can high-order aberrations of the ophthalmic lenses, harm the eye of the wearer ?

[safeir]

sirs
i am wondering here about the high-order aberrations that are found in most standard lenses (old fashioned-manufactured ones) .
i am not talking about these aberrations in the human eye it self .
so the question is :
can these high-order aberrations found in traditionally-manufactured lenses (old ways , not free from) harm the human eye after a while of wearing ?
but why this matters ?
this matters because i am looking for more evidence that free-form made lenses are healthier to the eyes of the customers , and they are urged to change their current lenses to "free-form made lenses" , even with the same prescription .
please dont write about the benefits of freeform .
what i am looking for is the answer of the core question : can these aberrations harm the human eye , and so there is a medical need to change the old traditionally made lenses into freeform made ? what are the negative effects of eye and vision of these tradition lenses ?
thanks

[Wes]

http://www.opticampus.com/courses.php

See the course "Ophthalmic lens design"

[Wes]

Corrected-curve or best-form lenses will not harm anyones eye. Even lenses with poorly selected curves won't harm the eye, but they may force the wearer to become used to aberrations.
Aspheric and freeform lenses can eliminate or reduce those aberrations while providing a flatter lower profile lens and position-of-wear compensations.

[MakeOptics]

Yes and No.

First Yes, any lens that is not best form will create unwanted aberrations or increases in power and astigmatism amoung other effects off axis this can and does lead to asthenopia (eye strain) which has a ICD code so I would say yes. I am speculating on this, but I would venture to say in younger children the possibility exists to create an isekonic situation if the proper curves are not maintained which could lead to strabismus or the lack of visual development.

Now the No, except for the scenario with children involved the effects are reversable, although as Wes has mentioned if the person gets used to the aberrated lens they are going to have a hard time accepting the best form lens sometimes. I personally went without a correction for so long as a child that I still cannot wear my full Rx. 20/25 is the best I can physically handle beyond that and I'm the patient that complains of headaches because the lens is too clear. I have experienced this with my customers as well in the past, complaints of too much clarity, brioghtness, or enhanced color contrast. The effects are similar to a cataract removal to a much lesser degree.

[Speed]

No.

[sharpstick777]

The overwhelming cause of visual trouble is due to the inherant shape of the eye. In general eyeglass lenses themselves cannot cause any more harm to the underlying visual condition, or help it. The path light is corrected with eyewear to variing degree of sucess but the health of the eye will remain unchanged, for better or for worse.

Only contact lenses have the potential to change the shape of the eye, so. Contacts can both improve or damage the eyes in ways glasses cannot and that is one reason they are regulated more thouroughly. Even with Contacts, no health claim is usually made (medically necesary or bandage contacts aside).

I don't think you will ever be able to make a case the Free-form lenses are healthier than standard lenses that would stand up.

[MakeOptics]

To add to my previous post, best form lenses may bot have any benefit for the wearer if they compound the effects of the visual systems aberrations. In essence a best form lens in front of an eye that is not best form is going to be at best a neutral situation and at worst exacerbate the effects of aberration.

[Barry Santini]

Corrected-curve or best-form lenses will not harm anyones eye. Even lenses with poorly selected curves won't harm the eye, but they may force the wearer to become used to aberrations.
Aspheric and freeform lenses can eliminate or reduce those aberrations while providing a flatter lower profile lens and position-of-wear compensations.

This is the main reason why I find so many of my conversion to optimized SV FF lenses experience some initial discomfort and/or headache for the first 1-3 days. Then, they'll tell me "it just clicks" and their vsion is excellent. CL wearers especially.

B

[Barry Santini]

In general eyeglass lenses themselves cannot cause any more harm to the underlying visual condition, or help it. The path light is corrected with eyewear to variing degree of sucess but the health of the eye will remain unchanged, for better or for worse.



I don't think you will ever be able to make a case the Free-form lenses are healthier than standard lenses that would stand up.

Depends on how you define "healthy"

Not completely true, in my experience. Visual processing (part of the visual experience) in the brain adjusts or compensates when HOAs and or off-axis errors are introduced, changed or increased. It then has to "unlearn" the compensation when different lenses are introduced. The eye remains unchanged, yes. But not the visual processing.

B

[chip anderson]

I know that many disagree with this theory but:
In PMMA lenses most but not all myopes stopped progressing. I saw many that would wear them when seeking romance for years at a time and then when for some reason they stopped seeking same and stopped wearing the CL's the progression would continue. In some cases I saw this repeated many times in the same patient.
I also have seen similar but not as pronounced results in RGP's.
In soft lenses I am afraid I have seen the opposite.

The theory is that the eye developes tropicly and if it is in focus most of the time it remains stable. If it is out of focus most of the time (as in spectacles or in poor focus as in many soft lens wearers where less than 20/20 is the norm). The eye continues to grow appearently seeking emetropia (appeareantly we are born hyperopes and if we are lucky the eye lengthens to emetropia and stops, but for some people they pass emetropia (perhaps due to cylinder presence or other factors) and the eye keeps lenghthening, hense myopia increase.

