Online viewfinder: The web simulates a world skewed by a host of ocular conditions

The world can look much different through glaucomatous eyes. But for those of us who are not lucky enough to have 20/20 vision, there is a way to experience perfection. Determine, too, the influence of a variety of neurological disorders on visual perception. It’s all online.

BEFORE looking at the effects of disease on the human eye it might be worth taking a detour to see how our vision develops. So, what does a tiny baby see? Tiny Eyes (tinyeyes.com/tinyeyes) attempts to show the development of the human visual system from birth onwards. The site is fun and easy to use. You simply select an image file on your own hard drive, select an age from newborn to adult, enter the viewing distance and click.

It can be difficult to describe the effects of progressive vision loss in words alone. A new web site sponsored by Pharmacia (my-vision-simulator.com) does a nice job of simulating the effects of various eye conditions on vision. Using the Vision Simulator is easy. You can change perspective from early progression to a more advanced stage simply by clicking and dragging your mouse on a graphical slider bar under various images. You can also change the focal length.

The site provides simulations of the common refractive problems such as myopia, astigmatism and hyperopia. It also does an impressive job of simulating the different stages of the most common eye diseases, including glaucoma, macular degeneration and cataracts.

In addition, you can see the effects of both proliferative and non-proliferative diabetic retinopathy, as well as the effects of day and night versions of retinitis pigmentosa.
This useful patient-oriented site also provides summary information on the different diseases, along with links to more comprehensive materials.
One in 100 males in the general population have some kind of colour blindness. This might help explain the presence of very useful evaluation tools that can be found on the web.

One site in particular, VisCheck (www.vischeck.com), does a remarkable job of simulating the world through the eyes of patients with different types of colour blindness - deuteranopia, protanopia and the more rare tritanopia.

VisCheck was developed by researchers at Stanford University, California, US. It allows the user to choose an image from his or her own hard drive online simulation of colour vision disorders. You can also see how different web pages you specify look under these conditions. VisCheck also offers the option of running the tool offline via downloadable software.

Those with some degree of colour blindness can adapt to everyday life. VisCheck provides another interactive tool that uses image processing techniques to shift colours in different images to make them more viewable for the colour blind. The developers believe this approach could have numerous applications for helping colour-blind people function when using various display devices including microscopes, TV and computers.
Another excellent site demonstrating the worldview of colour-blind people is Web Exhibits (webexhibits.org/causesofcolor/ 2.html). This site includes a nice simulator, along with a lot of sophisticated information types of disease, genetics and testing methods.

Patients considering refractive surgery would love to be able to see what their new vision would be like in advance. Attempts to describe the visual changes provided by Lasik range from the very basic but fuzzy ‘before’ and clear ‘after’ photos to very sophisticated wavefront tools.

As detailed in the last month’s column, there are also quite a few sites providing some idea of what a poor outcome from Lasik might look like (www.escrs.org/eurotimes).
Researchers at UC Berkeley are using some of the same tools used make to animated features movies like ‘Toy Story’ to provide software tools to, among others things, simulate the effect of various aberrations and their correction on human vision. (www.inst.eecs.berkeley.edu/ ~cs39j/vrr/ images.html)

They have developed a prototype based on what they call vision-realistic rendering, which generates images based on the wavefront characteristics of a particular individual’s optical system.

Applications in ophthalmology include simulating the actual vision of a patient, simulating visual disorders for the education of doctors and patients and simulating vision before and after surgery using preoperative and postoperative wavefront data. You can see samples of the system in action at the web site.

Researchers at Emory University have gone one step farther. They have developed the Interwave visualiser, a system for simulating the effects of different aberrations in the clinical setting (www.emoryvision.com/visualizer.html).

The system is now being used to provide patients with some idea of what their vision could be like following different refractive procedures. The system allows surgeons and patients to view images as they would appear without correction, with spectacle correction, and after Lasik under daylight, dusk and nighttime lighting conditions.
The images can be viewed on an LCD screen or a “virtual reality” visor. These images are generated from information gathered during wavefront scanning.

The Interwave system resembles a video game. The patient uses a joystick to centre a small light spot on a grid, clicking a button when alignment is complete. The computer records a precise measurement of the focusing power at each point tested. The system can record up to 70 measurements across the pupil for each eye.

The developers say the tool is specifically designed to optimise Lasik outcomes, producing sharper vision in all lighting conditions and fewer halos. Future applications of the Interwave system include planning re-treatments and treatment of presbyopia.
Neurological disorders can also have dramatic effects on vision. Researchers at UC Davis have created an excellent interactive tool that demonstrates the effects of disabling one or more of the 12 eye muscles and one or more of the six cranial nerves that control eye motion(cim.ucdavis.edu/EyeRelease/Interface/TopFrame.htm).

The purpose of this simulator is to teach medical students and doctors how the eye motion will change with the pathology of the eye muscles and cranial nerves and what to look for during a standard neurological eye examination. The latest version also includes a pupil response simulator.

The sites mentioned here are good examples of the educational power of the web. The disease simulation sites might be very useful for counselling patients and their families about what to expect from various visual disorders.

They could also have an important role in training the next generation of physicians. The wavefront-based simulation systems offer the added promise of not only giving patients a preview, but also of improving overall results with refractive surgery in the longer term.

Comments or suggestions for this column? Drop me a line at primesite@press1.com

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