Long -term effects of optical defocus on eye growth and refractogenesis

Long -term effects of optical defocus on eye growth and refractogenesis

December 2015
Tarutta, et al.

Anyone have the full text of this study?

Summary from another paper:
"A recent study has prescribed plus lenses to non-myopic children aged 5–8 years who are at risk of developing myopia [63]. The plus lenses imposed a 1.0 D myopic defocus and the children wore the correction the entire day. No cases of myopia onset have been observed in this group of children during the follow-up period (ranging from 3 to 9 years) [63]. "

(PDF) Prevention of Myopia Onset. Available from: https://www.researchgate.net/publication/336386165_Prevention_of_Myopia_Onset [accessed Feb 19 2020].

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This one? https://www.pum.edu.pl/__data/assets/pdf_file/0007/112849/PomeranianJLifeSci_62-01_025-030.pdf

the one you’re looking for is the title of the topic? that’s the one I linked… *confused *

Weird, that is the right one. I was stressed yesterday, maybe fat fingered the link. Thanks.

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"Conclusions: Permanent low myopic defocus of the image in
binocular spectacle format inhibits eye growth and refraction
shift to myopia in children with low hyperopia, emmetropia and
low myopia. The method of alternating monolateral low myopic
defocus arrests the myopia progression in 81.8% of children
with low myopia for 4 years and 66% for 7 years. "

1st group was just at risk for myopia, and wore preventative plus lenses to correct to 1D. “During the 9-year follow -up period no cases of myopia onset were observed.

" Ultrasound biometry revealed that this shift was caused by thinning of the crystalline lens and deepening of the anterior chamber. "
- thinning of the lens can be bad. This might be why some people report more floaters. If you thin your lens too much, you loose eye pressure.

"changes of the anterior chamber depth and the thickness of the crystalline lens initially induced by positive spherical lenses persisted over the follow -up period accompanied by inhibited axial growth. "


2nd group was low myopic, and wore lenses that corrected one eye for distance (+0.5D), and the other for near (+1.5D), two pairs of glasses were used alternatively to work both eyes over time.

2 patients in 2nd group developed binocular vision problems and had to stop the treatment. They recovered after stopping treatment.

(81.8%) had stable refraction, which grew not more
than ͔0.5D over the whole follow up period

“Ultrasound biometry revealed an insignificant increase in
the axial length”


"It is also possible that the most important factor
is not a particular type of ciliary muscle contraction but the
periods of defocus which are inevitable and recur in the course
of the day due to ciliary muscle fatigue and relaxation. "


word of the day - cycloplegia - paralysis of the ciliary muscle of the eye, resulting in a loss of accommodation. Because of the paralysis of the ciliary muscle, the curvature of the lens can no longer be adjusted to focus on nearby objects.

“Obviously, myopia occurs when the potentials of this emmetropizing mechanism are exhausted.” - implying that there are limits to how much this can work

"low myopic defocus induced by positive spherical lenses and natural defocus induced by the onset of myopia have the same effect on the accommodative -crystalline apparatus"


Takeaways:

  • Day long minor de-focus caused patients to be more far sighted and was protective against myopia progression for 9 years.
  • Don’t mess with binocular vision.
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The lens thinning thing is a bit disconcerting. We already thought that might be happening in active focus. I don’t know what to say.

Then again, supposedly the lens gets thicker with age, if I remember right. So maybe allowing it to thin is good.

Then again, if it’s the ciliary muscle doing this, could it increase the buildup of old layers/density leading to cataract sooner? Worried again.

This is why I’m not a huge fan of overdoing active focus, trying to always pull clarity out of total blur.

Then again, we really know nothing about the details of the mechanism yet. I bet when we do we will find there was little to worry about.

The binocular vision issues were likely due to poor adaptation to plus lenses that were used consistently. Maybe even improper use. Or even low quality lenses/improper PD.

The binocular issues were almost certainly a direct result of putting only one eye at a time in defocus. None of the subjects with equal defocus in both eyes had that issue. I’m guessing they were trying to maintain classroom performance and it backfired. They would have been better off with periodic defocus of both eyes.

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This tidbit keeps coming back to me. They say cataracts are inevitable because the lens only gets thicker with age and doesn’t shed old layers. I wonder if this is a major factor in EM. If so, there’s a limit to how far it can go. the lens is only 1/3 the plus power of the eye, and you need it to not be presbyopic. On the other hand, it might flex better when thinner, there might be a sweet spot where you stave off both presbyopia and myopia.

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We can hope…and work