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Old 20th August 2008, 11:14   #1
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Default Queer problem with my specs

There was another thread on powered sunglasses but I thought this might not have been relevant to that.. need some advice on this strange problem I have always faced..

Over the last couple of years, the glasses that I have had made (my power is -1.25 and -1.5) have never been satisfactory.

When the glasses sit normally on my nose, the image is blurred but if I tilt them a little towards my eyes (from the bottom of the frame), the image becomes clearer/sharper.

THis has been the problem with different kinds of frames and from different opticians. No one can seem to tell me whta the problem is! Has anyone else faced a similar kind of a problem. I want to get a decent pair made.. am using lenses for the moment.
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Old 20th August 2008, 11:54   #2
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Hello Mayank,

Excellent title. I thought your specifications were queer.
This would of course mean that you were quite gay, lol. This would not lower my respect for you. Some of my best friends swing my way.

I have been wearing glasses since I was a little boy of 7. I wore them till I was 17, then wearing contact lenses when out and glasses at home.
Till I had a successful lasik operation when I was 32, I had extensive experience with glasses.

It is quite simple, when you tilt the lower portion of your glasses towards your eyes, you change the refractive index of the lenses in your glasses, making them more powerful than they actually are. This is the simplest explanation I can offer you. The same phenomenon occurs, regardless of that fact that the corrective lenses in the glasses are coloured, tinted or shaded.
Now comes the question of - why does it seem clearer.

As any myopic person will tell you, if you wear a number that is higher (technically lower as myopia runs in negative numbers) thing do seem sharper.
For example, if your prescription correction was -2 and you wore glasses of -2.25, it would seem clearer, albeit objects would seem smaller than actual size.
Similarly, by tilting your glasses (regardless of frame) your are increasing the negative index by -.025 or -.5 or even more. This makes things look clearer, but smaller.

If you are 100% sure that with your existing prescription and glasses worn correctly, things are blurred - then you need a new eye prescription.

P.S. - Lenses will always appear clearer. They are closer to your eyes, cleaner than regular glassers, do not suffer from internal reflections and most opticians will give you soft lenses of a marginally higher number than the prescription.
It would also interest you that IMO certain companies like Killer Loop and others incorporate a refractive index of -0.25 into their regular sunglasses, to make the overal view using the glasses sharper and clearer.

Ram will be able to offer you a deeper and highly technical insight into this. I am 100% sure that his knowledge of corrective eyewear surpasses mine.

Last edited by Sam Kapasi : 20th August 2008 at 11:56.
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Old 20th August 2008, 12:30   #3
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I am runnning on -3.0 on both my eyes. Tried Contact lenses, but lost one during washing my face. Hence I am sticking to my glasses only.

To answer to your query, is it that you have a cylindrical component also in your sight, as well as spherical ? Just my thoughts. This might create some weird look the way one can see objects.

Sam, Did you go for lasik ? I am literally scared to go under the knife to get myself rectified. Can you shed more light on it, if you have time !
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Old 20th August 2008, 12:43   #4
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Lambu, I had severe myopia most of my life.
Left eye -4.5
Right eye -5 with cylindrical error.

I was scared to get my eyes operated. I thought about it for 10 years. Made 6 visits to the lasik surgery centre 3 years ago. Understood the details, every small detail and if there were any risks.

Finally took the plunge with a little bit of courage and encouragement from a friend. I have never looked back since. It has been 3 years. No complications, no problems and no glasses.
I am a happy man. For the first year I went mad with sunglasses, buying everything I could buy, lol.

I went to Dr. Niteen Dedhia in Mumbai. You can search for him on the internet.

Last edited by Sam Kapasi : 20th August 2008 at 12:45.
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Old 20th August 2008, 13:13   #5
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Sam,

Thanks a lot for your encouraging words. Let me mentally prepare myself and then I shall start visiting the lasik center. Should be worth the time spent
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Old 20th August 2008, 13:56   #6
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Mayank, Sam has explained quite well, the reason behind why you are able to see clearer with your glasses tilted. When i used to use spectacles, i used to resort to the same method at times. Needless to say, it was also an indication that i needed to get my eyes checked.

I've been using soft lenses from B&L for the past 6 years now, and such a problem is not felt while using them. As for lasik, didnt really give it much thought so far, as the journey with lenses has been quite smooth so far.
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Old 20th August 2008, 14:10   #7
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Quote:
Originally Posted by MC Mayank View Post

Over the last couple of years, the glasses that I have had made (my power is -1.25 and -1.5) have never been satisfactory. .
Please be more specific here...it is spherical power or cylindrical power

Quote:
Originally Posted by MC Mayank View Post
When the glasses sit normally on my nose, the image is blurred but if I tilt them a little towards my eyes (from the bottom of the frame), the image becomes clearer/sharper. .
your symptom suggests that it may be cylindrical error. but the axis you seem to be using is probably wrong.

