Do prescription glasses get made wrong ?

Loagi

Loagi

Loagi

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Joined
22 Mar 2020
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149
I had an eye-test and got a new set of glasses as the old ones were a bit bent from being sat on. The new prescription was very similar to the old one, and the new glasses are a similar size frame/lenses.

With the new ones I can't look down and read a mobile phone, but if I hold it at the same distance straight ahead I can. With the old glasses I can read it in both locations.

If I tip the new glasses above my ears I can now look down and read the phone.

Does this suggest the lenses may be out of spec (e.g. the focal point in the wrong place) ?
 
probably when someone behind the counter at the shop ordered the glasses, they might have typed in the wrong perscription numbers, so probably wrong lense type. take em back and ask them to try again
 
Yes. When I had glasses I regularly ended up getting lenses that were wrong. Go back to your opticians and they can check.
 
if they are single focus lenses then they work best when looking through from normal angle, if you are looking down off-axis you don't expect focus to be as good,
if the new ones are a thinner lense material with higher refractive index then I could believe off-axis viewing may be different to earlier glasses,
don't most glasses have a satisfied or money back option you can use.


I have varifocals designed to give you your near sight prescription when you look down and far-sight looking straight ahead.
 
As said above, yes, it happens. Take them back. It took three attempts for my current ones to be made properly.
 
My eye consultant advised that I go indie as he had similar feedback about the high street chains from other patients on his caseload, so I did go indie. Had no problems so far.

Disclaimer: Don't lose your glasses like I did, because you will be stumping up for another set :p
 
i used to work in a lab that made prescription lenses and there are checks on the lenses to make sure they are the correct prescription before they go out but rarely sometimes some errors did creep in so yes it's possible.
 
you didn't investigate salvaging lenses from, sat on glasses, re-framed ? frames i had in that situation were no longer made

[ complex article that explains focus problems

The very considerable aberrations that occur with flat form lenses make it imperative that during refraction trial frames/phoropters are fitted with the plane of the front perfectly vertical and the centre of the trial lens, which is flat form, perfectly aligned with the pupil centre such that the pantoscopic angle is zero. Figure 5 shows the field diagram for a +4.00DS trial lens made in plano-convex form. It can be seen that at 20˚ eccentricity (eg 10˚ tilt plus OC 5mm up due to low sitting trial frame) the sagittal power is around +4.25DS and the tangential power +4.75DS. In other words, in the primary position of gaze, the patient is experiencing +4.25/+0.50 x 180 when the optometrist would prescribe +4.00DS.
...
Lenses designed to reduce or eliminate the above aberrations and provide the highest standard of off axis visual acuity are known as best form. The form of lens required for a given back vertex power can be determined from Tscherning’s ellipses, there being different ellipses for each lens design philosophy, refractive index, working distance and centre of rotation distance (which is normally assumed to be 27mm).

It should be noted that all best form lenses are more bulbous and therefore cosmetically inferior to their flat form cousins
Click to expand...

..so if frame was fitted say 5mm too low or, just looking down at 10degrees, both can contribute to lost focus and you'd see lense power 4.75 not prescription 4.00
]
 
Late to the party but after reading this thread when it started it reminded that i had new glasses made back in March. I stopped wearing them because they gave me a headache. So 2 weeks ago I took it in and it turns out they didn't measure the position of where my pupils would be vertically so that was why I would get tired wearing them and lead to headaches.

I got it back on Friday and worn it all weekend, perfect now.
 
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