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Tony Houghton
May 24, 2012, 4:28:49 PM5/24/12
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I've been wearing a new pair of glasses for 4 days and getting used to
them comfortably - chromatic aberration and barrel distortion are well
below problem levels - but I have noticed a problem looking at lit
objects against dark backgrounds which I haven't experienced before. If
I try to describe it can anyone offer a diagnosis?
The effect is a kind of faint bleeding or ghosting of light eg when
looking at computer icons or windows against a dark background or street
lights against the night sky. It looks a little bit like the smears of
light you get when AR coated lenses are greasy, but in this case much
more confined to the lit-up shape. The light only bleeds horizontally
but it occurs equally in both eyes. The extent of the bleeding has an
apparent width of about 5mm with a laptop on my lap and gets wider when
I move it further away. And it only occurs looking straight ahead; if I
move my head to one side it disappears with quite an abrupt transition,
but it persists if I look up or down. Reading text doesn't feel
difficult, but again, I thnk it's slightly clearer just off-centre.
My prescription is -6 to -7 with astigmatism. The new lenses are
photochromic (Transitions) 1.56 index plastic with AR coating. I have
another pair of glasses with 1.56 lenses (also coated but not
photochromic) from the same company and I'm not seeing the same effect
with those. I've also had 1.50 photochromic lenses before and don't
remember any such problem.
--
TH * http://www.realh.co.uk
them comfortably - chromatic aberration and barrel distortion are well
below problem levels - but I have noticed a problem looking at lit
objects against dark backgrounds which I haven't experienced before. If
I try to describe it can anyone offer a diagnosis?
The effect is a kind of faint bleeding or ghosting of light eg when
looking at computer icons or windows against a dark background or street
lights against the night sky. It looks a little bit like the smears of
light you get when AR coated lenses are greasy, but in this case much
more confined to the lit-up shape. The light only bleeds horizontally
but it occurs equally in both eyes. The extent of the bleeding has an
apparent width of about 5mm with a laptop on my lap and gets wider when
I move it further away. And it only occurs looking straight ahead; if I
move my head to one side it disappears with quite an abrupt transition,
but it persists if I look up or down. Reading text doesn't feel
difficult, but again, I thnk it's slightly clearer just off-centre.
My prescription is -6 to -7 with astigmatism. The new lenses are
photochromic (Transitions) 1.56 index plastic with AR coating. I have
another pair of glasses with 1.56 lenses (also coated but not
photochromic) from the same company and I'm not seeing the same effect
with those. I've also had 1.50 photochromic lenses before and don't
remember any such problem.
--
TH * http://www.realh.co.uk
Mark A
May 24, 2012, 4:57:27 PM5/24/12
to
value (lower the abbe, more the chromatic abberaton).
Here are some lens materials with their abbe values (sorry for it being hard to read).
Material Index ABBE Specific Gravity
Transitions Plastic 1.5 58 1.27
CR-39 Hard Resin 1.5 58 1.32
Trivex 1.53 44 1.11
Spectralite 1.54 47 1.21
Ormex 1.56 36 1.23
Polycarbonate 1.59 30 1.2
Hi-Index 1.60 1.6 42 1.22
Hi-Index 1.67 1.67 32 1.35
Hyperview 1.66 1.66 32 1.37
Hi-Index 1.70 1.7 39 1.41
Hi-Index 1.74 1.73 33 1.47
Crown Glass 1.523 59 2.54
You problem could be the abbe value, or it could be that your Rx is off a little.
Tony Houghton
May 24, 2012, 6:33:50 PM5/24/12
to
In <jpm7bm$kqd$1...@dont-email.me>,
> You problem could be the abbe value, or it could be that your Rx is
> off a little.
I don't think it's either of those. The non-photochromic pair which are
OK are the same prescription. I experience chromatic aberration as
coloured fringes that are worse looking off-axis, whereas I only get
this new problem looking along the axis.
Mark A <ma...@nowhere.com> wrote:
> I believe that the 1.56 material is Essior Ormex. For an index value
> of 1.56 it seems to have a low abbe value (lower the abbe, more the
> chromatic abberaton).
[Snip]
> I believe that the 1.56 material is Essior Ormex. For an index value
> of 1.56 it seems to have a low abbe value (lower the abbe, more the
> chromatic abberaton).
> You problem could be the abbe value, or it could be that your Rx is
> off a little.
OK are the same prescription. I experience chromatic aberration as
coloured fringes that are worse looking off-axis, whereas I only get
this new problem looking along the axis.
Mark A
May 24, 2012, 7:19:52 PM5/24/12
to
On Thu, 24 May 2012 22:33:50 +0000, Tony Houghton wrote:
> I don't think it's either of those. The non-photochromic pair which are
> OK are the same prescription. I experience chromatic aberration as
> coloured fringes that are worse looking off-axis, whereas I only get
> this new problem looking along the axis.
It's possible that the lens was made incorrectly. I once had a lens made for me with wrong cylinder
> I don't think it's either of those. The non-photochromic pair which are
> OK are the same prescription. I experience chromatic aberration as
> coloured fringes that are worse looking off-axis, whereas I only get
> this new problem looking along the axis.
(astigmatism) correction. Take it to another optician and see if they can measure it.
I believe it has to be one the following:
- Rx
- lens material
- lens finishing (including choice of base curve, etc)
- fitting (proper fitting height, PD, position in frame, etc).
The Real Bev
May 25, 2012, 1:18:37 AM5/25/12
to
On 05/24/2012 04:19 PM, Mark A wrote:
> On Thu, 24 May 2012 22:33:50 +0000, Tony Houghton wrote:
>
>> I don't think it's either of those. The non-photochromic pair which are
>> OK are the same prescription. I experience chromatic aberration as
>> coloured fringes that are worse looking off-axis, whereas I only get
>> this new problem looking along the axis.
>
> It's possible that the lens was made incorrectly. I once had a lens made for me with wrong cylinder
> (astigmatism) correction. Take it to another optician and see if they can measure it.
That would be my guess. In 50 years of 1.5-2.5D of astigmatism it's
> On Thu, 24 May 2012 22:33:50 +0000, Tony Houghton wrote:
>
>> I don't think it's either of those. The non-photochromic pair which are
>> OK are the same prescription. I experience chromatic aberration as
>> coloured fringes that are worse looking off-axis, whereas I only get
>> this new problem looking along the axis.
>
> It's possible that the lens was made incorrectly. I once had a lens made for me with wrong cylinder
> (astigmatism) correction. Take it to another optician and see if they can measure it.
NEVER been corrected completely and is exactly as you describe. Be glad
you CAN be corrected!
> I believe it has to be one the following:
>
> - Rx
> - lens material
> - lens finishing (including choice of base curve, etc)
> - fitting (proper fitting height, PD, position in frame, etc).
Cheers, Bev
===============================================================
I'd rather trust the guys in the lab coats who aren't demanding
that I get up early on Sundays to apologize for being human.
-- Captain Splendid
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