Quote:
Originally Posted by MC Mayank View Post
THis has been the problem with different kinds of frames and from different opticians. No one can seem to tell me whta the problem is!
have you ever been tested after cycloplegia??? that is after eye drops instilled? if not, i would advise you to get it done by a good ophthalmologist

Hope this helps
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Old 20th August 2008, 14:13   #8
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Mayank,

I've seen opticians use a Viewscope kind of device to take measurement of the eye when making spectacles. This is supposed to ensure that they cut the glass at the right curvature and you get a clear image.

check with your optician if he has this device.
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Old 20th August 2008, 15:28   #9
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Quote:
Originally Posted by Sam Kapasi View Post
It is quite simple, when you tilt the lower portion of your glasses towards your eyes, you change the refractive index of the lenses in your glasses, making them more powerful than they actually are.
Change the refractive index of the lenses? Isn't refractive index a material's property irrespective of its thickness and or relative position?

Anyway, what I suspect (and this is a really wild guess, I have zero knowledge of all this glasses business, never wore one) is that when you tilt the glasses, the upper surface of the glasses go further away from your eye and help focus the image better. Either that, or the tilt causes the image to be formed on some other part of the retina.
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Old 20th August 2008, 18:23   #10
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Quote:
Originally Posted by Sam Kapasi View Post
Hello Mayank,

Excellent title. I thought your specifications were queer.
This would of course mean that you were quite gay, lol.
Hehehe, Sam, I give it to you. Need to watch out with the titles the next time. Luckily for me, it wasn't something like 'my queer problem'

Quote:
Originally Posted by Sam Kapasi View Post
If you are 100% sure that with your existing prescription and glasses worn correctly, things are blurred - then you need a new eye prescription.
I had my eyes checked at Manipal by a decent doctor and his opthalmologist.. I guess I can't do better in terms of prescription. But remember, if my prescription was wrong, then my lenses would also given me a blurred vision.
On tilting the frames, the image becomes sharper without reducing in size. So I have a strong feeling that it's something the optician is missing while making my glasses.

Quote:
Originally Posted by i_see View Post
Please be more specific here...it is spherical power or cylindrical power
My prescription reads as follows:
Right eye: Sphere, 1.25; cyl 0.25; axis 30
Left eye: Sphere, 1.5; cyl N/A; axis N/A
*all distance numbers

Well I started wearing glasses in 2004 and I noticed this problem only maybe 2 yrs back or so..never checked before that. The 'queer' thing is that since my power has changed maybe like 4 times altogether.. everytime I got a frame made this problem existed, and I have used about 4 opticians, the latest being Lawrence and Mayo in Bangalore.

Quote:
Originally Posted by i_see View Post
your symptom suggests that it may be cylindrical error. but the axis you seem to be using is probably wrong.
Let's assume the prescription of my axis is OK. Then do you mean the opticians could be neglecting the axis while cutting my lenses?

have you ever been tested after cycloplegia??? that is after eye drops instilled?
[/quote]
No, but does it really help. I asked Manipal hospital during my last check up 4 months ago, they said don't worry about it.

Quote:
Originally Posted by smsrini View Post
Mayank,

I've seen opticians use a Viewscope kind of device to take measurement of the eye when making spectacles. This is supposed to ensure that they cut the glass at the right curvature and you get a clear image.
Lawrence and Mayo did use this. This reason sounds like a good suspect!

Quote:
Originally Posted by Bass&Trouble View Post
Change the refractive index of the lenses? Isn't refractive index a material's property irrespective of its thickness and or relative position?
That's what I thought as well. Sam?
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Old 20th August 2008, 18:35   #11
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Quote:
Originally Posted by Bass&Trouble View Post
Change the refractive index of the lenses? Isn't refractive index a material's property irrespective of its thickness and or relative position?

Anyway, what I suspect (and this is a really wild guess, I have zero knowledge of all this glasses business, never wore one) is that when you tilt the glasses, the upper surface of the glasses go further away from your eye and help focus the image better. Either that, or the tilt causes the image to be formed on some other part of the retina.
No Ajay.

Imagine a cube of glass. 1 in by 2 inches by 1 inch. Now look through the 1 inch side and look through the 2 inch side.

Even though the image is focussed on the same part of your retina, you are looking through more glass, hence a changed refraction. The word refractive index was incorrect.

By tilting the glass, you change the refraction/correction/whatever property and cause the number to increase. Things look smaller and sharper, exactly like increasing the myopic correction by -0.25 or -0.5. Ask anyone who has worn long-term myopic correction glasses and he will concur.
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Old 20th August 2008, 18:43   #12
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Quote:
Originally Posted by Sam Kapasi
Imagine a cube of glass. 1 in by 2 inches by 1 inch.
Cant.

Sorry.

Cube would need all sides to be equal.

But I think I get your point.
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Old 20th August 2008, 19:13   #13
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Quote:
Originally Posted by Bass&Trouble View Post
Cant.

Sorry.

Cube would need all sides to be equal.
OT:
Good catch there, B&T! The Yeti's day off, perhaps? :P
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Old 20th August 2008, 20:21   #14
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Sam, you meant optical power. which is a function of refractive index (practically always constant for a material for a given light) and the curvature of the glass (which changes the way you are explaining).
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Old 21st August 2008, 00:02   #15
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Quote:
Originally Posted by vivekiny2k View Post
Sam, you meant optical power. which is a function of refractive index (practically always constant for a material for a given light) and the curvature of the glass (which changes the way you are explaining).
Yes thank you, that's what i was looking for.

I don't know why, every 28 days I behave strangely for 4 or 5 days, saying weird things. It's almost like there is less blood in my brains.
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