The validity of the Jessen formula in overnight orthokeratology: a retrospective study

Ophthalmic & Physiological Optics : the Journal of the British College of Ophthalmic Opticians (Optometrists)
Ben ChanJohn Mountford

Abstract

To investigate the validity of the Jessen formula, with a compression factor of 0.75, in determining the back optic zone radius (BOZR) of an orthokeratology (ortho-k) lens for myopic reduction [i.e. BOZR = flattest K- (target reduction + 0.75)]. One hundred and twenty-three consecutive ortho-k patient files from the Optometry Clinic of The Hong Kong Polytechnic University were reviewed. Pertinent data at the preliminary visit and at the morning visit after 2 weeks of lens wear for 63 patients who fulfilled the inclusion criteria were retrieved for analysis. All patients were either fitted with DreimLens (DreimLens Taiwan, Taiwan Macro Vision Group, Taiwan, China) or eLens (E&E Optics Ltd., Hong Kong SAR, China) designs. Only data from the right eye were analysed. The validity of the Jessen formula was evaluated by comparing the equation of the plot of myopic reduction attempted (based on the Jessen formula) and myopic reduction achieved (based on subjective refraction). The Jessen formula was found to underestimate the intended target of myopic reduction following ortho-k. The results suggested that the formula should be revised to BOZR = flattest K- (1.23 target reduction + 1.27). If the intention is to overcorrect the ortho-k...Continue Reading

References

Jun 1, 2000·Optometry and Vision Science : Official Publication of the American Academy of Optometry·J J NicholsM A Bullimore
Sep 27, 2002·Optometry and Vision Science : Official Publication of the American Academy of Optometry·Marjorie J RahJoseph T Barr
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Citations

Jun 28, 2012·Eye & Contact Lens·Jaume PaunéLluïsa Quevedo
Mar 1, 2018·Eye & Contact Lens·Rémy Marcotte-CollardLangis Michaud
Oct 22, 2009·Optometry and Vision Science : Official Publication of the American Academy of Optometry·Sin Wan CheungBen Chan
Mar 1, 2019·Investigative Ophthalmology & Visual Science·Christine F WildsoetJames S Wolffsohn
Jul 3, 2019·Clinical & Experimental Optometry : Journal of the Australian Optometrical Association·Jason K LauPauline Cho
Mar 30, 2021·Contact Lens & Anterior Eye : the Journal of the British Contact Lens Association·Stephen J VincentLyndon Jones
May 5, 2021·Ophthalmic & Physiological Optics : the Journal of the British College of Ophthalmic Opticians (Optometrists)·Kim DuongJared Cox
May 12, 2021·Eye & Contact Lens·Yuanhao HeStephen J Vincent

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