Since you guys like to go back and forth on and throw optical theories about then I thought I would let you in on a raging debate me a couple of OD's an MD and Retinal Specialist have been bashing about for the last few years..
It's prism :-) It all started over Fresnel press on prism and has grown from there..
namely the idea that an elderly guy was prescribed 30^ base out (yikes) well here is my point of view.. the corneal apex forms the anterior pole. opposite is the posterior pole on the temperal postion to the optic nerve..now the optic axis joins the 2 poles. (so far easy right?) ..NOW the fovea centralis set temporally and below the posterior pole..so the visual AXIS and the optic AXIS are NOT coincident!! ..OK so far, right? ..think of a "X" ..stretched, the visual axis at one point, the optic axis at the other side then they cross at the "equator" (well close to it) then spread out again at the fovea centralis..now here is where we get into the "crux" of the hmm "debate" .. My point is that you have to break down the fovea centralis (rod & cones) ..the RODS are very sensitive to light, they are responsible for low light conditions (night vision etc.) the rods do NOT "see" the color spectrum per se so they produce "colorless vision" ..now CONES do break it down (blue, green, red) ..though low light source is not enough to get you to "see" color in low light conditions with the cones... NOW to get to the "meat" of it.. Cones & rods both connect with the bipolar cells. The cone fiber is dominate while the rods fibers are devided...
Now we breakdown the fovea.. it's about 16 to 1 (rods to cones) I'm going from memory but it's like 110 million to 6 million (something real close to that.. but the crux is where they are located and the concentration..the rods are located centrally and drop off rather quickly, there are NO rods at a small area in the central fovea zone.. while the rods are at maximum around 5 mm away from the fovea..
SO .. I think you can hit it with prism (the rods) more so the the cones..BUT there is a limit to the amount of diviation of "light" and still get a actual image that can be of any use.. The way I see it you can "bend" more through prism but you would be flashing across the rods and cones and only the perception of "brighter" light would be acheived but NOT any usuable images.. while less prism would give you not as great "acuity" but give you an actual image that you can "see" .. amybe "blurry" but it sure beats just "brighter light" in my opinion...
The second part of my theory is that the time difference of reproduction of the rods and cones.. rods can do it far qiucker then cones.. so I've been batting around the idea that if you actually stimulate the rods and cones with prism (even in the case of MD if diagnossed soon enough) then you can give it a slight "push" and stimulate regrowth and "trick" the eye to thinking (I know it has no brain but give me some slack) that even though centrally you have loss you bend light across the fovea at an angle to hit the rods and cones...and then gradually cut back the amount of prism to get images over a time period..
well anyone want to add to the debate? .. any idea's? ... am I off my nut? (optical nut :rolleyes :) Well you guys seem to have opinions.. how about it..

Jeff "just, still, a lab rat.. but a curous one" Trail