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eyestrain, not enough hertz can damage your eyes
(by the Hot Deals Maniac, last updated August 8, 2001)

Conventional (CRT) monitors flicker, which can contribute to serious damage to your eyes. Unless you are reading this through a LCD monitor, you should be running at 85Hz or greater or you could get eyestrain, also known as Computer Vision Syndrome. The higher the refresh rate, the more stable the image, and less damage is caused to the eye.

After speaking with a few of my friends, I noticed that hardly anyone updates the refresh rate on their desktop computers. From someone who spends a lot of time looking at a computer monitor, let me tell you how important it is to maximize the refresh rate on your monitor. First off, understand that the images that you see on your CRT monitor are not static images - they are not like looking at a painting on the wall. Your CRT monitor sprays beams of light to one pixel at a time, but does this thousands of times horizontally per second, and a few dozens of times vertically per second. The image seems solid, but is no more solid than a fluorescent light. The rate of vertical refresh is expressed in hertz. Most monitors support a minimum refresh rate of 60Hz, which means the monitor will flash the screen 60 times each second. Although your brain cannot register the strobe-like refresh effect, your eyes can, and this is called eyestrain.

Continued eyestrain over long periods of time can cause serious eye problems. How do you know if your eye is strained? If you stare at a monitor for more than 2 hours at a time, and if your brain starts to hurt (like you have a very minor headache), your eyes are under too much strain and must be given a rest.

How do you minimize eyestrain? The easiest way is to increase the refresh rate on your monitor.

Based on a poll that I did to a select group of people, here's the refresh rates that I discovered and their relation to people feeling "eyestrain": (I mean "casual use" because the test subjects were not staring at their computers for the entire time, but were for most of the time - in a workplace.) Note that this was a personal survey of a few friends, and should not be considered as an official guide to "eyestrain" in any way. Kids, don't try this at home.

Okay, so now you know, but how do you check your refresh rate? In Windows 95/98/ME/2000, right-click on the desktop and choose Properties. Click on the Settings Tab, click the Advanced button. Click the Monitor tab. Check the Refresh Frequency setting. On some Windows OSes, you may be required to first select the exact monitor model of your monitor before the refresh rates show up. If your OS allows an option of "Adapter Default" or "Maximum", I would manually specify the highest refresh rate just to be sure. Under Windows NT 4, right-click on the desktop and choose Properties, click the Settings tab, and the refresh rate should be right there. If anyone knows how to set refresh rates on Linux, Mac, or Solaris, please let me know.

I strongly recommend a refresh rate of at least 85Hz at all times for CRT monitors. Anything less and you may be asking for trouble, especially if you are in an office where you are staring at your computer for most of your day. If your refresh rate is 60Hz, you must increase your refresh rate to something higher. A CRT monitor running at 60Hz is extremely unhealthy if you stare at your computer for more than an hour at a time (est. 2 hours of casual use). Note that as your screen resolution increases, the monitor's max refresh rate will decrease. For example, my Viewsonic PS790 supports 85Hz at 1280x1024, but drops to 72Hz at 1600x1200, so I chose to run it at 1280x1024@85Hz. Lowering your screen resolution will allow for a greater max refresh rate. I would gladly sacrifice desktop space for an 85Hz refresh rate, as should you. If your monitor does not support a good refresh rate at your desired resolution, I would consider purchasing a new CRT monitor or any LCD monitor.

Laptop screens and LCD monitors are much easier on the eyes, because they do not flicker (or have a strobe-like effect) like conventional (CRT) monitors do. Because of this non-flickering technology, your eyes will feel comfortable with viewing an LCD screen at any refresh rate. Also, LCD monitors to not susceptible to background light glare, which can also cause eyestrain. Laptop users should not split their display simultaneously between a laptop LCD screen and a CRT monitor, because the laptop's 60Hz refresh rate will be fine on the eyes, but the CRT signal will share the same 60Hz frequency which can cause serious eye damage.

If you do spend more than a few hours staring at a desktop computer CRT monitor each day, I strongly recommend looking at a refresh rate no less than 85Hz. Period.

If you are considering purchasing a new computer monitor, I would strongly recommend that you consider an LCD monitor if you care about your eyes. LCD monitors are much more expensive that conventional CRT monitors, but are much easier on the eyes. Another thing to consider, a typical 15" LCD monitor has a similar screen size to a 17" CRT monitor, a 17" LCD has a similar screen size to a 19" CRT monitor, and so on. So if you are used to looking at a 19" CRT monitor screen, I would consider upgrading to a 17" LCD monitor - physically a smaller size but will appear to be identical. And, a LCD monitor will be much healthier on your eyes at any refresh rate.

An optometrist had these comments in April of 2001. He said that while increasing the refresh rate of your monitor will help reduce eyestrain, there are many other causes of eyestrain which result from working at a computer workstation.

Some helpful links: Some video cards will drop their refresh rates to 60Hz when playing DirectX or OpenGL games & screensavers. If you have an Nvidia video card, it is recommended that you look for a Nvidia Refresh Rate Fix application that will force your video card to run at specific refresh rates when playing games.

At the time of this article, my desktop consists of two 15" Samsung 150MP LCD flatpanel computer monitors, both running at 1024x768 at 85Hz, using a single Matrox Millennium G550 dual-head video card, total desktop resolution is a massive 2048x768. In a dual-monitor environment, having two CRT monitors will drastically increase the glare and radiation on my desk which can contribute to eyestrain, but two LCD monitors are safe and make my eyes so comfortable I can stare at the screen for long periods of time with no problems.

This article was written based on observations of several test-subjects in a work environment, and through knowledge passed to me by eye doctors. The eye doctors contributed to this article in an effort to help get the word out about how critical eyestrain is as millions of people are now staring at computer screens.