Trial Lens


I believe in intelligent self checking. I also believe that many ODs simply “give up” on the general public, and will not take the time to discuss the issue of “self-prevention”, when you can still read the 20/40 line. (Passes the DMV requirement of 20/40 for almost all DMV test.)

Since an OD has given up on you, I suggest this self-measurement to be a protective, or self-defense measure. I constantly see people with a -1.0 to -1.75 diopter prescription, being able to read the 20/40 line. But they never know they are over-prescribed – until they have the fortitude to actually check themselves.
This is the purpose of presenting these self-measurement, and self checking lenses. In addition, with some more skill, assuming you have self-checked 20/40, and have some test-lenses, you can determine the minus lens you will require to read the 20/20 line. This is very easy – when you get comfortable, holding up a lens, and finding the minimum minus to give you 20/20.


It is just objective science and common sense. It no sense will it replace a full medical exam, conducted by an ophthalmologist. But – the habit of “prescription” in an office is to give you the strongest minus possible. This means that, even if you have 20/20, you will be given a -1.0 diopter, for the simple reason that that lens will give you 20/13, and even 20/10 vision.

But it is well-known that wearing a minus lens, simply makes your vision ‘adapt’ to that strong minus – and you get down to 20/60, and self-measured -2.0 diopters.

Virtually no OD will take the time to explain this issue to you. This is my objection to this type of “excessive practice”. This is why I do these measurement myself. If I can not get 20/20 though a -2 diopter lens (at home), then I certainly will go to an ophthalmologist to find out what the medical problem is – that prevents me from demonstrating 20/20 to myself.

It is early wise prevention steps – that are necessary to never start wearing a minus lens – by always objectively exceeding the required 20/40 line – at home.
You can make your own judgments about these issues yourself.


So – how do you resist that first minus lens?  In this video, the person probably has about 20/40.  The minus (with the leaves), gives about 20/13 vision.  The point is this – you must check your Snellen yourself.  That is the start of self-imposed prevention.

It does indeed take an effort to do this checking.  Your OD has NO CONCERN about your long-term vision – and your desire to keep it.  In fact, he will not even help HIS OWN CHILDREN.  (Read “OD MYOPIC KIDS”, on this site.)

That is the “last straw” for me.  I must help myself – because the OD will not help me – although quite a few recognize that it would be wise to do it.

I have no choice – but to take responsibility that the ODs refuse to accept.  That is open public information about this critical issue.

A good start, would be that they state that they help their own child, by insisting that THEIR child always wears a plus when doing close work.

But since they do not “see there way clear” to say that – I must choose to protect my own vision by 1) Confirming my own vision to be 20/20, and 2) Measuring my own refractive status – objectively.  That is how I avoid any “fighting” with an OD about this critical issue.

Simple Trial Lens Set

Trial Lenses for Home Checking

Subject:  Using a Trial Lens set to measure your refractive STATE.

A Snellen seen through a -1/2 diopter minus lens.

Snellen and -1/2 diopter effect.

Snellen as seen through a -1/2 diopter lens.

This is what plus and minus lenses look like — with a Snellen chart:

Below is how to obtain a full-fledged Trial-lens set, as well has how to obtain some personal “check lenses” for your own use.

I need low-cost test lenses – that are easy to obtain.  They are not “prescription”, so I do not need a prescription.  Here is a simplified video on how to order these low-cost glasses.  You will order a -1 and a -1/2 diopter for the glasses.  Your PD is 60, and you will require, “single vision”.   The cost is about $7.

This is the basic idea – for checking your refractive state – yourself.  Here is a more complete video from Zennioptical.

I know that a considerable number of prescriptions – are given in a “hurry”.  There is no serious attempt to have the person measure his Snellen visual acuity himself.

I do see over-prescriptions of about -1 diopter consistently. By this I mean that, at home the person measures at 20/20, yet he will be prescribed a -1.0 diopters – with NO DISCUSSION, that you should not wear a minus – because you have 20/20.

How and why does this happen?


9 responses to “Trial Lens

  1. Pingback: Eye 20 70 : Improve Eyesight Without Glasses

  2. Here is a review of four basic lenses – and what they show against a Snellen chart.

  3. Any serious person – who needs to achieve 20/20 from 20/50, needs to have an accurate Snellen set up. This is for consistent viewing. It will take about six months of consistent wearing of a preventive plus lens – to change your refractive state from -1.0 diopters to 0.0 diopters, and verify you read the 20/20 line. Here is the simplified set-up.

  4. As an Engineer, I like to do my own measurements – that is the only way I will trust my results. I only need a few test lenses, of – 1/2, -1, +1/2 and +1.0 diopters. Here is a video of these test lenses.

  5. Here is what a “formal” Trial-Lens kit looks like:

    Very few people have serious “astigmatism” issues – so I just use a “spherical” lens to confirm that I have 20/20 with glasses.

  6. School children and prevention.

    Yes – it is necessary.

  7. I believe in being safe. But – because I see no help coming from an optometrist. For this reason, I must personally check my own eyes, using this so-called, “subjective method”.

    The key issue is this. Do you have a true medical problem?

    The optometrist tells us to use a pin-hole lens. If you are reading the 20/50 line, and you use a pin-hold, and can read the 20/20 line, then you do not have a medical problem.

    This is critical for anyone who chooses to restore their distant vision, using various Bates methods, and a plus lens. You can not solve your refraction issue, until you have personally verified your vision using that pin hole.

  8. Better version of ordering glasses:

    Click on 4.00 for the basic ordering form.

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