Vision screening
Why vision screen?
Resources
Vision2020
Protocols
Some international standards, lots of local variation.
When children can run tests independently, time is less important than in clinical setting. So time can be traded for more accurate results, and a more enjoyable process.
Resources
Protocols - OLPC-specific opportunities
Screening protocols are built around expected equipment and logistics. We obviously have a nifty additional resource, olpc laptops. OLPC dramatically changes the equipment which can be relied upon to be available. This could both aid in applying existing tests, and create screening opportunities which would otherwise not exist. So in addition to attempting to help with current protocols, we should look for additional useful ways olpc might be used.
A variety of tests seem possible. Some straightforward (such as broken-line vernier acuity), some likely (such as color perception), some may or may not be feasible (astigmatism), some would require additional equipment (a small mirror and cardboard box for binocular perception), and some are more speculative. It may be possible to do some kind of alignment and motility tests, but I'm not sure. Among other things, the laptops have a low-resolution "webcam" camera, which could take 600 pixel wide pictures of each eye. And there is a prototype ~1 dollar lens set to make it into microscope, so close-ups seem possible. The laptops also video conference.
Candidates and discussion
field of view testing
Is this actually useful for target population?
other
- use added macro lens for photographic examination?
Optotypes
Display and illuminance
Visual acuity
Visual acuity charts screen for near sightedness, far sightedness, astigmatism, and anisometropia (visual acuity differences between the two eyes).
Stereo acuity
Random Dot E (RDE), Stereobutterfly stereopsis
Stereo-acuity is a good instrument for the measurement of fusion. But traditionally expensive and hard to conduct. If a child has poor stereo-acuity caused by strabismus, that deviation should be detected with properly performed cross cover testing. So it's normally secondary to corneal light reflex/cover testing.
Color vision
Near vision
Near vision is said to be more difficult to test with children as the accomodate more easily.
Contrast sensitivity
There is a color object sorting game from Game Jam Boston June 2007 which might be leveraged.
Muscle balance testing
The early childhood years and the early elementary years are critical touch points to screen for amblyogenic risk factors, such as strabismus.
It is important to screen for muscle balance deficiencies and organic factors, especially in children younger than 8 years of age. These include the corneal light reflection and the cross cover test (by using a toy for the child to look at straight on and an occluder).