Posted , 6 users are following.
For distance monofocal what is the extent of blurriness (loss of focus) in the near and intermediate range?
Does it depend on the extent of myopia an individual had with cataracts? Are there any photos or images that can show the extent of blurriness?
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trilemma kdf123
Edited
Study defocus curves.
https://patient.info/forums/discuss/translating-defocus-curves-from-d-to-feet--803594?page=0 with the jimluck post and attachment being especially good.
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The sharpness vs distance does not depend on the extent of myopia an individual had with cataracts. The old lens is gone, and the new one has its own focus (tho the new lens will not be cloudy). What the old prescription can do is to give a major clue as to what the astigmatism will be if the new lens does not adjust for astigmatism. If your new lens has astigmatism correction, (toric lens), then that will change astigmatism -- hopefully toward zero.
RonAKA kdf123
Edited
Yes, there is an excellent document that shows the typical visual acuity curve vs distance. See figure 1 in particular. It shows the Snellen visual acuity vs distance in meters for a monofocal set for distance (dashed line). It also shows the same information when different steps of myopia are targeted instead of distance. One option to get the full range of vision is to target one eye for distance and the other for near (typically -1.50 D). Figure 2 shows the combined binocular visual acuity for the various degrees of mini-monovision. Click on each graph and then on expand to get the best view and explanation. Google this:
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Optimal amount of anisometropia for pseudophakic monovision.
Ken Hayashi, Motoaki Yoshida, +1 author H. Hayashi
Published in Journal of refractive surgery 1 May 2011
Medicine
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According to this curve visual acuity drops to 20/32 (the normal limit of acceptable vision) at 0.8 meters or about 32" for a distance set monofocal. Results do vary from person to person, and typical near vision results are typically in the 2-3 feet range. Those with myopia prior to surgery may get a little closer vision. Also those with smaller pupils (like older people) get better near vision. I get vision down to 18" with a bright computer display with my distance set eye (-0.6 D SE), but that seems to be unusual. My myopia was in the -2.5 D range before surgery, and I was 71 years old when my first eye was done.
trilemma kdf123
Edited
RonAKA, are you implying that the doctor is more likely to use too strong of lens for the IOL if the patient had been myopic? Why would that be?
Would that be intentional?
RonAKA trilemma
Posted
I looked for the study but could not find it again. However, some time ago I found a study that concluded people that were myopic before surgery tended to have better near vision after surgery, when they were targeted for distance vision. I suspect that is due to differences in the length of the eye of a myopic person - longer eye. I don't know why, but possibly the longer eye stretches the focus point more than a person with a shorter eye. Just guessing. The same study also found that those with smaller pupil size also had better near vision. This probably could be extrapolated to conclude that older people that tend to have smaller pupils can expect better near vision. This effect would appear to be due to the pinhole effect extending the depth of focus, kind of like the IC-8 IOL does.
trilemma RonAKA
Posted
I suspect that is due to differences in the length of the eye of a myopic person - longer eye. I don't know why, but possibly the longer eye stretches the focus point more than a person with a shorter eye. Just guessing.
DOFMaster "On-line Depth of Field Calculator " showed greater depth of field when I plugged in a longer focal length.
Guest kdf123
Edited
The short version is, pretty much everyone that lands right on plano can expect to have usable vision down to 36 inches (3 feet) but your mileage (and where your refraction lands) can vary dramatically from one person to the next. I have Eyhance which is basically a monofocal (only a very tiny intermediate benefit) and in really good light that eye is usable down to 14-16 inches. My Dad has monofocals set for distance and ended up with even better near vision. He can read ingredient labels in normal indoor room lighting. Incredible. So no one can really tell you for sure what you will get. There is so much more to vision than just the implant. BUT… you can probably count on at least 32-36" or so being very usable.
aspen88 Guest
Posted
that is incredible. so your dad can basically see at all distances?