Cristian wrote:
Hi,

Please help me to understand what is going on with me and my new glasses.

History - In the last +30 years I have worn only Zeiss Single Vision glass lens, in the last 5 years being -5.75 Sph (glass). I have always been extremely happy with my glasses, although 5 years ago I tried non Zeiss lens and I returned them due to chromatic aberrations (yellow/blue edges around bright white contrasting surfaces), as well as poor peripheral lens focus. With the Zeiss I have now I do not experience any of these, and I can look all the way through the side edges of the lens and the image remains sharp, with no colour aberrations or shape deformations. BTW – the thickness at these lens edge is ~4 mm.

Now - my new Rx calls now for -6.25 Sph -0.25 Cyl with Add +1.5 Axis 80.
Given my experiences in the past, my optician told me to go with Nikon Seemax, since they will give me the widest field of vision, and virtually no aberrations – which I did. The result: I am at the second pair now (looks like first one was not positioned correctly) – and my distance field of vision is terrible, no matter the adjustments they tried: basically, if I look forward (far) I see perfect in the lens’ centre, and just few degrees off centre, left or right – it becomes blurry, like for e.g. road signs on the left or right side of the street, at ~50m ahead – I must turn my head, or cannot see them in focus anymore.
I understand that PAL will not offer a wide distance field of vision anywhere near compared to my Zeiss – but I found the results terrible (I am talking about few millimetres left or right on the far field of the lens, not the edge of it, and all while using Seemax…). In addition, I really don’t understand how come latest technology will produce lenses not much different in Rx, but much thicker at same diameter (now at ~7 mm compared to 4 mm) – but this is secondary, the lack of distance field of vision is what I just cannot adapt to.
My optician tells me “it’s me, and I need to adapt” (to something bad, I might ask?)

Please comment or recommend a course of action.

Thank you.

ANSWER

Hi Cristian,

It is true that glass lenses will give minimal aberrations.  This will give you good peripheral vision.  Plastic high-index lenses have become a lot better over the past few years.  Aspheric high-index lenses give much less distortion in the periphery of the lens and you can now get ‘free-form’ single vision lenses that are bi-aspheric, which would give the clearest peripheral vision.  I will also tell you that I do not recommend glass lenses because they are unsafe.  They will shatter much more easily and if they do shatter the pieces can be very sharp and can cause severe eye injuries.  Also glass is extremely heavy.  I do not sell any glass lenses in my practice.

Moving on to your progressive lenses, you are exactly right that with progressive lenses the clearest  vision is in the centre of the lens.  To see clearly you must be looking through the centre of the lens.  When you look an object you need to point with your nose to have that object come into clear focus.  This is something that people do adapt to.  As a result progressive lens wearers do have to move their head more than people who wear single vision lenses. Sometimes adaptation to this can take a long time.  Every person is different, but I would say it can take at least 2-4 weeks to adjust and sometimes longer.  The Nikon SeeMax is an excellent lens.  If you find you cannot adjust or do not want to deal with this limitation you could go back to single vision lenses or go to a straight top bifocal (there would be a line on the lens).  The advantage of the bifocal is that you would have better peripheral vision; the disadvantage is that they are not good if you do any amount of computer work.  If you do a lot of computer work you would be better off going with two pairs of glasses – one for distance tasks and one for near tasks.

As far as the thickness of the lens is concerned that depends on a number of factors.  The first is the index of the lens.  The higher the index the thinner the lens will be.  Glass lenses have an index of about 1.52.  Regular plastic lenses have an index of 1.5.  High index plastic comes in 1.6, 1.67 and 1.74. With your prescription I would recommend a high index lens.  The size and shape of the frame and where your pupil is located in the frame also play a role.  Square frames will have thicker edges than an oval frame and if your pupil is not centred in the frame, one edge will be thicker.

Dr. Carol Doman

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