Author Topic: Peripheral defocus while wearing minus lenses?  (Read 2032 times)

Offline HansK

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Peripheral defocus while wearing minus lenses?
« on: February 01, 2015, 05:32:04 AM »
Hi,

I often read that peripheral defocus can also stimulate the eye to grow longer towards myopia. This is pointed out as a (possible) reason why myopia progression does happen. Ortho-K for example claims that it stops or slows myopic progression significantly because of peripheral myopic defocus.

When we wear undercorrected lenses (Todd recommends cutting 0.25 to 0.50 diopters), can this affect us, too? Is there a difference between contact lenses and glasses (concerning peripheral defocus)?

I think if you have consistently 20/30 vision (you must be slightly better, decimal value: 0,7 - required in Germany to pass the DMV), you do not need any minus lens. Todd said wearing undercorrected lenses for distance activities - he says if myopia is too strong, the eye gives up focusing - and practicing print pushing accelerate the process of reversing myopia.

I have 20/50 to 20/40 vision (decimal value: 0,4 to 0,5). Unfortunately, I cannot make out the 20/30 line - rarely, when testing my visual acuity in bright daylight. And if I achieve it, I lose focus after a few seconds.

September 2014 - I stopped ortho-k and let it "wear out" so that I have my refraction back again. And since October 2014, I practice print pushing and my refraction did not change.

I prefer staying at D2 (I can see that very good when I am on my iPhone and look at the time) - I can focus so that D2 becomes D1, but when I blink, I lose focus. I am frustrated that nothing changed. I have -1.25 glasses which are slightly undercorrected (I need -1.50 diopters to see NO BLUR) and I do not wear them, just for seeing the blackboard etc.

I hope you guys who improved within 3 months can help me because I did not. And I want to know if that "peripheral defocus" (with undercorrected lenses) can be "dangerous".

Kind regards,
Hans
« Last Edit: February 01, 2015, 05:36:06 AM by HansK »

Offline OtisBrown

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Re: Peripheral defocus while wearing minus lenses?
« Reply #1 on: February 01, 2015, 06:07:30 AM »
Hi Hans,

A question for you:

Hans> I prefer staying at D2 (I can see that very good when I am on my iPhone and look at the time) - I can focus so that D2 becomes D1, but when I blink, I lose focus. I am frustrated that nothing changed. I have -1.25 glasses which are slightly undercorrected (I need -1.50 diopters to see NO BLUR) and I do not wear them, just for seeing the blackboard etc.

Otis> What strength of a plus lens do you wear, when reading at D2?  Also:

Hans> September 2014 - I stopped ortho-k and let it "wear out" so that I have my refraction back again. And since October 2014, I practice print pushing and my refraction did not change.

Otis> Were you wearing a +1.5 diopter, for all reading, and when doing your print-pushing?



« Last Edit: February 01, 2015, 06:14:35 AM by OtisBrown »

Offline HansK

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Re: Peripheral defocus while wearing minus lenses?
« Reply #2 on: February 01, 2015, 06:13:58 AM »
Hi Mr. Otis,

working with my iPhone or writing (university), I currently use +1.5 diopters (= +3 diopters, because my eyes are "at +1.5 diopters"). In front of the computer, I do not need a plus. I can sit far enough to be at my blur point.

When I do not read that close, I use +1 diopters. My far-point with +1 diopters on my eyes is about 40 cm (sometimes more, sometimes less).

Kind regards,
Hans

Offline OtisBrown

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Re: Peripheral defocus while wearing minus lenses?
« Reply #3 on: February 01, 2015, 06:24:05 AM »
Hi Hans,

Thanks for your report.  There is no doubt in my mind, about the difficulties one has in wearing a plus for the specific purpose of prevention.  For myself,
I would wear the plus on the computer, even if it meant that I had to move my eyes slightly closer to the screen.

Outside, because of depth-of-field, you can probably function with no minus lens.  Driving, and in class, you will need a -1 diopter, in your pocket, to be put on if you need to read something on the board.  These are very frustrating issues for you, and anyone who is working on plus-prevention.  I always agree on that issue.

CONTACT MINUS LENS:

I think that is a truly bad idea.  The reason is that you can not take it off, and leave it off.  The minus has a long-term bad effect.  It is counter productive to wear it.  I know how powerful it seems - to wear it - and how clear your vision is when wearing it.  But for me, I would want to wear NO MINUS LENS, unless I absolutely had to, and that minus would come off-my-face, as soon as possible.

I know this is difficult advice to follow - but you are lucky to have vision good enough, so you can avoid wearing any minus at this time.  (The exception is class work, and driving a car.)

I know it difficult to "juggle" wearing the plus an minus lenses - as describe above.  But I personally do not see any other choice.

DEGREE OF DIFFICULTY:

There is no doubt about the fact that "convincing" yourself to wear the plus for all close work, is difficult.  Expecting any results in about two months is not reasonable, however much we might desire, "rapid results".  I do not judge a person on these issues,  I just suggest very consistent wearing of a plus, almost always whenever you are in the range of 20 inches from the object you are viewing.

It is a shame, that, three years ago, you probably had close-to 20/20, and that you went "down" by -1.5 diopters in years.  Yet no OD "volunteered" this information to you.  I regret that fact.

Now you need a change of about +1 diopters (to begin reading the 20/30 line on a brightly lit Snellen).  It is reasonable to expect that it will take at least one year, of wearing a plus for all close work - to begin to get that result.

You have made a start, in plus lens wear.  I can only hope you can accept the challenge, of continuing to wear the plus for all close work.


Hi Mr. Otis,

working with my iPhone or writing (university), I currently use +1.5 diopters (= +3 diopters, because my eyes are "at +1.5 diopters"). In front of the computer, I do not need a plus. I can sit far enough to be at my blur point.

When I do not read that close, I use +1 diopters. My far-point with +1 diopters on my eyes is about 40 cm (sometimes more, sometimes less).

Kind regards,
Hans
« Last Edit: February 01, 2015, 07:39:52 AM by OtisBrown »

Offline CapitalPrince

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Re: Peripheral defocus while wearing minus lenses?
« Reply #4 on: February 01, 2015, 09:00:08 AM »
Hans,

your visual acuity is quite poor. you should be using an undercorrection for distance of say -0,25D or -0.5D.
that lets you see around 20/30

keep wearing the +1D, theres no reason for you to use a higher plus, since the +1d blur at only 40cm.
this is why i suggest a bifocal. say -0.25D top / +1D.

plan reading at the slight blur point for 2-4 hours a day, and expect about 2 years to get a change of +1D.