From Greek and meaning roughly ‘well-proportioned, or well-measured sight’, emmetropia is literally a condition where the person can see what ought to be seen. In particular, this is taken to mean ‘seen at distance’. At some point, the brute measure of emmetropia was if a viewer could, on a clear dark night, see two stars in the second point on the ‘handle’ in Ursa Major. Sometimes called the Arab Eye Test, this is an interesting bit of history written in the stars and in the history of vision science. Of course, to the Vision Mechanic, it has limited applications in the clinic – to be sure, it is not an accurate measure of or test for emmetropia.
Photography in the Foothills of Alberta affords many opportunities to appreciate some truly spectacular landscapes and lighting. It helps to be nearly emmetropic – I can see quite well at distance with no effort and no help. In my early 50’s, I have a notable and predictable loss of focusing power at near distances, and so I absolutely love my near-bias progressive addition lenses (PALs) which I use every time I sit down to write or work on a computer. Still, lest I lose my sight to medical blindness, I should mantain my distance sight to my last days.
People with myopia and hyperopia will always need help to see clearly at distance. Same for those with astigmatism. This brief video describes emmetropia in terms of muscle strain, and how this is different for myopes and hyperopes – and hints a little at why hyperopia is one of the most commonly undetected learning disabilities.
The Vision Mechanics know that you have to fix the basic inputs, check the plugs, check the tank, before you start looking at computer code. Vision is everything, when it goes wrong, life follows. Watch the video above to learn more about emmetropia, and what happens when vision is not so perfectly tuned to the distance.
You can learn a lot more about refractive states like astigmatism, hyperopia, and myopia by taking the Intro to Human Vision course and other courses at VisionMechanic.net, so feel free to have a look. You’ll be especially interested in spending time with us if you’re a parent, a teacher, therapist or doctor working with reading, developmental, and learning disorders, or even brain injuries – we’ve got a load of good advice we all should have been taught in school.
We’d appreciate it if you Liked and shared this video series if you find it helpful. We’re planning a lot of new content so subscribe to ensure you see all the new videos as they come out. Go to VisionMechanic.net to let us know if there’s a topic you’d like us to cover in an upcoming episode of the VisionMechanic.
All science, with just a little attitude and no filler. That’s the Vision Mechanic. See you next time.
Dr. B
2 Responses