If you’ve been to our office you might have noticed we have a lot of Apple products throughout.  We employ several desktop computers, iPads and iPhones to manage our electronic records, communicate with our awesome patients and even accept credit card payments.  So it should be no surprise that I’ve been eagerly awaiting Apple’s next product announcement.

Today Apple revealed the details of the newest version of their “resolutionary” product: the iPad.  One of the most signifiant improvements compared to its predecessor is the resolution of the display which they now bestow the moniker of “Retina Display”.  As an optometrist who examines retinas all day long, I thought it would be interesting to more clearly define how the iPad is being compared to the resolution of the human eye.

The retina display, first introduced in the iPhone 4 a little over a year ago, is remarkable because the resolution is so high that a human eye cannot see the individual pixels on the screen.  Put another way, the pixels are so close together your eyes cannot see any one individual pixel.  You and I appreciate this as crisper photos and easier to read text.  It truly is a gorgeous screen that can truly reduce eye strain.

Let’s take a quick moment to compare the technical specifications of the retina display to the physiology of the eye.  There are two key variables to consider whether a user will be able to see the individual pixels on a screen or monitor: the user’s visual acuity and the distance the screen is from the eye.  A person with 20/20 (normal) vision has an eye resolution of 286 pixels per inch (ppi) for objects viewed at 12″ away.  Since the iPhone 4 has a resolution of 326 ppi, the eye cannot see any pixels.

The first two versions of the iPad have a resolution of 132 ppi so viewed at 12″ the pixels are still distinguishable to users with 20/20 vision.  Even if you hold it at 16-18″ inches you will still be able to see the pixels.  However, the newest iPad has 264 ppi.  While that’s not enough resolution at 12″, it more than enough when held at a comfortable 16-18″.

Looking past all the mathematics (and I did skip some of the math), the main things to consider is the resolution of the eye always depends on the visual acuity (e.g. 20/20) and the distance an object is viewed.

So go ahead and tell your wife or your parents that you need to buy the new iPad because its easier on the eyes.  It’s even OK to tell them your optometrist recommended it.

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