Why do I feel a strain on my eyes when I look at the 19" matte display?

I have a white MacBook. It has a 13" glossy screen which sports a 1280x800 max resolution. Awesome stuff. Lovely fonts, great display quality. Only, sometimes, 13" isn't spacious enough.

I also have a 19" external LCD from ViewSonic (VX1940w). It has a matte, wide-screen display, and sports a max 1680x1050 resolution. When I have a need to make room for more windows on the screen simultaneously, I connect the LCD to the MacBook via a mini-DVI to VGA adpater. Fonts don't look half as crisp, and the quality isn't quite what I enjoy on the small glossy screen, but at the very least, I get more space to manage my work with some level of comfort.

While the font quality isn't desirable--they appear jagged--I am willing to overlook it. But--and I can't understand why--I feel a lot of strain on my eyes when I look at the LCD. I don't know why. I have tried tweaking all sorts of conceivable settings, both on the LCD and system preferences, from contrast to brightness to colour calibration, but managed to get no-where. I've toyed with the ambient light to no effect--and the fact that I don't so much as twitch in front of the 13" screen would suggest that my ambient settings are not at fault. But no sooner I sit in front of the LCD than I start feeling an incredible strain burdening my eyes down. I should note that the LCD only seems to support a refresh rate of 65Hz. It won't let me switch to another. Could this be a problem? Is there a way for me to work around it, somehow?

It is a shame I can't really use the LCD as much as I'd like to. I am short-sighted, but as I mentioned, I have absolutely no issues with staring non-stop at the 13" screen (I know bad idea, and yes, I make use of AntiRSI with some level of success).

Any pointers, insights would be greatly appreciated. Thanks.

Update: JNK, in their reply, touched upon a point that I failed to address in my question. I am going to make a small update respecting that. Initially, I started with a dual-head setup. It didn't work for me, what with the eye strain and the disproportionate sizes of the two displays. I then settled down with the LCD as my primary and only display. But the incredible eye strain I felt in that setup forced me to go back to using my 13" only.

Solution 1:

It's probably not an issue with the LCD, but with the constant adjustment your eyes are making between them. I am assuming that you are using both the LCD and the 13" screen. The constant back and forth between the 13" that your eyes are used to, and the 19" which is quite different may be the cause.

As to the refresh rate, those are normally set by the hardware in the monitor. You can maybe increase it but you will probably get flickering and artifacts that will just make the problem worse.

Do you ever use any other displays (like a shared terminal at school or a library, or at work?), and if so do you have the same issue there?

If you use both the LCD and the 13", try JUST using the LCD for a short time and see if your eyes can adjust.

Solution 2:

Your monitor has a DVI interface, use that instead. Get a mini-DVI to DVI adapter.

The difference between DVI and VGA is substantial. Over VGA the signal is converted from digital to analogue, then back to digital on the screen. This causes all kinds of problems, colour fringing, "pixel creep" and a general lack of sharpness. It also can't make use of subpixel font smoothing. If your screen has an "auto" button, that's there to try and make a decent picture from the VGA input.

Over DVI, the signal is digital all the way.

I switch workplaces a lot and use monitors where there happens to be a free seat, and having a DVI connected monitor is more important to me than a separate mouse and keyboard.