Correction lens/Glasses advise needed for my Leica M9

[Guest NEIL-D-WILLIAMS]

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Rick

Q Is that in the contact lens or spectacles?

A I am not sure as originally I was fitted with contacts and later had reading glasses done

Q Are your contacts progressive or mono vision?

A They were progressive, the near was great the distance was terrible

Q What is your best corrected visual acuity at far with your left eye?

A 90%

Q Do you have binocular vision?

A No

Q What is your age?

A 54

Q Are contact lenses even comfortable to wear in your left eye?

A Considering I have never worn them before they were ok (just a pain to get in and even a bigger pain to take out)

Q Do you have dry eyes or allergies that might make contacts a poor choice?

A The doctor gave me drops for dry eyes to use for a month before he wants me to try the reading contact for my left eye

Q Do you have any medical eye conditions such as, cataract or macular degeneration, for example?

A No

Q Have you tried progressive glasses and found them difficult to adapt to?

A Yes I use them in my work safety glasses and they are OK, at the same time I had a pair of designer frames fitted with the same prescription and hated them

These are a few of the question we ask patients in our clinic in order to get an idea of what fitting methods may be available to them. We know one very important piece of information already; you better have tack-sharp vision in the RF eye. And, you are not going to be able to focus the RF as well at near with your naked eye because you have lost a large degree of your accommodation with birthdays. And, you right eye is slightly hyperopic and needs to focus 0.25D at ∞. That makes near vision harder for you than others.

Q What would you recommend for my right eye? I was thinking of trying a diopter in the M9-P to sharpen up the viewfinder (I did try them before but really couldn’t see that much of a difference, if I try again should I try focusing through the viewfinder on something near or far??

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[Rick]

NDWgolf, I'll try and address your case and I'll also generalize a bit to keep it more relevant for others.

 

Progressive Bifocal Contact Lenses

 

Progressive or bifocal contact lenses are not suited for the RF. This is because they rely on the much over-rated ability of the eye to see two image distances projected on the retina at the same time; near and far. This is called simultaneous vision.

 

All progressive bifocal soft contact lens designs pretty much rely on having both near and far zones in the lens. This means that the retina has both near and far images projected on it. The visual system is supposed to learn to pick the correct "clear" one depending on whether you are looking at a near or distance target. Progressive bifocal contact lenses provide you with both near and distance at the same time and this why they call it simultaneous vision.

 

But,here is the rub, no matter which distance you are viewing there will always exist a blur image of the other distances projected on the retina. The inherent problem with simultaneous vision is that there will always exist blur and decreased contrast sensitivity. It generally can work quite well for near but, it is often a compromise for distance. And, when it works well for distance, near is not satisfactory.

 

The bottom line is that you get both simultaneous vision and simultaneous blur. But, hey, you can make out letters on the very contrasty chart in the exam room!

 

Simply fitting this lens modality is very often not the best solution. So, the next step is to bring the patient back for about the bazilliontth time and change the fit to modified monovision. Here, we make one contact more for near and one more for far. That is done either by changing the power in the lenses making one far and one more of the reading correction or, we can change the lens-design and fit the distance eye with a center-near design where the annulus surrounding the center of the lens is near (these lenses work better for distance vision) and we fit the near eye with a lens that has a near center with a distance annulus ( these lenses work better for near). Or, we additionally modify the powers of these different lenses and make one eye more near and one more far in the overall power of the lens.

 

Are you still with me? Does this all sound like a compromise? Sounding like the optimum way to correct presbyopia yet? Do you think you would be happy with this for trying to focus a RF? It just depends on what your expectations are. Managing patient expectation plays a large role in successfully fitting contact lenses.

 

**********************************************************************************

 

For NDWgolf, who relies on his right eye for sharp vision, progressive bifocal contact lenses would be a compromise that might work for some situations but, probably would be difficult to use with the RF that requires sharp visual acuity. No matter what type of bifocal soft contact lens is placed on his right eye, the probability that it will compromise his visual acuity will be almost 100%. This method likely won't work for him. I'd think that you would be better if you used no lens in his right eye and maybe tried a +0.50 diopter in the RF.

