When can an exam lane be without mirrors?

[planex]

I remember being in one exam lane without mirrors, and it was a very long room, and it was years ago.
Since then, there has always been a two mirror system in every exam lane that I have seen. Does anyone know the minimum room length to allow for no mirrors for refraction?
If I am figuring right, it would only seem to need minimally about 13 ft (allowing room for the exam chair) to enable 10ft from the projector to the screen and 10ft from the phoroptor to the screen and little extra. I would appreciate affirmation if I am thinking of this correctly or another explanation.
- thanks so much

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[POJO]

At 16 feet from patient to screen, it should be 16 feet or 5meters +. This equates to an accommodative demand about .16D.

 

[orangezero]

I remember being in one exam lane without mirrors, and it was a very long room, and it was years ago.
Since then, there has always been a two mirror system in every exam lane that I have seen. Does anyone know the minimum room length to allow for no mirrors for refraction?
If I am figuring right, it would only seem to need minimally about 13 ft (allowing room for the exam chair) to enable 10ft from the projector to the screen and 10ft from the phoroptor to the screen and little extra. I would appreciate affirmation if I am thinking of this correctly or another explanation.
- thanks so much

The distance from the projector to the screen would make no difference in the patient's accommodation, other than needing it close to you to change it potentially. Ideally, the room would be set up to allow 20ft from eye to letter. I've heard 12x9ft mentioned as a good size room. The 20ft rooms are becoming outdated. I think its mostly due to size constraints and more efficient use of space. Although, I have seen a few rooms where the extra space was put to good use storing contact trials, etc.

I know there are standards and we can make corrections, but I personally wouldn't want to have everyone off by 0.16D, if I could avoid it by better planning. Then there is always the factor of proximal accommodation to have to worry about. Patient staring at a wall 8ft away (even while looking in a mirror) is going to feel boxed in and the visual system isn't exactly the same then like when they are in their house, or in the car.

 

[POJO]

If something is off theroetically by the same consistent amount, I don't think there should be a problem. Likewise, if you have >70 y/o patients, the 0.16D should be controllable, if not trivial.