Dynamic Refractive Trainer​ (also known as Auto‑focus Training Glasses, Smart Vision Training Device, or Digital Vision Training Glasses) is based on the core principle of vision training. By programming the optical power of the lenses (usually liquid‑crystal lenses) to change continuously, the instrument forces the ciliary muscle of the eye to keep adjusting, aiming to relieve visual fatigue and enhance accommodative flexibility. It can provide some relief for pseudomyopia caused by accommodative spasm.

Working Principle

The theoretical foundation is accommodative function training. The human eye changes the curvature of the lens through contraction and relaxation of the ciliary muscle to see objects at different distances.

Prolonged near work leads to sustained tension of the ciliary muscle and accommodative spasm, resulting in visual fatigue and pseudomyopia. This type of instrument uses a built‑in variable‑focus optical system (e.g., liquid‑crystal lenses, Alvarez varifocal lenses, etc.). While the user is viewing, the system programmatically and cyclically changes the diopter of the lenses (alternating between plus and minus power), simulating the visual scenario of looking far and near. This forces the ciliary muscle to actively contract and relax in rhythm, much like “exercise” for the eyes, with the goal of improving its accommodative flexibility, amplitude, and endurance.

I had the privilege of participating in the entire process—design, component selection, production, and sales—of the first‑generation Dynamic Refractive Trainer in 2016. In the design of dynamic refractive trainers (or smart zoom/vision training glasses), the weight of the glasses is a critical factor, as it directly determines wearing comfort, user compliance, and the feasibility of long‑term, daily use. Through several generations of iteration, the weight of the training glasses has been significantly reduced from 270 g to just tens of grams, laying a solid foundation for achieving a lightweight, unobtrusive wearing experience.

Recommended motor: Nidec ∅6 mm Planetary Geared Stepper Motor​

  • Step angle (motor alone): 18°
  • Gear ratio: 1 : 47.02
  • Mass: 1.1 g
  • Winding resistance: 20 Ω
  • Output torque: >5 mN·m
  • Backlash: <3°
  • Dimensions: ∅6 × 13.25 mm