SO Research Seminar – Beyond the Jessen Factor: Leveraging Tear‑Layer Thickness for Predictable Orthokeratology
Conference / Seminar
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Date
27 Jan 2026
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Organiser
School of Optometry
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Time
13:00 - 14:00
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Venue
Room AG710, The Hong Kong Polytechnic University Map
Speaker
Dr Theodore R Chow
Dr Edward S Chow
Summary
Since the 1960s, the Jessen factor—flattening the orthokeratology (OK) lens base curve by the intended myopic correction plus a compression offset—has guided OK lens design. However, clinical results remain variable because this formula overlooks individual corneal shape, biomechanics, lens geometry, and tear-film forces that drive epithelial redistribution. This lecture revisits the physiological basis of ortho-k and presents evidence for a tear-layer–centred approach to predicting outcomes. Retrospective data show that post-lens tear-layer profile, which captures both lens geometry and corneal morphology, outperforms Jessen offsets. The speaker will outline a prospective trial, discuss imaging and grading strategies, and highlight future directions in ortho-k lens design and myopia control.
Keynote Speaker
Dr Theodore R Chow
O.D., M.Sc.
Private Practice Optometrists
Toronto, Canada
Dr Theodore Chow, OD, MSc, is an optometrist and PhD candidate at the University of Waterloo’s Centre for Ocular Research & Education (CORE), supervised by Professors Lyndon Jones and Paul Gifford. His research focuses on orthokeratology post-lens tear-film dynamics, corneal remodelling, and standardizing lens designs for clinical trials. Clinically, he leads the specialty contact lens and myopia management service at Chow Eye Institute (Markham). He has published and presented internationally, serves on industry advisory panels, and recently won the Daytech Prize for best PhD seminar.
Dr Edward S Chow
OD
Private Practice Optometrist
Toronto, Canada
Dr Edward S. Chow is a pioneer in orthokeratology and specialty contact lenses, with over five decades of clinical experience. Founder and President of Chow Eye Institute in Markham, Ontario, he has managed an estimated 25,000 orthokeratology patients and currently oversees more than 5,000 active cases. Dr. Chow developed the Orthotool™ Custom Design Lens platform and is a Fellow of the American Academy of Optometry and AAOMC, which awarded him its Lifetime Achievement Award. He is a published author and international lecturer, and founded the Global Council of Myopia Management.
