I did a series of two blog postings several weeks ago on accommodating people with limited vision. It was motivated by the fact that I have had cornea transplants and cataract surgery, and have spent many years with limited vision.
One of my motivations for looking at vision problems has to do with developing technology that can be used to aid people with limited vision make full use of the Web.
This time, I’d like to look at an issue that is specific to people with vision problems that cause angular distortion, as opposed to vision that is very unfocused or opaque. This was my problem. Before I had cornea transplants, my vision was perfectly clear and somewhat unfocused; the dominant symptom was that the world around me was fragmented into overlapping, broken images. People who have had laser surgery to fixed their nearsightedness, but where too much of the cornea was shaved off, can have similar symptoms.
Why are the corneas so critical to vision? The corneas, which are the clear outer surface of the eye, prefocus light for the lens. If the corneas don’t do their job right, the lenses cannot do their job.
It’s called Keratoconus.
My corneas thinned as I aged, until they were so thin they lost their structural integrity. If you look directly into the eyes of a person, you could consider the top-to-bottom axis to be “u” and the side-to-side axis to be “v”. The front-to-back axis could be consider “w”. Imagine examining someone’s corneas, in particular, looking up and down the u axis, and right and left across the v axis. If that person has normal corneas, the corneas have a smooth, spherical slope into the w axis. My disease caused the slope of my corneas to vary significantly at various points across both the u and v axis. This caused light going through my corneas to be refracted at widely different angles. This created a sort of kaleidoscope effect.
The challenge for someone with kaleidoscope vision is to extract an accurate mental image based on your shattered view of the world. This disease, by the way, is called Keratoconus, which is basically Latin for “cone-shaped corneas”. The name comes from one of the primary symptoms used to make a diagnosis: super-thin corneas tend to get pushed outward by the center of the eyeball, turning the cornea from a basketball to a football (or cone) shape.
The parallel between Keratoconus and 3D model deformation.
I teach an introduction to 3D animation class, and years ago, I noticed that some of the “deformer” effects available in Autodesk Maya, (the gold standard in 3D animation) could be used to simulate the distortions caused by my eye disease. As part of my research at my university, I’ve been experimenting with using deformation effects available in Maya to compensate for the distortion caused by Keratoconus.
A couple of examples.
Below are two sets of images. The two with red characters on a white background contain the integer 7, showing a common effect of keratoconus: multiple, overlapping images. The two with yellow characters on black backgrounds are the word “cow”, showing another common sort of distortion; in particular, one shows a horizontal distortion, and the other, a vertical distortion.
Note: You may have to click on the icons below to download the actual images.
In the next posting of this blog, I will describe some of the deformation effects in Maya, and how they can be used to actually compensate for the problem caused by Keratoconus.