Research Article|Articles in Press, 101848

Factors influencing treatment zone size in orthokeratology



      The aim of this study was to analyze the influence of corneal topography, contact lens parameters and degree of myopia on the treatment zone (TZ) and peripheral plus ring (PPR) size in orthokeratology.


      In this retrospective study the topographic zones of the right eyes of 106 patients (73 female, 22.16 ± 8.96 years) were analyzed in the tangential difference map of the Oculus Keratograph 5M (Oculus, Wetzlar, Germany). Using the MB-Ruler Pro 5.4 software (MB-Softwaresolutions, Iffezheim, Germany) the horizontal, vertical, longest, shortest diameters and area of the TZ; horizontal, vertical, total diameters and width of the PPR were measured. Correlations were determined between these zones and the subjects’ baseline parameters (myopia; corneal diameter, radii, astigmatism, eccentricity, sagittal height; contact lens radii, toricity and total diameter) for three back optic zone diameter (BOZD) groups (5.5, 6.0 and 6.6 mm). A stepwise linear regression analysis was performed to test for TZ and PPR predictability.


      In the group of BOZD 6.0 correlations were found between the amount of myopia and the short TZ diameter (r = −0.25, p = 0.025); the steep corneal radius and the vertical diameter (r = –0.244, p = 0.029), the longest diameter (r = −0.254, p = 0.023) and the area (r = −0.228, p = 0.042) of the TZ; the amount of astigmatism and PPR width (r = 0.266, p = 0.017); eccentricity of the steep corneal meridian and PPR width (r = –0.222, p = 0.047). BOZD correlated significantly positively with all zones (p < 0.05). The best prediction model (R2 = 0.389) resulted with the TZ area as the outcome variable.


      The amount of myopia, topography and contact lens parameters influence TZ and PPR in orthokeratology. Describing the TZ by its area may provide the most accurate representation of its size.


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        • Caroline P.J.
        Contemporary orthokeratology.
        Cont Lens Anterior Eye. 2001; 24: 41-46
        • Haque S.
        • Fonn D.
        • Simpson T.
        • Jones L.
        Corneal and epithelial thickness changes after 4 weeks of overnight corneal refractive therapy lens wear, measured with optical coherence tomography.
        Eye Contact Lens. 2004; 30: 189-193
        • Carracedo G.
        • Espinosa-Vidal T.M.
        • Martínez-Alberquilla I.
        • Batres L.
        The topographical effect of optical zone diameter in orthokeratology contact lenses in high Myopes.
        J Ophthalmol. 2019; 2019: 1082472
        • Guo B.
        • Cheung S.W.
        • Kojima R.
        • Cho P.
        One-year results of the Variation of Orthokeratology Lens Treatment Zone (VOLTZ) study: a prospective randomised clinical trial.
        Ophthalmic Physiol Opt. 2021; 41: 702-714
        • Gifford P.
        • Tran M.
        • Priestley C.
        • Maseedupally V.
        • Kang P.
        Reducing treatment zone diameter in orthokeratology and its effect on peripheral ocular refraction.
        Cont Lens Anterior Eye. 2019; 43: 54-59
        • Sridharan R.
        • Swarbrick H.
        Corneal response to short-term orthokeratology lens wear.
        Optom Vis Sci. 2003; 80: 200-206
        • Lu F.
        • Simpson T.
        • Sorbara L.
        • Fonn D.
        The relationship between the treatment zone diameter and visual, optical and subjective performance in Corneal Refractive Therapy lens wearers.
        Ophthalmic Physiol Opt. 2007; 27: 568-578
        • Smith E.L.
        • Kee C.
        • Ramamirtham R.
        • Qiao-Grider Y.
        • Hung L.-F.
        Peripheral vision can influence eye growth and refractive development in infant monkeys.
        Invest Ophthalmol Vis Sci. 2005; 46: 3965-3972
        • Chen Z.
        • Niu L.
        • Xue F.
        • Qu X.
        • Zhou Z.
        • Zhou X.
        • et al.
        Impact of pupil diameter on axial growth in orthokeratology.
        Optom Vis Sci. 2012; 89: 1636-1640
        • Pauné J.
        • Fonts S.
        • Rodríguez L.
        • Queirós A.
        The role of back optic zone diameter in Myopia control with orthokeratology lenses.
        J Clin Med. 2021; 10: 336
        • Marcotte-Collard R.
        • Simard P.
        • Michaud L.
        Analysis of two orthokeratology lens designs and comparison of their optical effects on the cornea.
        Eye Contact Lens. 2018; 44: 322-329
        • Vincent S.J.
        • Cho P.
        • Chan K.Y.
        • Fadel D.
        • Ghorbani-Mojarrad N.
        • González-Méijome J.M.
        • et al.
        CLEAR - Orthokeratology.
        Cont Lens Anterior Eye. 2021; 44: 240-269
        • Sun L.
        • Li X.
        • Zhao H.
        • Li Y.
        • Wang K.
        • Qu J.
        • Zhao M.
        Biometric factors and orthokeratology lens parameters can influence the treatment zone diameter on corneal topography in Corneal Refractive Therapy lens wearers.
        Cont Lens Anterior Eye. 2022; : 101700
        • Liu G.
        • Chen Z.
        • Xue F.
        • Li J.
        • Tian M.
        • Zhou X.
        • et al.
        Effects of myopic orthokeratology on visual performance and optical quality.
        Eye Contact Lens. 2018; 44: 316-321
      1. L. Jung, M. Liu, Comparing 5mm and 6mm Back Optic Zone Diameter (BOZD) in Orthokeratology Lens Design. Poster session presented at:, Las Vegas, USA, 2022-2022.

        • Owens H.
        • Garner L.F.
        • Craig J.P.
        • Gamble G.
        Posterior corneal changes with orthokeratology.
        Optom Vis Sci. 2004; 81: 421-426
        • Faria-Ribeiro M.
        • Belsue R.N.
        • López-Gil N.
        • González-Méijome J.M.
        Morphology, topography, and optics of the orthokeratology cornea.
        J Biomed Opt. 2016; 21: 75011
        • Guo B.
        • Wu H.
        • Cheung S.W.
        • Cho P.
        Manual and software-based measurements of treatment zone parameters and characteristics in children with slow and fast axial elongation in orthokeratology.
        Ophthalmic Physiol Opt. 2022; 42: 773-785
        • Guo H.-C.
        • Jin W.-Q.
        • Pan A.-P.
        • Wang Q.-M.
        • Qu J.
        • Yu A.-Y.
        Changes and diurnal variation of visual quality after orthokeratology in myopic children.
        J Ophthalmol. 2018; 2018: 1-10