Wow, I can hardly wait for the feed back and controversy on this.

However it could make a case however slight for if the eye were in better focus more of the time with free form, the eye might slow down its growth/change.

Chip

[Wes]

Chip:
Emmetropization:
A process that is presumed to operate to produce a greater frequency of emmetropic eyes than would otherwise occur on the basis of chance. This mechanism would coordinate the development of the various components of the optical system of the eye (e.g. axial length, refracting power of the cornea, depth of the anterior chamber, etc.) to prevent ametropia.

http://sites.google.com/site/myopiao...me-nearsighted

http://www.agingeye.net/myopia/3.3.5.php

http://journals.lww.com/optvissci/Fu...he_12th.6.aspx

I had 20/15 -20/20 vision from my teens into my early 30s. At 32 I began working more intensively at near, both in study and labwork. By 34, I was 20/40 (roughly -1.00). I no longer wear correction for PC use and near work, and there has been no further progression of myopia. Coincidence? Correlation? Causation? Discussion?

[Barry Santini]

It has been suggested that the bio mechanical tension on the eye globe by the external muscles during convergence is relieved through a gradual lengthening of the same.

B

[sharpstick777]

Depends on how you define "healthy"

Not completely true, in my experience. Visual processing (part of the visual experience) in the brain adjusts or compensates when HOAs and or off-axis errors are introduced, changed or increased. It then has to "unlearn" the compensation when different lenses are introduced. The eye remains unchanged, yes. But not the visual processing.

B

You are correct Barry, but in the US here we cannot use the term "healthier" for any product without incurring the oversight and wrath of the FDA. Their definition is fairly stict on the usuage and definition of the term. Recently Reebok was sued for millions because of "toning" claims made by their walking shoes, and even an implied health benefit went to cost them millions.

"Healthier" is not a term I would apply to any product in the US without two independant studies in my hand and army of well dressed lawyers at my side.

[chip anderson]

You can use advertizing words to insinuate "healthy" Words like probiotic, nutrient, and the like. Listen to the commericals on radio and TV, they are full of little meaningless words like this.

Chip

Wes: Causation: Probably your lenses becoming more dense. I'm sure it had nothing to do with the distance you worked at although there were theories and wives tales about close work causing myopia.. The truth is myopes are more comfortable workind a close distances, especially if uncorrected.

[Nikolay Angelov]

Safeir,
You are trying to scare people into more expensive products.
This is bad.

And people pay more for "more"positive benefits. Not for less negative features.
You can say that the lens has less oblique astigmatism error.

OR

You can say that a lens have a larger zone of crisp clear vision.

Same thing but guess which statement will make better sales.

PS: Few people are more worthy of despise than those deceiving about illness to sell a product through fear.
People trust you, don't betray that trust.

[drk]

Nice post, Nikolay.

[Darryl Meister]

i am wondering here about the high-order aberrations that are found in most standard lenses (old fashioned-manufactured ones) .

This article will present the fundamentals of wavefront aberrations in both lens design and ocular aberrometry: Wavefront Aberrations and Spectacle Lenses.

Best regards,
Darryl

[braheem24]

Welcome back!

[Wes]

Welcome back indeed! Where the heck have you been?

[Darryl Meister]

Haven't been checking in here as often as I should. It's been hectic for me lately. I should be able to hang out more regularly again in the not-too-distant future.

Best regards,
Darryl

[optical24/7]

Glad you're back too Darryl!

[Robert Martellaro]

Yay!

[Barry Santini]

I too am glad you're back, Darryl! But the paper also helps point out that we optical nuts often can't see the forest for the trees:

1. Dr.s continue to say "there is such a small change in your Rx, don't bother getting new lenese/glasses." but, newer-designed lenses may just be the ticket to improving their vision.

2. Dr.s continue to advise lower ammetropes, those about 0.50D around plano to get eyewear "only if they feel they need it."

3. Motor vehicles acuity threshold standards do not take low illuminance environments into account, while almost 60% of states don't regulate eyewear delivery anyway.

Bottom line: HOA correction is best applied where the fire is hottest: in the corridors of matures adds of presbyopes who insist that their general use progressive deliver maximum intermediate utility. But exacting centration standards, both in empirical measurement and fabrication are just as important for the same.

However, the most bottom line subjective vision improvement will come when optimal-abbe materials are used with POW compensated SV FF lenses in both moderate to higher astigmatism and spherical corrections, as well as those fitting situations where the best form fitting principles have been ignored for a long time.

MY ADVICE:: STOP WORRYING ABOUT HOAs, and STOP USING STOCK SV LENSES!

B

[chip anderson]

As to the origional question, Aberrations won't bother the eye so much as they could do a number on the mind. Remeber the world got along without high tech solutions to theoretical problems for a long time.
This doesn't say that they shouldn't be addressed now that better products are available, but I don't think they harmed anyone before we had the means to address the problem.

Chip