In orthokeratology (Ortho-K) for myopia control in children, the mechanism by which overnight rigid contact lens wear reduces peripheral hyperopic defocus and thereby slows axial elongation is:

• A Central corneal flattening shifts retinal focus posteriorly, stimulating photoreceptors to inhibit scleral growth factors
• B Peripheral corneal steepening created by the reverse geometry lens design produces myopic defocus in the peripheral retina, signaling the eye to stop elongating ✓
• C Ortho-K causes corneal epithelial redistribution that increases corneal rigidity, mechanically preventing scleral stretch
• D Nocturnal IOP reduction from contact lens-induced aqueous outflow improvement reduces scleral creep

Explanation

Orthokeratology reverse-geometry lenses flatten the central cornea (correcting the myopic refractive error for daytime clear vision) while simultaneously steepening the mid-peripheral cornea. This mid-peripheral steepening shifts the peripheral image focus in front of the peripheral retina (myopic peripheral defocus). Animal model research (emanating from the Smith and Hung laboratory) demonstrated that hyperopic defocus in the peripheral retina drives axial elongation, while myopic defocus inhibits it. By converting peripheral retinal focus from hyperopic to myopic, Ortho-K signals the scleral fibroblasts to reduce remodeling and axial growth. This mechanism is shared by peripheral defocus-modifying spectacle lenses (e.g., MiSight, DIMS lenses) and atropine's effect on peripheral retina.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.