When and if you install it, you might consider this kludge, which has helped me:

https://github.com/schreiberstein/lucidagrandeyosemite

Regards, Nate

Unless and until Apple fixes Yosemite's vision problems on non-Retina Macs, this apparently safe kludge has helped me considerably:

https://github.com/schreiberstein/lucidagrandeyosemite

along with electing every enlargement option I could find scattered all over various application preferences, system preferences, etc. often with non-intuitive labels or names. Very frustrating!

Regards, Nate

In addition, if you switch to FireFox instead of Safari, you can change the font and size of the Bookmarks Toolbar etc. to overcome the visibility problems created by Yosemite on non-Retina Macs. See:

Go the the Add-Ons page on FireFox and search for this Add-On:

Theme Font & Size Changer

Nate

One quick though less attractive-looking fix is to lower the resolution - one side-effect of which is to make everything bigger, if less crisp. Go to System Preferences, Display, tick "scaled" option under Resolution, and choose a lower resolution that suits your size needs.

FWIW, I found it much easier to adjust the default font size in Chrome. Put another way, I have yet to discover a way to do so in Safari running Yosemite.

With Theme Font & Size Changer, I now have four different zoom options showing under the View menu in FireFox:

Full Zoom In

Full Zoom Out

Text Zoom In

Text Zoom Out

Using these options being assigned individually and sticking to each individual website I visit, I was now able to go to System Preferences/Display and return the resolution setting to "Best for Built-in Display" thus getting BOTH the best resolution and the needed font enlargement and choice of fonts at the same time.

I have found no way to do this in Safari.

Has Apple lost its perspective?

I have been using a 15" MBP Retina laptop for a couple of years, mostly for Web use and photo processing with Apple's Aperture.  Most Web browsers work fairly well, and the MBP Retina is an eyesight saver.  I wish I could say the same when using their photo app Aperture.  At the display's default resolution, the side panes in Aperture have a fixed minuscule font.  I keep the display 16" away for my eyes and I am forced to use the annoying "Control + 2 fingers swipe" gesture to Zoom in and out while working with Aperture.

I was planning, and actually looking forward, to buy the new high powered 27" 5k iMac.  With such a big display, I thought for sure the minuscule font would be relatively scaled up to the 27" screen size.  A visit to the Apple Store to check out that 27" display proved me wrong!  That font in Aperture remaind exactly the same size as on the 15" display.  Ditto for the iTunes Store app; same minuscule font but twice as many albums with minuscule titles displayed in a HUGE window on a huge display right in your face.  Talk about perspective!

Interesting to note that competitors may have done better in this area.  With Windows 7, Microsoft included in the Display Resolution settings a choice for all objects including text to appear "small", "medium" or "large" at the display's native resolution.  Adobe included a scalable font size setting in their Lightroom photo app; this setting works OK on the Windows version of Lightroom, but for some reason does not function on my MBP running Yosemite.

Hard to believe that with all this advanced technology and super high resolution displays, perspective may be now be a thing of the past .  I called Apple support a few times and for some reason they always include in their follow-up Email a link to their "Options for Accessibility" page.

If we chose to remain loyal to Apple this may be our only remaining option.

http://http://support.apple.com/kb/ph18395?viewlocale=en_US

Is there an error in your url listed at the end of your comment?

I get a strange looking page with no text on it and/or "server not found."

Nate

Yep!  Link got messed up.  It's the old Apple's

OS X Yosemite: Set options for accessibility

at http://support.apple.com/kb/ph18395?viewlocale=en_US

I'm also using No-Squint and now I am not sure which add-on created these new menu choices, so I can only suggest installing both to be sure!

Nate

I agree. Font rendering also annoying, it is thinner. Everything is getting thinner these days, but fonts need to be fat to have more readability. I installed old Lucida but still applications has thinner fonts, it is not about the menu bar or dock, it is all about the choice of fonts, or rendering, looks like fonts are thinner now.

Actually it is also an issue for retinas. I test drived iMac retina, and I had to use lower resolution than "best-for-retina" option. Since fonts are thinner, harder to read. Each font/character has less pixel density now, this is a less of a problem for retina but still a problem. I have more eye strain compared to my retina macbook pro that has Mavericks on it.

Actually I believe this is a very serious issue that Apple has to consider. I changed to Mac 2 years ago solely because of Retina display. I am a researcher and in front of the computer reading/writing at least for an 8 hours/day. According to my doctor my eye has not got worse, but slightly better since 2 years ago. I cannot say this is due to retina but at least it does not get worse. I did not upgraded my macbook pros like you guys to new OSX,  but I am seriously thinking of iMac retina. But after I test drived I see that  Yosemite is definitely worse with respect to font rendering. Again people got stuck with respect to Helvetica vs Lucida, it is not only that, I think they made everything "thinner", which makes reading harder on our eyes.Anybody knows how to change the font to make fatter like Mavericks? I changed to already Lucida but that only helps the menu. The real issue is rendering or making fonts thinner, paler, in my opinion.

As others on this thread may have noted, Yosemite's changes affect not only the vision-impaired  but all "older eyes." I doubt I'm the only Mac user whose eyes had been "just good enough" to see without glasses about 30" away from an iMac by virtue of globally enlarged type face. (Why I've also largely switched to reading books on an iPad). Certainly I don't begrudge Apple its right to use whatever type size/font style it prefers to market its products. I do mind when the company takes away our ability to make adjustments, or inflicts pain (in the form of inferior display) as the price for allowing it.

Apple is losing sales over this smaller font issue.

With the advent of new cameras with higher resolution, more photographers (professional and hobbyist) are now thinking twice before upgrading to the new processing power of the 27" iMac 5K or any Mac running Yosemite for that purpose.  I know I am.  I would gain the higher resolution for the image itself but also the eyestrain trying to read those tiny fonts in the image processing software, regardless how big the display size, whether it's a 15", 21" or 27".