Evaluating on-eye wavefront aberrations of a soft contact lens with an optical design simulating orthokeratology

Authors: Xu Cheng(1), Mona Almaghshi(1,2), Mike Yang,(3) Alyra Shaw(4), Noel A Brennan(1)

  1. Johnson & Johnson Vision, Florida, United States
  2. Inc., New Jersey, United States
  3. Centre for Ocular Research & Education, University of Waterloo, Ontario, Canada
  4. Contact Lens & Visual Optics Laboratory, Queensland University of Technology, Queensland, Australia

Date: June 2020

Source: ARVO 2020 abstracts

Summary

If you are not familiar with wavefront aberration terminology then you should read our helpful guide on Understanding Ocular Wavefront Aberrations

Whole eye wavefront aberrations were measured in successful orthokeratology (OK) lens wearers and compared to the same measurements for different study participants with and without wearing a prototype soft contact lens designed to replicate OK induced changed to optical profile. Both prototype CLs and OK increased positive spherical aberration (SA) with no significant difference between the two modalities. The outcomes adding to previous research from the same team (link) and adding further weight to a non optical mechanism for OK’s propensity to slow myopia progression in children.

Clinical relevance

  • By deduction, the failure of the prototype soft CL to slow myopia progression over 1 year, and the similarity in paraxial (on axis) optical profile between the prototype soft CL and OK, suggests that changes to paraxial wavefront induced by OK may not be the mechanism for how it slows progression of myopia.
  • Further work is needed to analyse whether there are any differences in change to off-axis (peripheral) refraction profile.
  • The similarity in wavefront measurements between distance (4m) and near (25cm) fixation suggests similar focus between both conditions and that accommodation at 25cm is not over or under active with OK or while wearing the prototype soft CL.

Limitations and future research

  • Meeting abstract so not fully peer-reviewed
  • Different participants compared for OK vs prototype soft CL
  • Different pupil diameters measured, but only 5mm data presented
  • Comparisons between additional aberrations terms, especially coma, is needed to compare against the existing literature on OK induced change to wavefront aberrations
  • As identified by the authors, off axis refraction measures and assessment on any changes to accommodation is also needed.

Full story

Whole eye wavefront aberrations (Shack-Hartmann) measured at distance (4M) and near fixation (25cm) in:

  • Successful OK lens wearers (n=8)
  • Non-OK wearers (n=20):
    • Without lens wear
    • Wearing prototype soft CL designed to replicate the optical profile induced by OK lens wear (see Link)

Results (5mm pupil diameter):

  • SA at distance (4m):
    • Without lens wear: 0.054±0.050µm
    • Prototype soft CL: 0.350±0.066µm
    • Orthok wearers: 0.364±0.212µm
  • Least-square mean differences (4m):
    • Prototype soft CL - without lens wear: 0.297µm (CI 0.255, 0.338)
    • Prototype soft CL - OK: -0.034µm (CI -0.148, 0.080)
  • 3rd order and total higher order aberrations at distance (4m)
    • Similar results to SA
  • Wavefront aberrations measured at near (25cm)
    • Similar results to distance (4m) measurements

Conclusions

The optical profile as measured by a wavefront aberrometer was similar between wearers of a prototype soft contact lens designed to replicate OK and existing successful OK lens wearers.

Abstract

Title: Evaluating on-eye wavefront aberrations of a soft contact lens with an optical design simulating orthokeratology

Purpose: Orthokeratology (OK) has been shown to be effective in slowing myopia progression. The mechanism of action is hypothesized to be the resultant optical impact to the eye. However, a soft contact lens (SCL) designed to simulate the optical effect of OK (simOK) for myopia control was found to be ineffective in a randomized controlled myopia control trial. The purpose of this study was to evaluate on-eye wavefront aberrations of the simOK lens by comparing to that of successful OK patients.

Methods: Distance (4 m) and near (25 cm) wavefront aberrations were measured with an open-field Shack-Hartmann aberrometer in 8 OK-treated patients (bare eye only) and 20 non-OK subjects with bare eye (simOK-BE) and with simOK lens on-eye (simOK-LOE) between the age of 7 and 25 years. Zernike expansions of wavefront aberration functions to the 6th order were used to determine aberration coefficients for a series of pupil diameters. Zernike coefficient of primary spherical aberration (Z40), Root-Mean-Square (RMS) of 3rd order and total Higher Order Aberrations (HOA, 3rd – 6th orders) at a 5 mm aperture were compared between simOK-BE and SimOK-LOE and between OK and simOK-LOE. A general linear mixed model with a type I error of 0.05 was used for statistical analysis.

Results: Under a 5mm pupil and with a 4-m target, the means (SD) of Z40 were 0.054 (0.050), 0.350 (0.066), and 0.364 (0.212) microns in simOK-BE, simOK-LOE and OK, respectively. Compared to simOK-BE, Z40 was significantly increased with simOK-LOE with least-square-mean (LSM) difference of 0.297 micron (95% CI: 0.255, 0.338, p0.001). There was no significant difference in Z40 between simOK-LOE and OK (LSM difference (95%CI): -0.034 micron (-0.148, 0.080), p=0.783). Similar results were found between conditions for near wavefront and for total 3rd order aberrations and total HOAs.

Conclusions: This exploratory study demonstrated that wearing SCL designed to simulate the optical impact of OK resulted in a significant increase of HOAs in the eye. The magnitude of HOAs, including primary spherical aberration and 3rd order aberrations, was similar to those of the OK patients. To fully characterize the on-eye optical performance of the simOK lens and understand the mechanism of action of OK, additional analysis of off-axis refraction and accommodative response with the simOK lens will be examined.

Abstract link is here

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About Paul

Dr Paul Gifford is a research scientist and industry innovator based in Brisbane, Australia, and co-founder of Myopia Profile.

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