This article was originally published in a sponsored newsletter.

Orthokeratology (ortho-k) has come of age in the past 20 or so years. The initial FDA approvals for overnight ortho-k resulted in wider acceptance of the modality. Optometric teaching institutions in the US and around the world embraced the technology and began to incorporate the discipline as part of their course curriculum. Lens designs morphed as well from 3-curve to 4-curve and 5-curve configurations. And today, toric designs make up a significant percentage of lens fits because they enhance fitting characteristics and provide improved centration.¹
 
The fabrication of these complex designs has become quite sophisticated, especially with the introduction of computer-numeric-controlled (CNC) lathing equipment. Although it’s not initially necessary to fully incorporate topographical data to design a lens, it is required to document post-fit corneal surface changes and position of the corneal treatment zone in relation to the patient’s line of sight. Ultimately, corneal topography analysis is the backbone of ortho-k fitting.
 
Lens materials have progressed as well. For a long time, we’ve understood that maximizing the amount of oxygen transmitted on-eye through contact lenses is necessary for healthy wear – especially in overnight wear with ortho-k.²Recently, five practice locations with 15 eyecare practitioners studied the high-DK Euclid MAX™ (Tisilfocon A) Orthokeratology lenses.³The primary objective was to complete a retrospective data analysis of 60 initial-fit patients (30 spherical and 30 toric) specifically aimed to provide data regarding the safety and effectiveness of this design within the approved indications for use. The study had many positive findings. The primary outcome variable was for vision improvement in uncorrected distance Snellen visual acuity (UCVA) of at least two lines together with better than or equal to 20/40 unaided distance Snellen visual acuity after a minimum of three months of lens wear.
 
The UCVA achieved by patients throughout the study evaluation period indicated good effectiveness of the Euclid MAX Orthokeratology lens when used within its approved indications. Of all eyes at all visits at three months and beyond, 94% achieved 20/40 or better UCVA; 82% achieved 20/25 or better UCVA; and 51% achieved 20/20 or better UCVA. Approximately 90% of eyes met the success criteria at all visits at or beyond three months. The primary safety outcomes showed there were no cases of unresolved loss of best corrected visual acuity and no adverse events in slit lamp findings greater than grade 2. The outcomes also showed a discontinuation rate of 1.8% for patients who completed at least three months of lens wear. These data demonstrated that the Euclid MAX Orthokeratology lenses achieved similar safety and effectiveness outcomes to the original Euclid Emerald Orthokeratology lenses.⁴

In addition to materials that have a high DK to provide excellent transmissibility during wear, there are other material characteristics to consider as well. This balance of properties ensures that, besides high oxygen transmissibility, the lenses wet well on-eye and decrease surface deposits and films (hopefully without special surface treatments); lens stability reduces lens flexure; and surface scratches are avoided during lens handling. After the study was completed, the 15 investigators were surveyed for their real-world experiences. All agreed that Euclid MAX demonstrated excellent deposit resistance and provided wettable surfaces. They also did not find any barriers to offering this design to their ortho-k patients.

Now, fueled by the remarkable advancements witnessed in the past two decades and looking forward to the next 20 years of orthokeratology, the field is poised for groundbreaking innovations in lens design and materials that will transform the way we shape our vision.

REFERENCES

1. Kojima R, Kojima T, Heavyside N, et al. How Often Should We Prescribe Toric Orthokeratology Lenses? GSLS 2021. Available at: https://na.eventscloud.com/website/10665/2021-posters-/. Accessed June 19, 2023.

2. Ladage PM, Yamamoto K, Ren DH, et al. Proliferation rate of rabbit corneal epithelium during overnight rigid contact lens wear. Invest Ophthalmol Vis Sci. 2001;42:2804-2812.

3. Euclid Max Orthokeratology Lens Retrospective Evaluation (MORE), data on file at Euclid Vision Corporation.

4. Euclid. Summary of Safety and Effectiveness Data. Euclid PMA. Available at: https://www.accessdata.fda.gov/cdrh_docs/pdf/P010062B.pdf. Accessed June 19, 2023.