>What are your thoughts on causes/treatment of astigmatism? Could lens distortion (away from optical center of a high minus lens) be a contributing factor over

>What are your thoughts on causes/treatment of astigmatism? Could lens distortion (away from optical center of a high minus lens) be a contributing factor over a long period of time? If so, could be an argument for using FF lenses. Apparently the Zeiss FF patent expired this month and Seiko's FF patent expired in 2016. Pfuuuh. Got a link? I honestly have to say I draw a blank in regards to what you mean by "FF lenses", as I'd assume you wouldn't mean full frame lenses in the photography sense? >Rodenstock lenses are not widely available in the US. I know. They recently made an attempt to relaunch in the US but I have no idea if it succeeded. >Looks like the Zeiss Individual SV will compensate for astigmatism caused by pantoscopic tilt, https://pdfs.semanticscholar.org/3e73/2da37ec9e17bd086b32095.. https://pdfs.semanticscholar.org/3e73/2da37ec9e17bd086b32095.... Yepp, but that's not the main problem. The main problem comes from the cyclotorsion the eyes exhibit during convergence as part of the donward gaze. This fundamentally changes the astigmatism axis. I didn't go into this in my earlier post (Which I'll link here, since it's in a different sub-thread: https://news.ycombinator.com/item?id=16195742 https://news.ycombinator.com/item?id=16195742), but actually, to expand on this, I consider cyclotorsion a HUGE problem in the successful measurement of astigmatism. I've tested this empirically quite a few times, and the traditional cover test fails to fully interrupt the fusional circuit in the brain, the cyclotorsion component remains active until the other eye is closed consciously. (In fact, I speculate that even then it remains partially active, and in some cases only a temporary concious supression of the [inside-of-your-eyelids] image leads to a full disengagement of the circuit. But this is highly speculative, take this part with a large grain of salt.) I consider this a problem because: 1. Cycloplegia in fact fails to prevent cyclotorsional adjustment. 2. Incorrect astigmatism correction can lead to amblyopic suppression, which can lead to (micro)strabismus, which leads to diplopia. Now, horizontal prisms aside, which we shouldN't prescribe, ever, except in EXTREMELY rare cases of total muscle paralysis or similar, this can then lead to an incorrect measurement of vertical deviation of the angle of gaze, which leads to an incorrect prism prescription, which... well, you get the point. Bonus if the astigmatism correction ends up so off, you end up affecting distance vision and cause accommodation. Double bonus if the patient already suffered from accommodative cramps [which btw. WON'T GET ANY BETTER if we keep the testing distance at 6 meters, which as, previously state, definitely DOESN'T equal optical infinity.]. Triple bonus if they didn't get cycloplegia to compensate for it at first. Quadruple bonus if the pupil dilation from the cycloplegia fucks up the astigmatism measurement [which is the point where wavefront measurements shine, because they can backinfere about the behavior of the narrower pupil even from the measurement of the widened pupil! But even wavefront measurement can't compensate for cyclotorsion! But of course that gets fucked up by wavefront mesurements that fail to consider the full pupil diameter!] >Some quotes from Chapter 1 of an open-access book on astigmatism: https://www.intechopen.com/books/astigmatism-optics-physiolo.. https://www.intechopen.com/books/astigmatism-optics-physiolo.... >continuous use of the medial rectus muscle, especially during near tasks, imposes a force on the cornea which increases its radius of curvature in the horizontal meridian resulting in a shift towards against-the-rule astigmatism... Interesting. Didn't know that one yet. > Larger pupil sizes—in low lighting conditions— increase the amount of higher order aberrations such as coma and may intensify the cylinder power in subjective/manifest refraction. Coma has been shown to be correlated with greater amounts of astigmatism Yepp, see my point about wavefront measurements. >accommodative astigmatism is related to lens distortion due to inhomogeneous lens elasticity, variable constriction in ciliary muscles (which itself changes the lens power), and nonhomogeneous tension of the extraocular muscles during convergence (which causes corneal distortion… True, but this ignores the cyclotorsional element. >slight changes in cylinder power and axis (towards with the rule) occur during convergence alone … this change is seen in a small percentage of eyes Small percentage my ass, that's a case of underdiagnosis due to insufficiently precise measuring equipment. >for those who experience such an alteration, separate spectacle prescriptions for near and far distance vision might be beneficial. or we can just, I don't know, PROGRESSIVELY ALTER THE ASTIGMATISM CORRECTION AS PART OF GLASSES? Using the same technology we already use for progressives? I know, I know, that'd seem TOO LOGICAL. Sorry, I harbor the most bitter feelings on this topic.