 

Your lett eye may be able to use a progressive contact but, I believe that there is no progressive lens that will correct your astigmatism and near vision. I may have just learned about a new one that does this but, I wasn't paying attention because, it wouldn't be anything I would fit when there are GP options that I would try first. And, in your case I would just fit your left eye with a single vision (non-bifocal) astigmatic soft lens that incorporate +1.50 of near power in it. That would be like wearing a +1.50 bifocal power lens in your left eye. The +1.50 power would be added to your spectacle correction and that would be the power for that contact. This would be age appropriate and should give you generally good near vision.

 

But, it all depends and your visual systems ability to utilize that near power when you need it. You are very right eye dominant just based on the fact that your brain has not been using your left eye and more to the point; your brain has been trying all your life to ignore it!

 

Oddly, this may work in your favor. Remember the simultaneous vision example where you are presented with two images at the same time, one clear and one blur? Mono-vision contact lens wear works similarly except, the images are on separate retinas; one eye near and one eye far. This can work extremely well if, the patient's visual system can suppress the blurry image and choose to use the clear image. A lot of people with strong binocular visual systems can't do this. The brain just can't get used to having a blurry image along with a clear one. The brain wants to fuse both images and the perception is of a ghost image or a shadow around everything. This drives these people nuts.

 

Those patients that can suppress the near eye when viewing distance and vice versa, do extremely well with the mono vision contact lens fitting method. As you can imagine, few people are either one way or the other. Everyone has to try this to see how they fall on the spectrum of how well they adapt to this. Also, with enough time, months or years, I suspect most people will eventually adapt.

 

NDWgolf, your brain will choose the right eye for distance without a doubt but, the question is; will your brain be able to use the image from the left non-dominant eye or will just continue to use your right eye? This depends on a lot of factors that I won't go into here but, if you are like some patients, they can alternate fixation between their eyes. You mentioned that you don't use your eyes together, so you may be able to consciously alternate to the left eye for near?

 

Your left eye sounds like it has pretty good vision so, this should be good enough for good near vision for most daily tasks because, our near acuity is not as critical as what we expect of our distance.

 

As far as LASIK eye surgery for your left eye goes, first you need to be able successfully prove to yourself with a near contact lens that your visual system will accept this type of correction (monovision) before you decide on the other considerations of refractive surgery.

 

Hope this helps everyone understand a little about this subject from the other side of the chair,

 

Rick

[Guest NEIL-D-WILLIAMS]

^^^^^^^

Thank you Rick for taking the time to try and help a fellow photographer. Your explanation is clear and very much appreciated

Regards

Neil

NDWgolf

[Rick]

Progressive Lenses

 

This is another topic that seems to have some relevance to RF photography. Many people love progressive spectacles. Some hate them. I believe that everyone could be fit with progressive spectacles if, certain perimeters are controlled.

 

First we need a binocular patient. That means a patient that uses both of their eyes together and has good visual acuity in both eyes. Plenty of people that essentially use only one eye can wear progressive glasses, my dad was one, but it can be more difficult.

 

Next, the glasses chosen by the patient actually make a difference. I'd like to see at least 30mm of vertical lens in the frame. Anything smaller can work but, it becomes less optimum when trying to cram both a useful distance vertical area and a vertical near area. So, pick a relatively large frame off the rack.

 

Dont' pick frames that rap around your face like Oakley sunglasses - too much distortion right off the bat. Sure, it can work but, why start off with a problem?

 

Make sure you pick a frame that sits on your nose close to your face. If, the frame stands away from your face it will not work as well for reasons that I'll explain someday.

