profile. This work describes a method to extend on-axis individualized eye modeling to the peripheral retina. Using measurements of corneal geometry, axial distances, and central optical quality from a group of young adults, a crystalline lens model was built to help reproduce the peripheral optical quality of the eye. Subsequent individualized eye models were generated from each of the 25 participants. These models were used to predict the individual peripheral optical quality over the central 40 degrees. Outcomes of the final model were then compared to the actual measurements of peripheral optical quality in these participants, measured with a scanning aberrometer. A high agreement was found between the final model and measured optical quality for the relative spherical equivalent and J0 astigmatism.

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

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.