Defocus method

The 'Defocus Method' is the current name for the EndMyopia approach to reducing myopia. It is the evolution of the 'Reduced Lens Method', first published on endmyopia.org on 29 November 2012. The rename followed the causality: the early version was described in terms of the tool, reduced lenses, while the method is now named for the mechanism those lenses control, which is defocus.

Defocus

Defocus describes where light comes to a point relative to the retina.

• 'Myopic defocus': light focuses in front of the retina.
• 'Hyperopic defocus': light focuses behind the retina.

Both are blur, and they can look alike, but the retina distinguishes them and responds in opposite directions.

Mechanism

Eyes grow into focus through emmetropization, guided by visual feedback. The sign of defocus is the signal:

• Sustained 'hyperopic defocus' drives axial elongation. This is the standard laboratory method for inducing myopia in animal models, known as lens induced myopia.
• Sustained 'myopic defocus' slows or halts elongation.

The response is largely local to the retina and persists when the optic nerve is severed, so it is not mediated by the brain. The peripheral retina matters a great deal.

Applied

A full distance correction worn for close work produces accommodative lag, leaving the image slightly behind the retina, which is hyperopic defocus delivered for hours a day. Standard single vision lenses also leave the periphery focused behind the retina.

The Defocus Method reverses the sign of that input:

• Differentials remove the hyperopic defocus load during close work.
• Normalized keeps a small myopic defocus present at distance, the blur horizon.
• Active Focus engages that edge.

Correction is reduced further as measurements improve, at roughly one diopter per year.

Industry parallel

Every mainstream myopia control product works by imposing peripheral myopic defocus, including DIMS lenses (Hoya MiyoSmart), dual focus contact lenses such as MiSight, Zeiss MyoCare, and orthokeratology. The mechanism is not disputed. It is the basis of the myopia control category.

Origin

The term and the method originate with Jake Steiner. Its component terms were coined on endmyopia.org between September 2012 and July 2013, with dated first published use recorded in the Endmyopia glossary. Full biology: The Defocus Method.

Endmyopia and Active Focus are registered trademarks of Jake Steiner.