piano music question

[septembergal]

After cataract surgery, with a lens implanted and set for distance vision, will I be able to see music about 24-25 inches away on the music stand of a piano without glasses?  
thanks

[SoftwareDeveloper]

When you need to focus at a certain distance, the lens power compared to what is required to focus at distance is measured in diopters. This page gives examples of what distance compares to what diopter measurement:
https://www.slackbooks.com/excerpts/67956_3.pdf

the formula is (100 / distance-in-centimeters).  So 24-25 inches would be 60.96-63.5 centimeters which is 1.57-1.64 diopters. So if your eyes were focused exactly at distance, reading glasses of +1.5D would be about right to focus at that distance exactly.

A monofocal lens does let you see well within a small range of  distances, so if you were doing monovision, one eye being set for distance and one eye being set for near, you could set one eye at -1D, 1 diopter myopic, or perhaps 1.25D myopic, and that  would likely let you see that sheet music well enough, with -1.5D being better but risking more trouble adapting to the monovision and reduction of  stereopsis, 3D visual perception.

That distance is generally considered in the "intermediate" range (though different studies use different definitions of "intermediate", 60cm or 66 cm  are  fairly common).

Alternatively rather than monovision you could consider a premium presbyopia correcting lens that gives good distance vision as well as more closer in vision than a monofocal. The options are  a multifocal lens, the accommodating Crystalens, or if you are outside the US then the extended depth of focus lens the Symfony which isn't yet FDA approved (this is an international site, it doesn't say where you are from, though most are from the US).  The Symfony is likely the best bet for good intermediate, follow by the Crystalens (though there are some potential side effects and the risk that the Crystalens won't accommodate that make it less of a good bet for near).

In the US, unfortunately the "multifocals" are really bifocals and were  initially setup to give good distance and near vision, with not quite as good intermediate vision. Outside the US there are trifocal lenses that give better  intermediate vision in addition to good distance and near (though their intermediate may not be quite as good as the Symfony or Crystalens, they may give better near).

Just in the last few months they've approved some low add bifocals in the US  like the Tecnis +2.75 and +3.25 and the Alcon Restor +2.5 which are focused on distance and intermediate, with not quite as good near. (outside the US the Lentis has even lower adds, the +2 and the +1.5).  They are somewhat comparable to the Symfony or the Crystalens (if it accommodates, it does for most but not all) in terms of their visual range, but likely not quite as good still for the distance you want. That is around my computer distance, which is why I went for the Symfony. A recent study on the Symfony:

https://ascrs.confex.com/ascrs/15am/webprogram/Paper16105.html
"New Extended Focus IOL Versus  Bifocal, Trifocal, and Accommodating IOLs

Results
Extended focus lens achieves the best results from 46 cms to farthest vision with no disphotopsic phenomenon and with a great subjective satisfaction."

That 46cms is 18.11 inches, and that is only the range where it is better than other lenses, its still decent a bit further in for many people.  

Various studies give what is called a "defocus curve" for a lens, showing how good your visual acuity is at different distances if you set that lens to far. Usually they measure the distance in diopters, but sometimes they add centimeters as well. The visual acuity is often in "logMar" or decimal which can be converted to the usual  20/20 or 6/6 (metric) measurements from charts like on this page:

http://en.wikipedia.org/wiki/Visual_acuity

It is hard to know what say 20/30 means, but one guideline is that 20/40 in most places is what you need to drive. This page gives a chart of  visual acuity you need to read different types of print at  near:

http://www.teachingvisuallyimpaired.com/print-comparisons.html

For instance you only need 20/50 to read small column newsprint.

This gives a defocus curve for the Tecnis monofocal and the Symfony lens, if you click on the clinical tab:

http://www.tecnisiol.com/eu/tecnis-symfony-iol.htm

This gives one for the Tecnis +2.75 and +3.25 and +4

http://amo-inc.com/products/cataract/refractive-iols/tecnis-multifocal-family

The Restor +2.5 and +3:

http://www.alconsurgical.co.za/acrysof-iq-restor-2-5-d-iol.aspx

There are reasons some surgeons  prefer the Tecnis lenses over the Restor lenses due to things like correcting chromatic abberation, and fewer glistenings, but they are widely used.

This gives a defocus curve for the Crystalens AO:

http://ascrs2014.abstractsnet.com/handouts/pdfs/100183.pdf

[achillea]

Before my cataract surgery, I had three (!) separate visits with my surgeon to ask questions, which he patiently answered.  On one visit, I told him I'd  sure like to know what to expect, and he held lenses up to my eye to simulate--not exactly predict--but to give me some idea of what I might see with x, y, or z.

You might want to ask your doc about something like this.

[Anomalychick]

It depends. Some people can some people cannot. You should at minimum be able to make it out, but it will be blurry. It really depends on the person. Some people can see just fine at arms length, but with others the blur begins at around six feet away.

I cannot guarantee you will be able to.