 

Pick a frame that has your eye at the point of about 30% down from the top. Don't use this % as an exact, just think about it. You want to have enough on the top for distance and a bunch on the bottom for the near progressive power. 1/3 top and 2/3 bottom is just a rule of thumb. What you need to watch out for is, when your eye is right at the top of the frame or if your eye is too low in the frame. Too low means that you need at least 18mm of frame lens below your eye, at least. 20mm is better. That is probably why NDWgolf hates his dress glasses and loves his safety glasses. I bet his dress glasses are one of those cool small (hight) frames that are so popular right now. Fashion hurt's.

 

Now, you need a good optician. The measurements are critical. A good optician is good and a good optometrist is better because, they measured (refraction) your eyes and they know how they work. There is more to your vision than just those numbers you get on that piece of paper. Ophthalmologist are usually somewhere in the middle. They can be great as well but, let's face it, their specialty is surgery. Why do they want to waste their time with glasses and contacts? The real stars in this area are the Optometrists. Find a good one.

 

Next, get a good lens. Cheap places often are cheap because, they use crappy lenses. Good lenses and the good labs that surface these lenses aren't cheap. This can make the difference between having problems with distortion and small reading areas and having a successful fit.

 

Now the best part. If, progressive glasses are done right, they are exceptional for RF cameras. Lars knows that he unconsciously uses his progressive when looking into the RF. As we age, it becomes more difficult to see at near. We need help. It is no different using the RF. If, you had perfect distance vision with or without glasses, you would do fine in the distance of the RF. But, at near you have an accommodative load on your visual system and you just can't make the near clear. Try it, look through your RF at your computer close up and you will see that it isn't easy to read. Forget about the focus patch, I just mean the whole rest of the frame. it should be hard to see close stuff clearly. You need to accommodate your visual system but, if you are old enough, this is difficult. Put your reading glasses on and it should help (at the distance they are used for).

 

Some find that a +0.50 diopter in the RF helps them. It will help with near and it will help some people that are somewhat hyperopic and they might not even know they are and this is why it helps. NDWgolf is slightly near-sighted by ).25D so, this may help him.

 

But, none of this gets around the problem of the presbyopic patient; they can't focus at near very well anymore. So, rangefinder cameras are going to be a challenge.

 

Lar's has gotten around all of this with his progressive glasses. He is letting the glasses do the focusing at near distances for him. He chooses where in the glasses to look through depending on the distance he is shooting while his eye is looking through the RF. I'm sure he has trained himself to do this automatically. It can be a wonderful solution and the best one for older photographers to help produce a clear image in the RF which is so critical. But, everything has to be correct when the glasses are made and when the Optometrist initially makes the measurements (refracts) of the eye.

[lars_bergquist]

You are giving good advice, Rick. But I can second you. I am extremely presbyopic, plus that my eyes have no accommodation at all left. So my vision, though OK in itself, is permanently locked in focus at a point beyond the horizon.

 

I have experimented with correction lenses, but my permanent solution is a pair of progressive specs. They work like a charm. I focus my 135mm Apo-Telyt with them without magnifier or anything. I use these specs for anything (and with binoculars too). The problem is a slight cataract in my right (focusing) eye. We shall see how it develops.

 

The bleary-eyed old man

[Carduelis]

I would like to see the results of several independent longitudinal studies on laser eye surgery before I begin to consider it, but irrespective of their outcome, the "very small level of risk" remains too high.

 

I was always concerned about the risk too and have deferred laser eye surgery for a number of years until I was happy that the surgery was well established and there were no long term issues. It was all the positive responses from friends who had the laser eye surgery that made me take the plunge and also after I had fully researched the clinic that performed the surgery. Price never entered into it as I do not believe that you should go for the cheapest treatment when it concerns your eyesight at the end of the day.

 

With wearing contact lenses for 32 years, I often used to wonder whether there might be any long term issues with having pieces of plastic on your eyes for 60% of the time. After having once had a serious eye infection, I was always worried about it recurring.