Investigation of the relationship between contact lens design parameters and refractive changes in Ortho-K
Lo-Yu Wu,
Louise Pellegrino Gomes Esporcatte,
Wen-Kai Li,
Wen-Pin Lin,
Richard Wu,
Lynn White,
Marcella Q. Salomão,
Bernardo T. Lopes,
Renato Ambrósio, Jr.,
Ahmed Abass
Affiliations
Lo-Yu Wu
Department of Power Mechanical Engineering, Nation Tsing Hua University, Hsinchu, Taiwan; Research and Development Center, Brighten Optix Corporation, Taipei, Taiwan
Louise Pellegrino Gomes Esporcatte
Rio de Janeiro Corneal Tomography and Biomechanics Study Group, Rio de Janeiro, Brazil; Instituto de Olhos Renato Ambrósio, Rio de Janeiro, Brazil; Department of Ophthalmology, Federal University of São Paulo, São Paulo, Brazil
Wen-Kai Li
Department of Power Mechanical Engineering, Nation Tsing Hua University, Hsinchu, Taiwan; Research and Development Center, Brighten Optix Corporation, Taipei, Taiwan
Wen-Pin Lin
Research and Development Center, Brighten Optix Corporation, Taipei, Taiwan; Department of Optometry, University of Kang Ning, Taipei, Taiwan
Richard Wu
Research and Development Center, Brighten Optix Corporation, Taipei, Taiwan; College of Optometry, Pacific University, Forest Grove, OR, USA
Lynn White
Research and Development Department, LWVision, Leicester, UK
Marcella Q. Salomão
Rio de Janeiro Corneal Tomography and Biomechanics Study Group, Rio de Janeiro, Brazil; Instituto de Olhos Renato Ambrósio, Rio de Janeiro, Brazil; Department of Ophthalmology, Federal University of São Paulo, São Paulo, Brazil; Brazilian Study Group of Artificial Intelligence and Corneal Analysis – BrAIN, Rio de Janeiro & Maceió, Brazil; Instituto Benjamin Constant, Rio de Janeiro, Brazil
Bernardo T. Lopes
Rio de Janeiro Corneal Tomography and Biomechanics Study Group, Rio de Janeiro, Brazil; Department of Ophthalmology, Federal University of São Paulo, São Paulo, Brazil; Brazilian Study Group of Artificial Intelligence and Corneal Analysis – BrAIN, Rio de Janeiro & Maceió, Brazil; Department of Civil Engineering and Industrial Design, School of Engineering, University of Liverpool, Liverpool, UK
Renato Ambrósio, Jr.
Rio de Janeiro Corneal Tomography and Biomechanics Study Group, Rio de Janeiro, Brazil; Instituto de Olhos Renato Ambrósio, Rio de Janeiro, Brazil; Department of Ophthalmology, Federal University of São Paulo, São Paulo, Brazil; Brazilian Study Group of Artificial Intelligence and Corneal Analysis – BrAIN, Rio de Janeiro & Maceió, Brazil; Department of Ophthalmology, Federal University the State of Rio de Janeiro, Rio de Janeiro, Brazil
Ahmed Abass
Department of Mechanical, Materials and Aerospace Engineering, School of Engineering, University of Liverpool, Liverpool, UK; Department of Production Engineering and Mechanical Design, Faculty of Engineering, Port Said University, Port Said, Egypt; Corresponding author.
Purpose: To investigate the relationship between Ortho-K contact lens design parameters and refractive power change of the eye through a parametric mathematical representation. Methods: The current study utilises fully anonymized records of 249 eyes, 132 right eyes, and 117 left eyes from subjects aged 14.1 ± 4.0 years on average (range 9–38 years) which were selected for secondary analysis processing. The data were split into 3 groups (G1 up to 35 days wear, from 10 to 35 days, G2 up to 99 days wear, more than 35–99 days & G3 more than 100 days wear) according to the length of time, in days, that the lenses were worn. Corneal shape was measured before and after contact lens wear using the Medmont E300 topographer, from which height and distance files were read by a custom-built MATLAB code to construct the corneal anterior surface independently. Changes in refractive power pre and post-Ortho-K wear were determined using constructed tangential refractive power maps from which both centrally flattened and annular steepened zones were automatically bounded, hence used to determine the refractive power change. Results: On average, flat Sim-K and steep Sim-K were reduced after Ortho-K lens wear by 1.6 ± 1.3 D and 1.3 ± 1.4 D respectively. The radius of the base curve was correlated with the mean central flattened zone power change strongly in G1 (R = 0.7, p < 0.001) and moderately in G2 (R = 0.4) and G3 (R = 0.4, p < 0.001). Hence, a strong correlation with the base curve was recorded in group G1 and moderate in G2 and G3. The reverse curve was very strongly correlated to the mean central flattened zone power change in G1 (R = 0.8, p < 0.001) and strongly correlated with G2 (R = 0.6, p < 0.001) and G3 (R = 0.7, p < 0.001). The reverse curve was also strongly correlated with the mean annular steepened zone power change among all groups G1, G2, and G3 (R = 0.7, R = 0.6 and R = 0.6) respectively (p < 0.001). Conclusions: Although the central corneal refractive power change was strongly correlated to the Ortho-K lens base curve, it characterized only 50% of the target power change. However, the annular steepened zone refractive power change appears to be a clearer predictor of target power change, as there appears to be a one-to-one inverse relationship with the target refractive power correction. Differences between these results and the literature may be a result of the topography software smoothing effect.
