Abstract
Purpose
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.
Methods
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.
Results
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.
Conclusion
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.
Keywords
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Article info
Publication history
Published online: May 01, 2023
Accepted:
April 16,
2023
Received in revised form:
April 4,
2023
Received:
December 24,
2022
Publication stage
In Press Corrected ProofIdentification
Copyright
© 2023 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
