A Unified Index to Predict the Success Probability of Myopia Control

An Orthokeratology lens (OK-lens) is a rigid contact lens with a reverse geometry on its back surface. Overnight OK-lens wearing flattens the central cornea (creating minus power) and steepens the mid-peripheral cornea (creating plus power). During the day, this inverted pattern of peripheral corneal refraction induces relative peripheral myopic defocus on the retina to slow down the axial growth. The central portion of an MFCL is designed with minus powers to correct for distance vision, and plus power is directly added to the peripheral part of the lens. Daytime MFCL wear imposes peripheral retinal myopic defocus when the lenses are worn. An MFCL can also reduce axial growth by 52% compared to a single vision spectacle or contact lens.

Myopia control with OK-lens or MFCL requires a long-term commitment from doctors and patients to see the effect become apparent. It is paramount to estimate the probability that a patient would achieve effective control in myopic progression ideally before treatment begins or early during the course of treatment. To this end, efforts have been made to investigate the correlations between axial growth and possible contributing factors. Early research works have covered a variety of parameters at the baseline, including age, spherical equivalent (SE), corneal eccentricity, and corneal thickness. These measurements are nonspecific, indirect, and based on the assumption that their relationships to axial growth are linear, which often leads to contradictory findings and results that are hard to interpret by physicians. Therefore, in this study, we proposed a new index that takes pupil size into consideration by determining the summed relative myopic defocus dosage within the pupillary area (PMDD) to predict myopia control's success rate. This index will be determined for each eye, will be quantified one month after the lens dispensing, and will be used as the predictive variable.