Back Optic Zone Diameter in Orthokeratology
The Role of Back Optic Zone Diameter in Myopia Control with Orthokeratology Lenses
There was a study published in 2021 that compared the efficacy of controlling the annual increase in axial length (AL) in myopic Caucasian children based on two parameters: the back optic zone diameter (BOZD) of the orthokeratology (OK) lens and plus power ring diameter (PPRD) or mid-peripheral annular ring of corneal steepening. You can access the study here.
The research involved 71 myopic patients, mostly young and male, who were treated with different orthokeratology lens designs from a Spanish optometry clinic.
The sample was divided into groups with BOZDs above or below 5.00 mm and the induced PPRD above or below 4.5 mm, and the relation to AL and refractive progression at 12 months was analysed.
Subjects with smaller BOZDs, and PRPD within pupil seemed to perform the best to reduce myopia progression.
This means a 76% lesser AL growth or 0.13 mm/year in absolute reduction. Smaller BOZD induces a reduced PPRDs that slows AL elongation better than standard OK lenses.
The BOZD is a factor that is looked at carefully at Carina Eye Care to customise orthokeratology for patients requiring an aggressive myopia management strategy. However, the outcome of orthokeratology is not entirely predictable as it depends on multiple corneal factors.
